1 /*
   2  * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #if !defined(__clang_major__) && defined(__GNUC__)
  26 // FIXME, formats have issues.  Disable this macro definition, compile, and study warnings for more information.
  27 #define ATTRIBUTE_PRINTF(x,y)
  28 #endif
  29 
  30 #include "precompiled.hpp"
  31 #include "classfile/stringTable.hpp"
  32 #include "code/codeCache.hpp"
  33 #include "code/icBuffer.hpp"
  34 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  35 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  36 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  37 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  38 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  39 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  40 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  41 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  42 #include "gc_implementation/g1/g1EvacFailure.hpp"
  43 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  44 #include "gc_implementation/g1/g1Log.hpp"
  45 #include "gc_implementation/g1/g1MarkSweep.hpp"
  46 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  47 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  48 #include "gc_implementation/g1/g1StringDedup.hpp"
  49 #include "gc_implementation/g1/g1YCTypes.hpp"
  50 #include "gc_implementation/g1/heapRegion.inline.hpp"
  51 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  52 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  53 #include "gc_implementation/g1/vm_operations_g1.hpp"
  54 #include "gc_implementation/shared/gcHeapSummary.hpp"
  55 #include "gc_implementation/shared/gcTimer.hpp"
  56 #include "gc_implementation/shared/gcTrace.hpp"
  57 #include "gc_implementation/shared/gcTraceTime.hpp"
  58 #include "gc_implementation/shared/isGCActiveMark.hpp"
  59 #include "memory/gcLocker.inline.hpp"
  60 #include "memory/generationSpec.hpp"
  61 #include "memory/iterator.hpp"
  62 #include "memory/referenceProcessor.hpp"
  63 #include "oops/oop.inline.hpp"
  64 #include "oops/oop.pcgc.inline.hpp"
  65 #include "runtime/orderAccess.inline.hpp"
  66 #include "runtime/vmThread.hpp"
  67 #include "utilities/globalDefinitions.hpp"
  68 #include "utilities/ticks.hpp"
  69 
  70 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  71 
  72 // turn it on so that the contents of the young list (scan-only /
  73 // to-be-collected) are printed at "strategic" points before / during
  74 // / after the collection --- this is useful for debugging
  75 #define YOUNG_LIST_VERBOSE 0
  76 // CURRENT STATUS
  77 // This file is under construction.  Search for "FIXME".
  78 
  79 // INVARIANTS/NOTES
  80 //
  81 // All allocation activity covered by the G1CollectedHeap interface is
  82 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  83 // and allocate_new_tlab, which are the "entry" points to the
  84 // allocation code from the rest of the JVM.  (Note that this does not
  85 // apply to TLAB allocation, which is not part of this interface: it
  86 // is done by clients of this interface.)
  87 
  88 // Notes on implementation of parallelism in different tasks.
  89 //
  90 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
  91 // The number of GC workers is passed to heap_region_par_iterate_chunked().
  92 // It does use run_task() which sets _n_workers in the task.
  93 // G1ParTask executes g1_process_strong_roots() ->
  94 // SharedHeap::process_strong_roots() which calls eventually to
  95 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
  96 // SequentialSubTasksDone.  SharedHeap::process_strong_roots() also
  97 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
  98 //
  99 
 100 // Local to this file.
 101 
 102 class RefineCardTableEntryClosure: public CardTableEntryClosure {
 103   bool _concurrent;
 104 public:
 105   RefineCardTableEntryClosure() : _concurrent(true) { }
 106 
 107   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 108     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
 109     // This path is executed by the concurrent refine or mutator threads,
 110     // concurrently, and so we do not care if card_ptr contains references
 111     // that point into the collection set.
 112     assert(!oops_into_cset, "should be");
 113 
 114     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 115       // Caller will actually yield.
 116       return false;
 117     }
 118     // Otherwise, we finished successfully; return true.
 119     return true;
 120   }
 121 
 122   void set_concurrent(bool b) { _concurrent = b; }
 123 };
 124 
 125 
 126 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 127   size_t _num_processed;
 128   CardTableModRefBS* _ctbs;
 129   int _histo[256];
 130 
 131  public:
 132   ClearLoggedCardTableEntryClosure() :
 133     _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
 134   {
 135     for (int i = 0; i < 256; i++) _histo[i] = 0;
 136   }
 137 
 138   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 139     unsigned char* ujb = (unsigned char*)card_ptr;
 140     int ind = (int)(*ujb);
 141     _histo[ind]++;
 142 
 143     *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
 144     _num_processed++;
 145 
 146     return true;
 147   }
 148 
 149   size_t num_processed() { return _num_processed; }
 150 
 151   void print_histo() {
 152     gclog_or_tty->print_cr("Card table value histogram:");
 153     for (int i = 0; i < 256; i++) {
 154       if (_histo[i] != 0) {
 155         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 156       }
 157     }
 158   }
 159 };
 160 
 161 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 162  private:
 163   size_t _num_processed;
 164 
 165  public:
 166   RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
 167 
 168   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 169     *card_ptr = CardTableModRefBS::dirty_card_val();
 170     _num_processed++;
 171     return true;
 172   }
 173 
 174   size_t num_processed() const { return _num_processed; }
 175 };
 176 
 177 YoungList::YoungList(G1CollectedHeap* g1h) :
 178     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 179     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 180   guarantee(check_list_empty(false), "just making sure...");
 181 }
 182 
 183 void YoungList::push_region(HeapRegion *hr) {
 184   assert(!hr->is_young(), "should not already be young");
 185   assert(hr->get_next_young_region() == NULL, "cause it should!");
 186 
 187   hr->set_next_young_region(_head);
 188   _head = hr;
 189 
 190   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 191   ++_length;
 192 }
 193 
 194 void YoungList::add_survivor_region(HeapRegion* hr) {
 195   assert(hr->is_survivor(), "should be flagged as survivor region");
 196   assert(hr->get_next_young_region() == NULL, "cause it should!");
 197 
 198   hr->set_next_young_region(_survivor_head);
 199   if (_survivor_head == NULL) {
 200     _survivor_tail = hr;
 201   }
 202   _survivor_head = hr;
 203   ++_survivor_length;
 204 }
 205 
 206 void YoungList::empty_list(HeapRegion* list) {
 207   while (list != NULL) {
 208     HeapRegion* next = list->get_next_young_region();
 209     list->set_next_young_region(NULL);
 210     list->uninstall_surv_rate_group();
 211     list->set_not_young();
 212     list = next;
 213   }
 214 }
 215 
 216 void YoungList::empty_list() {
 217   assert(check_list_well_formed(), "young list should be well formed");
 218 
 219   empty_list(_head);
 220   _head = NULL;
 221   _length = 0;
 222 
 223   empty_list(_survivor_head);
 224   _survivor_head = NULL;
 225   _survivor_tail = NULL;
 226   _survivor_length = 0;
 227 
 228   _last_sampled_rs_lengths = 0;
 229 
 230   assert(check_list_empty(false), "just making sure...");
 231 }
 232 
 233 bool YoungList::check_list_well_formed() {
 234   bool ret = true;
 235 
 236   uint length = 0;
 237   HeapRegion* curr = _head;
 238   HeapRegion* last = NULL;
 239   while (curr != NULL) {
 240     if (!curr->is_young()) {
 241       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 242                              "incorrectly tagged (y: %d, surv: %d)",
 243                              curr->bottom(), curr->end(),
 244                              curr->is_young(), curr->is_survivor());
 245       ret = false;
 246     }
 247     ++length;
 248     last = curr;
 249     curr = curr->get_next_young_region();
 250   }
 251   ret = ret && (length == _length);
 252 
 253   if (!ret) {
 254     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 255     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 256                            length, _length);
 257   }
 258 
 259   return ret;
 260 }
 261 
 262 bool YoungList::check_list_empty(bool check_sample) {
 263   bool ret = true;
 264 
 265   if (_length != 0) {
 266     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 267                   _length);
 268     ret = false;
 269   }
 270   if (check_sample && _last_sampled_rs_lengths != 0) {
 271     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 272     ret = false;
 273   }
 274   if (_head != NULL) {
 275     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 276     ret = false;
 277   }
 278   if (!ret) {
 279     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 280   }
 281 
 282   return ret;
 283 }
 284 
 285 void
 286 YoungList::rs_length_sampling_init() {
 287   _sampled_rs_lengths = 0;
 288   _curr               = _head;
 289 }
 290 
 291 bool
 292 YoungList::rs_length_sampling_more() {
 293   return _curr != NULL;
 294 }
 295 
 296 void
 297 YoungList::rs_length_sampling_next() {
 298   assert( _curr != NULL, "invariant" );
 299   size_t rs_length = _curr->rem_set()->occupied();
 300 
 301   _sampled_rs_lengths += rs_length;
 302 
 303   // The current region may not yet have been added to the
 304   // incremental collection set (it gets added when it is
 305   // retired as the current allocation region).
 306   if (_curr->in_collection_set()) {
 307     // Update the collection set policy information for this region
 308     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 309   }
 310 
 311   _curr = _curr->get_next_young_region();
 312   if (_curr == NULL) {
 313     _last_sampled_rs_lengths = _sampled_rs_lengths;
 314     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 315   }
 316 }
 317 
 318 void
 319 YoungList::reset_auxilary_lists() {
 320   guarantee( is_empty(), "young list should be empty" );
 321   assert(check_list_well_formed(), "young list should be well formed");
 322 
 323   // Add survivor regions to SurvRateGroup.
 324   _g1h->g1_policy()->note_start_adding_survivor_regions();
 325   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 326 
 327   int young_index_in_cset = 0;
 328   for (HeapRegion* curr = _survivor_head;
 329        curr != NULL;
 330        curr = curr->get_next_young_region()) {
 331     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 332 
 333     // The region is a non-empty survivor so let's add it to
 334     // the incremental collection set for the next evacuation
 335     // pause.
 336     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 337     young_index_in_cset += 1;
 338   }
 339   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 340   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 341 
 342   _head   = _survivor_head;
 343   _length = _survivor_length;
 344   if (_survivor_head != NULL) {
 345     assert(_survivor_tail != NULL, "cause it shouldn't be");
 346     assert(_survivor_length > 0, "invariant");
 347     _survivor_tail->set_next_young_region(NULL);
 348   }
 349 
 350   // Don't clear the survivor list handles until the start of
 351   // the next evacuation pause - we need it in order to re-tag
 352   // the survivor regions from this evacuation pause as 'young'
 353   // at the start of the next.
 354 
 355   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 356 
 357   assert(check_list_well_formed(), "young list should be well formed");
 358 }
 359 
 360 void YoungList::print() {
 361   HeapRegion* lists[] = {_head,   _survivor_head};
 362   const char* names[] = {"YOUNG", "SURVIVOR"};
 363 
 364   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 365     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 366     HeapRegion *curr = lists[list];
 367     if (curr == NULL)
 368       gclog_or_tty->print_cr("  empty");
 369     while (curr != NULL) {
 370       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
 371                              HR_FORMAT_PARAMS(curr),
 372                              curr->prev_top_at_mark_start(),
 373                              curr->next_top_at_mark_start(),
 374                              curr->age_in_surv_rate_group_cond());
 375       curr = curr->get_next_young_region();
 376     }
 377   }
 378 
 379   gclog_or_tty->cr();
 380 }
 381 
 382 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 383 {
 384   // Claim the right to put the region on the dirty cards region list
 385   // by installing a self pointer.
 386   HeapRegion* next = hr->get_next_dirty_cards_region();
 387   if (next == NULL) {
 388     HeapRegion* res = (HeapRegion*)
 389       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 390                           NULL);
 391     if (res == NULL) {
 392       HeapRegion* head;
 393       do {
 394         // Put the region to the dirty cards region list.
 395         head = _dirty_cards_region_list;
 396         next = (HeapRegion*)
 397           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 398         if (next == head) {
 399           assert(hr->get_next_dirty_cards_region() == hr,
 400                  "hr->get_next_dirty_cards_region() != hr");
 401           if (next == NULL) {
 402             // The last region in the list points to itself.
 403             hr->set_next_dirty_cards_region(hr);
 404           } else {
 405             hr->set_next_dirty_cards_region(next);
 406           }
 407         }
 408       } while (next != head);
 409     }
 410   }
 411 }
 412 
 413 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 414 {
 415   HeapRegion* head;
 416   HeapRegion* hr;
 417   do {
 418     head = _dirty_cards_region_list;
 419     if (head == NULL) {
 420       return NULL;
 421     }
 422     HeapRegion* new_head = head->get_next_dirty_cards_region();
 423     if (head == new_head) {
 424       // The last region.
 425       new_head = NULL;
 426     }
 427     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 428                                           head);
 429   } while (hr != head);
 430   assert(hr != NULL, "invariant");
 431   hr->set_next_dirty_cards_region(NULL);
 432   return hr;
 433 }
 434 
 435 void G1CollectedHeap::stop_conc_gc_threads() {
 436   _cg1r->stop();
 437   _cmThread->stop();
 438   if (G1StringDedup::is_enabled()) {
 439     G1StringDedup::stop();
 440   }
 441 }
 442 
 443 #ifdef ASSERT
 444 // A region is added to the collection set as it is retired
 445 // so an address p can point to a region which will be in the
 446 // collection set but has not yet been retired.  This method
 447 // therefore is only accurate during a GC pause after all
 448 // regions have been retired.  It is used for debugging
 449 // to check if an nmethod has references to objects that can
 450 // be move during a partial collection.  Though it can be
 451 // inaccurate, it is sufficient for G1 because the conservative
 452 // implementation of is_scavengable() for G1 will indicate that
 453 // all nmethods must be scanned during a partial collection.
 454 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 455   if (p == NULL) {
 456     return false;
 457   }
 458   return heap_region_containing(p)->in_collection_set();
 459 }
 460 #endif
 461 
 462 // Returns true if the reference points to an object that
 463 // can move in an incremental collection.
 464 bool G1CollectedHeap::is_scavengable(const void* p) {
 465   HeapRegion* hr = heap_region_containing(p);
 466   return !hr->isHumongous();
 467 }
 468 
 469 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 470   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 471   CardTableModRefBS* ct_bs = g1_barrier_set();
 472 
 473   // Count the dirty cards at the start.
 474   CountNonCleanMemRegionClosure count1(this);
 475   ct_bs->mod_card_iterate(&count1);
 476   int orig_count = count1.n();
 477 
 478   // First clear the logged cards.
 479   ClearLoggedCardTableEntryClosure clear;
 480   dcqs.apply_closure_to_all_completed_buffers(&clear);
 481   dcqs.iterate_closure_all_threads(&clear, false);
 482   clear.print_histo();
 483 
 484   // Now ensure that there's no dirty cards.
 485   CountNonCleanMemRegionClosure count2(this);
 486   ct_bs->mod_card_iterate(&count2);
 487   if (count2.n() != 0) {
 488     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 489                            count2.n(), orig_count);
 490   }
 491   guarantee(count2.n() == 0, "Card table should be clean.");
 492 
 493   RedirtyLoggedCardTableEntryClosure redirty;
 494   dcqs.apply_closure_to_all_completed_buffers(&redirty);
 495   dcqs.iterate_closure_all_threads(&redirty, false);
 496   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 497                          clear.num_processed(), orig_count);
 498   guarantee(redirty.num_processed() == clear.num_processed(),
 499             err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
 500                     redirty.num_processed(), clear.num_processed()));
 501 
 502   CountNonCleanMemRegionClosure count3(this);
 503   ct_bs->mod_card_iterate(&count3);
 504   if (count3.n() != orig_count) {
 505     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 506                            orig_count, count3.n());
 507     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 508   }
 509 }
 510 
 511 // Private class members.
 512 
 513 G1CollectedHeap* G1CollectedHeap::_g1h;
 514 
 515 // Private methods.
 516 
 517 HeapRegion*
 518 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 519   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 520   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 521     if (!_secondary_free_list.is_empty()) {
 522       if (G1ConcRegionFreeingVerbose) {
 523         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 524                                "secondary_free_list has %u entries",
 525                                _secondary_free_list.length());
 526       }
 527       // It looks as if there are free regions available on the
 528       // secondary_free_list. Let's move them to the free_list and try
 529       // again to allocate from it.
 530       append_secondary_free_list();
 531 
 532       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
 533              "empty we should have moved at least one entry to the free_list");
 534       HeapRegion* res = _free_list.remove_region(is_old);
 535       if (G1ConcRegionFreeingVerbose) {
 536         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 537                                "allocated "HR_FORMAT" from secondary_free_list",
 538                                HR_FORMAT_PARAMS(res));
 539       }
 540       return res;
 541     }
 542 
 543     // Wait here until we get notified either when (a) there are no
 544     // more free regions coming or (b) some regions have been moved on
 545     // the secondary_free_list.
 546     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 547   }
 548 
 549   if (G1ConcRegionFreeingVerbose) {
 550     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 551                            "could not allocate from secondary_free_list");
 552   }
 553   return NULL;
 554 }
 555 
 556 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 557   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
 558          "the only time we use this to allocate a humongous region is "
 559          "when we are allocating a single humongous region");
 560 
 561   HeapRegion* res;
 562   if (G1StressConcRegionFreeing) {
 563     if (!_secondary_free_list.is_empty()) {
 564       if (G1ConcRegionFreeingVerbose) {
 565         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 566                                "forced to look at the secondary_free_list");
 567       }
 568       res = new_region_try_secondary_free_list(is_old);
 569       if (res != NULL) {
 570         return res;
 571       }
 572     }
 573   }
 574 
 575   res = _free_list.remove_region(is_old);
 576 
 577   if (res == NULL) {
 578     if (G1ConcRegionFreeingVerbose) {
 579       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 580                              "res == NULL, trying the secondary_free_list");
 581     }
 582     res = new_region_try_secondary_free_list(is_old);
 583   }
 584   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 585     // Currently, only attempts to allocate GC alloc regions set
 586     // do_expand to true. So, we should only reach here during a
 587     // safepoint. If this assumption changes we might have to
 588     // reconsider the use of _expand_heap_after_alloc_failure.
 589     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 590 
 591     ergo_verbose1(ErgoHeapSizing,
 592                   "attempt heap expansion",
 593                   ergo_format_reason("region allocation request failed")
 594                   ergo_format_byte("allocation request"),
 595                   word_size * HeapWordSize);
 596     if (expand(word_size * HeapWordSize)) {
 597       // Given that expand() succeeded in expanding the heap, and we
 598       // always expand the heap by an amount aligned to the heap
 599       // region size, the free list should in theory not be empty.
 600       // In either case remove_region() will check for NULL.
 601       res = _free_list.remove_region(is_old);
 602     } else {
 603       _expand_heap_after_alloc_failure = false;
 604     }
 605   }
 606   return res;
 607 }
 608 
 609 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
 610                                                         size_t word_size) {
 611   assert(isHumongous(word_size), "word_size should be humongous");
 612   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 613 
 614   uint first = G1_NULL_HRS_INDEX;
 615   if (num_regions == 1) {
 616     // Only one region to allocate, no need to go through the slower
 617     // path. The caller will attempt the expansion if this fails, so
 618     // let's not try to expand here too.
 619     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 620     if (hr != NULL) {
 621       first = hr->hrs_index();
 622     } else {
 623       first = G1_NULL_HRS_INDEX;
 624     }
 625   } else {
 626     // We can't allocate humongous regions while cleanupComplete() is
 627     // running, since some of the regions we find to be empty might not
 628     // yet be added to the free list and it is not straightforward to
 629     // know which list they are on so that we can remove them. Note
 630     // that we only need to do this if we need to allocate more than
 631     // one region to satisfy the current humongous allocation
 632     // request. If we are only allocating one region we use the common
 633     // region allocation code (see above).
 634     wait_while_free_regions_coming();
 635     append_secondary_free_list_if_not_empty_with_lock();
 636 
 637     if (free_regions() >= num_regions) {
 638       first = _hrs.find_contiguous(num_regions);
 639       if (first != G1_NULL_HRS_INDEX) {
 640         for (uint i = first; i < first + num_regions; ++i) {
 641           HeapRegion* hr = region_at(i);
 642           assert(hr->is_empty(), "sanity");
 643           assert(is_on_master_free_list(hr), "sanity");
 644           hr->set_pending_removal(true);
 645         }
 646         _free_list.remove_all_pending(num_regions);
 647       }
 648     }
 649   }
 650   return first;
 651 }
 652 
 653 HeapWord*
 654 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 655                                                            uint num_regions,
 656                                                            size_t word_size) {
 657   assert(first != G1_NULL_HRS_INDEX, "pre-condition");
 658   assert(isHumongous(word_size), "word_size should be humongous");
 659   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 660 
 661   // Index of last region in the series + 1.
 662   uint last = first + num_regions;
 663 
 664   // We need to initialize the region(s) we just discovered. This is
 665   // a bit tricky given that it can happen concurrently with
 666   // refinement threads refining cards on these regions and
 667   // potentially wanting to refine the BOT as they are scanning
 668   // those cards (this can happen shortly after a cleanup; see CR
 669   // 6991377). So we have to set up the region(s) carefully and in
 670   // a specific order.
 671 
 672   // The word size sum of all the regions we will allocate.
 673   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 674   assert(word_size <= word_size_sum, "sanity");
 675 
 676   // This will be the "starts humongous" region.
 677   HeapRegion* first_hr = region_at(first);
 678   // The header of the new object will be placed at the bottom of
 679   // the first region.
 680   HeapWord* new_obj = first_hr->bottom();
 681   // This will be the new end of the first region in the series that
 682   // should also match the end of the last region in the series.
 683   HeapWord* new_end = new_obj + word_size_sum;
 684   // This will be the new top of the first region that will reflect
 685   // this allocation.
 686   HeapWord* new_top = new_obj + word_size;
 687 
 688   // First, we need to zero the header of the space that we will be
 689   // allocating. When we update top further down, some refinement
 690   // threads might try to scan the region. By zeroing the header we
 691   // ensure that any thread that will try to scan the region will
 692   // come across the zero klass word and bail out.
 693   //
 694   // NOTE: It would not have been correct to have used
 695   // CollectedHeap::fill_with_object() and make the space look like
 696   // an int array. The thread that is doing the allocation will
 697   // later update the object header to a potentially different array
 698   // type and, for a very short period of time, the klass and length
 699   // fields will be inconsistent. This could cause a refinement
 700   // thread to calculate the object size incorrectly.
 701   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 702 
 703   // We will set up the first region as "starts humongous". This
 704   // will also update the BOT covering all the regions to reflect
 705   // that there is a single object that starts at the bottom of the
 706   // first region.
 707   first_hr->set_startsHumongous(new_top, new_end);
 708 
 709   // Then, if there are any, we will set up the "continues
 710   // humongous" regions.
 711   HeapRegion* hr = NULL;
 712   for (uint i = first + 1; i < last; ++i) {
 713     hr = region_at(i);
 714     hr->set_continuesHumongous(first_hr);
 715   }
 716   // If we have "continues humongous" regions (hr != NULL), then the
 717   // end of the last one should match new_end.
 718   assert(hr == NULL || hr->end() == new_end, "sanity");
 719 
 720   // Up to this point no concurrent thread would have been able to
 721   // do any scanning on any region in this series. All the top
 722   // fields still point to bottom, so the intersection between
 723   // [bottom,top] and [card_start,card_end] will be empty. Before we
 724   // update the top fields, we'll do a storestore to make sure that
 725   // no thread sees the update to top before the zeroing of the
 726   // object header and the BOT initialization.
 727   OrderAccess::storestore();
 728 
 729   // Now that the BOT and the object header have been initialized,
 730   // we can update top of the "starts humongous" region.
 731   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 732          "new_top should be in this region");
 733   first_hr->set_top(new_top);
 734   if (_hr_printer.is_active()) {
 735     HeapWord* bottom = first_hr->bottom();
 736     HeapWord* end = first_hr->orig_end();
 737     if ((first + 1) == last) {
 738       // the series has a single humongous region
 739       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 740     } else {
 741       // the series has more than one humongous regions
 742       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 743     }
 744   }
 745 
 746   // Now, we will update the top fields of the "continues humongous"
 747   // regions. The reason we need to do this is that, otherwise,
 748   // these regions would look empty and this will confuse parts of
 749   // G1. For example, the code that looks for a consecutive number
 750   // of empty regions will consider them empty and try to
 751   // re-allocate them. We can extend is_empty() to also include
 752   // !continuesHumongous(), but it is easier to just update the top
 753   // fields here. The way we set top for all regions (i.e., top ==
 754   // end for all regions but the last one, top == new_top for the
 755   // last one) is actually used when we will free up the humongous
 756   // region in free_humongous_region().
 757   hr = NULL;
 758   for (uint i = first + 1; i < last; ++i) {
 759     hr = region_at(i);
 760     if ((i + 1) == last) {
 761       // last continues humongous region
 762       assert(hr->bottom() < new_top && new_top <= hr->end(),
 763              "new_top should fall on this region");
 764       hr->set_top(new_top);
 765       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 766     } else {
 767       // not last one
 768       assert(new_top > hr->end(), "new_top should be above this region");
 769       hr->set_top(hr->end());
 770       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 771     }
 772   }
 773   // If we have continues humongous regions (hr != NULL), then the
 774   // end of the last one should match new_end and its top should
 775   // match new_top.
 776   assert(hr == NULL ||
 777          (hr->end() == new_end && hr->top() == new_top), "sanity");
 778   check_bitmaps("Humongous Region Allocation", first_hr);
 779 
 780   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 781   _summary_bytes_used += first_hr->used();
 782   _humongous_set.add(first_hr);
 783 
 784   return new_obj;
 785 }
 786 
 787 // If could fit into free regions w/o expansion, try.
 788 // Otherwise, if can expand, do so.
 789 // Otherwise, if using ex regions might help, try with ex given back.
 790 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 791   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 792 
 793   verify_region_sets_optional();
 794 
 795   size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
 796   uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
 797   uint x_num = expansion_regions();
 798   uint fs = _hrs.free_suffix();
 799   uint first = humongous_obj_allocate_find_first(num_regions, word_size);
 800   if (first == G1_NULL_HRS_INDEX) {
 801     // The only thing we can do now is attempt expansion.
 802     if (fs + x_num >= num_regions) {
 803       // If the number of regions we're trying to allocate for this
 804       // object is at most the number of regions in the free suffix,
 805       // then the call to humongous_obj_allocate_find_first() above
 806       // should have succeeded and we wouldn't be here.
 807       //
 808       // We should only be trying to expand when the free suffix is
 809       // not sufficient for the object _and_ we have some expansion
 810       // room available.
 811       assert(num_regions > fs, "earlier allocation should have succeeded");
 812 
 813       ergo_verbose1(ErgoHeapSizing,
 814                     "attempt heap expansion",
 815                     ergo_format_reason("humongous allocation request failed")
 816                     ergo_format_byte("allocation request"),
 817                     word_size * HeapWordSize);
 818       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
 819         // Even though the heap was expanded, it might not have
 820         // reached the desired size. So, we cannot assume that the
 821         // allocation will succeed.
 822         first = humongous_obj_allocate_find_first(num_regions, word_size);
 823       }
 824     }
 825   }
 826 
 827   HeapWord* result = NULL;
 828   if (first != G1_NULL_HRS_INDEX) {
 829     result =
 830       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
 831     assert(result != NULL, "it should always return a valid result");
 832 
 833     // A successful humongous object allocation changes the used space
 834     // information of the old generation so we need to recalculate the
 835     // sizes and update the jstat counters here.
 836     g1mm()->update_sizes();
 837   }
 838 
 839   verify_region_sets_optional();
 840 
 841   return result;
 842 }
 843 
 844 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 845   assert_heap_not_locked_and_not_at_safepoint();
 846   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
 847 
 848   unsigned int dummy_gc_count_before;
 849   int dummy_gclocker_retry_count = 0;
 850   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 851 }
 852 
 853 HeapWord*
 854 G1CollectedHeap::mem_allocate(size_t word_size,
 855                               bool*  gc_overhead_limit_was_exceeded) {
 856   assert_heap_not_locked_and_not_at_safepoint();
 857 
 858   // Loop until the allocation is satisfied, or unsatisfied after GC.
 859   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 860     unsigned int gc_count_before;
 861 
 862     HeapWord* result = NULL;
 863     if (!isHumongous(word_size)) {
 864       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 865     } else {
 866       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 867     }
 868     if (result != NULL) {
 869       return result;
 870     }
 871 
 872     // Create the garbage collection operation...
 873     VM_G1CollectForAllocation op(gc_count_before, word_size);
 874     // ...and get the VM thread to execute it.
 875     VMThread::execute(&op);
 876 
 877     if (op.prologue_succeeded() && op.pause_succeeded()) {
 878       // If the operation was successful we'll return the result even
 879       // if it is NULL. If the allocation attempt failed immediately
 880       // after a Full GC, it's unlikely we'll be able to allocate now.
 881       HeapWord* result = op.result();
 882       if (result != NULL && !isHumongous(word_size)) {
 883         // Allocations that take place on VM operations do not do any
 884         // card dirtying and we have to do it here. We only have to do
 885         // this for non-humongous allocations, though.
 886         dirty_young_block(result, word_size);
 887       }
 888       return result;
 889     } else {
 890       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 891         return NULL;
 892       }
 893       assert(op.result() == NULL,
 894              "the result should be NULL if the VM op did not succeed");
 895     }
 896 
 897     // Give a warning if we seem to be looping forever.
 898     if ((QueuedAllocationWarningCount > 0) &&
 899         (try_count % QueuedAllocationWarningCount == 0)) {
 900       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 901     }
 902   }
 903 
 904   ShouldNotReachHere();
 905   return NULL;
 906 }
 907 
 908 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 909                                            unsigned int *gc_count_before_ret,
 910                                            int* gclocker_retry_count_ret) {
 911   // Make sure you read the note in attempt_allocation_humongous().
 912 
 913   assert_heap_not_locked_and_not_at_safepoint();
 914   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
 915          "be called for humongous allocation requests");
 916 
 917   // We should only get here after the first-level allocation attempt
 918   // (attempt_allocation()) failed to allocate.
 919 
 920   // We will loop until a) we manage to successfully perform the
 921   // allocation or b) we successfully schedule a collection which
 922   // fails to perform the allocation. b) is the only case when we'll
 923   // return NULL.
 924   HeapWord* result = NULL;
 925   for (int try_count = 1; /* we'll return */; try_count += 1) {
 926     bool should_try_gc;
 927     unsigned int gc_count_before;
 928 
 929     {
 930       MutexLockerEx x(Heap_lock);
 931 
 932       result = _mutator_alloc_region.attempt_allocation_locked(word_size,
 933                                                       false /* bot_updates */);
 934       if (result != NULL) {
 935         return result;
 936       }
 937 
 938       // If we reach here, attempt_allocation_locked() above failed to
 939       // allocate a new region. So the mutator alloc region should be NULL.
 940       assert(_mutator_alloc_region.get() == NULL, "only way to get here");
 941 
 942       if (GC_locker::is_active_and_needs_gc()) {
 943         if (g1_policy()->can_expand_young_list()) {
 944           // No need for an ergo verbose message here,
 945           // can_expand_young_list() does this when it returns true.
 946           result = _mutator_alloc_region.attempt_allocation_force(word_size,
 947                                                       false /* bot_updates */);
 948           if (result != NULL) {
 949             return result;
 950           }
 951         }
 952         should_try_gc = false;
 953       } else {
 954         // The GCLocker may not be active but the GCLocker initiated
 955         // GC may not yet have been performed (GCLocker::needs_gc()
 956         // returns true). In this case we do not try this GC and
 957         // wait until the GCLocker initiated GC is performed, and
 958         // then retry the allocation.
 959         if (GC_locker::needs_gc()) {
 960           should_try_gc = false;
 961         } else {
 962           // Read the GC count while still holding the Heap_lock.
 963           gc_count_before = total_collections();
 964           should_try_gc = true;
 965         }
 966       }
 967     }
 968 
 969     if (should_try_gc) {
 970       bool succeeded;
 971       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 972           GCCause::_g1_inc_collection_pause);
 973       if (result != NULL) {
 974         assert(succeeded, "only way to get back a non-NULL result");
 975         return result;
 976       }
 977 
 978       if (succeeded) {
 979         // If we get here we successfully scheduled a collection which
 980         // failed to allocate. No point in trying to allocate
 981         // further. We'll just return NULL.
 982         MutexLockerEx x(Heap_lock);
 983         *gc_count_before_ret = total_collections();
 984         return NULL;
 985       }
 986     } else {
 987       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 988         MutexLockerEx x(Heap_lock);
 989         *gc_count_before_ret = total_collections();
 990         return NULL;
 991       }
 992       // The GCLocker is either active or the GCLocker initiated
 993       // GC has not yet been performed. Stall until it is and
 994       // then retry the allocation.
 995       GC_locker::stall_until_clear();
 996       (*gclocker_retry_count_ret) += 1;
 997     }
 998 
 999     // We can reach here if we were unsuccessful in scheduling a
1000     // collection (because another thread beat us to it) or if we were
1001     // stalled due to the GC locker. In either can we should retry the
1002     // allocation attempt in case another thread successfully
1003     // performed a collection and reclaimed enough space. We do the
1004     // first attempt (without holding the Heap_lock) here and the
1005     // follow-on attempt will be at the start of the next loop
1006     // iteration (after taking the Heap_lock).
1007     result = _mutator_alloc_region.attempt_allocation(word_size,
1008                                                       false /* bot_updates */);
1009     if (result != NULL) {
1010       return result;
1011     }
1012 
1013     // Give a warning if we seem to be looping forever.
1014     if ((QueuedAllocationWarningCount > 0) &&
1015         (try_count % QueuedAllocationWarningCount == 0)) {
1016       warning("G1CollectedHeap::attempt_allocation_slow() "
1017               "retries %d times", try_count);
1018     }
1019   }
1020 
1021   ShouldNotReachHere();
1022   return NULL;
1023 }
1024 
1025 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1026                                           unsigned int * gc_count_before_ret,
1027                                           int* gclocker_retry_count_ret) {
1028   // The structure of this method has a lot of similarities to
1029   // attempt_allocation_slow(). The reason these two were not merged
1030   // into a single one is that such a method would require several "if
1031   // allocation is not humongous do this, otherwise do that"
1032   // conditional paths which would obscure its flow. In fact, an early
1033   // version of this code did use a unified method which was harder to
1034   // follow and, as a result, it had subtle bugs that were hard to
1035   // track down. So keeping these two methods separate allows each to
1036   // be more readable. It will be good to keep these two in sync as
1037   // much as possible.
1038 
1039   assert_heap_not_locked_and_not_at_safepoint();
1040   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1041          "should only be called for humongous allocations");
1042 
1043   // Humongous objects can exhaust the heap quickly, so we should check if we
1044   // need to start a marking cycle at each humongous object allocation. We do
1045   // the check before we do the actual allocation. The reason for doing it
1046   // before the allocation is that we avoid having to keep track of the newly
1047   // allocated memory while we do a GC.
1048   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1049                                            word_size)) {
1050     collect(GCCause::_g1_humongous_allocation);
1051   }
1052 
1053   // We will loop until a) we manage to successfully perform the
1054   // allocation or b) we successfully schedule a collection which
1055   // fails to perform the allocation. b) is the only case when we'll
1056   // return NULL.
1057   HeapWord* result = NULL;
1058   for (int try_count = 1; /* we'll return */; try_count += 1) {
1059     bool should_try_gc;
1060     unsigned int gc_count_before;
1061 
1062     {
1063       MutexLockerEx x(Heap_lock);
1064 
1065       // Given that humongous objects are not allocated in young
1066       // regions, we'll first try to do the allocation without doing a
1067       // collection hoping that there's enough space in the heap.
1068       result = humongous_obj_allocate(word_size);
1069       if (result != NULL) {
1070         return result;
1071       }
1072 
1073       if (GC_locker::is_active_and_needs_gc()) {
1074         should_try_gc = false;
1075       } else {
1076          // The GCLocker may not be active but the GCLocker initiated
1077         // GC may not yet have been performed (GCLocker::needs_gc()
1078         // returns true). In this case we do not try this GC and
1079         // wait until the GCLocker initiated GC is performed, and
1080         // then retry the allocation.
1081         if (GC_locker::needs_gc()) {
1082           should_try_gc = false;
1083         } else {
1084           // Read the GC count while still holding the Heap_lock.
1085           gc_count_before = total_collections();
1086           should_try_gc = true;
1087         }
1088       }
1089     }
1090 
1091     if (should_try_gc) {
1092       // If we failed to allocate the humongous object, we should try to
1093       // do a collection pause (if we're allowed) in case it reclaims
1094       // enough space for the allocation to succeed after the pause.
1095 
1096       bool succeeded;
1097       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1098           GCCause::_g1_humongous_allocation);
1099       if (result != NULL) {
1100         assert(succeeded, "only way to get back a non-NULL result");
1101         return result;
1102       }
1103 
1104       if (succeeded) {
1105         // If we get here we successfully scheduled a collection which
1106         // failed to allocate. No point in trying to allocate
1107         // further. We'll just return NULL.
1108         MutexLockerEx x(Heap_lock);
1109         *gc_count_before_ret = total_collections();
1110         return NULL;
1111       }
1112     } else {
1113       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1114         MutexLockerEx x(Heap_lock);
1115         *gc_count_before_ret = total_collections();
1116         return NULL;
1117       }
1118       // The GCLocker is either active or the GCLocker initiated
1119       // GC has not yet been performed. Stall until it is and
1120       // then retry the allocation.
1121       GC_locker::stall_until_clear();
1122       (*gclocker_retry_count_ret) += 1;
1123     }
1124 
1125     // We can reach here if we were unsuccessful in scheduling a
1126     // collection (because another thread beat us to it) or if we were
1127     // stalled due to the GC locker. In either can we should retry the
1128     // allocation attempt in case another thread successfully
1129     // performed a collection and reclaimed enough space.  Give a
1130     // warning if we seem to be looping forever.
1131 
1132     if ((QueuedAllocationWarningCount > 0) &&
1133         (try_count % QueuedAllocationWarningCount == 0)) {
1134       warning("G1CollectedHeap::attempt_allocation_humongous() "
1135               "retries %d times", try_count);
1136     }
1137   }
1138 
1139   ShouldNotReachHere();
1140   return NULL;
1141 }
1142 
1143 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1144                                        bool expect_null_mutator_alloc_region) {
1145   assert_at_safepoint(true /* should_be_vm_thread */);
1146   assert(_mutator_alloc_region.get() == NULL ||
1147                                              !expect_null_mutator_alloc_region,
1148          "the current alloc region was unexpectedly found to be non-NULL");
1149 
1150   if (!isHumongous(word_size)) {
1151     return _mutator_alloc_region.attempt_allocation_locked(word_size,
1152                                                       false /* bot_updates */);
1153   } else {
1154     HeapWord* result = humongous_obj_allocate(word_size);
1155     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1156       g1_policy()->set_initiate_conc_mark_if_possible();
1157     }
1158     return result;
1159   }
1160 
1161   ShouldNotReachHere();
1162 }
1163 
1164 class PostMCRemSetClearClosure: public HeapRegionClosure {
1165   G1CollectedHeap* _g1h;
1166   ModRefBarrierSet* _mr_bs;
1167 public:
1168   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1169     _g1h(g1h), _mr_bs(mr_bs) {}
1170 
1171   bool doHeapRegion(HeapRegion* r) {
1172     HeapRegionRemSet* hrrs = r->rem_set();
1173 
1174     if (r->continuesHumongous()) {
1175       // We'll assert that the strong code root list and RSet is empty
1176       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1177       assert(hrrs->occupied() == 0, "RSet should be empty");
1178       return false;
1179     }
1180 
1181     _g1h->reset_gc_time_stamps(r);
1182     hrrs->clear();
1183     // You might think here that we could clear just the cards
1184     // corresponding to the used region.  But no: if we leave a dirty card
1185     // in a region we might allocate into, then it would prevent that card
1186     // from being enqueued, and cause it to be missed.
1187     // Re: the performance cost: we shouldn't be doing full GC anyway!
1188     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1189 
1190     return false;
1191   }
1192 };
1193 
1194 void G1CollectedHeap::clear_rsets_post_compaction() {
1195   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1196   heap_region_iterate(&rs_clear);
1197 }
1198 
1199 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1200   G1CollectedHeap*   _g1h;
1201   UpdateRSOopClosure _cl;
1202   int                _worker_i;
1203 public:
1204   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1205     _cl(g1->g1_rem_set(), worker_i),
1206     _worker_i(worker_i),
1207     _g1h(g1)
1208   { }
1209 
1210   bool doHeapRegion(HeapRegion* r) {
1211     if (!r->continuesHumongous()) {
1212       _cl.set_from(r);
1213       r->oop_iterate(&_cl);
1214     }
1215     return false;
1216   }
1217 };
1218 
1219 class ParRebuildRSTask: public AbstractGangTask {
1220   G1CollectedHeap* _g1;
1221 public:
1222   ParRebuildRSTask(G1CollectedHeap* g1)
1223     : AbstractGangTask("ParRebuildRSTask"),
1224       _g1(g1)
1225   { }
1226 
1227   void work(uint worker_id) {
1228     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1229     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1230                                           _g1->workers()->active_workers(),
1231                                          HeapRegion::RebuildRSClaimValue);
1232   }
1233 };
1234 
1235 class PostCompactionPrinterClosure: public HeapRegionClosure {
1236 private:
1237   G1HRPrinter* _hr_printer;
1238 public:
1239   bool doHeapRegion(HeapRegion* hr) {
1240     assert(!hr->is_young(), "not expecting to find young regions");
1241     // We only generate output for non-empty regions.
1242     if (!hr->is_empty()) {
1243       if (!hr->isHumongous()) {
1244         _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1245       } else if (hr->startsHumongous()) {
1246         if (hr->region_num() == 1) {
1247           // single humongous region
1248           _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1249         } else {
1250           _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1251         }
1252       } else {
1253         assert(hr->continuesHumongous(), "only way to get here");
1254         _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1255       }
1256     }
1257     return false;
1258   }
1259 
1260   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1261     : _hr_printer(hr_printer) { }
1262 };
1263 
1264 void G1CollectedHeap::print_hrs_post_compaction() {
1265   PostCompactionPrinterClosure cl(hr_printer());
1266   heap_region_iterate(&cl);
1267 }
1268 
1269 bool G1CollectedHeap::do_collection(bool explicit_gc,
1270                                     bool clear_all_soft_refs,
1271                                     size_t word_size) {
1272   assert_at_safepoint(true /* should_be_vm_thread */);
1273 
1274   if (GC_locker::check_active_before_gc()) {
1275     return false;
1276   }
1277 
1278   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1279   gc_timer->register_gc_start();
1280 
1281   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1282   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1283 
1284   SvcGCMarker sgcm(SvcGCMarker::FULL);
1285   ResourceMark rm;
1286 
1287   print_heap_before_gc();
1288   trace_heap_before_gc(gc_tracer);
1289 
1290   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1291 
1292   verify_region_sets_optional();
1293 
1294   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1295                            collector_policy()->should_clear_all_soft_refs();
1296 
1297   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1298 
1299   {
1300     IsGCActiveMark x;
1301 
1302     // Timing
1303     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1304     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1305     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1306 
1307     {
1308       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1309       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1310       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1311 
1312       double start = os::elapsedTime();
1313       g1_policy()->record_full_collection_start();
1314 
1315       // Note: When we have a more flexible GC logging framework that
1316       // allows us to add optional attributes to a GC log record we
1317       // could consider timing and reporting how long we wait in the
1318       // following two methods.
1319       wait_while_free_regions_coming();
1320       // If we start the compaction before the CM threads finish
1321       // scanning the root regions we might trip them over as we'll
1322       // be moving objects / updating references. So let's wait until
1323       // they are done. By telling them to abort, they should complete
1324       // early.
1325       _cm->root_regions()->abort();
1326       _cm->root_regions()->wait_until_scan_finished();
1327       append_secondary_free_list_if_not_empty_with_lock();
1328 
1329       gc_prologue(true);
1330       increment_total_collections(true /* full gc */);
1331       increment_old_marking_cycles_started();
1332 
1333       assert(used() == recalculate_used(), "Should be equal");
1334 
1335       verify_before_gc();
1336 
1337       check_bitmaps("Full GC Start");
1338       pre_full_gc_dump(gc_timer);
1339 
1340       COMPILER2_PRESENT(DerivedPointerTable::clear());
1341 
1342       // Disable discovery and empty the discovered lists
1343       // for the CM ref processor.
1344       ref_processor_cm()->disable_discovery();
1345       ref_processor_cm()->abandon_partial_discovery();
1346       ref_processor_cm()->verify_no_references_recorded();
1347 
1348       // Abandon current iterations of concurrent marking and concurrent
1349       // refinement, if any are in progress. We have to do this before
1350       // wait_until_scan_finished() below.
1351       concurrent_mark()->abort();
1352 
1353       // Make sure we'll choose a new allocation region afterwards.
1354       release_mutator_alloc_region();
1355       abandon_gc_alloc_regions();
1356       g1_rem_set()->cleanupHRRS();
1357 
1358       // We should call this after we retire any currently active alloc
1359       // regions so that all the ALLOC / RETIRE events are generated
1360       // before the start GC event.
1361       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1362 
1363       // We may have added regions to the current incremental collection
1364       // set between the last GC or pause and now. We need to clear the
1365       // incremental collection set and then start rebuilding it afresh
1366       // after this full GC.
1367       abandon_collection_set(g1_policy()->inc_cset_head());
1368       g1_policy()->clear_incremental_cset();
1369       g1_policy()->stop_incremental_cset_building();
1370 
1371       tear_down_region_sets(false /* free_list_only */);
1372       g1_policy()->set_gcs_are_young(true);
1373 
1374       // See the comments in g1CollectedHeap.hpp and
1375       // G1CollectedHeap::ref_processing_init() about
1376       // how reference processing currently works in G1.
1377 
1378       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1379       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1380 
1381       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1382       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1383 
1384       ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1385       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1386 
1387       // Do collection work
1388       {
1389         HandleMark hm;  // Discard invalid handles created during gc
1390         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1391       }
1392 
1393       assert(free_regions() == 0, "we should not have added any free regions");
1394       rebuild_region_sets(false /* free_list_only */);
1395 
1396       // Enqueue any discovered reference objects that have
1397       // not been removed from the discovered lists.
1398       ref_processor_stw()->enqueue_discovered_references();
1399 
1400       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1401 
1402       MemoryService::track_memory_usage();
1403 
1404       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1405       ref_processor_stw()->verify_no_references_recorded();
1406 
1407       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1408       ClassLoaderDataGraph::purge();
1409       MetaspaceAux::verify_metrics();
1410 
1411       // Note: since we've just done a full GC, concurrent
1412       // marking is no longer active. Therefore we need not
1413       // re-enable reference discovery for the CM ref processor.
1414       // That will be done at the start of the next marking cycle.
1415       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1416       ref_processor_cm()->verify_no_references_recorded();
1417 
1418       reset_gc_time_stamp();
1419       // Since everything potentially moved, we will clear all remembered
1420       // sets, and clear all cards.  Later we will rebuild remembered
1421       // sets. We will also reset the GC time stamps of the regions.
1422       clear_rsets_post_compaction();
1423       check_gc_time_stamps();
1424 
1425       // Resize the heap if necessary.
1426       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1427 
1428       if (_hr_printer.is_active()) {
1429         // We should do this after we potentially resize the heap so
1430         // that all the COMMIT / UNCOMMIT events are generated before
1431         // the end GC event.
1432 
1433         print_hrs_post_compaction();
1434         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1435       }
1436 
1437       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1438       if (hot_card_cache->use_cache()) {
1439         hot_card_cache->reset_card_counts();
1440         hot_card_cache->reset_hot_cache();
1441       }
1442 
1443       // Rebuild remembered sets of all regions.
1444       if (G1CollectedHeap::use_parallel_gc_threads()) {
1445         uint n_workers =
1446           AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1447                                                   workers()->active_workers(),
1448                                                   Threads::number_of_non_daemon_threads());
1449         assert(UseDynamicNumberOfGCThreads ||
1450                n_workers == workers()->total_workers(),
1451                "If not dynamic should be using all the  workers");
1452         workers()->set_active_workers(n_workers);
1453         // Set parallel threads in the heap (_n_par_threads) only
1454         // before a parallel phase and always reset it to 0 after
1455         // the phase so that the number of parallel threads does
1456         // no get carried forward to a serial phase where there
1457         // may be code that is "possibly_parallel".
1458         set_par_threads(n_workers);
1459 
1460         ParRebuildRSTask rebuild_rs_task(this);
1461         assert(check_heap_region_claim_values(
1462                HeapRegion::InitialClaimValue), "sanity check");
1463         assert(UseDynamicNumberOfGCThreads ||
1464                workers()->active_workers() == workers()->total_workers(),
1465                "Unless dynamic should use total workers");
1466         // Use the most recent number of  active workers
1467         assert(workers()->active_workers() > 0,
1468                "Active workers not properly set");
1469         set_par_threads(workers()->active_workers());
1470         workers()->run_task(&rebuild_rs_task);
1471         set_par_threads(0);
1472         assert(check_heap_region_claim_values(
1473                HeapRegion::RebuildRSClaimValue), "sanity check");
1474         reset_heap_region_claim_values();
1475       } else {
1476         RebuildRSOutOfRegionClosure rebuild_rs(this);
1477         heap_region_iterate(&rebuild_rs);
1478       }
1479 
1480       // Rebuild the strong code root lists for each region
1481       rebuild_strong_code_roots();
1482 
1483       if (true) { // FIXME
1484         MetaspaceGC::compute_new_size();
1485       }
1486 
1487 #ifdef TRACESPINNING
1488       ParallelTaskTerminator::print_termination_counts();
1489 #endif
1490 
1491       // Discard all rset updates
1492       JavaThread::dirty_card_queue_set().abandon_logs();
1493       assert(!G1DeferredRSUpdate
1494              || (G1DeferredRSUpdate &&
1495                 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1496 
1497       _young_list->reset_sampled_info();
1498       // At this point there should be no regions in the
1499       // entire heap tagged as young.
1500       assert(check_young_list_empty(true /* check_heap */),
1501              "young list should be empty at this point");
1502 
1503       // Update the number of full collections that have been completed.
1504       increment_old_marking_cycles_completed(false /* concurrent */);
1505 
1506       _hrs.verify_optional();
1507       verify_region_sets_optional();
1508 
1509       verify_after_gc();
1510 
1511       // Clear the previous marking bitmap, if needed for bitmap verification.
1512       // Note we cannot do this when we clear the next marking bitmap in
1513       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1514       // objects marked during a full GC against the previous bitmap.
1515       // But we need to clear it before calling check_bitmaps below since
1516       // the full GC has compacted objects and updated TAMS but not updated
1517       // the prev bitmap.
1518       if (G1VerifyBitmaps) {
1519         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1520       }
1521       check_bitmaps("Full GC End");
1522 
1523       // Start a new incremental collection set for the next pause
1524       assert(g1_policy()->collection_set() == NULL, "must be");
1525       g1_policy()->start_incremental_cset_building();
1526 
1527       clear_cset_fast_test();
1528 
1529       init_mutator_alloc_region();
1530 
1531       double end = os::elapsedTime();
1532       g1_policy()->record_full_collection_end();
1533 
1534       if (G1Log::fine()) {
1535         g1_policy()->print_heap_transition();
1536       }
1537 
1538       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1539       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1540       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1541       // before any GC notifications are raised.
1542       g1mm()->update_sizes();
1543 
1544       gc_epilogue(true);
1545     }
1546 
1547     if (G1Log::finer()) {
1548       g1_policy()->print_detailed_heap_transition(true /* full */);
1549     }
1550 
1551     print_heap_after_gc();
1552     trace_heap_after_gc(gc_tracer);
1553 
1554     post_full_gc_dump(gc_timer);
1555 
1556     gc_timer->register_gc_end();
1557     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1558   }
1559 
1560   return true;
1561 }
1562 
1563 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1564   // do_collection() will return whether it succeeded in performing
1565   // the GC. Currently, there is no facility on the
1566   // do_full_collection() API to notify the caller than the collection
1567   // did not succeed (e.g., because it was locked out by the GC
1568   // locker). So, right now, we'll ignore the return value.
1569   bool dummy = do_collection(true,                /* explicit_gc */
1570                              clear_all_soft_refs,
1571                              0                    /* word_size */);
1572 }
1573 
1574 // This code is mostly copied from TenuredGeneration.
1575 void
1576 G1CollectedHeap::
1577 resize_if_necessary_after_full_collection(size_t word_size) {
1578   // Include the current allocation, if any, and bytes that will be
1579   // pre-allocated to support collections, as "used".
1580   const size_t used_after_gc = used();
1581   const size_t capacity_after_gc = capacity();
1582   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1583 
1584   // This is enforced in arguments.cpp.
1585   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1586          "otherwise the code below doesn't make sense");
1587 
1588   // We don't have floating point command-line arguments
1589   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1590   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1591   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1592   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1593 
1594   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1595   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1596 
1597   // We have to be careful here as these two calculations can overflow
1598   // 32-bit size_t's.
1599   double used_after_gc_d = (double) used_after_gc;
1600   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1601   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1602 
1603   // Let's make sure that they are both under the max heap size, which
1604   // by default will make them fit into a size_t.
1605   double desired_capacity_upper_bound = (double) max_heap_size;
1606   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1607                                     desired_capacity_upper_bound);
1608   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1609                                     desired_capacity_upper_bound);
1610 
1611   // We can now safely turn them into size_t's.
1612   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1613   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1614 
1615   // This assert only makes sense here, before we adjust them
1616   // with respect to the min and max heap size.
1617   assert(minimum_desired_capacity <= maximum_desired_capacity,
1618          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1619                  "maximum_desired_capacity = "SIZE_FORMAT,
1620                  minimum_desired_capacity, maximum_desired_capacity));
1621 
1622   // Should not be greater than the heap max size. No need to adjust
1623   // it with respect to the heap min size as it's a lower bound (i.e.,
1624   // we'll try to make the capacity larger than it, not smaller).
1625   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1626   // Should not be less than the heap min size. No need to adjust it
1627   // with respect to the heap max size as it's an upper bound (i.e.,
1628   // we'll try to make the capacity smaller than it, not greater).
1629   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1630 
1631   if (capacity_after_gc < minimum_desired_capacity) {
1632     // Don't expand unless it's significant
1633     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1634     ergo_verbose4(ErgoHeapSizing,
1635                   "attempt heap expansion",
1636                   ergo_format_reason("capacity lower than "
1637                                      "min desired capacity after Full GC")
1638                   ergo_format_byte("capacity")
1639                   ergo_format_byte("occupancy")
1640                   ergo_format_byte_perc("min desired capacity"),
1641                   capacity_after_gc, used_after_gc,
1642                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1643     expand(expand_bytes);
1644 
1645     // No expansion, now see if we want to shrink
1646   } else if (capacity_after_gc > maximum_desired_capacity) {
1647     // Capacity too large, compute shrinking size
1648     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1649     ergo_verbose4(ErgoHeapSizing,
1650                   "attempt heap shrinking",
1651                   ergo_format_reason("capacity higher than "
1652                                      "max desired capacity after Full GC")
1653                   ergo_format_byte("capacity")
1654                   ergo_format_byte("occupancy")
1655                   ergo_format_byte_perc("max desired capacity"),
1656                   capacity_after_gc, used_after_gc,
1657                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1658     shrink(shrink_bytes);
1659   }
1660 }
1661 
1662 
1663 HeapWord*
1664 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1665                                            bool* succeeded) {
1666   assert_at_safepoint(true /* should_be_vm_thread */);
1667 
1668   *succeeded = true;
1669   // Let's attempt the allocation first.
1670   HeapWord* result =
1671     attempt_allocation_at_safepoint(word_size,
1672                                  false /* expect_null_mutator_alloc_region */);
1673   if (result != NULL) {
1674     assert(*succeeded, "sanity");
1675     return result;
1676   }
1677 
1678   // In a G1 heap, we're supposed to keep allocation from failing by
1679   // incremental pauses.  Therefore, at least for now, we'll favor
1680   // expansion over collection.  (This might change in the future if we can
1681   // do something smarter than full collection to satisfy a failed alloc.)
1682   result = expand_and_allocate(word_size);
1683   if (result != NULL) {
1684     assert(*succeeded, "sanity");
1685     return result;
1686   }
1687 
1688   // Expansion didn't work, we'll try to do a Full GC.
1689   bool gc_succeeded = do_collection(false, /* explicit_gc */
1690                                     false, /* clear_all_soft_refs */
1691                                     word_size);
1692   if (!gc_succeeded) {
1693     *succeeded = false;
1694     return NULL;
1695   }
1696 
1697   // Retry the allocation
1698   result = attempt_allocation_at_safepoint(word_size,
1699                                   true /* expect_null_mutator_alloc_region */);
1700   if (result != NULL) {
1701     assert(*succeeded, "sanity");
1702     return result;
1703   }
1704 
1705   // Then, try a Full GC that will collect all soft references.
1706   gc_succeeded = do_collection(false, /* explicit_gc */
1707                                true,  /* clear_all_soft_refs */
1708                                word_size);
1709   if (!gc_succeeded) {
1710     *succeeded = false;
1711     return NULL;
1712   }
1713 
1714   // Retry the allocation once more
1715   result = attempt_allocation_at_safepoint(word_size,
1716                                   true /* expect_null_mutator_alloc_region */);
1717   if (result != NULL) {
1718     assert(*succeeded, "sanity");
1719     return result;
1720   }
1721 
1722   assert(!collector_policy()->should_clear_all_soft_refs(),
1723          "Flag should have been handled and cleared prior to this point");
1724 
1725   // What else?  We might try synchronous finalization later.  If the total
1726   // space available is large enough for the allocation, then a more
1727   // complete compaction phase than we've tried so far might be
1728   // appropriate.
1729   assert(*succeeded, "sanity");
1730   return NULL;
1731 }
1732 
1733 // Attempting to expand the heap sufficiently
1734 // to support an allocation of the given "word_size".  If
1735 // successful, perform the allocation and return the address of the
1736 // allocated block, or else "NULL".
1737 
1738 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1739   assert_at_safepoint(true /* should_be_vm_thread */);
1740 
1741   verify_region_sets_optional();
1742 
1743   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1744   ergo_verbose1(ErgoHeapSizing,
1745                 "attempt heap expansion",
1746                 ergo_format_reason("allocation request failed")
1747                 ergo_format_byte("allocation request"),
1748                 word_size * HeapWordSize);
1749   if (expand(expand_bytes)) {
1750     _hrs.verify_optional();
1751     verify_region_sets_optional();
1752     return attempt_allocation_at_safepoint(word_size,
1753                                  false /* expect_null_mutator_alloc_region */);
1754   }
1755   return NULL;
1756 }
1757 
1758 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1759                                              HeapWord* new_end) {
1760   assert(old_end != new_end, "don't call this otherwise");
1761   assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1762 
1763   // Update the committed mem region.
1764   _g1_committed.set_end(new_end);
1765   // Tell the card table about the update.
1766   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1767   // Tell the BOT about the update.
1768   _bot_shared->resize(_g1_committed.word_size());
1769   // Tell the hot card cache about the update
1770   _cg1r->hot_card_cache()->resize_card_counts(capacity());
1771 }
1772 
1773 bool G1CollectedHeap::expand(size_t expand_bytes) {
1774   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1775   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1776                                        HeapRegion::GrainBytes);
1777   ergo_verbose2(ErgoHeapSizing,
1778                 "expand the heap",
1779                 ergo_format_byte("requested expansion amount")
1780                 ergo_format_byte("attempted expansion amount"),
1781                 expand_bytes, aligned_expand_bytes);
1782 
1783   if (_g1_storage.uncommitted_size() == 0) {
1784     ergo_verbose0(ErgoHeapSizing,
1785                       "did not expand the heap",
1786                       ergo_format_reason("heap already fully expanded"));
1787     return false;
1788   }
1789 
1790   // First commit the memory.
1791   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1792   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1793   if (successful) {
1794     // Then propagate this update to the necessary data structures.
1795     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1796     update_committed_space(old_end, new_end);
1797 
1798     FreeRegionList expansion_list("Local Expansion List");
1799     MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1800     assert(mr.start() == old_end, "post-condition");
1801     // mr might be a smaller region than what was requested if
1802     // expand_by() was unable to allocate the HeapRegion instances
1803     assert(mr.end() <= new_end, "post-condition");
1804 
1805     size_t actual_expand_bytes = mr.byte_size();
1806     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1807     assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1808            "post-condition");
1809     if (actual_expand_bytes < aligned_expand_bytes) {
1810       // We could not expand _hrs to the desired size. In this case we
1811       // need to shrink the committed space accordingly.
1812       assert(mr.end() < new_end, "invariant");
1813 
1814       size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1815       // First uncommit the memory.
1816       _g1_storage.shrink_by(diff_bytes);
1817       // Then propagate this update to the necessary data structures.
1818       update_committed_space(new_end, mr.end());
1819     }
1820     _free_list.add_as_tail(&expansion_list);
1821 
1822     if (_hr_printer.is_active()) {
1823       HeapWord* curr = mr.start();
1824       while (curr < mr.end()) {
1825         HeapWord* curr_end = curr + HeapRegion::GrainWords;
1826         _hr_printer.commit(curr, curr_end);
1827         curr = curr_end;
1828       }
1829       assert(curr == mr.end(), "post-condition");
1830     }
1831     g1_policy()->record_new_heap_size(n_regions());
1832   } else {
1833     ergo_verbose0(ErgoHeapSizing,
1834                   "did not expand the heap",
1835                   ergo_format_reason("heap expansion operation failed"));
1836     // The expansion of the virtual storage space was unsuccessful.
1837     // Let's see if it was because we ran out of swap.
1838     if (G1ExitOnExpansionFailure &&
1839         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1840       // We had head room...
1841       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1842     }
1843   }
1844   return successful;
1845 }
1846 
1847 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1848   size_t aligned_shrink_bytes =
1849     ReservedSpace::page_align_size_down(shrink_bytes);
1850   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1851                                          HeapRegion::GrainBytes);
1852   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1853 
1854   uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1855   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1856   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1857 
1858   ergo_verbose3(ErgoHeapSizing,
1859                 "shrink the heap",
1860                 ergo_format_byte("requested shrinking amount")
1861                 ergo_format_byte("aligned shrinking amount")
1862                 ergo_format_byte("attempted shrinking amount"),
1863                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1864   if (num_regions_removed > 0) {
1865     _g1_storage.shrink_by(shrunk_bytes);
1866     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1867 
1868     if (_hr_printer.is_active()) {
1869       HeapWord* curr = old_end;
1870       while (curr > new_end) {
1871         HeapWord* curr_end = curr;
1872         curr -= HeapRegion::GrainWords;
1873         _hr_printer.uncommit(curr, curr_end);
1874       }
1875     }
1876 
1877     _expansion_regions += num_regions_removed;
1878     update_committed_space(old_end, new_end);
1879     HeapRegionRemSet::shrink_heap(n_regions());
1880     g1_policy()->record_new_heap_size(n_regions());
1881   } else {
1882     ergo_verbose0(ErgoHeapSizing,
1883                   "did not shrink the heap",
1884                   ergo_format_reason("heap shrinking operation failed"));
1885   }
1886 }
1887 
1888 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1889   verify_region_sets_optional();
1890 
1891   // We should only reach here at the end of a Full GC which means we
1892   // should not not be holding to any GC alloc regions. The method
1893   // below will make sure of that and do any remaining clean up.
1894   abandon_gc_alloc_regions();
1895 
1896   // Instead of tearing down / rebuilding the free lists here, we
1897   // could instead use the remove_all_pending() method on free_list to
1898   // remove only the ones that we need to remove.
1899   tear_down_region_sets(true /* free_list_only */);
1900   shrink_helper(shrink_bytes);
1901   rebuild_region_sets(true /* free_list_only */);
1902 
1903   _hrs.verify_optional();
1904   verify_region_sets_optional();
1905 }
1906 
1907 // Public methods.
1908 
1909 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1910 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1911 #endif // _MSC_VER
1912 
1913 
1914 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1915   SharedHeap(policy_),
1916   _g1_policy(policy_),
1917   _dirty_card_queue_set(false),
1918   _into_cset_dirty_card_queue_set(false),
1919   _is_alive_closure_cm(this),
1920   _is_alive_closure_stw(this),
1921   _ref_processor_cm(NULL),
1922   _ref_processor_stw(NULL),
1923   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1924   _bot_shared(NULL),
1925   _evac_failure_scan_stack(NULL),
1926   _mark_in_progress(false),
1927   _cg1r(NULL), _summary_bytes_used(0),
1928   _g1mm(NULL),
1929   _refine_cte_cl(NULL),
1930   _full_collection(false),
1931   _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()),
1932   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1933   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1934   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1935   _free_regions_coming(false),
1936   _young_list(new YoungList(this)),
1937   _gc_time_stamp(0),
1938   _retained_old_gc_alloc_region(NULL),
1939   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1940   _old_plab_stats(OldPLABSize, PLABWeight),
1941   _expand_heap_after_alloc_failure(true),
1942   _surviving_young_words(NULL),
1943   _old_marking_cycles_started(0),
1944   _old_marking_cycles_completed(0),
1945   _concurrent_cycle_started(false),
1946   _in_cset_fast_test(),
1947   _dirty_cards_region_list(NULL),
1948   _worker_cset_start_region(NULL),
1949   _worker_cset_start_region_time_stamp(NULL),
1950   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1951   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1952   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1953   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1954 
1955   _g1h = this;
1956   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1957     vm_exit_during_initialization("Failed necessary allocation.");
1958   }
1959 
1960   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1961 
1962   int n_queues = MAX2((int)ParallelGCThreads, 1);
1963   _task_queues = new RefToScanQueueSet(n_queues);
1964 
1965   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1966   assert(n_rem_sets > 0, "Invariant.");
1967 
1968   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1969   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1970   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1971 
1972   for (int i = 0; i < n_queues; i++) {
1973     RefToScanQueue* q = new RefToScanQueue();
1974     q->initialize();
1975     _task_queues->register_queue(i, q);
1976     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1977   }
1978   clear_cset_start_regions();
1979 
1980   // Initialize the G1EvacuationFailureALot counters and flags.
1981   NOT_PRODUCT(reset_evacuation_should_fail();)
1982 
1983   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1984 }
1985 
1986 jint G1CollectedHeap::initialize() {
1987   CollectedHeap::pre_initialize();
1988   os::enable_vtime();
1989 
1990   G1Log::init();
1991 
1992   // Necessary to satisfy locking discipline assertions.
1993 
1994   MutexLocker x(Heap_lock);
1995 
1996   // We have to initialize the printer before committing the heap, as
1997   // it will be used then.
1998   _hr_printer.set_active(G1PrintHeapRegions);
1999 
2000   // While there are no constraints in the GC code that HeapWordSize
2001   // be any particular value, there are multiple other areas in the
2002   // system which believe this to be true (e.g. oop->object_size in some
2003   // cases incorrectly returns the size in wordSize units rather than
2004   // HeapWordSize).
2005   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2006 
2007   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2008   size_t max_byte_size = collector_policy()->max_heap_byte_size();
2009   size_t heap_alignment = collector_policy()->heap_alignment();
2010 
2011   // Ensure that the sizes are properly aligned.
2012   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2013   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2014   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
2015 
2016   _refine_cte_cl = new RefineCardTableEntryClosure();
2017 
2018   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
2019 
2020   // Reserve the maximum.
2021 
2022   // When compressed oops are enabled, the preferred heap base
2023   // is calculated by subtracting the requested size from the
2024   // 32Gb boundary and using the result as the base address for
2025   // heap reservation. If the requested size is not aligned to
2026   // HeapRegion::GrainBytes (i.e. the alignment that is passed
2027   // into the ReservedHeapSpace constructor) then the actual
2028   // base of the reserved heap may end up differing from the
2029   // address that was requested (i.e. the preferred heap base).
2030   // If this happens then we could end up using a non-optimal
2031   // compressed oops mode.
2032 
2033   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2034                                                  heap_alignment);
2035 
2036   // It is important to do this in a way such that concurrent readers can't
2037   // temporarily think something is in the heap.  (I've actually seen this
2038   // happen in asserts: DLD.)
2039   _reserved.set_word_size(0);
2040   _reserved.set_start((HeapWord*)heap_rs.base());
2041   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2042 
2043   _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2044 
2045   // Create the gen rem set (and barrier set) for the entire reserved region.
2046   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2047   set_barrier_set(rem_set()->bs());
2048   if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
2049     vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
2050     return JNI_ENOMEM;
2051   }
2052 
2053   // Also create a G1 rem set.
2054   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
2055 
2056   // Carve out the G1 part of the heap.
2057 
2058   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
2059   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2060                            g1_rs.size()/HeapWordSize);
2061 
2062   _g1_storage.initialize(g1_rs, 0);
2063   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2064   _hrs.initialize((HeapWord*) _g1_reserved.start(),
2065                   (HeapWord*) _g1_reserved.end());
2066   assert(_hrs.max_length() == _expansion_regions,
2067          err_msg("max length: %u expansion regions: %u",
2068                  _hrs.max_length(), _expansion_regions));
2069 
2070   // Do later initialization work for concurrent refinement.
2071   _cg1r->init();
2072 
2073   // 6843694 - ensure that the maximum region index can fit
2074   // in the remembered set structures.
2075   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2076   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2077 
2078   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2079   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2080   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2081             "too many cards per region");
2082 
2083   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2084 
2085   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2086                                              heap_word_size(init_byte_size));
2087 
2088   _g1h = this;
2089 
2090   _in_cset_fast_test.initialize(_g1_reserved.start(), _g1_reserved.end(), HeapRegion::GrainBytes);
2091 
2092   // Create the ConcurrentMark data structure and thread.
2093   // (Must do this late, so that "max_regions" is defined.)
2094   _cm = new ConcurrentMark(this, heap_rs);
2095   if (_cm == NULL || !_cm->completed_initialization()) {
2096     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2097     return JNI_ENOMEM;
2098   }
2099   _cmThread = _cm->cmThread();
2100 
2101   // Initialize the from_card cache structure of HeapRegionRemSet.
2102   HeapRegionRemSet::init_heap(max_regions());
2103 
2104   // Now expand into the initial heap size.
2105   if (!expand(init_byte_size)) {
2106     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2107     return JNI_ENOMEM;
2108   }
2109 
2110   // Perform any initialization actions delegated to the policy.
2111   g1_policy()->init();
2112 
2113   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2114                                                SATB_Q_FL_lock,
2115                                                G1SATBProcessCompletedThreshold,
2116                                                Shared_SATB_Q_lock);
2117 
2118   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2119                                                 DirtyCardQ_CBL_mon,
2120                                                 DirtyCardQ_FL_lock,
2121                                                 concurrent_g1_refine()->yellow_zone(),
2122                                                 concurrent_g1_refine()->red_zone(),
2123                                                 Shared_DirtyCardQ_lock);
2124 
2125   if (G1DeferredRSUpdate) {
2126     dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2127                                       DirtyCardQ_CBL_mon,
2128                                       DirtyCardQ_FL_lock,
2129                                       -1, // never trigger processing
2130                                       -1, // no limit on length
2131                                       Shared_DirtyCardQ_lock,
2132                                       &JavaThread::dirty_card_queue_set());
2133   }
2134 
2135   // Initialize the card queue set used to hold cards containing
2136   // references into the collection set.
2137   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2138                                              DirtyCardQ_CBL_mon,
2139                                              DirtyCardQ_FL_lock,
2140                                              -1, // never trigger processing
2141                                              -1, // no limit on length
2142                                              Shared_DirtyCardQ_lock,
2143                                              &JavaThread::dirty_card_queue_set());
2144 
2145   // In case we're keeping closure specialization stats, initialize those
2146   // counts and that mechanism.
2147   SpecializationStats::clear();
2148 
2149   // Here we allocate the dummy full region that is required by the
2150   // G1AllocRegion class. If we don't pass an address in the reserved
2151   // space here, lots of asserts fire.
2152 
2153   HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2154                                              _g1_reserved.start());
2155   // We'll re-use the same region whether the alloc region will
2156   // require BOT updates or not and, if it doesn't, then a non-young
2157   // region will complain that it cannot support allocations without
2158   // BOT updates. So we'll tag the dummy region as young to avoid that.
2159   dummy_region->set_young();
2160   // Make sure it's full.
2161   dummy_region->set_top(dummy_region->end());
2162   G1AllocRegion::setup(this, dummy_region);
2163 
2164   init_mutator_alloc_region();
2165 
2166   // Do create of the monitoring and management support so that
2167   // values in the heap have been properly initialized.
2168   _g1mm = new G1MonitoringSupport(this);
2169 
2170   G1StringDedup::initialize();
2171 
2172   return JNI_OK;
2173 }
2174 
2175 void G1CollectedHeap::stop() {
2176 #if 0
2177   // Stopping concurrent worker threads is currently disabled until
2178   // some bugs in concurrent mark has been resolve. Without fixing
2179   // those bugs first we risk haning during VM exit when trying to
2180   // stop these threads.
2181 
2182   // Abort any ongoing concurrent root region scanning and stop all
2183   // concurrent threads. We do this to make sure these threads do
2184   // not continue to execute and access resources (e.g. gclog_or_tty)
2185   // that are destroyed during shutdown.
2186   _cm->root_regions()->abort();
2187   _cm->root_regions()->wait_until_scan_finished();
2188   stop_conc_gc_threads();
2189 #endif
2190 }
2191 
2192 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2193   return HeapRegion::max_region_size();
2194 }
2195 
2196 void G1CollectedHeap::ref_processing_init() {
2197   // Reference processing in G1 currently works as follows:
2198   //
2199   // * There are two reference processor instances. One is
2200   //   used to record and process discovered references
2201   //   during concurrent marking; the other is used to
2202   //   record and process references during STW pauses
2203   //   (both full and incremental).
2204   // * Both ref processors need to 'span' the entire heap as
2205   //   the regions in the collection set may be dotted around.
2206   //
2207   // * For the concurrent marking ref processor:
2208   //   * Reference discovery is enabled at initial marking.
2209   //   * Reference discovery is disabled and the discovered
2210   //     references processed etc during remarking.
2211   //   * Reference discovery is MT (see below).
2212   //   * Reference discovery requires a barrier (see below).
2213   //   * Reference processing may or may not be MT
2214   //     (depending on the value of ParallelRefProcEnabled
2215   //     and ParallelGCThreads).
2216   //   * A full GC disables reference discovery by the CM
2217   //     ref processor and abandons any entries on it's
2218   //     discovered lists.
2219   //
2220   // * For the STW processor:
2221   //   * Non MT discovery is enabled at the start of a full GC.
2222   //   * Processing and enqueueing during a full GC is non-MT.
2223   //   * During a full GC, references are processed after marking.
2224   //
2225   //   * Discovery (may or may not be MT) is enabled at the start
2226   //     of an incremental evacuation pause.
2227   //   * References are processed near the end of a STW evacuation pause.
2228   //   * For both types of GC:
2229   //     * Discovery is atomic - i.e. not concurrent.
2230   //     * Reference discovery will not need a barrier.
2231 
2232   SharedHeap::ref_processing_init();
2233   MemRegion mr = reserved_region();
2234 
2235   // Concurrent Mark ref processor
2236   _ref_processor_cm =
2237     new ReferenceProcessor(mr,    // span
2238                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2239                                 // mt processing
2240                            (int) ParallelGCThreads,
2241                                 // degree of mt processing
2242                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2243                                 // mt discovery
2244                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2245                                 // degree of mt discovery
2246                            false,
2247                                 // Reference discovery is not atomic
2248                            &_is_alive_closure_cm);
2249                                 // is alive closure
2250                                 // (for efficiency/performance)
2251 
2252   // STW ref processor
2253   _ref_processor_stw =
2254     new ReferenceProcessor(mr,    // span
2255                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2256                                 // mt processing
2257                            MAX2((int)ParallelGCThreads, 1),
2258                                 // degree of mt processing
2259                            (ParallelGCThreads > 1),
2260                                 // mt discovery
2261                            MAX2((int)ParallelGCThreads, 1),
2262                                 // degree of mt discovery
2263                            true,
2264                                 // Reference discovery is atomic
2265                            &_is_alive_closure_stw);
2266                                 // is alive closure
2267                                 // (for efficiency/performance)
2268 }
2269 
2270 size_t G1CollectedHeap::capacity() const {
2271   return _g1_committed.byte_size();
2272 }
2273 
2274 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2275   assert(!hr->continuesHumongous(), "pre-condition");
2276   hr->reset_gc_time_stamp();
2277   if (hr->startsHumongous()) {
2278     uint first_index = hr->hrs_index() + 1;
2279     uint last_index = hr->last_hc_index();
2280     for (uint i = first_index; i < last_index; i += 1) {
2281       HeapRegion* chr = region_at(i);
2282       assert(chr->continuesHumongous(), "sanity");
2283       chr->reset_gc_time_stamp();
2284     }
2285   }
2286 }
2287 
2288 #ifndef PRODUCT
2289 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2290 private:
2291   unsigned _gc_time_stamp;
2292   bool _failures;
2293 
2294 public:
2295   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2296     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2297 
2298   virtual bool doHeapRegion(HeapRegion* hr) {
2299     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2300     if (_gc_time_stamp != region_gc_time_stamp) {
2301       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2302                              "expected %d", HR_FORMAT_PARAMS(hr),
2303                              region_gc_time_stamp, _gc_time_stamp);
2304       _failures = true;
2305     }
2306     return false;
2307   }
2308 
2309   bool failures() { return _failures; }
2310 };
2311 
2312 void G1CollectedHeap::check_gc_time_stamps() {
2313   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2314   heap_region_iterate(&cl);
2315   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2316 }
2317 #endif // PRODUCT
2318 
2319 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2320                                                  DirtyCardQueue* into_cset_dcq,
2321                                                  bool concurrent,
2322                                                  uint worker_i) {
2323   // Clean cards in the hot card cache
2324   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2325   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2326 
2327   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2328   int n_completed_buffers = 0;
2329   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2330     n_completed_buffers++;
2331   }
2332   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2333   dcqs.clear_n_completed_buffers();
2334   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2335 }
2336 
2337 
2338 // Computes the sum of the storage used by the various regions.
2339 
2340 size_t G1CollectedHeap::used() const {
2341   assert(Heap_lock->owner() != NULL,
2342          "Should be owned on this thread's behalf.");
2343   size_t result = _summary_bytes_used;
2344   // Read only once in case it is set to NULL concurrently
2345   HeapRegion* hr = _mutator_alloc_region.get();
2346   if (hr != NULL)
2347     result += hr->used();
2348   return result;
2349 }
2350 
2351 size_t G1CollectedHeap::used_unlocked() const {
2352   size_t result = _summary_bytes_used;
2353   return result;
2354 }
2355 
2356 class SumUsedClosure: public HeapRegionClosure {
2357   size_t _used;
2358 public:
2359   SumUsedClosure() : _used(0) {}
2360   bool doHeapRegion(HeapRegion* r) {
2361     if (!r->continuesHumongous()) {
2362       _used += r->used();
2363     }
2364     return false;
2365   }
2366   size_t result() { return _used; }
2367 };
2368 
2369 size_t G1CollectedHeap::recalculate_used() const {
2370   double recalculate_used_start = os::elapsedTime();
2371 
2372   SumUsedClosure blk;
2373   heap_region_iterate(&blk);
2374 
2375   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2376   return blk.result();
2377 }
2378 
2379 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2380   switch (cause) {
2381     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2382     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2383     case GCCause::_g1_humongous_allocation: return true;
2384     default:                                return false;
2385   }
2386 }
2387 
2388 #ifndef PRODUCT
2389 void G1CollectedHeap::allocate_dummy_regions() {
2390   // Let's fill up most of the region
2391   size_t word_size = HeapRegion::GrainWords - 1024;
2392   // And as a result the region we'll allocate will be humongous.
2393   guarantee(isHumongous(word_size), "sanity");
2394 
2395   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2396     // Let's use the existing mechanism for the allocation
2397     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2398     if (dummy_obj != NULL) {
2399       MemRegion mr(dummy_obj, word_size);
2400       CollectedHeap::fill_with_object(mr);
2401     } else {
2402       // If we can't allocate once, we probably cannot allocate
2403       // again. Let's get out of the loop.
2404       break;
2405     }
2406   }
2407 }
2408 #endif // !PRODUCT
2409 
2410 void G1CollectedHeap::increment_old_marking_cycles_started() {
2411   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2412     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2413     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2414     _old_marking_cycles_started, _old_marking_cycles_completed));
2415 
2416   _old_marking_cycles_started++;
2417 }
2418 
2419 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2420   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2421 
2422   // We assume that if concurrent == true, then the caller is a
2423   // concurrent thread that was joined the Suspendible Thread
2424   // Set. If there's ever a cheap way to check this, we should add an
2425   // assert here.
2426 
2427   // Given that this method is called at the end of a Full GC or of a
2428   // concurrent cycle, and those can be nested (i.e., a Full GC can
2429   // interrupt a concurrent cycle), the number of full collections
2430   // completed should be either one (in the case where there was no
2431   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2432   // behind the number of full collections started.
2433 
2434   // This is the case for the inner caller, i.e. a Full GC.
2435   assert(concurrent ||
2436          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2437          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2438          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2439                  "is inconsistent with _old_marking_cycles_completed = %u",
2440                  _old_marking_cycles_started, _old_marking_cycles_completed));
2441 
2442   // This is the case for the outer caller, i.e. the concurrent cycle.
2443   assert(!concurrent ||
2444          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2445          err_msg("for outer caller (concurrent cycle): "
2446                  "_old_marking_cycles_started = %u "
2447                  "is inconsistent with _old_marking_cycles_completed = %u",
2448                  _old_marking_cycles_started, _old_marking_cycles_completed));
2449 
2450   _old_marking_cycles_completed += 1;
2451 
2452   // We need to clear the "in_progress" flag in the CM thread before
2453   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2454   // is set) so that if a waiter requests another System.gc() it doesn't
2455   // incorrectly see that a marking cycle is still in progress.
2456   if (concurrent) {
2457     _cmThread->clear_in_progress();
2458   }
2459 
2460   // This notify_all() will ensure that a thread that called
2461   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2462   // and it's waiting for a full GC to finish will be woken up. It is
2463   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2464   FullGCCount_lock->notify_all();
2465 }
2466 
2467 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2468   _concurrent_cycle_started = true;
2469   _gc_timer_cm->register_gc_start(start_time);
2470 
2471   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2472   trace_heap_before_gc(_gc_tracer_cm);
2473 }
2474 
2475 void G1CollectedHeap::register_concurrent_cycle_end() {
2476   if (_concurrent_cycle_started) {
2477     if (_cm->has_aborted()) {
2478       _gc_tracer_cm->report_concurrent_mode_failure();
2479     }
2480 
2481     _gc_timer_cm->register_gc_end();
2482     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2483 
2484     _concurrent_cycle_started = false;
2485   }
2486 }
2487 
2488 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2489   if (_concurrent_cycle_started) {
2490     trace_heap_after_gc(_gc_tracer_cm);
2491   }
2492 }
2493 
2494 G1YCType G1CollectedHeap::yc_type() {
2495   bool is_young = g1_policy()->gcs_are_young();
2496   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2497   bool is_during_mark = mark_in_progress();
2498 
2499   if (is_initial_mark) {
2500     return InitialMark;
2501   } else if (is_during_mark) {
2502     return DuringMark;
2503   } else if (is_young) {
2504     return Normal;
2505   } else {
2506     return Mixed;
2507   }
2508 }
2509 
2510 void G1CollectedHeap::collect(GCCause::Cause cause) {
2511   assert_heap_not_locked();
2512 
2513   unsigned int gc_count_before;
2514   unsigned int old_marking_count_before;
2515   bool retry_gc;
2516 
2517   do {
2518     retry_gc = false;
2519 
2520     {
2521       MutexLocker ml(Heap_lock);
2522 
2523       // Read the GC count while holding the Heap_lock
2524       gc_count_before = total_collections();
2525       old_marking_count_before = _old_marking_cycles_started;
2526     }
2527 
2528     if (should_do_concurrent_full_gc(cause)) {
2529       // Schedule an initial-mark evacuation pause that will start a
2530       // concurrent cycle. We're setting word_size to 0 which means that
2531       // we are not requesting a post-GC allocation.
2532       VM_G1IncCollectionPause op(gc_count_before,
2533                                  0,     /* word_size */
2534                                  true,  /* should_initiate_conc_mark */
2535                                  g1_policy()->max_pause_time_ms(),
2536                                  cause);
2537 
2538       VMThread::execute(&op);
2539       if (!op.pause_succeeded()) {
2540         if (old_marking_count_before == _old_marking_cycles_started) {
2541           retry_gc = op.should_retry_gc();
2542         } else {
2543           // A Full GC happened while we were trying to schedule the
2544           // initial-mark GC. No point in starting a new cycle given
2545           // that the whole heap was collected anyway.
2546         }
2547 
2548         if (retry_gc) {
2549           if (GC_locker::is_active_and_needs_gc()) {
2550             GC_locker::stall_until_clear();
2551           }
2552         }
2553       }
2554     } else {
2555       if (cause == GCCause::_gc_locker
2556           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2557 
2558         // Schedule a standard evacuation pause. We're setting word_size
2559         // to 0 which means that we are not requesting a post-GC allocation.
2560         VM_G1IncCollectionPause op(gc_count_before,
2561                                    0,     /* word_size */
2562                                    false, /* should_initiate_conc_mark */
2563                                    g1_policy()->max_pause_time_ms(),
2564                                    cause);
2565         VMThread::execute(&op);
2566       } else {
2567         // Schedule a Full GC.
2568         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2569         VMThread::execute(&op);
2570       }
2571     }
2572   } while (retry_gc);
2573 }
2574 
2575 bool G1CollectedHeap::is_in(const void* p) const {
2576   if (_g1_committed.contains(p)) {
2577     // Given that we know that p is in the committed space,
2578     // heap_region_containing_raw() should successfully
2579     // return the containing region.
2580     HeapRegion* hr = heap_region_containing_raw(p);
2581     return hr->is_in(p);
2582   } else {
2583     return false;
2584   }
2585 }
2586 
2587 // Iteration functions.
2588 
2589 // Iterates an OopClosure over all ref-containing fields of objects
2590 // within a HeapRegion.
2591 
2592 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2593   MemRegion _mr;
2594   ExtendedOopClosure* _cl;
2595 public:
2596   IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2597     : _mr(mr), _cl(cl) {}
2598   bool doHeapRegion(HeapRegion* r) {
2599     if (!r->continuesHumongous()) {
2600       r->oop_iterate(_cl);
2601     }
2602     return false;
2603   }
2604 };
2605 
2606 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2607   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2608   heap_region_iterate(&blk);
2609 }
2610 
2611 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2612   IterateOopClosureRegionClosure blk(mr, cl);
2613   heap_region_iterate(&blk);
2614 }
2615 
2616 // Iterates an ObjectClosure over all objects within a HeapRegion.
2617 
2618 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2619   ObjectClosure* _cl;
2620 public:
2621   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2622   bool doHeapRegion(HeapRegion* r) {
2623     if (! r->continuesHumongous()) {
2624       r->object_iterate(_cl);
2625     }
2626     return false;
2627   }
2628 };
2629 
2630 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2631   IterateObjectClosureRegionClosure blk(cl);
2632   heap_region_iterate(&blk);
2633 }
2634 
2635 // Calls a SpaceClosure on a HeapRegion.
2636 
2637 class SpaceClosureRegionClosure: public HeapRegionClosure {
2638   SpaceClosure* _cl;
2639 public:
2640   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2641   bool doHeapRegion(HeapRegion* r) {
2642     _cl->do_space(r);
2643     return false;
2644   }
2645 };
2646 
2647 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2648   SpaceClosureRegionClosure blk(cl);
2649   heap_region_iterate(&blk);
2650 }
2651 
2652 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2653   _hrs.iterate(cl);
2654 }
2655 
2656 void
2657 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2658                                                  uint worker_id,
2659                                                  uint no_of_par_workers,
2660                                                  jint claim_value) {
2661   const uint regions = n_regions();
2662   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2663                              no_of_par_workers :
2664                              1);
2665   assert(UseDynamicNumberOfGCThreads ||
2666          no_of_par_workers == workers()->total_workers(),
2667          "Non dynamic should use fixed number of workers");
2668   // try to spread out the starting points of the workers
2669   const HeapRegion* start_hr =
2670                         start_region_for_worker(worker_id, no_of_par_workers);
2671   const uint start_index = start_hr->hrs_index();
2672 
2673   // each worker will actually look at all regions
2674   for (uint count = 0; count < regions; ++count) {
2675     const uint index = (start_index + count) % regions;
2676     assert(0 <= index && index < regions, "sanity");
2677     HeapRegion* r = region_at(index);
2678     // we'll ignore "continues humongous" regions (we'll process them
2679     // when we come across their corresponding "start humongous"
2680     // region) and regions already claimed
2681     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2682       continue;
2683     }
2684     // OK, try to claim it
2685     if (r->claimHeapRegion(claim_value)) {
2686       // success!
2687       assert(!r->continuesHumongous(), "sanity");
2688       if (r->startsHumongous()) {
2689         // If the region is "starts humongous" we'll iterate over its
2690         // "continues humongous" first; in fact we'll do them
2691         // first. The order is important. In on case, calling the
2692         // closure on the "starts humongous" region might de-allocate
2693         // and clear all its "continues humongous" regions and, as a
2694         // result, we might end up processing them twice. So, we'll do
2695         // them first (notice: most closures will ignore them anyway) and
2696         // then we'll do the "starts humongous" region.
2697         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2698           HeapRegion* chr = region_at(ch_index);
2699 
2700           // if the region has already been claimed or it's not
2701           // "continues humongous" we're done
2702           if (chr->claim_value() == claim_value ||
2703               !chr->continuesHumongous()) {
2704             break;
2705           }
2706 
2707           // No one should have claimed it directly. We can given
2708           // that we claimed its "starts humongous" region.
2709           assert(chr->claim_value() != claim_value, "sanity");
2710           assert(chr->humongous_start_region() == r, "sanity");
2711 
2712           if (chr->claimHeapRegion(claim_value)) {
2713             // we should always be able to claim it; no one else should
2714             // be trying to claim this region
2715 
2716             bool res2 = cl->doHeapRegion(chr);
2717             assert(!res2, "Should not abort");
2718 
2719             // Right now, this holds (i.e., no closure that actually
2720             // does something with "continues humongous" regions
2721             // clears them). We might have to weaken it in the future,
2722             // but let's leave these two asserts here for extra safety.
2723             assert(chr->continuesHumongous(), "should still be the case");
2724             assert(chr->humongous_start_region() == r, "sanity");
2725           } else {
2726             guarantee(false, "we should not reach here");
2727           }
2728         }
2729       }
2730 
2731       assert(!r->continuesHumongous(), "sanity");
2732       bool res = cl->doHeapRegion(r);
2733       assert(!res, "Should not abort");
2734     }
2735   }
2736 }
2737 
2738 class ResetClaimValuesClosure: public HeapRegionClosure {
2739 public:
2740   bool doHeapRegion(HeapRegion* r) {
2741     r->set_claim_value(HeapRegion::InitialClaimValue);
2742     return false;
2743   }
2744 };
2745 
2746 void G1CollectedHeap::reset_heap_region_claim_values() {
2747   ResetClaimValuesClosure blk;
2748   heap_region_iterate(&blk);
2749 }
2750 
2751 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2752   ResetClaimValuesClosure blk;
2753   collection_set_iterate(&blk);
2754 }
2755 
2756 #ifdef ASSERT
2757 // This checks whether all regions in the heap have the correct claim
2758 // value. I also piggy-backed on this a check to ensure that the
2759 // humongous_start_region() information on "continues humongous"
2760 // regions is correct.
2761 
2762 class CheckClaimValuesClosure : public HeapRegionClosure {
2763 private:
2764   jint _claim_value;
2765   uint _failures;
2766   HeapRegion* _sh_region;
2767 
2768 public:
2769   CheckClaimValuesClosure(jint claim_value) :
2770     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2771   bool doHeapRegion(HeapRegion* r) {
2772     if (r->claim_value() != _claim_value) {
2773       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2774                              "claim value = %d, should be %d",
2775                              HR_FORMAT_PARAMS(r),
2776                              r->claim_value(), _claim_value);
2777       ++_failures;
2778     }
2779     if (!r->isHumongous()) {
2780       _sh_region = NULL;
2781     } else if (r->startsHumongous()) {
2782       _sh_region = r;
2783     } else if (r->continuesHumongous()) {
2784       if (r->humongous_start_region() != _sh_region) {
2785         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2786                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2787                                HR_FORMAT_PARAMS(r),
2788                                r->humongous_start_region(),
2789                                _sh_region);
2790         ++_failures;
2791       }
2792     }
2793     return false;
2794   }
2795   uint failures() { return _failures; }
2796 };
2797 
2798 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2799   CheckClaimValuesClosure cl(claim_value);
2800   heap_region_iterate(&cl);
2801   return cl.failures() == 0;
2802 }
2803 
2804 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2805 private:
2806   jint _claim_value;
2807   uint _failures;
2808 
2809 public:
2810   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2811     _claim_value(claim_value), _failures(0) { }
2812 
2813   uint failures() { return _failures; }
2814 
2815   bool doHeapRegion(HeapRegion* hr) {
2816     assert(hr->in_collection_set(), "how?");
2817     assert(!hr->isHumongous(), "H-region in CSet");
2818     if (hr->claim_value() != _claim_value) {
2819       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2820                              "claim value = %d, should be %d",
2821                              HR_FORMAT_PARAMS(hr),
2822                              hr->claim_value(), _claim_value);
2823       _failures += 1;
2824     }
2825     return false;
2826   }
2827 };
2828 
2829 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2830   CheckClaimValuesInCSetHRClosure cl(claim_value);
2831   collection_set_iterate(&cl);
2832   return cl.failures() == 0;
2833 }
2834 #endif // ASSERT
2835 
2836 // Clear the cached CSet starting regions and (more importantly)
2837 // the time stamps. Called when we reset the GC time stamp.
2838 void G1CollectedHeap::clear_cset_start_regions() {
2839   assert(_worker_cset_start_region != NULL, "sanity");
2840   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2841 
2842   int n_queues = MAX2((int)ParallelGCThreads, 1);
2843   for (int i = 0; i < n_queues; i++) {
2844     _worker_cset_start_region[i] = NULL;
2845     _worker_cset_start_region_time_stamp[i] = 0;
2846   }
2847 }
2848 
2849 // Given the id of a worker, obtain or calculate a suitable
2850 // starting region for iterating over the current collection set.
2851 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2852   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2853 
2854   HeapRegion* result = NULL;
2855   unsigned gc_time_stamp = get_gc_time_stamp();
2856 
2857   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2858     // Cached starting region for current worker was set
2859     // during the current pause - so it's valid.
2860     // Note: the cached starting heap region may be NULL
2861     // (when the collection set is empty).
2862     result = _worker_cset_start_region[worker_i];
2863     assert(result == NULL || result->in_collection_set(), "sanity");
2864     return result;
2865   }
2866 
2867   // The cached entry was not valid so let's calculate
2868   // a suitable starting heap region for this worker.
2869 
2870   // We want the parallel threads to start their collection
2871   // set iteration at different collection set regions to
2872   // avoid contention.
2873   // If we have:
2874   //          n collection set regions
2875   //          p threads
2876   // Then thread t will start at region floor ((t * n) / p)
2877 
2878   result = g1_policy()->collection_set();
2879   if (G1CollectedHeap::use_parallel_gc_threads()) {
2880     uint cs_size = g1_policy()->cset_region_length();
2881     uint active_workers = workers()->active_workers();
2882     assert(UseDynamicNumberOfGCThreads ||
2883              active_workers == workers()->total_workers(),
2884              "Unless dynamic should use total workers");
2885 
2886     uint end_ind   = (cs_size * worker_i) / active_workers;
2887     uint start_ind = 0;
2888 
2889     if (worker_i > 0 &&
2890         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2891       // Previous workers starting region is valid
2892       // so let's iterate from there
2893       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2894       result = _worker_cset_start_region[worker_i - 1];
2895     }
2896 
2897     for (uint i = start_ind; i < end_ind; i++) {
2898       result = result->next_in_collection_set();
2899     }
2900   }
2901 
2902   // Note: the calculated starting heap region may be NULL
2903   // (when the collection set is empty).
2904   assert(result == NULL || result->in_collection_set(), "sanity");
2905   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2906          "should be updated only once per pause");
2907   _worker_cset_start_region[worker_i] = result;
2908   OrderAccess::storestore();
2909   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2910   return result;
2911 }
2912 
2913 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2914                                                      uint no_of_par_workers) {
2915   uint worker_num =
2916            G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2917   assert(UseDynamicNumberOfGCThreads ||
2918          no_of_par_workers == workers()->total_workers(),
2919          "Non dynamic should use fixed number of workers");
2920   const uint start_index = n_regions() * worker_i / worker_num;
2921   return region_at(start_index);
2922 }
2923 
2924 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2925   HeapRegion* r = g1_policy()->collection_set();
2926   while (r != NULL) {
2927     HeapRegion* next = r->next_in_collection_set();
2928     if (cl->doHeapRegion(r)) {
2929       cl->incomplete();
2930       return;
2931     }
2932     r = next;
2933   }
2934 }
2935 
2936 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2937                                                   HeapRegionClosure *cl) {
2938   if (r == NULL) {
2939     // The CSet is empty so there's nothing to do.
2940     return;
2941   }
2942 
2943   assert(r->in_collection_set(),
2944          "Start region must be a member of the collection set.");
2945   HeapRegion* cur = r;
2946   while (cur != NULL) {
2947     HeapRegion* next = cur->next_in_collection_set();
2948     if (cl->doHeapRegion(cur) && false) {
2949       cl->incomplete();
2950       return;
2951     }
2952     cur = next;
2953   }
2954   cur = g1_policy()->collection_set();
2955   while (cur != r) {
2956     HeapRegion* next = cur->next_in_collection_set();
2957     if (cl->doHeapRegion(cur) && false) {
2958       cl->incomplete();
2959       return;
2960     }
2961     cur = next;
2962   }
2963 }
2964 
2965 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2966   return n_regions() > 0 ? region_at(0) : NULL;
2967 }
2968 
2969 
2970 Space* G1CollectedHeap::space_containing(const void* addr) const {
2971   return heap_region_containing(addr);
2972 }
2973 
2974 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2975   Space* sp = space_containing(addr);
2976   return sp->block_start(addr);
2977 }
2978 
2979 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2980   Space* sp = space_containing(addr);
2981   return sp->block_size(addr);
2982 }
2983 
2984 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2985   Space* sp = space_containing(addr);
2986   return sp->block_is_obj(addr);
2987 }
2988 
2989 bool G1CollectedHeap::supports_tlab_allocation() const {
2990   return true;
2991 }
2992 
2993 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2994   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2995 }
2996 
2997 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2998   return young_list()->eden_used_bytes();
2999 }
3000 
3001 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
3002 // must be smaller than the humongous object limit.
3003 size_t G1CollectedHeap::max_tlab_size() const {
3004   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
3005 }
3006 
3007 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3008   // Return the remaining space in the cur alloc region, but not less than
3009   // the min TLAB size.
3010 
3011   // Also, this value can be at most the humongous object threshold,
3012   // since we can't allow tlabs to grow big enough to accommodate
3013   // humongous objects.
3014 
3015   HeapRegion* hr = _mutator_alloc_region.get();
3016   size_t max_tlab = max_tlab_size() * wordSize;
3017   if (hr == NULL) {
3018     return max_tlab;
3019   } else {
3020     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3021   }
3022 }
3023 
3024 size_t G1CollectedHeap::max_capacity() const {
3025   return _g1_reserved.byte_size();
3026 }
3027 
3028 jlong G1CollectedHeap::millis_since_last_gc() {
3029   // assert(false, "NYI");
3030   return 0;
3031 }
3032 
3033 void G1CollectedHeap::prepare_for_verify() {
3034   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3035     ensure_parsability(false);
3036   }
3037   g1_rem_set()->prepare_for_verify();
3038 }
3039 
3040 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3041                                               VerifyOption vo) {
3042   switch (vo) {
3043   case VerifyOption_G1UsePrevMarking:
3044     return hr->obj_allocated_since_prev_marking(obj);
3045   case VerifyOption_G1UseNextMarking:
3046     return hr->obj_allocated_since_next_marking(obj);
3047   case VerifyOption_G1UseMarkWord:
3048     return false;
3049   default:
3050     ShouldNotReachHere();
3051   }
3052   return false; // keep some compilers happy
3053 }
3054 
3055 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3056   switch (vo) {
3057   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3058   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3059   case VerifyOption_G1UseMarkWord:    return NULL;
3060   default:                            ShouldNotReachHere();
3061   }
3062   return NULL; // keep some compilers happy
3063 }
3064 
3065 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3066   switch (vo) {
3067   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3068   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3069   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
3070   default:                            ShouldNotReachHere();
3071   }
3072   return false; // keep some compilers happy
3073 }
3074 
3075 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3076   switch (vo) {
3077   case VerifyOption_G1UsePrevMarking: return "PTAMS";
3078   case VerifyOption_G1UseNextMarking: return "NTAMS";
3079   case VerifyOption_G1UseMarkWord:    return "NONE";
3080   default:                            ShouldNotReachHere();
3081   }
3082   return NULL; // keep some compilers happy
3083 }
3084 
3085 class VerifyRootsClosure: public OopClosure {
3086 private:
3087   G1CollectedHeap* _g1h;
3088   VerifyOption     _vo;
3089   bool             _failures;
3090 public:
3091   // _vo == UsePrevMarking -> use "prev" marking information,
3092   // _vo == UseNextMarking -> use "next" marking information,
3093   // _vo == UseMarkWord    -> use mark word from object header.
3094   VerifyRootsClosure(VerifyOption vo) :
3095     _g1h(G1CollectedHeap::heap()),
3096     _vo(vo),
3097     _failures(false) { }
3098 
3099   bool failures() { return _failures; }
3100 
3101   template <class T> void do_oop_nv(T* p) {
3102     T heap_oop = oopDesc::load_heap_oop(p);
3103     if (!oopDesc::is_null(heap_oop)) {
3104       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3105       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3106         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3107                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3108         if (_vo == VerifyOption_G1UseMarkWord) {
3109           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3110         }
3111         obj->print_on(gclog_or_tty);
3112         _failures = true;
3113       }
3114     }
3115   }
3116 
3117   void do_oop(oop* p)       { do_oop_nv(p); }
3118   void do_oop(narrowOop* p) { do_oop_nv(p); }
3119 };
3120 
3121 class G1VerifyCodeRootOopClosure: public OopClosure {
3122   G1CollectedHeap* _g1h;
3123   OopClosure* _root_cl;
3124   nmethod* _nm;
3125   VerifyOption _vo;
3126   bool _failures;
3127 
3128   template <class T> void do_oop_work(T* p) {
3129     // First verify that this root is live
3130     _root_cl->do_oop(p);
3131 
3132     if (!G1VerifyHeapRegionCodeRoots) {
3133       // We're not verifying the code roots attached to heap region.
3134       return;
3135     }
3136 
3137     // Don't check the code roots during marking verification in a full GC
3138     if (_vo == VerifyOption_G1UseMarkWord) {
3139       return;
3140     }
3141 
3142     // Now verify that the current nmethod (which contains p) is
3143     // in the code root list of the heap region containing the
3144     // object referenced by p.
3145 
3146     T heap_oop = oopDesc::load_heap_oop(p);
3147     if (!oopDesc::is_null(heap_oop)) {
3148       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3149 
3150       // Now fetch the region containing the object
3151       HeapRegion* hr = _g1h->heap_region_containing(obj);
3152       HeapRegionRemSet* hrrs = hr->rem_set();
3153       // Verify that the strong code root list for this region
3154       // contains the nmethod
3155       if (!hrrs->strong_code_roots_list_contains(_nm)) {
3156         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3157                               "from nmethod "PTR_FORMAT" not in strong "
3158                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3159                               p, _nm, hr->bottom(), hr->end());
3160         _failures = true;
3161       }
3162     }
3163   }
3164 
3165 public:
3166   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3167     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3168 
3169   void do_oop(oop* p) { do_oop_work(p); }
3170   void do_oop(narrowOop* p) { do_oop_work(p); }
3171 
3172   void set_nmethod(nmethod* nm) { _nm = nm; }
3173   bool failures() { return _failures; }
3174 };
3175 
3176 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3177   G1VerifyCodeRootOopClosure* _oop_cl;
3178 
3179 public:
3180   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3181     _oop_cl(oop_cl) {}
3182 
3183   void do_code_blob(CodeBlob* cb) {
3184     nmethod* nm = cb->as_nmethod_or_null();
3185     if (nm != NULL) {
3186       _oop_cl->set_nmethod(nm);
3187       nm->oops_do(_oop_cl);
3188     }
3189   }
3190 };
3191 
3192 class YoungRefCounterClosure : public OopClosure {
3193   G1CollectedHeap* _g1h;
3194   int              _count;
3195  public:
3196   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3197   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3198   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3199 
3200   int count() { return _count; }
3201   void reset_count() { _count = 0; };
3202 };
3203 
3204 class VerifyKlassClosure: public KlassClosure {
3205   YoungRefCounterClosure _young_ref_counter_closure;
3206   OopClosure *_oop_closure;
3207  public:
3208   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3209   void do_klass(Klass* k) {
3210     k->oops_do(_oop_closure);
3211 
3212     _young_ref_counter_closure.reset_count();
3213     k->oops_do(&_young_ref_counter_closure);
3214     if (_young_ref_counter_closure.count() > 0) {
3215       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3216     }
3217   }
3218 };
3219 
3220 class VerifyLivenessOopClosure: public OopClosure {
3221   G1CollectedHeap* _g1h;
3222   VerifyOption _vo;
3223 public:
3224   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3225     _g1h(g1h), _vo(vo)
3226   { }
3227   void do_oop(narrowOop *p) { do_oop_work(p); }
3228   void do_oop(      oop *p) { do_oop_work(p); }
3229 
3230   template <class T> void do_oop_work(T *p) {
3231     oop obj = oopDesc::load_decode_heap_oop(p);
3232     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3233               "Dead object referenced by a not dead object");
3234   }
3235 };
3236 
3237 class VerifyObjsInRegionClosure: public ObjectClosure {
3238 private:
3239   G1CollectedHeap* _g1h;
3240   size_t _live_bytes;
3241   HeapRegion *_hr;
3242   VerifyOption _vo;
3243 public:
3244   // _vo == UsePrevMarking -> use "prev" marking information,
3245   // _vo == UseNextMarking -> use "next" marking information,
3246   // _vo == UseMarkWord    -> use mark word from object header.
3247   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3248     : _live_bytes(0), _hr(hr), _vo(vo) {
3249     _g1h = G1CollectedHeap::heap();
3250   }
3251   void do_object(oop o) {
3252     VerifyLivenessOopClosure isLive(_g1h, _vo);
3253     assert(o != NULL, "Huh?");
3254     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3255       // If the object is alive according to the mark word,
3256       // then verify that the marking information agrees.
3257       // Note we can't verify the contra-positive of the
3258       // above: if the object is dead (according to the mark
3259       // word), it may not be marked, or may have been marked
3260       // but has since became dead, or may have been allocated
3261       // since the last marking.
3262       if (_vo == VerifyOption_G1UseMarkWord) {
3263         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3264       }
3265 
3266       o->oop_iterate_no_header(&isLive);
3267       if (!_hr->obj_allocated_since_prev_marking(o)) {
3268         size_t obj_size = o->size();    // Make sure we don't overflow
3269         _live_bytes += (obj_size * HeapWordSize);
3270       }
3271     }
3272   }
3273   size_t live_bytes() { return _live_bytes; }
3274 };
3275 
3276 class PrintObjsInRegionClosure : public ObjectClosure {
3277   HeapRegion *_hr;
3278   G1CollectedHeap *_g1;
3279 public:
3280   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3281     _g1 = G1CollectedHeap::heap();
3282   };
3283 
3284   void do_object(oop o) {
3285     if (o != NULL) {
3286       HeapWord *start = (HeapWord *) o;
3287       size_t word_sz = o->size();
3288       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3289                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3290                           (void*) o, word_sz,
3291                           _g1->isMarkedPrev(o),
3292                           _g1->isMarkedNext(o),
3293                           _hr->obj_allocated_since_prev_marking(o));
3294       HeapWord *end = start + word_sz;
3295       HeapWord *cur;
3296       int *val;
3297       for (cur = start; cur < end; cur++) {
3298         val = (int *) cur;
3299         gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3300       }
3301     }
3302   }
3303 };
3304 
3305 class VerifyRegionClosure: public HeapRegionClosure {
3306 private:
3307   bool             _par;
3308   VerifyOption     _vo;
3309   bool             _failures;
3310 public:
3311   // _vo == UsePrevMarking -> use "prev" marking information,
3312   // _vo == UseNextMarking -> use "next" marking information,
3313   // _vo == UseMarkWord    -> use mark word from object header.
3314   VerifyRegionClosure(bool par, VerifyOption vo)
3315     : _par(par),
3316       _vo(vo),
3317       _failures(false) {}
3318 
3319   bool failures() {
3320     return _failures;
3321   }
3322 
3323   bool doHeapRegion(HeapRegion* r) {
3324     if (!r->continuesHumongous()) {
3325       bool failures = false;
3326       r->verify(_vo, &failures);
3327       if (failures) {
3328         _failures = true;
3329       } else {
3330         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3331         r->object_iterate(&not_dead_yet_cl);
3332         if (_vo != VerifyOption_G1UseNextMarking) {
3333           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3334             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3335                                    "max_live_bytes "SIZE_FORMAT" "
3336                                    "< calculated "SIZE_FORMAT,
3337                                    r->bottom(), r->end(),
3338                                    r->max_live_bytes(),
3339                                  not_dead_yet_cl.live_bytes());
3340             _failures = true;
3341           }
3342         } else {
3343           // When vo == UseNextMarking we cannot currently do a sanity
3344           // check on the live bytes as the calculation has not been
3345           // finalized yet.
3346         }
3347       }
3348     }
3349     return false; // stop the region iteration if we hit a failure
3350   }
3351 };
3352 
3353 // This is the task used for parallel verification of the heap regions
3354 
3355 class G1ParVerifyTask: public AbstractGangTask {
3356 private:
3357   G1CollectedHeap* _g1h;
3358   VerifyOption     _vo;
3359   bool             _failures;
3360 
3361 public:
3362   // _vo == UsePrevMarking -> use "prev" marking information,
3363   // _vo == UseNextMarking -> use "next" marking information,
3364   // _vo == UseMarkWord    -> use mark word from object header.
3365   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3366     AbstractGangTask("Parallel verify task"),
3367     _g1h(g1h),
3368     _vo(vo),
3369     _failures(false) { }
3370 
3371   bool failures() {
3372     return _failures;
3373   }
3374 
3375   void work(uint worker_id) {
3376     HandleMark hm;
3377     VerifyRegionClosure blk(true, _vo);
3378     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3379                                           _g1h->workers()->active_workers(),
3380                                           HeapRegion::ParVerifyClaimValue);
3381     if (blk.failures()) {
3382       _failures = true;
3383     }
3384   }
3385 };
3386 
3387 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3388   if (SafepointSynchronize::is_at_safepoint()) {
3389     assert(Thread::current()->is_VM_thread(),
3390            "Expected to be executed serially by the VM thread at this point");
3391 
3392     if (!silent) { gclog_or_tty->print("Roots "); }
3393     VerifyRootsClosure rootsCl(vo);
3394     VerifyKlassClosure klassCl(this, &rootsCl);
3395 
3396     // We apply the relevant closures to all the oops in the
3397     // system dictionary, class loader data graph and the string table.
3398     // Don't verify the code cache here, since it's verified below.
3399     const int so = SO_AllClasses | SO_Strings;
3400 
3401     // Need cleared claim bits for the strong roots processing
3402     ClassLoaderDataGraph::clear_claimed_marks();
3403 
3404     process_strong_roots(true,      // activate StrongRootsScope
3405                          ScanningOption(so),  // roots scanning options
3406                          &rootsCl,
3407                          &klassCl
3408                          );
3409 
3410     // Verify the nmethods in the code cache.
3411     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3412     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3413     CodeCache::blobs_do(&blobsCl);
3414 
3415     bool failures = rootsCl.failures() || codeRootsCl.failures();
3416 
3417     if (vo != VerifyOption_G1UseMarkWord) {
3418       // If we're verifying during a full GC then the region sets
3419       // will have been torn down at the start of the GC. Therefore
3420       // verifying the region sets will fail. So we only verify
3421       // the region sets when not in a full GC.
3422       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3423       verify_region_sets();
3424     }
3425 
3426     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3427     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3428       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3429              "sanity check");
3430 
3431       G1ParVerifyTask task(this, vo);
3432       assert(UseDynamicNumberOfGCThreads ||
3433         workers()->active_workers() == workers()->total_workers(),
3434         "If not dynamic should be using all the workers");
3435       int n_workers = workers()->active_workers();
3436       set_par_threads(n_workers);
3437       workers()->run_task(&task);
3438       set_par_threads(0);
3439       if (task.failures()) {
3440         failures = true;
3441       }
3442 
3443       // Checks that the expected amount of parallel work was done.
3444       // The implication is that n_workers is > 0.
3445       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3446              "sanity check");
3447 
3448       reset_heap_region_claim_values();
3449 
3450       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3451              "sanity check");
3452     } else {
3453       VerifyRegionClosure blk(false, vo);
3454       heap_region_iterate(&blk);
3455       if (blk.failures()) {
3456         failures = true;
3457       }
3458     }
3459     if (!silent) gclog_or_tty->print("RemSet ");
3460     rem_set()->verify();
3461 
3462     if (G1StringDedup::is_enabled()) {
3463       if (!silent) gclog_or_tty->print("StrDedup ");
3464       G1StringDedup::verify();
3465     }
3466 
3467     if (failures) {
3468       gclog_or_tty->print_cr("Heap:");
3469       // It helps to have the per-region information in the output to
3470       // help us track down what went wrong. This is why we call
3471       // print_extended_on() instead of print_on().
3472       print_extended_on(gclog_or_tty);
3473       gclog_or_tty->cr();
3474 #ifndef PRODUCT
3475       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3476         concurrent_mark()->print_reachable("at-verification-failure",
3477                                            vo, false /* all */);
3478       }
3479 #endif
3480       gclog_or_tty->flush();
3481     }
3482     guarantee(!failures, "there should not have been any failures");
3483   } else {
3484     if (!silent) {
3485       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3486       if (G1StringDedup::is_enabled()) {
3487         gclog_or_tty->print(", StrDedup");
3488       }
3489       gclog_or_tty->print(") ");
3490     }
3491   }
3492 }
3493 
3494 void G1CollectedHeap::verify(bool silent) {
3495   verify(silent, VerifyOption_G1UsePrevMarking);
3496 }
3497 
3498 double G1CollectedHeap::verify(bool guard, const char* msg) {
3499   double verify_time_ms = 0.0;
3500 
3501   if (guard && total_collections() >= VerifyGCStartAt) {
3502     double verify_start = os::elapsedTime();
3503     HandleMark hm;  // Discard invalid handles created during verification
3504     prepare_for_verify();
3505     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3506     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3507   }
3508 
3509   return verify_time_ms;
3510 }
3511 
3512 void G1CollectedHeap::verify_before_gc() {
3513   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3514   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3515 }
3516 
3517 void G1CollectedHeap::verify_after_gc() {
3518   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3519   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3520 }
3521 
3522 class PrintRegionClosure: public HeapRegionClosure {
3523   outputStream* _st;
3524 public:
3525   PrintRegionClosure(outputStream* st) : _st(st) {}
3526   bool doHeapRegion(HeapRegion* r) {
3527     r->print_on(_st);
3528     return false;
3529   }
3530 };
3531 
3532 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3533                                        const HeapRegion* hr,
3534                                        const VerifyOption vo) const {
3535   switch (vo) {
3536   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3537   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3538   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3539   default:                            ShouldNotReachHere();
3540   }
3541   return false; // keep some compilers happy
3542 }
3543 
3544 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3545                                        const VerifyOption vo) const {
3546   switch (vo) {
3547   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3548   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3549   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3550   default:                            ShouldNotReachHere();
3551   }
3552   return false; // keep some compilers happy
3553 }
3554 
3555 void G1CollectedHeap::print_on(outputStream* st) const {
3556   st->print(" %-20s", "garbage-first heap");
3557   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3558             capacity()/K, used_unlocked()/K);
3559   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3560             _g1_storage.low_boundary(),
3561             _g1_storage.high(),
3562             _g1_storage.high_boundary());
3563   st->cr();
3564   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3565   uint young_regions = _young_list->length();
3566   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3567             (size_t) young_regions * HeapRegion::GrainBytes / K);
3568   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3569   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3570             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3571   st->cr();
3572   MetaspaceAux::print_on(st);
3573 }
3574 
3575 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3576   print_on(st);
3577 
3578   // Print the per-region information.
3579   st->cr();
3580   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3581                "HS=humongous(starts), HC=humongous(continues), "
3582                "CS=collection set, F=free, TS=gc time stamp, "
3583                "PTAMS=previous top-at-mark-start, "
3584                "NTAMS=next top-at-mark-start)");
3585   PrintRegionClosure blk(st);
3586   heap_region_iterate(&blk);
3587 }
3588 
3589 void G1CollectedHeap::print_on_error(outputStream* st) const {
3590   this->CollectedHeap::print_on_error(st);
3591 
3592   if (_cm != NULL) {
3593     st->cr();
3594     _cm->print_on_error(st);
3595   }
3596 }
3597 
3598 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3599   if (G1CollectedHeap::use_parallel_gc_threads()) {
3600     workers()->print_worker_threads_on(st);
3601   }
3602   _cmThread->print_on(st);
3603   st->cr();
3604   _cm->print_worker_threads_on(st);
3605   _cg1r->print_worker_threads_on(st);
3606   if (G1StringDedup::is_enabled()) {
3607     G1StringDedup::print_worker_threads_on(st);
3608   }
3609 }
3610 
3611 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3612   if (G1CollectedHeap::use_parallel_gc_threads()) {
3613     workers()->threads_do(tc);
3614   }
3615   tc->do_thread(_cmThread);
3616   _cg1r->threads_do(tc);
3617   if (G1StringDedup::is_enabled()) {
3618     G1StringDedup::threads_do(tc);
3619   }
3620 }
3621 
3622 void G1CollectedHeap::print_tracing_info() const {
3623   // We'll overload this to mean "trace GC pause statistics."
3624   if (TraceGen0Time || TraceGen1Time) {
3625     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3626     // to that.
3627     g1_policy()->print_tracing_info();
3628   }
3629   if (G1SummarizeRSetStats) {
3630     g1_rem_set()->print_summary_info();
3631   }
3632   if (G1SummarizeConcMark) {
3633     concurrent_mark()->print_summary_info();
3634   }
3635   g1_policy()->print_yg_surv_rate_info();
3636   SpecializationStats::print();
3637 }
3638 
3639 #ifndef PRODUCT
3640 // Helpful for debugging RSet issues.
3641 
3642 class PrintRSetsClosure : public HeapRegionClosure {
3643 private:
3644   const char* _msg;
3645   size_t _occupied_sum;
3646 
3647 public:
3648   bool doHeapRegion(HeapRegion* r) {
3649     HeapRegionRemSet* hrrs = r->rem_set();
3650     size_t occupied = hrrs->occupied();
3651     _occupied_sum += occupied;
3652 
3653     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3654                            HR_FORMAT_PARAMS(r));
3655     if (occupied == 0) {
3656       gclog_or_tty->print_cr("  RSet is empty");
3657     } else {
3658       hrrs->print();
3659     }
3660     gclog_or_tty->print_cr("----------");
3661     return false;
3662   }
3663 
3664   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3665     gclog_or_tty->cr();
3666     gclog_or_tty->print_cr("========================================");
3667     gclog_or_tty->print_cr("%s", msg);
3668     gclog_or_tty->cr();
3669   }
3670 
3671   ~PrintRSetsClosure() {
3672     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3673     gclog_or_tty->print_cr("========================================");
3674     gclog_or_tty->cr();
3675   }
3676 };
3677 
3678 void G1CollectedHeap::print_cset_rsets() {
3679   PrintRSetsClosure cl("Printing CSet RSets");
3680   collection_set_iterate(&cl);
3681 }
3682 
3683 void G1CollectedHeap::print_all_rsets() {
3684   PrintRSetsClosure cl("Printing All RSets");;
3685   heap_region_iterate(&cl);
3686 }
3687 #endif // PRODUCT
3688 
3689 G1CollectedHeap* G1CollectedHeap::heap() {
3690   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3691          "not a garbage-first heap");
3692   return _g1h;
3693 }
3694 
3695 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3696   // always_do_update_barrier = false;
3697   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3698   // Fill TLAB's and such
3699   accumulate_statistics_all_tlabs();
3700   ensure_parsability(true);
3701 
3702   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3703       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3704     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3705   }
3706 }
3707 
3708 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3709 
3710   if (G1SummarizeRSetStats &&
3711       (G1SummarizeRSetStatsPeriod > 0) &&
3712       // we are at the end of the GC. Total collections has already been increased.
3713       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3714     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3715   }
3716 
3717   // FIXME: what is this about?
3718   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3719   // is set.
3720   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3721                         "derived pointer present"));
3722   // always_do_update_barrier = true;
3723 
3724   resize_all_tlabs();
3725 
3726   // We have just completed a GC. Update the soft reference
3727   // policy with the new heap occupancy
3728   Universe::update_heap_info_at_gc();
3729 }
3730 
3731 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3732                                                unsigned int gc_count_before,
3733                                                bool* succeeded,
3734                                                GCCause::Cause gc_cause) {
3735   assert_heap_not_locked_and_not_at_safepoint();
3736   g1_policy()->record_stop_world_start();
3737   VM_G1IncCollectionPause op(gc_count_before,
3738                              word_size,
3739                              false, /* should_initiate_conc_mark */
3740                              g1_policy()->max_pause_time_ms(),
3741                              gc_cause);
3742   VMThread::execute(&op);
3743 
3744   HeapWord* result = op.result();
3745   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3746   assert(result == NULL || ret_succeeded,
3747          "the result should be NULL if the VM did not succeed");
3748   *succeeded = ret_succeeded;
3749 
3750   assert_heap_not_locked();
3751   return result;
3752 }
3753 
3754 void
3755 G1CollectedHeap::doConcurrentMark() {
3756   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3757   if (!_cmThread->in_progress()) {
3758     _cmThread->set_started();
3759     CGC_lock->notify();
3760   }
3761 }
3762 
3763 size_t G1CollectedHeap::pending_card_num() {
3764   size_t extra_cards = 0;
3765   JavaThread *curr = Threads::first();
3766   while (curr != NULL) {
3767     DirtyCardQueue& dcq = curr->dirty_card_queue();
3768     extra_cards += dcq.size();
3769     curr = curr->next();
3770   }
3771   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3772   size_t buffer_size = dcqs.buffer_size();
3773   size_t buffer_num = dcqs.completed_buffers_num();
3774 
3775   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3776   // in bytes - not the number of 'entries'. We need to convert
3777   // into a number of cards.
3778   return (buffer_size * buffer_num + extra_cards) / oopSize;
3779 }
3780 
3781 size_t G1CollectedHeap::cards_scanned() {
3782   return g1_rem_set()->cardsScanned();
3783 }
3784 
3785 void
3786 G1CollectedHeap::setup_surviving_young_words() {
3787   assert(_surviving_young_words == NULL, "pre-condition");
3788   uint array_length = g1_policy()->young_cset_region_length();
3789   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3790   if (_surviving_young_words == NULL) {
3791     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3792                           "Not enough space for young surv words summary.");
3793   }
3794   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3795 #ifdef ASSERT
3796   for (uint i = 0;  i < array_length; ++i) {
3797     assert( _surviving_young_words[i] == 0, "memset above" );
3798   }
3799 #endif // !ASSERT
3800 }
3801 
3802 void
3803 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3804   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3805   uint array_length = g1_policy()->young_cset_region_length();
3806   for (uint i = 0; i < array_length; ++i) {
3807     _surviving_young_words[i] += surv_young_words[i];
3808   }
3809 }
3810 
3811 void
3812 G1CollectedHeap::cleanup_surviving_young_words() {
3813   guarantee( _surviving_young_words != NULL, "pre-condition" );
3814   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3815   _surviving_young_words = NULL;
3816 }
3817 
3818 #ifdef ASSERT
3819 class VerifyCSetClosure: public HeapRegionClosure {
3820 public:
3821   bool doHeapRegion(HeapRegion* hr) {
3822     // Here we check that the CSet region's RSet is ready for parallel
3823     // iteration. The fields that we'll verify are only manipulated
3824     // when the region is part of a CSet and is collected. Afterwards,
3825     // we reset these fields when we clear the region's RSet (when the
3826     // region is freed) so they are ready when the region is
3827     // re-allocated. The only exception to this is if there's an
3828     // evacuation failure and instead of freeing the region we leave
3829     // it in the heap. In that case, we reset these fields during
3830     // evacuation failure handling.
3831     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3832 
3833     // Here's a good place to add any other checks we'd like to
3834     // perform on CSet regions.
3835     return false;
3836   }
3837 };
3838 #endif // ASSERT
3839 
3840 #if TASKQUEUE_STATS
3841 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3842   st->print_raw_cr("GC Task Stats");
3843   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3844   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3845 }
3846 
3847 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3848   print_taskqueue_stats_hdr(st);
3849 
3850   TaskQueueStats totals;
3851   const int n = workers() != NULL ? workers()->total_workers() : 1;
3852   for (int i = 0; i < n; ++i) {
3853     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3854     totals += task_queue(i)->stats;
3855   }
3856   st->print_raw("tot "); totals.print(st); st->cr();
3857 
3858   DEBUG_ONLY(totals.verify());
3859 }
3860 
3861 void G1CollectedHeap::reset_taskqueue_stats() {
3862   const int n = workers() != NULL ? workers()->total_workers() : 1;
3863   for (int i = 0; i < n; ++i) {
3864     task_queue(i)->stats.reset();
3865   }
3866 }
3867 #endif // TASKQUEUE_STATS
3868 
3869 void G1CollectedHeap::log_gc_header() {
3870   if (!G1Log::fine()) {
3871     return;
3872   }
3873 
3874   gclog_or_tty->date_stamp(PrintGCDateStamps);
3875   gclog_or_tty->stamp(PrintGCTimeStamps);
3876 
3877   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3878     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3879     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3880 
3881   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3882 }
3883 
3884 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3885   if (!G1Log::fine()) {
3886     return;
3887   }
3888 
3889   if (G1Log::finer()) {
3890     if (evacuation_failed()) {
3891       gclog_or_tty->print(" (to-space exhausted)");
3892     }
3893     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3894     g1_policy()->phase_times()->note_gc_end();
3895     g1_policy()->phase_times()->print(pause_time_sec);
3896     g1_policy()->print_detailed_heap_transition();
3897   } else {
3898     if (evacuation_failed()) {
3899       gclog_or_tty->print("--");
3900     }
3901     g1_policy()->print_heap_transition();
3902     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3903   }
3904   gclog_or_tty->flush();
3905 }
3906 
3907 bool
3908 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3909   assert_at_safepoint(true /* should_be_vm_thread */);
3910   guarantee(!is_gc_active(), "collection is not reentrant");
3911 
3912   if (GC_locker::check_active_before_gc()) {
3913     return false;
3914   }
3915 
3916   _gc_timer_stw->register_gc_start();
3917 
3918   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3919 
3920   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3921   ResourceMark rm;
3922 
3923   print_heap_before_gc();
3924   trace_heap_before_gc(_gc_tracer_stw);
3925 
3926   verify_region_sets_optional();
3927   verify_dirty_young_regions();
3928 
3929   // This call will decide whether this pause is an initial-mark
3930   // pause. If it is, during_initial_mark_pause() will return true
3931   // for the duration of this pause.
3932   g1_policy()->decide_on_conc_mark_initiation();
3933 
3934   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3935   assert(!g1_policy()->during_initial_mark_pause() ||
3936           g1_policy()->gcs_are_young(), "sanity");
3937 
3938   // We also do not allow mixed GCs during marking.
3939   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3940 
3941   // Record whether this pause is an initial mark. When the current
3942   // thread has completed its logging output and it's safe to signal
3943   // the CM thread, the flag's value in the policy has been reset.
3944   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3945 
3946   // Inner scope for scope based logging, timers, and stats collection
3947   {
3948     EvacuationInfo evacuation_info;
3949 
3950     if (g1_policy()->during_initial_mark_pause()) {
3951       // We are about to start a marking cycle, so we increment the
3952       // full collection counter.
3953       increment_old_marking_cycles_started();
3954       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3955     }
3956 
3957     _gc_tracer_stw->report_yc_type(yc_type());
3958 
3959     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3960 
3961     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3962                                 workers()->active_workers() : 1);
3963     double pause_start_sec = os::elapsedTime();
3964     g1_policy()->phase_times()->note_gc_start(active_workers);
3965     log_gc_header();
3966 
3967     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3968     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3969 
3970     // If the secondary_free_list is not empty, append it to the
3971     // free_list. No need to wait for the cleanup operation to finish;
3972     // the region allocation code will check the secondary_free_list
3973     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3974     // set, skip this step so that the region allocation code has to
3975     // get entries from the secondary_free_list.
3976     if (!G1StressConcRegionFreeing) {
3977       append_secondary_free_list_if_not_empty_with_lock();
3978     }
3979 
3980     assert(check_young_list_well_formed(), "young list should be well formed");
3981     assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3982            "sanity check");
3983 
3984     // Don't dynamically change the number of GC threads this early.  A value of
3985     // 0 is used to indicate serial work.  When parallel work is done,
3986     // it will be set.
3987 
3988     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3989       IsGCActiveMark x;
3990 
3991       gc_prologue(false);
3992       increment_total_collections(false /* full gc */);
3993       increment_gc_time_stamp();
3994 
3995       verify_before_gc();
3996       check_bitmaps("GC Start");
3997 
3998       COMPILER2_PRESENT(DerivedPointerTable::clear());
3999 
4000       // Please see comment in g1CollectedHeap.hpp and
4001       // G1CollectedHeap::ref_processing_init() to see how
4002       // reference processing currently works in G1.
4003 
4004       // Enable discovery in the STW reference processor
4005       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
4006                                             true /*verify_no_refs*/);
4007 
4008       {
4009         // We want to temporarily turn off discovery by the
4010         // CM ref processor, if necessary, and turn it back on
4011         // on again later if we do. Using a scoped
4012         // NoRefDiscovery object will do this.
4013         NoRefDiscovery no_cm_discovery(ref_processor_cm());
4014 
4015         // Forget the current alloc region (we might even choose it to be part
4016         // of the collection set!).
4017         release_mutator_alloc_region();
4018 
4019         // We should call this after we retire the mutator alloc
4020         // region(s) so that all the ALLOC / RETIRE events are generated
4021         // before the start GC event.
4022         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4023 
4024         // This timing is only used by the ergonomics to handle our pause target.
4025         // It is unclear why this should not include the full pause. We will
4026         // investigate this in CR 7178365.
4027         //
4028         // Preserving the old comment here if that helps the investigation:
4029         //
4030         // The elapsed time induced by the start time below deliberately elides
4031         // the possible verification above.
4032         double sample_start_time_sec = os::elapsedTime();
4033 
4034 #if YOUNG_LIST_VERBOSE
4035         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4036         _young_list->print();
4037         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4038 #endif // YOUNG_LIST_VERBOSE
4039 
4040         g1_policy()->record_collection_pause_start(sample_start_time_sec);
4041 
4042         double scan_wait_start = os::elapsedTime();
4043         // We have to wait until the CM threads finish scanning the
4044         // root regions as it's the only way to ensure that all the
4045         // objects on them have been correctly scanned before we start
4046         // moving them during the GC.
4047         bool waited = _cm->root_regions()->wait_until_scan_finished();
4048         double wait_time_ms = 0.0;
4049         if (waited) {
4050           double scan_wait_end = os::elapsedTime();
4051           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4052         }
4053         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4054 
4055 #if YOUNG_LIST_VERBOSE
4056         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4057         _young_list->print();
4058 #endif // YOUNG_LIST_VERBOSE
4059 
4060         if (g1_policy()->during_initial_mark_pause()) {
4061           concurrent_mark()->checkpointRootsInitialPre();
4062         }
4063 
4064 #if YOUNG_LIST_VERBOSE
4065         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4066         _young_list->print();
4067         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4068 #endif // YOUNG_LIST_VERBOSE
4069 
4070         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4071 
4072         _cm->note_start_of_gc();
4073         // We should not verify the per-thread SATB buffers given that
4074         // we have not filtered them yet (we'll do so during the
4075         // GC). We also call this after finalize_cset() to
4076         // ensure that the CSet has been finalized.
4077         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4078                                  true  /* verify_enqueued_buffers */,
4079                                  false /* verify_thread_buffers */,
4080                                  true  /* verify_fingers */);
4081 
4082         if (_hr_printer.is_active()) {
4083           HeapRegion* hr = g1_policy()->collection_set();
4084           while (hr != NULL) {
4085             G1HRPrinter::RegionType type;
4086             if (!hr->is_young()) {
4087               type = G1HRPrinter::Old;
4088             } else if (hr->is_survivor()) {
4089               type = G1HRPrinter::Survivor;
4090             } else {
4091               type = G1HRPrinter::Eden;
4092             }
4093             _hr_printer.cset(hr);
4094             hr = hr->next_in_collection_set();
4095           }
4096         }
4097 
4098 #ifdef ASSERT
4099         VerifyCSetClosure cl;
4100         collection_set_iterate(&cl);
4101 #endif // ASSERT
4102 
4103         setup_surviving_young_words();
4104 
4105         // Initialize the GC alloc regions.
4106         init_gc_alloc_regions(evacuation_info);
4107 
4108         // Actually do the work...
4109         evacuate_collection_set(evacuation_info);
4110 
4111         // We do this to mainly verify the per-thread SATB buffers
4112         // (which have been filtered by now) since we didn't verify
4113         // them earlier. No point in re-checking the stacks / enqueued
4114         // buffers given that the CSet has not changed since last time
4115         // we checked.
4116         _cm->verify_no_cset_oops(false /* verify_stacks */,
4117                                  false /* verify_enqueued_buffers */,
4118                                  true  /* verify_thread_buffers */,
4119                                  true  /* verify_fingers */);
4120 
4121         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4122         g1_policy()->clear_collection_set();
4123 
4124         cleanup_surviving_young_words();
4125 
4126         // Start a new incremental collection set for the next pause.
4127         g1_policy()->start_incremental_cset_building();
4128 
4129         clear_cset_fast_test();
4130 
4131         _young_list->reset_sampled_info();
4132 
4133         // Don't check the whole heap at this point as the
4134         // GC alloc regions from this pause have been tagged
4135         // as survivors and moved on to the survivor list.
4136         // Survivor regions will fail the !is_young() check.
4137         assert(check_young_list_empty(false /* check_heap */),
4138           "young list should be empty");
4139 
4140 #if YOUNG_LIST_VERBOSE
4141         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4142         _young_list->print();
4143 #endif // YOUNG_LIST_VERBOSE
4144 
4145         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4146                                              _young_list->first_survivor_region(),
4147                                              _young_list->last_survivor_region());
4148 
4149         _young_list->reset_auxilary_lists();
4150 
4151         if (evacuation_failed()) {
4152           _summary_bytes_used = recalculate_used();
4153           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4154           for (uint i = 0; i < n_queues; i++) {
4155             if (_evacuation_failed_info_array[i].has_failed()) {
4156               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4157             }
4158           }
4159         } else {
4160           // The "used" of the the collection set have already been subtracted
4161           // when they were freed.  Add in the bytes evacuated.
4162           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4163         }
4164 
4165         if (g1_policy()->during_initial_mark_pause()) {
4166           // We have to do this before we notify the CM threads that
4167           // they can start working to make sure that all the
4168           // appropriate initialization is done on the CM object.
4169           concurrent_mark()->checkpointRootsInitialPost();
4170           set_marking_started();
4171           // Note that we don't actually trigger the CM thread at
4172           // this point. We do that later when we're sure that
4173           // the current thread has completed its logging output.
4174         }
4175 
4176         allocate_dummy_regions();
4177 
4178 #if YOUNG_LIST_VERBOSE
4179         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4180         _young_list->print();
4181         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4182 #endif // YOUNG_LIST_VERBOSE
4183 
4184         init_mutator_alloc_region();
4185 
4186         {
4187           size_t expand_bytes = g1_policy()->expansion_amount();
4188           if (expand_bytes > 0) {
4189             size_t bytes_before = capacity();
4190             // No need for an ergo verbose message here,
4191             // expansion_amount() does this when it returns a value > 0.
4192             if (!expand(expand_bytes)) {
4193               // We failed to expand the heap so let's verify that
4194               // committed/uncommitted amount match the backing store
4195               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4196               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4197             }
4198           }
4199         }
4200 
4201         // We redo the verification but now wrt to the new CSet which
4202         // has just got initialized after the previous CSet was freed.
4203         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4204                                  true  /* verify_enqueued_buffers */,
4205                                  true  /* verify_thread_buffers */,
4206                                  true  /* verify_fingers */);
4207         _cm->note_end_of_gc();
4208 
4209         // This timing is only used by the ergonomics to handle our pause target.
4210         // It is unclear why this should not include the full pause. We will
4211         // investigate this in CR 7178365.
4212         double sample_end_time_sec = os::elapsedTime();
4213         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4214         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4215 
4216         MemoryService::track_memory_usage();
4217 
4218         // In prepare_for_verify() below we'll need to scan the deferred
4219         // update buffers to bring the RSets up-to-date if
4220         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4221         // the update buffers we'll probably need to scan cards on the
4222         // regions we just allocated to (i.e., the GC alloc
4223         // regions). However, during the last GC we called
4224         // set_saved_mark() on all the GC alloc regions, so card
4225         // scanning might skip the [saved_mark_word()...top()] area of
4226         // those regions (i.e., the area we allocated objects into
4227         // during the last GC). But it shouldn't. Given that
4228         // saved_mark_word() is conditional on whether the GC time stamp
4229         // on the region is current or not, by incrementing the GC time
4230         // stamp here we invalidate all the GC time stamps on all the
4231         // regions and saved_mark_word() will simply return top() for
4232         // all the regions. This is a nicer way of ensuring this rather
4233         // than iterating over the regions and fixing them. In fact, the
4234         // GC time stamp increment here also ensures that
4235         // saved_mark_word() will return top() between pauses, i.e.,
4236         // during concurrent refinement. So we don't need the
4237         // is_gc_active() check to decided which top to use when
4238         // scanning cards (see CR 7039627).
4239         increment_gc_time_stamp();
4240 
4241         verify_after_gc();
4242         check_bitmaps("GC End");
4243 
4244         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4245         ref_processor_stw()->verify_no_references_recorded();
4246 
4247         // CM reference discovery will be re-enabled if necessary.
4248       }
4249 
4250       // We should do this after we potentially expand the heap so
4251       // that all the COMMIT events are generated before the end GC
4252       // event, and after we retire the GC alloc regions so that all
4253       // RETIRE events are generated before the end GC event.
4254       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4255 
4256       if (mark_in_progress()) {
4257         concurrent_mark()->update_g1_committed();
4258       }
4259 
4260 #ifdef TRACESPINNING
4261       ParallelTaskTerminator::print_termination_counts();
4262 #endif
4263 
4264       gc_epilogue(false);
4265     }
4266 
4267     // Print the remainder of the GC log output.
4268     log_gc_footer(os::elapsedTime() - pause_start_sec);
4269 
4270     // It is not yet to safe to tell the concurrent mark to
4271     // start as we have some optional output below. We don't want the
4272     // output from the concurrent mark thread interfering with this
4273     // logging output either.
4274 
4275     _hrs.verify_optional();
4276     verify_region_sets_optional();
4277 
4278     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4279     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4280 
4281     print_heap_after_gc();
4282     trace_heap_after_gc(_gc_tracer_stw);
4283 
4284     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4285     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4286     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4287     // before any GC notifications are raised.
4288     g1mm()->update_sizes();
4289 
4290     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4291     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4292     _gc_timer_stw->register_gc_end();
4293     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4294   }
4295   // It should now be safe to tell the concurrent mark thread to start
4296   // without its logging output interfering with the logging output
4297   // that came from the pause.
4298 
4299   if (should_start_conc_mark) {
4300     // CAUTION: after the doConcurrentMark() call below,
4301     // the concurrent marking thread(s) could be running
4302     // concurrently with us. Make sure that anything after
4303     // this point does not assume that we are the only GC thread
4304     // running. Note: of course, the actual marking work will
4305     // not start until the safepoint itself is released in
4306     // SuspendibleThreadSet::desynchronize().
4307     doConcurrentMark();
4308   }
4309 
4310   return true;
4311 }
4312 
4313 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4314 {
4315   size_t gclab_word_size;
4316   switch (purpose) {
4317     case GCAllocForSurvived:
4318       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4319       break;
4320     case GCAllocForTenured:
4321       gclab_word_size = _old_plab_stats.desired_plab_sz();
4322       break;
4323     default:
4324       assert(false, "unknown GCAllocPurpose");
4325       gclab_word_size = _old_plab_stats.desired_plab_sz();
4326       break;
4327   }
4328 
4329   // Prevent humongous PLAB sizes for two reasons:
4330   // * PLABs are allocated using a similar paths as oops, but should
4331   //   never be in a humongous region
4332   // * Allowing humongous PLABs needlessly churns the region free lists
4333   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4334 }
4335 
4336 void G1CollectedHeap::init_mutator_alloc_region() {
4337   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4338   _mutator_alloc_region.init();
4339 }
4340 
4341 void G1CollectedHeap::release_mutator_alloc_region() {
4342   _mutator_alloc_region.release();
4343   assert(_mutator_alloc_region.get() == NULL, "post-condition");
4344 }
4345 
4346 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4347   assert_at_safepoint(true /* should_be_vm_thread */);
4348 
4349   _survivor_gc_alloc_region.init();
4350   _old_gc_alloc_region.init();
4351   HeapRegion* retained_region = _retained_old_gc_alloc_region;
4352   _retained_old_gc_alloc_region = NULL;
4353 
4354   // We will discard the current GC alloc region if:
4355   // a) it's in the collection set (it can happen!),
4356   // b) it's already full (no point in using it),
4357   // c) it's empty (this means that it was emptied during
4358   // a cleanup and it should be on the free list now), or
4359   // d) it's humongous (this means that it was emptied
4360   // during a cleanup and was added to the free list, but
4361   // has been subsequently used to allocate a humongous
4362   // object that may be less than the region size).
4363   if (retained_region != NULL &&
4364       !retained_region->in_collection_set() &&
4365       !(retained_region->top() == retained_region->end()) &&
4366       !retained_region->is_empty() &&
4367       !retained_region->isHumongous()) {
4368     retained_region->set_saved_mark();
4369     // The retained region was added to the old region set when it was
4370     // retired. We have to remove it now, since we don't allow regions
4371     // we allocate to in the region sets. We'll re-add it later, when
4372     // it's retired again.
4373     _old_set.remove(retained_region);
4374     bool during_im = g1_policy()->during_initial_mark_pause();
4375     retained_region->note_start_of_copying(during_im);
4376     _old_gc_alloc_region.set(retained_region);
4377     _hr_printer.reuse(retained_region);
4378     evacuation_info.set_alloc_regions_used_before(retained_region->used());
4379   }
4380 }
4381 
4382 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4383   evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4384                                          _old_gc_alloc_region.count());
4385   _survivor_gc_alloc_region.release();
4386   // If we have an old GC alloc region to release, we'll save it in
4387   // _retained_old_gc_alloc_region. If we don't
4388   // _retained_old_gc_alloc_region will become NULL. This is what we
4389   // want either way so no reason to check explicitly for either
4390   // condition.
4391   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4392 
4393   if (ResizePLAB) {
4394     _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4395     _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4396   }
4397 }
4398 
4399 void G1CollectedHeap::abandon_gc_alloc_regions() {
4400   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4401   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4402   _retained_old_gc_alloc_region = NULL;
4403 }
4404 
4405 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4406   _drain_in_progress = false;
4407   set_evac_failure_closure(cl);
4408   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4409 }
4410 
4411 void G1CollectedHeap::finalize_for_evac_failure() {
4412   assert(_evac_failure_scan_stack != NULL &&
4413          _evac_failure_scan_stack->length() == 0,
4414          "Postcondition");
4415   assert(!_drain_in_progress, "Postcondition");
4416   delete _evac_failure_scan_stack;
4417   _evac_failure_scan_stack = NULL;
4418 }
4419 
4420 void G1CollectedHeap::remove_self_forwarding_pointers() {
4421   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4422 
4423   double remove_self_forwards_start = os::elapsedTime();
4424 
4425   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4426 
4427   if (G1CollectedHeap::use_parallel_gc_threads()) {
4428     set_par_threads();
4429     workers()->run_task(&rsfp_task);
4430     set_par_threads(0);
4431   } else {
4432     rsfp_task.work(0);
4433   }
4434 
4435   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4436 
4437   // Reset the claim values in the regions in the collection set.
4438   reset_cset_heap_region_claim_values();
4439 
4440   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4441 
4442   // Now restore saved marks, if any.
4443   assert(_objs_with_preserved_marks.size() ==
4444             _preserved_marks_of_objs.size(), "Both or none.");
4445   while (!_objs_with_preserved_marks.is_empty()) {
4446     oop obj = _objs_with_preserved_marks.pop();
4447     markOop m = _preserved_marks_of_objs.pop();
4448     obj->set_mark(m);
4449   }
4450   _objs_with_preserved_marks.clear(true);
4451   _preserved_marks_of_objs.clear(true);
4452 
4453   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4454 }
4455 
4456 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4457   _evac_failure_scan_stack->push(obj);
4458 }
4459 
4460 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4461   assert(_evac_failure_scan_stack != NULL, "precondition");
4462 
4463   while (_evac_failure_scan_stack->length() > 0) {
4464      oop obj = _evac_failure_scan_stack->pop();
4465      _evac_failure_closure->set_region(heap_region_containing(obj));
4466      obj->oop_iterate_backwards(_evac_failure_closure);
4467   }
4468 }
4469 
4470 oop
4471 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4472                                                oop old) {
4473   assert(obj_in_cs(old),
4474          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4475                  (HeapWord*) old));
4476   markOop m = old->mark();
4477   oop forward_ptr = old->forward_to_atomic(old);
4478   if (forward_ptr == NULL) {
4479     // Forward-to-self succeeded.
4480     assert(_par_scan_state != NULL, "par scan state");
4481     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4482     uint queue_num = _par_scan_state->queue_num();
4483 
4484     _evacuation_failed = true;
4485     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4486     if (_evac_failure_closure != cl) {
4487       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4488       assert(!_drain_in_progress,
4489              "Should only be true while someone holds the lock.");
4490       // Set the global evac-failure closure to the current thread's.
4491       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4492       set_evac_failure_closure(cl);
4493       // Now do the common part.
4494       handle_evacuation_failure_common(old, m);
4495       // Reset to NULL.
4496       set_evac_failure_closure(NULL);
4497     } else {
4498       // The lock is already held, and this is recursive.
4499       assert(_drain_in_progress, "This should only be the recursive case.");
4500       handle_evacuation_failure_common(old, m);
4501     }
4502     return old;
4503   } else {
4504     // Forward-to-self failed. Either someone else managed to allocate
4505     // space for this object (old != forward_ptr) or they beat us in
4506     // self-forwarding it (old == forward_ptr).
4507     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4508            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4509                    "should not be in the CSet",
4510                    (HeapWord*) old, (HeapWord*) forward_ptr));
4511     return forward_ptr;
4512   }
4513 }
4514 
4515 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4516   preserve_mark_if_necessary(old, m);
4517 
4518   HeapRegion* r = heap_region_containing(old);
4519   if (!r->evacuation_failed()) {
4520     r->set_evacuation_failed(true);
4521     _hr_printer.evac_failure(r);
4522   }
4523 
4524   push_on_evac_failure_scan_stack(old);
4525 
4526   if (!_drain_in_progress) {
4527     // prevent recursion in copy_to_survivor_space()
4528     _drain_in_progress = true;
4529     drain_evac_failure_scan_stack();
4530     _drain_in_progress = false;
4531   }
4532 }
4533 
4534 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4535   assert(evacuation_failed(), "Oversaving!");
4536   // We want to call the "for_promotion_failure" version only in the
4537   // case of a promotion failure.
4538   if (m->must_be_preserved_for_promotion_failure(obj)) {
4539     _objs_with_preserved_marks.push(obj);
4540     _preserved_marks_of_objs.push(m);
4541   }
4542 }
4543 
4544 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4545                                                   size_t word_size) {
4546   if (purpose == GCAllocForSurvived) {
4547     HeapWord* result = survivor_attempt_allocation(word_size);
4548     if (result != NULL) {
4549       return result;
4550     } else {
4551       // Let's try to allocate in the old gen in case we can fit the
4552       // object there.
4553       return old_attempt_allocation(word_size);
4554     }
4555   } else {
4556     assert(purpose ==  GCAllocForTenured, "sanity");
4557     HeapWord* result = old_attempt_allocation(word_size);
4558     if (result != NULL) {
4559       return result;
4560     } else {
4561       // Let's try to allocate in the survivors in case we can fit the
4562       // object there.
4563       return survivor_attempt_allocation(word_size);
4564     }
4565   }
4566 
4567   ShouldNotReachHere();
4568   // Trying to keep some compilers happy.
4569   return NULL;
4570 }
4571 
4572 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4573   ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4574 
4575 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp)
4576   : _g1h(g1h),
4577     _refs(g1h->task_queue(queue_num)),
4578     _dcq(&g1h->dirty_card_queue_set()),
4579     _ct_bs(g1h->g1_barrier_set()),
4580     _g1_rem(g1h->g1_rem_set()),
4581     _hash_seed(17), _queue_num(queue_num),
4582     _term_attempts(0),
4583     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4584     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4585     _age_table(false), _scanner(g1h, this, rp),
4586     _strong_roots_time(0), _term_time(0),
4587     _alloc_buffer_waste(0), _undo_waste(0) {
4588   // we allocate G1YoungSurvRateNumRegions plus one entries, since
4589   // we "sacrifice" entry 0 to keep track of surviving bytes for
4590   // non-young regions (where the age is -1)
4591   // We also add a few elements at the beginning and at the end in
4592   // an attempt to eliminate cache contention
4593   uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4594   uint array_length = PADDING_ELEM_NUM +
4595                       real_length +
4596                       PADDING_ELEM_NUM;
4597   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4598   if (_surviving_young_words_base == NULL)
4599     vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
4600                           "Not enough space for young surv histo.");
4601   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4602   memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4603 
4604   _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4605   _alloc_buffers[GCAllocForTenured]  = &_tenured_alloc_buffer;
4606 
4607   _start = os::elapsedTime();
4608 }
4609 
4610 void
4611 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4612 {
4613   st->print_raw_cr("GC Termination Stats");
4614   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------"
4615                    " ------waste (KiB)------");
4616   st->print_raw_cr("thr     ms        ms      %        ms      %    attempts"
4617                    "  total   alloc    undo");
4618   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4619                    " ------- ------- -------");
4620 }
4621 
4622 void
4623 G1ParScanThreadState::print_termination_stats(int i,
4624                                               outputStream* const st) const
4625 {
4626   const double elapsed_ms = elapsed_time() * 1000.0;
4627   const double s_roots_ms = strong_roots_time() * 1000.0;
4628   const double term_ms    = term_time() * 1000.0;
4629   st->print_cr("%3d %9.2f %9.2f %6.2f "
4630                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4631                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4632                i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4633                term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4634                (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4635                alloc_buffer_waste() * HeapWordSize / K,
4636                undo_waste() * HeapWordSize / K);
4637 }
4638 
4639 #ifdef ASSERT
4640 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4641   assert(ref != NULL, "invariant");
4642   assert(UseCompressedOops, "sanity");
4643   assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4644   oop p = oopDesc::load_decode_heap_oop(ref);
4645   assert(_g1h->is_in_g1_reserved(p),
4646          err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4647   return true;
4648 }
4649 
4650 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4651   assert(ref != NULL, "invariant");
4652   if (has_partial_array_mask(ref)) {
4653     // Must be in the collection set--it's already been copied.
4654     oop p = clear_partial_array_mask(ref);
4655     assert(_g1h->obj_in_cs(p),
4656            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4657   } else {
4658     oop p = oopDesc::load_decode_heap_oop(ref);
4659     assert(_g1h->is_in_g1_reserved(p),
4660            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4661   }
4662   return true;
4663 }
4664 
4665 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4666   if (ref.is_narrow()) {
4667     return verify_ref((narrowOop*) ref);
4668   } else {
4669     return verify_ref((oop*) ref);
4670   }
4671 }
4672 #endif // ASSERT
4673 
4674 void G1ParScanThreadState::trim_queue() {
4675   assert(_evac_failure_cl != NULL, "not set");
4676 
4677   StarTask ref;
4678   do {
4679     // Drain the overflow stack first, so other threads can steal.
4680     while (refs()->pop_overflow(ref)) {
4681       deal_with_reference(ref);
4682     }
4683 
4684     while (refs()->pop_local(ref)) {
4685       deal_with_reference(ref);
4686     }
4687   } while (!refs()->is_empty());
4688 }
4689 
4690 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4691                                      G1ParScanThreadState* par_scan_state) :
4692   _g1(g1), _par_scan_state(par_scan_state),
4693   _worker_id(par_scan_state->queue_num()) { }
4694 
4695 void G1ParCopyHelper::mark_object(oop obj) {
4696   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4697 
4698   // We know that the object is not moving so it's safe to read its size.
4699   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4700 }
4701 
4702 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4703   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4704   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4705   assert(from_obj != to_obj, "should not be self-forwarded");
4706 
4707   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4708   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4709 
4710   // The object might be in the process of being copied by another
4711   // worker so we cannot trust that its to-space image is
4712   // well-formed. So we have to read its size from its from-space
4713   // image which we know should not be changing.
4714   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4715 }
4716 
4717 oop G1ParScanThreadState::copy_to_survivor_space(oop const old) {
4718   size_t word_sz = old->size();
4719   HeapRegion* from_region = _g1h->heap_region_containing_raw(old);
4720   // +1 to make the -1 indexes valid...
4721   int       young_index = from_region->young_index_in_cset()+1;
4722   assert( (from_region->is_young() && young_index >  0) ||
4723          (!from_region->is_young() && young_index == 0), "invariant" );
4724   G1CollectorPolicy* g1p = _g1h->g1_policy();
4725   markOop m = old->mark();
4726   int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4727                                            : m->age();
4728   GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4729                                                              word_sz);
4730   HeapWord* obj_ptr = allocate(alloc_purpose, word_sz);
4731 #ifndef PRODUCT
4732   // Should this evacuation fail?
4733   if (_g1h->evacuation_should_fail()) {
4734     if (obj_ptr != NULL) {
4735       undo_allocation(alloc_purpose, obj_ptr, word_sz);
4736       obj_ptr = NULL;
4737     }
4738   }
4739 #endif // !PRODUCT
4740 
4741   if (obj_ptr == NULL) {
4742     // This will either forward-to-self, or detect that someone else has
4743     // installed a forwarding pointer.
4744     return _g1h->handle_evacuation_failure_par(this, old);
4745   }
4746 
4747   oop obj = oop(obj_ptr);
4748 
4749   // We're going to allocate linearly, so might as well prefetch ahead.
4750   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4751 
4752   oop forward_ptr = old->forward_to_atomic(obj);
4753   if (forward_ptr == NULL) {
4754     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4755 
4756     // alloc_purpose is just a hint to allocate() above, recheck the type of region
4757     // we actually allocated from and update alloc_purpose accordingly
4758     HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr);
4759     alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured;
4760 
4761     if (g1p->track_object_age(alloc_purpose)) {
4762       // We could simply do obj->incr_age(). However, this causes a
4763       // performance issue. obj->incr_age() will first check whether
4764       // the object has a displaced mark by checking its mark word;
4765       // getting the mark word from the new location of the object
4766       // stalls. So, given that we already have the mark word and we
4767       // are about to install it anyway, it's better to increase the
4768       // age on the mark word, when the object does not have a
4769       // displaced mark word. We're not expecting many objects to have
4770       // a displaced marked word, so that case is not optimized
4771       // further (it could be...) and we simply call obj->incr_age().
4772 
4773       if (m->has_displaced_mark_helper()) {
4774         // in this case, we have to install the mark word first,
4775         // otherwise obj looks to be forwarded (the old mark word,
4776         // which contains the forward pointer, was copied)
4777         obj->set_mark(m);
4778         obj->incr_age();
4779       } else {
4780         m = m->incr_age();
4781         obj->set_mark(m);
4782       }
4783       age_table()->add(obj, word_sz);
4784     } else {
4785       obj->set_mark(m);
4786     }
4787 
4788     if (G1StringDedup::is_enabled()) {
4789       G1StringDedup::enqueue_from_evacuation(from_region->is_young(),
4790                                              to_region->is_young(),
4791                                              queue_num(),
4792                                              obj);
4793     }
4794 
4795     size_t* surv_young_words = surviving_young_words();
4796     surv_young_words[young_index] += word_sz;
4797 
4798     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4799       // We keep track of the next start index in the length field of
4800       // the to-space object. The actual length can be found in the
4801       // length field of the from-space object.
4802       arrayOop(obj)->set_length(0);
4803       oop* old_p = set_partial_array_mask(old);
4804       push_on_queue(old_p);
4805     } else {
4806       // No point in using the slower heap_region_containing() method,
4807       // given that we know obj is in the heap.
4808       _scanner.set_region(_g1h->heap_region_containing_raw(obj));
4809       obj->oop_iterate_backwards(&_scanner);
4810     }
4811   } else {
4812     undo_allocation(alloc_purpose, obj_ptr, word_sz);
4813     obj = forward_ptr;
4814   }
4815   return obj;
4816 }
4817 
4818 template <class T>
4819 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4820   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4821     _scanned_klass->record_modified_oops();
4822   }
4823 }
4824 
4825 template <G1Barrier barrier, bool do_mark_object>
4826 template <class T>
4827 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4828   T heap_oop = oopDesc::load_heap_oop(p);
4829 
4830   if (oopDesc::is_null(heap_oop)) {
4831     return;
4832   }
4833 
4834   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4835 
4836   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4837 
4838   if (_g1->in_cset_fast_test(obj)) {
4839     oop forwardee;
4840     if (obj->is_forwarded()) {
4841       forwardee = obj->forwardee();
4842     } else {
4843       forwardee = _par_scan_state->copy_to_survivor_space(obj);
4844     }
4845     assert(forwardee != NULL, "forwardee should not be NULL");
4846     oopDesc::encode_store_heap_oop(p, forwardee);
4847     if (do_mark_object && forwardee != obj) {
4848       // If the object is self-forwarded we don't need to explicitly
4849       // mark it, the evacuation failure protocol will do so.
4850       mark_forwarded_object(obj, forwardee);
4851     }
4852 
4853     if (barrier == G1BarrierKlass) {
4854       do_klass_barrier(p, forwardee);
4855     }
4856   } else {
4857     // The object is not in collection set. If we're a root scanning
4858     // closure during an initial mark pause (i.e. do_mark_object will
4859     // be true) then attempt to mark the object.
4860     if (do_mark_object) {
4861       mark_object(obj);
4862     }
4863   }
4864 
4865   if (barrier == G1BarrierEvac) {
4866     _par_scan_state->update_rs(_from, p, _worker_id);
4867   }
4868 }
4869 
4870 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(oop* p);
4871 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4872 
4873 class G1ParEvacuateFollowersClosure : public VoidClosure {
4874 protected:
4875   G1CollectedHeap*              _g1h;
4876   G1ParScanThreadState*         _par_scan_state;
4877   RefToScanQueueSet*            _queues;
4878   ParallelTaskTerminator*       _terminator;
4879 
4880   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4881   RefToScanQueueSet*      queues()         { return _queues; }
4882   ParallelTaskTerminator* terminator()     { return _terminator; }
4883 
4884 public:
4885   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4886                                 G1ParScanThreadState* par_scan_state,
4887                                 RefToScanQueueSet* queues,
4888                                 ParallelTaskTerminator* terminator)
4889     : _g1h(g1h), _par_scan_state(par_scan_state),
4890       _queues(queues), _terminator(terminator) {}
4891 
4892   void do_void();
4893 
4894 private:
4895   inline bool offer_termination();
4896 };
4897 
4898 bool G1ParEvacuateFollowersClosure::offer_termination() {
4899   G1ParScanThreadState* const pss = par_scan_state();
4900   pss->start_term_time();
4901   const bool res = terminator()->offer_termination();
4902   pss->end_term_time();
4903   return res;
4904 }
4905 
4906 void G1ParEvacuateFollowersClosure::do_void() {
4907   StarTask stolen_task;
4908   G1ParScanThreadState* const pss = par_scan_state();
4909   pss->trim_queue();
4910 
4911   do {
4912     while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4913       assert(pss->verify_task(stolen_task), "sanity");
4914       if (stolen_task.is_narrow()) {
4915         pss->deal_with_reference((narrowOop*) stolen_task);
4916       } else {
4917         pss->deal_with_reference((oop*) stolen_task);
4918       }
4919 
4920       // We've just processed a reference and we might have made
4921       // available new entries on the queues. So we have to make sure
4922       // we drain the queues as necessary.
4923       pss->trim_queue();
4924     }
4925   } while (!offer_termination());
4926 }
4927 
4928 class G1KlassScanClosure : public KlassClosure {
4929  G1ParCopyHelper* _closure;
4930  bool             _process_only_dirty;
4931  int              _count;
4932  public:
4933   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4934       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4935   void do_klass(Klass* klass) {
4936     // If the klass has not been dirtied we know that there's
4937     // no references into  the young gen and we can skip it.
4938    if (!_process_only_dirty || klass->has_modified_oops()) {
4939       // Clean the klass since we're going to scavenge all the metadata.
4940       klass->clear_modified_oops();
4941 
4942       // Tell the closure that this klass is the Klass to scavenge
4943       // and is the one to dirty if oops are left pointing into the young gen.
4944       _closure->set_scanned_klass(klass);
4945 
4946       klass->oops_do(_closure);
4947 
4948       _closure->set_scanned_klass(NULL);
4949     }
4950     _count++;
4951   }
4952 };
4953 
4954 class G1ParTask : public AbstractGangTask {
4955 protected:
4956   G1CollectedHeap*       _g1h;
4957   RefToScanQueueSet      *_queues;
4958   ParallelTaskTerminator _terminator;
4959   uint _n_workers;
4960 
4961   Mutex _stats_lock;
4962   Mutex* stats_lock() { return &_stats_lock; }
4963 
4964   size_t getNCards() {
4965     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4966       / G1BlockOffsetSharedArray::N_bytes;
4967   }
4968 
4969 public:
4970   G1ParTask(G1CollectedHeap* g1h,
4971             RefToScanQueueSet *task_queues)
4972     : AbstractGangTask("G1 collection"),
4973       _g1h(g1h),
4974       _queues(task_queues),
4975       _terminator(0, _queues),
4976       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4977   {}
4978 
4979   RefToScanQueueSet* queues() { return _queues; }
4980 
4981   RefToScanQueue *work_queue(int i) {
4982     return queues()->queue(i);
4983   }
4984 
4985   ParallelTaskTerminator* terminator() { return &_terminator; }
4986 
4987   virtual void set_for_termination(int active_workers) {
4988     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4989     // in the young space (_par_seq_tasks) in the G1 heap
4990     // for SequentialSubTasksDone.
4991     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4992     // both of which need setting by set_n_termination().
4993     _g1h->SharedHeap::set_n_termination(active_workers);
4994     _g1h->set_n_termination(active_workers);
4995     terminator()->reset_for_reuse(active_workers);
4996     _n_workers = active_workers;
4997   }
4998 
4999   void work(uint worker_id) {
5000     if (worker_id >= _n_workers) return;  // no work needed this round
5001 
5002     double start_time_ms = os::elapsedTime() * 1000.0;
5003     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
5004 
5005     {
5006       ResourceMark rm;
5007       HandleMark   hm;
5008 
5009       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
5010 
5011       G1ParScanThreadState            pss(_g1h, worker_id, rp);
5012       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
5013 
5014       pss.set_evac_failure_closure(&evac_failure_cl);
5015 
5016       G1ParScanExtRootClosure        only_scan_root_cl(_g1h, &pss, rp);
5017       G1ParScanMetadataClosure       only_scan_metadata_cl(_g1h, &pss, rp);
5018 
5019       G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
5020       G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
5021 
5022       bool only_young                 = _g1h->g1_policy()->gcs_are_young();
5023       G1KlassScanClosure              scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
5024       G1KlassScanClosure              only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
5025 
5026       OopClosure*                    scan_root_cl = &only_scan_root_cl;
5027       G1KlassScanClosure*            scan_klasses_cl = &only_scan_klasses_cl_s;
5028 
5029       if (_g1h->g1_policy()->during_initial_mark_pause()) {
5030         // We also need to mark copied objects.
5031         scan_root_cl = &scan_mark_root_cl;
5032         scan_klasses_cl = &scan_mark_klasses_cl_s;
5033       }
5034 
5035       G1ParPushHeapRSClosure          push_heap_rs_cl(_g1h, &pss);
5036 
5037       // Don't scan the scavengable methods in the code cache as part
5038       // of strong root scanning. The code roots that point into a
5039       // region in the collection set are scanned when we scan the
5040       // region's RSet.
5041       int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
5042 
5043       pss.start_strong_roots();
5044       _g1h->g1_process_strong_roots(/* is scavenging */ true,
5045                                     SharedHeap::ScanningOption(so),
5046                                     scan_root_cl,
5047                                     &push_heap_rs_cl,
5048                                     scan_klasses_cl,
5049                                     worker_id);
5050       pss.end_strong_roots();
5051 
5052       {
5053         double start = os::elapsedTime();
5054         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
5055         evac.do_void();
5056         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
5057         double term_ms = pss.term_time()*1000.0;
5058         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
5059         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
5060       }
5061       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
5062       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
5063 
5064       if (ParallelGCVerbose) {
5065         MutexLocker x(stats_lock());
5066         pss.print_termination_stats(worker_id);
5067       }
5068 
5069       assert(pss.refs()->is_empty(), "should be empty");
5070 
5071       // Close the inner scope so that the ResourceMark and HandleMark
5072       // destructors are executed here and are included as part of the
5073       // "GC Worker Time".
5074     }
5075 
5076     double end_time_ms = os::elapsedTime() * 1000.0;
5077     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5078   }
5079 };
5080 
5081 // *** Common G1 Evacuation Stuff
5082 
5083 // This method is run in a GC worker.
5084 
5085 void
5086 G1CollectedHeap::
5087 g1_process_strong_roots(bool is_scavenging,
5088                         ScanningOption so,
5089                         OopClosure* scan_non_heap_roots,
5090                         OopsInHeapRegionClosure* scan_rs,
5091                         G1KlassScanClosure* scan_klasses,
5092                         uint worker_i) {
5093 
5094   // First scan the strong roots
5095   double ext_roots_start = os::elapsedTime();
5096   double closure_app_time_sec = 0.0;
5097 
5098   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5099 
5100   process_strong_roots(false, // no scoping; this is parallel code
5101                        so,
5102                        &buf_scan_non_heap_roots,
5103                        scan_klasses
5104                        );
5105 
5106   // Now the CM ref_processor roots.
5107   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5108     // We need to treat the discovered reference lists of the
5109     // concurrent mark ref processor as roots and keep entries
5110     // (which are added by the marking threads) on them live
5111     // until they can be processed at the end of marking.
5112     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5113   }
5114 
5115   // Finish up any enqueued closure apps (attributed as object copy time).
5116   buf_scan_non_heap_roots.done();
5117 
5118   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5119 
5120   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5121 
5122   double ext_root_time_ms =
5123     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5124 
5125   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5126 
5127   // During conc marking we have to filter the per-thread SATB buffers
5128   // to make sure we remove any oops into the CSet (which will show up
5129   // as implicitly live).
5130   double satb_filtering_ms = 0.0;
5131   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5132     if (mark_in_progress()) {
5133       double satb_filter_start = os::elapsedTime();
5134 
5135       JavaThread::satb_mark_queue_set().filter_thread_buffers();
5136 
5137       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5138     }
5139   }
5140   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5141 
5142   // If this is an initial mark pause, and we're not scanning
5143   // the entire code cache, we need to mark the oops in the
5144   // strong code root lists for the regions that are not in
5145   // the collection set.
5146   // Note all threads participate in this set of root tasks.
5147   double mark_strong_code_roots_ms = 0.0;
5148   if (g1_policy()->during_initial_mark_pause() && !(so & SO_AllCodeCache)) {
5149     double mark_strong_roots_start = os::elapsedTime();
5150     mark_strong_code_roots(worker_i);
5151     mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
5152   }
5153   g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
5154 
5155   // Now scan the complement of the collection set.
5156   CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
5157   g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
5158 
5159   _process_strong_tasks->all_tasks_completed();
5160 }
5161 
5162 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
5163 private:
5164   BoolObjectClosure* _is_alive;
5165   int _initial_string_table_size;
5166   int _initial_symbol_table_size;
5167 
5168   bool  _process_strings;
5169   int _strings_processed;
5170   int _strings_removed;
5171 
5172   bool  _process_symbols;
5173   int _symbols_processed;
5174   int _symbols_removed;
5175 
5176   bool _do_in_parallel;
5177 public:
5178   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
5179     AbstractGangTask("Par String/Symbol table unlink"), _is_alive(is_alive),
5180     _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
5181     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
5182     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
5183 
5184     _initial_string_table_size = StringTable::the_table()->table_size();
5185     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
5186     if (process_strings) {
5187       StringTable::clear_parallel_claimed_index();
5188     }
5189     if (process_symbols) {
5190       SymbolTable::clear_parallel_claimed_index();
5191     }
5192   }
5193 
5194   ~G1StringSymbolTableUnlinkTask() {
5195     guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
5196               err_msg("claim value %d after unlink less than initial string table size %d",
5197                       StringTable::parallel_claimed_index(), _initial_string_table_size));
5198     guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
5199               err_msg("claim value %d after unlink less than initial symbol table size %d",
5200                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
5201   }
5202 
5203   void work(uint worker_id) {
5204     if (_do_in_parallel) {
5205       int strings_processed = 0;
5206       int strings_removed = 0;
5207       int symbols_processed = 0;
5208       int symbols_removed = 0;
5209       if (_process_strings) {
5210         StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5211         Atomic::add(strings_processed, &_strings_processed);
5212         Atomic::add(strings_removed, &_strings_removed);
5213       }
5214       if (_process_symbols) {
5215         SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5216         Atomic::add(symbols_processed, &_symbols_processed);
5217         Atomic::add(symbols_removed, &_symbols_removed);
5218       }
5219     } else {
5220       if (_process_strings) {
5221         StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5222       }
5223       if (_process_symbols) {
5224         SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5225       }
5226     }
5227   }
5228 
5229   size_t strings_processed() const { return (size_t)_strings_processed; }
5230   size_t strings_removed()   const { return (size_t)_strings_removed; }
5231 
5232   size_t symbols_processed() const { return (size_t)_symbols_processed; }
5233   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
5234 };
5235 
5236 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5237                                                      bool process_strings, bool process_symbols) {
5238   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5239                    _g1h->workers()->active_workers() : 1);
5240 
5241   G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5242   if (G1CollectedHeap::use_parallel_gc_threads()) {
5243     set_par_threads(n_workers);
5244     workers()->run_task(&g1_unlink_task);
5245     set_par_threads(0);
5246   } else {
5247     g1_unlink_task.work(0);
5248   }
5249   if (G1TraceStringSymbolTableScrubbing) {
5250     gclog_or_tty->print_cr("Cleaned string and symbol table, "
5251                            "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5252                            "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5253                            g1_unlink_task.strings_processed(), g1_unlink_task.strings_removed(),
5254                            g1_unlink_task.symbols_processed(), g1_unlink_task.symbols_removed());
5255   }
5256 
5257   if (G1StringDedup::is_enabled()) {
5258     G1StringDedup::unlink(is_alive);
5259   }
5260 }
5261 
5262 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5263  private:
5264   DirtyCardQueueSet* _queue;
5265  public:
5266   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5267 
5268   virtual void work(uint worker_id) {
5269     double start_time = os::elapsedTime();
5270 
5271     RedirtyLoggedCardTableEntryClosure cl;
5272     if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5273       _queue->par_apply_closure_to_all_completed_buffers(&cl);
5274     } else {
5275       _queue->apply_closure_to_all_completed_buffers(&cl);
5276     }
5277 
5278     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5279     timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5280     timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5281   }
5282 };
5283 
5284 void G1CollectedHeap::redirty_logged_cards() {
5285   guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5286   double redirty_logged_cards_start = os::elapsedTime();
5287 
5288   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5289                    _g1h->workers()->active_workers() : 1);
5290 
5291   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5292   dirty_card_queue_set().reset_for_par_iteration();
5293   if (use_parallel_gc_threads()) {
5294     set_par_threads(n_workers);
5295     workers()->run_task(&redirty_task);
5296     set_par_threads(0);
5297   } else {
5298     redirty_task.work(0);
5299   }
5300 
5301   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5302   dcq.merge_bufferlists(&dirty_card_queue_set());
5303   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5304 
5305   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5306 }
5307 
5308 // Weak Reference Processing support
5309 
5310 // An always "is_alive" closure that is used to preserve referents.
5311 // If the object is non-null then it's alive.  Used in the preservation
5312 // of referent objects that are pointed to by reference objects
5313 // discovered by the CM ref processor.
5314 class G1AlwaysAliveClosure: public BoolObjectClosure {
5315   G1CollectedHeap* _g1;
5316 public:
5317   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5318   bool do_object_b(oop p) {
5319     if (p != NULL) {
5320       return true;
5321     }
5322     return false;
5323   }
5324 };
5325 
5326 bool G1STWIsAliveClosure::do_object_b(oop p) {
5327   // An object is reachable if it is outside the collection set,
5328   // or is inside and copied.
5329   return !_g1->obj_in_cs(p) || p->is_forwarded();
5330 }
5331 
5332 // Non Copying Keep Alive closure
5333 class G1KeepAliveClosure: public OopClosure {
5334   G1CollectedHeap* _g1;
5335 public:
5336   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5337   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5338   void do_oop(      oop* p) {
5339     oop obj = *p;
5340 
5341     if (_g1->obj_in_cs(obj)) {
5342       assert( obj->is_forwarded(), "invariant" );
5343       *p = obj->forwardee();
5344     }
5345   }
5346 };
5347 
5348 // Copying Keep Alive closure - can be called from both
5349 // serial and parallel code as long as different worker
5350 // threads utilize different G1ParScanThreadState instances
5351 // and different queues.
5352 
5353 class G1CopyingKeepAliveClosure: public OopClosure {
5354   G1CollectedHeap*         _g1h;
5355   OopClosure*              _copy_non_heap_obj_cl;
5356   OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5357   G1ParScanThreadState*    _par_scan_state;
5358 
5359 public:
5360   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5361                             OopClosure* non_heap_obj_cl,
5362                             OopsInHeapRegionClosure* metadata_obj_cl,
5363                             G1ParScanThreadState* pss):
5364     _g1h(g1h),
5365     _copy_non_heap_obj_cl(non_heap_obj_cl),
5366     _copy_metadata_obj_cl(metadata_obj_cl),
5367     _par_scan_state(pss)
5368   {}
5369 
5370   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5371   virtual void do_oop(      oop* p) { do_oop_work(p); }
5372 
5373   template <class T> void do_oop_work(T* p) {
5374     oop obj = oopDesc::load_decode_heap_oop(p);
5375 
5376     if (_g1h->obj_in_cs(obj)) {
5377       // If the referent object has been forwarded (either copied
5378       // to a new location or to itself in the event of an
5379       // evacuation failure) then we need to update the reference
5380       // field and, if both reference and referent are in the G1
5381       // heap, update the RSet for the referent.
5382       //
5383       // If the referent has not been forwarded then we have to keep
5384       // it alive by policy. Therefore we have copy the referent.
5385       //
5386       // If the reference field is in the G1 heap then we can push
5387       // on the PSS queue. When the queue is drained (after each
5388       // phase of reference processing) the object and it's followers
5389       // will be copied, the reference field set to point to the
5390       // new location, and the RSet updated. Otherwise we need to
5391       // use the the non-heap or metadata closures directly to copy
5392       // the referent object and update the pointer, while avoiding
5393       // updating the RSet.
5394 
5395       if (_g1h->is_in_g1_reserved(p)) {
5396         _par_scan_state->push_on_queue(p);
5397       } else {
5398         assert(!ClassLoaderDataGraph::contains((address)p),
5399                err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5400                               PTR_FORMAT, p));
5401           _copy_non_heap_obj_cl->do_oop(p);
5402         }
5403       }
5404     }
5405 };
5406 
5407 // Serial drain queue closure. Called as the 'complete_gc'
5408 // closure for each discovered list in some of the
5409 // reference processing phases.
5410 
5411 class G1STWDrainQueueClosure: public VoidClosure {
5412 protected:
5413   G1CollectedHeap* _g1h;
5414   G1ParScanThreadState* _par_scan_state;
5415 
5416   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5417 
5418 public:
5419   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5420     _g1h(g1h),
5421     _par_scan_state(pss)
5422   { }
5423 
5424   void do_void() {
5425     G1ParScanThreadState* const pss = par_scan_state();
5426     pss->trim_queue();
5427   }
5428 };
5429 
5430 // Parallel Reference Processing closures
5431 
5432 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5433 // processing during G1 evacuation pauses.
5434 
5435 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5436 private:
5437   G1CollectedHeap*   _g1h;
5438   RefToScanQueueSet* _queues;
5439   FlexibleWorkGang*  _workers;
5440   int                _active_workers;
5441 
5442 public:
5443   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5444                         FlexibleWorkGang* workers,
5445                         RefToScanQueueSet *task_queues,
5446                         int n_workers) :
5447     _g1h(g1h),
5448     _queues(task_queues),
5449     _workers(workers),
5450     _active_workers(n_workers)
5451   {
5452     assert(n_workers > 0, "shouldn't call this otherwise");
5453   }
5454 
5455   // Executes the given task using concurrent marking worker threads.
5456   virtual void execute(ProcessTask& task);
5457   virtual void execute(EnqueueTask& task);
5458 };
5459 
5460 // Gang task for possibly parallel reference processing
5461 
5462 class G1STWRefProcTaskProxy: public AbstractGangTask {
5463   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5464   ProcessTask&     _proc_task;
5465   G1CollectedHeap* _g1h;
5466   RefToScanQueueSet *_task_queues;
5467   ParallelTaskTerminator* _terminator;
5468 
5469 public:
5470   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5471                      G1CollectedHeap* g1h,
5472                      RefToScanQueueSet *task_queues,
5473                      ParallelTaskTerminator* terminator) :
5474     AbstractGangTask("Process reference objects in parallel"),
5475     _proc_task(proc_task),
5476     _g1h(g1h),
5477     _task_queues(task_queues),
5478     _terminator(terminator)
5479   {}
5480 
5481   virtual void work(uint worker_id) {
5482     // The reference processing task executed by a single worker.
5483     ResourceMark rm;
5484     HandleMark   hm;
5485 
5486     G1STWIsAliveClosure is_alive(_g1h);
5487 
5488     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5489     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5490 
5491     pss.set_evac_failure_closure(&evac_failure_cl);
5492 
5493     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5494     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5495 
5496     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5497     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5498 
5499     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5500     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5501 
5502     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5503       // We also need to mark copied objects.
5504       copy_non_heap_cl = &copy_mark_non_heap_cl;
5505       copy_metadata_cl = &copy_mark_metadata_cl;
5506     }
5507 
5508     // Keep alive closure.
5509     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5510 
5511     // Complete GC closure
5512     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5513 
5514     // Call the reference processing task's work routine.
5515     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5516 
5517     // Note we cannot assert that the refs array is empty here as not all
5518     // of the processing tasks (specifically phase2 - pp2_work) execute
5519     // the complete_gc closure (which ordinarily would drain the queue) so
5520     // the queue may not be empty.
5521   }
5522 };
5523 
5524 // Driver routine for parallel reference processing.
5525 // Creates an instance of the ref processing gang
5526 // task and has the worker threads execute it.
5527 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5528   assert(_workers != NULL, "Need parallel worker threads.");
5529 
5530   ParallelTaskTerminator terminator(_active_workers, _queues);
5531   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5532 
5533   _g1h->set_par_threads(_active_workers);
5534   _workers->run_task(&proc_task_proxy);
5535   _g1h->set_par_threads(0);
5536 }
5537 
5538 // Gang task for parallel reference enqueueing.
5539 
5540 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5541   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5542   EnqueueTask& _enq_task;
5543 
5544 public:
5545   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5546     AbstractGangTask("Enqueue reference objects in parallel"),
5547     _enq_task(enq_task)
5548   { }
5549 
5550   virtual void work(uint worker_id) {
5551     _enq_task.work(worker_id);
5552   }
5553 };
5554 
5555 // Driver routine for parallel reference enqueueing.
5556 // Creates an instance of the ref enqueueing gang
5557 // task and has the worker threads execute it.
5558 
5559 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5560   assert(_workers != NULL, "Need parallel worker threads.");
5561 
5562   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5563 
5564   _g1h->set_par_threads(_active_workers);
5565   _workers->run_task(&enq_task_proxy);
5566   _g1h->set_par_threads(0);
5567 }
5568 
5569 // End of weak reference support closures
5570 
5571 // Abstract task used to preserve (i.e. copy) any referent objects
5572 // that are in the collection set and are pointed to by reference
5573 // objects discovered by the CM ref processor.
5574 
5575 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5576 protected:
5577   G1CollectedHeap* _g1h;
5578   RefToScanQueueSet      *_queues;
5579   ParallelTaskTerminator _terminator;
5580   uint _n_workers;
5581 
5582 public:
5583   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5584     AbstractGangTask("ParPreserveCMReferents"),
5585     _g1h(g1h),
5586     _queues(task_queues),
5587     _terminator(workers, _queues),
5588     _n_workers(workers)
5589   { }
5590 
5591   void work(uint worker_id) {
5592     ResourceMark rm;
5593     HandleMark   hm;
5594 
5595     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5596     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5597 
5598     pss.set_evac_failure_closure(&evac_failure_cl);
5599 
5600     assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5601 
5602 
5603     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5604     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5605 
5606     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5607     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5608 
5609     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5610     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5611 
5612     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5613       // We also need to mark copied objects.
5614       copy_non_heap_cl = &copy_mark_non_heap_cl;
5615       copy_metadata_cl = &copy_mark_metadata_cl;
5616     }
5617 
5618     // Is alive closure
5619     G1AlwaysAliveClosure always_alive(_g1h);
5620 
5621     // Copying keep alive closure. Applied to referent objects that need
5622     // to be copied.
5623     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5624 
5625     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5626 
5627     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5628     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5629 
5630     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5631     // So this must be true - but assert just in case someone decides to
5632     // change the worker ids.
5633     assert(0 <= worker_id && worker_id < limit, "sanity");
5634     assert(!rp->discovery_is_atomic(), "check this code");
5635 
5636     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5637     for (uint idx = worker_id; idx < limit; idx += stride) {
5638       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5639 
5640       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5641       while (iter.has_next()) {
5642         // Since discovery is not atomic for the CM ref processor, we
5643         // can see some null referent objects.
5644         iter.load_ptrs(DEBUG_ONLY(true));
5645         oop ref = iter.obj();
5646 
5647         // This will filter nulls.
5648         if (iter.is_referent_alive()) {
5649           iter.make_referent_alive();
5650         }
5651         iter.move_to_next();
5652       }
5653     }
5654 
5655     // Drain the queue - which may cause stealing
5656     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5657     drain_queue.do_void();
5658     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5659     assert(pss.refs()->is_empty(), "should be");
5660   }
5661 };
5662 
5663 // Weak Reference processing during an evacuation pause (part 1).
5664 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5665   double ref_proc_start = os::elapsedTime();
5666 
5667   ReferenceProcessor* rp = _ref_processor_stw;
5668   assert(rp->discovery_enabled(), "should have been enabled");
5669 
5670   // Any reference objects, in the collection set, that were 'discovered'
5671   // by the CM ref processor should have already been copied (either by
5672   // applying the external root copy closure to the discovered lists, or
5673   // by following an RSet entry).
5674   //
5675   // But some of the referents, that are in the collection set, that these
5676   // reference objects point to may not have been copied: the STW ref
5677   // processor would have seen that the reference object had already
5678   // been 'discovered' and would have skipped discovering the reference,
5679   // but would not have treated the reference object as a regular oop.
5680   // As a result the copy closure would not have been applied to the
5681   // referent object.
5682   //
5683   // We need to explicitly copy these referent objects - the references
5684   // will be processed at the end of remarking.
5685   //
5686   // We also need to do this copying before we process the reference
5687   // objects discovered by the STW ref processor in case one of these
5688   // referents points to another object which is also referenced by an
5689   // object discovered by the STW ref processor.
5690 
5691   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5692            no_of_gc_workers == workers()->active_workers(),
5693            "Need to reset active GC workers");
5694 
5695   set_par_threads(no_of_gc_workers);
5696   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5697                                                  no_of_gc_workers,
5698                                                  _task_queues);
5699 
5700   if (G1CollectedHeap::use_parallel_gc_threads()) {
5701     workers()->run_task(&keep_cm_referents);
5702   } else {
5703     keep_cm_referents.work(0);
5704   }
5705 
5706   set_par_threads(0);
5707 
5708   // Closure to test whether a referent is alive.
5709   G1STWIsAliveClosure is_alive(this);
5710 
5711   // Even when parallel reference processing is enabled, the processing
5712   // of JNI refs is serial and performed serially by the current thread
5713   // rather than by a worker. The following PSS will be used for processing
5714   // JNI refs.
5715 
5716   // Use only a single queue for this PSS.
5717   G1ParScanThreadState            pss(this, 0, NULL);
5718 
5719   // We do not embed a reference processor in the copying/scanning
5720   // closures while we're actually processing the discovered
5721   // reference objects.
5722   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5723 
5724   pss.set_evac_failure_closure(&evac_failure_cl);
5725 
5726   assert(pss.refs()->is_empty(), "pre-condition");
5727 
5728   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5729   G1ParScanMetadataClosure       only_copy_metadata_cl(this, &pss, NULL);
5730 
5731   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5732   G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5733 
5734   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5735   OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5736 
5737   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5738     // We also need to mark copied objects.
5739     copy_non_heap_cl = &copy_mark_non_heap_cl;
5740     copy_metadata_cl = &copy_mark_metadata_cl;
5741   }
5742 
5743   // Keep alive closure.
5744   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5745 
5746   // Serial Complete GC closure
5747   G1STWDrainQueueClosure drain_queue(this, &pss);
5748 
5749   // Setup the soft refs policy...
5750   rp->setup_policy(false);
5751 
5752   ReferenceProcessorStats stats;
5753   if (!rp->processing_is_mt()) {
5754     // Serial reference processing...
5755     stats = rp->process_discovered_references(&is_alive,
5756                                               &keep_alive,
5757                                               &drain_queue,
5758                                               NULL,
5759                                               _gc_timer_stw);
5760   } else {
5761     // Parallel reference processing
5762     assert(rp->num_q() == no_of_gc_workers, "sanity");
5763     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5764 
5765     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5766     stats = rp->process_discovered_references(&is_alive,
5767                                               &keep_alive,
5768                                               &drain_queue,
5769                                               &par_task_executor,
5770                                               _gc_timer_stw);
5771   }
5772 
5773   _gc_tracer_stw->report_gc_reference_stats(stats);
5774 
5775   // We have completed copying any necessary live referent objects.
5776   assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5777 
5778   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5779   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5780 }
5781 
5782 // Weak Reference processing during an evacuation pause (part 2).
5783 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5784   double ref_enq_start = os::elapsedTime();
5785 
5786   ReferenceProcessor* rp = _ref_processor_stw;
5787   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5788 
5789   // Now enqueue any remaining on the discovered lists on to
5790   // the pending list.
5791   if (!rp->processing_is_mt()) {
5792     // Serial reference processing...
5793     rp->enqueue_discovered_references();
5794   } else {
5795     // Parallel reference enqueueing
5796 
5797     assert(no_of_gc_workers == workers()->active_workers(),
5798            "Need to reset active workers");
5799     assert(rp->num_q() == no_of_gc_workers, "sanity");
5800     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5801 
5802     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5803     rp->enqueue_discovered_references(&par_task_executor);
5804   }
5805 
5806   rp->verify_no_references_recorded();
5807   assert(!rp->discovery_enabled(), "should have been disabled");
5808 
5809   // FIXME
5810   // CM's reference processing also cleans up the string and symbol tables.
5811   // Should we do that here also? We could, but it is a serial operation
5812   // and could significantly increase the pause time.
5813 
5814   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5815   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5816 }
5817 
5818 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5819   _expand_heap_after_alloc_failure = true;
5820   _evacuation_failed = false;
5821 
5822   // Should G1EvacuationFailureALot be in effect for this GC?
5823   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5824 
5825   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5826 
5827   // Disable the hot card cache.
5828   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5829   hot_card_cache->reset_hot_cache_claimed_index();
5830   hot_card_cache->set_use_cache(false);
5831 
5832   uint n_workers;
5833   if (G1CollectedHeap::use_parallel_gc_threads()) {
5834     n_workers =
5835       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5836                                      workers()->active_workers(),
5837                                      Threads::number_of_non_daemon_threads());
5838     assert(UseDynamicNumberOfGCThreads ||
5839            n_workers == workers()->total_workers(),
5840            "If not dynamic should be using all the  workers");
5841     workers()->set_active_workers(n_workers);
5842     set_par_threads(n_workers);
5843   } else {
5844     assert(n_par_threads() == 0,
5845            "Should be the original non-parallel value");
5846     n_workers = 1;
5847   }
5848 
5849   G1ParTask g1_par_task(this, _task_queues);
5850 
5851   init_for_evac_failure(NULL);
5852 
5853   rem_set()->prepare_for_younger_refs_iterate(true);
5854 
5855   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5856   double start_par_time_sec = os::elapsedTime();
5857   double end_par_time_sec;
5858 
5859   {
5860     StrongRootsScope srs(this);
5861 
5862     if (G1CollectedHeap::use_parallel_gc_threads()) {
5863       // The individual threads will set their evac-failure closures.
5864       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5865       // These tasks use ShareHeap::_process_strong_tasks
5866       assert(UseDynamicNumberOfGCThreads ||
5867              workers()->active_workers() == workers()->total_workers(),
5868              "If not dynamic should be using all the  workers");
5869       workers()->run_task(&g1_par_task);
5870     } else {
5871       g1_par_task.set_for_termination(n_workers);
5872       g1_par_task.work(0);
5873     }
5874     end_par_time_sec = os::elapsedTime();
5875 
5876     // Closing the inner scope will execute the destructor
5877     // for the StrongRootsScope object. We record the current
5878     // elapsed time before closing the scope so that time
5879     // taken for the SRS destructor is NOT included in the
5880     // reported parallel time.
5881   }
5882 
5883   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5884   g1_policy()->phase_times()->record_par_time(par_time_ms);
5885 
5886   double code_root_fixup_time_ms =
5887         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5888   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5889 
5890   set_par_threads(0);
5891 
5892   // Process any discovered reference objects - we have
5893   // to do this _before_ we retire the GC alloc regions
5894   // as we may have to copy some 'reachable' referent
5895   // objects (and their reachable sub-graphs) that were
5896   // not copied during the pause.
5897   process_discovered_references(n_workers);
5898 
5899   // Weak root processing.
5900   {
5901     G1STWIsAliveClosure is_alive(this);
5902     G1KeepAliveClosure keep_alive(this);
5903     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5904     if (G1StringDedup::is_enabled()) {
5905       G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5906     }
5907   }
5908 
5909   release_gc_alloc_regions(n_workers, evacuation_info);
5910   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5911 
5912   // Reset and re-enable the hot card cache.
5913   // Note the counts for the cards in the regions in the
5914   // collection set are reset when the collection set is freed.
5915   hot_card_cache->reset_hot_cache();
5916   hot_card_cache->set_use_cache(true);
5917 
5918   // Migrate the strong code roots attached to each region in
5919   // the collection set. Ideally we would like to do this
5920   // after we have finished the scanning/evacuation of the
5921   // strong code roots for a particular heap region.
5922   migrate_strong_code_roots();
5923 
5924   purge_code_root_memory();
5925 
5926   if (g1_policy()->during_initial_mark_pause()) {
5927     // Reset the claim values set during marking the strong code roots
5928     reset_heap_region_claim_values();
5929   }
5930 
5931   finalize_for_evac_failure();
5932 
5933   if (evacuation_failed()) {
5934     remove_self_forwarding_pointers();
5935 
5936     // Reset the G1EvacuationFailureALot counters and flags
5937     // Note: the values are reset only when an actual
5938     // evacuation failure occurs.
5939     NOT_PRODUCT(reset_evacuation_should_fail();)
5940   }
5941 
5942   // Enqueue any remaining references remaining on the STW
5943   // reference processor's discovered lists. We need to do
5944   // this after the card table is cleaned (and verified) as
5945   // the act of enqueueing entries on to the pending list
5946   // will log these updates (and dirty their associated
5947   // cards). We need these updates logged to update any
5948   // RSets.
5949   enqueue_discovered_references(n_workers);
5950 
5951   if (G1DeferredRSUpdate) {
5952     redirty_logged_cards();
5953   }
5954   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5955 }
5956 
5957 void G1CollectedHeap::free_region(HeapRegion* hr,
5958                                   FreeRegionList* free_list,
5959                                   bool par,
5960                                   bool locked) {
5961   assert(!hr->isHumongous(), "this is only for non-humongous regions");
5962   assert(!hr->is_empty(), "the region should not be empty");
5963   assert(free_list != NULL, "pre-condition");
5964 
5965   if (G1VerifyBitmaps) {
5966     MemRegion mr(hr->bottom(), hr->end());
5967     concurrent_mark()->clearRangePrevBitmap(mr);
5968   }
5969 
5970   // Clear the card counts for this region.
5971   // Note: we only need to do this if the region is not young
5972   // (since we don't refine cards in young regions).
5973   if (!hr->is_young()) {
5974     _cg1r->hot_card_cache()->reset_card_counts(hr);
5975   }
5976   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5977   free_list->add_ordered(hr);
5978 }
5979 
5980 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5981                                      FreeRegionList* free_list,
5982                                      bool par) {
5983   assert(hr->startsHumongous(), "this is only for starts humongous regions");
5984   assert(free_list != NULL, "pre-condition");
5985 
5986   size_t hr_capacity = hr->capacity();
5987   // We need to read this before we make the region non-humongous,
5988   // otherwise the information will be gone.
5989   uint last_index = hr->last_hc_index();
5990   hr->set_notHumongous();
5991   free_region(hr, free_list, par);
5992 
5993   uint i = hr->hrs_index() + 1;
5994   while (i < last_index) {
5995     HeapRegion* curr_hr = region_at(i);
5996     assert(curr_hr->continuesHumongous(), "invariant");
5997     curr_hr->set_notHumongous();
5998     free_region(curr_hr, free_list, par);
5999     i += 1;
6000   }
6001 }
6002 
6003 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6004                                        const HeapRegionSetCount& humongous_regions_removed) {
6005   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6006     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6007     _old_set.bulk_remove(old_regions_removed);
6008     _humongous_set.bulk_remove(humongous_regions_removed);
6009   }
6010 
6011 }
6012 
6013 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6014   assert(list != NULL, "list can't be null");
6015   if (!list->is_empty()) {
6016     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6017     _free_list.add_ordered(list);
6018   }
6019 }
6020 
6021 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6022   assert(_summary_bytes_used >= bytes,
6023          err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
6024                   _summary_bytes_used, bytes));
6025   _summary_bytes_used -= bytes;
6026 }
6027 
6028 class G1ParCleanupCTTask : public AbstractGangTask {
6029   G1SATBCardTableModRefBS* _ct_bs;
6030   G1CollectedHeap* _g1h;
6031   HeapRegion* volatile _su_head;
6032 public:
6033   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6034                      G1CollectedHeap* g1h) :
6035     AbstractGangTask("G1 Par Cleanup CT Task"),
6036     _ct_bs(ct_bs), _g1h(g1h) { }
6037 
6038   void work(uint worker_id) {
6039     HeapRegion* r;
6040     while (r = _g1h->pop_dirty_cards_region()) {
6041       clear_cards(r);
6042     }
6043   }
6044 
6045   void clear_cards(HeapRegion* r) {
6046     // Cards of the survivors should have already been dirtied.
6047     if (!r->is_survivor()) {
6048       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6049     }
6050   }
6051 };
6052 
6053 #ifndef PRODUCT
6054 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6055   G1CollectedHeap* _g1h;
6056   G1SATBCardTableModRefBS* _ct_bs;
6057 public:
6058   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6059     : _g1h(g1h), _ct_bs(ct_bs) { }
6060   virtual bool doHeapRegion(HeapRegion* r) {
6061     if (r->is_survivor()) {
6062       _g1h->verify_dirty_region(r);
6063     } else {
6064       _g1h->verify_not_dirty_region(r);
6065     }
6066     return false;
6067   }
6068 };
6069 
6070 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6071   // All of the region should be clean.
6072   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6073   MemRegion mr(hr->bottom(), hr->end());
6074   ct_bs->verify_not_dirty_region(mr);
6075 }
6076 
6077 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6078   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
6079   // dirty allocated blocks as they allocate them. The thread that
6080   // retires each region and replaces it with a new one will do a
6081   // maximal allocation to fill in [pre_dummy_top(),end()] but will
6082   // not dirty that area (one less thing to have to do while holding
6083   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6084   // is dirty.
6085   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6086   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6087   if (hr->is_young()) {
6088     ct_bs->verify_g1_young_region(mr);
6089   } else {
6090     ct_bs->verify_dirty_region(mr);
6091   }
6092 }
6093 
6094 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6095   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6096   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6097     verify_dirty_region(hr);
6098   }
6099 }
6100 
6101 void G1CollectedHeap::verify_dirty_young_regions() {
6102   verify_dirty_young_list(_young_list->first_region());
6103 }
6104 
6105 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6106                                                HeapWord* tams, HeapWord* end) {
6107   guarantee(tams <= end,
6108             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6109   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6110   if (result < end) {
6111     gclog_or_tty->cr();
6112     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6113                            bitmap_name, result);
6114     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6115                            bitmap_name, tams, end);
6116     return false;
6117   }
6118   return true;
6119 }
6120 
6121 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6122   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6123   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6124 
6125   HeapWord* bottom = hr->bottom();
6126   HeapWord* ptams  = hr->prev_top_at_mark_start();
6127   HeapWord* ntams  = hr->next_top_at_mark_start();
6128   HeapWord* end    = hr->end();
6129 
6130   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6131 
6132   bool res_n = true;
6133   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6134   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6135   // if we happen to be in that state.
6136   if (mark_in_progress() || !_cmThread->in_progress()) {
6137     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6138   }
6139   if (!res_p || !res_n) {
6140     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6141                            HR_FORMAT_PARAMS(hr));
6142     gclog_or_tty->print_cr("#### Caller: %s", caller);
6143     return false;
6144   }
6145   return true;
6146 }
6147 
6148 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6149   if (!G1VerifyBitmaps) return;
6150 
6151   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6152 }
6153 
6154 class G1VerifyBitmapClosure : public HeapRegionClosure {
6155 private:
6156   const char* _caller;
6157   G1CollectedHeap* _g1h;
6158   bool _failures;
6159 
6160 public:
6161   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6162     _caller(caller), _g1h(g1h), _failures(false) { }
6163 
6164   bool failures() { return _failures; }
6165 
6166   virtual bool doHeapRegion(HeapRegion* hr) {
6167     if (hr->continuesHumongous()) return false;
6168 
6169     bool result = _g1h->verify_bitmaps(_caller, hr);
6170     if (!result) {
6171       _failures = true;
6172     }
6173     return false;
6174   }
6175 };
6176 
6177 void G1CollectedHeap::check_bitmaps(const char* caller) {
6178   if (!G1VerifyBitmaps) return;
6179 
6180   G1VerifyBitmapClosure cl(caller, this);
6181   heap_region_iterate(&cl);
6182   guarantee(!cl.failures(), "bitmap verification");
6183 }
6184 #endif // PRODUCT
6185 
6186 void G1CollectedHeap::cleanUpCardTable() {
6187   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6188   double start = os::elapsedTime();
6189 
6190   {
6191     // Iterate over the dirty cards region list.
6192     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6193 
6194     if (G1CollectedHeap::use_parallel_gc_threads()) {
6195       set_par_threads();
6196       workers()->run_task(&cleanup_task);
6197       set_par_threads(0);
6198     } else {
6199       while (_dirty_cards_region_list) {
6200         HeapRegion* r = _dirty_cards_region_list;
6201         cleanup_task.clear_cards(r);
6202         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6203         if (_dirty_cards_region_list == r) {
6204           // The last region.
6205           _dirty_cards_region_list = NULL;
6206         }
6207         r->set_next_dirty_cards_region(NULL);
6208       }
6209     }
6210 #ifndef PRODUCT
6211     if (G1VerifyCTCleanup || VerifyAfterGC) {
6212       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6213       heap_region_iterate(&cleanup_verifier);
6214     }
6215 #endif
6216   }
6217 
6218   double elapsed = os::elapsedTime() - start;
6219   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6220 }
6221 
6222 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6223   size_t pre_used = 0;
6224   FreeRegionList local_free_list("Local List for CSet Freeing");
6225 
6226   double young_time_ms     = 0.0;
6227   double non_young_time_ms = 0.0;
6228 
6229   // Since the collection set is a superset of the the young list,
6230   // all we need to do to clear the young list is clear its
6231   // head and length, and unlink any young regions in the code below
6232   _young_list->clear();
6233 
6234   G1CollectorPolicy* policy = g1_policy();
6235 
6236   double start_sec = os::elapsedTime();
6237   bool non_young = true;
6238 
6239   HeapRegion* cur = cs_head;
6240   int age_bound = -1;
6241   size_t rs_lengths = 0;
6242 
6243   while (cur != NULL) {
6244     assert(!is_on_master_free_list(cur), "sanity");
6245     if (non_young) {
6246       if (cur->is_young()) {
6247         double end_sec = os::elapsedTime();
6248         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6249         non_young_time_ms += elapsed_ms;
6250 
6251         start_sec = os::elapsedTime();
6252         non_young = false;
6253       }
6254     } else {
6255       if (!cur->is_young()) {
6256         double end_sec = os::elapsedTime();
6257         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6258         young_time_ms += elapsed_ms;
6259 
6260         start_sec = os::elapsedTime();
6261         non_young = true;
6262       }
6263     }
6264 
6265     rs_lengths += cur->rem_set()->occupied_locked();
6266 
6267     HeapRegion* next = cur->next_in_collection_set();
6268     assert(cur->in_collection_set(), "bad CS");
6269     cur->set_next_in_collection_set(NULL);
6270     cur->set_in_collection_set(false);
6271 
6272     if (cur->is_young()) {
6273       int index = cur->young_index_in_cset();
6274       assert(index != -1, "invariant");
6275       assert((uint) index < policy->young_cset_region_length(), "invariant");
6276       size_t words_survived = _surviving_young_words[index];
6277       cur->record_surv_words_in_group(words_survived);
6278 
6279       // At this point the we have 'popped' cur from the collection set
6280       // (linked via next_in_collection_set()) but it is still in the
6281       // young list (linked via next_young_region()). Clear the
6282       // _next_young_region field.
6283       cur->set_next_young_region(NULL);
6284     } else {
6285       int index = cur->young_index_in_cset();
6286       assert(index == -1, "invariant");
6287     }
6288 
6289     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6290             (!cur->is_young() && cur->young_index_in_cset() == -1),
6291             "invariant" );
6292 
6293     if (!cur->evacuation_failed()) {
6294       MemRegion used_mr = cur->used_region();
6295 
6296       // And the region is empty.
6297       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6298       pre_used += cur->used();
6299       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6300     } else {
6301       cur->uninstall_surv_rate_group();
6302       if (cur->is_young()) {
6303         cur->set_young_index_in_cset(-1);
6304       }
6305       cur->set_not_young();
6306       cur->set_evacuation_failed(false);
6307       // The region is now considered to be old.
6308       _old_set.add(cur);
6309       evacuation_info.increment_collectionset_used_after(cur->used());
6310     }
6311     cur = next;
6312   }
6313 
6314   evacuation_info.set_regions_freed(local_free_list.length());
6315   policy->record_max_rs_lengths(rs_lengths);
6316   policy->cset_regions_freed();
6317 
6318   double end_sec = os::elapsedTime();
6319   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6320 
6321   if (non_young) {
6322     non_young_time_ms += elapsed_ms;
6323   } else {
6324     young_time_ms += elapsed_ms;
6325   }
6326 
6327   prepend_to_freelist(&local_free_list);
6328   decrement_summary_bytes(pre_used);
6329   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6330   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6331 }
6332 
6333 // This routine is similar to the above but does not record
6334 // any policy statistics or update free lists; we are abandoning
6335 // the current incremental collection set in preparation of a
6336 // full collection. After the full GC we will start to build up
6337 // the incremental collection set again.
6338 // This is only called when we're doing a full collection
6339 // and is immediately followed by the tearing down of the young list.
6340 
6341 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6342   HeapRegion* cur = cs_head;
6343 
6344   while (cur != NULL) {
6345     HeapRegion* next = cur->next_in_collection_set();
6346     assert(cur->in_collection_set(), "bad CS");
6347     cur->set_next_in_collection_set(NULL);
6348     cur->set_in_collection_set(false);
6349     cur->set_young_index_in_cset(-1);
6350     cur = next;
6351   }
6352 }
6353 
6354 void G1CollectedHeap::set_free_regions_coming() {
6355   if (G1ConcRegionFreeingVerbose) {
6356     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6357                            "setting free regions coming");
6358   }
6359 
6360   assert(!free_regions_coming(), "pre-condition");
6361   _free_regions_coming = true;
6362 }
6363 
6364 void G1CollectedHeap::reset_free_regions_coming() {
6365   assert(free_regions_coming(), "pre-condition");
6366 
6367   {
6368     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6369     _free_regions_coming = false;
6370     SecondaryFreeList_lock->notify_all();
6371   }
6372 
6373   if (G1ConcRegionFreeingVerbose) {
6374     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6375                            "reset free regions coming");
6376   }
6377 }
6378 
6379 void G1CollectedHeap::wait_while_free_regions_coming() {
6380   // Most of the time we won't have to wait, so let's do a quick test
6381   // first before we take the lock.
6382   if (!free_regions_coming()) {
6383     return;
6384   }
6385 
6386   if (G1ConcRegionFreeingVerbose) {
6387     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6388                            "waiting for free regions");
6389   }
6390 
6391   {
6392     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6393     while (free_regions_coming()) {
6394       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6395     }
6396   }
6397 
6398   if (G1ConcRegionFreeingVerbose) {
6399     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6400                            "done waiting for free regions");
6401   }
6402 }
6403 
6404 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6405   assert(heap_lock_held_for_gc(),
6406               "the heap lock should already be held by or for this thread");
6407   _young_list->push_region(hr);
6408 }
6409 
6410 class NoYoungRegionsClosure: public HeapRegionClosure {
6411 private:
6412   bool _success;
6413 public:
6414   NoYoungRegionsClosure() : _success(true) { }
6415   bool doHeapRegion(HeapRegion* r) {
6416     if (r->is_young()) {
6417       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6418                              r->bottom(), r->end());
6419       _success = false;
6420     }
6421     return false;
6422   }
6423   bool success() { return _success; }
6424 };
6425 
6426 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6427   bool ret = _young_list->check_list_empty(check_sample);
6428 
6429   if (check_heap) {
6430     NoYoungRegionsClosure closure;
6431     heap_region_iterate(&closure);
6432     ret = ret && closure.success();
6433   }
6434 
6435   return ret;
6436 }
6437 
6438 class TearDownRegionSetsClosure : public HeapRegionClosure {
6439 private:
6440   HeapRegionSet *_old_set;
6441 
6442 public:
6443   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6444 
6445   bool doHeapRegion(HeapRegion* r) {
6446     if (r->is_empty()) {
6447       // We ignore empty regions, we'll empty the free list afterwards
6448     } else if (r->is_young()) {
6449       // We ignore young regions, we'll empty the young list afterwards
6450     } else if (r->isHumongous()) {
6451       // We ignore humongous regions, we're not tearing down the
6452       // humongous region set
6453     } else {
6454       // The rest should be old
6455       _old_set->remove(r);
6456     }
6457     return false;
6458   }
6459 
6460   ~TearDownRegionSetsClosure() {
6461     assert(_old_set->is_empty(), "post-condition");
6462   }
6463 };
6464 
6465 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6466   assert_at_safepoint(true /* should_be_vm_thread */);
6467 
6468   if (!free_list_only) {
6469     TearDownRegionSetsClosure cl(&_old_set);
6470     heap_region_iterate(&cl);
6471 
6472     // Note that emptying the _young_list is postponed and instead done as
6473     // the first step when rebuilding the regions sets again. The reason for
6474     // this is that during a full GC string deduplication needs to know if
6475     // a collected region was young or old when the full GC was initiated.
6476   }
6477   _free_list.remove_all();
6478 }
6479 
6480 class RebuildRegionSetsClosure : public HeapRegionClosure {
6481 private:
6482   bool            _free_list_only;
6483   HeapRegionSet*   _old_set;
6484   FreeRegionList* _free_list;
6485   size_t          _total_used;
6486 
6487 public:
6488   RebuildRegionSetsClosure(bool free_list_only,
6489                            HeapRegionSet* old_set, FreeRegionList* free_list) :
6490     _free_list_only(free_list_only),
6491     _old_set(old_set), _free_list(free_list), _total_used(0) {
6492     assert(_free_list->is_empty(), "pre-condition");
6493     if (!free_list_only) {
6494       assert(_old_set->is_empty(), "pre-condition");
6495     }
6496   }
6497 
6498   bool doHeapRegion(HeapRegion* r) {
6499     if (r->continuesHumongous()) {
6500       return false;
6501     }
6502 
6503     if (r->is_empty()) {
6504       // Add free regions to the free list
6505       _free_list->add_as_tail(r);
6506     } else if (!_free_list_only) {
6507       assert(!r->is_young(), "we should not come across young regions");
6508 
6509       if (r->isHumongous()) {
6510         // We ignore humongous regions, we left the humongous set unchanged
6511       } else {
6512         // The rest should be old, add them to the old set
6513         _old_set->add(r);
6514       }
6515       _total_used += r->used();
6516     }
6517 
6518     return false;
6519   }
6520 
6521   size_t total_used() {
6522     return _total_used;
6523   }
6524 };
6525 
6526 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6527   assert_at_safepoint(true /* should_be_vm_thread */);
6528 
6529   if (!free_list_only) {
6530     _young_list->empty_list();
6531   }
6532 
6533   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6534   heap_region_iterate(&cl);
6535 
6536   if (!free_list_only) {
6537     _summary_bytes_used = cl.total_used();
6538   }
6539   assert(_summary_bytes_used == recalculate_used(),
6540          err_msg("inconsistent _summary_bytes_used, "
6541                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6542                  _summary_bytes_used, recalculate_used()));
6543 }
6544 
6545 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6546   _refine_cte_cl->set_concurrent(concurrent);
6547 }
6548 
6549 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6550   HeapRegion* hr = heap_region_containing(p);
6551   return hr->is_in(p);
6552 }
6553 
6554 // Methods for the mutator alloc region
6555 
6556 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6557                                                       bool force) {
6558   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6559   assert(!force || g1_policy()->can_expand_young_list(),
6560          "if force is true we should be able to expand the young list");
6561   bool young_list_full = g1_policy()->is_young_list_full();
6562   if (force || !young_list_full) {
6563     HeapRegion* new_alloc_region = new_region(word_size,
6564                                               false /* is_old */,
6565                                               false /* do_expand */);
6566     if (new_alloc_region != NULL) {
6567       set_region_short_lived_locked(new_alloc_region);
6568       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6569       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6570       return new_alloc_region;
6571     }
6572   }
6573   return NULL;
6574 }
6575 
6576 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6577                                                   size_t allocated_bytes) {
6578   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6579   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6580 
6581   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6582   _summary_bytes_used += allocated_bytes;
6583   _hr_printer.retire(alloc_region);
6584   // We update the eden sizes here, when the region is retired,
6585   // instead of when it's allocated, since this is the point that its
6586   // used space has been recored in _summary_bytes_used.
6587   g1mm()->update_eden_size();
6588 }
6589 
6590 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6591                                                     bool force) {
6592   return _g1h->new_mutator_alloc_region(word_size, force);
6593 }
6594 
6595 void G1CollectedHeap::set_par_threads() {
6596   // Don't change the number of workers.  Use the value previously set
6597   // in the workgroup.
6598   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6599   uint n_workers = workers()->active_workers();
6600   assert(UseDynamicNumberOfGCThreads ||
6601            n_workers == workers()->total_workers(),
6602       "Otherwise should be using the total number of workers");
6603   if (n_workers == 0) {
6604     assert(false, "Should have been set in prior evacuation pause.");
6605     n_workers = ParallelGCThreads;
6606     workers()->set_active_workers(n_workers);
6607   }
6608   set_par_threads(n_workers);
6609 }
6610 
6611 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6612                                        size_t allocated_bytes) {
6613   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6614 }
6615 
6616 // Methods for the GC alloc regions
6617 
6618 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6619                                                  uint count,
6620                                                  GCAllocPurpose ap) {
6621   assert(FreeList_lock->owned_by_self(), "pre-condition");
6622 
6623   if (count < g1_policy()->max_regions(ap)) {
6624     bool survivor = (ap == GCAllocForSurvived);
6625     HeapRegion* new_alloc_region = new_region(word_size,
6626                                               !survivor,
6627                                               true /* do_expand */);
6628     if (new_alloc_region != NULL) {
6629       // We really only need to do this for old regions given that we
6630       // should never scan survivors. But it doesn't hurt to do it
6631       // for survivors too.
6632       new_alloc_region->set_saved_mark();
6633       if (survivor) {
6634         new_alloc_region->set_survivor();
6635         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6636         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6637       } else {
6638         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6639         check_bitmaps("Old Region Allocation", new_alloc_region);
6640       }
6641       bool during_im = g1_policy()->during_initial_mark_pause();
6642       new_alloc_region->note_start_of_copying(during_im);
6643       return new_alloc_region;
6644     } else {
6645       g1_policy()->note_alloc_region_limit_reached(ap);
6646     }
6647   }
6648   return NULL;
6649 }
6650 
6651 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6652                                              size_t allocated_bytes,
6653                                              GCAllocPurpose ap) {
6654   bool during_im = g1_policy()->during_initial_mark_pause();
6655   alloc_region->note_end_of_copying(during_im);
6656   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6657   if (ap == GCAllocForSurvived) {
6658     young_list()->add_survivor_region(alloc_region);
6659   } else {
6660     _old_set.add(alloc_region);
6661   }
6662   _hr_printer.retire(alloc_region);
6663 }
6664 
6665 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6666                                                        bool force) {
6667   assert(!force, "not supported for GC alloc regions");
6668   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6669 }
6670 
6671 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6672                                           size_t allocated_bytes) {
6673   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6674                                GCAllocForSurvived);
6675 }
6676 
6677 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6678                                                   bool force) {
6679   assert(!force, "not supported for GC alloc regions");
6680   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6681 }
6682 
6683 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6684                                      size_t allocated_bytes) {
6685   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6686                                GCAllocForTenured);
6687 }
6688 // Heap region set verification
6689 
6690 class VerifyRegionListsClosure : public HeapRegionClosure {
6691 private:
6692   HeapRegionSet*   _old_set;
6693   HeapRegionSet*   _humongous_set;
6694   FreeRegionList*  _free_list;
6695 
6696 public:
6697   HeapRegionSetCount _old_count;
6698   HeapRegionSetCount _humongous_count;
6699   HeapRegionSetCount _free_count;
6700 
6701   VerifyRegionListsClosure(HeapRegionSet* old_set,
6702                            HeapRegionSet* humongous_set,
6703                            FreeRegionList* free_list) :
6704     _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list),
6705     _old_count(), _humongous_count(), _free_count(){ }
6706 
6707   bool doHeapRegion(HeapRegion* hr) {
6708     if (hr->continuesHumongous()) {
6709       return false;
6710     }
6711 
6712     if (hr->is_young()) {
6713       // TODO
6714     } else if (hr->startsHumongous()) {
6715       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrs_index()));
6716       _humongous_count.increment(1u, hr->capacity());
6717     } else if (hr->is_empty()) {
6718       assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->hrs_index()));
6719       _free_count.increment(1u, hr->capacity());
6720     } else {
6721       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrs_index()));
6722       _old_count.increment(1u, hr->capacity());
6723     }
6724     return false;
6725   }
6726 
6727   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) {
6728     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6729     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6730         old_set->total_capacity_bytes(), _old_count.capacity()));
6731 
6732     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6733     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6734         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6735 
6736     guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length()));
6737     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6738         free_list->total_capacity_bytes(), _free_count.capacity()));
6739   }
6740 };
6741 
6742 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6743                                              HeapWord* bottom) {
6744   HeapWord* end = bottom + HeapRegion::GrainWords;
6745   MemRegion mr(bottom, end);
6746   assert(_g1_reserved.contains(mr), "invariant");
6747   // This might return NULL if the allocation fails
6748   return new HeapRegion(hrs_index, _bot_shared, mr);
6749 }
6750 
6751 void G1CollectedHeap::verify_region_sets() {
6752   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6753 
6754   // First, check the explicit lists.
6755   _free_list.verify_list();
6756   {
6757     // Given that a concurrent operation might be adding regions to
6758     // the secondary free list we have to take the lock before
6759     // verifying it.
6760     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6761     _secondary_free_list.verify_list();
6762   }
6763 
6764   // If a concurrent region freeing operation is in progress it will
6765   // be difficult to correctly attributed any free regions we come
6766   // across to the correct free list given that they might belong to
6767   // one of several (free_list, secondary_free_list, any local lists,
6768   // etc.). So, if that's the case we will skip the rest of the
6769   // verification operation. Alternatively, waiting for the concurrent
6770   // operation to complete will have a non-trivial effect on the GC's
6771   // operation (no concurrent operation will last longer than the
6772   // interval between two calls to verification) and it might hide
6773   // any issues that we would like to catch during testing.
6774   if (free_regions_coming()) {
6775     return;
6776   }
6777 
6778   // Make sure we append the secondary_free_list on the free_list so
6779   // that all free regions we will come across can be safely
6780   // attributed to the free_list.
6781   append_secondary_free_list_if_not_empty_with_lock();
6782 
6783   // Finally, make sure that the region accounting in the lists is
6784   // consistent with what we see in the heap.
6785 
6786   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6787   heap_region_iterate(&cl);
6788   cl.verify_counts(&_old_set, &_humongous_set, &_free_list);
6789 }
6790 
6791 // Optimized nmethod scanning
6792 
6793 class RegisterNMethodOopClosure: public OopClosure {
6794   G1CollectedHeap* _g1h;
6795   nmethod* _nm;
6796 
6797   template <class T> void do_oop_work(T* p) {
6798     T heap_oop = oopDesc::load_heap_oop(p);
6799     if (!oopDesc::is_null(heap_oop)) {
6800       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6801       HeapRegion* hr = _g1h->heap_region_containing(obj);
6802       assert(!hr->continuesHumongous(),
6803              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6804                      " starting at "HR_FORMAT,
6805                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6806 
6807       // HeapRegion::add_strong_code_root() avoids adding duplicate
6808       // entries but having duplicates is  OK since we "mark" nmethods
6809       // as visited when we scan the strong code root lists during the GC.
6810       hr->add_strong_code_root(_nm);
6811       assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
6812              err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
6813                      _nm, HR_FORMAT_PARAMS(hr)));
6814     }
6815   }
6816 
6817 public:
6818   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6819     _g1h(g1h), _nm(nm) {}
6820 
6821   void do_oop(oop* p)       { do_oop_work(p); }
6822   void do_oop(narrowOop* p) { do_oop_work(p); }
6823 };
6824 
6825 class UnregisterNMethodOopClosure: public OopClosure {
6826   G1CollectedHeap* _g1h;
6827   nmethod* _nm;
6828 
6829   template <class T> void do_oop_work(T* p) {
6830     T heap_oop = oopDesc::load_heap_oop(p);
6831     if (!oopDesc::is_null(heap_oop)) {
6832       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6833       HeapRegion* hr = _g1h->heap_region_containing(obj);
6834       assert(!hr->continuesHumongous(),
6835              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6836                      " starting at "HR_FORMAT,
6837                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6838 
6839       hr->remove_strong_code_root(_nm);
6840       assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
6841              err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
6842                      _nm, HR_FORMAT_PARAMS(hr)));
6843     }
6844   }
6845 
6846 public:
6847   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6848     _g1h(g1h), _nm(nm) {}
6849 
6850   void do_oop(oop* p)       { do_oop_work(p); }
6851   void do_oop(narrowOop* p) { do_oop_work(p); }
6852 };
6853 
6854 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6855   CollectedHeap::register_nmethod(nm);
6856 
6857   guarantee(nm != NULL, "sanity");
6858   RegisterNMethodOopClosure reg_cl(this, nm);
6859   nm->oops_do(&reg_cl);
6860 }
6861 
6862 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6863   CollectedHeap::unregister_nmethod(nm);
6864 
6865   guarantee(nm != NULL, "sanity");
6866   UnregisterNMethodOopClosure reg_cl(this, nm);
6867   nm->oops_do(&reg_cl, true);
6868 }
6869 
6870 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6871 public:
6872   bool doHeapRegion(HeapRegion *hr) {
6873     assert(!hr->isHumongous(),
6874            err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
6875                    HR_FORMAT_PARAMS(hr)));
6876     hr->migrate_strong_code_roots();
6877     return false;
6878   }
6879 };
6880 
6881 void G1CollectedHeap::migrate_strong_code_roots() {
6882   MigrateCodeRootsHeapRegionClosure cl;
6883   double migrate_start = os::elapsedTime();
6884   collection_set_iterate(&cl);
6885   double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6886   g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6887 }
6888 
6889 void G1CollectedHeap::purge_code_root_memory() {
6890   double purge_start = os::elapsedTime();
6891   G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
6892   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6893   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6894 }
6895 
6896 // Mark all the code roots that point into regions *not* in the
6897 // collection set.
6898 //
6899 // Note we do not want to use a "marking" CodeBlobToOopClosure while
6900 // walking the the code roots lists of regions not in the collection
6901 // set. Suppose we have an nmethod (M) that points to objects in two
6902 // separate regions - one in the collection set (R1) and one not (R2).
6903 // Using a "marking" CodeBlobToOopClosure here would result in "marking"
6904 // nmethod M when walking the code roots for R1. When we come to scan
6905 // the code roots for R2, we would see that M is already marked and it
6906 // would be skipped and the objects in R2 that are referenced from M
6907 // would not be evacuated.
6908 
6909 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
6910 
6911   class MarkStrongCodeRootOopClosure: public OopClosure {
6912     ConcurrentMark* _cm;
6913     HeapRegion* _hr;
6914     uint _worker_id;
6915 
6916     template <class T> void do_oop_work(T* p) {
6917       T heap_oop = oopDesc::load_heap_oop(p);
6918       if (!oopDesc::is_null(heap_oop)) {
6919         oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6920         // Only mark objects in the region (which is assumed
6921         // to be not in the collection set).
6922         if (_hr->is_in(obj)) {
6923           _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
6924         }
6925       }
6926     }
6927 
6928   public:
6929     MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
6930       _cm(cm), _hr(hr), _worker_id(worker_id) {
6931       assert(!_hr->in_collection_set(), "sanity");
6932     }
6933 
6934     void do_oop(narrowOop* p) { do_oop_work(p); }
6935     void do_oop(oop* p)       { do_oop_work(p); }
6936   };
6937 
6938   MarkStrongCodeRootOopClosure _oop_cl;
6939 
6940 public:
6941   MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
6942     _oop_cl(cm, hr, worker_id) {}
6943 
6944   void do_code_blob(CodeBlob* cb) {
6945     nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
6946     if (nm != NULL) {
6947       nm->oops_do(&_oop_cl);
6948     }
6949   }
6950 };
6951 
6952 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
6953   G1CollectedHeap* _g1h;
6954   uint _worker_id;
6955 
6956 public:
6957   MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
6958     _g1h(g1h), _worker_id(worker_id) {}
6959 
6960   bool doHeapRegion(HeapRegion *hr) {
6961     HeapRegionRemSet* hrrs = hr->rem_set();
6962     if (hr->continuesHumongous()) {
6963       // Code roots should never be attached to a continuation of a humongous region
6964       assert(hrrs->strong_code_roots_list_length() == 0,
6965              err_msg("code roots should never be attached to continuations of humongous region "HR_FORMAT
6966                      " starting at "HR_FORMAT", but has "SIZE_FORMAT,
6967                      HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()),
6968                      hrrs->strong_code_roots_list_length()));
6969       return false;
6970     }
6971 
6972     if (hr->in_collection_set()) {
6973       // Don't mark code roots into regions in the collection set here.
6974       // They will be marked when we scan them.
6975       return false;
6976     }
6977 
6978     MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
6979     hr->strong_code_roots_do(&cb_cl);
6980     return false;
6981   }
6982 };
6983 
6984 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
6985   MarkStrongCodeRootsHRClosure cl(this, worker_id);
6986   if (G1CollectedHeap::use_parallel_gc_threads()) {
6987     heap_region_par_iterate_chunked(&cl,
6988                                     worker_id,
6989                                     workers()->active_workers(),
6990                                     HeapRegion::ParMarkRootClaimValue);
6991   } else {
6992     heap_region_iterate(&cl);
6993   }
6994 }
6995 
6996 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6997   G1CollectedHeap* _g1h;
6998 
6999 public:
7000   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7001     _g1h(g1h) {}
7002 
7003   void do_code_blob(CodeBlob* cb) {
7004     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7005     if (nm == NULL) {
7006       return;
7007     }
7008 
7009     if (ScavengeRootsInCode && nm->detect_scavenge_root_oops()) {
7010       _g1h->register_nmethod(nm);
7011     }
7012   }
7013 };
7014 
7015 void G1CollectedHeap::rebuild_strong_code_roots() {
7016   RebuildStrongCodeRootClosure blob_cl(this);
7017   CodeCache::blobs_do(&blob_cl);
7018 }