1 /*
   2  * Copyright (c) 2001, 2015, 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 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/concurrentG1Refine.hpp"
  33 #include "gc/g1/concurrentG1RefineThread.hpp"
  34 #include "gc/g1/concurrentMarkThread.inline.hpp"
  35 #include "gc/g1/g1Allocator.inline.hpp"
  36 #include "gc/g1/g1CollectedHeap.inline.hpp"
  37 #include "gc/g1/g1CollectorPolicy.hpp"
  38 #include "gc/g1/g1CollectorState.hpp"
  39 #include "gc/g1/g1EvacStats.inline.hpp"
  40 #include "gc/g1/g1GCPhaseTimes.hpp"
  41 #include "gc/g1/g1HeapVerifier.hpp"
  42 #include "gc/g1/g1MarkSweep.hpp"
  43 #include "gc/g1/g1OopClosures.inline.hpp"
  44 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  45 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  46 #include "gc/g1/g1RemSet.inline.hpp"
  47 #include "gc/g1/g1RootClosures.hpp"
  48 #include "gc/g1/g1RootProcessor.hpp"
  49 #include "gc/g1/g1StringDedup.hpp"
  50 #include "gc/g1/g1YCTypes.hpp"
  51 #include "gc/g1/heapRegion.inline.hpp"
  52 #include "gc/g1/heapRegionRemSet.hpp"
  53 #include "gc/g1/heapRegionSet.inline.hpp"
  54 #include "gc/g1/suspendibleThreadSet.hpp"
  55 #include "gc/g1/vm_operations_g1.hpp"
  56 #include "gc/shared/gcHeapSummary.hpp"
  57 #include "gc/shared/gcId.hpp"
  58 #include "gc/shared/gcLocker.inline.hpp"
  59 #include "gc/shared/gcTimer.hpp"
  60 #include "gc/shared/gcTrace.hpp"
  61 #include "gc/shared/gcTraceTime.inline.hpp"
  62 #include "gc/shared/generationSpec.hpp"
  63 #include "gc/shared/isGCActiveMark.hpp"
  64 #include "gc/shared/referenceProcessor.hpp"
  65 #include "gc/shared/taskqueue.inline.hpp"
  66 #include "logging/log.hpp"
  67 #include "memory/allocation.hpp"
  68 #include "memory/iterator.hpp"
  69 #include "oops/oop.inline.hpp"
  70 #include "runtime/atomic.inline.hpp"
  71 #include "runtime/init.hpp"
  72 #include "runtime/orderAccess.inline.hpp"
  73 #include "runtime/vmThread.hpp"
  74 #include "utilities/globalDefinitions.hpp"
  75 #include "utilities/stack.inline.hpp"
  76 
  77 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  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 // Local to this file.
  89 
  90 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  91   bool _concurrent;
  92 public:
  93   RefineCardTableEntryClosure() : _concurrent(true) { }
  94 
  95   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
  96     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
  97     // This path is executed by the concurrent refine or mutator threads,
  98     // concurrently, and so we do not care if card_ptr contains references
  99     // that point into the collection set.
 100     assert(!oops_into_cset, "should be");
 101 
 102     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 103       // Caller will actually yield.
 104       return false;
 105     }
 106     // Otherwise, we finished successfully; return true.
 107     return true;
 108   }
 109 
 110   void set_concurrent(bool b) { _concurrent = b; }
 111 };
 112 
 113 
 114 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 115  private:
 116   size_t _num_dirtied;
 117   G1CollectedHeap* _g1h;
 118   G1SATBCardTableLoggingModRefBS* _g1_bs;
 119 
 120   HeapRegion* region_for_card(jbyte* card_ptr) const {
 121     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 122   }
 123 
 124   bool will_become_free(HeapRegion* hr) const {
 125     // A region will be freed by free_collection_set if the region is in the
 126     // collection set and has not had an evacuation failure.
 127     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 128   }
 129 
 130  public:
 131   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 132     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 133 
 134   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 135     HeapRegion* hr = region_for_card(card_ptr);
 136 
 137     // Should only dirty cards in regions that won't be freed.
 138     if (!will_become_free(hr)) {
 139       *card_ptr = CardTableModRefBS::dirty_card_val();
 140       _num_dirtied++;
 141     }
 142 
 143     return true;
 144   }
 145 
 146   size_t num_dirtied()   const { return _num_dirtied; }
 147 };
 148 
 149 
 150 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 151   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 152 }
 153 
 154 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 155   // The from card cache is not the memory that is actually committed. So we cannot
 156   // take advantage of the zero_filled parameter.
 157   reset_from_card_cache(start_idx, num_regions);
 158 }
 159 
 160 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 161 {
 162   // Claim the right to put the region on the dirty cards region list
 163   // by installing a self pointer.
 164   HeapRegion* next = hr->get_next_dirty_cards_region();
 165   if (next == NULL) {
 166     HeapRegion* res = (HeapRegion*)
 167       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 168                           NULL);
 169     if (res == NULL) {
 170       HeapRegion* head;
 171       do {
 172         // Put the region to the dirty cards region list.
 173         head = _dirty_cards_region_list;
 174         next = (HeapRegion*)
 175           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 176         if (next == head) {
 177           assert(hr->get_next_dirty_cards_region() == hr,
 178                  "hr->get_next_dirty_cards_region() != hr");
 179           if (next == NULL) {
 180             // The last region in the list points to itself.
 181             hr->set_next_dirty_cards_region(hr);
 182           } else {
 183             hr->set_next_dirty_cards_region(next);
 184           }
 185         }
 186       } while (next != head);
 187     }
 188   }
 189 }
 190 
 191 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 192 {
 193   HeapRegion* head;
 194   HeapRegion* hr;
 195   do {
 196     head = _dirty_cards_region_list;
 197     if (head == NULL) {
 198       return NULL;
 199     }
 200     HeapRegion* new_head = head->get_next_dirty_cards_region();
 201     if (head == new_head) {
 202       // The last region.
 203       new_head = NULL;
 204     }
 205     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 206                                           head);
 207   } while (hr != head);
 208   assert(hr != NULL, "invariant");
 209   hr->set_next_dirty_cards_region(NULL);
 210   return hr;
 211 }
 212 
 213 // Returns true if the reference points to an object that
 214 // can move in an incremental collection.
 215 bool G1CollectedHeap::is_scavengable(const void* p) {
 216   HeapRegion* hr = heap_region_containing(p);
 217   return !hr->is_pinned();
 218 }
 219 
 220 // Private methods.
 221 
 222 HeapRegion*
 223 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 224   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 225   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 226     if (!_secondary_free_list.is_empty()) {
 227       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 228                                       "secondary_free_list has %u entries",
 229                                       _secondary_free_list.length());
 230       // It looks as if there are free regions available on the
 231       // secondary_free_list. Let's move them to the free_list and try
 232       // again to allocate from it.
 233       append_secondary_free_list();
 234 
 235       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 236              "empty we should have moved at least one entry to the free_list");
 237       HeapRegion* res = _hrm.allocate_free_region(is_old);
 238       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 239                                       "allocated " HR_FORMAT " from secondary_free_list",
 240                                       HR_FORMAT_PARAMS(res));
 241       return res;
 242     }
 243 
 244     // Wait here until we get notified either when (a) there are no
 245     // more free regions coming or (b) some regions have been moved on
 246     // the secondary_free_list.
 247     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 248   }
 249 
 250   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 251                                   "could not allocate from secondary_free_list");
 252   return NULL;
 253 }
 254 
 255 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 256   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 257          "the only time we use this to allocate a humongous region is "
 258          "when we are allocating a single humongous region");
 259 
 260   HeapRegion* res;
 261   if (G1StressConcRegionFreeing) {
 262     if (!_secondary_free_list.is_empty()) {
 263       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 264                                       "forced to look at the secondary_free_list");
 265       res = new_region_try_secondary_free_list(is_old);
 266       if (res != NULL) {
 267         return res;
 268       }
 269     }
 270   }
 271 
 272   res = _hrm.allocate_free_region(is_old);
 273 
 274   if (res == NULL) {
 275     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 276                                     "res == NULL, trying the secondary_free_list");
 277     res = new_region_try_secondary_free_list(is_old);
 278   }
 279   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 280     // Currently, only attempts to allocate GC alloc regions set
 281     // do_expand to true. So, we should only reach here during a
 282     // safepoint. If this assumption changes we might have to
 283     // reconsider the use of _expand_heap_after_alloc_failure.
 284     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 285 
 286     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 287                               word_size * HeapWordSize);
 288 
 289     if (expand(word_size * HeapWordSize)) {
 290       // Given that expand() succeeded in expanding the heap, and we
 291       // always expand the heap by an amount aligned to the heap
 292       // region size, the free list should in theory not be empty.
 293       // In either case allocate_free_region() will check for NULL.
 294       res = _hrm.allocate_free_region(is_old);
 295     } else {
 296       _expand_heap_after_alloc_failure = false;
 297     }
 298   }
 299   return res;
 300 }
 301 
 302 HeapWord*
 303 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 304                                                            uint num_regions,
 305                                                            size_t word_size,
 306                                                            AllocationContext_t context) {
 307   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 308   assert(is_humongous(word_size), "word_size should be humongous");
 309   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 310 
 311   // Index of last region in the series.
 312   uint last = first + num_regions - 1;
 313 
 314   // We need to initialize the region(s) we just discovered. This is
 315   // a bit tricky given that it can happen concurrently with
 316   // refinement threads refining cards on these regions and
 317   // potentially wanting to refine the BOT as they are scanning
 318   // those cards (this can happen shortly after a cleanup; see CR
 319   // 6991377). So we have to set up the region(s) carefully and in
 320   // a specific order.
 321 
 322   // The word size sum of all the regions we will allocate.
 323   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 324   assert(word_size <= word_size_sum, "sanity");
 325 
 326   // This will be the "starts humongous" region.
 327   HeapRegion* first_hr = region_at(first);
 328   // The header of the new object will be placed at the bottom of
 329   // the first region.
 330   HeapWord* new_obj = first_hr->bottom();
 331   // This will be the new top of the new object.
 332   HeapWord* obj_top = new_obj + word_size;
 333 
 334   // First, we need to zero the header of the space that we will be
 335   // allocating. When we update top further down, some refinement
 336   // threads might try to scan the region. By zeroing the header we
 337   // ensure that any thread that will try to scan the region will
 338   // come across the zero klass word and bail out.
 339   //
 340   // NOTE: It would not have been correct to have used
 341   // CollectedHeap::fill_with_object() and make the space look like
 342   // an int array. The thread that is doing the allocation will
 343   // later update the object header to a potentially different array
 344   // type and, for a very short period of time, the klass and length
 345   // fields will be inconsistent. This could cause a refinement
 346   // thread to calculate the object size incorrectly.
 347   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 348 
 349   // How many words we use for filler objects.
 350   size_t word_fill_size = word_size_sum - word_size;
 351 
 352   // How many words memory we "waste" which cannot hold a filler object.
 353   size_t words_not_fillable = 0;
 354 
 355   if (word_fill_size >= min_fill_size()) {
 356     fill_with_objects(obj_top, word_fill_size);
 357   } else if (word_fill_size > 0) {
 358     // We have space to fill, but we cannot fit an object there.
 359     words_not_fillable = word_fill_size;
 360     word_fill_size = 0;
 361   }
 362 
 363   // We will set up the first region as "starts humongous". This
 364   // will also update the BOT covering all the regions to reflect
 365   // that there is a single object that starts at the bottom of the
 366   // first region.
 367   first_hr->set_starts_humongous(obj_top, word_fill_size);
 368   first_hr->set_allocation_context(context);
 369   // Then, if there are any, we will set up the "continues
 370   // humongous" regions.
 371   HeapRegion* hr = NULL;
 372   for (uint i = first + 1; i <= last; ++i) {
 373     hr = region_at(i);
 374     hr->set_continues_humongous(first_hr);
 375     hr->set_allocation_context(context);
 376   }
 377 
 378   // Up to this point no concurrent thread would have been able to
 379   // do any scanning on any region in this series. All the top
 380   // fields still point to bottom, so the intersection between
 381   // [bottom,top] and [card_start,card_end] will be empty. Before we
 382   // update the top fields, we'll do a storestore to make sure that
 383   // no thread sees the update to top before the zeroing of the
 384   // object header and the BOT initialization.
 385   OrderAccess::storestore();
 386 
 387   // Now, we will update the top fields of the "continues humongous"
 388   // regions except the last one.
 389   for (uint i = first; i < last; ++i) {
 390     hr = region_at(i);
 391     hr->set_top(hr->end());
 392   }
 393 
 394   hr = region_at(last);
 395   // If we cannot fit a filler object, we must set top to the end
 396   // of the humongous object, otherwise we cannot iterate the heap
 397   // and the BOT will not be complete.
 398   hr->set_top(hr->end() - words_not_fillable);
 399 
 400   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 401          "obj_top should be in last region");
 402 
 403   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 404 
 405   assert(words_not_fillable == 0 ||
 406          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 407          "Miscalculation in humongous allocation");
 408 
 409   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 410 
 411   for (uint i = first; i <= last; ++i) {
 412     hr = region_at(i);
 413     _humongous_set.add(hr);
 414     _hr_printer.alloc(hr);
 415   }
 416 
 417   return new_obj;
 418 }
 419 
 420 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 421   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 422   return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 423 }
 424 
 425 // If could fit into free regions w/o expansion, try.
 426 // Otherwise, if can expand, do so.
 427 // Otherwise, if using ex regions might help, try with ex given back.
 428 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 429   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 430 
 431   _verifier->verify_region_sets_optional();
 432 
 433   uint first = G1_NO_HRM_INDEX;
 434   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 435 
 436   if (obj_regions == 1) {
 437     // Only one region to allocate, try to use a fast path by directly allocating
 438     // from the free lists. Do not try to expand here, we will potentially do that
 439     // later.
 440     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 441     if (hr != NULL) {
 442       first = hr->hrm_index();
 443     }
 444   } else {
 445     // We can't allocate humongous regions spanning more than one region while
 446     // cleanupComplete() is running, since some of the regions we find to be
 447     // empty might not yet be added to the free list. It is not straightforward
 448     // to know in which list they are on so that we can remove them. We only
 449     // need to do this if we need to allocate more than one region to satisfy the
 450     // current humongous allocation request. If we are only allocating one region
 451     // we use the one-region region allocation code (see above), that already
 452     // potentially waits for regions from the secondary free list.
 453     wait_while_free_regions_coming();
 454     append_secondary_free_list_if_not_empty_with_lock();
 455 
 456     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 457     // are lucky enough to find some.
 458     first = _hrm.find_contiguous_only_empty(obj_regions);
 459     if (first != G1_NO_HRM_INDEX) {
 460       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 461     }
 462   }
 463 
 464   if (first == G1_NO_HRM_INDEX) {
 465     // Policy: We could not find enough regions for the humongous object in the
 466     // free list. Look through the heap to find a mix of free and uncommitted regions.
 467     // If so, try expansion.
 468     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 469     if (first != G1_NO_HRM_INDEX) {
 470       // We found something. Make sure these regions are committed, i.e. expand
 471       // the heap. Alternatively we could do a defragmentation GC.
 472       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 473                                     word_size * HeapWordSize);
 474 
 475 
 476       _hrm.expand_at(first, obj_regions);
 477       g1_policy()->record_new_heap_size(num_regions());
 478 
 479 #ifdef ASSERT
 480       for (uint i = first; i < first + obj_regions; ++i) {
 481         HeapRegion* hr = region_at(i);
 482         assert(hr->is_free(), "sanity");
 483         assert(hr->is_empty(), "sanity");
 484         assert(is_on_master_free_list(hr), "sanity");
 485       }
 486 #endif
 487       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 488     } else {
 489       // Policy: Potentially trigger a defragmentation GC.
 490     }
 491   }
 492 
 493   HeapWord* result = NULL;
 494   if (first != G1_NO_HRM_INDEX) {
 495     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 496                                                        word_size, context);
 497     assert(result != NULL, "it should always return a valid result");
 498 
 499     // A successful humongous object allocation changes the used space
 500     // information of the old generation so we need to recalculate the
 501     // sizes and update the jstat counters here.
 502     g1mm()->update_sizes();
 503   }
 504 
 505   _verifier->verify_region_sets_optional();
 506 
 507   return result;
 508 }
 509 
 510 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 511   assert_heap_not_locked_and_not_at_safepoint();
 512   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 513 
 514   uint dummy_gc_count_before;
 515   uint dummy_gclocker_retry_count = 0;
 516   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 517 }
 518 
 519 HeapWord*
 520 G1CollectedHeap::mem_allocate(size_t word_size,
 521                               bool*  gc_overhead_limit_was_exceeded) {
 522   assert_heap_not_locked_and_not_at_safepoint();
 523 
 524   // Loop until the allocation is satisfied, or unsatisfied after GC.
 525   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 526     uint gc_count_before;
 527 
 528     HeapWord* result = NULL;
 529     if (!is_humongous(word_size)) {
 530       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 531     } else {
 532       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 533     }
 534     if (result != NULL) {
 535       return result;
 536     }
 537 
 538     // Create the garbage collection operation...
 539     VM_G1CollectForAllocation op(gc_count_before, word_size);
 540     op.set_allocation_context(AllocationContext::current());
 541 
 542     // ...and get the VM thread to execute it.
 543     VMThread::execute(&op);
 544 
 545     if (op.prologue_succeeded() && op.pause_succeeded()) {
 546       // If the operation was successful we'll return the result even
 547       // if it is NULL. If the allocation attempt failed immediately
 548       // after a Full GC, it's unlikely we'll be able to allocate now.
 549       HeapWord* result = op.result();
 550       if (result != NULL && !is_humongous(word_size)) {
 551         // Allocations that take place on VM operations do not do any
 552         // card dirtying and we have to do it here. We only have to do
 553         // this for non-humongous allocations, though.
 554         dirty_young_block(result, word_size);
 555       }
 556       return result;
 557     } else {
 558       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 559         return NULL;
 560       }
 561       assert(op.result() == NULL,
 562              "the result should be NULL if the VM op did not succeed");
 563     }
 564 
 565     // Give a warning if we seem to be looping forever.
 566     if ((QueuedAllocationWarningCount > 0) &&
 567         (try_count % QueuedAllocationWarningCount == 0)) {
 568       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 569     }
 570   }
 571 
 572   ShouldNotReachHere();
 573   return NULL;
 574 }
 575 
 576 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 577                                                    AllocationContext_t context,
 578                                                    uint* gc_count_before_ret,
 579                                                    uint* gclocker_retry_count_ret) {
 580   // Make sure you read the note in attempt_allocation_humongous().
 581 
 582   assert_heap_not_locked_and_not_at_safepoint();
 583   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 584          "be called for humongous allocation requests");
 585 
 586   // We should only get here after the first-level allocation attempt
 587   // (attempt_allocation()) failed to allocate.
 588 
 589   // We will loop until a) we manage to successfully perform the
 590   // allocation or b) we successfully schedule a collection which
 591   // fails to perform the allocation. b) is the only case when we'll
 592   // return NULL.
 593   HeapWord* result = NULL;
 594   for (int try_count = 1; /* we'll return */; try_count += 1) {
 595     bool should_try_gc;
 596     uint gc_count_before;
 597 
 598     {
 599       MutexLockerEx x(Heap_lock);
 600       result = _allocator->attempt_allocation_locked(word_size, context);
 601       if (result != NULL) {
 602         return result;
 603       }
 604 
 605       if (GCLocker::is_active_and_needs_gc()) {
 606         if (g1_policy()->can_expand_young_list()) {
 607           // No need for an ergo verbose message here,
 608           // can_expand_young_list() does this when it returns true.
 609           result = _allocator->attempt_allocation_force(word_size, context);
 610           if (result != NULL) {
 611             return result;
 612           }
 613         }
 614         should_try_gc = false;
 615       } else {
 616         // The GCLocker may not be active but the GCLocker initiated
 617         // GC may not yet have been performed (GCLocker::needs_gc()
 618         // returns true). In this case we do not try this GC and
 619         // wait until the GCLocker initiated GC is performed, and
 620         // then retry the allocation.
 621         if (GCLocker::needs_gc()) {
 622           should_try_gc = false;
 623         } else {
 624           // Read the GC count while still holding the Heap_lock.
 625           gc_count_before = total_collections();
 626           should_try_gc = true;
 627         }
 628       }
 629     }
 630 
 631     if (should_try_gc) {
 632       bool succeeded;
 633       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 634                                    GCCause::_g1_inc_collection_pause);
 635       if (result != NULL) {
 636         assert(succeeded, "only way to get back a non-NULL result");
 637         return result;
 638       }
 639 
 640       if (succeeded) {
 641         // If we get here we successfully scheduled a collection which
 642         // failed to allocate. No point in trying to allocate
 643         // further. We'll just return NULL.
 644         MutexLockerEx x(Heap_lock);
 645         *gc_count_before_ret = total_collections();
 646         return NULL;
 647       }
 648     } else {
 649       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 650         MutexLockerEx x(Heap_lock);
 651         *gc_count_before_ret = total_collections();
 652         return NULL;
 653       }
 654       // The GCLocker is either active or the GCLocker initiated
 655       // GC has not yet been performed. Stall until it is and
 656       // then retry the allocation.
 657       GCLocker::stall_until_clear();
 658       (*gclocker_retry_count_ret) += 1;
 659     }
 660 
 661     // We can reach here if we were unsuccessful in scheduling a
 662     // collection (because another thread beat us to it) or if we were
 663     // stalled due to the GC locker. In either can we should retry the
 664     // allocation attempt in case another thread successfully
 665     // performed a collection and reclaimed enough space. We do the
 666     // first attempt (without holding the Heap_lock) here and the
 667     // follow-on attempt will be at the start of the next loop
 668     // iteration (after taking the Heap_lock).
 669     result = _allocator->attempt_allocation(word_size, context);
 670     if (result != NULL) {
 671       return result;
 672     }
 673 
 674     // Give a warning if we seem to be looping forever.
 675     if ((QueuedAllocationWarningCount > 0) &&
 676         (try_count % QueuedAllocationWarningCount == 0)) {
 677       warning("G1CollectedHeap::attempt_allocation_slow() "
 678               "retries %d times", try_count);
 679     }
 680   }
 681 
 682   ShouldNotReachHere();
 683   return NULL;
 684 }
 685 
 686 void G1CollectedHeap::begin_archive_alloc_range() {
 687   assert_at_safepoint(true /* should_be_vm_thread */);
 688   if (_archive_allocator == NULL) {
 689     _archive_allocator = G1ArchiveAllocator::create_allocator(this);
 690   }
 691 }
 692 
 693 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 694   // Allocations in archive regions cannot be of a size that would be considered
 695   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 696   // may be different at archive-restore time.
 697   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 698 }
 699 
 700 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 701   assert_at_safepoint(true /* should_be_vm_thread */);
 702   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 703   if (is_archive_alloc_too_large(word_size)) {
 704     return NULL;
 705   }
 706   return _archive_allocator->archive_mem_allocate(word_size);
 707 }
 708 
 709 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 710                                               size_t end_alignment_in_bytes) {
 711   assert_at_safepoint(true /* should_be_vm_thread */);
 712   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 713 
 714   // Call complete_archive to do the real work, filling in the MemRegion
 715   // array with the archive regions.
 716   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 717   delete _archive_allocator;
 718   _archive_allocator = NULL;
 719 }
 720 
 721 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 722   assert(ranges != NULL, "MemRegion array NULL");
 723   assert(count != 0, "No MemRegions provided");
 724   MemRegion reserved = _hrm.reserved();
 725   for (size_t i = 0; i < count; i++) {
 726     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 727       return false;
 728     }
 729   }
 730   return true;
 731 }
 732 
 733 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
 734   assert(!is_init_completed(), "Expect to be called at JVM init time");
 735   assert(ranges != NULL, "MemRegion array NULL");
 736   assert(count != 0, "No MemRegions provided");
 737   MutexLockerEx x(Heap_lock);
 738 
 739   MemRegion reserved = _hrm.reserved();
 740   HeapWord* prev_last_addr = NULL;
 741   HeapRegion* prev_last_region = NULL;
 742 
 743   // Temporarily disable pretouching of heap pages. This interface is used
 744   // when mmap'ing archived heap data in, so pre-touching is wasted.
 745   FlagSetting fs(AlwaysPreTouch, false);
 746 
 747   // Enable archive object checking in G1MarkSweep. We have to let it know
 748   // about each archive range, so that objects in those ranges aren't marked.
 749   G1MarkSweep::enable_archive_object_check();
 750 
 751   // For each specified MemRegion range, allocate the corresponding G1
 752   // regions and mark them as archive regions. We expect the ranges in
 753   // ascending starting address order, without overlap.
 754   for (size_t i = 0; i < count; i++) {
 755     MemRegion curr_range = ranges[i];
 756     HeapWord* start_address = curr_range.start();
 757     size_t word_size = curr_range.word_size();
 758     HeapWord* last_address = curr_range.last();
 759     size_t commits = 0;
 760 
 761     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 762               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 763               p2i(start_address), p2i(last_address));
 764     guarantee(start_address > prev_last_addr,
 765               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 766               p2i(start_address), p2i(prev_last_addr));
 767     prev_last_addr = last_address;
 768 
 769     // Check for ranges that start in the same G1 region in which the previous
 770     // range ended, and adjust the start address so we don't try to allocate
 771     // the same region again. If the current range is entirely within that
 772     // region, skip it, just adjusting the recorded top.
 773     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 774     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 775       start_address = start_region->end();
 776       if (start_address > last_address) {
 777         increase_used(word_size * HeapWordSize);
 778         start_region->set_top(last_address + 1);
 779         continue;
 780       }
 781       start_region->set_top(start_address);
 782       curr_range = MemRegion(start_address, last_address + 1);
 783       start_region = _hrm.addr_to_region(start_address);
 784     }
 785 
 786     // Perform the actual region allocation, exiting if it fails.
 787     // Then note how much new space we have allocated.
 788     if (!_hrm.allocate_containing_regions(curr_range, &commits)) {
 789       return false;
 790     }
 791     increase_used(word_size * HeapWordSize);
 792     if (commits != 0) {
 793       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 794                                 HeapRegion::GrainWords * HeapWordSize * commits);
 795 
 796     }
 797 
 798     // Mark each G1 region touched by the range as archive, add it to the old set,
 799     // and set the allocation context and top.
 800     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 801     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 802     prev_last_region = last_region;
 803 
 804     while (curr_region != NULL) {
 805       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 806              "Region already in use (index %u)", curr_region->hrm_index());
 807       curr_region->set_allocation_context(AllocationContext::system());
 808       curr_region->set_archive();
 809       _hr_printer.alloc(curr_region);
 810       _old_set.add(curr_region);
 811       if (curr_region != last_region) {
 812         curr_region->set_top(curr_region->end());
 813         curr_region = _hrm.next_region_in_heap(curr_region);
 814       } else {
 815         curr_region->set_top(last_address + 1);
 816         curr_region = NULL;
 817       }
 818     }
 819 
 820     // Notify mark-sweep of the archive range.
 821     G1MarkSweep::set_range_archive(curr_range, true);
 822   }
 823   return true;
 824 }
 825 
 826 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 827   assert(!is_init_completed(), "Expect to be called at JVM init time");
 828   assert(ranges != NULL, "MemRegion array NULL");
 829   assert(count != 0, "No MemRegions provided");
 830   MemRegion reserved = _hrm.reserved();
 831   HeapWord *prev_last_addr = NULL;
 832   HeapRegion* prev_last_region = NULL;
 833 
 834   // For each MemRegion, create filler objects, if needed, in the G1 regions
 835   // that contain the address range. The address range actually within the
 836   // MemRegion will not be modified. That is assumed to have been initialized
 837   // elsewhere, probably via an mmap of archived heap data.
 838   MutexLockerEx x(Heap_lock);
 839   for (size_t i = 0; i < count; i++) {
 840     HeapWord* start_address = ranges[i].start();
 841     HeapWord* last_address = ranges[i].last();
 842 
 843     assert(reserved.contains(start_address) && reserved.contains(last_address),
 844            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 845            p2i(start_address), p2i(last_address));
 846     assert(start_address > prev_last_addr,
 847            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 848            p2i(start_address), p2i(prev_last_addr));
 849 
 850     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 851     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 852     HeapWord* bottom_address = start_region->bottom();
 853 
 854     // Check for a range beginning in the same region in which the
 855     // previous one ended.
 856     if (start_region == prev_last_region) {
 857       bottom_address = prev_last_addr + 1;
 858     }
 859 
 860     // Verify that the regions were all marked as archive regions by
 861     // alloc_archive_regions.
 862     HeapRegion* curr_region = start_region;
 863     while (curr_region != NULL) {
 864       guarantee(curr_region->is_archive(),
 865                 "Expected archive region at index %u", curr_region->hrm_index());
 866       if (curr_region != last_region) {
 867         curr_region = _hrm.next_region_in_heap(curr_region);
 868       } else {
 869         curr_region = NULL;
 870       }
 871     }
 872 
 873     prev_last_addr = last_address;
 874     prev_last_region = last_region;
 875 
 876     // Fill the memory below the allocated range with dummy object(s),
 877     // if the region bottom does not match the range start, or if the previous
 878     // range ended within the same G1 region, and there is a gap.
 879     if (start_address != bottom_address) {
 880       size_t fill_size = pointer_delta(start_address, bottom_address);
 881       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 882       increase_used(fill_size * HeapWordSize);
 883     }
 884   }
 885 }
 886 
 887 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 888                                                      uint* gc_count_before_ret,
 889                                                      uint* gclocker_retry_count_ret) {
 890   assert_heap_not_locked_and_not_at_safepoint();
 891   assert(!is_humongous(word_size), "attempt_allocation() should not "
 892          "be called for humongous allocation requests");
 893 
 894   AllocationContext_t context = AllocationContext::current();
 895   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 896 
 897   if (result == NULL) {
 898     result = attempt_allocation_slow(word_size,
 899                                      context,
 900                                      gc_count_before_ret,
 901                                      gclocker_retry_count_ret);
 902   }
 903   assert_heap_not_locked();
 904   if (result != NULL) {
 905     dirty_young_block(result, word_size);
 906   }
 907   return result;
 908 }
 909 
 910 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 911   assert(!is_init_completed(), "Expect to be called at JVM init time");
 912   assert(ranges != NULL, "MemRegion array NULL");
 913   assert(count != 0, "No MemRegions provided");
 914   MemRegion reserved = _hrm.reserved();
 915   HeapWord* prev_last_addr = NULL;
 916   HeapRegion* prev_last_region = NULL;
 917   size_t size_used = 0;
 918   size_t uncommitted_regions = 0;
 919 
 920   // For each Memregion, free the G1 regions that constitute it, and
 921   // notify mark-sweep that the range is no longer to be considered 'archive.'
 922   MutexLockerEx x(Heap_lock);
 923   for (size_t i = 0; i < count; i++) {
 924     HeapWord* start_address = ranges[i].start();
 925     HeapWord* last_address = ranges[i].last();
 926 
 927     assert(reserved.contains(start_address) && reserved.contains(last_address),
 928            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 929            p2i(start_address), p2i(last_address));
 930     assert(start_address > prev_last_addr,
 931            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 932            p2i(start_address), p2i(prev_last_addr));
 933     size_used += ranges[i].byte_size();
 934     prev_last_addr = last_address;
 935 
 936     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 937     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 938 
 939     // Check for ranges that start in the same G1 region in which the previous
 940     // range ended, and adjust the start address so we don't try to free
 941     // the same region again. If the current range is entirely within that
 942     // region, skip it.
 943     if (start_region == prev_last_region) {
 944       start_address = start_region->end();
 945       if (start_address > last_address) {
 946         continue;
 947       }
 948       start_region = _hrm.addr_to_region(start_address);
 949     }
 950     prev_last_region = last_region;
 951 
 952     // After verifying that each region was marked as an archive region by
 953     // alloc_archive_regions, set it free and empty and uncommit it.
 954     HeapRegion* curr_region = start_region;
 955     while (curr_region != NULL) {
 956       guarantee(curr_region->is_archive(),
 957                 "Expected archive region at index %u", curr_region->hrm_index());
 958       uint curr_index = curr_region->hrm_index();
 959       _old_set.remove(curr_region);
 960       curr_region->set_free();
 961       curr_region->set_top(curr_region->bottom());
 962       if (curr_region != last_region) {
 963         curr_region = _hrm.next_region_in_heap(curr_region);
 964       } else {
 965         curr_region = NULL;
 966       }
 967       _hrm.shrink_at(curr_index, 1);
 968       uncommitted_regions++;
 969     }
 970 
 971     // Notify mark-sweep that this is no longer an archive range.
 972     G1MarkSweep::set_range_archive(ranges[i], false);
 973   }
 974 
 975   if (uncommitted_regions != 0) {
 976     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 977                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 978   }
 979   decrease_used(size_used);
 980 }
 981 
 982 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 983                                                         uint* gc_count_before_ret,
 984                                                         uint* gclocker_retry_count_ret) {
 985   // The structure of this method has a lot of similarities to
 986   // attempt_allocation_slow(). The reason these two were not merged
 987   // into a single one is that such a method would require several "if
 988   // allocation is not humongous do this, otherwise do that"
 989   // conditional paths which would obscure its flow. In fact, an early
 990   // version of this code did use a unified method which was harder to
 991   // follow and, as a result, it had subtle bugs that were hard to
 992   // track down. So keeping these two methods separate allows each to
 993   // be more readable. It will be good to keep these two in sync as
 994   // much as possible.
 995 
 996   assert_heap_not_locked_and_not_at_safepoint();
 997   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 998          "should only be called for humongous allocations");
 999 
1000   // Humongous objects can exhaust the heap quickly, so we should check if we
1001   // need to start a marking cycle at each humongous object allocation. We do
1002   // the check before we do the actual allocation. The reason for doing it
1003   // before the allocation is that we avoid having to keep track of the newly
1004   // allocated memory while we do a GC.
1005   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1006                                            word_size)) {
1007     collect(GCCause::_g1_humongous_allocation);
1008   }
1009 
1010   // We will loop until a) we manage to successfully perform the
1011   // allocation or b) we successfully schedule a collection which
1012   // fails to perform the allocation. b) is the only case when we'll
1013   // return NULL.
1014   HeapWord* result = NULL;
1015   for (int try_count = 1; /* we'll return */; try_count += 1) {
1016     bool should_try_gc;
1017     uint gc_count_before;
1018 
1019     {
1020       MutexLockerEx x(Heap_lock);
1021 
1022       // Given that humongous objects are not allocated in young
1023       // regions, we'll first try to do the allocation without doing a
1024       // collection hoping that there's enough space in the heap.
1025       result = humongous_obj_allocate(word_size, AllocationContext::current());
1026       if (result != NULL) {
1027         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
1028         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
1029         return result;
1030       }
1031 
1032       if (GCLocker::is_active_and_needs_gc()) {
1033         should_try_gc = false;
1034       } else {
1035          // The GCLocker may not be active but the GCLocker initiated
1036         // GC may not yet have been performed (GCLocker::needs_gc()
1037         // returns true). In this case we do not try this GC and
1038         // wait until the GCLocker initiated GC is performed, and
1039         // then retry the allocation.
1040         if (GCLocker::needs_gc()) {
1041           should_try_gc = false;
1042         } else {
1043           // Read the GC count while still holding the Heap_lock.
1044           gc_count_before = total_collections();
1045           should_try_gc = true;
1046         }
1047       }
1048     }
1049 
1050     if (should_try_gc) {
1051       // If we failed to allocate the humongous object, we should try to
1052       // do a collection pause (if we're allowed) in case it reclaims
1053       // enough space for the allocation to succeed after the pause.
1054 
1055       bool succeeded;
1056       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1057                                    GCCause::_g1_humongous_allocation);
1058       if (result != NULL) {
1059         assert(succeeded, "only way to get back a non-NULL result");
1060         return result;
1061       }
1062 
1063       if (succeeded) {
1064         // If we get here we successfully scheduled a collection which
1065         // failed to allocate. No point in trying to allocate
1066         // further. We'll just return NULL.
1067         MutexLockerEx x(Heap_lock);
1068         *gc_count_before_ret = total_collections();
1069         return NULL;
1070       }
1071     } else {
1072       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1073         MutexLockerEx x(Heap_lock);
1074         *gc_count_before_ret = total_collections();
1075         return NULL;
1076       }
1077       // The GCLocker is either active or the GCLocker initiated
1078       // GC has not yet been performed. Stall until it is and
1079       // then retry the allocation.
1080       GCLocker::stall_until_clear();
1081       (*gclocker_retry_count_ret) += 1;
1082     }
1083 
1084     // We can reach here if we were unsuccessful in scheduling a
1085     // collection (because another thread beat us to it) or if we were
1086     // stalled due to the GC locker. In either can we should retry the
1087     // allocation attempt in case another thread successfully
1088     // performed a collection and reclaimed enough space.  Give a
1089     // warning if we seem to be looping forever.
1090 
1091     if ((QueuedAllocationWarningCount > 0) &&
1092         (try_count % QueuedAllocationWarningCount == 0)) {
1093       warning("G1CollectedHeap::attempt_allocation_humongous() "
1094               "retries %d times", try_count);
1095     }
1096   }
1097 
1098   ShouldNotReachHere();
1099   return NULL;
1100 }
1101 
1102 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1103                                                            AllocationContext_t context,
1104                                                            bool expect_null_mutator_alloc_region) {
1105   assert_at_safepoint(true /* should_be_vm_thread */);
1106   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1107          "the current alloc region was unexpectedly found to be non-NULL");
1108 
1109   if (!is_humongous(word_size)) {
1110     return _allocator->attempt_allocation_locked(word_size, context);
1111   } else {
1112     HeapWord* result = humongous_obj_allocate(word_size, context);
1113     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1114       collector_state()->set_initiate_conc_mark_if_possible(true);
1115     }
1116     return result;
1117   }
1118 
1119   ShouldNotReachHere();
1120 }
1121 
1122 class PostMCRemSetClearClosure: public HeapRegionClosure {
1123   G1CollectedHeap* _g1h;
1124   ModRefBarrierSet* _mr_bs;
1125 public:
1126   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1127     _g1h(g1h), _mr_bs(mr_bs) {}
1128 
1129   bool doHeapRegion(HeapRegion* r) {
1130     HeapRegionRemSet* hrrs = r->rem_set();
1131 
1132     _g1h->reset_gc_time_stamps(r);
1133 
1134     if (r->is_continues_humongous()) {
1135       // We'll assert that the strong code root list and RSet is empty
1136       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1137       assert(hrrs->occupied() == 0, "RSet should be empty");
1138     } else {
1139       hrrs->clear();
1140     }
1141     // You might think here that we could clear just the cards
1142     // corresponding to the used region.  But no: if we leave a dirty card
1143     // in a region we might allocate into, then it would prevent that card
1144     // from being enqueued, and cause it to be missed.
1145     // Re: the performance cost: we shouldn't be doing full GC anyway!
1146     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1147 
1148     return false;
1149   }
1150 };
1151 
1152 void G1CollectedHeap::clear_rsets_post_compaction() {
1153   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1154   heap_region_iterate(&rs_clear);
1155 }
1156 
1157 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1158   G1CollectedHeap*   _g1h;
1159   UpdateRSOopClosure _cl;
1160 public:
1161   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1162     _cl(g1->g1_rem_set(), worker_i),
1163     _g1h(g1)
1164   { }
1165 
1166   bool doHeapRegion(HeapRegion* r) {
1167     if (!r->is_continues_humongous()) {
1168       _cl.set_from(r);
1169       r->oop_iterate(&_cl);
1170     }
1171     return false;
1172   }
1173 };
1174 
1175 class ParRebuildRSTask: public AbstractGangTask {
1176   G1CollectedHeap* _g1;
1177   HeapRegionClaimer _hrclaimer;
1178 
1179 public:
1180   ParRebuildRSTask(G1CollectedHeap* g1) :
1181       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1182 
1183   void work(uint worker_id) {
1184     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1185     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1186   }
1187 };
1188 
1189 class PostCompactionPrinterClosure: public HeapRegionClosure {
1190 private:
1191   G1HRPrinter* _hr_printer;
1192 public:
1193   bool doHeapRegion(HeapRegion* hr) {
1194     assert(!hr->is_young(), "not expecting to find young regions");
1195     _hr_printer->post_compaction(hr);
1196     return false;
1197   }
1198 
1199   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1200     : _hr_printer(hr_printer) { }
1201 };
1202 
1203 void G1CollectedHeap::print_hrm_post_compaction() {
1204   if (_hr_printer.is_active()) {
1205     PostCompactionPrinterClosure cl(hr_printer());
1206     heap_region_iterate(&cl);
1207   }
1208 
1209 }
1210 
1211 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1212                                          bool clear_all_soft_refs) {
1213   assert_at_safepoint(true /* should_be_vm_thread */);
1214 
1215   if (GCLocker::check_active_before_gc()) {
1216     return false;
1217   }
1218 
1219   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1220   gc_timer->register_gc_start();
1221 
1222   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1223   GCIdMark gc_id_mark;
1224   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1225 
1226   SvcGCMarker sgcm(SvcGCMarker::FULL);
1227   ResourceMark rm;
1228 
1229   print_heap_before_gc();
1230   trace_heap_before_gc(gc_tracer);
1231 
1232   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1233 
1234   _verifier->verify_region_sets_optional();
1235 
1236   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1237                            collector_policy()->should_clear_all_soft_refs();
1238 
1239   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1240 
1241   {
1242     IsGCActiveMark x;
1243 
1244     // Timing
1245     assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1246     GCTraceCPUTime tcpu;
1247 
1248     {
1249       GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1250       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1251       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1252 
1253       g1_policy()->record_full_collection_start();
1254 
1255       // Note: When we have a more flexible GC logging framework that
1256       // allows us to add optional attributes to a GC log record we
1257       // could consider timing and reporting how long we wait in the
1258       // following two methods.
1259       wait_while_free_regions_coming();
1260       // If we start the compaction before the CM threads finish
1261       // scanning the root regions we might trip them over as we'll
1262       // be moving objects / updating references. So let's wait until
1263       // they are done. By telling them to abort, they should complete
1264       // early.
1265       _cm->root_regions()->abort();
1266       _cm->root_regions()->wait_until_scan_finished();
1267       append_secondary_free_list_if_not_empty_with_lock();
1268 
1269       gc_prologue(true);
1270       increment_total_collections(true /* full gc */);
1271       increment_old_marking_cycles_started();
1272 
1273       assert(used() == recalculate_used(), "Should be equal");
1274 
1275       _verifier->verify_before_gc();
1276 
1277       _verifier->check_bitmaps("Full GC Start");
1278       pre_full_gc_dump(gc_timer);
1279 
1280 #if defined(COMPILER2) || INCLUDE_JVMCI
1281       DerivedPointerTable::clear();
1282 #endif
1283 
1284       // Disable discovery and empty the discovered lists
1285       // for the CM ref processor.
1286       ref_processor_cm()->disable_discovery();
1287       ref_processor_cm()->abandon_partial_discovery();
1288       ref_processor_cm()->verify_no_references_recorded();
1289 
1290       // Abandon current iterations of concurrent marking and concurrent
1291       // refinement, if any are in progress. We have to do this before
1292       // wait_until_scan_finished() below.
1293       concurrent_mark()->abort();
1294 
1295       // Make sure we'll choose a new allocation region afterwards.
1296       _allocator->release_mutator_alloc_region();
1297       _allocator->abandon_gc_alloc_regions();
1298       g1_rem_set()->cleanupHRRS();
1299 
1300       // We may have added regions to the current incremental collection
1301       // set between the last GC or pause and now. We need to clear the
1302       // incremental collection set and then start rebuilding it afresh
1303       // after this full GC.
1304       abandon_collection_set(g1_policy()->inc_cset_head());
1305       g1_policy()->clear_incremental_cset();
1306       g1_policy()->stop_incremental_cset_building();
1307 
1308       tear_down_region_sets(false /* free_list_only */);
1309       collector_state()->set_gcs_are_young(true);
1310 
1311       // See the comments in g1CollectedHeap.hpp and
1312       // G1CollectedHeap::ref_processing_init() about
1313       // how reference processing currently works in G1.
1314 
1315       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1316       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1317 
1318       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1319       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1320 
1321       ref_processor_stw()->enable_discovery();
1322       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1323 
1324       // Do collection work
1325       {
1326         HandleMark hm;  // Discard invalid handles created during gc
1327         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1328       }
1329 
1330       assert(num_free_regions() == 0, "we should not have added any free regions");
1331       rebuild_region_sets(false /* free_list_only */);
1332 
1333       // Enqueue any discovered reference objects that have
1334       // not been removed from the discovered lists.
1335       ref_processor_stw()->enqueue_discovered_references();
1336 
1337 #if defined(COMPILER2) || INCLUDE_JVMCI
1338       DerivedPointerTable::update_pointers();
1339 #endif
1340 
1341       MemoryService::track_memory_usage();
1342 
1343       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1344       ref_processor_stw()->verify_no_references_recorded();
1345 
1346       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1347       ClassLoaderDataGraph::purge();
1348       MetaspaceAux::verify_metrics();
1349 
1350       // Note: since we've just done a full GC, concurrent
1351       // marking is no longer active. Therefore we need not
1352       // re-enable reference discovery for the CM ref processor.
1353       // That will be done at the start of the next marking cycle.
1354       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1355       ref_processor_cm()->verify_no_references_recorded();
1356 
1357       reset_gc_time_stamp();
1358       // Since everything potentially moved, we will clear all remembered
1359       // sets, and clear all cards.  Later we will rebuild remembered
1360       // sets. We will also reset the GC time stamps of the regions.
1361       clear_rsets_post_compaction();
1362       check_gc_time_stamps();
1363 
1364       resize_if_necessary_after_full_collection();
1365 
1366       // We should do this after we potentially resize the heap so
1367       // that all the COMMIT / UNCOMMIT events are generated before
1368       // the compaction events.
1369       print_hrm_post_compaction();
1370 
1371       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1372       if (hot_card_cache->use_cache()) {
1373         hot_card_cache->reset_card_counts();
1374         hot_card_cache->reset_hot_cache();
1375       }
1376 
1377       // Rebuild remembered sets of all regions.
1378       uint n_workers =
1379         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1380                                                 workers()->active_workers(),
1381                                                 Threads::number_of_non_daemon_threads());
1382       workers()->set_active_workers(n_workers);
1383 
1384       ParRebuildRSTask rebuild_rs_task(this);
1385       workers()->run_task(&rebuild_rs_task);
1386 
1387       // Rebuild the strong code root lists for each region
1388       rebuild_strong_code_roots();
1389 
1390       if (true) { // FIXME
1391         MetaspaceGC::compute_new_size();
1392       }
1393 
1394 #ifdef TRACESPINNING
1395       ParallelTaskTerminator::print_termination_counts();
1396 #endif
1397 
1398       // Discard all rset updates
1399       JavaThread::dirty_card_queue_set().abandon_logs();
1400       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1401 
1402       _young_list->reset_sampled_info();
1403       // At this point there should be no regions in the
1404       // entire heap tagged as young.
1405       assert(check_young_list_empty(true /* check_heap */),
1406              "young list should be empty at this point");
1407 
1408       // Update the number of full collections that have been completed.
1409       increment_old_marking_cycles_completed(false /* concurrent */);
1410 
1411       _hrm.verify_optional();
1412       _verifier->verify_region_sets_optional();
1413 
1414       _verifier->verify_after_gc();
1415 
1416       // Clear the previous marking bitmap, if needed for bitmap verification.
1417       // Note we cannot do this when we clear the next marking bitmap in
1418       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1419       // objects marked during a full GC against the previous bitmap.
1420       // But we need to clear it before calling check_bitmaps below since
1421       // the full GC has compacted objects and updated TAMS but not updated
1422       // the prev bitmap.
1423       if (G1VerifyBitmaps) {
1424         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1425       }
1426       _verifier->check_bitmaps("Full GC End");
1427 
1428       // Start a new incremental collection set for the next pause
1429       assert(g1_policy()->collection_set() == NULL, "must be");
1430       g1_policy()->start_incremental_cset_building();
1431 
1432       clear_cset_fast_test();
1433 
1434       _allocator->init_mutator_alloc_region();
1435 
1436       g1_policy()->record_full_collection_end();
1437 
1438       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1439       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1440       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1441       // before any GC notifications are raised.
1442       g1mm()->update_sizes();
1443 
1444       gc_epilogue(true);
1445     }
1446 
1447     g1_policy()->print_detailed_heap_transition();
1448 
1449     print_heap_after_gc();
1450     trace_heap_after_gc(gc_tracer);
1451 
1452     post_full_gc_dump(gc_timer);
1453 
1454     gc_timer->register_gc_end();
1455     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1456   }
1457 
1458   return true;
1459 }
1460 
1461 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1462   // Currently, there is no facility in the do_full_collection(bool) API to notify
1463   // the caller that the collection did not succeed (e.g., because it was locked
1464   // out by the GC locker). So, right now, we'll ignore the return value.
1465   bool dummy = do_full_collection(true,                /* explicit_gc */
1466                                   clear_all_soft_refs);
1467 }
1468 
1469 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1470   // Include bytes that will be pre-allocated to support collections, as "used".
1471   const size_t used_after_gc = used();
1472   const size_t capacity_after_gc = capacity();
1473   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1474 
1475   // This is enforced in arguments.cpp.
1476   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1477          "otherwise the code below doesn't make sense");
1478 
1479   // We don't have floating point command-line arguments
1480   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1481   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1482   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1483   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1484 
1485   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1486   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1487 
1488   // We have to be careful here as these two calculations can overflow
1489   // 32-bit size_t's.
1490   double used_after_gc_d = (double) used_after_gc;
1491   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1492   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1493 
1494   // Let's make sure that they are both under the max heap size, which
1495   // by default will make them fit into a size_t.
1496   double desired_capacity_upper_bound = (double) max_heap_size;
1497   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1498                                     desired_capacity_upper_bound);
1499   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1500                                     desired_capacity_upper_bound);
1501 
1502   // We can now safely turn them into size_t's.
1503   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1504   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1505 
1506   // This assert only makes sense here, before we adjust them
1507   // with respect to the min and max heap size.
1508   assert(minimum_desired_capacity <= maximum_desired_capacity,
1509          "minimum_desired_capacity = " SIZE_FORMAT ", "
1510          "maximum_desired_capacity = " SIZE_FORMAT,
1511          minimum_desired_capacity, maximum_desired_capacity);
1512 
1513   // Should not be greater than the heap max size. No need to adjust
1514   // it with respect to the heap min size as it's a lower bound (i.e.,
1515   // we'll try to make the capacity larger than it, not smaller).
1516   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1517   // Should not be less than the heap min size. No need to adjust it
1518   // with respect to the heap max size as it's an upper bound (i.e.,
1519   // we'll try to make the capacity smaller than it, not greater).
1520   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1521 
1522   if (capacity_after_gc < minimum_desired_capacity) {
1523     // Don't expand unless it's significant
1524     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1525 
1526     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1527                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1528                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1529 
1530     expand(expand_bytes);
1531 
1532     // No expansion, now see if we want to shrink
1533   } else if (capacity_after_gc > maximum_desired_capacity) {
1534     // Capacity too large, compute shrinking size
1535     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1536 
1537     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1538                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1539                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1540 
1541     shrink(shrink_bytes);
1542   }
1543 }
1544 
1545 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1546                                                             AllocationContext_t context,
1547                                                             bool do_gc,
1548                                                             bool clear_all_soft_refs,
1549                                                             bool expect_null_mutator_alloc_region,
1550                                                             bool* gc_succeeded) {
1551   *gc_succeeded = true;
1552   // Let's attempt the allocation first.
1553   HeapWord* result =
1554     attempt_allocation_at_safepoint(word_size,
1555                                     context,
1556                                     expect_null_mutator_alloc_region);
1557   if (result != NULL) {
1558     assert(*gc_succeeded, "sanity");
1559     return result;
1560   }
1561 
1562   // In a G1 heap, we're supposed to keep allocation from failing by
1563   // incremental pauses.  Therefore, at least for now, we'll favor
1564   // expansion over collection.  (This might change in the future if we can
1565   // do something smarter than full collection to satisfy a failed alloc.)
1566   result = expand_and_allocate(word_size, context);
1567   if (result != NULL) {
1568     assert(*gc_succeeded, "sanity");
1569     return result;
1570   }
1571 
1572   if (do_gc) {
1573     // Expansion didn't work, we'll try to do a Full GC.
1574     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1575                                        clear_all_soft_refs);
1576   }
1577 
1578   return NULL;
1579 }
1580 
1581 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1582                                                      AllocationContext_t context,
1583                                                      bool* succeeded) {
1584   assert_at_safepoint(true /* should_be_vm_thread */);
1585 
1586   // Attempts to allocate followed by Full GC.
1587   HeapWord* result =
1588     satisfy_failed_allocation_helper(word_size,
1589                                      context,
1590                                      true,  /* do_gc */
1591                                      false, /* clear_all_soft_refs */
1592                                      false, /* expect_null_mutator_alloc_region */
1593                                      succeeded);
1594 
1595   if (result != NULL || !*succeeded) {
1596     return result;
1597   }
1598 
1599   // Attempts to allocate followed by Full GC that will collect all soft references.
1600   result = satisfy_failed_allocation_helper(word_size,
1601                                             context,
1602                                             true, /* do_gc */
1603                                             true, /* clear_all_soft_refs */
1604                                             true, /* expect_null_mutator_alloc_region */
1605                                             succeeded);
1606 
1607   if (result != NULL || !*succeeded) {
1608     return result;
1609   }
1610 
1611   // Attempts to allocate, no GC
1612   result = satisfy_failed_allocation_helper(word_size,
1613                                             context,
1614                                             false, /* do_gc */
1615                                             false, /* clear_all_soft_refs */
1616                                             true,  /* expect_null_mutator_alloc_region */
1617                                             succeeded);
1618 
1619   if (result != NULL) {
1620     assert(*succeeded, "sanity");
1621     return result;
1622   }
1623 
1624   assert(!collector_policy()->should_clear_all_soft_refs(),
1625          "Flag should have been handled and cleared prior to this point");
1626 
1627   // What else?  We might try synchronous finalization later.  If the total
1628   // space available is large enough for the allocation, then a more
1629   // complete compaction phase than we've tried so far might be
1630   // appropriate.
1631   assert(*succeeded, "sanity");
1632   return NULL;
1633 }
1634 
1635 // Attempting to expand the heap sufficiently
1636 // to support an allocation of the given "word_size".  If
1637 // successful, perform the allocation and return the address of the
1638 // allocated block, or else "NULL".
1639 
1640 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1641   assert_at_safepoint(true /* should_be_vm_thread */);
1642 
1643   _verifier->verify_region_sets_optional();
1644 
1645   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1646   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1647                             word_size * HeapWordSize);
1648 
1649 
1650   if (expand(expand_bytes)) {
1651     _hrm.verify_optional();
1652     _verifier->verify_region_sets_optional();
1653     return attempt_allocation_at_safepoint(word_size,
1654                                            context,
1655                                            false /* expect_null_mutator_alloc_region */);
1656   }
1657   return NULL;
1658 }
1659 
1660 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) {
1661   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1662   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1663                                        HeapRegion::GrainBytes);
1664 
1665   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B",
1666                             expand_bytes, aligned_expand_bytes);
1667 
1668   if (is_maximal_no_gc()) {
1669     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1670     return false;
1671   }
1672 
1673   double expand_heap_start_time_sec = os::elapsedTime();
1674   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1675   assert(regions_to_expand > 0, "Must expand by at least one region");
1676 
1677   uint expanded_by = _hrm.expand_by(regions_to_expand);
1678   if (expand_time_ms != NULL) {
1679     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1680   }
1681 
1682   if (expanded_by > 0) {
1683     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1684     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1685     g1_policy()->record_new_heap_size(num_regions());
1686   } else {
1687     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1688 
1689     // The expansion of the virtual storage space was unsuccessful.
1690     // Let's see if it was because we ran out of swap.
1691     if (G1ExitOnExpansionFailure &&
1692         _hrm.available() >= regions_to_expand) {
1693       // We had head room...
1694       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1695     }
1696   }
1697   return regions_to_expand > 0;
1698 }
1699 
1700 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1701   size_t aligned_shrink_bytes =
1702     ReservedSpace::page_align_size_down(shrink_bytes);
1703   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1704                                          HeapRegion::GrainBytes);
1705   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1706 
1707   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1708   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1709 
1710 
1711   log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B",
1712                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1713   if (num_regions_removed > 0) {
1714     g1_policy()->record_new_heap_size(num_regions());
1715   } else {
1716     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1717   }
1718 }
1719 
1720 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1721   _verifier->verify_region_sets_optional();
1722 
1723   // We should only reach here at the end of a Full GC which means we
1724   // should not not be holding to any GC alloc regions. The method
1725   // below will make sure of that and do any remaining clean up.
1726   _allocator->abandon_gc_alloc_regions();
1727 
1728   // Instead of tearing down / rebuilding the free lists here, we
1729   // could instead use the remove_all_pending() method on free_list to
1730   // remove only the ones that we need to remove.
1731   tear_down_region_sets(true /* free_list_only */);
1732   shrink_helper(shrink_bytes);
1733   rebuild_region_sets(true /* free_list_only */);
1734 
1735   _hrm.verify_optional();
1736   _verifier->verify_region_sets_optional();
1737 }
1738 
1739 // Public methods.
1740 
1741 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1742   CollectedHeap(),
1743   _g1_policy(policy_),
1744   _dirty_card_queue_set(false),
1745   _is_alive_closure_cm(this),
1746   _is_alive_closure_stw(this),
1747   _ref_processor_cm(NULL),
1748   _ref_processor_stw(NULL),
1749   _bot(NULL),
1750   _cg1r(NULL),
1751   _g1mm(NULL),
1752   _refine_cte_cl(NULL),
1753   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1754   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1755   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1756   _humongous_reclaim_candidates(),
1757   _has_humongous_reclaim_candidates(false),
1758   _archive_allocator(NULL),
1759   _free_regions_coming(false),
1760   _young_list(new YoungList(this)),
1761   _gc_time_stamp(0),
1762   _summary_bytes_used(0),
1763   _survivor_evac_stats(YoungPLABSize, PLABWeight),
1764   _old_evac_stats(OldPLABSize, PLABWeight),
1765   _expand_heap_after_alloc_failure(true),
1766   _old_marking_cycles_started(0),
1767   _old_marking_cycles_completed(0),
1768   _heap_summary_sent(false),
1769   _in_cset_fast_test(),
1770   _dirty_cards_region_list(NULL),
1771   _worker_cset_start_region(NULL),
1772   _worker_cset_start_region_time_stamp(NULL),
1773   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1774   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1775   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1776   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1777 
1778   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1779                           /* are_GC_task_threads */true,
1780                           /* are_ConcurrentGC_threads */false);
1781   _workers->initialize_workers();
1782   _verifier = new G1HeapVerifier(this);
1783 
1784   _allocator = G1Allocator::create_allocator(this);
1785   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1786 
1787   // Override the default _filler_array_max_size so that no humongous filler
1788   // objects are created.
1789   _filler_array_max_size = _humongous_object_threshold_in_words;
1790 
1791   uint n_queues = ParallelGCThreads;
1792   _task_queues = new RefToScanQueueSet(n_queues);
1793 
1794   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1795   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1796   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1797 
1798   for (uint i = 0; i < n_queues; i++) {
1799     RefToScanQueue* q = new RefToScanQueue();
1800     q->initialize();
1801     _task_queues->register_queue(i, q);
1802     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1803   }
1804   clear_cset_start_regions();
1805 
1806   // Initialize the G1EvacuationFailureALot counters and flags.
1807   NOT_PRODUCT(reset_evacuation_should_fail();)
1808 
1809   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1810 }
1811 
1812 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1813                                                                  size_t size,
1814                                                                  size_t translation_factor) {
1815   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1816   // Allocate a new reserved space, preferring to use large pages.
1817   ReservedSpace rs(size, preferred_page_size);
1818   G1RegionToSpaceMapper* result  =
1819     G1RegionToSpaceMapper::create_mapper(rs,
1820                                          size,
1821                                          rs.alignment(),
1822                                          HeapRegion::GrainBytes,
1823                                          translation_factor,
1824                                          mtGC);
1825   if (TracePageSizes) {
1826     tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1827                   description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1828   }
1829   return result;
1830 }
1831 
1832 jint G1CollectedHeap::initialize() {
1833   CollectedHeap::pre_initialize();
1834   os::enable_vtime();
1835 
1836   // Necessary to satisfy locking discipline assertions.
1837 
1838   MutexLocker x(Heap_lock);
1839 
1840   // While there are no constraints in the GC code that HeapWordSize
1841   // be any particular value, there are multiple other areas in the
1842   // system which believe this to be true (e.g. oop->object_size in some
1843   // cases incorrectly returns the size in wordSize units rather than
1844   // HeapWordSize).
1845   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1846 
1847   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1848   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1849   size_t heap_alignment = collector_policy()->heap_alignment();
1850 
1851   // Ensure that the sizes are properly aligned.
1852   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1853   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1854   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1855 
1856   _refine_cte_cl = new RefineCardTableEntryClosure();
1857 
1858   jint ecode = JNI_OK;
1859   _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode);
1860   if (_cg1r == NULL) {
1861     return ecode;
1862   }
1863 
1864   // Reserve the maximum.
1865 
1866   // When compressed oops are enabled, the preferred heap base
1867   // is calculated by subtracting the requested size from the
1868   // 32Gb boundary and using the result as the base address for
1869   // heap reservation. If the requested size is not aligned to
1870   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1871   // into the ReservedHeapSpace constructor) then the actual
1872   // base of the reserved heap may end up differing from the
1873   // address that was requested (i.e. the preferred heap base).
1874   // If this happens then we could end up using a non-optimal
1875   // compressed oops mode.
1876 
1877   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1878                                                  heap_alignment);
1879 
1880   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1881 
1882   // Create the barrier set for the entire reserved region.
1883   G1SATBCardTableLoggingModRefBS* bs
1884     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1885   bs->initialize();
1886   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1887   set_barrier_set(bs);
1888 
1889   // Also create a G1 rem set.
1890   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1891 
1892   // Carve out the G1 part of the heap.
1893   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1894   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1895   G1RegionToSpaceMapper* heap_storage =
1896     G1RegionToSpaceMapper::create_mapper(g1_rs,
1897                                          g1_rs.size(),
1898                                          page_size,
1899                                          HeapRegion::GrainBytes,
1900                                          1,
1901                                          mtJavaHeap);
1902   os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(),
1903                        max_byte_size, page_size,
1904                        heap_rs.base(),
1905                        heap_rs.size());
1906   heap_storage->set_mapping_changed_listener(&_listener);
1907 
1908   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1909   G1RegionToSpaceMapper* bot_storage =
1910     create_aux_memory_mapper("Block offset table",
1911                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1912                              G1BlockOffsetTable::heap_map_factor());
1913 
1914   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1915   G1RegionToSpaceMapper* cardtable_storage =
1916     create_aux_memory_mapper("Card table",
1917                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1918                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1919 
1920   G1RegionToSpaceMapper* card_counts_storage =
1921     create_aux_memory_mapper("Card counts table",
1922                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1923                              G1CardCounts::heap_map_factor());
1924 
1925   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1926   G1RegionToSpaceMapper* prev_bitmap_storage =
1927     create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1928   G1RegionToSpaceMapper* next_bitmap_storage =
1929     create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1930 
1931   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1932   g1_barrier_set()->initialize(cardtable_storage);
1933    // Do later initialization work for concurrent refinement.
1934   _cg1r->init(card_counts_storage);
1935 
1936   // 6843694 - ensure that the maximum region index can fit
1937   // in the remembered set structures.
1938   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1939   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1940 
1941   G1RemSet::initialize(max_regions());
1942 
1943   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1944   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1945   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1946             "too many cards per region");
1947 
1948   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1949 
1950   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1951 
1952   {
1953     HeapWord* start = _hrm.reserved().start();
1954     HeapWord* end = _hrm.reserved().end();
1955     size_t granularity = HeapRegion::GrainBytes;
1956 
1957     _in_cset_fast_test.initialize(start, end, granularity);
1958     _humongous_reclaim_candidates.initialize(start, end, granularity);
1959   }
1960 
1961   // Create the ConcurrentMark data structure and thread.
1962   // (Must do this late, so that "max_regions" is defined.)
1963   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1964   if (_cm == NULL || !_cm->completed_initialization()) {
1965     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1966     return JNI_ENOMEM;
1967   }
1968   _cmThread = _cm->cmThread();
1969 
1970   // Now expand into the initial heap size.
1971   if (!expand(init_byte_size)) {
1972     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1973     return JNI_ENOMEM;
1974   }
1975 
1976   // Perform any initialization actions delegated to the policy.
1977   g1_policy()->init();
1978 
1979   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1980                                                SATB_Q_FL_lock,
1981                                                G1SATBProcessCompletedThreshold,
1982                                                Shared_SATB_Q_lock);
1983 
1984   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1985                                                 DirtyCardQ_CBL_mon,
1986                                                 DirtyCardQ_FL_lock,
1987                                                 concurrent_g1_refine()->yellow_zone(),
1988                                                 concurrent_g1_refine()->red_zone(),
1989                                                 Shared_DirtyCardQ_lock,
1990                                                 NULL,  // fl_owner
1991                                                 true); // init_free_ids
1992 
1993   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1994                                     DirtyCardQ_CBL_mon,
1995                                     DirtyCardQ_FL_lock,
1996                                     -1, // never trigger processing
1997                                     -1, // no limit on length
1998                                     Shared_DirtyCardQ_lock,
1999                                     &JavaThread::dirty_card_queue_set());
2000 
2001   // Here we allocate the dummy HeapRegion that is required by the
2002   // G1AllocRegion class.
2003   HeapRegion* dummy_region = _hrm.get_dummy_region();
2004 
2005   // We'll re-use the same region whether the alloc region will
2006   // require BOT updates or not and, if it doesn't, then a non-young
2007   // region will complain that it cannot support allocations without
2008   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2009   dummy_region->set_eden();
2010   // Make sure it's full.
2011   dummy_region->set_top(dummy_region->end());
2012   G1AllocRegion::setup(this, dummy_region);
2013 
2014   _allocator->init_mutator_alloc_region();
2015 
2016   // Do create of the monitoring and management support so that
2017   // values in the heap have been properly initialized.
2018   _g1mm = new G1MonitoringSupport(this);
2019 
2020   G1StringDedup::initialize();
2021 
2022   _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC);
2023   for (uint i = 0; i < ParallelGCThreads; i++) {
2024     new (&_preserved_objs[i]) OopAndMarkOopStack();
2025   }
2026 
2027   return JNI_OK;
2028 }
2029 
2030 void G1CollectedHeap::stop() {
2031   // Stop all concurrent threads. We do this to make sure these threads
2032   // do not continue to execute and access resources (e.g. logging)
2033   // that are destroyed during shutdown.
2034   _cg1r->stop();
2035   _cmThread->stop();
2036   if (G1StringDedup::is_enabled()) {
2037     G1StringDedup::stop();
2038   }
2039 }
2040 
2041 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2042   return HeapRegion::max_region_size();
2043 }
2044 
2045 void G1CollectedHeap::post_initialize() {
2046   CollectedHeap::post_initialize();
2047   ref_processing_init();
2048 }
2049 
2050 void G1CollectedHeap::ref_processing_init() {
2051   // Reference processing in G1 currently works as follows:
2052   //
2053   // * There are two reference processor instances. One is
2054   //   used to record and process discovered references
2055   //   during concurrent marking; the other is used to
2056   //   record and process references during STW pauses
2057   //   (both full and incremental).
2058   // * Both ref processors need to 'span' the entire heap as
2059   //   the regions in the collection set may be dotted around.
2060   //
2061   // * For the concurrent marking ref processor:
2062   //   * Reference discovery is enabled at initial marking.
2063   //   * Reference discovery is disabled and the discovered
2064   //     references processed etc during remarking.
2065   //   * Reference discovery is MT (see below).
2066   //   * Reference discovery requires a barrier (see below).
2067   //   * Reference processing may or may not be MT
2068   //     (depending on the value of ParallelRefProcEnabled
2069   //     and ParallelGCThreads).
2070   //   * A full GC disables reference discovery by the CM
2071   //     ref processor and abandons any entries on it's
2072   //     discovered lists.
2073   //
2074   // * For the STW processor:
2075   //   * Non MT discovery is enabled at the start of a full GC.
2076   //   * Processing and enqueueing during a full GC is non-MT.
2077   //   * During a full GC, references are processed after marking.
2078   //
2079   //   * Discovery (may or may not be MT) is enabled at the start
2080   //     of an incremental evacuation pause.
2081   //   * References are processed near the end of a STW evacuation pause.
2082   //   * For both types of GC:
2083   //     * Discovery is atomic - i.e. not concurrent.
2084   //     * Reference discovery will not need a barrier.
2085 
2086   MemRegion mr = reserved_region();
2087 
2088   // Concurrent Mark ref processor
2089   _ref_processor_cm =
2090     new ReferenceProcessor(mr,    // span
2091                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2092                                 // mt processing
2093                            ParallelGCThreads,
2094                                 // degree of mt processing
2095                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2096                                 // mt discovery
2097                            MAX2(ParallelGCThreads, ConcGCThreads),
2098                                 // degree of mt discovery
2099                            false,
2100                                 // Reference discovery is not atomic
2101                            &_is_alive_closure_cm);
2102                                 // is alive closure
2103                                 // (for efficiency/performance)
2104 
2105   // STW ref processor
2106   _ref_processor_stw =
2107     new ReferenceProcessor(mr,    // span
2108                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2109                                 // mt processing
2110                            ParallelGCThreads,
2111                                 // degree of mt processing
2112                            (ParallelGCThreads > 1),
2113                                 // mt discovery
2114                            ParallelGCThreads,
2115                                 // degree of mt discovery
2116                            true,
2117                                 // Reference discovery is atomic
2118                            &_is_alive_closure_stw);
2119                                 // is alive closure
2120                                 // (for efficiency/performance)
2121 }
2122 
2123 CollectorPolicy* G1CollectedHeap::collector_policy() const {
2124   return g1_policy();
2125 }
2126 
2127 size_t G1CollectedHeap::capacity() const {
2128   return _hrm.length() * HeapRegion::GrainBytes;
2129 }
2130 
2131 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2132   hr->reset_gc_time_stamp();
2133 }
2134 
2135 #ifndef PRODUCT
2136 
2137 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2138 private:
2139   unsigned _gc_time_stamp;
2140   bool _failures;
2141 
2142 public:
2143   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2144     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2145 
2146   virtual bool doHeapRegion(HeapRegion* hr) {
2147     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2148     if (_gc_time_stamp != region_gc_time_stamp) {
2149       log_info(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
2150                            region_gc_time_stamp, _gc_time_stamp);
2151       _failures = true;
2152     }
2153     return false;
2154   }
2155 
2156   bool failures() { return _failures; }
2157 };
2158 
2159 void G1CollectedHeap::check_gc_time_stamps() {
2160   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2161   heap_region_iterate(&cl);
2162   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2163 }
2164 #endif // PRODUCT
2165 
2166 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2167   _cg1r->hot_card_cache()->drain(cl, worker_i);
2168 }
2169 
2170 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2171   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2172   size_t n_completed_buffers = 0;
2173   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2174     n_completed_buffers++;
2175   }
2176   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2177   dcqs.clear_n_completed_buffers();
2178   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2179 }
2180 
2181 // Computes the sum of the storage used by the various regions.
2182 size_t G1CollectedHeap::used() const {
2183   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2184   if (_archive_allocator != NULL) {
2185     result += _archive_allocator->used();
2186   }
2187   return result;
2188 }
2189 
2190 size_t G1CollectedHeap::used_unlocked() const {
2191   return _summary_bytes_used;
2192 }
2193 
2194 class SumUsedClosure: public HeapRegionClosure {
2195   size_t _used;
2196 public:
2197   SumUsedClosure() : _used(0) {}
2198   bool doHeapRegion(HeapRegion* r) {
2199     _used += r->used();
2200     return false;
2201   }
2202   size_t result() { return _used; }
2203 };
2204 
2205 size_t G1CollectedHeap::recalculate_used() const {
2206   double recalculate_used_start = os::elapsedTime();
2207 
2208   SumUsedClosure blk;
2209   heap_region_iterate(&blk);
2210 
2211   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2212   return blk.result();
2213 }
2214 
2215 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2216   switch (cause) {
2217     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2218     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2219     case GCCause::_update_allocation_context_stats_inc: return true;
2220     case GCCause::_wb_conc_mark:                        return true;
2221     default :                                           return false;
2222   }
2223 }
2224 
2225 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2226   switch (cause) {
2227     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2228     case GCCause::_g1_humongous_allocation: return true;
2229     default:                                return is_user_requested_concurrent_full_gc(cause);
2230   }
2231 }
2232 
2233 #ifndef PRODUCT
2234 void G1CollectedHeap::allocate_dummy_regions() {
2235   // Let's fill up most of the region
2236   size_t word_size = HeapRegion::GrainWords - 1024;
2237   // And as a result the region we'll allocate will be humongous.
2238   guarantee(is_humongous(word_size), "sanity");
2239 
2240   // _filler_array_max_size is set to humongous object threshold
2241   // but temporarily change it to use CollectedHeap::fill_with_object().
2242   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2243 
2244   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2245     // Let's use the existing mechanism for the allocation
2246     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2247                                                  AllocationContext::system());
2248     if (dummy_obj != NULL) {
2249       MemRegion mr(dummy_obj, word_size);
2250       CollectedHeap::fill_with_object(mr);
2251     } else {
2252       // If we can't allocate once, we probably cannot allocate
2253       // again. Let's get out of the loop.
2254       break;
2255     }
2256   }
2257 }
2258 #endif // !PRODUCT
2259 
2260 void G1CollectedHeap::increment_old_marking_cycles_started() {
2261   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2262          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2263          "Wrong marking cycle count (started: %d, completed: %d)",
2264          _old_marking_cycles_started, _old_marking_cycles_completed);
2265 
2266   _old_marking_cycles_started++;
2267 }
2268 
2269 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2270   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2271 
2272   // We assume that if concurrent == true, then the caller is a
2273   // concurrent thread that was joined the Suspendible Thread
2274   // Set. If there's ever a cheap way to check this, we should add an
2275   // assert here.
2276 
2277   // Given that this method is called at the end of a Full GC or of a
2278   // concurrent cycle, and those can be nested (i.e., a Full GC can
2279   // interrupt a concurrent cycle), the number of full collections
2280   // completed should be either one (in the case where there was no
2281   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2282   // behind the number of full collections started.
2283 
2284   // This is the case for the inner caller, i.e. a Full GC.
2285   assert(concurrent ||
2286          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2287          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2288          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2289          "is inconsistent with _old_marking_cycles_completed = %u",
2290          _old_marking_cycles_started, _old_marking_cycles_completed);
2291 
2292   // This is the case for the outer caller, i.e. the concurrent cycle.
2293   assert(!concurrent ||
2294          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2295          "for outer caller (concurrent cycle): "
2296          "_old_marking_cycles_started = %u "
2297          "is inconsistent with _old_marking_cycles_completed = %u",
2298          _old_marking_cycles_started, _old_marking_cycles_completed);
2299 
2300   _old_marking_cycles_completed += 1;
2301 
2302   // We need to clear the "in_progress" flag in the CM thread before
2303   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2304   // is set) so that if a waiter requests another System.gc() it doesn't
2305   // incorrectly see that a marking cycle is still in progress.
2306   if (concurrent) {
2307     _cmThread->set_idle();
2308   }
2309 
2310   // This notify_all() will ensure that a thread that called
2311   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2312   // and it's waiting for a full GC to finish will be woken up. It is
2313   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2314   FullGCCount_lock->notify_all();
2315 }
2316 
2317 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2318   GCIdMarkAndRestore conc_gc_id_mark;
2319   collector_state()->set_concurrent_cycle_started(true);
2320   _gc_timer_cm->register_gc_start(start_time);
2321 
2322   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2323   trace_heap_before_gc(_gc_tracer_cm);
2324   _cmThread->set_gc_id(GCId::current());
2325 }
2326 
2327 void G1CollectedHeap::register_concurrent_cycle_end() {
2328   if (collector_state()->concurrent_cycle_started()) {
2329     GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id());
2330     if (_cm->has_aborted()) {
2331       _gc_tracer_cm->report_concurrent_mode_failure();
2332     }
2333 
2334     _gc_timer_cm->register_gc_end();
2335     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2336 
2337     // Clear state variables to prepare for the next concurrent cycle.
2338     collector_state()->set_concurrent_cycle_started(false);
2339     _heap_summary_sent = false;
2340   }
2341 }
2342 
2343 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2344   if (collector_state()->concurrent_cycle_started()) {
2345     // This function can be called when:
2346     //  the cleanup pause is run
2347     //  the concurrent cycle is aborted before the cleanup pause.
2348     //  the concurrent cycle is aborted after the cleanup pause,
2349     //   but before the concurrent cycle end has been registered.
2350     // Make sure that we only send the heap information once.
2351     if (!_heap_summary_sent) {
2352       GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id());
2353       trace_heap_after_gc(_gc_tracer_cm);
2354       _heap_summary_sent = true;
2355     }
2356   }
2357 }
2358 
2359 void G1CollectedHeap::collect(GCCause::Cause cause) {
2360   assert_heap_not_locked();
2361 
2362   uint gc_count_before;
2363   uint old_marking_count_before;
2364   uint full_gc_count_before;
2365   bool retry_gc;
2366 
2367   do {
2368     retry_gc = false;
2369 
2370     {
2371       MutexLocker ml(Heap_lock);
2372 
2373       // Read the GC count while holding the Heap_lock
2374       gc_count_before = total_collections();
2375       full_gc_count_before = total_full_collections();
2376       old_marking_count_before = _old_marking_cycles_started;
2377     }
2378 
2379     if (should_do_concurrent_full_gc(cause)) {
2380       // Schedule an initial-mark evacuation pause that will start a
2381       // concurrent cycle. We're setting word_size to 0 which means that
2382       // we are not requesting a post-GC allocation.
2383       VM_G1IncCollectionPause op(gc_count_before,
2384                                  0,     /* word_size */
2385                                  true,  /* should_initiate_conc_mark */
2386                                  g1_policy()->max_pause_time_ms(),
2387                                  cause);
2388       op.set_allocation_context(AllocationContext::current());
2389 
2390       VMThread::execute(&op);
2391       if (!op.pause_succeeded()) {
2392         if (old_marking_count_before == _old_marking_cycles_started) {
2393           retry_gc = op.should_retry_gc();
2394         } else {
2395           // A Full GC happened while we were trying to schedule the
2396           // initial-mark GC. No point in starting a new cycle given
2397           // that the whole heap was collected anyway.
2398         }
2399 
2400         if (retry_gc) {
2401           if (GCLocker::is_active_and_needs_gc()) {
2402             GCLocker::stall_until_clear();
2403           }
2404         }
2405       }
2406     } else {
2407       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2408           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2409 
2410         // Schedule a standard evacuation pause. We're setting word_size
2411         // to 0 which means that we are not requesting a post-GC allocation.
2412         VM_G1IncCollectionPause op(gc_count_before,
2413                                    0,     /* word_size */
2414                                    false, /* should_initiate_conc_mark */
2415                                    g1_policy()->max_pause_time_ms(),
2416                                    cause);
2417         VMThread::execute(&op);
2418       } else {
2419         // Schedule a Full GC.
2420         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2421         VMThread::execute(&op);
2422       }
2423     }
2424   } while (retry_gc);
2425 }
2426 
2427 bool G1CollectedHeap::is_in(const void* p) const {
2428   if (_hrm.reserved().contains(p)) {
2429     // Given that we know that p is in the reserved space,
2430     // heap_region_containing() should successfully
2431     // return the containing region.
2432     HeapRegion* hr = heap_region_containing(p);
2433     return hr->is_in(p);
2434   } else {
2435     return false;
2436   }
2437 }
2438 
2439 #ifdef ASSERT
2440 bool G1CollectedHeap::is_in_exact(const void* p) const {
2441   bool contains = reserved_region().contains(p);
2442   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2443   if (contains && available) {
2444     return true;
2445   } else {
2446     return false;
2447   }
2448 }
2449 #endif
2450 
2451 bool G1CollectedHeap::obj_in_cs(oop obj) {
2452   HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj);
2453   return r != NULL && r->in_collection_set();
2454 }
2455 
2456 // Iteration functions.
2457 
2458 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2459 
2460 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2461   ExtendedOopClosure* _cl;
2462 public:
2463   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2464   bool doHeapRegion(HeapRegion* r) {
2465     if (!r->is_continues_humongous()) {
2466       r->oop_iterate(_cl);
2467     }
2468     return false;
2469   }
2470 };
2471 
2472 // Iterates an ObjectClosure over all objects within a HeapRegion.
2473 
2474 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2475   ObjectClosure* _cl;
2476 public:
2477   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2478   bool doHeapRegion(HeapRegion* r) {
2479     if (!r->is_continues_humongous()) {
2480       r->object_iterate(_cl);
2481     }
2482     return false;
2483   }
2484 };
2485 
2486 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2487   IterateObjectClosureRegionClosure blk(cl);
2488   heap_region_iterate(&blk);
2489 }
2490 
2491 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2492   _hrm.iterate(cl);
2493 }
2494 
2495 void
2496 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2497                                          uint worker_id,
2498                                          HeapRegionClaimer *hrclaimer,
2499                                          bool concurrent) const {
2500   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2501 }
2502 
2503 // Clear the cached CSet starting regions and (more importantly)
2504 // the time stamps. Called when we reset the GC time stamp.
2505 void G1CollectedHeap::clear_cset_start_regions() {
2506   assert(_worker_cset_start_region != NULL, "sanity");
2507   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2508 
2509   for (uint i = 0; i < ParallelGCThreads; i++) {
2510     _worker_cset_start_region[i] = NULL;
2511     _worker_cset_start_region_time_stamp[i] = 0;
2512   }
2513 }
2514 
2515 // Given the id of a worker, obtain or calculate a suitable
2516 // starting region for iterating over the current collection set.
2517 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2518   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2519 
2520   HeapRegion* result = NULL;
2521   unsigned gc_time_stamp = get_gc_time_stamp();
2522 
2523   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2524     // Cached starting region for current worker was set
2525     // during the current pause - so it's valid.
2526     // Note: the cached starting heap region may be NULL
2527     // (when the collection set is empty).
2528     result = _worker_cset_start_region[worker_i];
2529     assert(result == NULL || result->in_collection_set(), "sanity");
2530     return result;
2531   }
2532 
2533   // The cached entry was not valid so let's calculate
2534   // a suitable starting heap region for this worker.
2535 
2536   // We want the parallel threads to start their collection
2537   // set iteration at different collection set regions to
2538   // avoid contention.
2539   // If we have:
2540   //          n collection set regions
2541   //          p threads
2542   // Then thread t will start at region floor ((t * n) / p)
2543 
2544   result = g1_policy()->collection_set();
2545   uint cs_size = g1_policy()->cset_region_length();
2546   uint active_workers = workers()->active_workers();
2547 
2548   uint end_ind   = (cs_size * worker_i) / active_workers;
2549   uint start_ind = 0;
2550 
2551   if (worker_i > 0 &&
2552       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2553     // Previous workers starting region is valid
2554     // so let's iterate from there
2555     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2556     OrderAccess::loadload();
2557     result = _worker_cset_start_region[worker_i - 1];
2558   }
2559 
2560   for (uint i = start_ind; i < end_ind; i++) {
2561     result = result->next_in_collection_set();
2562   }
2563 
2564   // Note: the calculated starting heap region may be NULL
2565   // (when the collection set is empty).
2566   assert(result == NULL || result->in_collection_set(), "sanity");
2567   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2568          "should be updated only once per pause");
2569   _worker_cset_start_region[worker_i] = result;
2570   OrderAccess::storestore();
2571   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2572   return result;
2573 }
2574 
2575 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2576   HeapRegion* r = g1_policy()->collection_set();
2577   while (r != NULL) {
2578     HeapRegion* next = r->next_in_collection_set();
2579     if (cl->doHeapRegion(r)) {
2580       cl->incomplete();
2581       return;
2582     }
2583     r = next;
2584   }
2585 }
2586 
2587 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2588                                                   HeapRegionClosure *cl) {
2589   if (r == NULL) {
2590     // The CSet is empty so there's nothing to do.
2591     return;
2592   }
2593 
2594   assert(r->in_collection_set(),
2595          "Start region must be a member of the collection set.");
2596   HeapRegion* cur = r;
2597   while (cur != NULL) {
2598     HeapRegion* next = cur->next_in_collection_set();
2599     if (cl->doHeapRegion(cur) && false) {
2600       cl->incomplete();
2601       return;
2602     }
2603     cur = next;
2604   }
2605   cur = g1_policy()->collection_set();
2606   while (cur != r) {
2607     HeapRegion* next = cur->next_in_collection_set();
2608     if (cl->doHeapRegion(cur) && false) {
2609       cl->incomplete();
2610       return;
2611     }
2612     cur = next;
2613   }
2614 }
2615 
2616 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2617   HeapRegion* result = _hrm.next_region_in_heap(from);
2618   while (result != NULL && result->is_pinned()) {
2619     result = _hrm.next_region_in_heap(result);
2620   }
2621   return result;
2622 }
2623 
2624 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2625   HeapRegion* hr = heap_region_containing(addr);
2626   return hr->block_start(addr);
2627 }
2628 
2629 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2630   HeapRegion* hr = heap_region_containing(addr);
2631   return hr->block_size(addr);
2632 }
2633 
2634 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2635   HeapRegion* hr = heap_region_containing(addr);
2636   return hr->block_is_obj(addr);
2637 }
2638 
2639 bool G1CollectedHeap::supports_tlab_allocation() const {
2640   return true;
2641 }
2642 
2643 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2644   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2645 }
2646 
2647 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2648   return young_list()->eden_used_bytes();
2649 }
2650 
2651 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2652 // must be equal to the humongous object limit.
2653 size_t G1CollectedHeap::max_tlab_size() const {
2654   return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
2655 }
2656 
2657 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2658   AllocationContext_t context = AllocationContext::current();
2659   return _allocator->unsafe_max_tlab_alloc(context);
2660 }
2661 
2662 size_t G1CollectedHeap::max_capacity() const {
2663   return _hrm.reserved().byte_size();
2664 }
2665 
2666 jlong G1CollectedHeap::millis_since_last_gc() {
2667   // assert(false, "NYI");
2668   return 0;
2669 }
2670 
2671 void G1CollectedHeap::prepare_for_verify() {
2672   _verifier->prepare_for_verify();
2673 }
2674 
2675 class PrintRegionClosure: public HeapRegionClosure {
2676   outputStream* _st;
2677 public:
2678   PrintRegionClosure(outputStream* st) : _st(st) {}
2679   bool doHeapRegion(HeapRegion* r) {
2680     r->print_on(_st);
2681     return false;
2682   }
2683 };
2684 
2685 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2686                                        const HeapRegion* hr,
2687                                        const VerifyOption vo) const {
2688   switch (vo) {
2689   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2690   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2691   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked() && !hr->is_archive();
2692   default:                            ShouldNotReachHere();
2693   }
2694   return false; // keep some compilers happy
2695 }
2696 
2697 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2698                                        const VerifyOption vo) const {
2699   switch (vo) {
2700   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2701   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2702   case VerifyOption_G1UseMarkWord: {
2703     HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2704     return !obj->is_gc_marked() && !hr->is_archive();
2705   }
2706   default:                            ShouldNotReachHere();
2707   }
2708   return false; // keep some compilers happy
2709 }
2710 
2711 void G1CollectedHeap::print_on(outputStream* st) const {
2712   st->print(" %-20s", "garbage-first heap");
2713   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2714             capacity()/K, used_unlocked()/K);
2715   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2716             p2i(_hrm.reserved().start()),
2717             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2718             p2i(_hrm.reserved().end()));
2719   st->cr();
2720   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2721   uint young_regions = _young_list->length();
2722   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2723             (size_t) young_regions * HeapRegion::GrainBytes / K);
2724   uint survivor_regions = g1_policy()->recorded_survivor_regions();
2725   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2726             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2727   st->cr();
2728   MetaspaceAux::print_on(st);
2729 }
2730 
2731 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2732   print_on(st);
2733 
2734   // Print the per-region information.
2735   st->cr();
2736   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2737                "HS=humongous(starts), HC=humongous(continues), "
2738                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2739                "AC=allocation context, "
2740                "TAMS=top-at-mark-start (previous, next)");
2741   PrintRegionClosure blk(st);
2742   heap_region_iterate(&blk);
2743 }
2744 
2745 void G1CollectedHeap::print_on_error(outputStream* st) const {
2746   this->CollectedHeap::print_on_error(st);
2747 
2748   if (_cm != NULL) {
2749     st->cr();
2750     _cm->print_on_error(st);
2751   }
2752 }
2753 
2754 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2755   workers()->print_worker_threads_on(st);
2756   _cmThread->print_on(st);
2757   st->cr();
2758   _cm->print_worker_threads_on(st);
2759   _cg1r->print_worker_threads_on(st);
2760   if (G1StringDedup::is_enabled()) {
2761     G1StringDedup::print_worker_threads_on(st);
2762   }
2763 }
2764 
2765 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2766   workers()->threads_do(tc);
2767   tc->do_thread(_cmThread);
2768   _cg1r->threads_do(tc);
2769   if (G1StringDedup::is_enabled()) {
2770     G1StringDedup::threads_do(tc);
2771   }
2772 }
2773 
2774 void G1CollectedHeap::print_tracing_info() const {
2775   // We'll overload this to mean "trace GC pause statistics."
2776   if (TraceYoungGenTime || TraceOldGenTime) {
2777     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
2778     // to that.
2779     g1_policy()->print_tracing_info();
2780   }
2781   g1_rem_set()->print_summary_info();
2782   concurrent_mark()->print_summary_info();
2783   g1_policy()->print_yg_surv_rate_info();
2784 }
2785 
2786 #ifndef PRODUCT
2787 // Helpful for debugging RSet issues.
2788 
2789 class PrintRSetsClosure : public HeapRegionClosure {
2790 private:
2791   const char* _msg;
2792   size_t _occupied_sum;
2793 
2794 public:
2795   bool doHeapRegion(HeapRegion* r) {
2796     HeapRegionRemSet* hrrs = r->rem_set();
2797     size_t occupied = hrrs->occupied();
2798     _occupied_sum += occupied;
2799 
2800     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2801     if (occupied == 0) {
2802       tty->print_cr("  RSet is empty");
2803     } else {
2804       hrrs->print();
2805     }
2806     tty->print_cr("----------");
2807     return false;
2808   }
2809 
2810   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2811     tty->cr();
2812     tty->print_cr("========================================");
2813     tty->print_cr("%s", msg);
2814     tty->cr();
2815   }
2816 
2817   ~PrintRSetsClosure() {
2818     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2819     tty->print_cr("========================================");
2820     tty->cr();
2821   }
2822 };
2823 
2824 void G1CollectedHeap::print_cset_rsets() {
2825   PrintRSetsClosure cl("Printing CSet RSets");
2826   collection_set_iterate(&cl);
2827 }
2828 
2829 void G1CollectedHeap::print_all_rsets() {
2830   PrintRSetsClosure cl("Printing All RSets");;
2831   heap_region_iterate(&cl);
2832 }
2833 #endif // PRODUCT
2834 
2835 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2836   YoungList* young_list = heap()->young_list();
2837 
2838   size_t eden_used_bytes = young_list->eden_used_bytes();
2839   size_t survivor_used_bytes = young_list->survivor_used_bytes();
2840 
2841   size_t eden_capacity_bytes =
2842     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2843 
2844   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2845   return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes);
2846 }
2847 
2848 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2849   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2850                        stats->unused(), stats->used(), stats->region_end_waste(),
2851                        stats->regions_filled(), stats->direct_allocated(),
2852                        stats->failure_used(), stats->failure_waste());
2853 }
2854 
2855 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2856   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2857   gc_tracer->report_gc_heap_summary(when, heap_summary);
2858 
2859   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2860   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2861 }
2862 
2863 
2864 G1CollectedHeap* G1CollectedHeap::heap() {
2865   CollectedHeap* heap = Universe::heap();
2866   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2867   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2868   return (G1CollectedHeap*)heap;
2869 }
2870 
2871 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2872   // always_do_update_barrier = false;
2873   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2874   // Fill TLAB's and such
2875   accumulate_statistics_all_tlabs();
2876   ensure_parsability(true);
2877 
2878   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2879 }
2880 
2881 void G1CollectedHeap::gc_epilogue(bool full) {
2882   // we are at the end of the GC. Total collections has already been increased.
2883   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2884 
2885   // FIXME: what is this about?
2886   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2887   // is set.
2888 #if defined(COMPILER2) || INCLUDE_JVMCI
2889   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2890 #endif
2891   // always_do_update_barrier = true;
2892 
2893   resize_all_tlabs();
2894   allocation_context_stats().update(full);
2895 
2896   // We have just completed a GC. Update the soft reference
2897   // policy with the new heap occupancy
2898   Universe::update_heap_info_at_gc();
2899 }
2900 
2901 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2902                                                uint gc_count_before,
2903                                                bool* succeeded,
2904                                                GCCause::Cause gc_cause) {
2905   assert_heap_not_locked_and_not_at_safepoint();
2906   g1_policy()->record_stop_world_start();
2907   VM_G1IncCollectionPause op(gc_count_before,
2908                              word_size,
2909                              false, /* should_initiate_conc_mark */
2910                              g1_policy()->max_pause_time_ms(),
2911                              gc_cause);
2912 
2913   op.set_allocation_context(AllocationContext::current());
2914   VMThread::execute(&op);
2915 
2916   HeapWord* result = op.result();
2917   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2918   assert(result == NULL || ret_succeeded,
2919          "the result should be NULL if the VM did not succeed");
2920   *succeeded = ret_succeeded;
2921 
2922   assert_heap_not_locked();
2923   return result;
2924 }
2925 
2926 void
2927 G1CollectedHeap::doConcurrentMark() {
2928   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2929   if (!_cmThread->in_progress()) {
2930     _cmThread->set_started();
2931     CGC_lock->notify();
2932   }
2933 }
2934 
2935 size_t G1CollectedHeap::pending_card_num() {
2936   size_t extra_cards = 0;
2937   JavaThread *curr = Threads::first();
2938   while (curr != NULL) {
2939     DirtyCardQueue& dcq = curr->dirty_card_queue();
2940     extra_cards += dcq.size();
2941     curr = curr->next();
2942   }
2943   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2944   size_t buffer_size = dcqs.buffer_size();
2945   size_t buffer_num = dcqs.completed_buffers_num();
2946 
2947   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
2948   // in bytes - not the number of 'entries'. We need to convert
2949   // into a number of cards.
2950   return (buffer_size * buffer_num + extra_cards) / oopSize;
2951 }
2952 
2953 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2954  private:
2955   size_t _total_humongous;
2956   size_t _candidate_humongous;
2957 
2958   DirtyCardQueue _dcq;
2959 
2960   // We don't nominate objects with many remembered set entries, on
2961   // the assumption that such objects are likely still live.
2962   bool is_remset_small(HeapRegion* region) const {
2963     HeapRegionRemSet* const rset = region->rem_set();
2964     return G1EagerReclaimHumongousObjectsWithStaleRefs
2965       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2966       : rset->is_empty();
2967   }
2968 
2969   bool is_typeArray_region(HeapRegion* region) const {
2970     return oop(region->bottom())->is_typeArray();
2971   }
2972 
2973   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2974     assert(region->is_starts_humongous(), "Must start a humongous object");
2975 
2976     // Candidate selection must satisfy the following constraints
2977     // while concurrent marking is in progress:
2978     //
2979     // * In order to maintain SATB invariants, an object must not be
2980     // reclaimed if it was allocated before the start of marking and
2981     // has not had its references scanned.  Such an object must have
2982     // its references (including type metadata) scanned to ensure no
2983     // live objects are missed by the marking process.  Objects
2984     // allocated after the start of concurrent marking don't need to
2985     // be scanned.
2986     //
2987     // * An object must not be reclaimed if it is on the concurrent
2988     // mark stack.  Objects allocated after the start of concurrent
2989     // marking are never pushed on the mark stack.
2990     //
2991     // Nominating only objects allocated after the start of concurrent
2992     // marking is sufficient to meet both constraints.  This may miss
2993     // some objects that satisfy the constraints, but the marking data
2994     // structures don't support efficiently performing the needed
2995     // additional tests or scrubbing of the mark stack.
2996     //
2997     // However, we presently only nominate is_typeArray() objects.
2998     // A humongous object containing references induces remembered
2999     // set entries on other regions.  In order to reclaim such an
3000     // object, those remembered sets would need to be cleaned up.
3001     //
3002     // We also treat is_typeArray() objects specially, allowing them
3003     // to be reclaimed even if allocated before the start of
3004     // concurrent mark.  For this we rely on mark stack insertion to
3005     // exclude is_typeArray() objects, preventing reclaiming an object
3006     // that is in the mark stack.  We also rely on the metadata for
3007     // such objects to be built-in and so ensured to be kept live.
3008     // Frequent allocation and drop of large binary blobs is an
3009     // important use case for eager reclaim, and this special handling
3010     // may reduce needed headroom.
3011 
3012     return is_typeArray_region(region) && is_remset_small(region);
3013   }
3014 
3015  public:
3016   RegisterHumongousWithInCSetFastTestClosure()
3017   : _total_humongous(0),
3018     _candidate_humongous(0),
3019     _dcq(&JavaThread::dirty_card_queue_set()) {
3020   }
3021 
3022   virtual bool doHeapRegion(HeapRegion* r) {
3023     if (!r->is_starts_humongous()) {
3024       return false;
3025     }
3026     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3027 
3028     bool is_candidate = humongous_region_is_candidate(g1h, r);
3029     uint rindex = r->hrm_index();
3030     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3031     if (is_candidate) {
3032       _candidate_humongous++;
3033       g1h->register_humongous_region_with_cset(rindex);
3034       // Is_candidate already filters out humongous object with large remembered sets.
3035       // If we have a humongous object with a few remembered sets, we simply flush these
3036       // remembered set entries into the DCQS. That will result in automatic
3037       // re-evaluation of their remembered set entries during the following evacuation
3038       // phase.
3039       if (!r->rem_set()->is_empty()) {
3040         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3041                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3042         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3043         HeapRegionRemSetIterator hrrs(r->rem_set());
3044         size_t card_index;
3045         while (hrrs.has_next(card_index)) {
3046           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3047           // The remembered set might contain references to already freed
3048           // regions. Filter out such entries to avoid failing card table
3049           // verification.
3050           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
3051             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3052               *card_ptr = CardTableModRefBS::dirty_card_val();
3053               _dcq.enqueue(card_ptr);
3054             }
3055           }
3056         }
3057         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
3058                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
3059                hrrs.n_yielded(), r->rem_set()->occupied());
3060         r->rem_set()->clear_locked();
3061       }
3062       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3063     }
3064     _total_humongous++;
3065 
3066     return false;
3067   }
3068 
3069   size_t total_humongous() const { return _total_humongous; }
3070   size_t candidate_humongous() const { return _candidate_humongous; }
3071 
3072   void flush_rem_set_entries() { _dcq.flush(); }
3073 };
3074 
3075 void G1CollectedHeap::register_humongous_regions_with_cset() {
3076   if (!G1EagerReclaimHumongousObjects) {
3077     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3078     return;
3079   }
3080   double time = os::elapsed_counter();
3081 
3082   // Collect reclaim candidate information and register candidates with cset.
3083   RegisterHumongousWithInCSetFastTestClosure cl;
3084   heap_region_iterate(&cl);
3085 
3086   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3087   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3088                                                                   cl.total_humongous(),
3089                                                                   cl.candidate_humongous());
3090   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3091 
3092   // Finally flush all remembered set entries to re-check into the global DCQS.
3093   cl.flush_rem_set_entries();
3094 }
3095 
3096 class VerifyRegionRemSetClosure : public HeapRegionClosure {
3097   public:
3098     bool doHeapRegion(HeapRegion* hr) {
3099       if (!hr->is_archive() && !hr->is_continues_humongous()) {
3100         hr->verify_rem_set();
3101       }
3102       return false;
3103     }
3104 };
3105 
3106 #ifdef ASSERT
3107 class VerifyCSetClosure: public HeapRegionClosure {
3108 public:
3109   bool doHeapRegion(HeapRegion* hr) {
3110     // Here we check that the CSet region's RSet is ready for parallel
3111     // iteration. The fields that we'll verify are only manipulated
3112     // when the region is part of a CSet and is collected. Afterwards,
3113     // we reset these fields when we clear the region's RSet (when the
3114     // region is freed) so they are ready when the region is
3115     // re-allocated. The only exception to this is if there's an
3116     // evacuation failure and instead of freeing the region we leave
3117     // it in the heap. In that case, we reset these fields during
3118     // evacuation failure handling.
3119     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3120 
3121     // Here's a good place to add any other checks we'd like to
3122     // perform on CSet regions.
3123     return false;
3124   }
3125 };
3126 #endif // ASSERT
3127 
3128 uint G1CollectedHeap::num_task_queues() const {
3129   return _task_queues->size();
3130 }
3131 
3132 #if TASKQUEUE_STATS
3133 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3134   st->print_raw_cr("GC Task Stats");
3135   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3136   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3137 }
3138 
3139 void G1CollectedHeap::print_taskqueue_stats() const {
3140   if (!develop_log_is_enabled(Trace, gc, task, stats)) {
3141     return;
3142   }
3143   LogHandle(gc, task, stats) log;
3144   ResourceMark rm;
3145   outputStream* st = log.trace_stream();
3146 
3147   print_taskqueue_stats_hdr(st);
3148 
3149   TaskQueueStats totals;
3150   const uint n = num_task_queues();
3151   for (uint i = 0; i < n; ++i) {
3152     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3153     totals += task_queue(i)->stats;
3154   }
3155   st->print_raw("tot "); totals.print(st); st->cr();
3156 
3157   DEBUG_ONLY(totals.verify());
3158 }
3159 
3160 void G1CollectedHeap::reset_taskqueue_stats() {
3161   const uint n = num_task_queues();
3162   for (uint i = 0; i < n; ++i) {
3163     task_queue(i)->stats.reset();
3164   }
3165 }
3166 #endif // TASKQUEUE_STATS
3167 
3168 void G1CollectedHeap::log_gc_footer(jlong pause_time_counter) {
3169   if (evacuation_failed()) {
3170     log_info(gc)("To-space exhausted");
3171   }
3172 
3173   double pause_time_ms = TimeHelper::counter_to_millis(pause_time_counter);
3174   g1_policy()->print_phases(pause_time_ms);
3175 
3176   g1_policy()->print_detailed_heap_transition();
3177 }
3178 
3179 
3180 void G1CollectedHeap::wait_for_root_region_scanning() {
3181   double scan_wait_start = os::elapsedTime();
3182   // We have to wait until the CM threads finish scanning the
3183   // root regions as it's the only way to ensure that all the
3184   // objects on them have been correctly scanned before we start
3185   // moving them during the GC.
3186   bool waited = _cm->root_regions()->wait_until_scan_finished();
3187   double wait_time_ms = 0.0;
3188   if (waited) {
3189     double scan_wait_end = os::elapsedTime();
3190     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3191   }
3192   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3193 }
3194 
3195 bool
3196 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3197   assert_at_safepoint(true /* should_be_vm_thread */);
3198   guarantee(!is_gc_active(), "collection is not reentrant");
3199 
3200   if (GCLocker::check_active_before_gc()) {
3201     return false;
3202   }
3203 
3204   _gc_timer_stw->register_gc_start();
3205 
3206   GCIdMark gc_id_mark;
3207   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3208 
3209   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3210   ResourceMark rm;
3211 
3212   wait_for_root_region_scanning();
3213 
3214   print_heap_before_gc();
3215   trace_heap_before_gc(_gc_tracer_stw);
3216 
3217   _verifier->verify_region_sets_optional();
3218   _verifier->verify_dirty_young_regions();
3219 
3220   // This call will decide whether this pause is an initial-mark
3221   // pause. If it is, during_initial_mark_pause() will return true
3222   // for the duration of this pause.
3223   g1_policy()->decide_on_conc_mark_initiation();
3224 
3225   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3226   assert(!collector_state()->during_initial_mark_pause() ||
3227           collector_state()->gcs_are_young(), "sanity");
3228 
3229   // We also do not allow mixed GCs during marking.
3230   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3231 
3232   // Record whether this pause is an initial mark. When the current
3233   // thread has completed its logging output and it's safe to signal
3234   // the CM thread, the flag's value in the policy has been reset.
3235   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3236 
3237   // Inner scope for scope based logging, timers, and stats collection
3238   {
3239     EvacuationInfo evacuation_info;
3240 
3241     if (collector_state()->during_initial_mark_pause()) {
3242       // We are about to start a marking cycle, so we increment the
3243       // full collection counter.
3244       increment_old_marking_cycles_started();
3245       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3246     }
3247 
3248     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3249 
3250     GCTraceCPUTime tcpu;
3251 
3252     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3253                                                                   workers()->active_workers(),
3254                                                                   Threads::number_of_non_daemon_threads());
3255     workers()->set_active_workers(active_workers);
3256     FormatBuffer<> gc_string("Pause ");
3257     if (collector_state()->during_initial_mark_pause()) {
3258       gc_string.append("Initial Mark");
3259     } else if (collector_state()->gcs_are_young()) {
3260       gc_string.append("Young");
3261     } else {
3262       gc_string.append("Mixed");
3263     }
3264     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
3265 
3266     jlong pause_start_counter = os::elapsed_counter();
3267     g1_policy()->note_gc_start(active_workers);
3268 
3269     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3270     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3271 
3272     // If the secondary_free_list is not empty, append it to the
3273     // free_list. No need to wait for the cleanup operation to finish;
3274     // the region allocation code will check the secondary_free_list
3275     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3276     // set, skip this step so that the region allocation code has to
3277     // get entries from the secondary_free_list.
3278     if (!G1StressConcRegionFreeing) {
3279       append_secondary_free_list_if_not_empty_with_lock();
3280     }
3281 
3282     assert(check_young_list_well_formed(), "young list should be well formed");
3283 
3284     // Don't dynamically change the number of GC threads this early.  A value of
3285     // 0 is used to indicate serial work.  When parallel work is done,
3286     // it will be set.
3287 
3288     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3289       IsGCActiveMark x;
3290 
3291       gc_prologue(false);
3292       increment_total_collections(false /* full gc */);
3293       increment_gc_time_stamp();
3294 
3295       if (VerifyRememberedSets) {
3296         log_info(gc, verify)("[Verifying RemSets before GC]");
3297         VerifyRegionRemSetClosure v_cl;
3298         heap_region_iterate(&v_cl);
3299       }
3300 
3301       _verifier->verify_before_gc();
3302 
3303       _verifier->check_bitmaps("GC Start");
3304 
3305 #if defined(COMPILER2) || INCLUDE_JVMCI
3306       DerivedPointerTable::clear();
3307 #endif
3308 
3309       // Please see comment in g1CollectedHeap.hpp and
3310       // G1CollectedHeap::ref_processing_init() to see how
3311       // reference processing currently works in G1.
3312 
3313       // Enable discovery in the STW reference processor
3314       if (g1_policy()->should_process_references()) {
3315         ref_processor_stw()->enable_discovery();
3316       } else {
3317         ref_processor_stw()->disable_discovery();
3318       }
3319 
3320       {
3321         // We want to temporarily turn off discovery by the
3322         // CM ref processor, if necessary, and turn it back on
3323         // on again later if we do. Using a scoped
3324         // NoRefDiscovery object will do this.
3325         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3326 
3327         // Forget the current alloc region (we might even choose it to be part
3328         // of the collection set!).
3329         _allocator->release_mutator_alloc_region();
3330 
3331         // This timing is only used by the ergonomics to handle our pause target.
3332         // It is unclear why this should not include the full pause. We will
3333         // investigate this in CR 7178365.
3334         //
3335         // Preserving the old comment here if that helps the investigation:
3336         //
3337         // The elapsed time induced by the start time below deliberately elides
3338         // the possible verification above.
3339         double sample_start_time_sec = os::elapsedTime();
3340 
3341         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3342 
3343         if (collector_state()->during_initial_mark_pause()) {
3344           concurrent_mark()->checkpointRootsInitialPre();
3345         }
3346 
3347         double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms);
3348         g1_policy()->finalize_old_cset_part(time_remaining_ms);
3349 
3350         evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length());
3351 
3352         // Make sure the remembered sets are up to date. This needs to be
3353         // done before register_humongous_regions_with_cset(), because the
3354         // remembered sets are used there to choose eager reclaim candidates.
3355         // If the remembered sets are not up to date we might miss some
3356         // entries that need to be handled.
3357         g1_rem_set()->cleanupHRRS();
3358 
3359         register_humongous_regions_with_cset();
3360 
3361         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3362 
3363         _cm->note_start_of_gc();
3364         // We call this after finalize_cset() to
3365         // ensure that the CSet has been finalized.
3366         _cm->verify_no_cset_oops();
3367 
3368         if (_hr_printer.is_active()) {
3369           HeapRegion* hr = g1_policy()->collection_set();
3370           while (hr != NULL) {
3371             _hr_printer.cset(hr);
3372             hr = hr->next_in_collection_set();
3373           }
3374         }
3375 
3376 #ifdef ASSERT
3377         VerifyCSetClosure cl;
3378         collection_set_iterate(&cl);
3379 #endif // ASSERT
3380 
3381         // Initialize the GC alloc regions.
3382         _allocator->init_gc_alloc_regions(evacuation_info);
3383 
3384         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length());
3385         pre_evacuate_collection_set();
3386 
3387         // Actually do the work...
3388         evacuate_collection_set(evacuation_info, &per_thread_states);
3389 
3390         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3391 
3392         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3393         free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words);
3394 
3395         eagerly_reclaim_humongous_regions();
3396 
3397         g1_policy()->clear_collection_set();
3398 
3399         // Start a new incremental collection set for the next pause.
3400         g1_policy()->start_incremental_cset_building();
3401 
3402         clear_cset_fast_test();
3403 
3404         _young_list->reset_sampled_info();
3405 
3406         // Don't check the whole heap at this point as the
3407         // GC alloc regions from this pause have been tagged
3408         // as survivors and moved on to the survivor list.
3409         // Survivor regions will fail the !is_young() check.
3410         assert(check_young_list_empty(false /* check_heap */),
3411           "young list should be empty");
3412 
3413         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3414                                              _young_list->first_survivor_region(),
3415                                              _young_list->last_survivor_region());
3416 
3417         _young_list->reset_auxilary_lists();
3418 
3419         if (evacuation_failed()) {
3420           set_used(recalculate_used());
3421           if (_archive_allocator != NULL) {
3422             _archive_allocator->clear_used();
3423           }
3424           for (uint i = 0; i < ParallelGCThreads; i++) {
3425             if (_evacuation_failed_info_array[i].has_failed()) {
3426               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3427             }
3428           }
3429         } else {
3430           // The "used" of the the collection set have already been subtracted
3431           // when they were freed.  Add in the bytes evacuated.
3432           increase_used(g1_policy()->bytes_copied_during_gc());
3433         }
3434 
3435         if (collector_state()->during_initial_mark_pause()) {
3436           // We have to do this before we notify the CM threads that
3437           // they can start working to make sure that all the
3438           // appropriate initialization is done on the CM object.
3439           concurrent_mark()->checkpointRootsInitialPost();
3440           collector_state()->set_mark_in_progress(true);
3441           // Note that we don't actually trigger the CM thread at
3442           // this point. We do that later when we're sure that
3443           // the current thread has completed its logging output.
3444         }
3445 
3446         allocate_dummy_regions();
3447 
3448         _allocator->init_mutator_alloc_region();
3449 
3450         {
3451           size_t expand_bytes = g1_policy()->expansion_amount();
3452           if (expand_bytes > 0) {
3453             size_t bytes_before = capacity();
3454             // No need for an ergo logging here,
3455             // expansion_amount() does this when it returns a value > 0.
3456             double expand_ms;
3457             if (!expand(expand_bytes, &expand_ms)) {
3458               // We failed to expand the heap. Cannot do anything about it.
3459             }
3460             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3461           }
3462         }
3463 
3464         // We redo the verification but now wrt to the new CSet which
3465         // has just got initialized after the previous CSet was freed.
3466         _cm->verify_no_cset_oops();
3467         _cm->note_end_of_gc();
3468 
3469         // This timing is only used by the ergonomics to handle our pause target.
3470         // It is unclear why this should not include the full pause. We will
3471         // investigate this in CR 7178365.
3472         double sample_end_time_sec = os::elapsedTime();
3473         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3474         size_t total_cards_scanned = per_thread_states.total_cards_scanned();
3475         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned);
3476 
3477         evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before());
3478         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3479 
3480         MemoryService::track_memory_usage();
3481 
3482         // In prepare_for_verify() below we'll need to scan the deferred
3483         // update buffers to bring the RSets up-to-date if
3484         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3485         // the update buffers we'll probably need to scan cards on the
3486         // regions we just allocated to (i.e., the GC alloc
3487         // regions). However, during the last GC we called
3488         // set_saved_mark() on all the GC alloc regions, so card
3489         // scanning might skip the [saved_mark_word()...top()] area of
3490         // those regions (i.e., the area we allocated objects into
3491         // during the last GC). But it shouldn't. Given that
3492         // saved_mark_word() is conditional on whether the GC time stamp
3493         // on the region is current or not, by incrementing the GC time
3494         // stamp here we invalidate all the GC time stamps on all the
3495         // regions and saved_mark_word() will simply return top() for
3496         // all the regions. This is a nicer way of ensuring this rather
3497         // than iterating over the regions and fixing them. In fact, the
3498         // GC time stamp increment here also ensures that
3499         // saved_mark_word() will return top() between pauses, i.e.,
3500         // during concurrent refinement. So we don't need the
3501         // is_gc_active() check to decided which top to use when
3502         // scanning cards (see CR 7039627).
3503         increment_gc_time_stamp();
3504 
3505         if (VerifyRememberedSets) {
3506           log_info(gc, verify)("[Verifying RemSets after GC]");
3507           VerifyRegionRemSetClosure v_cl;
3508           heap_region_iterate(&v_cl);
3509         }
3510 
3511         _verifier->verify_after_gc();
3512         _verifier->check_bitmaps("GC End");
3513 
3514         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3515         ref_processor_stw()->verify_no_references_recorded();
3516 
3517         // CM reference discovery will be re-enabled if necessary.
3518       }
3519 
3520 #ifdef TRACESPINNING
3521       ParallelTaskTerminator::print_termination_counts();
3522 #endif
3523 
3524       gc_epilogue(false);
3525     }
3526 
3527     // Print the remainder of the GC log output.
3528     log_gc_footer(os::elapsed_counter() - pause_start_counter);
3529 
3530     // It is not yet to safe to tell the concurrent mark to
3531     // start as we have some optional output below. We don't want the
3532     // output from the concurrent mark thread interfering with this
3533     // logging output either.
3534 
3535     _hrm.verify_optional();
3536     _verifier->verify_region_sets_optional();
3537 
3538     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3539     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3540 
3541     print_heap_after_gc();
3542     trace_heap_after_gc(_gc_tracer_stw);
3543 
3544     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3545     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3546     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3547     // before any GC notifications are raised.
3548     g1mm()->update_sizes();
3549 
3550     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3551     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3552     _gc_timer_stw->register_gc_end();
3553     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3554   }
3555   // It should now be safe to tell the concurrent mark thread to start
3556   // without its logging output interfering with the logging output
3557   // that came from the pause.
3558 
3559   if (should_start_conc_mark) {
3560     // CAUTION: after the doConcurrentMark() call below,
3561     // the concurrent marking thread(s) could be running
3562     // concurrently with us. Make sure that anything after
3563     // this point does not assume that we are the only GC thread
3564     // running. Note: of course, the actual marking work will
3565     // not start until the safepoint itself is released in
3566     // SuspendibleThreadSet::desynchronize().
3567     doConcurrentMark();
3568   }
3569 
3570   return true;
3571 }
3572 
3573 void G1CollectedHeap::restore_preserved_marks() {
3574   G1RestorePreservedMarksTask rpm_task(_preserved_objs);
3575   workers()->run_task(&rpm_task);
3576 }
3577 
3578 void G1CollectedHeap::remove_self_forwarding_pointers() {
3579   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3580   workers()->run_task(&rsfp_task);
3581 }
3582 
3583 void G1CollectedHeap::restore_after_evac_failure() {
3584   double remove_self_forwards_start = os::elapsedTime();
3585 
3586   remove_self_forwarding_pointers();
3587   restore_preserved_marks();
3588 
3589   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3590 }
3591 
3592 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3593   if (!_evacuation_failed) {
3594     _evacuation_failed = true;
3595   }
3596 
3597   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3598 
3599   // We want to call the "for_promotion_failure" version only in the
3600   // case of a promotion failure.
3601   if (m->must_be_preserved_for_promotion_failure(obj)) {
3602     OopAndMarkOop elem(obj, m);
3603     _preserved_objs[worker_id].push(elem);
3604   }
3605 }
3606 
3607 bool G1ParEvacuateFollowersClosure::offer_termination() {
3608   G1ParScanThreadState* const pss = par_scan_state();
3609   start_term_time();
3610   const bool res = terminator()->offer_termination();
3611   end_term_time();
3612   return res;
3613 }
3614 
3615 void G1ParEvacuateFollowersClosure::do_void() {
3616   G1ParScanThreadState* const pss = par_scan_state();
3617   pss->trim_queue();
3618   do {
3619     pss->steal_and_trim_queue(queues());
3620   } while (!offer_termination());
3621 }
3622 
3623 class G1ParTask : public AbstractGangTask {
3624 protected:
3625   G1CollectedHeap*         _g1h;
3626   G1ParScanThreadStateSet* _pss;
3627   RefToScanQueueSet*       _queues;
3628   G1RootProcessor*         _root_processor;
3629   ParallelTaskTerminator   _terminator;
3630   uint                     _n_workers;
3631 
3632 public:
3633   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3634     : AbstractGangTask("G1 collection"),
3635       _g1h(g1h),
3636       _pss(per_thread_states),
3637       _queues(task_queues),
3638       _root_processor(root_processor),
3639       _terminator(n_workers, _queues),
3640       _n_workers(n_workers)
3641   {}
3642 
3643   void work(uint worker_id) {
3644     if (worker_id >= _n_workers) return;  // no work needed this round
3645 
3646     double start_sec = os::elapsedTime();
3647     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3648 
3649     {
3650       ResourceMark rm;
3651       HandleMark   hm;
3652 
3653       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3654 
3655       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3656       pss->set_ref_processor(rp);
3657 
3658       double start_strong_roots_sec = os::elapsedTime();
3659 
3660       _root_processor->evacuate_roots(pss->closures(), worker_id);
3661 
3662       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
3663 
3664       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3665       // treating the nmethods visited to act as roots for concurrent marking.
3666       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3667       // objects copied by the current evacuation.
3668       size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
3669                                                                              pss->closures()->weak_codeblobs(),
3670                                                                              worker_id);
3671 
3672       _pss->add_cards_scanned(worker_id, cards_scanned);
3673 
3674       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3675 
3676       double term_sec = 0.0;
3677       size_t evac_term_attempts = 0;
3678       {
3679         double start = os::elapsedTime();
3680         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3681         evac.do_void();
3682 
3683         evac_term_attempts = evac.term_attempts();
3684         term_sec = evac.term_time();
3685         double elapsed_sec = os::elapsedTime() - start;
3686         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3687         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3688         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3689       }
3690 
3691       assert(pss->queue_is_empty(), "should be empty");
3692 
3693       if (log_is_enabled(Debug, gc, task, stats)) {
3694         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3695         size_t lab_waste;
3696         size_t lab_undo_waste;
3697         pss->waste(lab_waste, lab_undo_waste);
3698         _g1h->print_termination_stats(worker_id,
3699                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3700                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3701                                       term_sec * 1000.0,                          /* evac term time */
3702                                       evac_term_attempts,                         /* evac term attempts */
3703                                       lab_waste,                                  /* alloc buffer waste */
3704                                       lab_undo_waste                              /* undo waste */
3705                                       );
3706       }
3707 
3708       // Close the inner scope so that the ResourceMark and HandleMark
3709       // destructors are executed here and are included as part of the
3710       // "GC Worker Time".
3711     }
3712     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3713   }
3714 };
3715 
3716 void G1CollectedHeap::print_termination_stats_hdr() {
3717   log_debug(gc, task, stats)("GC Termination Stats");
3718   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3719   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3720   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3721 }
3722 
3723 void G1CollectedHeap::print_termination_stats(uint worker_id,
3724                                               double elapsed_ms,
3725                                               double strong_roots_ms,
3726                                               double term_ms,
3727                                               size_t term_attempts,
3728                                               size_t alloc_buffer_waste,
3729                                               size_t undo_waste) const {
3730   log_debug(gc, task, stats)
3731               ("%3d %9.2f %9.2f %6.2f "
3732                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3733                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3734                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3735                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3736                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3737                alloc_buffer_waste * HeapWordSize / K,
3738                undo_waste * HeapWordSize / K);
3739 }
3740 
3741 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
3742 private:
3743   BoolObjectClosure* _is_alive;
3744   int _initial_string_table_size;
3745   int _initial_symbol_table_size;
3746 
3747   bool  _process_strings;
3748   int _strings_processed;
3749   int _strings_removed;
3750 
3751   bool  _process_symbols;
3752   int _symbols_processed;
3753   int _symbols_removed;
3754 
3755 public:
3756   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
3757     AbstractGangTask("String/Symbol Unlinking"),
3758     _is_alive(is_alive),
3759     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3760     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
3761 
3762     _initial_string_table_size = StringTable::the_table()->table_size();
3763     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3764     if (process_strings) {
3765       StringTable::clear_parallel_claimed_index();
3766     }
3767     if (process_symbols) {
3768       SymbolTable::clear_parallel_claimed_index();
3769     }
3770   }
3771 
3772   ~G1StringSymbolTableUnlinkTask() {
3773     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3774               "claim value %d after unlink less than initial string table size %d",
3775               StringTable::parallel_claimed_index(), _initial_string_table_size);
3776     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3777               "claim value %d after unlink less than initial symbol table size %d",
3778               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3779 
3780     log_debug(gc, stringdedup)("Cleaned string and symbol table, "
3781                                "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3782                                "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3783                                strings_processed(), strings_removed(),
3784                                symbols_processed(), symbols_removed());
3785   }
3786 
3787   void work(uint worker_id) {
3788     int strings_processed = 0;
3789     int strings_removed = 0;
3790     int symbols_processed = 0;
3791     int symbols_removed = 0;
3792     if (_process_strings) {
3793       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3794       Atomic::add(strings_processed, &_strings_processed);
3795       Atomic::add(strings_removed, &_strings_removed);
3796     }
3797     if (_process_symbols) {
3798       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3799       Atomic::add(symbols_processed, &_symbols_processed);
3800       Atomic::add(symbols_removed, &_symbols_removed);
3801     }
3802   }
3803 
3804   size_t strings_processed() const { return (size_t)_strings_processed; }
3805   size_t strings_removed()   const { return (size_t)_strings_removed; }
3806 
3807   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3808   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3809 };
3810 
3811 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3812 private:
3813   static Monitor* _lock;
3814 
3815   BoolObjectClosure* const _is_alive;
3816   const bool               _unloading_occurred;
3817   const uint               _num_workers;
3818 
3819   // Variables used to claim nmethods.
3820   nmethod* _first_nmethod;
3821   volatile nmethod* _claimed_nmethod;
3822 
3823   // The list of nmethods that need to be processed by the second pass.
3824   volatile nmethod* _postponed_list;
3825   volatile uint     _num_entered_barrier;
3826 
3827  public:
3828   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3829       _is_alive(is_alive),
3830       _unloading_occurred(unloading_occurred),
3831       _num_workers(num_workers),
3832       _first_nmethod(NULL),
3833       _claimed_nmethod(NULL),
3834       _postponed_list(NULL),
3835       _num_entered_barrier(0)
3836   {
3837     nmethod::increase_unloading_clock();
3838     // Get first alive nmethod
3839     NMethodIterator iter = NMethodIterator();
3840     if(iter.next_alive()) {
3841       _first_nmethod = iter.method();
3842     }
3843     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
3844   }
3845 
3846   ~G1CodeCacheUnloadingTask() {
3847     CodeCache::verify_clean_inline_caches();
3848 
3849     CodeCache::set_needs_cache_clean(false);
3850     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3851 
3852     CodeCache::verify_icholder_relocations();
3853   }
3854 
3855  private:
3856   void add_to_postponed_list(nmethod* nm) {
3857       nmethod* old;
3858       do {
3859         old = (nmethod*)_postponed_list;
3860         nm->set_unloading_next(old);
3861       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3862   }
3863 
3864   void clean_nmethod(nmethod* nm) {
3865     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3866 
3867     if (postponed) {
3868       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3869       add_to_postponed_list(nm);
3870     }
3871 
3872     // Mark that this thread has been cleaned/unloaded.
3873     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3874     nm->set_unloading_clock(nmethod::global_unloading_clock());
3875   }
3876 
3877   void clean_nmethod_postponed(nmethod* nm) {
3878     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3879   }
3880 
3881   static const int MaxClaimNmethods = 16;
3882 
3883   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
3884     nmethod* first;
3885     NMethodIterator last;
3886 
3887     do {
3888       *num_claimed_nmethods = 0;
3889 
3890       first = (nmethod*)_claimed_nmethod;
3891       last = NMethodIterator(first);
3892 
3893       if (first != NULL) {
3894 
3895         for (int i = 0; i < MaxClaimNmethods; i++) {
3896           if (!last.next_alive()) {
3897             break;
3898           }
3899           claimed_nmethods[i] = last.method();
3900           (*num_claimed_nmethods)++;
3901         }
3902       }
3903 
3904     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3905   }
3906 
3907   nmethod* claim_postponed_nmethod() {
3908     nmethod* claim;
3909     nmethod* next;
3910 
3911     do {
3912       claim = (nmethod*)_postponed_list;
3913       if (claim == NULL) {
3914         return NULL;
3915       }
3916 
3917       next = claim->unloading_next();
3918 
3919     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3920 
3921     return claim;
3922   }
3923 
3924  public:
3925   // Mark that we're done with the first pass of nmethod cleaning.
3926   void barrier_mark(uint worker_id) {
3927     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3928     _num_entered_barrier++;
3929     if (_num_entered_barrier == _num_workers) {
3930       ml.notify_all();
3931     }
3932   }
3933 
3934   // See if we have to wait for the other workers to
3935   // finish their first-pass nmethod cleaning work.
3936   void barrier_wait(uint worker_id) {
3937     if (_num_entered_barrier < _num_workers) {
3938       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3939       while (_num_entered_barrier < _num_workers) {
3940           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3941       }
3942     }
3943   }
3944 
3945   // Cleaning and unloading of nmethods. Some work has to be postponed
3946   // to the second pass, when we know which nmethods survive.
3947   void work_first_pass(uint worker_id) {
3948     // The first nmethods is claimed by the first worker.
3949     if (worker_id == 0 && _first_nmethod != NULL) {
3950       clean_nmethod(_first_nmethod);
3951       _first_nmethod = NULL;
3952     }
3953 
3954     int num_claimed_nmethods;
3955     nmethod* claimed_nmethods[MaxClaimNmethods];
3956 
3957     while (true) {
3958       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3959 
3960       if (num_claimed_nmethods == 0) {
3961         break;
3962       }
3963 
3964       for (int i = 0; i < num_claimed_nmethods; i++) {
3965         clean_nmethod(claimed_nmethods[i]);
3966       }
3967     }
3968   }
3969 
3970   void work_second_pass(uint worker_id) {
3971     nmethod* nm;
3972     // Take care of postponed nmethods.
3973     while ((nm = claim_postponed_nmethod()) != NULL) {
3974       clean_nmethod_postponed(nm);
3975     }
3976   }
3977 };
3978 
3979 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3980 
3981 class G1KlassCleaningTask : public StackObj {
3982   BoolObjectClosure*                      _is_alive;
3983   volatile jint                           _clean_klass_tree_claimed;
3984   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3985 
3986  public:
3987   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3988       _is_alive(is_alive),
3989       _clean_klass_tree_claimed(0),
3990       _klass_iterator() {
3991   }
3992 
3993  private:
3994   bool claim_clean_klass_tree_task() {
3995     if (_clean_klass_tree_claimed) {
3996       return false;
3997     }
3998 
3999     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4000   }
4001 
4002   InstanceKlass* claim_next_klass() {
4003     Klass* klass;
4004     do {
4005       klass =_klass_iterator.next_klass();
4006     } while (klass != NULL && !klass->is_instance_klass());
4007 
4008     // this can be null so don't call InstanceKlass::cast
4009     return static_cast<InstanceKlass*>(klass);
4010   }
4011 
4012 public:
4013 
4014   void clean_klass(InstanceKlass* ik) {
4015     ik->clean_weak_instanceklass_links(_is_alive);
4016   }
4017 
4018   void work() {
4019     ResourceMark rm;
4020 
4021     // One worker will clean the subklass/sibling klass tree.
4022     if (claim_clean_klass_tree_task()) {
4023       Klass::clean_subklass_tree(_is_alive);
4024     }
4025 
4026     // All workers will help cleaning the classes,
4027     InstanceKlass* klass;
4028     while ((klass = claim_next_klass()) != NULL) {
4029       clean_klass(klass);
4030     }
4031   }
4032 };
4033 
4034 // To minimize the remark pause times, the tasks below are done in parallel.
4035 class G1ParallelCleaningTask : public AbstractGangTask {
4036 private:
4037   G1StringSymbolTableUnlinkTask _string_symbol_task;
4038   G1CodeCacheUnloadingTask      _code_cache_task;
4039   G1KlassCleaningTask           _klass_cleaning_task;
4040 
4041 public:
4042   // The constructor is run in the VMThread.
4043   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4044       AbstractGangTask("Parallel Cleaning"),
4045       _string_symbol_task(is_alive, process_strings, process_symbols),
4046       _code_cache_task(num_workers, is_alive, unloading_occurred),
4047       _klass_cleaning_task(is_alive) {
4048   }
4049 
4050   // The parallel work done by all worker threads.
4051   void work(uint worker_id) {
4052     // Do first pass of code cache cleaning.
4053     _code_cache_task.work_first_pass(worker_id);
4054 
4055     // Let the threads mark that the first pass is done.
4056     _code_cache_task.barrier_mark(worker_id);
4057 
4058     // Clean the Strings and Symbols.
4059     _string_symbol_task.work(worker_id);
4060 
4061     // Wait for all workers to finish the first code cache cleaning pass.
4062     _code_cache_task.barrier_wait(worker_id);
4063 
4064     // Do the second code cache cleaning work, which realize on
4065     // the liveness information gathered during the first pass.
4066     _code_cache_task.work_second_pass(worker_id);
4067 
4068     // Clean all klasses that were not unloaded.
4069     _klass_cleaning_task.work();
4070   }
4071 };
4072 
4073 
4074 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
4075                                         bool process_strings,
4076                                         bool process_symbols,
4077                                         bool class_unloading_occurred) {
4078   uint n_workers = workers()->active_workers();
4079 
4080   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
4081                                         n_workers, class_unloading_occurred);
4082   workers()->run_task(&g1_unlink_task);
4083 }
4084 
4085 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
4086                                                      bool process_strings, bool process_symbols) {
4087   {
4088     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
4089     workers()->run_task(&g1_unlink_task);
4090   }
4091 
4092   if (G1StringDedup::is_enabled()) {
4093     G1StringDedup::unlink(is_alive);
4094   }
4095 }
4096 
4097 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
4098  private:
4099   DirtyCardQueueSet* _queue;
4100   G1CollectedHeap* _g1h;
4101  public:
4102   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
4103     _queue(queue), _g1h(g1h) { }
4104 
4105   virtual void work(uint worker_id) {
4106     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
4107     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
4108 
4109     RedirtyLoggedCardTableEntryClosure cl(_g1h);
4110     _queue->par_apply_closure_to_all_completed_buffers(&cl);
4111 
4112     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
4113   }
4114 };
4115 
4116 void G1CollectedHeap::redirty_logged_cards() {
4117   double redirty_logged_cards_start = os::elapsedTime();
4118 
4119   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
4120   dirty_card_queue_set().reset_for_par_iteration();
4121   workers()->run_task(&redirty_task);
4122 
4123   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4124   dcq.merge_bufferlists(&dirty_card_queue_set());
4125   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4126 
4127   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4128 }
4129 
4130 // Weak Reference Processing support
4131 
4132 // An always "is_alive" closure that is used to preserve referents.
4133 // If the object is non-null then it's alive.  Used in the preservation
4134 // of referent objects that are pointed to by reference objects
4135 // discovered by the CM ref processor.
4136 class G1AlwaysAliveClosure: public BoolObjectClosure {
4137   G1CollectedHeap* _g1;
4138 public:
4139   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4140   bool do_object_b(oop p) {
4141     if (p != NULL) {
4142       return true;
4143     }
4144     return false;
4145   }
4146 };
4147 
4148 bool G1STWIsAliveClosure::do_object_b(oop p) {
4149   // An object is reachable if it is outside the collection set,
4150   // or is inside and copied.
4151   return !_g1->is_in_cset(p) || p->is_forwarded();
4152 }
4153 
4154 // Non Copying Keep Alive closure
4155 class G1KeepAliveClosure: public OopClosure {
4156   G1CollectedHeap* _g1;
4157 public:
4158   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4159   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4160   void do_oop(oop* p) {
4161     oop obj = *p;
4162     assert(obj != NULL, "the caller should have filtered out NULL values");
4163 
4164     const InCSetState cset_state = _g1->in_cset_state(obj);
4165     if (!cset_state.is_in_cset_or_humongous()) {
4166       return;
4167     }
4168     if (cset_state.is_in_cset()) {
4169       assert( obj->is_forwarded(), "invariant" );
4170       *p = obj->forwardee();
4171     } else {
4172       assert(!obj->is_forwarded(), "invariant" );
4173       assert(cset_state.is_humongous(),
4174              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
4175       _g1->set_humongous_is_live(obj);
4176     }
4177   }
4178 };
4179 
4180 // Copying Keep Alive closure - can be called from both
4181 // serial and parallel code as long as different worker
4182 // threads utilize different G1ParScanThreadState instances
4183 // and different queues.
4184 
4185 class G1CopyingKeepAliveClosure: public OopClosure {
4186   G1CollectedHeap*         _g1h;
4187   OopClosure*              _copy_non_heap_obj_cl;
4188   G1ParScanThreadState*    _par_scan_state;
4189 
4190 public:
4191   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4192                             OopClosure* non_heap_obj_cl,
4193                             G1ParScanThreadState* pss):
4194     _g1h(g1h),
4195     _copy_non_heap_obj_cl(non_heap_obj_cl),
4196     _par_scan_state(pss)
4197   {}
4198 
4199   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4200   virtual void do_oop(      oop* p) { do_oop_work(p); }
4201 
4202   template <class T> void do_oop_work(T* p) {
4203     oop obj = oopDesc::load_decode_heap_oop(p);
4204 
4205     if (_g1h->is_in_cset_or_humongous(obj)) {
4206       // If the referent object has been forwarded (either copied
4207       // to a new location or to itself in the event of an
4208       // evacuation failure) then we need to update the reference
4209       // field and, if both reference and referent are in the G1
4210       // heap, update the RSet for the referent.
4211       //
4212       // If the referent has not been forwarded then we have to keep
4213       // it alive by policy. Therefore we have copy the referent.
4214       //
4215       // If the reference field is in the G1 heap then we can push
4216       // on the PSS queue. When the queue is drained (after each
4217       // phase of reference processing) the object and it's followers
4218       // will be copied, the reference field set to point to the
4219       // new location, and the RSet updated. Otherwise we need to
4220       // use the the non-heap or metadata closures directly to copy
4221       // the referent object and update the pointer, while avoiding
4222       // updating the RSet.
4223 
4224       if (_g1h->is_in_g1_reserved(p)) {
4225         _par_scan_state->push_on_queue(p);
4226       } else {
4227         assert(!Metaspace::contains((const void*)p),
4228                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
4229         _copy_non_heap_obj_cl->do_oop(p);
4230       }
4231     }
4232   }
4233 };
4234 
4235 // Serial drain queue closure. Called as the 'complete_gc'
4236 // closure for each discovered list in some of the
4237 // reference processing phases.
4238 
4239 class G1STWDrainQueueClosure: public VoidClosure {
4240 protected:
4241   G1CollectedHeap* _g1h;
4242   G1ParScanThreadState* _par_scan_state;
4243 
4244   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4245 
4246 public:
4247   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4248     _g1h(g1h),
4249     _par_scan_state(pss)
4250   { }
4251 
4252   void do_void() {
4253     G1ParScanThreadState* const pss = par_scan_state();
4254     pss->trim_queue();
4255   }
4256 };
4257 
4258 // Parallel Reference Processing closures
4259 
4260 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4261 // processing during G1 evacuation pauses.
4262 
4263 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4264 private:
4265   G1CollectedHeap*          _g1h;
4266   G1ParScanThreadStateSet*  _pss;
4267   RefToScanQueueSet*        _queues;
4268   WorkGang*                 _workers;
4269   uint                      _active_workers;
4270 
4271 public:
4272   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4273                            G1ParScanThreadStateSet* per_thread_states,
4274                            WorkGang* workers,
4275                            RefToScanQueueSet *task_queues,
4276                            uint n_workers) :
4277     _g1h(g1h),
4278     _pss(per_thread_states),
4279     _queues(task_queues),
4280     _workers(workers),
4281     _active_workers(n_workers)
4282   {
4283     assert(n_workers > 0, "shouldn't call this otherwise");
4284   }
4285 
4286   // Executes the given task using concurrent marking worker threads.
4287   virtual void execute(ProcessTask& task);
4288   virtual void execute(EnqueueTask& task);
4289 };
4290 
4291 // Gang task for possibly parallel reference processing
4292 
4293 class G1STWRefProcTaskProxy: public AbstractGangTask {
4294   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4295   ProcessTask&     _proc_task;
4296   G1CollectedHeap* _g1h;
4297   G1ParScanThreadStateSet* _pss;
4298   RefToScanQueueSet* _task_queues;
4299   ParallelTaskTerminator* _terminator;
4300 
4301 public:
4302   G1STWRefProcTaskProxy(ProcessTask& proc_task,
4303                         G1CollectedHeap* g1h,
4304                         G1ParScanThreadStateSet* per_thread_states,
4305                         RefToScanQueueSet *task_queues,
4306                         ParallelTaskTerminator* terminator) :
4307     AbstractGangTask("Process reference objects in parallel"),
4308     _proc_task(proc_task),
4309     _g1h(g1h),
4310     _pss(per_thread_states),
4311     _task_queues(task_queues),
4312     _terminator(terminator)
4313   {}
4314 
4315   virtual void work(uint worker_id) {
4316     // The reference processing task executed by a single worker.
4317     ResourceMark rm;
4318     HandleMark   hm;
4319 
4320     G1STWIsAliveClosure is_alive(_g1h);
4321 
4322     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4323     pss->set_ref_processor(NULL);
4324 
4325     // Keep alive closure.
4326     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4327 
4328     // Complete GC closure
4329     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4330 
4331     // Call the reference processing task's work routine.
4332     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4333 
4334     // Note we cannot assert that the refs array is empty here as not all
4335     // of the processing tasks (specifically phase2 - pp2_work) execute
4336     // the complete_gc closure (which ordinarily would drain the queue) so
4337     // the queue may not be empty.
4338   }
4339 };
4340 
4341 // Driver routine for parallel reference processing.
4342 // Creates an instance of the ref processing gang
4343 // task and has the worker threads execute it.
4344 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4345   assert(_workers != NULL, "Need parallel worker threads.");
4346 
4347   ParallelTaskTerminator terminator(_active_workers, _queues);
4348   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4349 
4350   _workers->run_task(&proc_task_proxy);
4351 }
4352 
4353 // Gang task for parallel reference enqueueing.
4354 
4355 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4356   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4357   EnqueueTask& _enq_task;
4358 
4359 public:
4360   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4361     AbstractGangTask("Enqueue reference objects in parallel"),
4362     _enq_task(enq_task)
4363   { }
4364 
4365   virtual void work(uint worker_id) {
4366     _enq_task.work(worker_id);
4367   }
4368 };
4369 
4370 // Driver routine for parallel reference enqueueing.
4371 // Creates an instance of the ref enqueueing gang
4372 // task and has the worker threads execute it.
4373 
4374 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4375   assert(_workers != NULL, "Need parallel worker threads.");
4376 
4377   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4378 
4379   _workers->run_task(&enq_task_proxy);
4380 }
4381 
4382 // End of weak reference support closures
4383 
4384 // Abstract task used to preserve (i.e. copy) any referent objects
4385 // that are in the collection set and are pointed to by reference
4386 // objects discovered by the CM ref processor.
4387 
4388 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4389 protected:
4390   G1CollectedHeap*         _g1h;
4391   G1ParScanThreadStateSet* _pss;
4392   RefToScanQueueSet*       _queues;
4393   ParallelTaskTerminator   _terminator;
4394   uint                     _n_workers;
4395 
4396 public:
4397   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4398     AbstractGangTask("ParPreserveCMReferents"),
4399     _g1h(g1h),
4400     _pss(per_thread_states),
4401     _queues(task_queues),
4402     _terminator(workers, _queues),
4403     _n_workers(workers)
4404   { }
4405 
4406   void work(uint worker_id) {
4407     ResourceMark rm;
4408     HandleMark   hm;
4409 
4410     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4411     pss->set_ref_processor(NULL);
4412     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4413 
4414     // Is alive closure
4415     G1AlwaysAliveClosure always_alive(_g1h);
4416 
4417     // Copying keep alive closure. Applied to referent objects that need
4418     // to be copied.
4419     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4420 
4421     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4422 
4423     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4424     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4425 
4426     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4427     // So this must be true - but assert just in case someone decides to
4428     // change the worker ids.
4429     assert(worker_id < limit, "sanity");
4430     assert(!rp->discovery_is_atomic(), "check this code");
4431 
4432     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4433     for (uint idx = worker_id; idx < limit; idx += stride) {
4434       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4435 
4436       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4437       while (iter.has_next()) {
4438         // Since discovery is not atomic for the CM ref processor, we
4439         // can see some null referent objects.
4440         iter.load_ptrs(DEBUG_ONLY(true));
4441         oop ref = iter.obj();
4442 
4443         // This will filter nulls.
4444         if (iter.is_referent_alive()) {
4445           iter.make_referent_alive();
4446         }
4447         iter.move_to_next();
4448       }
4449     }
4450 
4451     // Drain the queue - which may cause stealing
4452     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4453     drain_queue.do_void();
4454     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4455     assert(pss->queue_is_empty(), "should be");
4456   }
4457 };
4458 
4459 void G1CollectedHeap::process_weak_jni_handles() {
4460   double ref_proc_start = os::elapsedTime();
4461 
4462   G1STWIsAliveClosure is_alive(this);
4463   G1KeepAliveClosure keep_alive(this);
4464   JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4465 
4466   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4467   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4468 }
4469 
4470 // Weak Reference processing during an evacuation pause (part 1).
4471 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4472   double ref_proc_start = os::elapsedTime();
4473 
4474   ReferenceProcessor* rp = _ref_processor_stw;
4475   assert(rp->discovery_enabled(), "should have been enabled");
4476 
4477   // Any reference objects, in the collection set, that were 'discovered'
4478   // by the CM ref processor should have already been copied (either by
4479   // applying the external root copy closure to the discovered lists, or
4480   // by following an RSet entry).
4481   //
4482   // But some of the referents, that are in the collection set, that these
4483   // reference objects point to may not have been copied: the STW ref
4484   // processor would have seen that the reference object had already
4485   // been 'discovered' and would have skipped discovering the reference,
4486   // but would not have treated the reference object as a regular oop.
4487   // As a result the copy closure would not have been applied to the
4488   // referent object.
4489   //
4490   // We need to explicitly copy these referent objects - the references
4491   // will be processed at the end of remarking.
4492   //
4493   // We also need to do this copying before we process the reference
4494   // objects discovered by the STW ref processor in case one of these
4495   // referents points to another object which is also referenced by an
4496   // object discovered by the STW ref processor.
4497 
4498   uint no_of_gc_workers = workers()->active_workers();
4499 
4500   G1ParPreserveCMReferentsTask keep_cm_referents(this,
4501                                                  per_thread_states,
4502                                                  no_of_gc_workers,
4503                                                  _task_queues);
4504 
4505   workers()->run_task(&keep_cm_referents);
4506 
4507   // Closure to test whether a referent is alive.
4508   G1STWIsAliveClosure is_alive(this);
4509 
4510   // Even when parallel reference processing is enabled, the processing
4511   // of JNI refs is serial and performed serially by the current thread
4512   // rather than by a worker. The following PSS will be used for processing
4513   // JNI refs.
4514 
4515   // Use only a single queue for this PSS.
4516   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4517   pss->set_ref_processor(NULL);
4518   assert(pss->queue_is_empty(), "pre-condition");
4519 
4520   // Keep alive closure.
4521   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4522 
4523   // Serial Complete GC closure
4524   G1STWDrainQueueClosure drain_queue(this, pss);
4525 
4526   // Setup the soft refs policy...
4527   rp->setup_policy(false);
4528 
4529   ReferenceProcessorStats stats;
4530   if (!rp->processing_is_mt()) {
4531     // Serial reference processing...
4532     stats = rp->process_discovered_references(&is_alive,
4533                                               &keep_alive,
4534                                               &drain_queue,
4535                                               NULL,
4536                                               _gc_timer_stw);
4537   } else {
4538     // Parallel reference processing
4539     assert(rp->num_q() == no_of_gc_workers, "sanity");
4540     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
4541 
4542     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4543     stats = rp->process_discovered_references(&is_alive,
4544                                               &keep_alive,
4545                                               &drain_queue,
4546                                               &par_task_executor,
4547                                               _gc_timer_stw);
4548   }
4549 
4550   _gc_tracer_stw->report_gc_reference_stats(stats);
4551 
4552   // We have completed copying any necessary live referent objects.
4553   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4554 
4555   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4556   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4557 }
4558 
4559 // Weak Reference processing during an evacuation pause (part 2).
4560 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4561   double ref_enq_start = os::elapsedTime();
4562 
4563   ReferenceProcessor* rp = _ref_processor_stw;
4564   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4565 
4566   // Now enqueue any remaining on the discovered lists on to
4567   // the pending list.
4568   if (!rp->processing_is_mt()) {
4569     // Serial reference processing...
4570     rp->enqueue_discovered_references();
4571   } else {
4572     // Parallel reference enqueueing
4573 
4574     uint n_workers = workers()->active_workers();
4575 
4576     assert(rp->num_q() == n_workers, "sanity");
4577     assert(n_workers <= rp->max_num_q(), "sanity");
4578 
4579     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4580     rp->enqueue_discovered_references(&par_task_executor);
4581   }
4582 
4583   rp->verify_no_references_recorded();
4584   assert(!rp->discovery_enabled(), "should have been disabled");
4585 
4586   // FIXME
4587   // CM's reference processing also cleans up the string and symbol tables.
4588   // Should we do that here also? We could, but it is a serial operation
4589   // and could significantly increase the pause time.
4590 
4591   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4592   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4593 }
4594 
4595 void G1CollectedHeap::pre_evacuate_collection_set() {
4596   _expand_heap_after_alloc_failure = true;
4597   _evacuation_failed = false;
4598 
4599   // Disable the hot card cache.
4600   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
4601   hot_card_cache->reset_hot_cache_claimed_index();
4602   hot_card_cache->set_use_cache(false);
4603 
4604   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4605 }
4606 
4607 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4608   // Should G1EvacuationFailureALot be in effect for this GC?
4609   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4610 
4611   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4612   double start_par_time_sec = os::elapsedTime();
4613   double end_par_time_sec;
4614 
4615   {
4616     const uint n_workers = workers()->active_workers();
4617     G1RootProcessor root_processor(this, n_workers);
4618     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4619     // InitialMark needs claim bits to keep track of the marked-through CLDs.
4620     if (collector_state()->during_initial_mark_pause()) {
4621       ClassLoaderDataGraph::clear_claimed_marks();
4622     }
4623 
4624     print_termination_stats_hdr();
4625 
4626     workers()->run_task(&g1_par_task);
4627     end_par_time_sec = os::elapsedTime();
4628 
4629     // Closing the inner scope will execute the destructor
4630     // for the G1RootProcessor object. We record the current
4631     // elapsed time before closing the scope so that time
4632     // taken for the destructor is NOT included in the
4633     // reported parallel time.
4634   }
4635 
4636   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4637 
4638   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4639   phase_times->record_par_time(par_time_ms);
4640 
4641   double code_root_fixup_time_ms =
4642         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4643   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4644 }
4645 
4646 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4647   // Process any discovered reference objects - we have
4648   // to do this _before_ we retire the GC alloc regions
4649   // as we may have to copy some 'reachable' referent
4650   // objects (and their reachable sub-graphs) that were
4651   // not copied during the pause.
4652   if (g1_policy()->should_process_references()) {
4653     process_discovered_references(per_thread_states);
4654   } else {
4655     ref_processor_stw()->verify_no_references_recorded();
4656     process_weak_jni_handles();
4657   }
4658 
4659   if (G1StringDedup::is_enabled()) {
4660     double fixup_start = os::elapsedTime();
4661 
4662     G1STWIsAliveClosure is_alive(this);
4663     G1KeepAliveClosure keep_alive(this);
4664     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4665 
4666     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4667     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4668   }
4669 
4670   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4671 
4672   if (evacuation_failed()) {
4673     restore_after_evac_failure();
4674 
4675     // Reset the G1EvacuationFailureALot counters and flags
4676     // Note: the values are reset only when an actual
4677     // evacuation failure occurs.
4678     NOT_PRODUCT(reset_evacuation_should_fail();)
4679   }
4680 
4681   // Enqueue any remaining references remaining on the STW
4682   // reference processor's discovered lists. We need to do
4683   // this after the card table is cleaned (and verified) as
4684   // the act of enqueueing entries on to the pending list
4685   // will log these updates (and dirty their associated
4686   // cards). We need these updates logged to update any
4687   // RSets.
4688   if (g1_policy()->should_process_references()) {
4689     enqueue_discovered_references(per_thread_states);
4690   } else {
4691     g1_policy()->phase_times()->record_ref_enq_time(0);
4692   }
4693 
4694   _allocator->release_gc_alloc_regions(evacuation_info);
4695 
4696   per_thread_states->flush();
4697 
4698   record_obj_copy_mem_stats();
4699 
4700   _survivor_evac_stats.adjust_desired_plab_sz();
4701   _old_evac_stats.adjust_desired_plab_sz();
4702 
4703   // Reset and re-enable the hot card cache.
4704   // Note the counts for the cards in the regions in the
4705   // collection set are reset when the collection set is freed.
4706   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
4707   hot_card_cache->reset_hot_cache();
4708   hot_card_cache->set_use_cache(true);
4709 
4710   purge_code_root_memory();
4711 
4712   redirty_logged_cards();
4713 #if defined(COMPILER2) || INCLUDE_JVMCI
4714   DerivedPointerTable::update_pointers();
4715 #endif
4716 }
4717 
4718 void G1CollectedHeap::record_obj_copy_mem_stats() {
4719   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4720 
4721   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4722                                                create_g1_evac_summary(&_old_evac_stats));
4723 }
4724 
4725 void G1CollectedHeap::free_region(HeapRegion* hr,
4726                                   FreeRegionList* free_list,
4727                                   bool par,
4728                                   bool locked) {
4729   assert(!hr->is_free(), "the region should not be free");
4730   assert(!hr->is_empty(), "the region should not be empty");
4731   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4732   assert(free_list != NULL, "pre-condition");
4733 
4734   if (G1VerifyBitmaps) {
4735     MemRegion mr(hr->bottom(), hr->end());
4736     concurrent_mark()->clearRangePrevBitmap(mr);
4737   }
4738 
4739   // Clear the card counts for this region.
4740   // Note: we only need to do this if the region is not young
4741   // (since we don't refine cards in young regions).
4742   if (!hr->is_young()) {
4743     _cg1r->hot_card_cache()->reset_card_counts(hr);
4744   }
4745   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
4746   free_list->add_ordered(hr);
4747 }
4748 
4749 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4750                                             FreeRegionList* free_list,
4751                                             bool par) {
4752   assert(hr->is_humongous(), "this is only for humongous regions");
4753   assert(free_list != NULL, "pre-condition");
4754   hr->clear_humongous();
4755   free_region(hr, free_list, par);
4756 }
4757 
4758 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4759                                            const uint humongous_regions_removed) {
4760   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4761     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4762     _old_set.bulk_remove(old_regions_removed);
4763     _humongous_set.bulk_remove(humongous_regions_removed);
4764   }
4765 
4766 }
4767 
4768 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4769   assert(list != NULL, "list can't be null");
4770   if (!list->is_empty()) {
4771     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4772     _hrm.insert_list_into_free_list(list);
4773   }
4774 }
4775 
4776 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4777   decrease_used(bytes);
4778 }
4779 
4780 class G1ParCleanupCTTask : public AbstractGangTask {
4781   G1SATBCardTableModRefBS* _ct_bs;
4782   G1CollectedHeap* _g1h;
4783   HeapRegion* volatile _su_head;
4784 public:
4785   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
4786                      G1CollectedHeap* g1h) :
4787     AbstractGangTask("G1 Par Cleanup CT Task"),
4788     _ct_bs(ct_bs), _g1h(g1h) { }
4789 
4790   void work(uint worker_id) {
4791     HeapRegion* r;
4792     while (r = _g1h->pop_dirty_cards_region()) {
4793       clear_cards(r);
4794     }
4795   }
4796 
4797   void clear_cards(HeapRegion* r) {
4798     // Cards of the survivors should have already been dirtied.
4799     if (!r->is_survivor()) {
4800       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
4801     }
4802   }
4803 };
4804 
4805 class G1ParScrubRemSetTask: public AbstractGangTask {
4806 protected:
4807   G1RemSet* _g1rs;
4808   BitMap* _region_bm;
4809   BitMap* _card_bm;
4810   HeapRegionClaimer _hrclaimer;
4811 
4812 public:
4813   G1ParScrubRemSetTask(G1RemSet* g1_rs, BitMap* region_bm, BitMap* card_bm, uint num_workers) :
4814     AbstractGangTask("G1 ScrubRS"),
4815     _g1rs(g1_rs),
4816     _region_bm(region_bm),
4817     _card_bm(card_bm),
4818     _hrclaimer(num_workers) {
4819   }
4820 
4821   void work(uint worker_id) {
4822     _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer);
4823   }
4824 };
4825 
4826 void G1CollectedHeap::scrub_rem_set(BitMap* region_bm, BitMap* card_bm) {
4827   uint num_workers = workers()->active_workers();
4828   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), region_bm, card_bm, num_workers);
4829   workers()->run_task(&g1_par_scrub_rs_task);
4830 }
4831 
4832 void G1CollectedHeap::cleanUpCardTable() {
4833   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
4834   double start = os::elapsedTime();
4835 
4836   {
4837     // Iterate over the dirty cards region list.
4838     G1ParCleanupCTTask cleanup_task(ct_bs, this);
4839 
4840     workers()->run_task(&cleanup_task);
4841 #ifndef PRODUCT
4842     _verifier->verify_card_table_cleanup();
4843 #endif
4844   }
4845 
4846   double elapsed = os::elapsedTime() - start;
4847   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
4848 }
4849 
4850 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4851   size_t pre_used = 0;
4852   FreeRegionList local_free_list("Local List for CSet Freeing");
4853 
4854   double young_time_ms     = 0.0;
4855   double non_young_time_ms = 0.0;
4856 
4857   // Since the collection set is a superset of the the young list,
4858   // all we need to do to clear the young list is clear its
4859   // head and length, and unlink any young regions in the code below
4860   _young_list->clear();
4861 
4862   G1CollectorPolicy* policy = g1_policy();
4863 
4864   double start_sec = os::elapsedTime();
4865   bool non_young = true;
4866 
4867   HeapRegion* cur = cs_head;
4868   int age_bound = -1;
4869   size_t rs_lengths = 0;
4870 
4871   while (cur != NULL) {
4872     assert(!is_on_master_free_list(cur), "sanity");
4873     if (non_young) {
4874       if (cur->is_young()) {
4875         double end_sec = os::elapsedTime();
4876         double elapsed_ms = (end_sec - start_sec) * 1000.0;
4877         non_young_time_ms += elapsed_ms;
4878 
4879         start_sec = os::elapsedTime();
4880         non_young = false;
4881       }
4882     } else {
4883       if (!cur->is_young()) {
4884         double end_sec = os::elapsedTime();
4885         double elapsed_ms = (end_sec - start_sec) * 1000.0;
4886         young_time_ms += elapsed_ms;
4887 
4888         start_sec = os::elapsedTime();
4889         non_young = true;
4890       }
4891     }
4892 
4893     rs_lengths += cur->rem_set()->occupied_locked();
4894 
4895     HeapRegion* next = cur->next_in_collection_set();
4896     assert(cur->in_collection_set(), "bad CS");
4897     cur->set_next_in_collection_set(NULL);
4898     clear_in_cset(cur);
4899 
4900     if (cur->is_young()) {
4901       int index = cur->young_index_in_cset();
4902       assert(index != -1, "invariant");
4903       assert((uint) index < policy->young_cset_region_length(), "invariant");
4904       size_t words_survived = surviving_young_words[index];
4905       cur->record_surv_words_in_group(words_survived);
4906 
4907       // At this point the we have 'popped' cur from the collection set
4908       // (linked via next_in_collection_set()) but it is still in the
4909       // young list (linked via next_young_region()). Clear the
4910       // _next_young_region field.
4911       cur->set_next_young_region(NULL);
4912     } else {
4913       int index = cur->young_index_in_cset();
4914       assert(index == -1, "invariant");
4915     }
4916 
4917     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
4918             (!cur->is_young() && cur->young_index_in_cset() == -1),
4919             "invariant" );
4920 
4921     if (!cur->evacuation_failed()) {
4922       MemRegion used_mr = cur->used_region();
4923 
4924       // And the region is empty.
4925       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
4926       pre_used += cur->used();
4927       free_region(cur, &local_free_list, false /* par */, true /* locked */);
4928     } else {
4929       cur->uninstall_surv_rate_group();
4930       if (cur->is_young()) {
4931         cur->set_young_index_in_cset(-1);
4932       }
4933       cur->set_evacuation_failed(false);
4934       // When moving a young gen region to old gen, we "allocate" that whole region
4935       // there. This is in addition to any already evacuated objects. Notify the
4936       // policy about that.
4937       // Old gen regions do not cause an additional allocation: both the objects
4938       // still in the region and the ones already moved are accounted for elsewhere.
4939       if (cur->is_young()) {
4940         policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes);
4941       }
4942       // The region is now considered to be old.
4943       cur->set_old();
4944       // Do some allocation statistics accounting. Regions that failed evacuation
4945       // are always made old, so there is no need to update anything in the young
4946       // gen statistics, but we need to update old gen statistics.
4947       size_t used_words = cur->marked_bytes() / HeapWordSize;
4948       _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words);
4949       _old_set.add(cur);
4950       evacuation_info.increment_collectionset_used_after(cur->used());
4951     }
4952     cur = next;
4953   }
4954 
4955   evacuation_info.set_regions_freed(local_free_list.length());
4956   policy->record_max_rs_lengths(rs_lengths);
4957   policy->cset_regions_freed();
4958 
4959   double end_sec = os::elapsedTime();
4960   double elapsed_ms = (end_sec - start_sec) * 1000.0;
4961 
4962   if (non_young) {
4963     non_young_time_ms += elapsed_ms;
4964   } else {
4965     young_time_ms += elapsed_ms;
4966   }
4967 
4968   prepend_to_freelist(&local_free_list);
4969   decrement_summary_bytes(pre_used);
4970   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
4971   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
4972 }
4973 
4974 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4975  private:
4976   FreeRegionList* _free_region_list;
4977   HeapRegionSet* _proxy_set;
4978   uint _humongous_regions_removed;
4979   size_t _freed_bytes;
4980  public:
4981 
4982   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4983     _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) {
4984   }
4985 
4986   virtual bool doHeapRegion(HeapRegion* r) {
4987     if (!r->is_starts_humongous()) {
4988       return false;
4989     }
4990 
4991     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4992 
4993     oop obj = (oop)r->bottom();
4994     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4995 
4996     // The following checks whether the humongous object is live are sufficient.
4997     // The main additional check (in addition to having a reference from the roots
4998     // or the young gen) is whether the humongous object has a remembered set entry.
4999     //
5000     // A humongous object cannot be live if there is no remembered set for it
5001     // because:
5002     // - there can be no references from within humongous starts regions referencing
5003     // the object because we never allocate other objects into them.
5004     // (I.e. there are no intra-region references that may be missed by the
5005     // remembered set)
5006     // - as soon there is a remembered set entry to the humongous starts region
5007     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
5008     // until the end of a concurrent mark.
5009     //
5010     // It is not required to check whether the object has been found dead by marking
5011     // or not, in fact it would prevent reclamation within a concurrent cycle, as
5012     // all objects allocated during that time are considered live.
5013     // SATB marking is even more conservative than the remembered set.
5014     // So if at this point in the collection there is no remembered set entry,
5015     // nobody has a reference to it.
5016     // At the start of collection we flush all refinement logs, and remembered sets
5017     // are completely up-to-date wrt to references to the humongous object.
5018     //
5019     // Other implementation considerations:
5020     // - never consider object arrays at this time because they would pose
5021     // considerable effort for cleaning up the the remembered sets. This is
5022     // required because stale remembered sets might reference locations that
5023     // are currently allocated into.
5024     uint region_idx = r->hrm_index();
5025     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
5026         !r->rem_set()->is_empty()) {
5027       log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT "  with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
5028                                region_idx,
5029                                (size_t)obj->size() * HeapWordSize,
5030                                p2i(r->bottom()),
5031                                r->rem_set()->occupied(),
5032                                r->rem_set()->strong_code_roots_list_length(),
5033                                next_bitmap->isMarked(r->bottom()),
5034                                g1h->is_humongous_reclaim_candidate(region_idx),
5035                                obj->is_typeArray()
5036                               );
5037       return false;
5038     }
5039 
5040     guarantee(obj->is_typeArray(),
5041               "Only eagerly reclaiming type arrays is supported, but the object "
5042               PTR_FORMAT " is not.", p2i(r->bottom()));
5043 
5044     log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
5045                              region_idx,
5046                              (size_t)obj->size() * HeapWordSize,
5047                              p2i(r->bottom()),
5048                              r->rem_set()->occupied(),
5049                              r->rem_set()->strong_code_roots_list_length(),
5050                              next_bitmap->isMarked(r->bottom()),
5051                              g1h->is_humongous_reclaim_candidate(region_idx),
5052                              obj->is_typeArray()
5053                             );
5054 
5055     // Need to clear mark bit of the humongous object if already set.
5056     if (next_bitmap->isMarked(r->bottom())) {
5057       next_bitmap->clear(r->bottom());
5058     }
5059     do {
5060       HeapRegion* next = g1h->next_region_in_humongous(r);
5061       _freed_bytes += r->used();
5062       r->set_containing_set(NULL);
5063       _humongous_regions_removed++;
5064       g1h->free_humongous_region(r, _free_region_list, false);
5065       r = next;
5066     } while (r != NULL);
5067 
5068     return false;
5069   }
5070 
5071   uint humongous_free_count() {
5072     return _humongous_regions_removed;
5073   }
5074 
5075   size_t bytes_freed() const {
5076     return _freed_bytes;
5077   }
5078 };
5079 
5080 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
5081   assert_at_safepoint(true);
5082 
5083   if (!G1EagerReclaimHumongousObjects ||
5084       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
5085     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
5086     return;
5087   }
5088 
5089   double start_time = os::elapsedTime();
5090 
5091   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
5092 
5093   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
5094   heap_region_iterate(&cl);
5095 
5096   remove_from_old_sets(0, cl.humongous_free_count());
5097 
5098   G1HRPrinter* hrp = hr_printer();
5099   if (hrp->is_active()) {
5100     FreeRegionListIterator iter(&local_cleanup_list);
5101     while (iter.more_available()) {
5102       HeapRegion* hr = iter.get_next();
5103       hrp->cleanup(hr);
5104     }
5105   }
5106 
5107   prepend_to_freelist(&local_cleanup_list);
5108   decrement_summary_bytes(cl.bytes_freed());
5109 
5110   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
5111                                                                     cl.humongous_free_count());
5112 }
5113 
5114 // This routine is similar to the above but does not record
5115 // any policy statistics or update free lists; we are abandoning
5116 // the current incremental collection set in preparation of a
5117 // full collection. After the full GC we will start to build up
5118 // the incremental collection set again.
5119 // This is only called when we're doing a full collection
5120 // and is immediately followed by the tearing down of the young list.
5121 
5122 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5123   HeapRegion* cur = cs_head;
5124 
5125   while (cur != NULL) {
5126     HeapRegion* next = cur->next_in_collection_set();
5127     assert(cur->in_collection_set(), "bad CS");
5128     cur->set_next_in_collection_set(NULL);
5129     clear_in_cset(cur);
5130     cur->set_young_index_in_cset(-1);
5131     cur = next;
5132   }
5133 }
5134 
5135 void G1CollectedHeap::set_free_regions_coming() {
5136   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
5137 
5138   assert(!free_regions_coming(), "pre-condition");
5139   _free_regions_coming = true;
5140 }
5141 
5142 void G1CollectedHeap::reset_free_regions_coming() {
5143   assert(free_regions_coming(), "pre-condition");
5144 
5145   {
5146     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5147     _free_regions_coming = false;
5148     SecondaryFreeList_lock->notify_all();
5149   }
5150 
5151   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5152 }
5153 
5154 void G1CollectedHeap::wait_while_free_regions_coming() {
5155   // Most of the time we won't have to wait, so let's do a quick test
5156   // first before we take the lock.
5157   if (!free_regions_coming()) {
5158     return;
5159   }
5160 
5161   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5162 
5163   {
5164     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5165     while (free_regions_coming()) {
5166       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5167     }
5168   }
5169 
5170   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5171 }
5172 
5173 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5174   return _allocator->is_retained_old_region(hr);
5175 }
5176 
5177 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5178   _young_list->push_region(hr);
5179 }
5180 
5181 class NoYoungRegionsClosure: public HeapRegionClosure {
5182 private:
5183   bool _success;
5184 public:
5185   NoYoungRegionsClosure() : _success(true) { }
5186   bool doHeapRegion(HeapRegion* r) {
5187     if (r->is_young()) {
5188       log_info(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5189                            p2i(r->bottom()), p2i(r->end()));
5190       _success = false;
5191     }
5192     return false;
5193   }
5194   bool success() { return _success; }
5195 };
5196 
5197 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5198   bool ret = _young_list->check_list_empty(check_sample);
5199 
5200   if (check_heap) {
5201     NoYoungRegionsClosure closure;
5202     heap_region_iterate(&closure);
5203     ret = ret && closure.success();
5204   }
5205 
5206   return ret;
5207 }
5208 
5209 class TearDownRegionSetsClosure : public HeapRegionClosure {
5210 private:
5211   HeapRegionSet *_old_set;
5212 
5213 public:
5214   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5215 
5216   bool doHeapRegion(HeapRegion* r) {
5217     if (r->is_old()) {
5218       _old_set->remove(r);
5219     } else {
5220       // We ignore free regions, we'll empty the free list afterwards.
5221       // We ignore young regions, we'll empty the young list afterwards.
5222       // We ignore humongous regions, we're not tearing down the
5223       // humongous regions set.
5224       assert(r->is_free() || r->is_young() || r->is_humongous(),
5225              "it cannot be another type");
5226     }
5227     return false;
5228   }
5229 
5230   ~TearDownRegionSetsClosure() {
5231     assert(_old_set->is_empty(), "post-condition");
5232   }
5233 };
5234 
5235 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5236   assert_at_safepoint(true /* should_be_vm_thread */);
5237 
5238   if (!free_list_only) {
5239     TearDownRegionSetsClosure cl(&_old_set);
5240     heap_region_iterate(&cl);
5241 
5242     // Note that emptying the _young_list is postponed and instead done as
5243     // the first step when rebuilding the regions sets again. The reason for
5244     // this is that during a full GC string deduplication needs to know if
5245     // a collected region was young or old when the full GC was initiated.
5246   }
5247   _hrm.remove_all_free_regions();
5248 }
5249 
5250 void G1CollectedHeap::increase_used(size_t bytes) {
5251   _summary_bytes_used += bytes;
5252 }
5253 
5254 void G1CollectedHeap::decrease_used(size_t bytes) {
5255   assert(_summary_bytes_used >= bytes,
5256          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5257          _summary_bytes_used, bytes);
5258   _summary_bytes_used -= bytes;
5259 }
5260 
5261 void G1CollectedHeap::set_used(size_t bytes) {
5262   _summary_bytes_used = bytes;
5263 }
5264 
5265 class RebuildRegionSetsClosure : public HeapRegionClosure {
5266 private:
5267   bool            _free_list_only;
5268   HeapRegionSet*   _old_set;
5269   HeapRegionManager*   _hrm;
5270   size_t          _total_used;
5271 
5272 public:
5273   RebuildRegionSetsClosure(bool free_list_only,
5274                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5275     _free_list_only(free_list_only),
5276     _old_set(old_set), _hrm(hrm), _total_used(0) {
5277     assert(_hrm->num_free_regions() == 0, "pre-condition");
5278     if (!free_list_only) {
5279       assert(_old_set->is_empty(), "pre-condition");
5280     }
5281   }
5282 
5283   bool doHeapRegion(HeapRegion* r) {
5284     if (r->is_empty()) {
5285       // Add free regions to the free list
5286       r->set_free();
5287       r->set_allocation_context(AllocationContext::system());
5288       _hrm->insert_into_free_list(r);
5289     } else if (!_free_list_only) {
5290       assert(!r->is_young(), "we should not come across young regions");
5291 
5292       if (r->is_humongous()) {
5293         // We ignore humongous regions. We left the humongous set unchanged.
5294       } else {
5295         // Objects that were compacted would have ended up on regions
5296         // that were previously old or free.  Archive regions (which are
5297         // old) will not have been touched.
5298         assert(r->is_free() || r->is_old(), "invariant");
5299         // We now consider them old, so register as such. Leave
5300         // archive regions set that way, however, while still adding
5301         // them to the old set.
5302         if (!r->is_archive()) {
5303           r->set_old();
5304         }
5305         _old_set->add(r);
5306       }
5307       _total_used += r->used();
5308     }
5309 
5310     return false;
5311   }
5312 
5313   size_t total_used() {
5314     return _total_used;
5315   }
5316 };
5317 
5318 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5319   assert_at_safepoint(true /* should_be_vm_thread */);
5320 
5321   if (!free_list_only) {
5322     _young_list->empty_list();
5323   }
5324 
5325   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5326   heap_region_iterate(&cl);
5327 
5328   if (!free_list_only) {
5329     set_used(cl.total_used());
5330     if (_archive_allocator != NULL) {
5331       _archive_allocator->clear_used();
5332     }
5333   }
5334   assert(used_unlocked() == recalculate_used(),
5335          "inconsistent used_unlocked(), "
5336          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5337          used_unlocked(), recalculate_used());
5338 }
5339 
5340 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5341   _refine_cte_cl->set_concurrent(concurrent);
5342 }
5343 
5344 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5345   HeapRegion* hr = heap_region_containing(p);
5346   return hr->is_in(p);
5347 }
5348 
5349 // Methods for the mutator alloc region
5350 
5351 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5352                                                       bool force) {
5353   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5354   assert(!force || g1_policy()->can_expand_young_list(),
5355          "if force is true we should be able to expand the young list");
5356   bool young_list_full = g1_policy()->is_young_list_full();
5357   if (force || !young_list_full) {
5358     HeapRegion* new_alloc_region = new_region(word_size,
5359                                               false /* is_old */,
5360                                               false /* do_expand */);
5361     if (new_alloc_region != NULL) {
5362       set_region_short_lived_locked(new_alloc_region);
5363       _hr_printer.alloc(new_alloc_region, young_list_full);
5364       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5365       return new_alloc_region;
5366     }
5367   }
5368   return NULL;
5369 }
5370 
5371 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5372                                                   size_t allocated_bytes) {
5373   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5374   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5375 
5376   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
5377   increase_used(allocated_bytes);
5378   _hr_printer.retire(alloc_region);
5379   // We update the eden sizes here, when the region is retired,
5380   // instead of when it's allocated, since this is the point that its
5381   // used space has been recored in _summary_bytes_used.
5382   g1mm()->update_eden_size();
5383 }
5384 
5385 // Methods for the GC alloc regions
5386 
5387 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
5388                                                  uint count,
5389                                                  InCSetState dest) {
5390   assert(FreeList_lock->owned_by_self(), "pre-condition");
5391 
5392   if (count < g1_policy()->max_regions(dest)) {
5393     const bool is_survivor = (dest.is_young());
5394     HeapRegion* new_alloc_region = new_region(word_size,
5395                                               !is_survivor,
5396                                               true /* do_expand */);
5397     if (new_alloc_region != NULL) {
5398       // We really only need to do this for old regions given that we
5399       // should never scan survivors. But it doesn't hurt to do it
5400       // for survivors too.
5401       new_alloc_region->record_timestamp();
5402       if (is_survivor) {
5403         new_alloc_region->set_survivor();
5404         _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5405       } else {
5406         new_alloc_region->set_old();
5407         _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5408       }
5409       _hr_printer.alloc(new_alloc_region);
5410       bool during_im = collector_state()->during_initial_mark_pause();
5411       new_alloc_region->note_start_of_copying(during_im);
5412       return new_alloc_region;
5413     }
5414   }
5415   return NULL;
5416 }
5417 
5418 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5419                                              size_t allocated_bytes,
5420                                              InCSetState dest) {
5421   bool during_im = collector_state()->during_initial_mark_pause();
5422   alloc_region->note_end_of_copying(during_im);
5423   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5424   if (dest.is_young()) {
5425     young_list()->add_survivor_region(alloc_region);
5426   } else {
5427     _old_set.add(alloc_region);
5428   }
5429   _hr_printer.retire(alloc_region);
5430 }
5431 
5432 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5433   bool expanded = false;
5434   uint index = _hrm.find_highest_free(&expanded);
5435 
5436   if (index != G1_NO_HRM_INDEX) {
5437     if (expanded) {
5438       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5439                                 HeapRegion::GrainWords * HeapWordSize);
5440     }
5441     _hrm.allocate_free_regions_starting_at(index, 1);
5442     return region_at(index);
5443   }
5444   return NULL;
5445 }
5446 
5447 // Optimized nmethod scanning
5448 
5449 class RegisterNMethodOopClosure: public OopClosure {
5450   G1CollectedHeap* _g1h;
5451   nmethod* _nm;
5452 
5453   template <class T> void do_oop_work(T* p) {
5454     T heap_oop = oopDesc::load_heap_oop(p);
5455     if (!oopDesc::is_null(heap_oop)) {
5456       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5457       HeapRegion* hr = _g1h->heap_region_containing(obj);
5458       assert(!hr->is_continues_humongous(),
5459              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5460              " starting at " HR_FORMAT,
5461              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5462 
5463       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5464       hr->add_strong_code_root_locked(_nm);
5465     }
5466   }
5467 
5468 public:
5469   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5470     _g1h(g1h), _nm(nm) {}
5471 
5472   void do_oop(oop* p)       { do_oop_work(p); }
5473   void do_oop(narrowOop* p) { do_oop_work(p); }
5474 };
5475 
5476 class UnregisterNMethodOopClosure: public OopClosure {
5477   G1CollectedHeap* _g1h;
5478   nmethod* _nm;
5479 
5480   template <class T> void do_oop_work(T* p) {
5481     T heap_oop = oopDesc::load_heap_oop(p);
5482     if (!oopDesc::is_null(heap_oop)) {
5483       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5484       HeapRegion* hr = _g1h->heap_region_containing(obj);
5485       assert(!hr->is_continues_humongous(),
5486              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5487              " starting at " HR_FORMAT,
5488              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5489 
5490       hr->remove_strong_code_root(_nm);
5491     }
5492   }
5493 
5494 public:
5495   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5496     _g1h(g1h), _nm(nm) {}
5497 
5498   void do_oop(oop* p)       { do_oop_work(p); }
5499   void do_oop(narrowOop* p) { do_oop_work(p); }
5500 };
5501 
5502 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5503   CollectedHeap::register_nmethod(nm);
5504 
5505   guarantee(nm != NULL, "sanity");
5506   RegisterNMethodOopClosure reg_cl(this, nm);
5507   nm->oops_do(&reg_cl);
5508 }
5509 
5510 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5511   CollectedHeap::unregister_nmethod(nm);
5512 
5513   guarantee(nm != NULL, "sanity");
5514   UnregisterNMethodOopClosure reg_cl(this, nm);
5515   nm->oops_do(&reg_cl, true);
5516 }
5517 
5518 void G1CollectedHeap::purge_code_root_memory() {
5519   double purge_start = os::elapsedTime();
5520   G1CodeRootSet::purge();
5521   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5522   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5523 }
5524 
5525 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5526   G1CollectedHeap* _g1h;
5527 
5528 public:
5529   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5530     _g1h(g1h) {}
5531 
5532   void do_code_blob(CodeBlob* cb) {
5533     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5534     if (nm == NULL) {
5535       return;
5536     }
5537 
5538     if (ScavengeRootsInCode) {
5539       _g1h->register_nmethod(nm);
5540     }
5541   }
5542 };
5543 
5544 void G1CollectedHeap::rebuild_strong_code_roots() {
5545   RebuildStrongCodeRootClosure blob_cl(this);
5546   CodeCache::blobs_do(&blob_cl);
5547 }