1 /* 2 * Copyright (c) 2001, 2011, 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 "code/icBuffer.hpp" 27 #include "gc_implementation/g1/bufferingOopClosure.hpp" 28 #include "gc_implementation/g1/concurrentG1Refine.hpp" 29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" 31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp" 32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 33 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 34 #include "gc_implementation/g1/g1ErgoVerbose.hpp" 35 #include "gc_implementation/g1/g1MarkSweep.hpp" 36 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 37 #include "gc_implementation/g1/g1RemSet.inline.hpp" 38 #include "gc_implementation/g1/heapRegionRemSet.hpp" 39 #include "gc_implementation/g1/heapRegionSeq.inline.hpp" 40 #include "gc_implementation/g1/vm_operations_g1.hpp" 41 #include "gc_implementation/shared/isGCActiveMark.hpp" 42 #include "memory/gcLocker.inline.hpp" 43 #include "memory/genOopClosures.inline.hpp" 44 #include "memory/generationSpec.hpp" 45 #include "memory/referenceProcessor.hpp" 46 #include "oops/oop.inline.hpp" 47 #include "oops/oop.pcgc.inline.hpp" 48 #include "runtime/aprofiler.hpp" 49 #include "runtime/vmThread.hpp" 50 51 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 52 53 // turn it on so that the contents of the young list (scan-only / 54 // to-be-collected) are printed at "strategic" points before / during 55 // / after the collection --- this is useful for debugging 56 #define YOUNG_LIST_VERBOSE 0 57 // CURRENT STATUS 58 // This file is under construction. Search for "FIXME". 59 60 // INVARIANTS/NOTES 61 // 62 // All allocation activity covered by the G1CollectedHeap interface is 63 // serialized by acquiring the HeapLock. This happens in mem_allocate 64 // and allocate_new_tlab, which are the "entry" points to the 65 // allocation code from the rest of the JVM. (Note that this does not 66 // apply to TLAB allocation, which is not part of this interface: it 67 // is done by clients of this interface.) 68 69 // Notes on implementation of parallelism in different tasks. 70 // 71 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism. 72 // The number of GC workers is passed to heap_region_par_iterate_chunked(). 73 // It does use run_task() which sets _n_workers in the task. 74 // G1ParTask executes g1_process_strong_roots() -> 75 // SharedHeap::process_strong_roots() which calls eventuall to 76 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses 77 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also 78 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap). 79 // 80 81 // Local to this file. 82 83 class RefineCardTableEntryClosure: public CardTableEntryClosure { 84 SuspendibleThreadSet* _sts; 85 G1RemSet* _g1rs; 86 ConcurrentG1Refine* _cg1r; 87 bool _concurrent; 88 public: 89 RefineCardTableEntryClosure(SuspendibleThreadSet* sts, 90 G1RemSet* g1rs, 91 ConcurrentG1Refine* cg1r) : 92 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true) 93 {} 94 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 95 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false); 96 // This path is executed by the concurrent refine or mutator threads, 97 // concurrently, and so we do not care if card_ptr contains references 98 // that point into the collection set. 99 assert(!oops_into_cset, "should be"); 100 101 if (_concurrent && _sts->should_yield()) { 102 // Caller will actually yield. 103 return false; 104 } 105 // Otherwise, we finished successfully; return true. 106 return true; 107 } 108 void set_concurrent(bool b) { _concurrent = b; } 109 }; 110 111 112 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 113 int _calls; 114 G1CollectedHeap* _g1h; 115 CardTableModRefBS* _ctbs; 116 int _histo[256]; 117 public: 118 ClearLoggedCardTableEntryClosure() : 119 _calls(0) 120 { 121 _g1h = G1CollectedHeap::heap(); 122 _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); 123 for (int i = 0; i < 256; i++) _histo[i] = 0; 124 } 125 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 126 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 127 _calls++; 128 unsigned char* ujb = (unsigned char*)card_ptr; 129 int ind = (int)(*ujb); 130 _histo[ind]++; 131 *card_ptr = -1; 132 } 133 return true; 134 } 135 int calls() { return _calls; } 136 void print_histo() { 137 gclog_or_tty->print_cr("Card table value histogram:"); 138 for (int i = 0; i < 256; i++) { 139 if (_histo[i] != 0) { 140 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); 141 } 142 } 143 } 144 }; 145 146 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure { 147 int _calls; 148 G1CollectedHeap* _g1h; 149 CardTableModRefBS* _ctbs; 150 public: 151 RedirtyLoggedCardTableEntryClosure() : 152 _calls(0) 153 { 154 _g1h = G1CollectedHeap::heap(); 155 _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); 156 } 157 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 158 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 159 _calls++; 160 *card_ptr = 0; 161 } 162 return true; 163 } 164 int calls() { return _calls; } 165 }; 166 167 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure { 168 public: 169 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 170 *card_ptr = CardTableModRefBS::dirty_card_val(); 171 return true; 172 } 173 }; 174 175 YoungList::YoungList(G1CollectedHeap* g1h) 176 : _g1h(g1h), _head(NULL), 177 _length(0), 178 _last_sampled_rs_lengths(0), 179 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) 180 { 181 guarantee( check_list_empty(false), "just making sure..." ); 182 } 183 184 void YoungList::push_region(HeapRegion *hr) { 185 assert(!hr->is_young(), "should not already be young"); 186 assert(hr->get_next_young_region() == NULL, "cause it should!"); 187 188 hr->set_next_young_region(_head); 189 _head = hr; 190 191 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 192 ++_length; 193 } 194 195 void YoungList::add_survivor_region(HeapRegion* hr) { 196 assert(hr->is_survivor(), "should be flagged as survivor region"); 197 assert(hr->get_next_young_region() == NULL, "cause it should!"); 198 199 hr->set_next_young_region(_survivor_head); 200 if (_survivor_head == NULL) { 201 _survivor_tail = hr; 202 } 203 _survivor_head = hr; 204 ++_survivor_length; 205 } 206 207 void YoungList::empty_list(HeapRegion* list) { 208 while (list != NULL) { 209 HeapRegion* next = list->get_next_young_region(); 210 list->set_next_young_region(NULL); 211 list->uninstall_surv_rate_group(); 212 list->set_not_young(); 213 list = next; 214 } 215 } 216 217 void YoungList::empty_list() { 218 assert(check_list_well_formed(), "young list should be well formed"); 219 220 empty_list(_head); 221 _head = NULL; 222 _length = 0; 223 224 empty_list(_survivor_head); 225 _survivor_head = NULL; 226 _survivor_tail = NULL; 227 _survivor_length = 0; 228 229 _last_sampled_rs_lengths = 0; 230 231 assert(check_list_empty(false), "just making sure..."); 232 } 233 234 bool YoungList::check_list_well_formed() { 235 bool ret = true; 236 237 size_t length = 0; 238 HeapRegion* curr = _head; 239 HeapRegion* last = NULL; 240 while (curr != NULL) { 241 if (!curr->is_young()) { 242 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 243 "incorrectly tagged (y: %d, surv: %d)", 244 curr->bottom(), curr->end(), 245 curr->is_young(), curr->is_survivor()); 246 ret = false; 247 } 248 ++length; 249 last = curr; 250 curr = curr->get_next_young_region(); 251 } 252 ret = ret && (length == _length); 253 254 if (!ret) { 255 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 256 gclog_or_tty->print_cr("### list has %d entries, _length is %d", 257 length, _length); 258 } 259 260 return ret; 261 } 262 263 bool YoungList::check_list_empty(bool check_sample) { 264 bool ret = true; 265 266 if (_length != 0) { 267 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %d", 268 _length); 269 ret = false; 270 } 271 if (check_sample && _last_sampled_rs_lengths != 0) { 272 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 273 ret = false; 274 } 275 if (_head != NULL) { 276 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 277 ret = false; 278 } 279 if (!ret) { 280 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 281 } 282 283 return ret; 284 } 285 286 void 287 YoungList::rs_length_sampling_init() { 288 _sampled_rs_lengths = 0; 289 _curr = _head; 290 } 291 292 bool 293 YoungList::rs_length_sampling_more() { 294 return _curr != NULL; 295 } 296 297 void 298 YoungList::rs_length_sampling_next() { 299 assert( _curr != NULL, "invariant" ); 300 size_t rs_length = _curr->rem_set()->occupied(); 301 302 _sampled_rs_lengths += rs_length; 303 304 // The current region may not yet have been added to the 305 // incremental collection set (it gets added when it is 306 // retired as the current allocation region). 307 if (_curr->in_collection_set()) { 308 // Update the collection set policy information for this region 309 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 310 } 311 312 _curr = _curr->get_next_young_region(); 313 if (_curr == NULL) { 314 _last_sampled_rs_lengths = _sampled_rs_lengths; 315 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 316 } 317 } 318 319 void 320 YoungList::reset_auxilary_lists() { 321 guarantee( is_empty(), "young list should be empty" ); 322 assert(check_list_well_formed(), "young list should be well formed"); 323 324 // Add survivor regions to SurvRateGroup. 325 _g1h->g1_policy()->note_start_adding_survivor_regions(); 326 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 327 328 int young_index_in_cset = 0; 329 for (HeapRegion* curr = _survivor_head; 330 curr != NULL; 331 curr = curr->get_next_young_region()) { 332 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 333 334 // The region is a non-empty survivor so let's add it to 335 // the incremental collection set for the next evacuation 336 // pause. 337 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 338 young_index_in_cset += 1; 339 } 340 assert((size_t) young_index_in_cset == _survivor_length, 341 "post-condition"); 342 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 343 344 _head = _survivor_head; 345 _length = _survivor_length; 346 if (_survivor_head != NULL) { 347 assert(_survivor_tail != NULL, "cause it shouldn't be"); 348 assert(_survivor_length > 0, "invariant"); 349 _survivor_tail->set_next_young_region(NULL); 350 } 351 352 // Don't clear the survivor list handles until the start of 353 // the next evacuation pause - we need it in order to re-tag 354 // the survivor regions from this evacuation pause as 'young' 355 // at the start of the next. 356 357 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 358 359 assert(check_list_well_formed(), "young list should be well formed"); 360 } 361 362 void YoungList::print() { 363 HeapRegion* lists[] = {_head, _survivor_head}; 364 const char* names[] = {"YOUNG", "SURVIVOR"}; 365 366 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { 367 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 368 HeapRegion *curr = lists[list]; 369 if (curr == NULL) 370 gclog_or_tty->print_cr(" empty"); 371 while (curr != NULL) { 372 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, " 373 "age: %4d, y: %d, surv: %d", 374 curr->bottom(), curr->end(), 375 curr->top(), 376 curr->prev_top_at_mark_start(), 377 curr->next_top_at_mark_start(), 378 curr->top_at_conc_mark_count(), 379 curr->age_in_surv_rate_group_cond(), 380 curr->is_young(), 381 curr->is_survivor()); 382 curr = curr->get_next_young_region(); 383 } 384 } 385 386 gclog_or_tty->print_cr(""); 387 } 388 389 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 390 { 391 // Claim the right to put the region on the dirty cards region list 392 // by installing a self pointer. 393 HeapRegion* next = hr->get_next_dirty_cards_region(); 394 if (next == NULL) { 395 HeapRegion* res = (HeapRegion*) 396 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 397 NULL); 398 if (res == NULL) { 399 HeapRegion* head; 400 do { 401 // Put the region to the dirty cards region list. 402 head = _dirty_cards_region_list; 403 next = (HeapRegion*) 404 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 405 if (next == head) { 406 assert(hr->get_next_dirty_cards_region() == hr, 407 "hr->get_next_dirty_cards_region() != hr"); 408 if (next == NULL) { 409 // The last region in the list points to itself. 410 hr->set_next_dirty_cards_region(hr); 411 } else { 412 hr->set_next_dirty_cards_region(next); 413 } 414 } 415 } while (next != head); 416 } 417 } 418 } 419 420 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 421 { 422 HeapRegion* head; 423 HeapRegion* hr; 424 do { 425 head = _dirty_cards_region_list; 426 if (head == NULL) { 427 return NULL; 428 } 429 HeapRegion* new_head = head->get_next_dirty_cards_region(); 430 if (head == new_head) { 431 // The last region. 432 new_head = NULL; 433 } 434 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 435 head); 436 } while (hr != head); 437 assert(hr != NULL, "invariant"); 438 hr->set_next_dirty_cards_region(NULL); 439 return hr; 440 } 441 442 void G1CollectedHeap::stop_conc_gc_threads() { 443 _cg1r->stop(); 444 _cmThread->stop(); 445 } 446 447 #ifdef ASSERT 448 // A region is added to the collection set as it is retired 449 // so an address p can point to a region which will be in the 450 // collection set but has not yet been retired. This method 451 // therefore is only accurate during a GC pause after all 452 // regions have been retired. It is used for debugging 453 // to check if an nmethod has references to objects that can 454 // be move during a partial collection. Though it can be 455 // inaccurate, it is sufficient for G1 because the conservative 456 // implementation of is_scavengable() for G1 will indicate that 457 // all nmethods must be scanned during a partial collection. 458 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 459 HeapRegion* hr = heap_region_containing(p); 460 return hr != NULL && hr->in_collection_set(); 461 } 462 #endif 463 464 // Returns true if the reference points to an object that 465 // can move in an incremental collecction. 466 bool G1CollectedHeap::is_scavengable(const void* p) { 467 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 468 G1CollectorPolicy* g1p = g1h->g1_policy(); 469 HeapRegion* hr = heap_region_containing(p); 470 if (hr == NULL) { 471 // perm gen (or null) 472 return false; 473 } else { 474 return !hr->isHumongous(); 475 } 476 } 477 478 void G1CollectedHeap::check_ct_logs_at_safepoint() { 479 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 480 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 481 482 // Count the dirty cards at the start. 483 CountNonCleanMemRegionClosure count1(this); 484 ct_bs->mod_card_iterate(&count1); 485 int orig_count = count1.n(); 486 487 // First clear the logged cards. 488 ClearLoggedCardTableEntryClosure clear; 489 dcqs.set_closure(&clear); 490 dcqs.apply_closure_to_all_completed_buffers(); 491 dcqs.iterate_closure_all_threads(false); 492 clear.print_histo(); 493 494 // Now ensure that there's no dirty cards. 495 CountNonCleanMemRegionClosure count2(this); 496 ct_bs->mod_card_iterate(&count2); 497 if (count2.n() != 0) { 498 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 499 count2.n(), orig_count); 500 } 501 guarantee(count2.n() == 0, "Card table should be clean."); 502 503 RedirtyLoggedCardTableEntryClosure redirty; 504 JavaThread::dirty_card_queue_set().set_closure(&redirty); 505 dcqs.apply_closure_to_all_completed_buffers(); 506 dcqs.iterate_closure_all_threads(false); 507 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 508 clear.calls(), orig_count); 509 guarantee(redirty.calls() == clear.calls(), 510 "Or else mechanism is broken."); 511 512 CountNonCleanMemRegionClosure count3(this); 513 ct_bs->mod_card_iterate(&count3); 514 if (count3.n() != orig_count) { 515 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 516 orig_count, count3.n()); 517 guarantee(count3.n() >= orig_count, "Should have restored them all."); 518 } 519 520 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 521 } 522 523 // Private class members. 524 525 G1CollectedHeap* G1CollectedHeap::_g1h; 526 527 // Private methods. 528 529 HeapRegion* 530 G1CollectedHeap::new_region_try_secondary_free_list() { 531 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 532 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 533 if (!_secondary_free_list.is_empty()) { 534 if (G1ConcRegionFreeingVerbose) { 535 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 536 "secondary_free_list has "SIZE_FORMAT" entries", 537 _secondary_free_list.length()); 538 } 539 // It looks as if there are free regions available on the 540 // secondary_free_list. Let's move them to the free_list and try 541 // again to allocate from it. 542 append_secondary_free_list(); 543 544 assert(!_free_list.is_empty(), "if the secondary_free_list was not " 545 "empty we should have moved at least one entry to the free_list"); 546 HeapRegion* res = _free_list.remove_head(); 547 if (G1ConcRegionFreeingVerbose) { 548 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 549 "allocated "HR_FORMAT" from secondary_free_list", 550 HR_FORMAT_PARAMS(res)); 551 } 552 return res; 553 } 554 555 // Wait here until we get notifed either when (a) there are no 556 // more free regions coming or (b) some regions have been moved on 557 // the secondary_free_list. 558 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 559 } 560 561 if (G1ConcRegionFreeingVerbose) { 562 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 563 "could not allocate from secondary_free_list"); 564 } 565 return NULL; 566 } 567 568 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) { 569 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords, 570 "the only time we use this to allocate a humongous region is " 571 "when we are allocating a single humongous region"); 572 573 HeapRegion* res; 574 if (G1StressConcRegionFreeing) { 575 if (!_secondary_free_list.is_empty()) { 576 if (G1ConcRegionFreeingVerbose) { 577 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 578 "forced to look at the secondary_free_list"); 579 } 580 res = new_region_try_secondary_free_list(); 581 if (res != NULL) { 582 return res; 583 } 584 } 585 } 586 res = _free_list.remove_head_or_null(); 587 if (res == NULL) { 588 if (G1ConcRegionFreeingVerbose) { 589 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 590 "res == NULL, trying the secondary_free_list"); 591 } 592 res = new_region_try_secondary_free_list(); 593 } 594 if (res == NULL && do_expand) { 595 ergo_verbose1(ErgoHeapSizing, 596 "attempt heap expansion", 597 ergo_format_reason("region allocation request failed") 598 ergo_format_byte("allocation request"), 599 word_size * HeapWordSize); 600 if (expand(word_size * HeapWordSize)) { 601 // Even though the heap was expanded, it might not have reached 602 // the desired size. So, we cannot assume that the allocation 603 // will succeed. 604 res = _free_list.remove_head_or_null(); 605 } 606 } 607 return res; 608 } 609 610 size_t G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions, 611 size_t word_size) { 612 assert(isHumongous(word_size), "word_size should be humongous"); 613 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 614 615 size_t first = G1_NULL_HRS_INDEX; 616 if (num_regions == 1) { 617 // Only one region to allocate, no need to go through the slower 618 // path. The caller will attempt the expasion if this fails, so 619 // let's not try to expand here too. 620 HeapRegion* hr = new_region(word_size, false /* do_expand */); 621 if (hr != NULL) { 622 first = hr->hrs_index(); 623 } else { 624 first = G1_NULL_HRS_INDEX; 625 } 626 } else { 627 // We can't allocate humongous regions while cleanupComplete() is 628 // running, since some of the regions we find to be empty might not 629 // yet be added to the free list and it is not straightforward to 630 // know which list they are on so that we can remove them. Note 631 // that we only need to do this if we need to allocate more than 632 // one region to satisfy the current humongous allocation 633 // request. If we are only allocating one region we use the common 634 // region allocation code (see above). 635 wait_while_free_regions_coming(); 636 append_secondary_free_list_if_not_empty_with_lock(); 637 638 if (free_regions() >= num_regions) { 639 first = _hrs.find_contiguous(num_regions); 640 if (first != G1_NULL_HRS_INDEX) { 641 for (size_t i = first; i < first + num_regions; ++i) { 642 HeapRegion* hr = region_at(i); 643 assert(hr->is_empty(), "sanity"); 644 assert(is_on_master_free_list(hr), "sanity"); 645 hr->set_pending_removal(true); 646 } 647 _free_list.remove_all_pending(num_regions); 648 } 649 } 650 } 651 return first; 652 } 653 654 HeapWord* 655 G1CollectedHeap::humongous_obj_allocate_initialize_regions(size_t first, 656 size_t num_regions, 657 size_t word_size) { 658 assert(first != G1_NULL_HRS_INDEX, "pre-condition"); 659 assert(isHumongous(word_size), "word_size should be humongous"); 660 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 661 662 // Index of last region in the series + 1. 663 size_t last = first + num_regions; 664 665 // We need to initialize the region(s) we just discovered. This is 666 // a bit tricky given that it can happen concurrently with 667 // refinement threads refining cards on these regions and 668 // potentially wanting to refine the BOT as they are scanning 669 // those cards (this can happen shortly after a cleanup; see CR 670 // 6991377). So we have to set up the region(s) carefully and in 671 // a specific order. 672 673 // The word size sum of all the regions we will allocate. 674 size_t word_size_sum = num_regions * HeapRegion::GrainWords; 675 assert(word_size <= word_size_sum, "sanity"); 676 677 // This will be the "starts humongous" region. 678 HeapRegion* first_hr = region_at(first); 679 // The header of the new object will be placed at the bottom of 680 // the first region. 681 HeapWord* new_obj = first_hr->bottom(); 682 // This will be the new end of the first region in the series that 683 // should also match the end of the last region in the seriers. 684 HeapWord* new_end = new_obj + word_size_sum; 685 // This will be the new top of the first region that will reflect 686 // this allocation. 687 HeapWord* new_top = new_obj + word_size; 688 689 // First, we need to zero the header of the space that we will be 690 // allocating. When we update top further down, some refinement 691 // threads might try to scan the region. By zeroing the header we 692 // ensure that any thread that will try to scan the region will 693 // come across the zero klass word and bail out. 694 // 695 // NOTE: It would not have been correct to have used 696 // CollectedHeap::fill_with_object() and make the space look like 697 // an int array. The thread that is doing the allocation will 698 // later update the object header to a potentially different array 699 // type and, for a very short period of time, the klass and length 700 // fields will be inconsistent. This could cause a refinement 701 // thread to calculate the object size incorrectly. 702 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 703 704 // We will set up the first region as "starts humongous". This 705 // will also update the BOT covering all the regions to reflect 706 // that there is a single object that starts at the bottom of the 707 // first region. 708 first_hr->set_startsHumongous(new_top, new_end); 709 710 // Then, if there are any, we will set up the "continues 711 // humongous" regions. 712 HeapRegion* hr = NULL; 713 for (size_t i = first + 1; i < last; ++i) { 714 hr = region_at(i); 715 hr->set_continuesHumongous(first_hr); 716 } 717 // If we have "continues humongous" regions (hr != NULL), then the 718 // end of the last one should match new_end. 719 assert(hr == NULL || hr->end() == new_end, "sanity"); 720 721 // Up to this point no concurrent thread would have been able to 722 // do any scanning on any region in this series. All the top 723 // fields still point to bottom, so the intersection between 724 // [bottom,top] and [card_start,card_end] will be empty. Before we 725 // update the top fields, we'll do a storestore to make sure that 726 // no thread sees the update to top before the zeroing of the 727 // object header and the BOT initialization. 728 OrderAccess::storestore(); 729 730 // Now that the BOT and the object header have been initialized, 731 // we can update top of the "starts humongous" region. 732 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 733 "new_top should be in this region"); 734 first_hr->set_top(new_top); 735 if (_hr_printer.is_active()) { 736 HeapWord* bottom = first_hr->bottom(); 737 HeapWord* end = first_hr->orig_end(); 738 if ((first + 1) == last) { 739 // the series has a single humongous region 740 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 741 } else { 742 // the series has more than one humongous regions 743 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 744 } 745 } 746 747 // Now, we will update the top fields of the "continues humongous" 748 // regions. The reason we need to do this is that, otherwise, 749 // these regions would look empty and this will confuse parts of 750 // G1. For example, the code that looks for a consecutive number 751 // of empty regions will consider them empty and try to 752 // re-allocate them. We can extend is_empty() to also include 753 // !continuesHumongous(), but it is easier to just update the top 754 // fields here. The way we set top for all regions (i.e., top == 755 // end for all regions but the last one, top == new_top for the 756 // last one) is actually used when we will free up the humongous 757 // region in free_humongous_region(). 758 hr = NULL; 759 for (size_t i = first + 1; i < last; ++i) { 760 hr = region_at(i); 761 if ((i + 1) == last) { 762 // last continues humongous region 763 assert(hr->bottom() < new_top && new_top <= hr->end(), 764 "new_top should fall on this region"); 765 hr->set_top(new_top); 766 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 767 } else { 768 // not last one 769 assert(new_top > hr->end(), "new_top should be above this region"); 770 hr->set_top(hr->end()); 771 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 772 } 773 } 774 // If we have continues humongous regions (hr != NULL), then the 775 // end of the last one should match new_end and its top should 776 // match new_top. 777 assert(hr == NULL || 778 (hr->end() == new_end && hr->top() == new_top), "sanity"); 779 780 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 781 _summary_bytes_used += first_hr->used(); 782 _humongous_set.add(first_hr); 783 784 return new_obj; 785 } 786 787 // If could fit into free regions w/o expansion, try. 788 // Otherwise, if can expand, do so. 789 // Otherwise, if using ex regions might help, try with ex given back. 790 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 791 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 792 793 verify_region_sets_optional(); 794 795 size_t num_regions = 796 round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 797 size_t x_size = expansion_regions(); 798 size_t fs = _hrs.free_suffix(); 799 size_t first = humongous_obj_allocate_find_first(num_regions, word_size); 800 if (first == G1_NULL_HRS_INDEX) { 801 // The only thing we can do now is attempt expansion. 802 if (fs + x_size >= num_regions) { 803 // If the number of regions we're trying to allocate for this 804 // object is at most the number of regions in the free suffix, 805 // then the call to humongous_obj_allocate_find_first() above 806 // should have succeeded and we wouldn't be here. 807 // 808 // We should only be trying to expand when the free suffix is 809 // not sufficient for the object _and_ we have some expansion 810 // room available. 811 assert(num_regions > fs, "earlier allocation should have succeeded"); 812 813 ergo_verbose1(ErgoHeapSizing, 814 "attempt heap expansion", 815 ergo_format_reason("humongous allocation request failed") 816 ergo_format_byte("allocation request"), 817 word_size * HeapWordSize); 818 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) { 819 // Even though the heap was expanded, it might not have 820 // reached the desired size. So, we cannot assume that the 821 // allocation will succeed. 822 first = humongous_obj_allocate_find_first(num_regions, word_size); 823 } 824 } 825 } 826 827 HeapWord* result = NULL; 828 if (first != G1_NULL_HRS_INDEX) { 829 result = 830 humongous_obj_allocate_initialize_regions(first, num_regions, word_size); 831 assert(result != NULL, "it should always return a valid result"); 832 833 // A successful humongous object allocation changes the used space 834 // information of the old generation so we need to recalculate the 835 // sizes and update the jstat counters here. 836 g1mm()->update_sizes(); 837 } 838 839 verify_region_sets_optional(); 840 841 return result; 842 } 843 844 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 845 assert_heap_not_locked_and_not_at_safepoint(); 846 assert(!isHumongous(word_size), "we do not allow humongous TLABs"); 847 848 unsigned int dummy_gc_count_before; 849 return attempt_allocation(word_size, &dummy_gc_count_before); 850 } 851 852 HeapWord* 853 G1CollectedHeap::mem_allocate(size_t word_size, 854 bool* gc_overhead_limit_was_exceeded) { 855 assert_heap_not_locked_and_not_at_safepoint(); 856 857 // Loop until the allocation is satisified, or unsatisfied after GC. 858 for (int try_count = 1; /* we'll return */; try_count += 1) { 859 unsigned int gc_count_before; 860 861 HeapWord* result = NULL; 862 if (!isHumongous(word_size)) { 863 result = attempt_allocation(word_size, &gc_count_before); 864 } else { 865 result = attempt_allocation_humongous(word_size, &gc_count_before); 866 } 867 if (result != NULL) { 868 return result; 869 } 870 871 // Create the garbage collection operation... 872 VM_G1CollectForAllocation op(gc_count_before, word_size); 873 // ...and get the VM thread to execute it. 874 VMThread::execute(&op); 875 876 if (op.prologue_succeeded() && op.pause_succeeded()) { 877 // If the operation was successful we'll return the result even 878 // if it is NULL. If the allocation attempt failed immediately 879 // after a Full GC, it's unlikely we'll be able to allocate now. 880 HeapWord* result = op.result(); 881 if (result != NULL && !isHumongous(word_size)) { 882 // Allocations that take place on VM operations do not do any 883 // card dirtying and we have to do it here. We only have to do 884 // this for non-humongous allocations, though. 885 dirty_young_block(result, word_size); 886 } 887 return result; 888 } else { 889 assert(op.result() == NULL, 890 "the result should be NULL if the VM op did not succeed"); 891 } 892 893 // Give a warning if we seem to be looping forever. 894 if ((QueuedAllocationWarningCount > 0) && 895 (try_count % QueuedAllocationWarningCount == 0)) { 896 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 897 } 898 } 899 900 ShouldNotReachHere(); 901 return NULL; 902 } 903 904 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 905 unsigned int *gc_count_before_ret) { 906 // Make sure you read the note in attempt_allocation_humongous(). 907 908 assert_heap_not_locked_and_not_at_safepoint(); 909 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 910 "be called for humongous allocation requests"); 911 912 // We should only get here after the first-level allocation attempt 913 // (attempt_allocation()) failed to allocate. 914 915 // We will loop until a) we manage to successfully perform the 916 // allocation or b) we successfully schedule a collection which 917 // fails to perform the allocation. b) is the only case when we'll 918 // return NULL. 919 HeapWord* result = NULL; 920 for (int try_count = 1; /* we'll return */; try_count += 1) { 921 bool should_try_gc; 922 unsigned int gc_count_before; 923 924 { 925 MutexLockerEx x(Heap_lock); 926 927 result = _mutator_alloc_region.attempt_allocation_locked(word_size, 928 false /* bot_updates */); 929 if (result != NULL) { 930 return result; 931 } 932 933 // If we reach here, attempt_allocation_locked() above failed to 934 // allocate a new region. So the mutator alloc region should be NULL. 935 assert(_mutator_alloc_region.get() == NULL, "only way to get here"); 936 937 if (GC_locker::is_active_and_needs_gc()) { 938 if (g1_policy()->can_expand_young_list()) { 939 // No need for an ergo verbose message here, 940 // can_expand_young_list() does this when it returns true. 941 result = _mutator_alloc_region.attempt_allocation_force(word_size, 942 false /* bot_updates */); 943 if (result != NULL) { 944 return result; 945 } 946 } 947 should_try_gc = false; 948 } else { 949 // Read the GC count while still holding the Heap_lock. 950 gc_count_before = SharedHeap::heap()->total_collections(); 951 should_try_gc = true; 952 } 953 } 954 955 if (should_try_gc) { 956 bool succeeded; 957 result = do_collection_pause(word_size, gc_count_before, &succeeded); 958 if (result != NULL) { 959 assert(succeeded, "only way to get back a non-NULL result"); 960 return result; 961 } 962 963 if (succeeded) { 964 // If we get here we successfully scheduled a collection which 965 // failed to allocate. No point in trying to allocate 966 // further. We'll just return NULL. 967 MutexLockerEx x(Heap_lock); 968 *gc_count_before_ret = SharedHeap::heap()->total_collections(); 969 return NULL; 970 } 971 } else { 972 GC_locker::stall_until_clear(); 973 } 974 975 // We can reach here if we were unsuccessul in scheduling a 976 // collection (because another thread beat us to it) or if we were 977 // stalled due to the GC locker. In either can we should retry the 978 // allocation attempt in case another thread successfully 979 // performed a collection and reclaimed enough space. We do the 980 // first attempt (without holding the Heap_lock) here and the 981 // follow-on attempt will be at the start of the next loop 982 // iteration (after taking the Heap_lock). 983 result = _mutator_alloc_region.attempt_allocation(word_size, 984 false /* bot_updates */); 985 if (result != NULL ){ 986 return result; 987 } 988 989 // Give a warning if we seem to be looping forever. 990 if ((QueuedAllocationWarningCount > 0) && 991 (try_count % QueuedAllocationWarningCount == 0)) { 992 warning("G1CollectedHeap::attempt_allocation_slow() " 993 "retries %d times", try_count); 994 } 995 } 996 997 ShouldNotReachHere(); 998 return NULL; 999 } 1000 1001 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1002 unsigned int * gc_count_before_ret) { 1003 // The structure of this method has a lot of similarities to 1004 // attempt_allocation_slow(). The reason these two were not merged 1005 // into a single one is that such a method would require several "if 1006 // allocation is not humongous do this, otherwise do that" 1007 // conditional paths which would obscure its flow. In fact, an early 1008 // version of this code did use a unified method which was harder to 1009 // follow and, as a result, it had subtle bugs that were hard to 1010 // track down. So keeping these two methods separate allows each to 1011 // be more readable. It will be good to keep these two in sync as 1012 // much as possible. 1013 1014 assert_heap_not_locked_and_not_at_safepoint(); 1015 assert(isHumongous(word_size), "attempt_allocation_humongous() " 1016 "should only be called for humongous allocations"); 1017 1018 // We will loop until a) we manage to successfully perform the 1019 // allocation or b) we successfully schedule a collection which 1020 // fails to perform the allocation. b) is the only case when we'll 1021 // return NULL. 1022 HeapWord* result = NULL; 1023 for (int try_count = 1; /* we'll return */; try_count += 1) { 1024 bool should_try_gc; 1025 unsigned int gc_count_before; 1026 1027 { 1028 MutexLockerEx x(Heap_lock); 1029 1030 // Given that humongous objects are not allocated in young 1031 // regions, we'll first try to do the allocation without doing a 1032 // collection hoping that there's enough space in the heap. 1033 result = humongous_obj_allocate(word_size); 1034 if (result != NULL) { 1035 return result; 1036 } 1037 1038 if (GC_locker::is_active_and_needs_gc()) { 1039 should_try_gc = false; 1040 } else { 1041 // Read the GC count while still holding the Heap_lock. 1042 gc_count_before = SharedHeap::heap()->total_collections(); 1043 should_try_gc = true; 1044 } 1045 } 1046 1047 if (should_try_gc) { 1048 // If we failed to allocate the humongous object, we should try to 1049 // do a collection pause (if we're allowed) in case it reclaims 1050 // enough space for the allocation to succeed after the pause. 1051 1052 bool succeeded; 1053 result = do_collection_pause(word_size, gc_count_before, &succeeded); 1054 if (result != NULL) { 1055 assert(succeeded, "only way to get back a non-NULL result"); 1056 return result; 1057 } 1058 1059 if (succeeded) { 1060 // If we get here we successfully scheduled a collection which 1061 // failed to allocate. No point in trying to allocate 1062 // further. We'll just return NULL. 1063 MutexLockerEx x(Heap_lock); 1064 *gc_count_before_ret = SharedHeap::heap()->total_collections(); 1065 return NULL; 1066 } 1067 } else { 1068 GC_locker::stall_until_clear(); 1069 } 1070 1071 // We can reach here if we were unsuccessul in scheduling a 1072 // collection (because another thread beat us to it) or if we were 1073 // stalled due to the GC locker. In either can we should retry the 1074 // allocation attempt in case another thread successfully 1075 // performed a collection and reclaimed enough space. Give a 1076 // warning if we seem to be looping forever. 1077 1078 if ((QueuedAllocationWarningCount > 0) && 1079 (try_count % QueuedAllocationWarningCount == 0)) { 1080 warning("G1CollectedHeap::attempt_allocation_humongous() " 1081 "retries %d times", try_count); 1082 } 1083 } 1084 1085 ShouldNotReachHere(); 1086 return NULL; 1087 } 1088 1089 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1090 bool expect_null_mutator_alloc_region) { 1091 assert_at_safepoint(true /* should_be_vm_thread */); 1092 assert(_mutator_alloc_region.get() == NULL || 1093 !expect_null_mutator_alloc_region, 1094 "the current alloc region was unexpectedly found to be non-NULL"); 1095 1096 if (!isHumongous(word_size)) { 1097 return _mutator_alloc_region.attempt_allocation_locked(word_size, 1098 false /* bot_updates */); 1099 } else { 1100 return humongous_obj_allocate(word_size); 1101 } 1102 1103 ShouldNotReachHere(); 1104 } 1105 1106 class PostMCRemSetClearClosure: public HeapRegionClosure { 1107 ModRefBarrierSet* _mr_bs; 1108 public: 1109 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {} 1110 bool doHeapRegion(HeapRegion* r) { 1111 r->reset_gc_time_stamp(); 1112 if (r->continuesHumongous()) 1113 return false; 1114 HeapRegionRemSet* hrrs = r->rem_set(); 1115 if (hrrs != NULL) hrrs->clear(); 1116 // You might think here that we could clear just the cards 1117 // corresponding to the used region. But no: if we leave a dirty card 1118 // in a region we might allocate into, then it would prevent that card 1119 // from being enqueued, and cause it to be missed. 1120 // Re: the performance cost: we shouldn't be doing full GC anyway! 1121 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1122 return false; 1123 } 1124 }; 1125 1126 1127 class PostMCRemSetInvalidateClosure: public HeapRegionClosure { 1128 ModRefBarrierSet* _mr_bs; 1129 public: 1130 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {} 1131 bool doHeapRegion(HeapRegion* r) { 1132 if (r->continuesHumongous()) return false; 1133 if (r->used_region().word_size() != 0) { 1134 _mr_bs->invalidate(r->used_region(), true /*whole heap*/); 1135 } 1136 return false; 1137 } 1138 }; 1139 1140 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1141 G1CollectedHeap* _g1h; 1142 UpdateRSOopClosure _cl; 1143 int _worker_i; 1144 public: 1145 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1146 _cl(g1->g1_rem_set(), worker_i), 1147 _worker_i(worker_i), 1148 _g1h(g1) 1149 { } 1150 1151 bool doHeapRegion(HeapRegion* r) { 1152 if (!r->continuesHumongous()) { 1153 _cl.set_from(r); 1154 r->oop_iterate(&_cl); 1155 } 1156 return false; 1157 } 1158 }; 1159 1160 class ParRebuildRSTask: public AbstractGangTask { 1161 G1CollectedHeap* _g1; 1162 public: 1163 ParRebuildRSTask(G1CollectedHeap* g1) 1164 : AbstractGangTask("ParRebuildRSTask"), 1165 _g1(g1) 1166 { } 1167 1168 void work(int i) { 1169 RebuildRSOutOfRegionClosure rebuild_rs(_g1, i); 1170 _g1->heap_region_par_iterate_chunked(&rebuild_rs, i, 1171 _g1->workers()->active_workers(), 1172 HeapRegion::RebuildRSClaimValue); 1173 } 1174 }; 1175 1176 class PostCompactionPrinterClosure: public HeapRegionClosure { 1177 private: 1178 G1HRPrinter* _hr_printer; 1179 public: 1180 bool doHeapRegion(HeapRegion* hr) { 1181 assert(!hr->is_young(), "not expecting to find young regions"); 1182 // We only generate output for non-empty regions. 1183 if (!hr->is_empty()) { 1184 if (!hr->isHumongous()) { 1185 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1186 } else if (hr->startsHumongous()) { 1187 if (hr->capacity() == HeapRegion::GrainBytes) { 1188 // single humongous region 1189 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1190 } else { 1191 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1192 } 1193 } else { 1194 assert(hr->continuesHumongous(), "only way to get here"); 1195 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1196 } 1197 } 1198 return false; 1199 } 1200 1201 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1202 : _hr_printer(hr_printer) { } 1203 }; 1204 1205 bool G1CollectedHeap::do_collection(bool explicit_gc, 1206 bool clear_all_soft_refs, 1207 size_t word_size) { 1208 assert_at_safepoint(true /* should_be_vm_thread */); 1209 1210 if (GC_locker::check_active_before_gc()) { 1211 return false; 1212 } 1213 1214 SvcGCMarker sgcm(SvcGCMarker::FULL); 1215 ResourceMark rm; 1216 1217 if (PrintHeapAtGC) { 1218 Universe::print_heap_before_gc(); 1219 } 1220 1221 HRSPhaseSetter x(HRSPhaseFullGC); 1222 verify_region_sets_optional(); 1223 1224 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1225 collector_policy()->should_clear_all_soft_refs(); 1226 1227 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1228 1229 { 1230 IsGCActiveMark x; 1231 1232 // Timing 1233 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc); 1234 assert(!system_gc || explicit_gc, "invariant"); 1235 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 1236 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 1237 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC", 1238 PrintGC, true, gclog_or_tty); 1239 1240 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1241 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1242 1243 double start = os::elapsedTime(); 1244 g1_policy()->record_full_collection_start(); 1245 1246 wait_while_free_regions_coming(); 1247 append_secondary_free_list_if_not_empty_with_lock(); 1248 1249 gc_prologue(true); 1250 increment_total_collections(true /* full gc */); 1251 1252 size_t g1h_prev_used = used(); 1253 assert(used() == recalculate_used(), "Should be equal"); 1254 1255 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) { 1256 HandleMark hm; // Discard invalid handles created during verification 1257 gclog_or_tty->print(" VerifyBeforeGC:"); 1258 prepare_for_verify(); 1259 Universe::verify(/* allow dirty */ true, 1260 /* silent */ false, 1261 /* option */ VerifyOption_G1UsePrevMarking); 1262 1263 } 1264 pre_full_gc_dump(); 1265 1266 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1267 1268 // Disable discovery and empty the discovered lists 1269 // for the CM ref processor. 1270 ref_processor_cm()->disable_discovery(); 1271 ref_processor_cm()->abandon_partial_discovery(); 1272 ref_processor_cm()->verify_no_references_recorded(); 1273 1274 // Abandon current iterations of concurrent marking and concurrent 1275 // refinement, if any are in progress. 1276 concurrent_mark()->abort(); 1277 1278 // Make sure we'll choose a new allocation region afterwards. 1279 release_mutator_alloc_region(); 1280 abandon_gc_alloc_regions(); 1281 g1_rem_set()->cleanupHRRS(); 1282 1283 // We should call this after we retire any currently active alloc 1284 // regions so that all the ALLOC / RETIRE events are generated 1285 // before the start GC event. 1286 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1287 1288 // We may have added regions to the current incremental collection 1289 // set between the last GC or pause and now. We need to clear the 1290 // incremental collection set and then start rebuilding it afresh 1291 // after this full GC. 1292 abandon_collection_set(g1_policy()->inc_cset_head()); 1293 g1_policy()->clear_incremental_cset(); 1294 g1_policy()->stop_incremental_cset_building(); 1295 1296 tear_down_region_sets(false /* free_list_only */); 1297 g1_policy()->set_gcs_are_young(true); 1298 1299 // See the comments in g1CollectedHeap.hpp and 1300 // G1CollectedHeap::ref_processing_init() about 1301 // how reference processing currently works in G1. 1302 1303 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1304 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1305 1306 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1307 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1308 1309 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1310 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1311 1312 // Do collection work 1313 { 1314 HandleMark hm; // Discard invalid handles created during gc 1315 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1316 } 1317 1318 assert(free_regions() == 0, "we should not have added any free regions"); 1319 rebuild_region_sets(false /* free_list_only */); 1320 1321 // Enqueue any discovered reference objects that have 1322 // not been removed from the discovered lists. 1323 ref_processor_stw()->enqueue_discovered_references(); 1324 1325 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1326 1327 MemoryService::track_memory_usage(); 1328 1329 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) { 1330 HandleMark hm; // Discard invalid handles created during verification 1331 gclog_or_tty->print(" VerifyAfterGC:"); 1332 prepare_for_verify(); 1333 Universe::verify(/* allow dirty */ false, 1334 /* silent */ false, 1335 /* option */ VerifyOption_G1UsePrevMarking); 1336 1337 } 1338 1339 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1340 ref_processor_stw()->verify_no_references_recorded(); 1341 1342 // Note: since we've just done a full GC, concurrent 1343 // marking is no longer active. Therefore we need not 1344 // re-enable reference discovery for the CM ref processor. 1345 // That will be done at the start of the next marking cycle. 1346 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1347 ref_processor_cm()->verify_no_references_recorded(); 1348 1349 reset_gc_time_stamp(); 1350 // Since everything potentially moved, we will clear all remembered 1351 // sets, and clear all cards. Later we will rebuild remebered 1352 // sets. We will also reset the GC time stamps of the regions. 1353 PostMCRemSetClearClosure rs_clear(mr_bs()); 1354 heap_region_iterate(&rs_clear); 1355 1356 // Resize the heap if necessary. 1357 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1358 1359 if (_hr_printer.is_active()) { 1360 // We should do this after we potentially resize the heap so 1361 // that all the COMMIT / UNCOMMIT events are generated before 1362 // the end GC event. 1363 1364 PostCompactionPrinterClosure cl(hr_printer()); 1365 heap_region_iterate(&cl); 1366 1367 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1368 } 1369 1370 if (_cg1r->use_cache()) { 1371 _cg1r->clear_and_record_card_counts(); 1372 _cg1r->clear_hot_cache(); 1373 } 1374 1375 // Rebuild remembered sets of all regions. 1376 if (G1CollectedHeap::use_parallel_gc_threads()) { 1377 int n_workers = 1378 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1379 workers()->active_workers(), 1380 Threads::number_of_non_daemon_threads()); 1381 assert(UseDynamicNumberOfGCThreads || 1382 n_workers == workers()->total_workers(), 1383 "If not dynamic should be using all the workers"); 1384 workers()->set_active_workers(n_workers); 1385 // Set parallel threads in the heap (_n_par_threads) only 1386 // before a parallel phase and always reset it to 0 after 1387 // the phase so that the number of parallel threads does 1388 // no get carried forward to a serial phase where there 1389 // may be code that is "possibly_parallel". 1390 set_par_threads(n_workers); 1391 1392 ParRebuildRSTask rebuild_rs_task(this); 1393 assert(check_heap_region_claim_values( 1394 HeapRegion::InitialClaimValue), "sanity check"); 1395 assert(UseDynamicNumberOfGCThreads || 1396 workers()->active_workers() == workers()->total_workers(), 1397 "Unless dynamic should use total workers"); 1398 // Use the most recent number of active workers 1399 assert(workers()->active_workers() > 0, 1400 "Active workers not properly set"); 1401 set_par_threads(workers()->active_workers()); 1402 workers()->run_task(&rebuild_rs_task); 1403 set_par_threads(0); 1404 assert(check_heap_region_claim_values( 1405 HeapRegion::RebuildRSClaimValue), "sanity check"); 1406 reset_heap_region_claim_values(); 1407 } else { 1408 RebuildRSOutOfRegionClosure rebuild_rs(this); 1409 heap_region_iterate(&rebuild_rs); 1410 } 1411 1412 if (PrintGC) { 1413 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity()); 1414 } 1415 1416 if (true) { // FIXME 1417 // Ask the permanent generation to adjust size for full collections 1418 perm()->compute_new_size(); 1419 } 1420 1421 // Start a new incremental collection set for the next pause 1422 assert(g1_policy()->collection_set() == NULL, "must be"); 1423 g1_policy()->start_incremental_cset_building(); 1424 1425 // Clear the _cset_fast_test bitmap in anticipation of adding 1426 // regions to the incremental collection set for the next 1427 // evacuation pause. 1428 clear_cset_fast_test(); 1429 1430 init_mutator_alloc_region(); 1431 1432 double end = os::elapsedTime(); 1433 g1_policy()->record_full_collection_end(); 1434 1435 #ifdef TRACESPINNING 1436 ParallelTaskTerminator::print_termination_counts(); 1437 #endif 1438 1439 gc_epilogue(true); 1440 1441 // Discard all rset updates 1442 JavaThread::dirty_card_queue_set().abandon_logs(); 1443 assert(!G1DeferredRSUpdate 1444 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); 1445 } 1446 1447 _young_list->reset_sampled_info(); 1448 // At this point there should be no regions in the 1449 // entire heap tagged as young. 1450 assert( check_young_list_empty(true /* check_heap */), 1451 "young list should be empty at this point"); 1452 1453 // Update the number of full collections that have been completed. 1454 increment_full_collections_completed(false /* concurrent */); 1455 1456 _hrs.verify_optional(); 1457 verify_region_sets_optional(); 1458 1459 if (PrintHeapAtGC) { 1460 Universe::print_heap_after_gc(); 1461 } 1462 g1mm()->update_sizes(); 1463 post_full_gc_dump(); 1464 1465 return true; 1466 } 1467 1468 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1469 // do_collection() will return whether it succeeded in performing 1470 // the GC. Currently, there is no facility on the 1471 // do_full_collection() API to notify the caller than the collection 1472 // did not succeed (e.g., because it was locked out by the GC 1473 // locker). So, right now, we'll ignore the return value. 1474 bool dummy = do_collection(true, /* explicit_gc */ 1475 clear_all_soft_refs, 1476 0 /* word_size */); 1477 } 1478 1479 // This code is mostly copied from TenuredGeneration. 1480 void 1481 G1CollectedHeap:: 1482 resize_if_necessary_after_full_collection(size_t word_size) { 1483 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check"); 1484 1485 // Include the current allocation, if any, and bytes that will be 1486 // pre-allocated to support collections, as "used". 1487 const size_t used_after_gc = used(); 1488 const size_t capacity_after_gc = capacity(); 1489 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1490 1491 // This is enforced in arguments.cpp. 1492 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1493 "otherwise the code below doesn't make sense"); 1494 1495 // We don't have floating point command-line arguments 1496 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1497 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1498 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1499 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1500 1501 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1502 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1503 1504 // We have to be careful here as these two calculations can overflow 1505 // 32-bit size_t's. 1506 double used_after_gc_d = (double) used_after_gc; 1507 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1508 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1509 1510 // Let's make sure that they are both under the max heap size, which 1511 // by default will make them fit into a size_t. 1512 double desired_capacity_upper_bound = (double) max_heap_size; 1513 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1514 desired_capacity_upper_bound); 1515 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1516 desired_capacity_upper_bound); 1517 1518 // We can now safely turn them into size_t's. 1519 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1520 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1521 1522 // This assert only makes sense here, before we adjust them 1523 // with respect to the min and max heap size. 1524 assert(minimum_desired_capacity <= maximum_desired_capacity, 1525 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1526 "maximum_desired_capacity = "SIZE_FORMAT, 1527 minimum_desired_capacity, maximum_desired_capacity)); 1528 1529 // Should not be greater than the heap max size. No need to adjust 1530 // it with respect to the heap min size as it's a lower bound (i.e., 1531 // we'll try to make the capacity larger than it, not smaller). 1532 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1533 // Should not be less than the heap min size. No need to adjust it 1534 // with respect to the heap max size as it's an upper bound (i.e., 1535 // we'll try to make the capacity smaller than it, not greater). 1536 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1537 1538 if (capacity_after_gc < minimum_desired_capacity) { 1539 // Don't expand unless it's significant 1540 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1541 ergo_verbose4(ErgoHeapSizing, 1542 "attempt heap expansion", 1543 ergo_format_reason("capacity lower than " 1544 "min desired capacity after Full GC") 1545 ergo_format_byte("capacity") 1546 ergo_format_byte("occupancy") 1547 ergo_format_byte_perc("min desired capacity"), 1548 capacity_after_gc, used_after_gc, 1549 minimum_desired_capacity, (double) MinHeapFreeRatio); 1550 expand(expand_bytes); 1551 1552 // No expansion, now see if we want to shrink 1553 } else if (capacity_after_gc > maximum_desired_capacity) { 1554 // Capacity too large, compute shrinking size 1555 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1556 ergo_verbose4(ErgoHeapSizing, 1557 "attempt heap shrinking", 1558 ergo_format_reason("capacity higher than " 1559 "max desired capacity after Full GC") 1560 ergo_format_byte("capacity") 1561 ergo_format_byte("occupancy") 1562 ergo_format_byte_perc("max desired capacity"), 1563 capacity_after_gc, used_after_gc, 1564 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1565 shrink(shrink_bytes); 1566 } 1567 } 1568 1569 1570 HeapWord* 1571 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1572 bool* succeeded) { 1573 assert_at_safepoint(true /* should_be_vm_thread */); 1574 1575 *succeeded = true; 1576 // Let's attempt the allocation first. 1577 HeapWord* result = 1578 attempt_allocation_at_safepoint(word_size, 1579 false /* expect_null_mutator_alloc_region */); 1580 if (result != NULL) { 1581 assert(*succeeded, "sanity"); 1582 return result; 1583 } 1584 1585 // In a G1 heap, we're supposed to keep allocation from failing by 1586 // incremental pauses. Therefore, at least for now, we'll favor 1587 // expansion over collection. (This might change in the future if we can 1588 // do something smarter than full collection to satisfy a failed alloc.) 1589 result = expand_and_allocate(word_size); 1590 if (result != NULL) { 1591 assert(*succeeded, "sanity"); 1592 return result; 1593 } 1594 1595 // Expansion didn't work, we'll try to do a Full GC. 1596 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1597 false, /* clear_all_soft_refs */ 1598 word_size); 1599 if (!gc_succeeded) { 1600 *succeeded = false; 1601 return NULL; 1602 } 1603 1604 // Retry the allocation 1605 result = attempt_allocation_at_safepoint(word_size, 1606 true /* expect_null_mutator_alloc_region */); 1607 if (result != NULL) { 1608 assert(*succeeded, "sanity"); 1609 return result; 1610 } 1611 1612 // Then, try a Full GC that will collect all soft references. 1613 gc_succeeded = do_collection(false, /* explicit_gc */ 1614 true, /* clear_all_soft_refs */ 1615 word_size); 1616 if (!gc_succeeded) { 1617 *succeeded = false; 1618 return NULL; 1619 } 1620 1621 // Retry the allocation once more 1622 result = attempt_allocation_at_safepoint(word_size, 1623 true /* expect_null_mutator_alloc_region */); 1624 if (result != NULL) { 1625 assert(*succeeded, "sanity"); 1626 return result; 1627 } 1628 1629 assert(!collector_policy()->should_clear_all_soft_refs(), 1630 "Flag should have been handled and cleared prior to this point"); 1631 1632 // What else? We might try synchronous finalization later. If the total 1633 // space available is large enough for the allocation, then a more 1634 // complete compaction phase than we've tried so far might be 1635 // appropriate. 1636 assert(*succeeded, "sanity"); 1637 return NULL; 1638 } 1639 1640 // Attempting to expand the heap sufficiently 1641 // to support an allocation of the given "word_size". If 1642 // successful, perform the allocation and return the address of the 1643 // allocated block, or else "NULL". 1644 1645 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1646 assert_at_safepoint(true /* should_be_vm_thread */); 1647 1648 verify_region_sets_optional(); 1649 1650 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1651 ergo_verbose1(ErgoHeapSizing, 1652 "attempt heap expansion", 1653 ergo_format_reason("allocation request failed") 1654 ergo_format_byte("allocation request"), 1655 word_size * HeapWordSize); 1656 if (expand(expand_bytes)) { 1657 _hrs.verify_optional(); 1658 verify_region_sets_optional(); 1659 return attempt_allocation_at_safepoint(word_size, 1660 false /* expect_null_mutator_alloc_region */); 1661 } 1662 return NULL; 1663 } 1664 1665 void G1CollectedHeap::update_committed_space(HeapWord* old_end, 1666 HeapWord* new_end) { 1667 assert(old_end != new_end, "don't call this otherwise"); 1668 assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); 1669 1670 // Update the committed mem region. 1671 _g1_committed.set_end(new_end); 1672 // Tell the card table about the update. 1673 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); 1674 // Tell the BOT about the update. 1675 _bot_shared->resize(_g1_committed.word_size()); 1676 } 1677 1678 bool G1CollectedHeap::expand(size_t expand_bytes) { 1679 size_t old_mem_size = _g1_storage.committed_size(); 1680 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1681 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1682 HeapRegion::GrainBytes); 1683 ergo_verbose2(ErgoHeapSizing, 1684 "expand the heap", 1685 ergo_format_byte("requested expansion amount") 1686 ergo_format_byte("attempted expansion amount"), 1687 expand_bytes, aligned_expand_bytes); 1688 1689 // First commit the memory. 1690 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1691 bool successful = _g1_storage.expand_by(aligned_expand_bytes); 1692 if (successful) { 1693 // Then propagate this update to the necessary data structures. 1694 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1695 update_committed_space(old_end, new_end); 1696 1697 FreeRegionList expansion_list("Local Expansion List"); 1698 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); 1699 assert(mr.start() == old_end, "post-condition"); 1700 // mr might be a smaller region than what was requested if 1701 // expand_by() was unable to allocate the HeapRegion instances 1702 assert(mr.end() <= new_end, "post-condition"); 1703 1704 size_t actual_expand_bytes = mr.byte_size(); 1705 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1706 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), 1707 "post-condition"); 1708 if (actual_expand_bytes < aligned_expand_bytes) { 1709 // We could not expand _hrs to the desired size. In this case we 1710 // need to shrink the committed space accordingly. 1711 assert(mr.end() < new_end, "invariant"); 1712 1713 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; 1714 // First uncommit the memory. 1715 _g1_storage.shrink_by(diff_bytes); 1716 // Then propagate this update to the necessary data structures. 1717 update_committed_space(new_end, mr.end()); 1718 } 1719 _free_list.add_as_tail(&expansion_list); 1720 1721 if (_hr_printer.is_active()) { 1722 HeapWord* curr = mr.start(); 1723 while (curr < mr.end()) { 1724 HeapWord* curr_end = curr + HeapRegion::GrainWords; 1725 _hr_printer.commit(curr, curr_end); 1726 curr = curr_end; 1727 } 1728 assert(curr == mr.end(), "post-condition"); 1729 } 1730 g1_policy()->record_new_heap_size(n_regions()); 1731 } else { 1732 ergo_verbose0(ErgoHeapSizing, 1733 "did not expand the heap", 1734 ergo_format_reason("heap expansion operation failed")); 1735 // The expansion of the virtual storage space was unsuccessful. 1736 // Let's see if it was because we ran out of swap. 1737 if (G1ExitOnExpansionFailure && 1738 _g1_storage.uncommitted_size() >= aligned_expand_bytes) { 1739 // We had head room... 1740 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion"); 1741 } 1742 } 1743 return successful; 1744 } 1745 1746 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1747 size_t old_mem_size = _g1_storage.committed_size(); 1748 size_t aligned_shrink_bytes = 1749 ReservedSpace::page_align_size_down(shrink_bytes); 1750 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1751 HeapRegion::GrainBytes); 1752 size_t num_regions_deleted = 0; 1753 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted); 1754 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1755 assert(mr.end() == old_end, "post-condition"); 1756 1757 ergo_verbose3(ErgoHeapSizing, 1758 "shrink the heap", 1759 ergo_format_byte("requested shrinking amount") 1760 ergo_format_byte("aligned shrinking amount") 1761 ergo_format_byte("attempted shrinking amount"), 1762 shrink_bytes, aligned_shrink_bytes, mr.byte_size()); 1763 if (mr.byte_size() > 0) { 1764 if (_hr_printer.is_active()) { 1765 HeapWord* curr = mr.end(); 1766 while (curr > mr.start()) { 1767 HeapWord* curr_end = curr; 1768 curr -= HeapRegion::GrainWords; 1769 _hr_printer.uncommit(curr, curr_end); 1770 } 1771 assert(curr == mr.start(), "post-condition"); 1772 } 1773 1774 _g1_storage.shrink_by(mr.byte_size()); 1775 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1776 assert(mr.start() == new_end, "post-condition"); 1777 1778 _expansion_regions += num_regions_deleted; 1779 update_committed_space(old_end, new_end); 1780 HeapRegionRemSet::shrink_heap(n_regions()); 1781 g1_policy()->record_new_heap_size(n_regions()); 1782 } else { 1783 ergo_verbose0(ErgoHeapSizing, 1784 "did not shrink the heap", 1785 ergo_format_reason("heap shrinking operation failed")); 1786 } 1787 } 1788 1789 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1790 verify_region_sets_optional(); 1791 1792 // We should only reach here at the end of a Full GC which means we 1793 // should not not be holding to any GC alloc regions. The method 1794 // below will make sure of that and do any remaining clean up. 1795 abandon_gc_alloc_regions(); 1796 1797 // Instead of tearing down / rebuilding the free lists here, we 1798 // could instead use the remove_all_pending() method on free_list to 1799 // remove only the ones that we need to remove. 1800 tear_down_region_sets(true /* free_list_only */); 1801 shrink_helper(shrink_bytes); 1802 rebuild_region_sets(true /* free_list_only */); 1803 1804 _hrs.verify_optional(); 1805 verify_region_sets_optional(); 1806 } 1807 1808 // Public methods. 1809 1810 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1811 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1812 #endif // _MSC_VER 1813 1814 1815 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1816 SharedHeap(policy_), 1817 _g1_policy(policy_), 1818 _dirty_card_queue_set(false), 1819 _into_cset_dirty_card_queue_set(false), 1820 _is_alive_closure_cm(this), 1821 _is_alive_closure_stw(this), 1822 _ref_processor_cm(NULL), 1823 _ref_processor_stw(NULL), 1824 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1825 _bot_shared(NULL), 1826 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL), 1827 _evac_failure_scan_stack(NULL) , 1828 _mark_in_progress(false), 1829 _cg1r(NULL), _summary_bytes_used(0), 1830 _g1mm(NULL), 1831 _refine_cte_cl(NULL), 1832 _full_collection(false), 1833 _free_list("Master Free List"), 1834 _secondary_free_list("Secondary Free List"), 1835 _old_set("Old Set"), 1836 _humongous_set("Master Humongous Set"), 1837 _free_regions_coming(false), 1838 _young_list(new YoungList(this)), 1839 _gc_time_stamp(0), 1840 _retained_old_gc_alloc_region(NULL), 1841 _surviving_young_words(NULL), 1842 _full_collections_completed(0), 1843 _in_cset_fast_test(NULL), 1844 _in_cset_fast_test_base(NULL), 1845 _dirty_cards_region_list(NULL), 1846 _worker_cset_start_region(NULL), 1847 _worker_cset_start_region_time_stamp(NULL) { 1848 _g1h = this; // To catch bugs. 1849 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1850 vm_exit_during_initialization("Failed necessary allocation."); 1851 } 1852 1853 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1854 1855 int n_queues = MAX2((int)ParallelGCThreads, 1); 1856 _task_queues = new RefToScanQueueSet(n_queues); 1857 1858 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1859 assert(n_rem_sets > 0, "Invariant."); 1860 1861 HeapRegionRemSetIterator** iter_arr = 1862 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues); 1863 for (int i = 0; i < n_queues; i++) { 1864 iter_arr[i] = new HeapRegionRemSetIterator(); 1865 } 1866 _rem_set_iterator = iter_arr; 1867 1868 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues); 1869 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues); 1870 1871 for (int i = 0; i < n_queues; i++) { 1872 RefToScanQueue* q = new RefToScanQueue(); 1873 q->initialize(); 1874 _task_queues->register_queue(i, q); 1875 } 1876 1877 clear_cset_start_regions(); 1878 1879 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1880 } 1881 1882 jint G1CollectedHeap::initialize() { 1883 CollectedHeap::pre_initialize(); 1884 os::enable_vtime(); 1885 1886 // Necessary to satisfy locking discipline assertions. 1887 1888 MutexLocker x(Heap_lock); 1889 1890 // We have to initialize the printer before committing the heap, as 1891 // it will be used then. 1892 _hr_printer.set_active(G1PrintHeapRegions); 1893 1894 // While there are no constraints in the GC code that HeapWordSize 1895 // be any particular value, there are multiple other areas in the 1896 // system which believe this to be true (e.g. oop->object_size in some 1897 // cases incorrectly returns the size in wordSize units rather than 1898 // HeapWordSize). 1899 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1900 1901 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1902 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1903 1904 // Ensure that the sizes are properly aligned. 1905 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1906 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1907 1908 _cg1r = new ConcurrentG1Refine(); 1909 1910 // Reserve the maximum. 1911 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation(); 1912 // Includes the perm-gen. 1913 1914 // When compressed oops are enabled, the preferred heap base 1915 // is calculated by subtracting the requested size from the 1916 // 32Gb boundary and using the result as the base address for 1917 // heap reservation. If the requested size is not aligned to 1918 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1919 // into the ReservedHeapSpace constructor) then the actual 1920 // base of the reserved heap may end up differing from the 1921 // address that was requested (i.e. the preferred heap base). 1922 // If this happens then we could end up using a non-optimal 1923 // compressed oops mode. 1924 1925 // Since max_byte_size is aligned to the size of a heap region (checked 1926 // above), we also need to align the perm gen size as it might not be. 1927 const size_t total_reserved = max_byte_size + 1928 align_size_up(pgs->max_size(), HeapRegion::GrainBytes); 1929 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm"); 1930 1931 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop); 1932 1933 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes, 1934 UseLargePages, addr); 1935 1936 if (UseCompressedOops) { 1937 if (addr != NULL && !heap_rs.is_reserved()) { 1938 // Failed to reserve at specified address - the requested memory 1939 // region is taken already, for example, by 'java' launcher. 1940 // Try again to reserver heap higher. 1941 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop); 1942 1943 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes, 1944 UseLargePages, addr); 1945 1946 if (addr != NULL && !heap_rs0.is_reserved()) { 1947 // Failed to reserve at specified address again - give up. 1948 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop); 1949 assert(addr == NULL, ""); 1950 1951 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes, 1952 UseLargePages, addr); 1953 heap_rs = heap_rs1; 1954 } else { 1955 heap_rs = heap_rs0; 1956 } 1957 } 1958 } 1959 1960 if (!heap_rs.is_reserved()) { 1961 vm_exit_during_initialization("Could not reserve enough space for object heap"); 1962 return JNI_ENOMEM; 1963 } 1964 1965 // It is important to do this in a way such that concurrent readers can't 1966 // temporarily think somethings in the heap. (I've actually seen this 1967 // happen in asserts: DLD.) 1968 _reserved.set_word_size(0); 1969 _reserved.set_start((HeapWord*)heap_rs.base()); 1970 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 1971 1972 _expansion_regions = max_byte_size/HeapRegion::GrainBytes; 1973 1974 // Create the gen rem set (and barrier set) for the entire reserved region. 1975 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 1976 set_barrier_set(rem_set()->bs()); 1977 if (barrier_set()->is_a(BarrierSet::ModRef)) { 1978 _mr_bs = (ModRefBarrierSet*)_barrier_set; 1979 } else { 1980 vm_exit_during_initialization("G1 requires a mod ref bs."); 1981 return JNI_ENOMEM; 1982 } 1983 1984 // Also create a G1 rem set. 1985 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) { 1986 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs()); 1987 } else { 1988 vm_exit_during_initialization("G1 requires a cardtable mod ref bs."); 1989 return JNI_ENOMEM; 1990 } 1991 1992 // Carve out the G1 part of the heap. 1993 1994 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1995 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), 1996 g1_rs.size()/HeapWordSize); 1997 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size); 1998 1999 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set()); 2000 2001 _g1_storage.initialize(g1_rs, 0); 2002 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); 2003 _hrs.initialize((HeapWord*) _g1_reserved.start(), 2004 (HeapWord*) _g1_reserved.end(), 2005 _expansion_regions); 2006 2007 // 6843694 - ensure that the maximum region index can fit 2008 // in the remembered set structures. 2009 const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2010 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2011 2012 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2013 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2014 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2015 "too many cards per region"); 2016 2017 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1); 2018 2019 _bot_shared = new G1BlockOffsetSharedArray(_reserved, 2020 heap_word_size(init_byte_size)); 2021 2022 _g1h = this; 2023 2024 _in_cset_fast_test_length = max_regions(); 2025 _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length); 2026 2027 // We're biasing _in_cset_fast_test to avoid subtracting the 2028 // beginning of the heap every time we want to index; basically 2029 // it's the same with what we do with the card table. 2030 _in_cset_fast_test = _in_cset_fast_test_base - 2031 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes); 2032 2033 // Clear the _cset_fast_test bitmap in anticipation of adding 2034 // regions to the incremental collection set for the first 2035 // evacuation pause. 2036 clear_cset_fast_test(); 2037 2038 // Create the ConcurrentMark data structure and thread. 2039 // (Must do this late, so that "max_regions" is defined.) 2040 _cm = new ConcurrentMark(heap_rs, (int) max_regions()); 2041 _cmThread = _cm->cmThread(); 2042 2043 // Initialize the from_card cache structure of HeapRegionRemSet. 2044 HeapRegionRemSet::init_heap(max_regions()); 2045 2046 // Now expand into the initial heap size. 2047 if (!expand(init_byte_size)) { 2048 vm_exit_during_initialization("Failed to allocate initial heap."); 2049 return JNI_ENOMEM; 2050 } 2051 2052 // Perform any initialization actions delegated to the policy. 2053 g1_policy()->init(); 2054 2055 _refine_cte_cl = 2056 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(), 2057 g1_rem_set(), 2058 concurrent_g1_refine()); 2059 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 2060 2061 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2062 SATB_Q_FL_lock, 2063 G1SATBProcessCompletedThreshold, 2064 Shared_SATB_Q_lock); 2065 2066 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2067 DirtyCardQ_FL_lock, 2068 concurrent_g1_refine()->yellow_zone(), 2069 concurrent_g1_refine()->red_zone(), 2070 Shared_DirtyCardQ_lock); 2071 2072 if (G1DeferredRSUpdate) { 2073 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2074 DirtyCardQ_FL_lock, 2075 -1, // never trigger processing 2076 -1, // no limit on length 2077 Shared_DirtyCardQ_lock, 2078 &JavaThread::dirty_card_queue_set()); 2079 } 2080 2081 // Initialize the card queue set used to hold cards containing 2082 // references into the collection set. 2083 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon, 2084 DirtyCardQ_FL_lock, 2085 -1, // never trigger processing 2086 -1, // no limit on length 2087 Shared_DirtyCardQ_lock, 2088 &JavaThread::dirty_card_queue_set()); 2089 2090 // In case we're keeping closure specialization stats, initialize those 2091 // counts and that mechanism. 2092 SpecializationStats::clear(); 2093 2094 // Do later initialization work for concurrent refinement. 2095 _cg1r->init(); 2096 2097 // Here we allocate the dummy full region that is required by the 2098 // G1AllocRegion class. If we don't pass an address in the reserved 2099 // space here, lots of asserts fire. 2100 2101 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, 2102 _g1_reserved.start()); 2103 // We'll re-use the same region whether the alloc region will 2104 // require BOT updates or not and, if it doesn't, then a non-young 2105 // region will complain that it cannot support allocations without 2106 // BOT updates. So we'll tag the dummy region as young to avoid that. 2107 dummy_region->set_young(); 2108 // Make sure it's full. 2109 dummy_region->set_top(dummy_region->end()); 2110 G1AllocRegion::setup(this, dummy_region); 2111 2112 init_mutator_alloc_region(); 2113 2114 // Do create of the monitoring and management support so that 2115 // values in the heap have been properly initialized. 2116 _g1mm = new G1MonitoringSupport(this); 2117 2118 return JNI_OK; 2119 } 2120 2121 void G1CollectedHeap::ref_processing_init() { 2122 // Reference processing in G1 currently works as follows: 2123 // 2124 // * There are two reference processor instances. One is 2125 // used to record and process discovered references 2126 // during concurrent marking; the other is used to 2127 // record and process references during STW pauses 2128 // (both full and incremental). 2129 // * Both ref processors need to 'span' the entire heap as 2130 // the regions in the collection set may be dotted around. 2131 // 2132 // * For the concurrent marking ref processor: 2133 // * Reference discovery is enabled at initial marking. 2134 // * Reference discovery is disabled and the discovered 2135 // references processed etc during remarking. 2136 // * Reference discovery is MT (see below). 2137 // * Reference discovery requires a barrier (see below). 2138 // * Reference processing may or may not be MT 2139 // (depending on the value of ParallelRefProcEnabled 2140 // and ParallelGCThreads). 2141 // * A full GC disables reference discovery by the CM 2142 // ref processor and abandons any entries on it's 2143 // discovered lists. 2144 // 2145 // * For the STW processor: 2146 // * Non MT discovery is enabled at the start of a full GC. 2147 // * Processing and enqueueing during a full GC is non-MT. 2148 // * During a full GC, references are processed after marking. 2149 // 2150 // * Discovery (may or may not be MT) is enabled at the start 2151 // of an incremental evacuation pause. 2152 // * References are processed near the end of a STW evacuation pause. 2153 // * For both types of GC: 2154 // * Discovery is atomic - i.e. not concurrent. 2155 // * Reference discovery will not need a barrier. 2156 2157 SharedHeap::ref_processing_init(); 2158 MemRegion mr = reserved_region(); 2159 2160 // Concurrent Mark ref processor 2161 _ref_processor_cm = 2162 new ReferenceProcessor(mr, // span 2163 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2164 // mt processing 2165 (int) ParallelGCThreads, 2166 // degree of mt processing 2167 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2168 // mt discovery 2169 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2170 // degree of mt discovery 2171 false, 2172 // Reference discovery is not atomic 2173 &_is_alive_closure_cm, 2174 // is alive closure 2175 // (for efficiency/performance) 2176 true); 2177 // Setting next fields of discovered 2178 // lists requires a barrier. 2179 2180 // STW ref processor 2181 _ref_processor_stw = 2182 new ReferenceProcessor(mr, // span 2183 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2184 // mt processing 2185 MAX2((int)ParallelGCThreads, 1), 2186 // degree of mt processing 2187 (ParallelGCThreads > 1), 2188 // mt discovery 2189 MAX2((int)ParallelGCThreads, 1), 2190 // degree of mt discovery 2191 true, 2192 // Reference discovery is atomic 2193 &_is_alive_closure_stw, 2194 // is alive closure 2195 // (for efficiency/performance) 2196 false); 2197 // Setting next fields of discovered 2198 // lists requires a barrier. 2199 } 2200 2201 size_t G1CollectedHeap::capacity() const { 2202 return _g1_committed.byte_size(); 2203 } 2204 2205 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2206 DirtyCardQueue* into_cset_dcq, 2207 bool concurrent, 2208 int worker_i) { 2209 // Clean cards in the hot card cache 2210 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq); 2211 2212 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2213 int n_completed_buffers = 0; 2214 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2215 n_completed_buffers++; 2216 } 2217 g1_policy()->record_update_rs_processed_buffers(worker_i, 2218 (double) n_completed_buffers); 2219 dcqs.clear_n_completed_buffers(); 2220 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2221 } 2222 2223 2224 // Computes the sum of the storage used by the various regions. 2225 2226 size_t G1CollectedHeap::used() const { 2227 assert(Heap_lock->owner() != NULL, 2228 "Should be owned on this thread's behalf."); 2229 size_t result = _summary_bytes_used; 2230 // Read only once in case it is set to NULL concurrently 2231 HeapRegion* hr = _mutator_alloc_region.get(); 2232 if (hr != NULL) 2233 result += hr->used(); 2234 return result; 2235 } 2236 2237 size_t G1CollectedHeap::used_unlocked() const { 2238 size_t result = _summary_bytes_used; 2239 return result; 2240 } 2241 2242 class SumUsedClosure: public HeapRegionClosure { 2243 size_t _used; 2244 public: 2245 SumUsedClosure() : _used(0) {} 2246 bool doHeapRegion(HeapRegion* r) { 2247 if (!r->continuesHumongous()) { 2248 _used += r->used(); 2249 } 2250 return false; 2251 } 2252 size_t result() { return _used; } 2253 }; 2254 2255 size_t G1CollectedHeap::recalculate_used() const { 2256 SumUsedClosure blk; 2257 heap_region_iterate(&blk); 2258 return blk.result(); 2259 } 2260 2261 size_t G1CollectedHeap::unsafe_max_alloc() { 2262 if (free_regions() > 0) return HeapRegion::GrainBytes; 2263 // otherwise, is there space in the current allocation region? 2264 2265 // We need to store the current allocation region in a local variable 2266 // here. The problem is that this method doesn't take any locks and 2267 // there may be other threads which overwrite the current allocation 2268 // region field. attempt_allocation(), for example, sets it to NULL 2269 // and this can happen *after* the NULL check here but before the call 2270 // to free(), resulting in a SIGSEGV. Note that this doesn't appear 2271 // to be a problem in the optimized build, since the two loads of the 2272 // current allocation region field are optimized away. 2273 HeapRegion* hr = _mutator_alloc_region.get(); 2274 if (hr == NULL) { 2275 return 0; 2276 } 2277 return hr->free(); 2278 } 2279 2280 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2281 return 2282 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) || 2283 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent)); 2284 } 2285 2286 #ifndef PRODUCT 2287 void G1CollectedHeap::allocate_dummy_regions() { 2288 // Let's fill up most of the region 2289 size_t word_size = HeapRegion::GrainWords - 1024; 2290 // And as a result the region we'll allocate will be humongous. 2291 guarantee(isHumongous(word_size), "sanity"); 2292 2293 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2294 // Let's use the existing mechanism for the allocation 2295 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2296 if (dummy_obj != NULL) { 2297 MemRegion mr(dummy_obj, word_size); 2298 CollectedHeap::fill_with_object(mr); 2299 } else { 2300 // If we can't allocate once, we probably cannot allocate 2301 // again. Let's get out of the loop. 2302 break; 2303 } 2304 } 2305 } 2306 #endif // !PRODUCT 2307 2308 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) { 2309 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2310 2311 // We assume that if concurrent == true, then the caller is a 2312 // concurrent thread that was joined the Suspendible Thread 2313 // Set. If there's ever a cheap way to check this, we should add an 2314 // assert here. 2315 2316 // We have already incremented _total_full_collections at the start 2317 // of the GC, so total_full_collections() represents how many full 2318 // collections have been started. 2319 unsigned int full_collections_started = total_full_collections(); 2320 2321 // Given that this method is called at the end of a Full GC or of a 2322 // concurrent cycle, and those can be nested (i.e., a Full GC can 2323 // interrupt a concurrent cycle), the number of full collections 2324 // completed should be either one (in the case where there was no 2325 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2326 // behind the number of full collections started. 2327 2328 // This is the case for the inner caller, i.e. a Full GC. 2329 assert(concurrent || 2330 (full_collections_started == _full_collections_completed + 1) || 2331 (full_collections_started == _full_collections_completed + 2), 2332 err_msg("for inner caller (Full GC): full_collections_started = %u " 2333 "is inconsistent with _full_collections_completed = %u", 2334 full_collections_started, _full_collections_completed)); 2335 2336 // This is the case for the outer caller, i.e. the concurrent cycle. 2337 assert(!concurrent || 2338 (full_collections_started == _full_collections_completed + 1), 2339 err_msg("for outer caller (concurrent cycle): " 2340 "full_collections_started = %u " 2341 "is inconsistent with _full_collections_completed = %u", 2342 full_collections_started, _full_collections_completed)); 2343 2344 _full_collections_completed += 1; 2345 2346 // We need to clear the "in_progress" flag in the CM thread before 2347 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2348 // is set) so that if a waiter requests another System.gc() it doesn't 2349 // incorrectly see that a marking cyle is still in progress. 2350 if (concurrent) { 2351 _cmThread->clear_in_progress(); 2352 } 2353 2354 // This notify_all() will ensure that a thread that called 2355 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2356 // and it's waiting for a full GC to finish will be woken up. It is 2357 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2358 FullGCCount_lock->notify_all(); 2359 } 2360 2361 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) { 2362 assert_at_safepoint(true /* should_be_vm_thread */); 2363 GCCauseSetter gcs(this, cause); 2364 switch (cause) { 2365 case GCCause::_heap_inspection: 2366 case GCCause::_heap_dump: { 2367 HandleMark hm; 2368 do_full_collection(false); // don't clear all soft refs 2369 break; 2370 } 2371 default: // XXX FIX ME 2372 ShouldNotReachHere(); // Unexpected use of this function 2373 } 2374 } 2375 2376 void G1CollectedHeap::collect(GCCause::Cause cause) { 2377 // The caller doesn't have the Heap_lock 2378 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock"); 2379 2380 unsigned int gc_count_before; 2381 unsigned int full_gc_count_before; 2382 { 2383 MutexLocker ml(Heap_lock); 2384 2385 // Read the GC count while holding the Heap_lock 2386 gc_count_before = SharedHeap::heap()->total_collections(); 2387 full_gc_count_before = SharedHeap::heap()->total_full_collections(); 2388 } 2389 2390 if (should_do_concurrent_full_gc(cause)) { 2391 // Schedule an initial-mark evacuation pause that will start a 2392 // concurrent cycle. We're setting word_size to 0 which means that 2393 // we are not requesting a post-GC allocation. 2394 VM_G1IncCollectionPause op(gc_count_before, 2395 0, /* word_size */ 2396 true, /* should_initiate_conc_mark */ 2397 g1_policy()->max_pause_time_ms(), 2398 cause); 2399 VMThread::execute(&op); 2400 } else { 2401 if (cause == GCCause::_gc_locker 2402 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2403 2404 // Schedule a standard evacuation pause. We're setting word_size 2405 // to 0 which means that we are not requesting a post-GC allocation. 2406 VM_G1IncCollectionPause op(gc_count_before, 2407 0, /* word_size */ 2408 false, /* should_initiate_conc_mark */ 2409 g1_policy()->max_pause_time_ms(), 2410 cause); 2411 VMThread::execute(&op); 2412 } else { 2413 // Schedule a Full GC. 2414 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2415 VMThread::execute(&op); 2416 } 2417 } 2418 } 2419 2420 bool G1CollectedHeap::is_in(const void* p) const { 2421 if (_g1_committed.contains(p)) { 2422 // Given that we know that p is in the committed space, 2423 // heap_region_containing_raw() should successfully 2424 // return the containing region. 2425 HeapRegion* hr = heap_region_containing_raw(p); 2426 return hr->is_in(p); 2427 } else { 2428 return _perm_gen->as_gen()->is_in(p); 2429 } 2430 } 2431 2432 // Iteration functions. 2433 2434 // Iterates an OopClosure over all ref-containing fields of objects 2435 // within a HeapRegion. 2436 2437 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2438 MemRegion _mr; 2439 OopClosure* _cl; 2440 public: 2441 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl) 2442 : _mr(mr), _cl(cl) {} 2443 bool doHeapRegion(HeapRegion* r) { 2444 if (! r->continuesHumongous()) { 2445 r->oop_iterate(_cl); 2446 } 2447 return false; 2448 } 2449 }; 2450 2451 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) { 2452 IterateOopClosureRegionClosure blk(_g1_committed, cl); 2453 heap_region_iterate(&blk); 2454 if (do_perm) { 2455 perm_gen()->oop_iterate(cl); 2456 } 2457 } 2458 2459 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) { 2460 IterateOopClosureRegionClosure blk(mr, cl); 2461 heap_region_iterate(&blk); 2462 if (do_perm) { 2463 perm_gen()->oop_iterate(cl); 2464 } 2465 } 2466 2467 // Iterates an ObjectClosure over all objects within a HeapRegion. 2468 2469 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2470 ObjectClosure* _cl; 2471 public: 2472 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2473 bool doHeapRegion(HeapRegion* r) { 2474 if (! r->continuesHumongous()) { 2475 r->object_iterate(_cl); 2476 } 2477 return false; 2478 } 2479 }; 2480 2481 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) { 2482 IterateObjectClosureRegionClosure blk(cl); 2483 heap_region_iterate(&blk); 2484 if (do_perm) { 2485 perm_gen()->object_iterate(cl); 2486 } 2487 } 2488 2489 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) { 2490 // FIXME: is this right? 2491 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap"); 2492 } 2493 2494 // Calls a SpaceClosure on a HeapRegion. 2495 2496 class SpaceClosureRegionClosure: public HeapRegionClosure { 2497 SpaceClosure* _cl; 2498 public: 2499 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2500 bool doHeapRegion(HeapRegion* r) { 2501 _cl->do_space(r); 2502 return false; 2503 } 2504 }; 2505 2506 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2507 SpaceClosureRegionClosure blk(cl); 2508 heap_region_iterate(&blk); 2509 } 2510 2511 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2512 _hrs.iterate(cl); 2513 } 2514 2515 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r, 2516 HeapRegionClosure* cl) const { 2517 _hrs.iterate_from(r, cl); 2518 } 2519 2520 void 2521 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2522 int worker, 2523 int no_of_par_workers, 2524 jint claim_value) { 2525 const size_t regions = n_regions(); 2526 const size_t max_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 2527 no_of_par_workers : 2528 1); 2529 assert(UseDynamicNumberOfGCThreads || 2530 no_of_par_workers == workers()->total_workers(), 2531 "Non dynamic should use fixed number of workers"); 2532 // try to spread out the starting points of the workers 2533 const size_t start_index = regions / max_workers * (size_t) worker; 2534 2535 // each worker will actually look at all regions 2536 for (size_t count = 0; count < regions; ++count) { 2537 const size_t index = (start_index + count) % regions; 2538 assert(0 <= index && index < regions, "sanity"); 2539 HeapRegion* r = region_at(index); 2540 // we'll ignore "continues humongous" regions (we'll process them 2541 // when we come across their corresponding "start humongous" 2542 // region) and regions already claimed 2543 if (r->claim_value() == claim_value || r->continuesHumongous()) { 2544 continue; 2545 } 2546 // OK, try to claim it 2547 if (r->claimHeapRegion(claim_value)) { 2548 // success! 2549 assert(!r->continuesHumongous(), "sanity"); 2550 if (r->startsHumongous()) { 2551 // If the region is "starts humongous" we'll iterate over its 2552 // "continues humongous" first; in fact we'll do them 2553 // first. The order is important. In on case, calling the 2554 // closure on the "starts humongous" region might de-allocate 2555 // and clear all its "continues humongous" regions and, as a 2556 // result, we might end up processing them twice. So, we'll do 2557 // them first (notice: most closures will ignore them anyway) and 2558 // then we'll do the "starts humongous" region. 2559 for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) { 2560 HeapRegion* chr = region_at(ch_index); 2561 2562 // if the region has already been claimed or it's not 2563 // "continues humongous" we're done 2564 if (chr->claim_value() == claim_value || 2565 !chr->continuesHumongous()) { 2566 break; 2567 } 2568 2569 // Noone should have claimed it directly. We can given 2570 // that we claimed its "starts humongous" region. 2571 assert(chr->claim_value() != claim_value, "sanity"); 2572 assert(chr->humongous_start_region() == r, "sanity"); 2573 2574 if (chr->claimHeapRegion(claim_value)) { 2575 // we should always be able to claim it; noone else should 2576 // be trying to claim this region 2577 2578 bool res2 = cl->doHeapRegion(chr); 2579 assert(!res2, "Should not abort"); 2580 2581 // Right now, this holds (i.e., no closure that actually 2582 // does something with "continues humongous" regions 2583 // clears them). We might have to weaken it in the future, 2584 // but let's leave these two asserts here for extra safety. 2585 assert(chr->continuesHumongous(), "should still be the case"); 2586 assert(chr->humongous_start_region() == r, "sanity"); 2587 } else { 2588 guarantee(false, "we should not reach here"); 2589 } 2590 } 2591 } 2592 2593 assert(!r->continuesHumongous(), "sanity"); 2594 bool res = cl->doHeapRegion(r); 2595 assert(!res, "Should not abort"); 2596 } 2597 } 2598 } 2599 2600 class ResetClaimValuesClosure: public HeapRegionClosure { 2601 public: 2602 bool doHeapRegion(HeapRegion* r) { 2603 r->set_claim_value(HeapRegion::InitialClaimValue); 2604 return false; 2605 } 2606 }; 2607 2608 void 2609 G1CollectedHeap::reset_heap_region_claim_values() { 2610 ResetClaimValuesClosure blk; 2611 heap_region_iterate(&blk); 2612 } 2613 2614 #ifdef ASSERT 2615 // This checks whether all regions in the heap have the correct claim 2616 // value. I also piggy-backed on this a check to ensure that the 2617 // humongous_start_region() information on "continues humongous" 2618 // regions is correct. 2619 2620 class CheckClaimValuesClosure : public HeapRegionClosure { 2621 private: 2622 jint _claim_value; 2623 size_t _failures; 2624 HeapRegion* _sh_region; 2625 public: 2626 CheckClaimValuesClosure(jint claim_value) : 2627 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2628 bool doHeapRegion(HeapRegion* r) { 2629 if (r->claim_value() != _claim_value) { 2630 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2631 "claim value = %d, should be %d", 2632 HR_FORMAT_PARAMS(r), 2633 r->claim_value(), _claim_value); 2634 ++_failures; 2635 } 2636 if (!r->isHumongous()) { 2637 _sh_region = NULL; 2638 } else if (r->startsHumongous()) { 2639 _sh_region = r; 2640 } else if (r->continuesHumongous()) { 2641 if (r->humongous_start_region() != _sh_region) { 2642 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2643 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2644 HR_FORMAT_PARAMS(r), 2645 r->humongous_start_region(), 2646 _sh_region); 2647 ++_failures; 2648 } 2649 } 2650 return false; 2651 } 2652 size_t failures() { 2653 return _failures; 2654 } 2655 }; 2656 2657 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2658 CheckClaimValuesClosure cl(claim_value); 2659 heap_region_iterate(&cl); 2660 return cl.failures() == 0; 2661 } 2662 2663 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2664 jint _claim_value; 2665 size_t _failures; 2666 2667 public: 2668 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2669 _claim_value(claim_value), 2670 _failures(0) { } 2671 2672 size_t failures() { 2673 return _failures; 2674 } 2675 2676 bool doHeapRegion(HeapRegion* hr) { 2677 assert(hr->in_collection_set(), "how?"); 2678 assert(!hr->isHumongous(), "H-region in CSet"); 2679 if (hr->claim_value() != _claim_value) { 2680 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2681 "claim value = %d, should be %d", 2682 HR_FORMAT_PARAMS(hr), 2683 hr->claim_value(), _claim_value); 2684 _failures += 1; 2685 } 2686 return false; 2687 } 2688 }; 2689 2690 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2691 CheckClaimValuesInCSetHRClosure cl(claim_value); 2692 collection_set_iterate(&cl); 2693 return cl.failures() == 0; 2694 } 2695 #endif // ASSERT 2696 2697 // Clear the cached CSet starting regions and (more importantly) 2698 // the time stamps. Called when we reset the GC time stamp. 2699 void G1CollectedHeap::clear_cset_start_regions() { 2700 assert(_worker_cset_start_region != NULL, "sanity"); 2701 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2702 2703 int n_queues = MAX2((int)ParallelGCThreads, 1); 2704 for (int i = 0; i < n_queues; i++) { 2705 _worker_cset_start_region[i] = NULL; 2706 _worker_cset_start_region_time_stamp[i] = 0; 2707 } 2708 } 2709 2710 // Given the id of a worker, obtain or calculate a suitable 2711 // starting region for iterating over the current collection set. 2712 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) { 2713 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2714 2715 HeapRegion* result = NULL; 2716 unsigned gc_time_stamp = get_gc_time_stamp(); 2717 2718 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2719 // Cached starting region for current worker was set 2720 // during the current pause - so it's valid. 2721 // Note: the cached starting heap region may be NULL 2722 // (when the collection set is empty). 2723 result = _worker_cset_start_region[worker_i]; 2724 assert(result == NULL || result->in_collection_set(), "sanity"); 2725 return result; 2726 } 2727 2728 // The cached entry was not valid so let's calculate 2729 // a suitable starting heap region for this worker. 2730 2731 // We want the parallel threads to start their collection 2732 // set iteration at different collection set regions to 2733 // avoid contention. 2734 // If we have: 2735 // n collection set regions 2736 // p threads 2737 // Then thread t will start at region floor ((t * n) / p) 2738 2739 result = g1_policy()->collection_set(); 2740 if (G1CollectedHeap::use_parallel_gc_threads()) { 2741 size_t cs_size = g1_policy()->cset_region_length(); 2742 int active_workers = workers()->active_workers(); 2743 assert(UseDynamicNumberOfGCThreads || 2744 active_workers == workers()->total_workers(), 2745 "Unless dynamic should use total workers"); 2746 2747 size_t end_ind = (cs_size * worker_i) / active_workers; 2748 size_t start_ind = 0; 2749 2750 if (worker_i > 0 && 2751 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2752 // Previous workers starting region is valid 2753 // so let's iterate from there 2754 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2755 result = _worker_cset_start_region[worker_i - 1]; 2756 } 2757 2758 for (size_t i = start_ind; i < end_ind; i++) { 2759 result = result->next_in_collection_set(); 2760 } 2761 } 2762 2763 // Note: the calculated starting heap region may be NULL 2764 // (when the collection set is empty). 2765 assert(result == NULL || result->in_collection_set(), "sanity"); 2766 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2767 "should be updated only once per pause"); 2768 _worker_cset_start_region[worker_i] = result; 2769 OrderAccess::storestore(); 2770 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2771 return result; 2772 } 2773 2774 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2775 HeapRegion* r = g1_policy()->collection_set(); 2776 while (r != NULL) { 2777 HeapRegion* next = r->next_in_collection_set(); 2778 if (cl->doHeapRegion(r)) { 2779 cl->incomplete(); 2780 return; 2781 } 2782 r = next; 2783 } 2784 } 2785 2786 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2787 HeapRegionClosure *cl) { 2788 if (r == NULL) { 2789 // The CSet is empty so there's nothing to do. 2790 return; 2791 } 2792 2793 assert(r->in_collection_set(), 2794 "Start region must be a member of the collection set."); 2795 HeapRegion* cur = r; 2796 while (cur != NULL) { 2797 HeapRegion* next = cur->next_in_collection_set(); 2798 if (cl->doHeapRegion(cur) && false) { 2799 cl->incomplete(); 2800 return; 2801 } 2802 cur = next; 2803 } 2804 cur = g1_policy()->collection_set(); 2805 while (cur != r) { 2806 HeapRegion* next = cur->next_in_collection_set(); 2807 if (cl->doHeapRegion(cur) && false) { 2808 cl->incomplete(); 2809 return; 2810 } 2811 cur = next; 2812 } 2813 } 2814 2815 CompactibleSpace* G1CollectedHeap::first_compactible_space() { 2816 return n_regions() > 0 ? region_at(0) : NULL; 2817 } 2818 2819 2820 Space* G1CollectedHeap::space_containing(const void* addr) const { 2821 Space* res = heap_region_containing(addr); 2822 if (res == NULL) 2823 res = perm_gen()->space_containing(addr); 2824 return res; 2825 } 2826 2827 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2828 Space* sp = space_containing(addr); 2829 if (sp != NULL) { 2830 return sp->block_start(addr); 2831 } 2832 return NULL; 2833 } 2834 2835 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2836 Space* sp = space_containing(addr); 2837 assert(sp != NULL, "block_size of address outside of heap"); 2838 return sp->block_size(addr); 2839 } 2840 2841 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2842 Space* sp = space_containing(addr); 2843 return sp->block_is_obj(addr); 2844 } 2845 2846 bool G1CollectedHeap::supports_tlab_allocation() const { 2847 return true; 2848 } 2849 2850 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2851 return HeapRegion::GrainBytes; 2852 } 2853 2854 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2855 // Return the remaining space in the cur alloc region, but not less than 2856 // the min TLAB size. 2857 2858 // Also, this value can be at most the humongous object threshold, 2859 // since we can't allow tlabs to grow big enough to accomodate 2860 // humongous objects. 2861 2862 HeapRegion* hr = _mutator_alloc_region.get(); 2863 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize; 2864 if (hr == NULL) { 2865 return max_tlab_size; 2866 } else { 2867 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size); 2868 } 2869 } 2870 2871 size_t G1CollectedHeap::max_capacity() const { 2872 return _g1_reserved.byte_size(); 2873 } 2874 2875 jlong G1CollectedHeap::millis_since_last_gc() { 2876 // assert(false, "NYI"); 2877 return 0; 2878 } 2879 2880 void G1CollectedHeap::prepare_for_verify() { 2881 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2882 ensure_parsability(false); 2883 } 2884 g1_rem_set()->prepare_for_verify(); 2885 } 2886 2887 class VerifyLivenessOopClosure: public OopClosure { 2888 G1CollectedHeap* _g1h; 2889 VerifyOption _vo; 2890 public: 2891 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2892 _g1h(g1h), _vo(vo) 2893 { } 2894 void do_oop(narrowOop *p) { do_oop_work(p); } 2895 void do_oop( oop *p) { do_oop_work(p); } 2896 2897 template <class T> void do_oop_work(T *p) { 2898 oop obj = oopDesc::load_decode_heap_oop(p); 2899 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2900 "Dead object referenced by a not dead object"); 2901 } 2902 }; 2903 2904 class VerifyObjsInRegionClosure: public ObjectClosure { 2905 private: 2906 G1CollectedHeap* _g1h; 2907 size_t _live_bytes; 2908 HeapRegion *_hr; 2909 VerifyOption _vo; 2910 public: 2911 // _vo == UsePrevMarking -> use "prev" marking information, 2912 // _vo == UseNextMarking -> use "next" marking information, 2913 // _vo == UseMarkWord -> use mark word from object header. 2914 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2915 : _live_bytes(0), _hr(hr), _vo(vo) { 2916 _g1h = G1CollectedHeap::heap(); 2917 } 2918 void do_object(oop o) { 2919 VerifyLivenessOopClosure isLive(_g1h, _vo); 2920 assert(o != NULL, "Huh?"); 2921 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2922 // If the object is alive according to the mark word, 2923 // then verify that the marking information agrees. 2924 // Note we can't verify the contra-positive of the 2925 // above: if the object is dead (according to the mark 2926 // word), it may not be marked, or may have been marked 2927 // but has since became dead, or may have been allocated 2928 // since the last marking. 2929 if (_vo == VerifyOption_G1UseMarkWord) { 2930 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2931 } 2932 2933 o->oop_iterate(&isLive); 2934 if (!_hr->obj_allocated_since_prev_marking(o)) { 2935 size_t obj_size = o->size(); // Make sure we don't overflow 2936 _live_bytes += (obj_size * HeapWordSize); 2937 } 2938 } 2939 } 2940 size_t live_bytes() { return _live_bytes; } 2941 }; 2942 2943 class PrintObjsInRegionClosure : public ObjectClosure { 2944 HeapRegion *_hr; 2945 G1CollectedHeap *_g1; 2946 public: 2947 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 2948 _g1 = G1CollectedHeap::heap(); 2949 }; 2950 2951 void do_object(oop o) { 2952 if (o != NULL) { 2953 HeapWord *start = (HeapWord *) o; 2954 size_t word_sz = o->size(); 2955 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 2956 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 2957 (void*) o, word_sz, 2958 _g1->isMarkedPrev(o), 2959 _g1->isMarkedNext(o), 2960 _hr->obj_allocated_since_prev_marking(o)); 2961 HeapWord *end = start + word_sz; 2962 HeapWord *cur; 2963 int *val; 2964 for (cur = start; cur < end; cur++) { 2965 val = (int *) cur; 2966 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 2967 } 2968 } 2969 } 2970 }; 2971 2972 class VerifyRegionClosure: public HeapRegionClosure { 2973 private: 2974 bool _allow_dirty; 2975 bool _par; 2976 VerifyOption _vo; 2977 bool _failures; 2978 public: 2979 // _vo == UsePrevMarking -> use "prev" marking information, 2980 // _vo == UseNextMarking -> use "next" marking information, 2981 // _vo == UseMarkWord -> use mark word from object header. 2982 VerifyRegionClosure(bool allow_dirty, bool par, VerifyOption vo) 2983 : _allow_dirty(allow_dirty), 2984 _par(par), 2985 _vo(vo), 2986 _failures(false) {} 2987 2988 bool failures() { 2989 return _failures; 2990 } 2991 2992 bool doHeapRegion(HeapRegion* r) { 2993 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue, 2994 "Should be unclaimed at verify points."); 2995 if (!r->continuesHumongous()) { 2996 bool failures = false; 2997 r->verify(_allow_dirty, _vo, &failures); 2998 if (failures) { 2999 _failures = true; 3000 } else { 3001 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3002 r->object_iterate(¬_dead_yet_cl); 3003 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3004 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3005 "max_live_bytes "SIZE_FORMAT" " 3006 "< calculated "SIZE_FORMAT, 3007 r->bottom(), r->end(), 3008 r->max_live_bytes(), 3009 not_dead_yet_cl.live_bytes()); 3010 _failures = true; 3011 } 3012 } 3013 } 3014 return false; // stop the region iteration if we hit a failure 3015 } 3016 }; 3017 3018 class VerifyRootsClosure: public OopsInGenClosure { 3019 private: 3020 G1CollectedHeap* _g1h; 3021 VerifyOption _vo; 3022 bool _failures; 3023 public: 3024 // _vo == UsePrevMarking -> use "prev" marking information, 3025 // _vo == UseNextMarking -> use "next" marking information, 3026 // _vo == UseMarkWord -> use mark word from object header. 3027 VerifyRootsClosure(VerifyOption vo) : 3028 _g1h(G1CollectedHeap::heap()), 3029 _vo(vo), 3030 _failures(false) { } 3031 3032 bool failures() { return _failures; } 3033 3034 template <class T> void do_oop_nv(T* p) { 3035 T heap_oop = oopDesc::load_heap_oop(p); 3036 if (!oopDesc::is_null(heap_oop)) { 3037 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3038 if (_g1h->is_obj_dead_cond(obj, _vo)) { 3039 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 3040 "points to dead obj "PTR_FORMAT, p, (void*) obj); 3041 if (_vo == VerifyOption_G1UseMarkWord) { 3042 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 3043 } 3044 obj->print_on(gclog_or_tty); 3045 _failures = true; 3046 } 3047 } 3048 } 3049 3050 void do_oop(oop* p) { do_oop_nv(p); } 3051 void do_oop(narrowOop* p) { do_oop_nv(p); } 3052 }; 3053 3054 // This is the task used for parallel heap verification. 3055 3056 class G1ParVerifyTask: public AbstractGangTask { 3057 private: 3058 G1CollectedHeap* _g1h; 3059 bool _allow_dirty; 3060 VerifyOption _vo; 3061 bool _failures; 3062 3063 public: 3064 // _vo == UsePrevMarking -> use "prev" marking information, 3065 // _vo == UseNextMarking -> use "next" marking information, 3066 // _vo == UseMarkWord -> use mark word from object header. 3067 G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty, VerifyOption vo) : 3068 AbstractGangTask("Parallel verify task"), 3069 _g1h(g1h), 3070 _allow_dirty(allow_dirty), 3071 _vo(vo), 3072 _failures(false) { } 3073 3074 bool failures() { 3075 return _failures; 3076 } 3077 3078 void work(int worker_i) { 3079 HandleMark hm; 3080 VerifyRegionClosure blk(_allow_dirty, true, _vo); 3081 _g1h->heap_region_par_iterate_chunked(&blk, worker_i, 3082 _g1h->workers()->active_workers(), 3083 HeapRegion::ParVerifyClaimValue); 3084 if (blk.failures()) { 3085 _failures = true; 3086 } 3087 } 3088 }; 3089 3090 void G1CollectedHeap::verify(bool allow_dirty, bool silent) { 3091 verify(allow_dirty, silent, VerifyOption_G1UsePrevMarking); 3092 } 3093 3094 void G1CollectedHeap::verify(bool allow_dirty, 3095 bool silent, 3096 VerifyOption vo) { 3097 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 3098 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); } 3099 VerifyRootsClosure rootsCl(vo); 3100 3101 assert(Thread::current()->is_VM_thread(), 3102 "Expected to be executed serially by the VM thread at this point"); 3103 3104 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false); 3105 3106 // We apply the relevant closures to all the oops in the 3107 // system dictionary, the string table and the code cache. 3108 const int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; 3109 3110 process_strong_roots(true, // activate StrongRootsScope 3111 true, // we set "collecting perm gen" to true, 3112 // so we don't reset the dirty cards in the perm gen. 3113 SharedHeap::ScanningOption(so), // roots scanning options 3114 &rootsCl, 3115 &blobsCl, 3116 &rootsCl); 3117 3118 // If we're verifying after the marking phase of a Full GC then we can't 3119 // treat the perm gen as roots into the G1 heap. Some of the objects in 3120 // the perm gen may be dead and hence not marked. If one of these dead 3121 // objects is considered to be a root then we may end up with a false 3122 // "Root location <x> points to dead ob <y>" failure. 3123 if (vo != VerifyOption_G1UseMarkWord) { 3124 // Since we used "collecting_perm_gen" == true above, we will not have 3125 // checked the refs from perm into the G1-collected heap. We check those 3126 // references explicitly below. Whether the relevant cards are dirty 3127 // is checked further below in the rem set verification. 3128 if (!silent) { gclog_or_tty->print("Permgen roots "); } 3129 perm_gen()->oop_iterate(&rootsCl); 3130 } 3131 bool failures = rootsCl.failures(); 3132 3133 if (vo != VerifyOption_G1UseMarkWord) { 3134 // If we're verifying during a full GC then the region sets 3135 // will have been torn down at the start of the GC. Therefore 3136 // verifying the region sets will fail. So we only verify 3137 // the region sets when not in a full GC. 3138 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3139 verify_region_sets(); 3140 } 3141 3142 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3143 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3144 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3145 "sanity check"); 3146 3147 G1ParVerifyTask task(this, allow_dirty, vo); 3148 assert(UseDynamicNumberOfGCThreads || 3149 workers()->active_workers() == workers()->total_workers(), 3150 "If not dynamic should be using all the workers"); 3151 int n_workers = workers()->active_workers(); 3152 set_par_threads(n_workers); 3153 workers()->run_task(&task); 3154 set_par_threads(0); 3155 if (task.failures()) { 3156 failures = true; 3157 } 3158 3159 // Checks that the expected amount of parallel work was done. 3160 // The implication is that n_workers is > 0. 3161 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3162 "sanity check"); 3163 3164 reset_heap_region_claim_values(); 3165 3166 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3167 "sanity check"); 3168 } else { 3169 VerifyRegionClosure blk(allow_dirty, false, vo); 3170 heap_region_iterate(&blk); 3171 if (blk.failures()) { 3172 failures = true; 3173 } 3174 } 3175 if (!silent) gclog_or_tty->print("RemSet "); 3176 rem_set()->verify(); 3177 3178 if (failures) { 3179 gclog_or_tty->print_cr("Heap:"); 3180 // It helps to have the per-region information in the output to 3181 // help us track down what went wrong. This is why we call 3182 // print_extended_on() instead of print_on(). 3183 print_extended_on(gclog_or_tty); 3184 gclog_or_tty->print_cr(""); 3185 #ifndef PRODUCT 3186 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3187 concurrent_mark()->print_reachable("at-verification-failure", 3188 vo, false /* all */); 3189 } 3190 #endif 3191 gclog_or_tty->flush(); 3192 } 3193 guarantee(!failures, "there should not have been any failures"); 3194 } else { 3195 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) "); 3196 } 3197 } 3198 3199 class PrintRegionClosure: public HeapRegionClosure { 3200 outputStream* _st; 3201 public: 3202 PrintRegionClosure(outputStream* st) : _st(st) {} 3203 bool doHeapRegion(HeapRegion* r) { 3204 r->print_on(_st); 3205 return false; 3206 } 3207 }; 3208 3209 void G1CollectedHeap::print_on(outputStream* st) const { 3210 st->print(" %-20s", "garbage-first heap"); 3211 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3212 capacity()/K, used_unlocked()/K); 3213 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3214 _g1_storage.low_boundary(), 3215 _g1_storage.high(), 3216 _g1_storage.high_boundary()); 3217 st->cr(); 3218 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3219 size_t young_regions = _young_list->length(); 3220 st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ", 3221 young_regions, young_regions * HeapRegion::GrainBytes / K); 3222 size_t survivor_regions = g1_policy()->recorded_survivor_regions(); 3223 st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)", 3224 survivor_regions, survivor_regions * HeapRegion::GrainBytes / K); 3225 st->cr(); 3226 perm()->as_gen()->print_on(st); 3227 } 3228 3229 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3230 print_on(st); 3231 3232 // Print the per-region information. 3233 st->cr(); 3234 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), HS=humongous(starts), HC=humongous(continues), CS=collection set, F=free, TS=gc time stamp, PTAMS=previous top-at-mark-start, NTAMS=next top-at-mark-start)"); 3235 PrintRegionClosure blk(st); 3236 heap_region_iterate(&blk); 3237 } 3238 3239 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3240 if (G1CollectedHeap::use_parallel_gc_threads()) { 3241 workers()->print_worker_threads_on(st); 3242 } 3243 _cmThread->print_on(st); 3244 st->cr(); 3245 _cm->print_worker_threads_on(st); 3246 _cg1r->print_worker_threads_on(st); 3247 st->cr(); 3248 } 3249 3250 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3251 if (G1CollectedHeap::use_parallel_gc_threads()) { 3252 workers()->threads_do(tc); 3253 } 3254 tc->do_thread(_cmThread); 3255 _cg1r->threads_do(tc); 3256 } 3257 3258 void G1CollectedHeap::print_tracing_info() const { 3259 // We'll overload this to mean "trace GC pause statistics." 3260 if (TraceGen0Time || TraceGen1Time) { 3261 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3262 // to that. 3263 g1_policy()->print_tracing_info(); 3264 } 3265 if (G1SummarizeRSetStats) { 3266 g1_rem_set()->print_summary_info(); 3267 } 3268 if (G1SummarizeConcMark) { 3269 concurrent_mark()->print_summary_info(); 3270 } 3271 g1_policy()->print_yg_surv_rate_info(); 3272 SpecializationStats::print(); 3273 } 3274 3275 #ifndef PRODUCT 3276 // Helpful for debugging RSet issues. 3277 3278 class PrintRSetsClosure : public HeapRegionClosure { 3279 private: 3280 const char* _msg; 3281 size_t _occupied_sum; 3282 3283 public: 3284 bool doHeapRegion(HeapRegion* r) { 3285 HeapRegionRemSet* hrrs = r->rem_set(); 3286 size_t occupied = hrrs->occupied(); 3287 _occupied_sum += occupied; 3288 3289 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3290 HR_FORMAT_PARAMS(r)); 3291 if (occupied == 0) { 3292 gclog_or_tty->print_cr(" RSet is empty"); 3293 } else { 3294 hrrs->print(); 3295 } 3296 gclog_or_tty->print_cr("----------"); 3297 return false; 3298 } 3299 3300 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3301 gclog_or_tty->cr(); 3302 gclog_or_tty->print_cr("========================================"); 3303 gclog_or_tty->print_cr(msg); 3304 gclog_or_tty->cr(); 3305 } 3306 3307 ~PrintRSetsClosure() { 3308 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3309 gclog_or_tty->print_cr("========================================"); 3310 gclog_or_tty->cr(); 3311 } 3312 }; 3313 3314 void G1CollectedHeap::print_cset_rsets() { 3315 PrintRSetsClosure cl("Printing CSet RSets"); 3316 collection_set_iterate(&cl); 3317 } 3318 3319 void G1CollectedHeap::print_all_rsets() { 3320 PrintRSetsClosure cl("Printing All RSets");; 3321 heap_region_iterate(&cl); 3322 } 3323 #endif // PRODUCT 3324 3325 G1CollectedHeap* G1CollectedHeap::heap() { 3326 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3327 "not a garbage-first heap"); 3328 return _g1h; 3329 } 3330 3331 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3332 // always_do_update_barrier = false; 3333 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3334 // Call allocation profiler 3335 AllocationProfiler::iterate_since_last_gc(); 3336 // Fill TLAB's and such 3337 ensure_parsability(true); 3338 } 3339 3340 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { 3341 // FIXME: what is this about? 3342 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3343 // is set. 3344 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3345 "derived pointer present")); 3346 // always_do_update_barrier = true; 3347 3348 // We have just completed a GC. Update the soft reference 3349 // policy with the new heap occupancy 3350 Universe::update_heap_info_at_gc(); 3351 } 3352 3353 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3354 unsigned int gc_count_before, 3355 bool* succeeded) { 3356 assert_heap_not_locked_and_not_at_safepoint(); 3357 g1_policy()->record_stop_world_start(); 3358 VM_G1IncCollectionPause op(gc_count_before, 3359 word_size, 3360 false, /* should_initiate_conc_mark */ 3361 g1_policy()->max_pause_time_ms(), 3362 GCCause::_g1_inc_collection_pause); 3363 VMThread::execute(&op); 3364 3365 HeapWord* result = op.result(); 3366 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3367 assert(result == NULL || ret_succeeded, 3368 "the result should be NULL if the VM did not succeed"); 3369 *succeeded = ret_succeeded; 3370 3371 assert_heap_not_locked(); 3372 return result; 3373 } 3374 3375 void 3376 G1CollectedHeap::doConcurrentMark() { 3377 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3378 if (!_cmThread->in_progress()) { 3379 _cmThread->set_started(); 3380 CGC_lock->notify(); 3381 } 3382 } 3383 3384 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr, 3385 bool young) { 3386 return _g1_policy->predict_region_elapsed_time_ms(hr, young); 3387 } 3388 3389 void G1CollectedHeap::check_if_region_is_too_expensive(double 3390 predicted_time_ms) { 3391 _g1_policy->check_if_region_is_too_expensive(predicted_time_ms); 3392 } 3393 3394 size_t G1CollectedHeap::pending_card_num() { 3395 size_t extra_cards = 0; 3396 JavaThread *curr = Threads::first(); 3397 while (curr != NULL) { 3398 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3399 extra_cards += dcq.size(); 3400 curr = curr->next(); 3401 } 3402 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3403 size_t buffer_size = dcqs.buffer_size(); 3404 size_t buffer_num = dcqs.completed_buffers_num(); 3405 return buffer_size * buffer_num + extra_cards; 3406 } 3407 3408 size_t G1CollectedHeap::max_pending_card_num() { 3409 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3410 size_t buffer_size = dcqs.buffer_size(); 3411 size_t buffer_num = dcqs.completed_buffers_num(); 3412 int thread_num = Threads::number_of_threads(); 3413 return (buffer_num + thread_num) * buffer_size; 3414 } 3415 3416 size_t G1CollectedHeap::cards_scanned() { 3417 return g1_rem_set()->cardsScanned(); 3418 } 3419 3420 void 3421 G1CollectedHeap::setup_surviving_young_words() { 3422 guarantee( _surviving_young_words == NULL, "pre-condition" ); 3423 size_t array_length = g1_policy()->young_cset_region_length(); 3424 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length); 3425 if (_surviving_young_words == NULL) { 3426 vm_exit_out_of_memory(sizeof(size_t) * array_length, 3427 "Not enough space for young surv words summary."); 3428 } 3429 memset(_surviving_young_words, 0, array_length * sizeof(size_t)); 3430 #ifdef ASSERT 3431 for (size_t i = 0; i < array_length; ++i) { 3432 assert( _surviving_young_words[i] == 0, "memset above" ); 3433 } 3434 #endif // !ASSERT 3435 } 3436 3437 void 3438 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3439 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3440 size_t array_length = g1_policy()->young_cset_region_length(); 3441 for (size_t i = 0; i < array_length; ++i) 3442 _surviving_young_words[i] += surv_young_words[i]; 3443 } 3444 3445 void 3446 G1CollectedHeap::cleanup_surviving_young_words() { 3447 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3448 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words); 3449 _surviving_young_words = NULL; 3450 } 3451 3452 #ifdef ASSERT 3453 class VerifyCSetClosure: public HeapRegionClosure { 3454 public: 3455 bool doHeapRegion(HeapRegion* hr) { 3456 // Here we check that the CSet region's RSet is ready for parallel 3457 // iteration. The fields that we'll verify are only manipulated 3458 // when the region is part of a CSet and is collected. Afterwards, 3459 // we reset these fields when we clear the region's RSet (when the 3460 // region is freed) so they are ready when the region is 3461 // re-allocated. The only exception to this is if there's an 3462 // evacuation failure and instead of freeing the region we leave 3463 // it in the heap. In that case, we reset these fields during 3464 // evacuation failure handling. 3465 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3466 3467 // Here's a good place to add any other checks we'd like to 3468 // perform on CSet regions. 3469 return false; 3470 } 3471 }; 3472 #endif // ASSERT 3473 3474 #if TASKQUEUE_STATS 3475 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3476 st->print_raw_cr("GC Task Stats"); 3477 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3478 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3479 } 3480 3481 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3482 print_taskqueue_stats_hdr(st); 3483 3484 TaskQueueStats totals; 3485 const int n = workers() != NULL ? workers()->total_workers() : 1; 3486 for (int i = 0; i < n; ++i) { 3487 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3488 totals += task_queue(i)->stats; 3489 } 3490 st->print_raw("tot "); totals.print(st); st->cr(); 3491 3492 DEBUG_ONLY(totals.verify()); 3493 } 3494 3495 void G1CollectedHeap::reset_taskqueue_stats() { 3496 const int n = workers() != NULL ? workers()->total_workers() : 1; 3497 for (int i = 0; i < n; ++i) { 3498 task_queue(i)->stats.reset(); 3499 } 3500 } 3501 #endif // TASKQUEUE_STATS 3502 3503 bool 3504 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3505 assert_at_safepoint(true /* should_be_vm_thread */); 3506 guarantee(!is_gc_active(), "collection is not reentrant"); 3507 3508 if (GC_locker::check_active_before_gc()) { 3509 return false; 3510 } 3511 3512 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3513 ResourceMark rm; 3514 3515 if (PrintHeapAtGC) { 3516 Universe::print_heap_before_gc(); 3517 } 3518 3519 HRSPhaseSetter x(HRSPhaseEvacuation); 3520 verify_region_sets_optional(); 3521 verify_dirty_young_regions(); 3522 3523 { 3524 // This call will decide whether this pause is an initial-mark 3525 // pause. If it is, during_initial_mark_pause() will return true 3526 // for the duration of this pause. 3527 g1_policy()->decide_on_conc_mark_initiation(); 3528 3529 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3530 assert(!g1_policy()->during_initial_mark_pause() || 3531 g1_policy()->gcs_are_young(), "sanity"); 3532 3533 // We also do not allow mixed GCs during marking. 3534 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3535 3536 char verbose_str[128]; 3537 sprintf(verbose_str, "GC pause "); 3538 if (g1_policy()->gcs_are_young()) { 3539 strcat(verbose_str, "(young)"); 3540 } else { 3541 strcat(verbose_str, "(mixed)"); 3542 } 3543 if (g1_policy()->during_initial_mark_pause()) { 3544 strcat(verbose_str, " (initial-mark)"); 3545 // We are about to start a marking cycle, so we increment the 3546 // full collection counter. 3547 increment_total_full_collections(); 3548 } 3549 3550 // if PrintGCDetails is on, we'll print long statistics information 3551 // in the collector policy code, so let's not print this as the output 3552 // is messy if we do. 3553 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 3554 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 3555 TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty); 3556 3557 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3558 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3559 3560 // If the secondary_free_list is not empty, append it to the 3561 // free_list. No need to wait for the cleanup operation to finish; 3562 // the region allocation code will check the secondary_free_list 3563 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3564 // set, skip this step so that the region allocation code has to 3565 // get entries from the secondary_free_list. 3566 if (!G1StressConcRegionFreeing) { 3567 append_secondary_free_list_if_not_empty_with_lock(); 3568 } 3569 3570 assert(check_young_list_well_formed(), 3571 "young list should be well formed"); 3572 3573 // Don't dynamically change the number of GC threads this early. A value of 3574 // 0 is used to indicate serial work. When parallel work is done, 3575 // it will be set. 3576 3577 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3578 IsGCActiveMark x; 3579 3580 gc_prologue(false); 3581 increment_total_collections(false /* full gc */); 3582 increment_gc_time_stamp(); 3583 3584 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) { 3585 HandleMark hm; // Discard invalid handles created during verification 3586 gclog_or_tty->print(" VerifyBeforeGC:"); 3587 prepare_for_verify(); 3588 Universe::verify(/* allow dirty */ false, 3589 /* silent */ false, 3590 /* option */ VerifyOption_G1UsePrevMarking); 3591 3592 } 3593 3594 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3595 3596 // Please see comment in g1CollectedHeap.hpp and 3597 // G1CollectedHeap::ref_processing_init() to see how 3598 // reference processing currently works in G1. 3599 3600 // Enable discovery in the STW reference processor 3601 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 3602 true /*verify_no_refs*/); 3603 3604 { 3605 // We want to temporarily turn off discovery by the 3606 // CM ref processor, if necessary, and turn it back on 3607 // on again later if we do. Using a scoped 3608 // NoRefDiscovery object will do this. 3609 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3610 3611 // Forget the current alloc region (we might even choose it to be part 3612 // of the collection set!). 3613 release_mutator_alloc_region(); 3614 3615 // We should call this after we retire the mutator alloc 3616 // region(s) so that all the ALLOC / RETIRE events are generated 3617 // before the start GC event. 3618 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3619 3620 // The elapsed time induced by the start time below deliberately elides 3621 // the possible verification above. 3622 double start_time_sec = os::elapsedTime(); 3623 size_t start_used_bytes = used(); 3624 3625 #if YOUNG_LIST_VERBOSE 3626 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3627 _young_list->print(); 3628 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3629 #endif // YOUNG_LIST_VERBOSE 3630 3631 g1_policy()->record_collection_pause_start(start_time_sec, 3632 start_used_bytes); 3633 3634 #if YOUNG_LIST_VERBOSE 3635 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3636 _young_list->print(); 3637 #endif // YOUNG_LIST_VERBOSE 3638 3639 if (g1_policy()->during_initial_mark_pause()) { 3640 concurrent_mark()->checkpointRootsInitialPre(); 3641 } 3642 perm_gen()->save_marks(); 3643 3644 // We must do this before any possible evacuation that should propagate 3645 // marks. 3646 if (mark_in_progress()) { 3647 double start_time_sec = os::elapsedTime(); 3648 3649 _cm->drainAllSATBBuffers(); 3650 double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0; 3651 g1_policy()->record_satb_drain_time(finish_mark_ms); 3652 } 3653 // Record the number of elements currently on the mark stack, so we 3654 // only iterate over these. (Since evacuation may add to the mark 3655 // stack, doing more exposes race conditions.) If no mark is in 3656 // progress, this will be zero. 3657 _cm->set_oops_do_bound(); 3658 3659 if (mark_in_progress()) { 3660 concurrent_mark()->newCSet(); 3661 } 3662 3663 #if YOUNG_LIST_VERBOSE 3664 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3665 _young_list->print(); 3666 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3667 #endif // YOUNG_LIST_VERBOSE 3668 3669 g1_policy()->choose_collection_set(target_pause_time_ms); 3670 3671 if (_hr_printer.is_active()) { 3672 HeapRegion* hr = g1_policy()->collection_set(); 3673 while (hr != NULL) { 3674 G1HRPrinter::RegionType type; 3675 if (!hr->is_young()) { 3676 type = G1HRPrinter::Old; 3677 } else if (hr->is_survivor()) { 3678 type = G1HRPrinter::Survivor; 3679 } else { 3680 type = G1HRPrinter::Eden; 3681 } 3682 _hr_printer.cset(hr); 3683 hr = hr->next_in_collection_set(); 3684 } 3685 } 3686 3687 // We have chosen the complete collection set. If marking is 3688 // active then, we clear the region fields of any of the 3689 // concurrent marking tasks whose region fields point into 3690 // the collection set as these values will become stale. This 3691 // will cause the owning marking threads to claim a new region 3692 // when marking restarts. 3693 if (mark_in_progress()) { 3694 concurrent_mark()->reset_active_task_region_fields_in_cset(); 3695 } 3696 3697 #ifdef ASSERT 3698 VerifyCSetClosure cl; 3699 collection_set_iterate(&cl); 3700 #endif // ASSERT 3701 3702 setup_surviving_young_words(); 3703 3704 // Initialize the GC alloc regions. 3705 init_gc_alloc_regions(); 3706 3707 // Actually do the work... 3708 evacuate_collection_set(); 3709 3710 free_collection_set(g1_policy()->collection_set()); 3711 g1_policy()->clear_collection_set(); 3712 3713 cleanup_surviving_young_words(); 3714 3715 // Start a new incremental collection set for the next pause. 3716 g1_policy()->start_incremental_cset_building(); 3717 3718 // Clear the _cset_fast_test bitmap in anticipation of adding 3719 // regions to the incremental collection set for the next 3720 // evacuation pause. 3721 clear_cset_fast_test(); 3722 3723 _young_list->reset_sampled_info(); 3724 3725 // Don't check the whole heap at this point as the 3726 // GC alloc regions from this pause have been tagged 3727 // as survivors and moved on to the survivor list. 3728 // Survivor regions will fail the !is_young() check. 3729 assert(check_young_list_empty(false /* check_heap */), 3730 "young list should be empty"); 3731 3732 #if YOUNG_LIST_VERBOSE 3733 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3734 _young_list->print(); 3735 #endif // YOUNG_LIST_VERBOSE 3736 3737 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3738 _young_list->first_survivor_region(), 3739 _young_list->last_survivor_region()); 3740 3741 _young_list->reset_auxilary_lists(); 3742 3743 if (evacuation_failed()) { 3744 _summary_bytes_used = recalculate_used(); 3745 } else { 3746 // The "used" of the the collection set have already been subtracted 3747 // when they were freed. Add in the bytes evacuated. 3748 _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); 3749 } 3750 3751 if (g1_policy()->during_initial_mark_pause()) { 3752 concurrent_mark()->checkpointRootsInitialPost(); 3753 set_marking_started(); 3754 // CAUTION: after the doConcurrentMark() call below, 3755 // the concurrent marking thread(s) could be running 3756 // concurrently with us. Make sure that anything after 3757 // this point does not assume that we are the only GC thread 3758 // running. Note: of course, the actual marking work will 3759 // not start until the safepoint itself is released in 3760 // ConcurrentGCThread::safepoint_desynchronize(). 3761 doConcurrentMark(); 3762 } 3763 3764 allocate_dummy_regions(); 3765 3766 #if YOUNG_LIST_VERBOSE 3767 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 3768 _young_list->print(); 3769 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3770 #endif // YOUNG_LIST_VERBOSE 3771 3772 init_mutator_alloc_region(); 3773 3774 { 3775 size_t expand_bytes = g1_policy()->expansion_amount(); 3776 if (expand_bytes > 0) { 3777 size_t bytes_before = capacity(); 3778 if (!expand(expand_bytes)) { 3779 // We failed to expand the heap so let's verify that 3780 // committed/uncommitted amount match the backing store 3781 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 3782 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 3783 } 3784 } 3785 } 3786 3787 double end_time_sec = os::elapsedTime(); 3788 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS; 3789 g1_policy()->record_pause_time_ms(pause_time_ms); 3790 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3791 workers()->active_workers() : 1); 3792 g1_policy()->record_collection_pause_end(active_workers); 3793 3794 MemoryService::track_memory_usage(); 3795 3796 // In prepare_for_verify() below we'll need to scan the deferred 3797 // update buffers to bring the RSets up-to-date if 3798 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3799 // the update buffers we'll probably need to scan cards on the 3800 // regions we just allocated to (i.e., the GC alloc 3801 // regions). However, during the last GC we called 3802 // set_saved_mark() on all the GC alloc regions, so card 3803 // scanning might skip the [saved_mark_word()...top()] area of 3804 // those regions (i.e., the area we allocated objects into 3805 // during the last GC). But it shouldn't. Given that 3806 // saved_mark_word() is conditional on whether the GC time stamp 3807 // on the region is current or not, by incrementing the GC time 3808 // stamp here we invalidate all the GC time stamps on all the 3809 // regions and saved_mark_word() will simply return top() for 3810 // all the regions. This is a nicer way of ensuring this rather 3811 // than iterating over the regions and fixing them. In fact, the 3812 // GC time stamp increment here also ensures that 3813 // saved_mark_word() will return top() between pauses, i.e., 3814 // during concurrent refinement. So we don't need the 3815 // is_gc_active() check to decided which top to use when 3816 // scanning cards (see CR 7039627). 3817 increment_gc_time_stamp(); 3818 3819 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) { 3820 HandleMark hm; // Discard invalid handles created during verification 3821 gclog_or_tty->print(" VerifyAfterGC:"); 3822 prepare_for_verify(); 3823 Universe::verify(/* allow dirty */ true, 3824 /* silent */ false, 3825 /* option */ VerifyOption_G1UsePrevMarking); 3826 } 3827 3828 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3829 ref_processor_stw()->verify_no_references_recorded(); 3830 3831 // CM reference discovery will be re-enabled if necessary. 3832 } 3833 3834 { 3835 size_t expand_bytes = g1_policy()->expansion_amount(); 3836 if (expand_bytes > 0) { 3837 size_t bytes_before = capacity(); 3838 // No need for an ergo verbose message here, 3839 // expansion_amount() does this when it returns a value > 0. 3840 if (!expand(expand_bytes)) { 3841 // We failed to expand the heap so let's verify that 3842 // committed/uncommitted amount match the backing store 3843 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 3844 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 3845 } 3846 } 3847 } 3848 3849 // We should do this after we potentially expand the heap so 3850 // that all the COMMIT events are generated before the end GC 3851 // event, and after we retire the GC alloc regions so that all 3852 // RETIRE events are generated before the end GC event. 3853 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 3854 3855 // We have to do this after we decide whether to expand the heap or not. 3856 g1_policy()->print_heap_transition(); 3857 3858 if (mark_in_progress()) { 3859 concurrent_mark()->update_g1_committed(); 3860 } 3861 3862 #ifdef TRACESPINNING 3863 ParallelTaskTerminator::print_termination_counts(); 3864 #endif 3865 3866 gc_epilogue(false); 3867 } 3868 3869 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) { 3870 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum); 3871 print_tracing_info(); 3872 vm_exit(-1); 3873 } 3874 } 3875 3876 _hrs.verify_optional(); 3877 verify_region_sets_optional(); 3878 3879 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 3880 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3881 3882 if (PrintHeapAtGC) { 3883 Universe::print_heap_after_gc(); 3884 } 3885 g1mm()->update_sizes(); 3886 3887 if (G1SummarizeRSetStats && 3888 (G1SummarizeRSetStatsPeriod > 0) && 3889 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3890 g1_rem_set()->print_summary_info(); 3891 } 3892 3893 return true; 3894 } 3895 3896 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 3897 { 3898 size_t gclab_word_size; 3899 switch (purpose) { 3900 case GCAllocForSurvived: 3901 gclab_word_size = YoungPLABSize; 3902 break; 3903 case GCAllocForTenured: 3904 gclab_word_size = OldPLABSize; 3905 break; 3906 default: 3907 assert(false, "unknown GCAllocPurpose"); 3908 gclab_word_size = OldPLABSize; 3909 break; 3910 } 3911 return gclab_word_size; 3912 } 3913 3914 void G1CollectedHeap::init_mutator_alloc_region() { 3915 assert(_mutator_alloc_region.get() == NULL, "pre-condition"); 3916 _mutator_alloc_region.init(); 3917 } 3918 3919 void G1CollectedHeap::release_mutator_alloc_region() { 3920 _mutator_alloc_region.release(); 3921 assert(_mutator_alloc_region.get() == NULL, "post-condition"); 3922 } 3923 3924 void G1CollectedHeap::init_gc_alloc_regions() { 3925 assert_at_safepoint(true /* should_be_vm_thread */); 3926 3927 _survivor_gc_alloc_region.init(); 3928 _old_gc_alloc_region.init(); 3929 HeapRegion* retained_region = _retained_old_gc_alloc_region; 3930 _retained_old_gc_alloc_region = NULL; 3931 3932 // We will discard the current GC alloc region if: 3933 // a) it's in the collection set (it can happen!), 3934 // b) it's already full (no point in using it), 3935 // c) it's empty (this means that it was emptied during 3936 // a cleanup and it should be on the free list now), or 3937 // d) it's humongous (this means that it was emptied 3938 // during a cleanup and was added to the free list, but 3939 // has been subseqently used to allocate a humongous 3940 // object that may be less than the region size). 3941 if (retained_region != NULL && 3942 !retained_region->in_collection_set() && 3943 !(retained_region->top() == retained_region->end()) && 3944 !retained_region->is_empty() && 3945 !retained_region->isHumongous()) { 3946 retained_region->set_saved_mark(); 3947 // The retained region was added to the old region set when it was 3948 // retired. We have to remove it now, since we don't allow regions 3949 // we allocate to in the region sets. We'll re-add it later, when 3950 // it's retired again. 3951 _old_set.remove(retained_region); 3952 _old_gc_alloc_region.set(retained_region); 3953 _hr_printer.reuse(retained_region); 3954 } 3955 } 3956 3957 void G1CollectedHeap::release_gc_alloc_regions() { 3958 _survivor_gc_alloc_region.release(); 3959 // If we have an old GC alloc region to release, we'll save it in 3960 // _retained_old_gc_alloc_region. If we don't 3961 // _retained_old_gc_alloc_region will become NULL. This is what we 3962 // want either way so no reason to check explicitly for either 3963 // condition. 3964 _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); 3965 } 3966 3967 void G1CollectedHeap::abandon_gc_alloc_regions() { 3968 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); 3969 assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); 3970 _retained_old_gc_alloc_region = NULL; 3971 } 3972 3973 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 3974 _drain_in_progress = false; 3975 set_evac_failure_closure(cl); 3976 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true); 3977 } 3978 3979 void G1CollectedHeap::finalize_for_evac_failure() { 3980 assert(_evac_failure_scan_stack != NULL && 3981 _evac_failure_scan_stack->length() == 0, 3982 "Postcondition"); 3983 assert(!_drain_in_progress, "Postcondition"); 3984 delete _evac_failure_scan_stack; 3985 _evac_failure_scan_stack = NULL; 3986 } 3987 3988 class UpdateRSetDeferred : public OopsInHeapRegionClosure { 3989 private: 3990 G1CollectedHeap* _g1; 3991 DirtyCardQueue *_dcq; 3992 CardTableModRefBS* _ct_bs; 3993 3994 public: 3995 UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) : 3996 _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {} 3997 3998 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3999 virtual void do_oop( oop* p) { do_oop_work(p); } 4000 template <class T> void do_oop_work(T* p) { 4001 assert(_from->is_in_reserved(p), "paranoia"); 4002 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && 4003 !_from->is_survivor()) { 4004 size_t card_index = _ct_bs->index_for(p); 4005 if (_ct_bs->mark_card_deferred(card_index)) { 4006 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index)); 4007 } 4008 } 4009 } 4010 }; 4011 4012 class RemoveSelfPointerClosure: public ObjectClosure { 4013 private: 4014 G1CollectedHeap* _g1; 4015 ConcurrentMark* _cm; 4016 HeapRegion* _hr; 4017 size_t _prev_marked_bytes; 4018 size_t _next_marked_bytes; 4019 OopsInHeapRegionClosure *_cl; 4020 public: 4021 RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr, 4022 OopsInHeapRegionClosure* cl) : 4023 _g1(g1), _hr(hr), _cm(_g1->concurrent_mark()), _prev_marked_bytes(0), 4024 _next_marked_bytes(0), _cl(cl) {} 4025 4026 size_t prev_marked_bytes() { return _prev_marked_bytes; } 4027 size_t next_marked_bytes() { return _next_marked_bytes; } 4028 4029 // <original comment> 4030 // The original idea here was to coalesce evacuated and dead objects. 4031 // However that caused complications with the block offset table (BOT). 4032 // In particular if there were two TLABs, one of them partially refined. 4033 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~| 4034 // The BOT entries of the unrefined part of TLAB_2 point to the start 4035 // of TLAB_2. If the last object of the TLAB_1 and the first object 4036 // of TLAB_2 are coalesced, then the cards of the unrefined part 4037 // would point into middle of the filler object. 4038 // The current approach is to not coalesce and leave the BOT contents intact. 4039 // </original comment> 4040 // 4041 // We now reset the BOT when we start the object iteration over the 4042 // region and refine its entries for every object we come across. So 4043 // the above comment is not really relevant and we should be able 4044 // to coalesce dead objects if we want to. 4045 void do_object(oop obj) { 4046 HeapWord* obj_addr = (HeapWord*) obj; 4047 assert(_hr->is_in(obj_addr), "sanity"); 4048 size_t obj_size = obj->size(); 4049 _hr->update_bot_for_object(obj_addr, obj_size); 4050 if (obj->is_forwarded() && obj->forwardee() == obj) { 4051 // The object failed to move. 4052 assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs."); 4053 _cm->markPrev(obj); 4054 assert(_cm->isPrevMarked(obj), "Should be marked!"); 4055 _prev_marked_bytes += (obj_size * HeapWordSize); 4056 if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) { 4057 _cm->markAndGrayObjectIfNecessary(obj); 4058 } 4059 obj->set_mark(markOopDesc::prototype()); 4060 // While we were processing RSet buffers during the 4061 // collection, we actually didn't scan any cards on the 4062 // collection set, since we didn't want to update remebered 4063 // sets with entries that point into the collection set, given 4064 // that live objects fromthe collection set are about to move 4065 // and such entries will be stale very soon. This change also 4066 // dealt with a reliability issue which involved scanning a 4067 // card in the collection set and coming across an array that 4068 // was being chunked and looking malformed. The problem is 4069 // that, if evacuation fails, we might have remembered set 4070 // entries missing given that we skipped cards on the 4071 // collection set. So, we'll recreate such entries now. 4072 obj->oop_iterate(_cl); 4073 assert(_cm->isPrevMarked(obj), "Should be marked!"); 4074 } else { 4075 // The object has been either evacuated or is dead. Fill it with a 4076 // dummy object. 4077 MemRegion mr((HeapWord*)obj, obj_size); 4078 CollectedHeap::fill_with_object(mr); 4079 _cm->clearRangeBothMaps(mr); 4080 } 4081 } 4082 }; 4083 4084 void G1CollectedHeap::remove_self_forwarding_pointers() { 4085 UpdateRSetImmediate immediate_update(_g1h->g1_rem_set()); 4086 DirtyCardQueue dcq(&_g1h->dirty_card_queue_set()); 4087 UpdateRSetDeferred deferred_update(_g1h, &dcq); 4088 OopsInHeapRegionClosure *cl; 4089 if (G1DeferredRSUpdate) { 4090 cl = &deferred_update; 4091 } else { 4092 cl = &immediate_update; 4093 } 4094 HeapRegion* cur = g1_policy()->collection_set(); 4095 while (cur != NULL) { 4096 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!"); 4097 assert(!cur->isHumongous(), "sanity"); 4098 4099 if (cur->evacuation_failed()) { 4100 assert(cur->in_collection_set(), "bad CS"); 4101 RemoveSelfPointerClosure rspc(_g1h, cur, cl); 4102 4103 // In the common case we make sure that this is done when the 4104 // region is freed so that it is "ready-to-go" when it's 4105 // re-allocated. However, when evacuation failure happens, a 4106 // region will remain in the heap and might ultimately be added 4107 // to a CSet in the future. So we have to be careful here and 4108 // make sure the region's RSet is ready for parallel iteration 4109 // whenever this might be required in the future. 4110 cur->rem_set()->reset_for_par_iteration(); 4111 cur->reset_bot(); 4112 cl->set_region(cur); 4113 cur->object_iterate(&rspc); 4114 4115 // A number of manipulations to make the TAMS be the current top, 4116 // and the marked bytes be the ones observed in the iteration. 4117 if (_g1h->concurrent_mark()->at_least_one_mark_complete()) { 4118 // The comments below are the postconditions achieved by the 4119 // calls. Note especially the last such condition, which says that 4120 // the count of marked bytes has been properly restored. 4121 cur->note_start_of_marking(false); 4122 // _next_top_at_mark_start == top, _next_marked_bytes == 0 4123 cur->add_to_marked_bytes(rspc.prev_marked_bytes()); 4124 // _next_marked_bytes == prev_marked_bytes. 4125 cur->note_end_of_marking(); 4126 // _prev_top_at_mark_start == top(), 4127 // _prev_marked_bytes == prev_marked_bytes 4128 } 4129 // If there is no mark in progress, we modified the _next variables 4130 // above needlessly, but harmlessly. 4131 if (_g1h->mark_in_progress()) { 4132 cur->note_start_of_marking(false); 4133 // _next_top_at_mark_start == top, _next_marked_bytes == 0 4134 // _next_marked_bytes == next_marked_bytes. 4135 } 4136 } 4137 cur = cur->next_in_collection_set(); 4138 } 4139 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!"); 4140 4141 // Now restore saved marks, if any. 4142 if (_objs_with_preserved_marks != NULL) { 4143 assert(_preserved_marks_of_objs != NULL, "Both or none."); 4144 guarantee(_objs_with_preserved_marks->length() == 4145 _preserved_marks_of_objs->length(), "Both or none."); 4146 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) { 4147 oop obj = _objs_with_preserved_marks->at(i); 4148 markOop m = _preserved_marks_of_objs->at(i); 4149 obj->set_mark(m); 4150 } 4151 // Delete the preserved marks growable arrays (allocated on the C heap). 4152 delete _objs_with_preserved_marks; 4153 delete _preserved_marks_of_objs; 4154 _objs_with_preserved_marks = NULL; 4155 _preserved_marks_of_objs = NULL; 4156 } 4157 } 4158 4159 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4160 _evac_failure_scan_stack->push(obj); 4161 } 4162 4163 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4164 assert(_evac_failure_scan_stack != NULL, "precondition"); 4165 4166 while (_evac_failure_scan_stack->length() > 0) { 4167 oop obj = _evac_failure_scan_stack->pop(); 4168 _evac_failure_closure->set_region(heap_region_containing(obj)); 4169 obj->oop_iterate_backwards(_evac_failure_closure); 4170 } 4171 } 4172 4173 oop 4174 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, 4175 oop old, 4176 bool should_mark_root) { 4177 assert(obj_in_cs(old), 4178 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4179 (HeapWord*) old)); 4180 markOop m = old->mark(); 4181 oop forward_ptr = old->forward_to_atomic(old); 4182 if (forward_ptr == NULL) { 4183 // Forward-to-self succeeded. 4184 4185 // should_mark_root will be true when this routine is called 4186 // from a root scanning closure during an initial mark pause. 4187 // In this case the thread that succeeds in self-forwarding the 4188 // object is also responsible for marking the object. 4189 if (should_mark_root) { 4190 assert(!oopDesc::is_null(old), "shouldn't be"); 4191 _cm->grayRoot(old); 4192 } 4193 4194 if (_evac_failure_closure != cl) { 4195 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4196 assert(!_drain_in_progress, 4197 "Should only be true while someone holds the lock."); 4198 // Set the global evac-failure closure to the current thread's. 4199 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4200 set_evac_failure_closure(cl); 4201 // Now do the common part. 4202 handle_evacuation_failure_common(old, m); 4203 // Reset to NULL. 4204 set_evac_failure_closure(NULL); 4205 } else { 4206 // The lock is already held, and this is recursive. 4207 assert(_drain_in_progress, "This should only be the recursive case."); 4208 handle_evacuation_failure_common(old, m); 4209 } 4210 return old; 4211 } else { 4212 // Forward-to-self failed. Either someone else managed to allocate 4213 // space for this object (old != forward_ptr) or they beat us in 4214 // self-forwarding it (old == forward_ptr). 4215 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4216 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4217 "should not be in the CSet", 4218 (HeapWord*) old, (HeapWord*) forward_ptr)); 4219 return forward_ptr; 4220 } 4221 } 4222 4223 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4224 set_evacuation_failed(true); 4225 4226 preserve_mark_if_necessary(old, m); 4227 4228 HeapRegion* r = heap_region_containing(old); 4229 if (!r->evacuation_failed()) { 4230 r->set_evacuation_failed(true); 4231 _hr_printer.evac_failure(r); 4232 } 4233 4234 push_on_evac_failure_scan_stack(old); 4235 4236 if (!_drain_in_progress) { 4237 // prevent recursion in copy_to_survivor_space() 4238 _drain_in_progress = true; 4239 drain_evac_failure_scan_stack(); 4240 _drain_in_progress = false; 4241 } 4242 } 4243 4244 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4245 assert(evacuation_failed(), "Oversaving!"); 4246 // We want to call the "for_promotion_failure" version only in the 4247 // case of a promotion failure. 4248 if (m->must_be_preserved_for_promotion_failure(obj)) { 4249 if (_objs_with_preserved_marks == NULL) { 4250 assert(_preserved_marks_of_objs == NULL, "Both or none."); 4251 _objs_with_preserved_marks = 4252 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true); 4253 _preserved_marks_of_objs = 4254 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true); 4255 } 4256 _objs_with_preserved_marks->push(obj); 4257 _preserved_marks_of_objs->push(m); 4258 } 4259 } 4260 4261 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4262 size_t word_size) { 4263 if (purpose == GCAllocForSurvived) { 4264 HeapWord* result = survivor_attempt_allocation(word_size); 4265 if (result != NULL) { 4266 return result; 4267 } else { 4268 // Let's try to allocate in the old gen in case we can fit the 4269 // object there. 4270 return old_attempt_allocation(word_size); 4271 } 4272 } else { 4273 assert(purpose == GCAllocForTenured, "sanity"); 4274 HeapWord* result = old_attempt_allocation(word_size); 4275 if (result != NULL) { 4276 return result; 4277 } else { 4278 // Let's try to allocate in the survivors in case we can fit the 4279 // object there. 4280 return survivor_attempt_allocation(word_size); 4281 } 4282 } 4283 4284 ShouldNotReachHere(); 4285 // Trying to keep some compilers happy. 4286 return NULL; 4287 } 4288 4289 #ifndef PRODUCT 4290 bool GCLabBitMapClosure::do_bit(size_t offset) { 4291 HeapWord* addr = _bitmap->offsetToHeapWord(offset); 4292 guarantee(_cm->isMarked(oop(addr)), "it should be!"); 4293 return true; 4294 } 4295 #endif // PRODUCT 4296 4297 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) : 4298 ParGCAllocBuffer(gclab_word_size), 4299 _should_mark_objects(false), 4300 _bitmap(G1CollectedHeap::heap()->reserved_region().start(), gclab_word_size), 4301 _retired(false) 4302 { 4303 //_should_mark_objects is set to true when G1ParCopyHelper needs to 4304 // mark the forwarded location of an evacuated object. 4305 // We set _should_mark_objects to true if marking is active, i.e. when we 4306 // need to propagate a mark, or during an initial mark pause, i.e. when we 4307 // need to mark objects immediately reachable by the roots. 4308 if (G1CollectedHeap::heap()->mark_in_progress() || 4309 G1CollectedHeap::heap()->g1_policy()->during_initial_mark_pause()) { 4310 _should_mark_objects = true; 4311 } 4312 } 4313 4314 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num) 4315 : _g1h(g1h), 4316 _refs(g1h->task_queue(queue_num)), 4317 _dcq(&g1h->dirty_card_queue_set()), 4318 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()), 4319 _g1_rem(g1h->g1_rem_set()), 4320 _hash_seed(17), _queue_num(queue_num), 4321 _term_attempts(0), 4322 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 4323 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 4324 _age_table(false), 4325 _strong_roots_time(0), _term_time(0), 4326 _alloc_buffer_waste(0), _undo_waste(0) 4327 { 4328 // we allocate G1YoungSurvRateNumRegions plus one entries, since 4329 // we "sacrifice" entry 0 to keep track of surviving bytes for 4330 // non-young regions (where the age is -1) 4331 // We also add a few elements at the beginning and at the end in 4332 // an attempt to eliminate cache contention 4333 size_t real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); 4334 size_t array_length = PADDING_ELEM_NUM + 4335 real_length + 4336 PADDING_ELEM_NUM; 4337 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length); 4338 if (_surviving_young_words_base == NULL) 4339 vm_exit_out_of_memory(array_length * sizeof(size_t), 4340 "Not enough space for young surv histo."); 4341 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 4342 memset(_surviving_young_words, 0, real_length * sizeof(size_t)); 4343 4344 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 4345 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 4346 4347 _start = os::elapsedTime(); 4348 } 4349 4350 void 4351 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 4352 { 4353 st->print_raw_cr("GC Termination Stats"); 4354 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 4355 " ------waste (KiB)------"); 4356 st->print_raw_cr("thr ms ms % ms % attempts" 4357 " total alloc undo"); 4358 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 4359 " ------- ------- -------"); 4360 } 4361 4362 void 4363 G1ParScanThreadState::print_termination_stats(int i, 4364 outputStream* const st) const 4365 { 4366 const double elapsed_ms = elapsed_time() * 1000.0; 4367 const double s_roots_ms = strong_roots_time() * 1000.0; 4368 const double term_ms = term_time() * 1000.0; 4369 st->print_cr("%3d %9.2f %9.2f %6.2f " 4370 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4371 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4372 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 4373 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 4374 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 4375 alloc_buffer_waste() * HeapWordSize / K, 4376 undo_waste() * HeapWordSize / K); 4377 } 4378 4379 #ifdef ASSERT 4380 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 4381 assert(ref != NULL, "invariant"); 4382 assert(UseCompressedOops, "sanity"); 4383 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); 4384 oop p = oopDesc::load_decode_heap_oop(ref); 4385 assert(_g1h->is_in_g1_reserved(p), 4386 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4387 return true; 4388 } 4389 4390 bool G1ParScanThreadState::verify_ref(oop* ref) const { 4391 assert(ref != NULL, "invariant"); 4392 if (has_partial_array_mask(ref)) { 4393 // Must be in the collection set--it's already been copied. 4394 oop p = clear_partial_array_mask(ref); 4395 assert(_g1h->obj_in_cs(p), 4396 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4397 } else { 4398 oop p = oopDesc::load_decode_heap_oop(ref); 4399 assert(_g1h->is_in_g1_reserved(p), 4400 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4401 } 4402 return true; 4403 } 4404 4405 bool G1ParScanThreadState::verify_task(StarTask ref) const { 4406 if (ref.is_narrow()) { 4407 return verify_ref((narrowOop*) ref); 4408 } else { 4409 return verify_ref((oop*) ref); 4410 } 4411 } 4412 #endif // ASSERT 4413 4414 void G1ParScanThreadState::trim_queue() { 4415 assert(_evac_cl != NULL, "not set"); 4416 assert(_evac_failure_cl != NULL, "not set"); 4417 assert(_partial_scan_cl != NULL, "not set"); 4418 4419 StarTask ref; 4420 do { 4421 // Drain the overflow stack first, so other threads can steal. 4422 while (refs()->pop_overflow(ref)) { 4423 deal_with_reference(ref); 4424 } 4425 4426 while (refs()->pop_local(ref)) { 4427 deal_with_reference(ref); 4428 } 4429 } while (!refs()->is_empty()); 4430 } 4431 4432 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) : 4433 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()), 4434 _par_scan_state(par_scan_state), 4435 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()), 4436 _mark_in_progress(_g1->mark_in_progress()) { } 4437 4438 template <class T> void G1ParCopyHelper::mark_object(T* p) { 4439 // This is called from do_oop_work for objects that are not 4440 // in the collection set. Objects in the collection set 4441 // are marked after they have been evacuated. 4442 4443 T heap_oop = oopDesc::load_heap_oop(p); 4444 if (!oopDesc::is_null(heap_oop)) { 4445 oop obj = oopDesc::decode_heap_oop(heap_oop); 4446 HeapWord* addr = (HeapWord*)obj; 4447 if (_g1->is_in_g1_reserved(addr)) { 4448 _cm->grayRoot(oop(addr)); 4449 } 4450 } 4451 } 4452 4453 oop G1ParCopyHelper::copy_to_survivor_space(oop old, bool should_mark_root, 4454 bool should_mark_copy) { 4455 size_t word_sz = old->size(); 4456 HeapRegion* from_region = _g1->heap_region_containing_raw(old); 4457 // +1 to make the -1 indexes valid... 4458 int young_index = from_region->young_index_in_cset()+1; 4459 assert( (from_region->is_young() && young_index > 0) || 4460 (!from_region->is_young() && young_index == 0), "invariant" ); 4461 G1CollectorPolicy* g1p = _g1->g1_policy(); 4462 markOop m = old->mark(); 4463 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 4464 : m->age(); 4465 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 4466 word_sz); 4467 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz); 4468 oop obj = oop(obj_ptr); 4469 4470 if (obj_ptr == NULL) { 4471 // This will either forward-to-self, or detect that someone else has 4472 // installed a forwarding pointer. 4473 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4474 return _g1->handle_evacuation_failure_par(cl, old, should_mark_root); 4475 } 4476 4477 // We're going to allocate linearly, so might as well prefetch ahead. 4478 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 4479 4480 oop forward_ptr = old->forward_to_atomic(obj); 4481 if (forward_ptr == NULL) { 4482 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 4483 if (g1p->track_object_age(alloc_purpose)) { 4484 // We could simply do obj->incr_age(). However, this causes a 4485 // performance issue. obj->incr_age() will first check whether 4486 // the object has a displaced mark by checking its mark word; 4487 // getting the mark word from the new location of the object 4488 // stalls. So, given that we already have the mark word and we 4489 // are about to install it anyway, it's better to increase the 4490 // age on the mark word, when the object does not have a 4491 // displaced mark word. We're not expecting many objects to have 4492 // a displaced marked word, so that case is not optimized 4493 // further (it could be...) and we simply call obj->incr_age(). 4494 4495 if (m->has_displaced_mark_helper()) { 4496 // in this case, we have to install the mark word first, 4497 // otherwise obj looks to be forwarded (the old mark word, 4498 // which contains the forward pointer, was copied) 4499 obj->set_mark(m); 4500 obj->incr_age(); 4501 } else { 4502 m = m->incr_age(); 4503 obj->set_mark(m); 4504 } 4505 _par_scan_state->age_table()->add(obj, word_sz); 4506 } else { 4507 obj->set_mark(m); 4508 } 4509 4510 // Mark the evacuated object or propagate "next" mark bit 4511 if (should_mark_copy) { 4512 if (!use_local_bitmaps || 4513 !_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) { 4514 // if we couldn't mark it on the local bitmap (this happens when 4515 // the object was not allocated in the GCLab), we have to bite 4516 // the bullet and do the standard parallel mark 4517 _cm->markAndGrayObjectIfNecessary(obj); 4518 } 4519 4520 if (_g1->isMarkedNext(old)) { 4521 // Unmark the object's old location so that marking 4522 // doesn't think the old object is alive. 4523 _cm->nextMarkBitMap()->parClear((HeapWord*)old); 4524 } 4525 } 4526 4527 size_t* surv_young_words = _par_scan_state->surviving_young_words(); 4528 surv_young_words[young_index] += word_sz; 4529 4530 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 4531 arrayOop(old)->set_length(0); 4532 oop* old_p = set_partial_array_mask(old); 4533 _par_scan_state->push_on_queue(old_p); 4534 } else { 4535 // No point in using the slower heap_region_containing() method, 4536 // given that we know obj is in the heap. 4537 _scanner->set_region(_g1->heap_region_containing_raw(obj)); 4538 obj->oop_iterate_backwards(_scanner); 4539 } 4540 } else { 4541 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4542 obj = forward_ptr; 4543 } 4544 return obj; 4545 } 4546 4547 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4548 template <class T> 4549 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4550 ::do_oop_work(T* p) { 4551 oop obj = oopDesc::load_decode_heap_oop(p); 4552 assert(barrier != G1BarrierRS || obj != NULL, 4553 "Precondition: G1BarrierRS implies obj is nonNull"); 4554 4555 // Marking: 4556 // If the object is in the collection set, then the thread 4557 // that copies the object should mark, or propagate the 4558 // mark to, the evacuated object. 4559 // If the object is not in the collection set then we 4560 // should call the mark_object() method depending on the 4561 // value of the template parameter do_mark_object (which will 4562 // be true for root scanning closures during an initial mark 4563 // pause). 4564 // The mark_object() method first checks whether the object 4565 // is marked and, if not, attempts to mark the object. 4566 4567 // here the null check is implicit in the cset_fast_test() test 4568 if (_g1->in_cset_fast_test(obj)) { 4569 if (obj->is_forwarded()) { 4570 oopDesc::encode_store_heap_oop(p, obj->forwardee()); 4571 // If we are a root scanning closure during an initial 4572 // mark pause (i.e. do_mark_object will be true) then 4573 // we also need to handle marking of roots in the 4574 // event of an evacuation failure. In the event of an 4575 // evacuation failure, the object is forwarded to itself 4576 // and not copied. For root-scanning closures, the 4577 // object would be marked after a successful self-forward 4578 // but an object could be pointed to by both a root and non 4579 // root location and be self-forwarded by a non-root-scanning 4580 // closure. Therefore we also have to attempt to mark the 4581 // self-forwarded root object here. 4582 if (do_mark_object && obj->forwardee() == obj) { 4583 mark_object(p); 4584 } 4585 } else { 4586 // During an initial mark pause, objects that are pointed to 4587 // by the roots need to be marked - even in the event of an 4588 // evacuation failure. We pass the template parameter 4589 // do_mark_object (which is true for root scanning closures 4590 // during an initial mark pause) to copy_to_survivor_space 4591 // which will pass it on to the evacuation failure handling 4592 // code. The thread that successfully self-forwards a root 4593 // object to itself is responsible for marking the object. 4594 bool should_mark_root = do_mark_object; 4595 4596 // We need to mark the copied object if we're a root scanning 4597 // closure during an initial mark pause (i.e. do_mark_object 4598 // will be true), or the object is already marked and we need 4599 // to propagate the mark to the evacuated copy. 4600 bool should_mark_copy = do_mark_object || 4601 _during_initial_mark || 4602 (_mark_in_progress && !_g1->is_obj_ill(obj)); 4603 4604 oop copy_oop = copy_to_survivor_space(obj, should_mark_root, 4605 should_mark_copy); 4606 oopDesc::encode_store_heap_oop(p, copy_oop); 4607 } 4608 // When scanning the RS, we only care about objs in CS. 4609 if (barrier == G1BarrierRS) { 4610 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num()); 4611 } 4612 } else { 4613 // The object is not in collection set. If we're a root scanning 4614 // closure during an initial mark pause (i.e. do_mark_object will 4615 // be true) then attempt to mark the object. 4616 if (do_mark_object) { 4617 mark_object(p); 4618 } 4619 } 4620 4621 if (barrier == G1BarrierEvac && obj != NULL) { 4622 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num()); 4623 } 4624 4625 if (do_gen_barrier && obj != NULL) { 4626 par_do_barrier(p); 4627 } 4628 } 4629 4630 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p); 4631 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p); 4632 4633 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) { 4634 assert(has_partial_array_mask(p), "invariant"); 4635 oop old = clear_partial_array_mask(p); 4636 assert(old->is_objArray(), "must be obj array"); 4637 assert(old->is_forwarded(), "must be forwarded"); 4638 assert(Universe::heap()->is_in_reserved(old), "must be in heap."); 4639 4640 objArrayOop obj = objArrayOop(old->forwardee()); 4641 assert((void*)old != (void*)old->forwardee(), "self forwarding here?"); 4642 // Process ParGCArrayScanChunk elements now 4643 // and push the remainder back onto queue 4644 int start = arrayOop(old)->length(); 4645 int end = obj->length(); 4646 int remainder = end - start; 4647 assert(start <= end, "just checking"); 4648 if (remainder > 2 * ParGCArrayScanChunk) { 4649 // Test above combines last partial chunk with a full chunk 4650 end = start + ParGCArrayScanChunk; 4651 arrayOop(old)->set_length(end); 4652 // Push remainder. 4653 oop* old_p = set_partial_array_mask(old); 4654 assert(arrayOop(old)->length() < obj->length(), "Empty push?"); 4655 _par_scan_state->push_on_queue(old_p); 4656 } else { 4657 // Restore length so that the heap remains parsable in 4658 // case of evacuation failure. 4659 arrayOop(old)->set_length(end); 4660 } 4661 _scanner.set_region(_g1->heap_region_containing_raw(obj)); 4662 // process our set of indices (include header in first chunk) 4663 obj->oop_iterate_range(&_scanner, start, end); 4664 } 4665 4666 class G1ParEvacuateFollowersClosure : public VoidClosure { 4667 protected: 4668 G1CollectedHeap* _g1h; 4669 G1ParScanThreadState* _par_scan_state; 4670 RefToScanQueueSet* _queues; 4671 ParallelTaskTerminator* _terminator; 4672 4673 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4674 RefToScanQueueSet* queues() { return _queues; } 4675 ParallelTaskTerminator* terminator() { return _terminator; } 4676 4677 public: 4678 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4679 G1ParScanThreadState* par_scan_state, 4680 RefToScanQueueSet* queues, 4681 ParallelTaskTerminator* terminator) 4682 : _g1h(g1h), _par_scan_state(par_scan_state), 4683 _queues(queues), _terminator(terminator) {} 4684 4685 void do_void(); 4686 4687 private: 4688 inline bool offer_termination(); 4689 }; 4690 4691 bool G1ParEvacuateFollowersClosure::offer_termination() { 4692 G1ParScanThreadState* const pss = par_scan_state(); 4693 pss->start_term_time(); 4694 const bool res = terminator()->offer_termination(); 4695 pss->end_term_time(); 4696 return res; 4697 } 4698 4699 void G1ParEvacuateFollowersClosure::do_void() { 4700 StarTask stolen_task; 4701 G1ParScanThreadState* const pss = par_scan_state(); 4702 pss->trim_queue(); 4703 4704 do { 4705 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { 4706 assert(pss->verify_task(stolen_task), "sanity"); 4707 if (stolen_task.is_narrow()) { 4708 pss->deal_with_reference((narrowOop*) stolen_task); 4709 } else { 4710 pss->deal_with_reference((oop*) stolen_task); 4711 } 4712 4713 // We've just processed a reference and we might have made 4714 // available new entries on the queues. So we have to make sure 4715 // we drain the queues as necessary. 4716 pss->trim_queue(); 4717 } 4718 } while (!offer_termination()); 4719 4720 pss->retire_alloc_buffers(); 4721 } 4722 4723 class G1ParTask : public AbstractGangTask { 4724 protected: 4725 G1CollectedHeap* _g1h; 4726 RefToScanQueueSet *_queues; 4727 ParallelTaskTerminator _terminator; 4728 int _n_workers; 4729 4730 Mutex _stats_lock; 4731 Mutex* stats_lock() { return &_stats_lock; } 4732 4733 size_t getNCards() { 4734 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) 4735 / G1BlockOffsetSharedArray::N_bytes; 4736 } 4737 4738 public: 4739 G1ParTask(G1CollectedHeap* g1h, 4740 RefToScanQueueSet *task_queues) 4741 : AbstractGangTask("G1 collection"), 4742 _g1h(g1h), 4743 _queues(task_queues), 4744 _terminator(0, _queues), 4745 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4746 {} 4747 4748 RefToScanQueueSet* queues() { return _queues; } 4749 4750 RefToScanQueue *work_queue(int i) { 4751 return queues()->queue(i); 4752 } 4753 4754 ParallelTaskTerminator* terminator() { return &_terminator; } 4755 4756 virtual void set_for_termination(int active_workers) { 4757 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4758 // in the young space (_par_seq_tasks) in the G1 heap 4759 // for SequentialSubTasksDone. 4760 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4761 // both of which need setting by set_n_termination(). 4762 _g1h->SharedHeap::set_n_termination(active_workers); 4763 _g1h->set_n_termination(active_workers); 4764 terminator()->reset_for_reuse(active_workers); 4765 _n_workers = active_workers; 4766 } 4767 4768 void work(int i) { 4769 if (i >= _n_workers) return; // no work needed this round 4770 4771 double start_time_ms = os::elapsedTime() * 1000.0; 4772 _g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms); 4773 4774 ResourceMark rm; 4775 HandleMark hm; 4776 4777 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4778 4779 G1ParScanThreadState pss(_g1h, i); 4780 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp); 4781 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4782 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp); 4783 4784 pss.set_evac_closure(&scan_evac_cl); 4785 pss.set_evac_failure_closure(&evac_failure_cl); 4786 pss.set_partial_scan_closure(&partial_scan_cl); 4787 4788 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp); 4789 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp); 4790 4791 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp); 4792 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp); 4793 4794 OopClosure* scan_root_cl = &only_scan_root_cl; 4795 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl; 4796 4797 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4798 // We also need to mark copied objects. 4799 scan_root_cl = &scan_mark_root_cl; 4800 scan_perm_cl = &scan_mark_perm_cl; 4801 } 4802 4803 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4804 4805 pss.start_strong_roots(); 4806 _g1h->g1_process_strong_roots(/* not collecting perm */ false, 4807 SharedHeap::SO_AllClasses, 4808 scan_root_cl, 4809 &push_heap_rs_cl, 4810 scan_perm_cl, 4811 i); 4812 pss.end_strong_roots(); 4813 4814 { 4815 double start = os::elapsedTime(); 4816 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4817 evac.do_void(); 4818 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4819 double term_ms = pss.term_time()*1000.0; 4820 _g1h->g1_policy()->record_obj_copy_time(i, elapsed_ms-term_ms); 4821 _g1h->g1_policy()->record_termination(i, term_ms, pss.term_attempts()); 4822 } 4823 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4824 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4825 4826 // Clean up any par-expanded rem sets. 4827 HeapRegionRemSet::par_cleanup(); 4828 4829 if (ParallelGCVerbose) { 4830 MutexLocker x(stats_lock()); 4831 pss.print_termination_stats(i); 4832 } 4833 4834 assert(pss.refs()->is_empty(), "should be empty"); 4835 double end_time_ms = os::elapsedTime() * 1000.0; 4836 _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms); 4837 } 4838 }; 4839 4840 // *** Common G1 Evacuation Stuff 4841 4842 // This method is run in a GC worker. 4843 4844 void 4845 G1CollectedHeap:: 4846 g1_process_strong_roots(bool collecting_perm_gen, 4847 SharedHeap::ScanningOption so, 4848 OopClosure* scan_non_heap_roots, 4849 OopsInHeapRegionClosure* scan_rs, 4850 OopsInGenClosure* scan_perm, 4851 int worker_i) { 4852 4853 // First scan the strong roots, including the perm gen. 4854 double ext_roots_start = os::elapsedTime(); 4855 double closure_app_time_sec = 0.0; 4856 4857 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 4858 BufferingOopsInGenClosure buf_scan_perm(scan_perm); 4859 buf_scan_perm.set_generation(perm_gen()); 4860 4861 // Walk the code cache w/o buffering, because StarTask cannot handle 4862 // unaligned oop locations. 4863 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true); 4864 4865 process_strong_roots(false, // no scoping; this is parallel code 4866 collecting_perm_gen, so, 4867 &buf_scan_non_heap_roots, 4868 &eager_scan_code_roots, 4869 &buf_scan_perm); 4870 4871 // Now the CM ref_processor roots. 4872 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 4873 // We need to treat the discovered reference lists of the 4874 // concurrent mark ref processor as roots and keep entries 4875 // (which are added by the marking threads) on them live 4876 // until they can be processed at the end of marking. 4877 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 4878 } 4879 4880 // Finish up any enqueued closure apps (attributed as object copy time). 4881 buf_scan_non_heap_roots.done(); 4882 buf_scan_perm.done(); 4883 4884 double ext_roots_end = os::elapsedTime(); 4885 4886 g1_policy()->reset_obj_copy_time(worker_i); 4887 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() + 4888 buf_scan_non_heap_roots.closure_app_seconds(); 4889 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 4890 4891 double ext_root_time_ms = 4892 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0; 4893 4894 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 4895 4896 // Scan strong roots in mark stack. 4897 if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) { 4898 concurrent_mark()->oops_do(scan_non_heap_roots); 4899 } 4900 double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0; 4901 g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms); 4902 4903 // Now scan the complement of the collection set. 4904 if (scan_rs != NULL) { 4905 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i); 4906 } 4907 4908 _process_strong_tasks->all_tasks_completed(); 4909 } 4910 4911 void 4912 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure, 4913 OopClosure* non_root_closure) { 4914 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); 4915 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure); 4916 } 4917 4918 // Weak Reference Processing support 4919 4920 // An always "is_alive" closure that is used to preserve referents. 4921 // If the object is non-null then it's alive. Used in the preservation 4922 // of referent objects that are pointed to by reference objects 4923 // discovered by the CM ref processor. 4924 class G1AlwaysAliveClosure: public BoolObjectClosure { 4925 G1CollectedHeap* _g1; 4926 public: 4927 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4928 void do_object(oop p) { assert(false, "Do not call."); } 4929 bool do_object_b(oop p) { 4930 if (p != NULL) { 4931 return true; 4932 } 4933 return false; 4934 } 4935 }; 4936 4937 bool G1STWIsAliveClosure::do_object_b(oop p) { 4938 // An object is reachable if it is outside the collection set, 4939 // or is inside and copied. 4940 return !_g1->obj_in_cs(p) || p->is_forwarded(); 4941 } 4942 4943 // Non Copying Keep Alive closure 4944 class G1KeepAliveClosure: public OopClosure { 4945 G1CollectedHeap* _g1; 4946 public: 4947 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 4948 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 4949 void do_oop( oop* p) { 4950 oop obj = *p; 4951 4952 if (_g1->obj_in_cs(obj)) { 4953 assert( obj->is_forwarded(), "invariant" ); 4954 *p = obj->forwardee(); 4955 } 4956 } 4957 }; 4958 4959 // Copying Keep Alive closure - can be called from both 4960 // serial and parallel code as long as different worker 4961 // threads utilize different G1ParScanThreadState instances 4962 // and different queues. 4963 4964 class G1CopyingKeepAliveClosure: public OopClosure { 4965 G1CollectedHeap* _g1h; 4966 OopClosure* _copy_non_heap_obj_cl; 4967 OopsInHeapRegionClosure* _copy_perm_obj_cl; 4968 G1ParScanThreadState* _par_scan_state; 4969 4970 public: 4971 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 4972 OopClosure* non_heap_obj_cl, 4973 OopsInHeapRegionClosure* perm_obj_cl, 4974 G1ParScanThreadState* pss): 4975 _g1h(g1h), 4976 _copy_non_heap_obj_cl(non_heap_obj_cl), 4977 _copy_perm_obj_cl(perm_obj_cl), 4978 _par_scan_state(pss) 4979 {} 4980 4981 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 4982 virtual void do_oop( oop* p) { do_oop_work(p); } 4983 4984 template <class T> void do_oop_work(T* p) { 4985 oop obj = oopDesc::load_decode_heap_oop(p); 4986 4987 if (_g1h->obj_in_cs(obj)) { 4988 // If the referent object has been forwarded (either copied 4989 // to a new location or to itself in the event of an 4990 // evacuation failure) then we need to update the reference 4991 // field and, if both reference and referent are in the G1 4992 // heap, update the RSet for the referent. 4993 // 4994 // If the referent has not been forwarded then we have to keep 4995 // it alive by policy. Therefore we have copy the referent. 4996 // 4997 // If the reference field is in the G1 heap then we can push 4998 // on the PSS queue. When the queue is drained (after each 4999 // phase of reference processing) the object and it's followers 5000 // will be copied, the reference field set to point to the 5001 // new location, and the RSet updated. Otherwise we need to 5002 // use the the non-heap or perm closures directly to copy 5003 // the refernt object and update the pointer, while avoiding 5004 // updating the RSet. 5005 5006 if (_g1h->is_in_g1_reserved(p)) { 5007 _par_scan_state->push_on_queue(p); 5008 } else { 5009 // The reference field is not in the G1 heap. 5010 if (_g1h->perm_gen()->is_in(p)) { 5011 _copy_perm_obj_cl->do_oop(p); 5012 } else { 5013 _copy_non_heap_obj_cl->do_oop(p); 5014 } 5015 } 5016 } 5017 } 5018 }; 5019 5020 // Serial drain queue closure. Called as the 'complete_gc' 5021 // closure for each discovered list in some of the 5022 // reference processing phases. 5023 5024 class G1STWDrainQueueClosure: public VoidClosure { 5025 protected: 5026 G1CollectedHeap* _g1h; 5027 G1ParScanThreadState* _par_scan_state; 5028 5029 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5030 5031 public: 5032 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5033 _g1h(g1h), 5034 _par_scan_state(pss) 5035 { } 5036 5037 void do_void() { 5038 G1ParScanThreadState* const pss = par_scan_state(); 5039 pss->trim_queue(); 5040 } 5041 }; 5042 5043 // Parallel Reference Processing closures 5044 5045 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5046 // processing during G1 evacuation pauses. 5047 5048 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5049 private: 5050 G1CollectedHeap* _g1h; 5051 RefToScanQueueSet* _queues; 5052 FlexibleWorkGang* _workers; 5053 int _active_workers; 5054 5055 public: 5056 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5057 FlexibleWorkGang* workers, 5058 RefToScanQueueSet *task_queues, 5059 int n_workers) : 5060 _g1h(g1h), 5061 _queues(task_queues), 5062 _workers(workers), 5063 _active_workers(n_workers) 5064 { 5065 assert(n_workers > 0, "shouldn't call this otherwise"); 5066 } 5067 5068 // Executes the given task using concurrent marking worker threads. 5069 virtual void execute(ProcessTask& task); 5070 virtual void execute(EnqueueTask& task); 5071 }; 5072 5073 // Gang task for possibly parallel reference processing 5074 5075 class G1STWRefProcTaskProxy: public AbstractGangTask { 5076 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5077 ProcessTask& _proc_task; 5078 G1CollectedHeap* _g1h; 5079 RefToScanQueueSet *_task_queues; 5080 ParallelTaskTerminator* _terminator; 5081 5082 public: 5083 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5084 G1CollectedHeap* g1h, 5085 RefToScanQueueSet *task_queues, 5086 ParallelTaskTerminator* terminator) : 5087 AbstractGangTask("Process reference objects in parallel"), 5088 _proc_task(proc_task), 5089 _g1h(g1h), 5090 _task_queues(task_queues), 5091 _terminator(terminator) 5092 {} 5093 5094 virtual void work(int i) { 5095 // The reference processing task executed by a single worker. 5096 ResourceMark rm; 5097 HandleMark hm; 5098 5099 G1STWIsAliveClosure is_alive(_g1h); 5100 5101 G1ParScanThreadState pss(_g1h, i); 5102 5103 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5104 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5105 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5106 5107 pss.set_evac_closure(&scan_evac_cl); 5108 pss.set_evac_failure_closure(&evac_failure_cl); 5109 pss.set_partial_scan_closure(&partial_scan_cl); 5110 5111 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5112 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL); 5113 5114 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5115 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL); 5116 5117 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5118 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl; 5119 5120 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5121 // We also need to mark copied objects. 5122 copy_non_heap_cl = ©_mark_non_heap_cl; 5123 copy_perm_cl = ©_mark_perm_cl; 5124 } 5125 5126 // Keep alive closure. 5127 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss); 5128 5129 // Complete GC closure 5130 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5131 5132 // Call the reference processing task's work routine. 5133 _proc_task.work(i, is_alive, keep_alive, drain_queue); 5134 5135 // Note we cannot assert that the refs array is empty here as not all 5136 // of the processing tasks (specifically phase2 - pp2_work) execute 5137 // the complete_gc closure (which ordinarily would drain the queue) so 5138 // the queue may not be empty. 5139 } 5140 }; 5141 5142 // Driver routine for parallel reference processing. 5143 // Creates an instance of the ref processing gang 5144 // task and has the worker threads execute it. 5145 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5146 assert(_workers != NULL, "Need parallel worker threads."); 5147 5148 ParallelTaskTerminator terminator(_active_workers, _queues); 5149 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5150 5151 _g1h->set_par_threads(_active_workers); 5152 _workers->run_task(&proc_task_proxy); 5153 _g1h->set_par_threads(0); 5154 } 5155 5156 // Gang task for parallel reference enqueueing. 5157 5158 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5159 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5160 EnqueueTask& _enq_task; 5161 5162 public: 5163 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5164 AbstractGangTask("Enqueue reference objects in parallel"), 5165 _enq_task(enq_task) 5166 { } 5167 5168 virtual void work(int i) { 5169 _enq_task.work(i); 5170 } 5171 }; 5172 5173 // Driver routine for parallel reference enqueing. 5174 // Creates an instance of the ref enqueueing gang 5175 // task and has the worker threads execute it. 5176 5177 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5178 assert(_workers != NULL, "Need parallel worker threads."); 5179 5180 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5181 5182 _g1h->set_par_threads(_active_workers); 5183 _workers->run_task(&enq_task_proxy); 5184 _g1h->set_par_threads(0); 5185 } 5186 5187 // End of weak reference support closures 5188 5189 // Abstract task used to preserve (i.e. copy) any referent objects 5190 // that are in the collection set and are pointed to by reference 5191 // objects discovered by the CM ref processor. 5192 5193 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5194 protected: 5195 G1CollectedHeap* _g1h; 5196 RefToScanQueueSet *_queues; 5197 ParallelTaskTerminator _terminator; 5198 int _n_workers; 5199 5200 public: 5201 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5202 AbstractGangTask("ParPreserveCMReferents"), 5203 _g1h(g1h), 5204 _queues(task_queues), 5205 _terminator(workers, _queues), 5206 _n_workers(workers) 5207 { } 5208 5209 void work(int i) { 5210 ResourceMark rm; 5211 HandleMark hm; 5212 5213 G1ParScanThreadState pss(_g1h, i); 5214 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5215 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5216 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5217 5218 pss.set_evac_closure(&scan_evac_cl); 5219 pss.set_evac_failure_closure(&evac_failure_cl); 5220 pss.set_partial_scan_closure(&partial_scan_cl); 5221 5222 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5223 5224 5225 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5226 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL); 5227 5228 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5229 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL); 5230 5231 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5232 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl; 5233 5234 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5235 // We also need to mark copied objects. 5236 copy_non_heap_cl = ©_mark_non_heap_cl; 5237 copy_perm_cl = ©_mark_perm_cl; 5238 } 5239 5240 // Is alive closure 5241 G1AlwaysAliveClosure always_alive(_g1h); 5242 5243 // Copying keep alive closure. Applied to referent objects that need 5244 // to be copied. 5245 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss); 5246 5247 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5248 5249 int limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5250 int stride = MIN2(MAX2(_n_workers, 1), limit); 5251 5252 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5253 // So this must be true - but assert just in case someone decides to 5254 // change the worker ids. 5255 assert(0 <= i && i < limit, "sanity"); 5256 assert(!rp->discovery_is_atomic(), "check this code"); 5257 5258 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5259 for (int idx = i; idx < limit; idx += stride) { 5260 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5261 5262 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5263 while (iter.has_next()) { 5264 // Since discovery is not atomic for the CM ref processor, we 5265 // can see some null referent objects. 5266 iter.load_ptrs(DEBUG_ONLY(true)); 5267 oop ref = iter.obj(); 5268 5269 // This will filter nulls. 5270 if (iter.is_referent_alive()) { 5271 iter.make_referent_alive(); 5272 } 5273 iter.move_to_next(); 5274 } 5275 } 5276 5277 // Drain the queue - which may cause stealing 5278 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5279 drain_queue.do_void(); 5280 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5281 assert(pss.refs()->is_empty(), "should be"); 5282 } 5283 }; 5284 5285 // Weak Reference processing during an evacuation pause (part 1). 5286 void G1CollectedHeap::process_discovered_references() { 5287 double ref_proc_start = os::elapsedTime(); 5288 5289 ReferenceProcessor* rp = _ref_processor_stw; 5290 assert(rp->discovery_enabled(), "should have been enabled"); 5291 5292 // Any reference objects, in the collection set, that were 'discovered' 5293 // by the CM ref processor should have already been copied (either by 5294 // applying the external root copy closure to the discovered lists, or 5295 // by following an RSet entry). 5296 // 5297 // But some of the referents, that are in the collection set, that these 5298 // reference objects point to may not have been copied: the STW ref 5299 // processor would have seen that the reference object had already 5300 // been 'discovered' and would have skipped discovering the reference, 5301 // but would not have treated the reference object as a regular oop. 5302 // As a reult the copy closure would not have been applied to the 5303 // referent object. 5304 // 5305 // We need to explicitly copy these referent objects - the references 5306 // will be processed at the end of remarking. 5307 // 5308 // We also need to do this copying before we process the reference 5309 // objects discovered by the STW ref processor in case one of these 5310 // referents points to another object which is also referenced by an 5311 // object discovered by the STW ref processor. 5312 5313 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5314 workers()->active_workers() : 1); 5315 5316 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5317 active_workers == workers()->active_workers(), 5318 "Need to reset active_workers"); 5319 5320 set_par_threads(active_workers); 5321 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues); 5322 5323 if (G1CollectedHeap::use_parallel_gc_threads()) { 5324 workers()->run_task(&keep_cm_referents); 5325 } else { 5326 keep_cm_referents.work(0); 5327 } 5328 5329 set_par_threads(0); 5330 5331 // Closure to test whether a referent is alive. 5332 G1STWIsAliveClosure is_alive(this); 5333 5334 // Even when parallel reference processing is enabled, the processing 5335 // of JNI refs is serial and performed serially by the current thread 5336 // rather than by a worker. The following PSS will be used for processing 5337 // JNI refs. 5338 5339 // Use only a single queue for this PSS. 5340 G1ParScanThreadState pss(this, 0); 5341 5342 // We do not embed a reference processor in the copying/scanning 5343 // closures while we're actually processing the discovered 5344 // reference objects. 5345 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL); 5346 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5347 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL); 5348 5349 pss.set_evac_closure(&scan_evac_cl); 5350 pss.set_evac_failure_closure(&evac_failure_cl); 5351 pss.set_partial_scan_closure(&partial_scan_cl); 5352 5353 assert(pss.refs()->is_empty(), "pre-condition"); 5354 5355 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5356 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL); 5357 5358 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5359 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL); 5360 5361 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5362 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl; 5363 5364 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5365 // We also need to mark copied objects. 5366 copy_non_heap_cl = ©_mark_non_heap_cl; 5367 copy_perm_cl = ©_mark_perm_cl; 5368 } 5369 5370 // Keep alive closure. 5371 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss); 5372 5373 // Serial Complete GC closure 5374 G1STWDrainQueueClosure drain_queue(this, &pss); 5375 5376 // Setup the soft refs policy... 5377 rp->setup_policy(false); 5378 5379 if (!rp->processing_is_mt()) { 5380 // Serial reference processing... 5381 rp->process_discovered_references(&is_alive, 5382 &keep_alive, 5383 &drain_queue, 5384 NULL); 5385 } else { 5386 // Parallel reference processing 5387 assert(rp->num_q() == active_workers, "sanity"); 5388 assert(active_workers <= rp->max_num_q(), "sanity"); 5389 5390 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers); 5391 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor); 5392 } 5393 5394 // We have completed copying any necessary live referent objects 5395 // (that were not copied during the actual pause) so we can 5396 // retire any active alloc buffers 5397 pss.retire_alloc_buffers(); 5398 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5399 5400 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5401 g1_policy()->record_ref_proc_time(ref_proc_time * 1000.0); 5402 } 5403 5404 // Weak Reference processing during an evacuation pause (part 2). 5405 void G1CollectedHeap::enqueue_discovered_references() { 5406 double ref_enq_start = os::elapsedTime(); 5407 5408 ReferenceProcessor* rp = _ref_processor_stw; 5409 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5410 5411 // Now enqueue any remaining on the discovered lists on to 5412 // the pending list. 5413 if (!rp->processing_is_mt()) { 5414 // Serial reference processing... 5415 rp->enqueue_discovered_references(); 5416 } else { 5417 // Parallel reference enqueuing 5418 5419 int active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1); 5420 assert(active_workers == workers()->active_workers(), 5421 "Need to reset active_workers"); 5422 assert(rp->num_q() == active_workers, "sanity"); 5423 assert(active_workers <= rp->max_num_q(), "sanity"); 5424 5425 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers); 5426 rp->enqueue_discovered_references(&par_task_executor); 5427 } 5428 5429 rp->verify_no_references_recorded(); 5430 assert(!rp->discovery_enabled(), "should have been disabled"); 5431 5432 // FIXME 5433 // CM's reference processing also cleans up the string and symbol tables. 5434 // Should we do that here also? We could, but it is a serial operation 5435 // and could signicantly increase the pause time. 5436 5437 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5438 g1_policy()->record_ref_enq_time(ref_enq_time * 1000.0); 5439 } 5440 5441 void G1CollectedHeap::evacuate_collection_set() { 5442 set_evacuation_failed(false); 5443 5444 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5445 concurrent_g1_refine()->set_use_cache(false); 5446 concurrent_g1_refine()->clear_hot_cache_claimed_index(); 5447 5448 int n_workers; 5449 if (G1CollectedHeap::use_parallel_gc_threads()) { 5450 n_workers = 5451 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5452 workers()->active_workers(), 5453 Threads::number_of_non_daemon_threads()); 5454 assert(UseDynamicNumberOfGCThreads || 5455 n_workers == workers()->total_workers(), 5456 "If not dynamic should be using all the workers"); 5457 workers()->set_active_workers(n_workers); 5458 set_par_threads(n_workers); 5459 } else { 5460 assert(n_par_threads() == 0, 5461 "Should be the original non-parallel value"); 5462 n_workers = 1; 5463 } 5464 5465 G1ParTask g1_par_task(this, _task_queues); 5466 5467 init_for_evac_failure(NULL); 5468 5469 rem_set()->prepare_for_younger_refs_iterate(true); 5470 5471 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5472 double start_par = os::elapsedTime(); 5473 5474 if (G1CollectedHeap::use_parallel_gc_threads()) { 5475 // The individual threads will set their evac-failure closures. 5476 StrongRootsScope srs(this); 5477 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5478 // These tasks use ShareHeap::_process_strong_tasks 5479 assert(UseDynamicNumberOfGCThreads || 5480 workers()->active_workers() == workers()->total_workers(), 5481 "If not dynamic should be using all the workers"); 5482 workers()->run_task(&g1_par_task); 5483 } else { 5484 StrongRootsScope srs(this); 5485 g1_par_task.set_for_termination(n_workers); 5486 g1_par_task.work(0); 5487 } 5488 5489 double par_time = (os::elapsedTime() - start_par) * 1000.0; 5490 g1_policy()->record_par_time(par_time); 5491 5492 set_par_threads(0); 5493 5494 // Process any discovered reference objects - we have 5495 // to do this _before_ we retire the GC alloc regions 5496 // as we may have to copy some 'reachable' referent 5497 // objects (and their reachable sub-graphs) that were 5498 // not copied during the pause. 5499 process_discovered_references(); 5500 5501 // Weak root processing. 5502 // Note: when JSR 292 is enabled and code blobs can contain 5503 // non-perm oops then we will need to process the code blobs 5504 // here too. 5505 { 5506 G1STWIsAliveClosure is_alive(this); 5507 G1KeepAliveClosure keep_alive(this); 5508 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5509 } 5510 5511 release_gc_alloc_regions(); 5512 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5513 5514 concurrent_g1_refine()->clear_hot_cache(); 5515 concurrent_g1_refine()->set_use_cache(true); 5516 5517 finalize_for_evac_failure(); 5518 5519 // Must do this before clearing the per-region evac-failure flags 5520 // (which is currently done when we free the collection set). 5521 // We also only do this if marking is actually in progress and so 5522 // have to do this before we set the mark_in_progress flag at the 5523 // end of an initial mark pause. 5524 concurrent_mark()->complete_marking_in_collection_set(); 5525 5526 if (evacuation_failed()) { 5527 remove_self_forwarding_pointers(); 5528 if (PrintGCDetails) { 5529 gclog_or_tty->print(" (to-space overflow)"); 5530 } else if (PrintGC) { 5531 gclog_or_tty->print("--"); 5532 } 5533 } 5534 5535 // Enqueue any remaining references remaining on the STW 5536 // reference processor's discovered lists. We need to do 5537 // this after the card table is cleaned (and verified) as 5538 // the act of enqueuing entries on to the pending list 5539 // will log these updates (and dirty their associated 5540 // cards). We need these updates logged to update any 5541 // RSets. 5542 enqueue_discovered_references(); 5543 5544 if (G1DeferredRSUpdate) { 5545 RedirtyLoggedCardTableEntryFastClosure redirty; 5546 dirty_card_queue_set().set_closure(&redirty); 5547 dirty_card_queue_set().apply_closure_to_all_completed_buffers(); 5548 5549 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5550 dcq.merge_bufferlists(&dirty_card_queue_set()); 5551 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5552 } 5553 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5554 } 5555 5556 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr, 5557 size_t* pre_used, 5558 FreeRegionList* free_list, 5559 OldRegionSet* old_proxy_set, 5560 HumongousRegionSet* humongous_proxy_set, 5561 HRRSCleanupTask* hrrs_cleanup_task, 5562 bool par) { 5563 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 5564 if (hr->isHumongous()) { 5565 assert(hr->startsHumongous(), "we should only see starts humongous"); 5566 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par); 5567 } else { 5568 _old_set.remove_with_proxy(hr, old_proxy_set); 5569 free_region(hr, pre_used, free_list, par); 5570 } 5571 } else { 5572 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task); 5573 } 5574 } 5575 5576 void G1CollectedHeap::free_region(HeapRegion* hr, 5577 size_t* pre_used, 5578 FreeRegionList* free_list, 5579 bool par) { 5580 assert(!hr->isHumongous(), "this is only for non-humongous regions"); 5581 assert(!hr->is_empty(), "the region should not be empty"); 5582 assert(free_list != NULL, "pre-condition"); 5583 5584 *pre_used += hr->used(); 5585 hr->hr_clear(par, true /* clear_space */); 5586 free_list->add_as_head(hr); 5587 } 5588 5589 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5590 size_t* pre_used, 5591 FreeRegionList* free_list, 5592 HumongousRegionSet* humongous_proxy_set, 5593 bool par) { 5594 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 5595 assert(free_list != NULL, "pre-condition"); 5596 assert(humongous_proxy_set != NULL, "pre-condition"); 5597 5598 size_t hr_used = hr->used(); 5599 size_t hr_capacity = hr->capacity(); 5600 size_t hr_pre_used = 0; 5601 _humongous_set.remove_with_proxy(hr, humongous_proxy_set); 5602 hr->set_notHumongous(); 5603 free_region(hr, &hr_pre_used, free_list, par); 5604 5605 size_t i = hr->hrs_index() + 1; 5606 size_t num = 1; 5607 while (i < n_regions()) { 5608 HeapRegion* curr_hr = region_at(i); 5609 if (!curr_hr->continuesHumongous()) { 5610 break; 5611 } 5612 curr_hr->set_notHumongous(); 5613 free_region(curr_hr, &hr_pre_used, free_list, par); 5614 num += 1; 5615 i += 1; 5616 } 5617 assert(hr_pre_used == hr_used, 5618 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" " 5619 "should be the same", hr_pre_used, hr_used)); 5620 *pre_used += hr_pre_used; 5621 } 5622 5623 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used, 5624 FreeRegionList* free_list, 5625 OldRegionSet* old_proxy_set, 5626 HumongousRegionSet* humongous_proxy_set, 5627 bool par) { 5628 if (pre_used > 0) { 5629 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL; 5630 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); 5631 assert(_summary_bytes_used >= pre_used, 5632 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" " 5633 "should be >= pre_used: "SIZE_FORMAT, 5634 _summary_bytes_used, pre_used)); 5635 _summary_bytes_used -= pre_used; 5636 } 5637 if (free_list != NULL && !free_list->is_empty()) { 5638 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5639 _free_list.add_as_head(free_list); 5640 } 5641 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) { 5642 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5643 _old_set.update_from_proxy(old_proxy_set); 5644 } 5645 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) { 5646 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5647 _humongous_set.update_from_proxy(humongous_proxy_set); 5648 } 5649 } 5650 5651 class G1ParCleanupCTTask : public AbstractGangTask { 5652 CardTableModRefBS* _ct_bs; 5653 G1CollectedHeap* _g1h; 5654 HeapRegion* volatile _su_head; 5655 public: 5656 G1ParCleanupCTTask(CardTableModRefBS* ct_bs, 5657 G1CollectedHeap* g1h) : 5658 AbstractGangTask("G1 Par Cleanup CT Task"), 5659 _ct_bs(ct_bs), _g1h(g1h) { } 5660 5661 void work(int i) { 5662 HeapRegion* r; 5663 while (r = _g1h->pop_dirty_cards_region()) { 5664 clear_cards(r); 5665 } 5666 } 5667 5668 void clear_cards(HeapRegion* r) { 5669 // Cards of the survivors should have already been dirtied. 5670 if (!r->is_survivor()) { 5671 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5672 } 5673 } 5674 }; 5675 5676 #ifndef PRODUCT 5677 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5678 G1CollectedHeap* _g1h; 5679 CardTableModRefBS* _ct_bs; 5680 public: 5681 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs) 5682 : _g1h(g1h), _ct_bs(ct_bs) { } 5683 virtual bool doHeapRegion(HeapRegion* r) { 5684 if (r->is_survivor()) { 5685 _g1h->verify_dirty_region(r); 5686 } else { 5687 _g1h->verify_not_dirty_region(r); 5688 } 5689 return false; 5690 } 5691 }; 5692 5693 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5694 // All of the region should be clean. 5695 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 5696 MemRegion mr(hr->bottom(), hr->end()); 5697 ct_bs->verify_not_dirty_region(mr); 5698 } 5699 5700 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5701 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5702 // dirty allocated blocks as they allocate them. The thread that 5703 // retires each region and replaces it with a new one will do a 5704 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5705 // not dirty that area (one less thing to have to do while holding 5706 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5707 // is dirty. 5708 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5709 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5710 ct_bs->verify_dirty_region(mr); 5711 } 5712 5713 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5714 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5715 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5716 verify_dirty_region(hr); 5717 } 5718 } 5719 5720 void G1CollectedHeap::verify_dirty_young_regions() { 5721 verify_dirty_young_list(_young_list->first_region()); 5722 verify_dirty_young_list(_young_list->first_survivor_region()); 5723 } 5724 #endif 5725 5726 void G1CollectedHeap::cleanUpCardTable() { 5727 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set()); 5728 double start = os::elapsedTime(); 5729 5730 { 5731 // Iterate over the dirty cards region list. 5732 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5733 5734 if (G1CollectedHeap::use_parallel_gc_threads()) { 5735 set_par_threads(); 5736 workers()->run_task(&cleanup_task); 5737 set_par_threads(0); 5738 } else { 5739 while (_dirty_cards_region_list) { 5740 HeapRegion* r = _dirty_cards_region_list; 5741 cleanup_task.clear_cards(r); 5742 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 5743 if (_dirty_cards_region_list == r) { 5744 // The last region. 5745 _dirty_cards_region_list = NULL; 5746 } 5747 r->set_next_dirty_cards_region(NULL); 5748 } 5749 } 5750 #ifndef PRODUCT 5751 if (G1VerifyCTCleanup || VerifyAfterGC) { 5752 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5753 heap_region_iterate(&cleanup_verifier); 5754 } 5755 #endif 5756 } 5757 5758 double elapsed = os::elapsedTime() - start; 5759 g1_policy()->record_clear_ct_time(elapsed * 1000.0); 5760 } 5761 5762 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) { 5763 size_t pre_used = 0; 5764 FreeRegionList local_free_list("Local List for CSet Freeing"); 5765 5766 double young_time_ms = 0.0; 5767 double non_young_time_ms = 0.0; 5768 5769 // Since the collection set is a superset of the the young list, 5770 // all we need to do to clear the young list is clear its 5771 // head and length, and unlink any young regions in the code below 5772 _young_list->clear(); 5773 5774 G1CollectorPolicy* policy = g1_policy(); 5775 5776 double start_sec = os::elapsedTime(); 5777 bool non_young = true; 5778 5779 HeapRegion* cur = cs_head; 5780 int age_bound = -1; 5781 size_t rs_lengths = 0; 5782 5783 while (cur != NULL) { 5784 assert(!is_on_master_free_list(cur), "sanity"); 5785 if (non_young) { 5786 if (cur->is_young()) { 5787 double end_sec = os::elapsedTime(); 5788 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5789 non_young_time_ms += elapsed_ms; 5790 5791 start_sec = os::elapsedTime(); 5792 non_young = false; 5793 } 5794 } else { 5795 if (!cur->is_young()) { 5796 double end_sec = os::elapsedTime(); 5797 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5798 young_time_ms += elapsed_ms; 5799 5800 start_sec = os::elapsedTime(); 5801 non_young = true; 5802 } 5803 } 5804 5805 rs_lengths += cur->rem_set()->occupied(); 5806 5807 HeapRegion* next = cur->next_in_collection_set(); 5808 assert(cur->in_collection_set(), "bad CS"); 5809 cur->set_next_in_collection_set(NULL); 5810 cur->set_in_collection_set(false); 5811 5812 if (cur->is_young()) { 5813 int index = cur->young_index_in_cset(); 5814 assert(index != -1, "invariant"); 5815 assert((size_t) index < policy->young_cset_region_length(), "invariant"); 5816 size_t words_survived = _surviving_young_words[index]; 5817 cur->record_surv_words_in_group(words_survived); 5818 5819 // At this point the we have 'popped' cur from the collection set 5820 // (linked via next_in_collection_set()) but it is still in the 5821 // young list (linked via next_young_region()). Clear the 5822 // _next_young_region field. 5823 cur->set_next_young_region(NULL); 5824 } else { 5825 int index = cur->young_index_in_cset(); 5826 assert(index == -1, "invariant"); 5827 } 5828 5829 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5830 (!cur->is_young() && cur->young_index_in_cset() == -1), 5831 "invariant" ); 5832 5833 if (!cur->evacuation_failed()) { 5834 MemRegion used_mr = cur->used_region(); 5835 5836 // And the region is empty. 5837 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5838 5839 // If marking is in progress then clear any objects marked in 5840 // the current region. Note mark_in_progress() returns false, 5841 // even during an initial mark pause, until the set_marking_started() 5842 // call which takes place later in the pause. 5843 if (mark_in_progress()) { 5844 assert(!g1_policy()->during_initial_mark_pause(), "sanity"); 5845 _cm->nextMarkBitMap()->clearRange(used_mr); 5846 } 5847 5848 free_region(cur, &pre_used, &local_free_list, false /* par */); 5849 } else { 5850 cur->uninstall_surv_rate_group(); 5851 if (cur->is_young()) { 5852 cur->set_young_index_in_cset(-1); 5853 } 5854 cur->set_not_young(); 5855 cur->set_evacuation_failed(false); 5856 // The region is now considered to be old. 5857 _old_set.add(cur); 5858 } 5859 cur = next; 5860 } 5861 5862 policy->record_max_rs_lengths(rs_lengths); 5863 policy->cset_regions_freed(); 5864 5865 double end_sec = os::elapsedTime(); 5866 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5867 5868 if (non_young) { 5869 non_young_time_ms += elapsed_ms; 5870 } else { 5871 young_time_ms += elapsed_ms; 5872 } 5873 5874 update_sets_after_freeing_regions(pre_used, &local_free_list, 5875 NULL /* old_proxy_set */, 5876 NULL /* humongous_proxy_set */, 5877 false /* par */); 5878 policy->record_young_free_cset_time_ms(young_time_ms); 5879 policy->record_non_young_free_cset_time_ms(non_young_time_ms); 5880 } 5881 5882 // This routine is similar to the above but does not record 5883 // any policy statistics or update free lists; we are abandoning 5884 // the current incremental collection set in preparation of a 5885 // full collection. After the full GC we will start to build up 5886 // the incremental collection set again. 5887 // This is only called when we're doing a full collection 5888 // and is immediately followed by the tearing down of the young list. 5889 5890 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 5891 HeapRegion* cur = cs_head; 5892 5893 while (cur != NULL) { 5894 HeapRegion* next = cur->next_in_collection_set(); 5895 assert(cur->in_collection_set(), "bad CS"); 5896 cur->set_next_in_collection_set(NULL); 5897 cur->set_in_collection_set(false); 5898 cur->set_young_index_in_cset(-1); 5899 cur = next; 5900 } 5901 } 5902 5903 void G1CollectedHeap::set_free_regions_coming() { 5904 if (G1ConcRegionFreeingVerbose) { 5905 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5906 "setting free regions coming"); 5907 } 5908 5909 assert(!free_regions_coming(), "pre-condition"); 5910 _free_regions_coming = true; 5911 } 5912 5913 void G1CollectedHeap::reset_free_regions_coming() { 5914 { 5915 assert(free_regions_coming(), "pre-condition"); 5916 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5917 _free_regions_coming = false; 5918 SecondaryFreeList_lock->notify_all(); 5919 } 5920 5921 if (G1ConcRegionFreeingVerbose) { 5922 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5923 "reset free regions coming"); 5924 } 5925 } 5926 5927 void G1CollectedHeap::wait_while_free_regions_coming() { 5928 // Most of the time we won't have to wait, so let's do a quick test 5929 // first before we take the lock. 5930 if (!free_regions_coming()) { 5931 return; 5932 } 5933 5934 if (G1ConcRegionFreeingVerbose) { 5935 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5936 "waiting for free regions"); 5937 } 5938 5939 { 5940 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5941 while (free_regions_coming()) { 5942 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5943 } 5944 } 5945 5946 if (G1ConcRegionFreeingVerbose) { 5947 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5948 "done waiting for free regions"); 5949 } 5950 } 5951 5952 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5953 assert(heap_lock_held_for_gc(), 5954 "the heap lock should already be held by or for this thread"); 5955 _young_list->push_region(hr); 5956 } 5957 5958 class NoYoungRegionsClosure: public HeapRegionClosure { 5959 private: 5960 bool _success; 5961 public: 5962 NoYoungRegionsClosure() : _success(true) { } 5963 bool doHeapRegion(HeapRegion* r) { 5964 if (r->is_young()) { 5965 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 5966 r->bottom(), r->end()); 5967 _success = false; 5968 } 5969 return false; 5970 } 5971 bool success() { return _success; } 5972 }; 5973 5974 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5975 bool ret = _young_list->check_list_empty(check_sample); 5976 5977 if (check_heap) { 5978 NoYoungRegionsClosure closure; 5979 heap_region_iterate(&closure); 5980 ret = ret && closure.success(); 5981 } 5982 5983 return ret; 5984 } 5985 5986 class TearDownRegionSetsClosure : public HeapRegionClosure { 5987 private: 5988 OldRegionSet *_old_set; 5989 5990 public: 5991 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { } 5992 5993 bool doHeapRegion(HeapRegion* r) { 5994 if (r->is_empty()) { 5995 // We ignore empty regions, we'll empty the free list afterwards 5996 } else if (r->is_young()) { 5997 // We ignore young regions, we'll empty the young list afterwards 5998 } else if (r->isHumongous()) { 5999 // We ignore humongous regions, we're not tearing down the 6000 // humongous region set 6001 } else { 6002 // The rest should be old 6003 _old_set->remove(r); 6004 } 6005 return false; 6006 } 6007 6008 ~TearDownRegionSetsClosure() { 6009 assert(_old_set->is_empty(), "post-condition"); 6010 } 6011 }; 6012 6013 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6014 assert_at_safepoint(true /* should_be_vm_thread */); 6015 6016 if (!free_list_only) { 6017 TearDownRegionSetsClosure cl(&_old_set); 6018 heap_region_iterate(&cl); 6019 6020 // Need to do this after the heap iteration to be able to 6021 // recognize the young regions and ignore them during the iteration. 6022 _young_list->empty_list(); 6023 } 6024 _free_list.remove_all(); 6025 } 6026 6027 class RebuildRegionSetsClosure : public HeapRegionClosure { 6028 private: 6029 bool _free_list_only; 6030 OldRegionSet* _old_set; 6031 FreeRegionList* _free_list; 6032 size_t _total_used; 6033 6034 public: 6035 RebuildRegionSetsClosure(bool free_list_only, 6036 OldRegionSet* old_set, FreeRegionList* free_list) : 6037 _free_list_only(free_list_only), 6038 _old_set(old_set), _free_list(free_list), _total_used(0) { 6039 assert(_free_list->is_empty(), "pre-condition"); 6040 if (!free_list_only) { 6041 assert(_old_set->is_empty(), "pre-condition"); 6042 } 6043 } 6044 6045 bool doHeapRegion(HeapRegion* r) { 6046 if (r->continuesHumongous()) { 6047 return false; 6048 } 6049 6050 if (r->is_empty()) { 6051 // Add free regions to the free list 6052 _free_list->add_as_tail(r); 6053 } else if (!_free_list_only) { 6054 assert(!r->is_young(), "we should not come across young regions"); 6055 6056 if (r->isHumongous()) { 6057 // We ignore humongous regions, we left the humongous set unchanged 6058 } else { 6059 // The rest should be old, add them to the old set 6060 _old_set->add(r); 6061 } 6062 _total_used += r->used(); 6063 } 6064 6065 return false; 6066 } 6067 6068 size_t total_used() { 6069 return _total_used; 6070 } 6071 }; 6072 6073 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6074 assert_at_safepoint(true /* should_be_vm_thread */); 6075 6076 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list); 6077 heap_region_iterate(&cl); 6078 6079 if (!free_list_only) { 6080 _summary_bytes_used = cl.total_used(); 6081 } 6082 assert(_summary_bytes_used == recalculate_used(), 6083 err_msg("inconsistent _summary_bytes_used, " 6084 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6085 _summary_bytes_used, recalculate_used())); 6086 } 6087 6088 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6089 _refine_cte_cl->set_concurrent(concurrent); 6090 } 6091 6092 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6093 HeapRegion* hr = heap_region_containing(p); 6094 if (hr == NULL) { 6095 return is_in_permanent(p); 6096 } else { 6097 return hr->is_in(p); 6098 } 6099 } 6100 6101 // Methods for the mutator alloc region 6102 6103 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6104 bool force) { 6105 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6106 assert(!force || g1_policy()->can_expand_young_list(), 6107 "if force is true we should be able to expand the young list"); 6108 bool young_list_full = g1_policy()->is_young_list_full(); 6109 if (force || !young_list_full) { 6110 HeapRegion* new_alloc_region = new_region(word_size, 6111 false /* do_expand */); 6112 if (new_alloc_region != NULL) { 6113 set_region_short_lived_locked(new_alloc_region); 6114 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6115 return new_alloc_region; 6116 } 6117 } 6118 return NULL; 6119 } 6120 6121 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6122 size_t allocated_bytes) { 6123 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6124 assert(alloc_region->is_young(), "all mutator alloc regions should be young"); 6125 6126 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6127 _summary_bytes_used += allocated_bytes; 6128 _hr_printer.retire(alloc_region); 6129 // We update the eden sizes here, when the region is retired, 6130 // instead of when it's allocated, since this is the point that its 6131 // used space has been recored in _summary_bytes_used. 6132 g1mm()->update_eden_size(); 6133 } 6134 6135 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, 6136 bool force) { 6137 return _g1h->new_mutator_alloc_region(word_size, force); 6138 } 6139 6140 void G1CollectedHeap::set_par_threads() { 6141 // Don't change the number of workers. Use the value previously set 6142 // in the workgroup. 6143 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6144 int n_workers = workers()->active_workers(); 6145 assert(UseDynamicNumberOfGCThreads || 6146 n_workers == workers()->total_workers(), 6147 "Otherwise should be using the total number of workers"); 6148 if (n_workers == 0) { 6149 assert(false, "Should have been set in prior evacuation pause."); 6150 n_workers = ParallelGCThreads; 6151 workers()->set_active_workers(n_workers); 6152 } 6153 set_par_threads(n_workers); 6154 } 6155 6156 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, 6157 size_t allocated_bytes) { 6158 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); 6159 } 6160 6161 // Methods for the GC alloc regions 6162 6163 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6164 size_t count, 6165 GCAllocPurpose ap) { 6166 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6167 6168 if (count < g1_policy()->max_regions(ap)) { 6169 HeapRegion* new_alloc_region = new_region(word_size, 6170 true /* do_expand */); 6171 if (new_alloc_region != NULL) { 6172 // We really only need to do this for old regions given that we 6173 // should never scan survivors. But it doesn't hurt to do it 6174 // for survivors too. 6175 new_alloc_region->set_saved_mark(); 6176 if (ap == GCAllocForSurvived) { 6177 new_alloc_region->set_survivor(); 6178 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6179 } else { 6180 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6181 } 6182 return new_alloc_region; 6183 } else { 6184 g1_policy()->note_alloc_region_limit_reached(ap); 6185 } 6186 } 6187 return NULL; 6188 } 6189 6190 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6191 size_t allocated_bytes, 6192 GCAllocPurpose ap) { 6193 alloc_region->note_end_of_copying(); 6194 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6195 if (ap == GCAllocForSurvived) { 6196 young_list()->add_survivor_region(alloc_region); 6197 } else { 6198 _old_set.add(alloc_region); 6199 } 6200 _hr_printer.retire(alloc_region); 6201 } 6202 6203 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, 6204 bool force) { 6205 assert(!force, "not supported for GC alloc regions"); 6206 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); 6207 } 6208 6209 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, 6210 size_t allocated_bytes) { 6211 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6212 GCAllocForSurvived); 6213 } 6214 6215 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, 6216 bool force) { 6217 assert(!force, "not supported for GC alloc regions"); 6218 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); 6219 } 6220 6221 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, 6222 size_t allocated_bytes) { 6223 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6224 GCAllocForTenured); 6225 } 6226 // Heap region set verification 6227 6228 class VerifyRegionListsClosure : public HeapRegionClosure { 6229 private: 6230 FreeRegionList* _free_list; 6231 OldRegionSet* _old_set; 6232 HumongousRegionSet* _humongous_set; 6233 size_t _region_count; 6234 6235 public: 6236 VerifyRegionListsClosure(OldRegionSet* old_set, 6237 HumongousRegionSet* humongous_set, 6238 FreeRegionList* free_list) : 6239 _old_set(old_set), _humongous_set(humongous_set), 6240 _free_list(free_list), _region_count(0) { } 6241 6242 size_t region_count() { return _region_count; } 6243 6244 bool doHeapRegion(HeapRegion* hr) { 6245 _region_count += 1; 6246 6247 if (hr->continuesHumongous()) { 6248 return false; 6249 } 6250 6251 if (hr->is_young()) { 6252 // TODO 6253 } else if (hr->startsHumongous()) { 6254 _humongous_set->verify_next_region(hr); 6255 } else if (hr->is_empty()) { 6256 _free_list->verify_next_region(hr); 6257 } else { 6258 _old_set->verify_next_region(hr); 6259 } 6260 return false; 6261 } 6262 }; 6263 6264 HeapRegion* G1CollectedHeap::new_heap_region(size_t hrs_index, 6265 HeapWord* bottom) { 6266 HeapWord* end = bottom + HeapRegion::GrainWords; 6267 MemRegion mr(bottom, end); 6268 assert(_g1_reserved.contains(mr), "invariant"); 6269 // This might return NULL if the allocation fails 6270 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */); 6271 } 6272 6273 void G1CollectedHeap::verify_region_sets() { 6274 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6275 6276 // First, check the explicit lists. 6277 _free_list.verify(); 6278 { 6279 // Given that a concurrent operation might be adding regions to 6280 // the secondary free list we have to take the lock before 6281 // verifying it. 6282 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6283 _secondary_free_list.verify(); 6284 } 6285 _old_set.verify(); 6286 _humongous_set.verify(); 6287 6288 // If a concurrent region freeing operation is in progress it will 6289 // be difficult to correctly attributed any free regions we come 6290 // across to the correct free list given that they might belong to 6291 // one of several (free_list, secondary_free_list, any local lists, 6292 // etc.). So, if that's the case we will skip the rest of the 6293 // verification operation. Alternatively, waiting for the concurrent 6294 // operation to complete will have a non-trivial effect on the GC's 6295 // operation (no concurrent operation will last longer than the 6296 // interval between two calls to verification) and it might hide 6297 // any issues that we would like to catch during testing. 6298 if (free_regions_coming()) { 6299 return; 6300 } 6301 6302 // Make sure we append the secondary_free_list on the free_list so 6303 // that all free regions we will come across can be safely 6304 // attributed to the free_list. 6305 append_secondary_free_list_if_not_empty_with_lock(); 6306 6307 // Finally, make sure that the region accounting in the lists is 6308 // consistent with what we see in the heap. 6309 _old_set.verify_start(); 6310 _humongous_set.verify_start(); 6311 _free_list.verify_start(); 6312 6313 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list); 6314 heap_region_iterate(&cl); 6315 6316 _old_set.verify_end(); 6317 _humongous_set.verify_end(); 6318 _free_list.verify_end(); 6319 }