1 /* 2 * Copyright (c) 2001, 2012, 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/g1EvacFailure.hpp" 36 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 37 #include "gc_implementation/g1/g1Log.hpp" 38 #include "gc_implementation/g1/g1MarkSweep.hpp" 39 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 40 #include "gc_implementation/g1/g1RemSet.inline.hpp" 41 #include "gc_implementation/g1/heapRegion.inline.hpp" 42 #include "gc_implementation/g1/heapRegionRemSet.hpp" 43 #include "gc_implementation/g1/heapRegionSeq.inline.hpp" 44 #include "gc_implementation/g1/vm_operations_g1.hpp" 45 #include "gc_implementation/shared/isGCActiveMark.hpp" 46 #include "memory/gcLocker.inline.hpp" 47 #include "memory/genOopClosures.inline.hpp" 48 #include "memory/generationSpec.hpp" 49 #include "memory/referenceProcessor.hpp" 50 #include "oops/oop.inline.hpp" 51 #include "oops/oop.pcgc.inline.hpp" 52 #include "runtime/aprofiler.hpp" 53 #include "runtime/vmThread.hpp" 54 55 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 56 57 // turn it on so that the contents of the young list (scan-only / 58 // to-be-collected) are printed at "strategic" points before / during 59 // / after the collection --- this is useful for debugging 60 #define YOUNG_LIST_VERBOSE 0 61 // CURRENT STATUS 62 // This file is under construction. Search for "FIXME". 63 64 // INVARIANTS/NOTES 65 // 66 // All allocation activity covered by the G1CollectedHeap interface is 67 // serialized by acquiring the HeapLock. This happens in mem_allocate 68 // and allocate_new_tlab, which are the "entry" points to the 69 // allocation code from the rest of the JVM. (Note that this does not 70 // apply to TLAB allocation, which is not part of this interface: it 71 // is done by clients of this interface.) 72 73 // Notes on implementation of parallelism in different tasks. 74 // 75 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism. 76 // The number of GC workers is passed to heap_region_par_iterate_chunked(). 77 // It does use run_task() which sets _n_workers in the task. 78 // G1ParTask executes g1_process_strong_roots() -> 79 // SharedHeap::process_strong_roots() which calls eventuall to 80 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses 81 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also 82 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap). 83 // 84 85 // Local to this file. 86 87 class RefineCardTableEntryClosure: public CardTableEntryClosure { 88 SuspendibleThreadSet* _sts; 89 G1RemSet* _g1rs; 90 ConcurrentG1Refine* _cg1r; 91 bool _concurrent; 92 public: 93 RefineCardTableEntryClosure(SuspendibleThreadSet* sts, 94 G1RemSet* g1rs, 95 ConcurrentG1Refine* cg1r) : 96 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true) 97 {} 98 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 99 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false); 100 // This path is executed by the concurrent refine or mutator threads, 101 // concurrently, and so we do not care if card_ptr contains references 102 // that point into the collection set. 103 assert(!oops_into_cset, "should be"); 104 105 if (_concurrent && _sts->should_yield()) { 106 // Caller will actually yield. 107 return false; 108 } 109 // Otherwise, we finished successfully; return true. 110 return true; 111 } 112 void set_concurrent(bool b) { _concurrent = b; } 113 }; 114 115 116 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 117 int _calls; 118 G1CollectedHeap* _g1h; 119 CardTableModRefBS* _ctbs; 120 int _histo[256]; 121 public: 122 ClearLoggedCardTableEntryClosure() : 123 _calls(0) 124 { 125 _g1h = G1CollectedHeap::heap(); 126 _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); 127 for (int i = 0; i < 256; i++) _histo[i] = 0; 128 } 129 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 130 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 131 _calls++; 132 unsigned char* ujb = (unsigned char*)card_ptr; 133 int ind = (int)(*ujb); 134 _histo[ind]++; 135 *card_ptr = -1; 136 } 137 return true; 138 } 139 int calls() { return _calls; } 140 void print_histo() { 141 gclog_or_tty->print_cr("Card table value histogram:"); 142 for (int i = 0; i < 256; i++) { 143 if (_histo[i] != 0) { 144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); 145 } 146 } 147 } 148 }; 149 150 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure { 151 int _calls; 152 G1CollectedHeap* _g1h; 153 CardTableModRefBS* _ctbs; 154 public: 155 RedirtyLoggedCardTableEntryClosure() : 156 _calls(0) 157 { 158 _g1h = G1CollectedHeap::heap(); 159 _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); 160 } 161 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 162 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 163 _calls++; 164 *card_ptr = 0; 165 } 166 return true; 167 } 168 int calls() { return _calls; } 169 }; 170 171 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure { 172 public: 173 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 174 *card_ptr = CardTableModRefBS::dirty_card_val(); 175 return true; 176 } 177 }; 178 179 YoungList::YoungList(G1CollectedHeap* g1h) : 180 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 181 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 182 guarantee(check_list_empty(false), "just making sure..."); 183 } 184 185 void YoungList::push_region(HeapRegion *hr) { 186 assert(!hr->is_young(), "should not already be young"); 187 assert(hr->get_next_young_region() == NULL, "cause it should!"); 188 189 hr->set_next_young_region(_head); 190 _head = hr; 191 192 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 193 ++_length; 194 } 195 196 void YoungList::add_survivor_region(HeapRegion* hr) { 197 assert(hr->is_survivor(), "should be flagged as survivor region"); 198 assert(hr->get_next_young_region() == NULL, "cause it should!"); 199 200 hr->set_next_young_region(_survivor_head); 201 if (_survivor_head == NULL) { 202 _survivor_tail = hr; 203 } 204 _survivor_head = hr; 205 ++_survivor_length; 206 } 207 208 void YoungList::empty_list(HeapRegion* list) { 209 while (list != NULL) { 210 HeapRegion* next = list->get_next_young_region(); 211 list->set_next_young_region(NULL); 212 list->uninstall_surv_rate_group(); 213 list->set_not_young(); 214 list = next; 215 } 216 } 217 218 void YoungList::empty_list() { 219 assert(check_list_well_formed(), "young list should be well formed"); 220 221 empty_list(_head); 222 _head = NULL; 223 _length = 0; 224 225 empty_list(_survivor_head); 226 _survivor_head = NULL; 227 _survivor_tail = NULL; 228 _survivor_length = 0; 229 230 _last_sampled_rs_lengths = 0; 231 232 assert(check_list_empty(false), "just making sure..."); 233 } 234 235 bool YoungList::check_list_well_formed() { 236 bool ret = true; 237 238 uint length = 0; 239 HeapRegion* curr = _head; 240 HeapRegion* last = NULL; 241 while (curr != NULL) { 242 if (!curr->is_young()) { 243 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 244 "incorrectly tagged (y: %d, surv: %d)", 245 curr->bottom(), curr->end(), 246 curr->is_young(), curr->is_survivor()); 247 ret = false; 248 } 249 ++length; 250 last = curr; 251 curr = curr->get_next_young_region(); 252 } 253 ret = ret && (length == _length); 254 255 if (!ret) { 256 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 257 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 258 length, _length); 259 } 260 261 return ret; 262 } 263 264 bool YoungList::check_list_empty(bool check_sample) { 265 bool ret = true; 266 267 if (_length != 0) { 268 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 269 _length); 270 ret = false; 271 } 272 if (check_sample && _last_sampled_rs_lengths != 0) { 273 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 274 ret = false; 275 } 276 if (_head != NULL) { 277 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 278 ret = false; 279 } 280 if (!ret) { 281 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 282 } 283 284 return ret; 285 } 286 287 void 288 YoungList::rs_length_sampling_init() { 289 _sampled_rs_lengths = 0; 290 _curr = _head; 291 } 292 293 bool 294 YoungList::rs_length_sampling_more() { 295 return _curr != NULL; 296 } 297 298 void 299 YoungList::rs_length_sampling_next() { 300 assert( _curr != NULL, "invariant" ); 301 size_t rs_length = _curr->rem_set()->occupied(); 302 303 _sampled_rs_lengths += rs_length; 304 305 // The current region may not yet have been added to the 306 // incremental collection set (it gets added when it is 307 // retired as the current allocation region). 308 if (_curr->in_collection_set()) { 309 // Update the collection set policy information for this region 310 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 311 } 312 313 _curr = _curr->get_next_young_region(); 314 if (_curr == NULL) { 315 _last_sampled_rs_lengths = _sampled_rs_lengths; 316 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 317 } 318 } 319 320 void 321 YoungList::reset_auxilary_lists() { 322 guarantee( is_empty(), "young list should be empty" ); 323 assert(check_list_well_formed(), "young list should be well formed"); 324 325 // Add survivor regions to SurvRateGroup. 326 _g1h->g1_policy()->note_start_adding_survivor_regions(); 327 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 328 329 int young_index_in_cset = 0; 330 for (HeapRegion* curr = _survivor_head; 331 curr != NULL; 332 curr = curr->get_next_young_region()) { 333 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 334 335 // The region is a non-empty survivor so let's add it to 336 // the incremental collection set for the next evacuation 337 // pause. 338 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 339 young_index_in_cset += 1; 340 } 341 assert((uint) young_index_in_cset == _survivor_length, "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(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d", 373 HR_FORMAT_PARAMS(curr), 374 curr->prev_top_at_mark_start(), 375 curr->next_top_at_mark_start(), 376 curr->age_in_surv_rate_group_cond()); 377 curr = curr->get_next_young_region(); 378 } 379 } 380 381 gclog_or_tty->print_cr(""); 382 } 383 384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 385 { 386 // Claim the right to put the region on the dirty cards region list 387 // by installing a self pointer. 388 HeapRegion* next = hr->get_next_dirty_cards_region(); 389 if (next == NULL) { 390 HeapRegion* res = (HeapRegion*) 391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 392 NULL); 393 if (res == NULL) { 394 HeapRegion* head; 395 do { 396 // Put the region to the dirty cards region list. 397 head = _dirty_cards_region_list; 398 next = (HeapRegion*) 399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 400 if (next == head) { 401 assert(hr->get_next_dirty_cards_region() == hr, 402 "hr->get_next_dirty_cards_region() != hr"); 403 if (next == NULL) { 404 // The last region in the list points to itself. 405 hr->set_next_dirty_cards_region(hr); 406 } else { 407 hr->set_next_dirty_cards_region(next); 408 } 409 } 410 } while (next != head); 411 } 412 } 413 } 414 415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 416 { 417 HeapRegion* head; 418 HeapRegion* hr; 419 do { 420 head = _dirty_cards_region_list; 421 if (head == NULL) { 422 return NULL; 423 } 424 HeapRegion* new_head = head->get_next_dirty_cards_region(); 425 if (head == new_head) { 426 // The last region. 427 new_head = NULL; 428 } 429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 430 head); 431 } while (hr != head); 432 assert(hr != NULL, "invariant"); 433 hr->set_next_dirty_cards_region(NULL); 434 return hr; 435 } 436 437 void G1CollectedHeap::stop_conc_gc_threads() { 438 _cg1r->stop(); 439 _cmThread->stop(); 440 } 441 442 #ifdef ASSERT 443 // A region is added to the collection set as it is retired 444 // so an address p can point to a region which will be in the 445 // collection set but has not yet been retired. This method 446 // therefore is only accurate during a GC pause after all 447 // regions have been retired. It is used for debugging 448 // to check if an nmethod has references to objects that can 449 // be move during a partial collection. Though it can be 450 // inaccurate, it is sufficient for G1 because the conservative 451 // implementation of is_scavengable() for G1 will indicate that 452 // all nmethods must be scanned during a partial collection. 453 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 454 HeapRegion* hr = heap_region_containing(p); 455 return hr != NULL && hr->in_collection_set(); 456 } 457 #endif 458 459 // Returns true if the reference points to an object that 460 // can move in an incremental collecction. 461 bool G1CollectedHeap::is_scavengable(const void* p) { 462 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 463 G1CollectorPolicy* g1p = g1h->g1_policy(); 464 HeapRegion* hr = heap_region_containing(p); 465 if (hr == NULL) { 466 // null 467 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p)); 468 return false; 469 } else { 470 return !hr->isHumongous(); 471 } 472 } 473 474 void G1CollectedHeap::check_ct_logs_at_safepoint() { 475 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 476 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 477 478 // Count the dirty cards at the start. 479 CountNonCleanMemRegionClosure count1(this); 480 ct_bs->mod_card_iterate(&count1); 481 int orig_count = count1.n(); 482 483 // First clear the logged cards. 484 ClearLoggedCardTableEntryClosure clear; 485 dcqs.set_closure(&clear); 486 dcqs.apply_closure_to_all_completed_buffers(); 487 dcqs.iterate_closure_all_threads(false); 488 clear.print_histo(); 489 490 // Now ensure that there's no dirty cards. 491 CountNonCleanMemRegionClosure count2(this); 492 ct_bs->mod_card_iterate(&count2); 493 if (count2.n() != 0) { 494 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 495 count2.n(), orig_count); 496 } 497 guarantee(count2.n() == 0, "Card table should be clean."); 498 499 RedirtyLoggedCardTableEntryClosure redirty; 500 JavaThread::dirty_card_queue_set().set_closure(&redirty); 501 dcqs.apply_closure_to_all_completed_buffers(); 502 dcqs.iterate_closure_all_threads(false); 503 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 504 clear.calls(), orig_count); 505 guarantee(redirty.calls() == clear.calls(), 506 "Or else mechanism is broken."); 507 508 CountNonCleanMemRegionClosure count3(this); 509 ct_bs->mod_card_iterate(&count3); 510 if (count3.n() != orig_count) { 511 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 512 orig_count, count3.n()); 513 guarantee(count3.n() >= orig_count, "Should have restored them all."); 514 } 515 516 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 517 } 518 519 // Private class members. 520 521 G1CollectedHeap* G1CollectedHeap::_g1h; 522 523 // Private methods. 524 525 HeapRegion* 526 G1CollectedHeap::new_region_try_secondary_free_list() { 527 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 528 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 529 if (!_secondary_free_list.is_empty()) { 530 if (G1ConcRegionFreeingVerbose) { 531 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 532 "secondary_free_list has %u entries", 533 _secondary_free_list.length()); 534 } 535 // It looks as if there are free regions available on the 536 // secondary_free_list. Let's move them to the free_list and try 537 // again to allocate from it. 538 append_secondary_free_list(); 539 540 assert(!_free_list.is_empty(), "if the secondary_free_list was not " 541 "empty we should have moved at least one entry to the free_list"); 542 HeapRegion* res = _free_list.remove_head(); 543 if (G1ConcRegionFreeingVerbose) { 544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 545 "allocated "HR_FORMAT" from secondary_free_list", 546 HR_FORMAT_PARAMS(res)); 547 } 548 return res; 549 } 550 551 // Wait here until we get notifed either when (a) there are no 552 // more free regions coming or (b) some regions have been moved on 553 // the secondary_free_list. 554 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 555 } 556 557 if (G1ConcRegionFreeingVerbose) { 558 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 559 "could not allocate from secondary_free_list"); 560 } 561 return NULL; 562 } 563 564 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) { 565 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords, 566 "the only time we use this to allocate a humongous region is " 567 "when we are allocating a single humongous region"); 568 569 HeapRegion* res; 570 if (G1StressConcRegionFreeing) { 571 if (!_secondary_free_list.is_empty()) { 572 if (G1ConcRegionFreeingVerbose) { 573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 574 "forced to look at the secondary_free_list"); 575 } 576 res = new_region_try_secondary_free_list(); 577 if (res != NULL) { 578 return res; 579 } 580 } 581 } 582 res = _free_list.remove_head_or_null(); 583 if (res == NULL) { 584 if (G1ConcRegionFreeingVerbose) { 585 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 586 "res == NULL, trying the secondary_free_list"); 587 } 588 res = new_region_try_secondary_free_list(); 589 } 590 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 591 // Currently, only attempts to allocate GC alloc regions set 592 // do_expand to true. So, we should only reach here during a 593 // safepoint. If this assumption changes we might have to 594 // reconsider the use of _expand_heap_after_alloc_failure. 595 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 596 597 ergo_verbose1(ErgoHeapSizing, 598 "attempt heap expansion", 599 ergo_format_reason("region allocation request failed") 600 ergo_format_byte("allocation request"), 601 word_size * HeapWordSize); 602 if (expand(word_size * HeapWordSize)) { 603 // Given that expand() succeeded in expanding the heap, and we 604 // always expand the heap by an amount aligned to the heap 605 // region size, the free list should in theory not be empty. So 606 // it would probably be OK to use remove_head(). But the extra 607 // check for NULL is unlikely to be a performance issue here (we 608 // just expanded the heap!) so let's just be conservative and 609 // use remove_head_or_null(). 610 res = _free_list.remove_head_or_null(); 611 } else { 612 _expand_heap_after_alloc_failure = false; 613 } 614 } 615 return res; 616 } 617 618 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions, 619 size_t word_size) { 620 assert(isHumongous(word_size), "word_size should be humongous"); 621 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 622 623 uint first = G1_NULL_HRS_INDEX; 624 if (num_regions == 1) { 625 // Only one region to allocate, no need to go through the slower 626 // path. The caller will attempt the expasion if this fails, so 627 // let's not try to expand here too. 628 HeapRegion* hr = new_region(word_size, false /* do_expand */); 629 if (hr != NULL) { 630 first = hr->hrs_index(); 631 } else { 632 first = G1_NULL_HRS_INDEX; 633 } 634 } else { 635 // We can't allocate humongous regions while cleanupComplete() is 636 // running, since some of the regions we find to be empty might not 637 // yet be added to the free list and it is not straightforward to 638 // know which list they are on so that we can remove them. Note 639 // that we only need to do this if we need to allocate more than 640 // one region to satisfy the current humongous allocation 641 // request. If we are only allocating one region we use the common 642 // region allocation code (see above). 643 wait_while_free_regions_coming(); 644 append_secondary_free_list_if_not_empty_with_lock(); 645 646 if (free_regions() >= num_regions) { 647 first = _hrs.find_contiguous(num_regions); 648 if (first != G1_NULL_HRS_INDEX) { 649 for (uint i = first; i < first + num_regions; ++i) { 650 HeapRegion* hr = region_at(i); 651 assert(hr->is_empty(), "sanity"); 652 assert(is_on_master_free_list(hr), "sanity"); 653 hr->set_pending_removal(true); 654 } 655 _free_list.remove_all_pending(num_regions); 656 } 657 } 658 } 659 return first; 660 } 661 662 HeapWord* 663 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 664 uint num_regions, 665 size_t word_size) { 666 assert(first != G1_NULL_HRS_INDEX, "pre-condition"); 667 assert(isHumongous(word_size), "word_size should be humongous"); 668 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 669 670 // Index of last region in the series + 1. 671 uint last = first + num_regions; 672 673 // We need to initialize the region(s) we just discovered. This is 674 // a bit tricky given that it can happen concurrently with 675 // refinement threads refining cards on these regions and 676 // potentially wanting to refine the BOT as they are scanning 677 // those cards (this can happen shortly after a cleanup; see CR 678 // 6991377). So we have to set up the region(s) carefully and in 679 // a specific order. 680 681 // The word size sum of all the regions we will allocate. 682 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 683 assert(word_size <= word_size_sum, "sanity"); 684 685 // This will be the "starts humongous" region. 686 HeapRegion* first_hr = region_at(first); 687 // The header of the new object will be placed at the bottom of 688 // the first region. 689 HeapWord* new_obj = first_hr->bottom(); 690 // This will be the new end of the first region in the series that 691 // should also match the end of the last region in the seriers. 692 HeapWord* new_end = new_obj + word_size_sum; 693 // This will be the new top of the first region that will reflect 694 // this allocation. 695 HeapWord* new_top = new_obj + word_size; 696 697 // First, we need to zero the header of the space that we will be 698 // allocating. When we update top further down, some refinement 699 // threads might try to scan the region. By zeroing the header we 700 // ensure that any thread that will try to scan the region will 701 // come across the zero klass word and bail out. 702 // 703 // NOTE: It would not have been correct to have used 704 // CollectedHeap::fill_with_object() and make the space look like 705 // an int array. The thread that is doing the allocation will 706 // later update the object header to a potentially different array 707 // type and, for a very short period of time, the klass and length 708 // fields will be inconsistent. This could cause a refinement 709 // thread to calculate the object size incorrectly. 710 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 711 712 // We will set up the first region as "starts humongous". This 713 // will also update the BOT covering all the regions to reflect 714 // that there is a single object that starts at the bottom of the 715 // first region. 716 first_hr->set_startsHumongous(new_top, new_end); 717 718 // Then, if there are any, we will set up the "continues 719 // humongous" regions. 720 HeapRegion* hr = NULL; 721 for (uint i = first + 1; i < last; ++i) { 722 hr = region_at(i); 723 hr->set_continuesHumongous(first_hr); 724 } 725 // If we have "continues humongous" regions (hr != NULL), then the 726 // end of the last one should match new_end. 727 assert(hr == NULL || hr->end() == new_end, "sanity"); 728 729 // Up to this point no concurrent thread would have been able to 730 // do any scanning on any region in this series. All the top 731 // fields still point to bottom, so the intersection between 732 // [bottom,top] and [card_start,card_end] will be empty. Before we 733 // update the top fields, we'll do a storestore to make sure that 734 // no thread sees the update to top before the zeroing of the 735 // object header and the BOT initialization. 736 OrderAccess::storestore(); 737 738 // Now that the BOT and the object header have been initialized, 739 // we can update top of the "starts humongous" region. 740 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 741 "new_top should be in this region"); 742 first_hr->set_top(new_top); 743 if (_hr_printer.is_active()) { 744 HeapWord* bottom = first_hr->bottom(); 745 HeapWord* end = first_hr->orig_end(); 746 if ((first + 1) == last) { 747 // the series has a single humongous region 748 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 749 } else { 750 // the series has more than one humongous regions 751 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 752 } 753 } 754 755 // Now, we will update the top fields of the "continues humongous" 756 // regions. The reason we need to do this is that, otherwise, 757 // these regions would look empty and this will confuse parts of 758 // G1. For example, the code that looks for a consecutive number 759 // of empty regions will consider them empty and try to 760 // re-allocate them. We can extend is_empty() to also include 761 // !continuesHumongous(), but it is easier to just update the top 762 // fields here. The way we set top for all regions (i.e., top == 763 // end for all regions but the last one, top == new_top for the 764 // last one) is actually used when we will free up the humongous 765 // region in free_humongous_region(). 766 hr = NULL; 767 for (uint i = first + 1; i < last; ++i) { 768 hr = region_at(i); 769 if ((i + 1) == last) { 770 // last continues humongous region 771 assert(hr->bottom() < new_top && new_top <= hr->end(), 772 "new_top should fall on this region"); 773 hr->set_top(new_top); 774 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 775 } else { 776 // not last one 777 assert(new_top > hr->end(), "new_top should be above this region"); 778 hr->set_top(hr->end()); 779 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 780 } 781 } 782 // If we have continues humongous regions (hr != NULL), then the 783 // end of the last one should match new_end and its top should 784 // match new_top. 785 assert(hr == NULL || 786 (hr->end() == new_end && hr->top() == new_top), "sanity"); 787 788 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 789 _summary_bytes_used += first_hr->used(); 790 _humongous_set.add(first_hr); 791 792 return new_obj; 793 } 794 795 // If could fit into free regions w/o expansion, try. 796 // Otherwise, if can expand, do so. 797 // Otherwise, if using ex regions might help, try with ex given back. 798 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 799 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 800 801 verify_region_sets_optional(); 802 803 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords); 804 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords); 805 uint x_num = expansion_regions(); 806 uint fs = _hrs.free_suffix(); 807 uint first = humongous_obj_allocate_find_first(num_regions, word_size); 808 if (first == G1_NULL_HRS_INDEX) { 809 // The only thing we can do now is attempt expansion. 810 if (fs + x_num >= num_regions) { 811 // If the number of regions we're trying to allocate for this 812 // object is at most the number of regions in the free suffix, 813 // then the call to humongous_obj_allocate_find_first() above 814 // should have succeeded and we wouldn't be here. 815 // 816 // We should only be trying to expand when the free suffix is 817 // not sufficient for the object _and_ we have some expansion 818 // room available. 819 assert(num_regions > fs, "earlier allocation should have succeeded"); 820 821 ergo_verbose1(ErgoHeapSizing, 822 "attempt heap expansion", 823 ergo_format_reason("humongous allocation request failed") 824 ergo_format_byte("allocation request"), 825 word_size * HeapWordSize); 826 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) { 827 // Even though the heap was expanded, it might not have 828 // reached the desired size. So, we cannot assume that the 829 // allocation will succeed. 830 first = humongous_obj_allocate_find_first(num_regions, word_size); 831 } 832 } 833 } 834 835 HeapWord* result = NULL; 836 if (first != G1_NULL_HRS_INDEX) { 837 result = 838 humongous_obj_allocate_initialize_regions(first, num_regions, word_size); 839 assert(result != NULL, "it should always return a valid result"); 840 841 // A successful humongous object allocation changes the used space 842 // information of the old generation so we need to recalculate the 843 // sizes and update the jstat counters here. 844 g1mm()->update_sizes(); 845 } 846 847 verify_region_sets_optional(); 848 849 return result; 850 } 851 852 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 853 assert_heap_not_locked_and_not_at_safepoint(); 854 assert(!isHumongous(word_size), "we do not allow humongous TLABs"); 855 856 unsigned int dummy_gc_count_before; 857 return attempt_allocation(word_size, &dummy_gc_count_before); 858 } 859 860 HeapWord* 861 G1CollectedHeap::mem_allocate(size_t word_size, 862 bool* gc_overhead_limit_was_exceeded) { 863 assert_heap_not_locked_and_not_at_safepoint(); 864 865 // Loop until the allocation is satisified, or unsatisfied after GC. 866 for (int try_count = 1; /* we'll return */; try_count += 1) { 867 unsigned int gc_count_before; 868 869 HeapWord* result = NULL; 870 if (!isHumongous(word_size)) { 871 result = attempt_allocation(word_size, &gc_count_before); 872 } else { 873 result = attempt_allocation_humongous(word_size, &gc_count_before); 874 } 875 if (result != NULL) { 876 return result; 877 } 878 879 // Create the garbage collection operation... 880 VM_G1CollectForAllocation op(gc_count_before, word_size); 881 // ...and get the VM thread to execute it. 882 VMThread::execute(&op); 883 884 if (op.prologue_succeeded() && op.pause_succeeded()) { 885 // If the operation was successful we'll return the result even 886 // if it is NULL. If the allocation attempt failed immediately 887 // after a Full GC, it's unlikely we'll be able to allocate now. 888 HeapWord* result = op.result(); 889 if (result != NULL && !isHumongous(word_size)) { 890 // Allocations that take place on VM operations do not do any 891 // card dirtying and we have to do it here. We only have to do 892 // this for non-humongous allocations, though. 893 dirty_young_block(result, word_size); 894 } 895 return result; 896 } else { 897 assert(op.result() == NULL, 898 "the result should be NULL if the VM op did not succeed"); 899 } 900 901 // Give a warning if we seem to be looping forever. 902 if ((QueuedAllocationWarningCount > 0) && 903 (try_count % QueuedAllocationWarningCount == 0)) { 904 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 905 } 906 } 907 908 ShouldNotReachHere(); 909 return NULL; 910 } 911 912 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 913 unsigned int *gc_count_before_ret) { 914 // Make sure you read the note in attempt_allocation_humongous(). 915 916 assert_heap_not_locked_and_not_at_safepoint(); 917 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 918 "be called for humongous allocation requests"); 919 920 // We should only get here after the first-level allocation attempt 921 // (attempt_allocation()) failed to allocate. 922 923 // We will loop until a) we manage to successfully perform the 924 // allocation or b) we successfully schedule a collection which 925 // fails to perform the allocation. b) is the only case when we'll 926 // return NULL. 927 HeapWord* result = NULL; 928 for (int try_count = 1; /* we'll return */; try_count += 1) { 929 bool should_try_gc; 930 unsigned int gc_count_before; 931 932 { 933 MutexLockerEx x(Heap_lock); 934 935 result = _mutator_alloc_region.attempt_allocation_locked(word_size, 936 false /* bot_updates */); 937 if (result != NULL) { 938 return result; 939 } 940 941 // If we reach here, attempt_allocation_locked() above failed to 942 // allocate a new region. So the mutator alloc region should be NULL. 943 assert(_mutator_alloc_region.get() == NULL, "only way to get here"); 944 945 if (GC_locker::is_active_and_needs_gc()) { 946 if (g1_policy()->can_expand_young_list()) { 947 // No need for an ergo verbose message here, 948 // can_expand_young_list() does this when it returns true. 949 result = _mutator_alloc_region.attempt_allocation_force(word_size, 950 false /* bot_updates */); 951 if (result != NULL) { 952 return result; 953 } 954 } 955 should_try_gc = false; 956 } else { 957 // The GCLocker may not be active but the GCLocker initiated 958 // GC may not yet have been performed (GCLocker::needs_gc() 959 // returns true). In this case we do not try this GC and 960 // wait until the GCLocker initiated GC is performed, and 961 // then retry the allocation. 962 if (GC_locker::needs_gc()) { 963 should_try_gc = false; 964 } else { 965 // Read the GC count while still holding the Heap_lock. 966 gc_count_before = total_collections(); 967 should_try_gc = true; 968 } 969 } 970 } 971 972 if (should_try_gc) { 973 bool succeeded; 974 result = do_collection_pause(word_size, gc_count_before, &succeeded); 975 if (result != NULL) { 976 assert(succeeded, "only way to get back a non-NULL result"); 977 return result; 978 } 979 980 if (succeeded) { 981 // If we get here we successfully scheduled a collection which 982 // failed to allocate. No point in trying to allocate 983 // further. We'll just return NULL. 984 MutexLockerEx x(Heap_lock); 985 *gc_count_before_ret = total_collections(); 986 return NULL; 987 } 988 } else { 989 // The GCLocker is either active or the GCLocker initiated 990 // GC has not yet been performed. Stall until it is and 991 // then retry the allocation. 992 GC_locker::stall_until_clear(); 993 } 994 995 // We can reach here if we were unsuccessul in scheduling a 996 // collection (because another thread beat us to it) or if we were 997 // stalled due to the GC locker. In either can we should retry the 998 // allocation attempt in case another thread successfully 999 // performed a collection and reclaimed enough space. We do the 1000 // first attempt (without holding the Heap_lock) here and the 1001 // follow-on attempt will be at the start of the next loop 1002 // iteration (after taking the Heap_lock). 1003 result = _mutator_alloc_region.attempt_allocation(word_size, 1004 false /* bot_updates */); 1005 if (result != NULL) { 1006 return result; 1007 } 1008 1009 // Give a warning if we seem to be looping forever. 1010 if ((QueuedAllocationWarningCount > 0) && 1011 (try_count % QueuedAllocationWarningCount == 0)) { 1012 warning("G1CollectedHeap::attempt_allocation_slow() " 1013 "retries %d times", try_count); 1014 } 1015 } 1016 1017 ShouldNotReachHere(); 1018 return NULL; 1019 } 1020 1021 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1022 unsigned int * gc_count_before_ret) { 1023 // The structure of this method has a lot of similarities to 1024 // attempt_allocation_slow(). The reason these two were not merged 1025 // into a single one is that such a method would require several "if 1026 // allocation is not humongous do this, otherwise do that" 1027 // conditional paths which would obscure its flow. In fact, an early 1028 // version of this code did use a unified method which was harder to 1029 // follow and, as a result, it had subtle bugs that were hard to 1030 // track down. So keeping these two methods separate allows each to 1031 // be more readable. It will be good to keep these two in sync as 1032 // much as possible. 1033 1034 assert_heap_not_locked_and_not_at_safepoint(); 1035 assert(isHumongous(word_size), "attempt_allocation_humongous() " 1036 "should only be called for humongous allocations"); 1037 1038 // Humongous objects can exhaust the heap quickly, so we should check if we 1039 // need to start a marking cycle at each humongous object allocation. We do 1040 // the check before we do the actual allocation. The reason for doing it 1041 // before the allocation is that we avoid having to keep track of the newly 1042 // allocated memory while we do a GC. 1043 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1044 word_size)) { 1045 collect(GCCause::_g1_humongous_allocation); 1046 } 1047 1048 // We will loop until a) we manage to successfully perform the 1049 // allocation or b) we successfully schedule a collection which 1050 // fails to perform the allocation. b) is the only case when we'll 1051 // return NULL. 1052 HeapWord* result = NULL; 1053 for (int try_count = 1; /* we'll return */; try_count += 1) { 1054 bool should_try_gc; 1055 unsigned int gc_count_before; 1056 1057 { 1058 MutexLockerEx x(Heap_lock); 1059 1060 // Given that humongous objects are not allocated in young 1061 // regions, we'll first try to do the allocation without doing a 1062 // collection hoping that there's enough space in the heap. 1063 result = humongous_obj_allocate(word_size); 1064 if (result != NULL) { 1065 return result; 1066 } 1067 1068 if (GC_locker::is_active_and_needs_gc()) { 1069 should_try_gc = false; 1070 } else { 1071 // The GCLocker may not be active but the GCLocker initiated 1072 // GC may not yet have been performed (GCLocker::needs_gc() 1073 // returns true). In this case we do not try this GC and 1074 // wait until the GCLocker initiated GC is performed, and 1075 // then retry the allocation. 1076 if (GC_locker::needs_gc()) { 1077 should_try_gc = false; 1078 } else { 1079 // Read the GC count while still holding the Heap_lock. 1080 gc_count_before = total_collections(); 1081 should_try_gc = true; 1082 } 1083 } 1084 } 1085 1086 if (should_try_gc) { 1087 // If we failed to allocate the humongous object, we should try to 1088 // do a collection pause (if we're allowed) in case it reclaims 1089 // enough space for the allocation to succeed after the pause. 1090 1091 bool succeeded; 1092 result = do_collection_pause(word_size, gc_count_before, &succeeded); 1093 if (result != NULL) { 1094 assert(succeeded, "only way to get back a non-NULL result"); 1095 return result; 1096 } 1097 1098 if (succeeded) { 1099 // If we get here we successfully scheduled a collection which 1100 // failed to allocate. No point in trying to allocate 1101 // further. We'll just return NULL. 1102 MutexLockerEx x(Heap_lock); 1103 *gc_count_before_ret = total_collections(); 1104 return NULL; 1105 } 1106 } else { 1107 // The GCLocker is either active or the GCLocker initiated 1108 // GC has not yet been performed. Stall until it is and 1109 // then retry the allocation. 1110 GC_locker::stall_until_clear(); 1111 } 1112 1113 // We can reach here if we were unsuccessul in scheduling a 1114 // collection (because another thread beat us to it) or if we were 1115 // stalled due to the GC locker. In either can we should retry the 1116 // allocation attempt in case another thread successfully 1117 // performed a collection and reclaimed enough space. Give a 1118 // warning if we seem to be looping forever. 1119 1120 if ((QueuedAllocationWarningCount > 0) && 1121 (try_count % QueuedAllocationWarningCount == 0)) { 1122 warning("G1CollectedHeap::attempt_allocation_humongous() " 1123 "retries %d times", try_count); 1124 } 1125 } 1126 1127 ShouldNotReachHere(); 1128 return NULL; 1129 } 1130 1131 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1132 bool expect_null_mutator_alloc_region) { 1133 assert_at_safepoint(true /* should_be_vm_thread */); 1134 assert(_mutator_alloc_region.get() == NULL || 1135 !expect_null_mutator_alloc_region, 1136 "the current alloc region was unexpectedly found to be non-NULL"); 1137 1138 if (!isHumongous(word_size)) { 1139 return _mutator_alloc_region.attempt_allocation_locked(word_size, 1140 false /* bot_updates */); 1141 } else { 1142 HeapWord* result = humongous_obj_allocate(word_size); 1143 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1144 g1_policy()->set_initiate_conc_mark_if_possible(); 1145 } 1146 return result; 1147 } 1148 1149 ShouldNotReachHere(); 1150 } 1151 1152 class PostMCRemSetClearClosure: public HeapRegionClosure { 1153 G1CollectedHeap* _g1h; 1154 ModRefBarrierSet* _mr_bs; 1155 public: 1156 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1157 _g1h(g1h), _mr_bs(mr_bs) { } 1158 bool doHeapRegion(HeapRegion* r) { 1159 if (r->continuesHumongous()) { 1160 return false; 1161 } 1162 _g1h->reset_gc_time_stamps(r); 1163 HeapRegionRemSet* hrrs = r->rem_set(); 1164 if (hrrs != NULL) hrrs->clear(); 1165 // You might think here that we could clear just the cards 1166 // corresponding to the used region. But no: if we leave a dirty card 1167 // in a region we might allocate into, then it would prevent that card 1168 // from being enqueued, and cause it to be missed. 1169 // Re: the performance cost: we shouldn't be doing full GC anyway! 1170 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1171 return false; 1172 } 1173 }; 1174 1175 void G1CollectedHeap::clear_rsets_post_compaction() { 1176 PostMCRemSetClearClosure rs_clear(this, mr_bs()); 1177 heap_region_iterate(&rs_clear); 1178 } 1179 1180 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1181 G1CollectedHeap* _g1h; 1182 UpdateRSOopClosure _cl; 1183 int _worker_i; 1184 public: 1185 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1186 _cl(g1->g1_rem_set(), worker_i), 1187 _worker_i(worker_i), 1188 _g1h(g1) 1189 { } 1190 1191 bool doHeapRegion(HeapRegion* r) { 1192 if (!r->continuesHumongous()) { 1193 _cl.set_from(r); 1194 r->oop_iterate(&_cl); 1195 } 1196 return false; 1197 } 1198 }; 1199 1200 class ParRebuildRSTask: public AbstractGangTask { 1201 G1CollectedHeap* _g1; 1202 public: 1203 ParRebuildRSTask(G1CollectedHeap* g1) 1204 : AbstractGangTask("ParRebuildRSTask"), 1205 _g1(g1) 1206 { } 1207 1208 void work(uint worker_id) { 1209 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1210 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id, 1211 _g1->workers()->active_workers(), 1212 HeapRegion::RebuildRSClaimValue); 1213 } 1214 }; 1215 1216 class PostCompactionPrinterClosure: public HeapRegionClosure { 1217 private: 1218 G1HRPrinter* _hr_printer; 1219 public: 1220 bool doHeapRegion(HeapRegion* hr) { 1221 assert(!hr->is_young(), "not expecting to find young regions"); 1222 // We only generate output for non-empty regions. 1223 if (!hr->is_empty()) { 1224 if (!hr->isHumongous()) { 1225 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1226 } else if (hr->startsHumongous()) { 1227 if (hr->region_num() == 1) { 1228 // single humongous region 1229 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1230 } else { 1231 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1232 } 1233 } else { 1234 assert(hr->continuesHumongous(), "only way to get here"); 1235 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1236 } 1237 } 1238 return false; 1239 } 1240 1241 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1242 : _hr_printer(hr_printer) { } 1243 }; 1244 1245 void G1CollectedHeap::print_hrs_post_compaction() { 1246 PostCompactionPrinterClosure cl(hr_printer()); 1247 heap_region_iterate(&cl); 1248 } 1249 1250 double G1CollectedHeap::verify(bool guard, const char* msg) { 1251 double verify_time_ms = 0.0; 1252 1253 if (guard && total_collections() >= VerifyGCStartAt) { 1254 double verify_start = os::elapsedTime(); 1255 HandleMark hm; // Discard invalid handles created during verification 1256 gclog_or_tty->print(msg); 1257 prepare_for_verify(); 1258 Universe::verify(false /* silent */, VerifyOption_G1UsePrevMarking); 1259 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 1260 } 1261 1262 return verify_time_ms; 1263 } 1264 1265 void G1CollectedHeap::verify_before_gc() { 1266 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 1267 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 1268 } 1269 1270 void G1CollectedHeap::verify_after_gc() { 1271 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 1272 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 1273 } 1274 1275 bool G1CollectedHeap::do_collection(bool explicit_gc, 1276 bool clear_all_soft_refs, 1277 size_t word_size) { 1278 assert_at_safepoint(true /* should_be_vm_thread */); 1279 1280 if (GC_locker::check_active_before_gc()) { 1281 return false; 1282 } 1283 1284 SvcGCMarker sgcm(SvcGCMarker::FULL); 1285 ResourceMark rm; 1286 1287 print_heap_before_gc(); 1288 1289 size_t metadata_prev_used = MetaspaceAux::used_in_bytes(); 1290 1291 HRSPhaseSetter x(HRSPhaseFullGC); 1292 verify_region_sets_optional(); 1293 1294 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1295 collector_policy()->should_clear_all_soft_refs(); 1296 1297 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1298 1299 { 1300 IsGCActiveMark x; 1301 1302 // Timing 1303 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1304 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps); 1305 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1306 1307 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty); 1308 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1309 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1310 1311 double start = os::elapsedTime(); 1312 g1_policy()->record_full_collection_start(); 1313 1314 // Note: When we have a more flexible GC logging framework that 1315 // allows us to add optional attributes to a GC log record we 1316 // could consider timing and reporting how long we wait in the 1317 // following two methods. 1318 wait_while_free_regions_coming(); 1319 // If we start the compaction before the CM threads finish 1320 // scanning the root regions we might trip them over as we'll 1321 // be moving objects / updating references. So let's wait until 1322 // they are done. By telling them to abort, they should complete 1323 // early. 1324 _cm->root_regions()->abort(); 1325 _cm->root_regions()->wait_until_scan_finished(); 1326 append_secondary_free_list_if_not_empty_with_lock(); 1327 1328 gc_prologue(true); 1329 increment_total_collections(true /* full gc */); 1330 increment_old_marking_cycles_started(); 1331 1332 size_t g1h_prev_used = used(); 1333 assert(used() == recalculate_used(), "Should be equal"); 1334 1335 verify_before_gc(); 1336 1337 pre_full_gc_dump(); 1338 1339 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1340 1341 // Disable discovery and empty the discovered lists 1342 // for the CM ref processor. 1343 ref_processor_cm()->disable_discovery(); 1344 ref_processor_cm()->abandon_partial_discovery(); 1345 ref_processor_cm()->verify_no_references_recorded(); 1346 1347 // Abandon current iterations of concurrent marking and concurrent 1348 // refinement, if any are in progress. We have to do this before 1349 // wait_until_scan_finished() below. 1350 concurrent_mark()->abort(); 1351 1352 // Make sure we'll choose a new allocation region afterwards. 1353 release_mutator_alloc_region(); 1354 abandon_gc_alloc_regions(); 1355 g1_rem_set()->cleanupHRRS(); 1356 1357 // We should call this after we retire any currently active alloc 1358 // regions so that all the ALLOC / RETIRE events are generated 1359 // before the start GC event. 1360 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1361 1362 // We may have added regions to the current incremental collection 1363 // set between the last GC or pause and now. We need to clear the 1364 // incremental collection set and then start rebuilding it afresh 1365 // after this full GC. 1366 abandon_collection_set(g1_policy()->inc_cset_head()); 1367 g1_policy()->clear_incremental_cset(); 1368 g1_policy()->stop_incremental_cset_building(); 1369 1370 tear_down_region_sets(false /* free_list_only */); 1371 g1_policy()->set_gcs_are_young(true); 1372 1373 // See the comments in g1CollectedHeap.hpp and 1374 // G1CollectedHeap::ref_processing_init() about 1375 // how reference processing currently works in G1. 1376 1377 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1378 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1379 1380 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1381 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1382 1383 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1384 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1385 1386 // Do collection work 1387 { 1388 HandleMark hm; // Discard invalid handles created during gc 1389 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1390 } 1391 1392 assert(free_regions() == 0, "we should not have added any free regions"); 1393 rebuild_region_sets(false /* free_list_only */); 1394 1395 // Enqueue any discovered reference objects that have 1396 // not been removed from the discovered lists. 1397 ref_processor_stw()->enqueue_discovered_references(); 1398 1399 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1400 1401 MemoryService::track_memory_usage(); 1402 1403 verify_after_gc(); 1404 1405 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1406 ref_processor_stw()->verify_no_references_recorded(); 1407 1408 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1409 ClassLoaderDataGraph::purge(); 1410 1411 // Note: since we've just done a full GC, concurrent 1412 // marking is no longer active. Therefore we need not 1413 // re-enable reference discovery for the CM ref processor. 1414 // That will be done at the start of the next marking cycle. 1415 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1416 ref_processor_cm()->verify_no_references_recorded(); 1417 1418 reset_gc_time_stamp(); 1419 // Since everything potentially moved, we will clear all remembered 1420 // sets, and clear all cards. Later we will rebuild remebered 1421 // sets. We will also reset the GC time stamps of the regions. 1422 clear_rsets_post_compaction(); 1423 check_gc_time_stamps(); 1424 1425 // Resize the heap if necessary. 1426 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1427 1428 if (_hr_printer.is_active()) { 1429 // We should do this after we potentially resize the heap so 1430 // that all the COMMIT / UNCOMMIT events are generated before 1431 // the end GC event. 1432 1433 print_hrs_post_compaction(); 1434 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1435 } 1436 1437 if (_cg1r->use_cache()) { 1438 _cg1r->clear_and_record_card_counts(); 1439 _cg1r->clear_hot_cache(); 1440 } 1441 1442 // Rebuild remembered sets of all regions. 1443 if (G1CollectedHeap::use_parallel_gc_threads()) { 1444 uint n_workers = 1445 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1446 workers()->active_workers(), 1447 Threads::number_of_non_daemon_threads()); 1448 assert(UseDynamicNumberOfGCThreads || 1449 n_workers == workers()->total_workers(), 1450 "If not dynamic should be using all the workers"); 1451 workers()->set_active_workers(n_workers); 1452 // Set parallel threads in the heap (_n_par_threads) only 1453 // before a parallel phase and always reset it to 0 after 1454 // the phase so that the number of parallel threads does 1455 // no get carried forward to a serial phase where there 1456 // may be code that is "possibly_parallel". 1457 set_par_threads(n_workers); 1458 1459 ParRebuildRSTask rebuild_rs_task(this); 1460 assert(check_heap_region_claim_values( 1461 HeapRegion::InitialClaimValue), "sanity check"); 1462 assert(UseDynamicNumberOfGCThreads || 1463 workers()->active_workers() == workers()->total_workers(), 1464 "Unless dynamic should use total workers"); 1465 // Use the most recent number of active workers 1466 assert(workers()->active_workers() > 0, 1467 "Active workers not properly set"); 1468 set_par_threads(workers()->active_workers()); 1469 workers()->run_task(&rebuild_rs_task); 1470 set_par_threads(0); 1471 assert(check_heap_region_claim_values( 1472 HeapRegion::RebuildRSClaimValue), "sanity check"); 1473 reset_heap_region_claim_values(); 1474 } else { 1475 RebuildRSOutOfRegionClosure rebuild_rs(this); 1476 heap_region_iterate(&rebuild_rs); 1477 } 1478 1479 if (G1Log::fine()) { 1480 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity()); 1481 } 1482 1483 if (true) { // FIXME 1484 MetaspaceGC::compute_new_size(); 1485 } 1486 1487 // Start a new incremental collection set for the next pause 1488 assert(g1_policy()->collection_set() == NULL, "must be"); 1489 g1_policy()->start_incremental_cset_building(); 1490 1491 // Clear the _cset_fast_test bitmap in anticipation of adding 1492 // regions to the incremental collection set for the next 1493 // evacuation pause. 1494 clear_cset_fast_test(); 1495 1496 init_mutator_alloc_region(); 1497 1498 double end = os::elapsedTime(); 1499 g1_policy()->record_full_collection_end(); 1500 1501 #ifdef TRACESPINNING 1502 ParallelTaskTerminator::print_termination_counts(); 1503 #endif 1504 1505 gc_epilogue(true); 1506 1507 // Discard all rset updates 1508 JavaThread::dirty_card_queue_set().abandon_logs(); 1509 assert(!G1DeferredRSUpdate 1510 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); 1511 1512 _young_list->reset_sampled_info(); 1513 // At this point there should be no regions in the 1514 // entire heap tagged as young. 1515 assert( check_young_list_empty(true /* check_heap */), 1516 "young list should be empty at this point"); 1517 1518 // Update the number of full collections that have been completed. 1519 increment_old_marking_cycles_completed(false /* concurrent */); 1520 1521 _hrs.verify_optional(); 1522 verify_region_sets_optional(); 1523 1524 print_heap_after_gc(); 1525 1526 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1527 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1528 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1529 // before any GC notifications are raised. 1530 g1mm()->update_sizes(); 1531 } 1532 1533 post_full_gc_dump(); 1534 1535 return true; 1536 } 1537 1538 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1539 // do_collection() will return whether it succeeded in performing 1540 // the GC. Currently, there is no facility on the 1541 // do_full_collection() API to notify the caller than the collection 1542 // did not succeed (e.g., because it was locked out by the GC 1543 // locker). So, right now, we'll ignore the return value. 1544 bool dummy = do_collection(true, /* explicit_gc */ 1545 clear_all_soft_refs, 1546 0 /* word_size */); 1547 } 1548 1549 // This code is mostly copied from TenuredGeneration. 1550 void 1551 G1CollectedHeap:: 1552 resize_if_necessary_after_full_collection(size_t word_size) { 1553 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check"); 1554 1555 // Include the current allocation, if any, and bytes that will be 1556 // pre-allocated to support collections, as "used". 1557 const size_t used_after_gc = used(); 1558 const size_t capacity_after_gc = capacity(); 1559 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1560 1561 // This is enforced in arguments.cpp. 1562 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1563 "otherwise the code below doesn't make sense"); 1564 1565 // We don't have floating point command-line arguments 1566 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1567 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1568 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1569 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1570 1571 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1572 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1573 1574 // We have to be careful here as these two calculations can overflow 1575 // 32-bit size_t's. 1576 double used_after_gc_d = (double) used_after_gc; 1577 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1578 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1579 1580 // Let's make sure that they are both under the max heap size, which 1581 // by default will make them fit into a size_t. 1582 double desired_capacity_upper_bound = (double) max_heap_size; 1583 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1584 desired_capacity_upper_bound); 1585 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1586 desired_capacity_upper_bound); 1587 1588 // We can now safely turn them into size_t's. 1589 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1590 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1591 1592 // This assert only makes sense here, before we adjust them 1593 // with respect to the min and max heap size. 1594 assert(minimum_desired_capacity <= maximum_desired_capacity, 1595 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1596 "maximum_desired_capacity = "SIZE_FORMAT, 1597 minimum_desired_capacity, maximum_desired_capacity)); 1598 1599 // Should not be greater than the heap max size. No need to adjust 1600 // it with respect to the heap min size as it's a lower bound (i.e., 1601 // we'll try to make the capacity larger than it, not smaller). 1602 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1603 // Should not be less than the heap min size. No need to adjust it 1604 // with respect to the heap max size as it's an upper bound (i.e., 1605 // we'll try to make the capacity smaller than it, not greater). 1606 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1607 1608 if (capacity_after_gc < minimum_desired_capacity) { 1609 // Don't expand unless it's significant 1610 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1611 ergo_verbose4(ErgoHeapSizing, 1612 "attempt heap expansion", 1613 ergo_format_reason("capacity lower than " 1614 "min desired capacity after Full GC") 1615 ergo_format_byte("capacity") 1616 ergo_format_byte("occupancy") 1617 ergo_format_byte_perc("min desired capacity"), 1618 capacity_after_gc, used_after_gc, 1619 minimum_desired_capacity, (double) MinHeapFreeRatio); 1620 expand(expand_bytes); 1621 1622 // No expansion, now see if we want to shrink 1623 } else if (capacity_after_gc > maximum_desired_capacity) { 1624 // Capacity too large, compute shrinking size 1625 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1626 ergo_verbose4(ErgoHeapSizing, 1627 "attempt heap shrinking", 1628 ergo_format_reason("capacity higher than " 1629 "max desired capacity after Full GC") 1630 ergo_format_byte("capacity") 1631 ergo_format_byte("occupancy") 1632 ergo_format_byte_perc("max desired capacity"), 1633 capacity_after_gc, used_after_gc, 1634 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1635 shrink(shrink_bytes); 1636 } 1637 } 1638 1639 1640 HeapWord* 1641 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1642 bool* succeeded) { 1643 assert_at_safepoint(true /* should_be_vm_thread */); 1644 1645 *succeeded = true; 1646 // Let's attempt the allocation first. 1647 HeapWord* result = 1648 attempt_allocation_at_safepoint(word_size, 1649 false /* expect_null_mutator_alloc_region */); 1650 if (result != NULL) { 1651 assert(*succeeded, "sanity"); 1652 return result; 1653 } 1654 1655 // In a G1 heap, we're supposed to keep allocation from failing by 1656 // incremental pauses. Therefore, at least for now, we'll favor 1657 // expansion over collection. (This might change in the future if we can 1658 // do something smarter than full collection to satisfy a failed alloc.) 1659 result = expand_and_allocate(word_size); 1660 if (result != NULL) { 1661 assert(*succeeded, "sanity"); 1662 return result; 1663 } 1664 1665 // Expansion didn't work, we'll try to do a Full GC. 1666 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1667 false, /* clear_all_soft_refs */ 1668 word_size); 1669 if (!gc_succeeded) { 1670 *succeeded = false; 1671 return NULL; 1672 } 1673 1674 // Retry the allocation 1675 result = attempt_allocation_at_safepoint(word_size, 1676 true /* expect_null_mutator_alloc_region */); 1677 if (result != NULL) { 1678 assert(*succeeded, "sanity"); 1679 return result; 1680 } 1681 1682 // Then, try a Full GC that will collect all soft references. 1683 gc_succeeded = do_collection(false, /* explicit_gc */ 1684 true, /* clear_all_soft_refs */ 1685 word_size); 1686 if (!gc_succeeded) { 1687 *succeeded = false; 1688 return NULL; 1689 } 1690 1691 // Retry the allocation once more 1692 result = attempt_allocation_at_safepoint(word_size, 1693 true /* expect_null_mutator_alloc_region */); 1694 if (result != NULL) { 1695 assert(*succeeded, "sanity"); 1696 return result; 1697 } 1698 1699 assert(!collector_policy()->should_clear_all_soft_refs(), 1700 "Flag should have been handled and cleared prior to this point"); 1701 1702 // What else? We might try synchronous finalization later. If the total 1703 // space available is large enough for the allocation, then a more 1704 // complete compaction phase than we've tried so far might be 1705 // appropriate. 1706 assert(*succeeded, "sanity"); 1707 return NULL; 1708 } 1709 1710 // Attempting to expand the heap sufficiently 1711 // to support an allocation of the given "word_size". If 1712 // successful, perform the allocation and return the address of the 1713 // allocated block, or else "NULL". 1714 1715 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1716 assert_at_safepoint(true /* should_be_vm_thread */); 1717 1718 verify_region_sets_optional(); 1719 1720 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1721 ergo_verbose1(ErgoHeapSizing, 1722 "attempt heap expansion", 1723 ergo_format_reason("allocation request failed") 1724 ergo_format_byte("allocation request"), 1725 word_size * HeapWordSize); 1726 if (expand(expand_bytes)) { 1727 _hrs.verify_optional(); 1728 verify_region_sets_optional(); 1729 return attempt_allocation_at_safepoint(word_size, 1730 false /* expect_null_mutator_alloc_region */); 1731 } 1732 return NULL; 1733 } 1734 1735 void G1CollectedHeap::update_committed_space(HeapWord* old_end, 1736 HeapWord* new_end) { 1737 assert(old_end != new_end, "don't call this otherwise"); 1738 assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); 1739 1740 // Update the committed mem region. 1741 _g1_committed.set_end(new_end); 1742 // Tell the card table about the update. 1743 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); 1744 // Tell the BOT about the update. 1745 _bot_shared->resize(_g1_committed.word_size()); 1746 } 1747 1748 bool G1CollectedHeap::expand(size_t expand_bytes) { 1749 size_t old_mem_size = _g1_storage.committed_size(); 1750 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1751 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1752 HeapRegion::GrainBytes); 1753 ergo_verbose2(ErgoHeapSizing, 1754 "expand the heap", 1755 ergo_format_byte("requested expansion amount") 1756 ergo_format_byte("attempted expansion amount"), 1757 expand_bytes, aligned_expand_bytes); 1758 1759 // First commit the memory. 1760 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1761 bool successful = _g1_storage.expand_by(aligned_expand_bytes); 1762 if (successful) { 1763 // Then propagate this update to the necessary data structures. 1764 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1765 update_committed_space(old_end, new_end); 1766 1767 FreeRegionList expansion_list("Local Expansion List"); 1768 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); 1769 assert(mr.start() == old_end, "post-condition"); 1770 // mr might be a smaller region than what was requested if 1771 // expand_by() was unable to allocate the HeapRegion instances 1772 assert(mr.end() <= new_end, "post-condition"); 1773 1774 size_t actual_expand_bytes = mr.byte_size(); 1775 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1776 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), 1777 "post-condition"); 1778 if (actual_expand_bytes < aligned_expand_bytes) { 1779 // We could not expand _hrs to the desired size. In this case we 1780 // need to shrink the committed space accordingly. 1781 assert(mr.end() < new_end, "invariant"); 1782 1783 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; 1784 // First uncommit the memory. 1785 _g1_storage.shrink_by(diff_bytes); 1786 // Then propagate this update to the necessary data structures. 1787 update_committed_space(new_end, mr.end()); 1788 } 1789 _free_list.add_as_tail(&expansion_list); 1790 1791 if (_hr_printer.is_active()) { 1792 HeapWord* curr = mr.start(); 1793 while (curr < mr.end()) { 1794 HeapWord* curr_end = curr + HeapRegion::GrainWords; 1795 _hr_printer.commit(curr, curr_end); 1796 curr = curr_end; 1797 } 1798 assert(curr == mr.end(), "post-condition"); 1799 } 1800 g1_policy()->record_new_heap_size(n_regions()); 1801 } else { 1802 ergo_verbose0(ErgoHeapSizing, 1803 "did not expand the heap", 1804 ergo_format_reason("heap expansion operation failed")); 1805 // The expansion of the virtual storage space was unsuccessful. 1806 // Let's see if it was because we ran out of swap. 1807 if (G1ExitOnExpansionFailure && 1808 _g1_storage.uncommitted_size() >= aligned_expand_bytes) { 1809 // We had head room... 1810 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion"); 1811 } 1812 } 1813 return successful; 1814 } 1815 1816 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1817 size_t old_mem_size = _g1_storage.committed_size(); 1818 size_t aligned_shrink_bytes = 1819 ReservedSpace::page_align_size_down(shrink_bytes); 1820 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1821 HeapRegion::GrainBytes); 1822 uint num_regions_deleted = 0; 1823 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted); 1824 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1825 assert(mr.end() == old_end, "post-condition"); 1826 1827 ergo_verbose3(ErgoHeapSizing, 1828 "shrink the heap", 1829 ergo_format_byte("requested shrinking amount") 1830 ergo_format_byte("aligned shrinking amount") 1831 ergo_format_byte("attempted shrinking amount"), 1832 shrink_bytes, aligned_shrink_bytes, mr.byte_size()); 1833 if (mr.byte_size() > 0) { 1834 if (_hr_printer.is_active()) { 1835 HeapWord* curr = mr.end(); 1836 while (curr > mr.start()) { 1837 HeapWord* curr_end = curr; 1838 curr -= HeapRegion::GrainWords; 1839 _hr_printer.uncommit(curr, curr_end); 1840 } 1841 assert(curr == mr.start(), "post-condition"); 1842 } 1843 1844 _g1_storage.shrink_by(mr.byte_size()); 1845 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1846 assert(mr.start() == new_end, "post-condition"); 1847 1848 _expansion_regions += num_regions_deleted; 1849 update_committed_space(old_end, new_end); 1850 HeapRegionRemSet::shrink_heap(n_regions()); 1851 g1_policy()->record_new_heap_size(n_regions()); 1852 } else { 1853 ergo_verbose0(ErgoHeapSizing, 1854 "did not shrink the heap", 1855 ergo_format_reason("heap shrinking operation failed")); 1856 } 1857 } 1858 1859 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1860 verify_region_sets_optional(); 1861 1862 // We should only reach here at the end of a Full GC which means we 1863 // should not not be holding to any GC alloc regions. The method 1864 // below will make sure of that and do any remaining clean up. 1865 abandon_gc_alloc_regions(); 1866 1867 // Instead of tearing down / rebuilding the free lists here, we 1868 // could instead use the remove_all_pending() method on free_list to 1869 // remove only the ones that we need to remove. 1870 tear_down_region_sets(true /* free_list_only */); 1871 shrink_helper(shrink_bytes); 1872 rebuild_region_sets(true /* free_list_only */); 1873 1874 _hrs.verify_optional(); 1875 verify_region_sets_optional(); 1876 } 1877 1878 // Public methods. 1879 1880 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1881 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1882 #endif // _MSC_VER 1883 1884 1885 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1886 SharedHeap(policy_), 1887 _g1_policy(policy_), 1888 _dirty_card_queue_set(false), 1889 _into_cset_dirty_card_queue_set(false), 1890 _is_alive_closure_cm(this), 1891 _is_alive_closure_stw(this), 1892 _ref_processor_cm(NULL), 1893 _ref_processor_stw(NULL), 1894 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1895 _bot_shared(NULL), 1896 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL), 1897 _evac_failure_scan_stack(NULL) , 1898 _mark_in_progress(false), 1899 _cg1r(NULL), _summary_bytes_used(0), 1900 _g1mm(NULL), 1901 _refine_cte_cl(NULL), 1902 _full_collection(false), 1903 _free_list("Master Free List"), 1904 _secondary_free_list("Secondary Free List"), 1905 _old_set("Old Set"), 1906 _humongous_set("Master Humongous Set"), 1907 _free_regions_coming(false), 1908 _young_list(new YoungList(this)), 1909 _gc_time_stamp(0), 1910 _retained_old_gc_alloc_region(NULL), 1911 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1912 _old_plab_stats(OldPLABSize, PLABWeight), 1913 _expand_heap_after_alloc_failure(true), 1914 _surviving_young_words(NULL), 1915 _old_marking_cycles_started(0), 1916 _old_marking_cycles_completed(0), 1917 _in_cset_fast_test(NULL), 1918 _in_cset_fast_test_base(NULL), 1919 _dirty_cards_region_list(NULL), 1920 _worker_cset_start_region(NULL), 1921 _worker_cset_start_region_time_stamp(NULL) { 1922 _g1h = this; // To catch bugs. 1923 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1924 vm_exit_during_initialization("Failed necessary allocation."); 1925 } 1926 1927 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1928 1929 int n_queues = MAX2((int)ParallelGCThreads, 1); 1930 _task_queues = new RefToScanQueueSet(n_queues); 1931 1932 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1933 assert(n_rem_sets > 0, "Invariant."); 1934 1935 HeapRegionRemSetIterator** iter_arr = 1936 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC); 1937 for (int i = 0; i < n_queues; i++) { 1938 iter_arr[i] = new HeapRegionRemSetIterator(); 1939 } 1940 _rem_set_iterator = iter_arr; 1941 1942 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1943 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1944 1945 for (int i = 0; i < n_queues; i++) { 1946 RefToScanQueue* q = new RefToScanQueue(); 1947 q->initialize(); 1948 _task_queues->register_queue(i, q); 1949 } 1950 1951 clear_cset_start_regions(); 1952 1953 // Initialize the G1EvacuationFailureALot counters and flags. 1954 NOT_PRODUCT(reset_evacuation_should_fail();) 1955 1956 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1957 #ifdef SPARC 1958 // Issue a stern warning, but allow use for experimentation and debugging. 1959 if (VM_Version::is_sun4v() && UseMemSetInBOT) { 1960 assert(!FLAG_IS_DEFAULT(UseMemSetInBOT), "Error"); 1961 warning("Experimental flag -XX:+UseMemSetInBOT is known to cause instability" 1962 " on sun4v; please understand that you are using at your own risk!"); 1963 } 1964 #endif 1965 } 1966 1967 jint G1CollectedHeap::initialize() { 1968 CollectedHeap::pre_initialize(); 1969 os::enable_vtime(); 1970 1971 G1Log::init(); 1972 1973 // Necessary to satisfy locking discipline assertions. 1974 1975 MutexLocker x(Heap_lock); 1976 1977 // We have to initialize the printer before committing the heap, as 1978 // it will be used then. 1979 _hr_printer.set_active(G1PrintHeapRegions); 1980 1981 // While there are no constraints in the GC code that HeapWordSize 1982 // be any particular value, there are multiple other areas in the 1983 // system which believe this to be true (e.g. oop->object_size in some 1984 // cases incorrectly returns the size in wordSize units rather than 1985 // HeapWordSize). 1986 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1987 1988 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1989 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1990 1991 // Ensure that the sizes are properly aligned. 1992 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1993 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1994 1995 _cg1r = new ConcurrentG1Refine(); 1996 1997 // Reserve the maximum. 1998 1999 // When compressed oops are enabled, the preferred heap base 2000 // is calculated by subtracting the requested size from the 2001 // 32Gb boundary and using the result as the base address for 2002 // heap reservation. If the requested size is not aligned to 2003 // HeapRegion::GrainBytes (i.e. the alignment that is passed 2004 // into the ReservedHeapSpace constructor) then the actual 2005 // base of the reserved heap may end up differing from the 2006 // address that was requested (i.e. the preferred heap base). 2007 // If this happens then we could end up using a non-optimal 2008 // compressed oops mode. 2009 2010 // Since max_byte_size is aligned to the size of a heap region (checked 2011 // above). 2012 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2013 2014 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 2015 HeapRegion::GrainBytes); 2016 2017 // It is important to do this in a way such that concurrent readers can't 2018 // temporarily think somethings in the heap. (I've actually seen this 2019 // happen in asserts: DLD.) 2020 _reserved.set_word_size(0); 2021 _reserved.set_start((HeapWord*)heap_rs.base()); 2022 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 2023 2024 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes); 2025 2026 // Create the gen rem set (and barrier set) for the entire reserved region. 2027 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 2028 set_barrier_set(rem_set()->bs()); 2029 if (barrier_set()->is_a(BarrierSet::ModRef)) { 2030 _mr_bs = (ModRefBarrierSet*)_barrier_set; 2031 } else { 2032 vm_exit_during_initialization("G1 requires a mod ref bs."); 2033 return JNI_ENOMEM; 2034 } 2035 2036 // Also create a G1 rem set. 2037 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) { 2038 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs()); 2039 } else { 2040 vm_exit_during_initialization("G1 requires a cardtable mod ref bs."); 2041 return JNI_ENOMEM; 2042 } 2043 2044 // Carve out the G1 part of the heap. 2045 2046 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 2047 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), 2048 g1_rs.size()/HeapWordSize); 2049 2050 _g1_storage.initialize(g1_rs, 0); 2051 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); 2052 _hrs.initialize((HeapWord*) _g1_reserved.start(), 2053 (HeapWord*) _g1_reserved.end(), 2054 _expansion_regions); 2055 2056 // 6843694 - ensure that the maximum region index can fit 2057 // in the remembered set structures. 2058 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2059 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2060 2061 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2062 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2063 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2064 "too many cards per region"); 2065 2066 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1); 2067 2068 _bot_shared = new G1BlockOffsetSharedArray(_reserved, 2069 heap_word_size(init_byte_size)); 2070 2071 _g1h = this; 2072 2073 _in_cset_fast_test_length = max_regions(); 2074 _in_cset_fast_test_base = 2075 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC); 2076 2077 // We're biasing _in_cset_fast_test to avoid subtracting the 2078 // beginning of the heap every time we want to index; basically 2079 // it's the same with what we do with the card table. 2080 _in_cset_fast_test = _in_cset_fast_test_base - 2081 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes); 2082 2083 // Clear the _cset_fast_test bitmap in anticipation of adding 2084 // regions to the incremental collection set for the first 2085 // evacuation pause. 2086 clear_cset_fast_test(); 2087 2088 // Create the ConcurrentMark data structure and thread. 2089 // (Must do this late, so that "max_regions" is defined.) 2090 _cm = new ConcurrentMark(heap_rs, max_regions()); 2091 _cmThread = _cm->cmThread(); 2092 2093 // Initialize the from_card cache structure of HeapRegionRemSet. 2094 HeapRegionRemSet::init_heap(max_regions()); 2095 2096 // Now expand into the initial heap size. 2097 if (!expand(init_byte_size)) { 2098 vm_exit_during_initialization("Failed to allocate initial heap."); 2099 return JNI_ENOMEM; 2100 } 2101 2102 // Perform any initialization actions delegated to the policy. 2103 g1_policy()->init(); 2104 2105 _refine_cte_cl = 2106 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(), 2107 g1_rem_set(), 2108 concurrent_g1_refine()); 2109 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 2110 2111 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2112 SATB_Q_FL_lock, 2113 G1SATBProcessCompletedThreshold, 2114 Shared_SATB_Q_lock); 2115 2116 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2117 DirtyCardQ_FL_lock, 2118 concurrent_g1_refine()->yellow_zone(), 2119 concurrent_g1_refine()->red_zone(), 2120 Shared_DirtyCardQ_lock); 2121 2122 if (G1DeferredRSUpdate) { 2123 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2124 DirtyCardQ_FL_lock, 2125 -1, // never trigger processing 2126 -1, // no limit on length 2127 Shared_DirtyCardQ_lock, 2128 &JavaThread::dirty_card_queue_set()); 2129 } 2130 2131 // Initialize the card queue set used to hold cards containing 2132 // references into the collection set. 2133 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon, 2134 DirtyCardQ_FL_lock, 2135 -1, // never trigger processing 2136 -1, // no limit on length 2137 Shared_DirtyCardQ_lock, 2138 &JavaThread::dirty_card_queue_set()); 2139 2140 // In case we're keeping closure specialization stats, initialize those 2141 // counts and that mechanism. 2142 SpecializationStats::clear(); 2143 2144 // Do later initialization work for concurrent refinement. 2145 _cg1r->init(); 2146 2147 // Here we allocate the dummy full region that is required by the 2148 // G1AllocRegion class. If we don't pass an address in the reserved 2149 // space here, lots of asserts fire. 2150 2151 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, 2152 _g1_reserved.start()); 2153 // We'll re-use the same region whether the alloc region will 2154 // require BOT updates or not and, if it doesn't, then a non-young 2155 // region will complain that it cannot support allocations without 2156 // BOT updates. So we'll tag the dummy region as young to avoid that. 2157 dummy_region->set_young(); 2158 // Make sure it's full. 2159 dummy_region->set_top(dummy_region->end()); 2160 G1AllocRegion::setup(this, dummy_region); 2161 2162 init_mutator_alloc_region(); 2163 2164 // Do create of the monitoring and management support so that 2165 // values in the heap have been properly initialized. 2166 _g1mm = new G1MonitoringSupport(this); 2167 2168 return JNI_OK; 2169 } 2170 2171 void G1CollectedHeap::ref_processing_init() { 2172 // Reference processing in G1 currently works as follows: 2173 // 2174 // * There are two reference processor instances. One is 2175 // used to record and process discovered references 2176 // during concurrent marking; the other is used to 2177 // record and process references during STW pauses 2178 // (both full and incremental). 2179 // * Both ref processors need to 'span' the entire heap as 2180 // the regions in the collection set may be dotted around. 2181 // 2182 // * For the concurrent marking ref processor: 2183 // * Reference discovery is enabled at initial marking. 2184 // * Reference discovery is disabled and the discovered 2185 // references processed etc during remarking. 2186 // * Reference discovery is MT (see below). 2187 // * Reference discovery requires a barrier (see below). 2188 // * Reference processing may or may not be MT 2189 // (depending on the value of ParallelRefProcEnabled 2190 // and ParallelGCThreads). 2191 // * A full GC disables reference discovery by the CM 2192 // ref processor and abandons any entries on it's 2193 // discovered lists. 2194 // 2195 // * For the STW processor: 2196 // * Non MT discovery is enabled at the start of a full GC. 2197 // * Processing and enqueueing during a full GC is non-MT. 2198 // * During a full GC, references are processed after marking. 2199 // 2200 // * Discovery (may or may not be MT) is enabled at the start 2201 // of an incremental evacuation pause. 2202 // * References are processed near the end of a STW evacuation pause. 2203 // * For both types of GC: 2204 // * Discovery is atomic - i.e. not concurrent. 2205 // * Reference discovery will not need a barrier. 2206 2207 SharedHeap::ref_processing_init(); 2208 MemRegion mr = reserved_region(); 2209 2210 // Concurrent Mark ref processor 2211 _ref_processor_cm = 2212 new ReferenceProcessor(mr, // span 2213 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2214 // mt processing 2215 (int) ParallelGCThreads, 2216 // degree of mt processing 2217 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2218 // mt discovery 2219 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2220 // degree of mt discovery 2221 false, 2222 // Reference discovery is not atomic 2223 &_is_alive_closure_cm, 2224 // is alive closure 2225 // (for efficiency/performance) 2226 true); 2227 // Setting next fields of discovered 2228 // lists requires a barrier. 2229 2230 // STW ref processor 2231 _ref_processor_stw = 2232 new ReferenceProcessor(mr, // span 2233 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2234 // mt processing 2235 MAX2((int)ParallelGCThreads, 1), 2236 // degree of mt processing 2237 (ParallelGCThreads > 1), 2238 // mt discovery 2239 MAX2((int)ParallelGCThreads, 1), 2240 // degree of mt discovery 2241 true, 2242 // Reference discovery is atomic 2243 &_is_alive_closure_stw, 2244 // is alive closure 2245 // (for efficiency/performance) 2246 false); 2247 // Setting next fields of discovered 2248 // lists requires a barrier. 2249 } 2250 2251 size_t G1CollectedHeap::capacity() const { 2252 return _g1_committed.byte_size(); 2253 } 2254 2255 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2256 assert(!hr->continuesHumongous(), "pre-condition"); 2257 hr->reset_gc_time_stamp(); 2258 if (hr->startsHumongous()) { 2259 uint first_index = hr->hrs_index() + 1; 2260 uint last_index = hr->last_hc_index(); 2261 for (uint i = first_index; i < last_index; i += 1) { 2262 HeapRegion* chr = region_at(i); 2263 assert(chr->continuesHumongous(), "sanity"); 2264 chr->reset_gc_time_stamp(); 2265 } 2266 } 2267 } 2268 2269 #ifndef PRODUCT 2270 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2271 private: 2272 unsigned _gc_time_stamp; 2273 bool _failures; 2274 2275 public: 2276 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2277 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2278 2279 virtual bool doHeapRegion(HeapRegion* hr) { 2280 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2281 if (_gc_time_stamp != region_gc_time_stamp) { 2282 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2283 "expected %d", HR_FORMAT_PARAMS(hr), 2284 region_gc_time_stamp, _gc_time_stamp); 2285 _failures = true; 2286 } 2287 return false; 2288 } 2289 2290 bool failures() { return _failures; } 2291 }; 2292 2293 void G1CollectedHeap::check_gc_time_stamps() { 2294 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2295 heap_region_iterate(&cl); 2296 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2297 } 2298 #endif // PRODUCT 2299 2300 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2301 DirtyCardQueue* into_cset_dcq, 2302 bool concurrent, 2303 int worker_i) { 2304 // Clean cards in the hot card cache 2305 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq); 2306 2307 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2308 int n_completed_buffers = 0; 2309 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2310 n_completed_buffers++; 2311 } 2312 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2313 dcqs.clear_n_completed_buffers(); 2314 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2315 } 2316 2317 2318 // Computes the sum of the storage used by the various regions. 2319 2320 size_t G1CollectedHeap::used() const { 2321 assert(Heap_lock->owner() != NULL, 2322 "Should be owned on this thread's behalf."); 2323 size_t result = _summary_bytes_used; 2324 // Read only once in case it is set to NULL concurrently 2325 HeapRegion* hr = _mutator_alloc_region.get(); 2326 if (hr != NULL) 2327 result += hr->used(); 2328 return result; 2329 } 2330 2331 size_t G1CollectedHeap::used_unlocked() const { 2332 size_t result = _summary_bytes_used; 2333 return result; 2334 } 2335 2336 class SumUsedClosure: public HeapRegionClosure { 2337 size_t _used; 2338 public: 2339 SumUsedClosure() : _used(0) {} 2340 bool doHeapRegion(HeapRegion* r) { 2341 if (!r->continuesHumongous()) { 2342 _used += r->used(); 2343 } 2344 return false; 2345 } 2346 size_t result() { return _used; } 2347 }; 2348 2349 size_t G1CollectedHeap::recalculate_used() const { 2350 SumUsedClosure blk; 2351 heap_region_iterate(&blk); 2352 return blk.result(); 2353 } 2354 2355 size_t G1CollectedHeap::unsafe_max_alloc() { 2356 if (free_regions() > 0) return HeapRegion::GrainBytes; 2357 // otherwise, is there space in the current allocation region? 2358 2359 // We need to store the current allocation region in a local variable 2360 // here. The problem is that this method doesn't take any locks and 2361 // there may be other threads which overwrite the current allocation 2362 // region field. attempt_allocation(), for example, sets it to NULL 2363 // and this can happen *after* the NULL check here but before the call 2364 // to free(), resulting in a SIGSEGV. Note that this doesn't appear 2365 // to be a problem in the optimized build, since the two loads of the 2366 // current allocation region field are optimized away. 2367 HeapRegion* hr = _mutator_alloc_region.get(); 2368 if (hr == NULL) { 2369 return 0; 2370 } 2371 return hr->free(); 2372 } 2373 2374 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2375 switch (cause) { 2376 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2377 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2378 case GCCause::_g1_humongous_allocation: return true; 2379 default: return false; 2380 } 2381 } 2382 2383 #ifndef PRODUCT 2384 void G1CollectedHeap::allocate_dummy_regions() { 2385 // Let's fill up most of the region 2386 size_t word_size = HeapRegion::GrainWords - 1024; 2387 // And as a result the region we'll allocate will be humongous. 2388 guarantee(isHumongous(word_size), "sanity"); 2389 2390 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2391 // Let's use the existing mechanism for the allocation 2392 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2393 if (dummy_obj != NULL) { 2394 MemRegion mr(dummy_obj, word_size); 2395 CollectedHeap::fill_with_object(mr); 2396 } else { 2397 // If we can't allocate once, we probably cannot allocate 2398 // again. Let's get out of the loop. 2399 break; 2400 } 2401 } 2402 } 2403 #endif // !PRODUCT 2404 2405 void G1CollectedHeap::increment_old_marking_cycles_started() { 2406 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2407 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2408 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2409 _old_marking_cycles_started, _old_marking_cycles_completed)); 2410 2411 _old_marking_cycles_started++; 2412 } 2413 2414 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2415 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2416 2417 // We assume that if concurrent == true, then the caller is a 2418 // concurrent thread that was joined the Suspendible Thread 2419 // Set. If there's ever a cheap way to check this, we should add an 2420 // assert here. 2421 2422 // Given that this method is called at the end of a Full GC or of a 2423 // concurrent cycle, and those can be nested (i.e., a Full GC can 2424 // interrupt a concurrent cycle), the number of full collections 2425 // completed should be either one (in the case where there was no 2426 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2427 // behind the number of full collections started. 2428 2429 // This is the case for the inner caller, i.e. a Full GC. 2430 assert(concurrent || 2431 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2432 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2433 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2434 "is inconsistent with _old_marking_cycles_completed = %u", 2435 _old_marking_cycles_started, _old_marking_cycles_completed)); 2436 2437 // This is the case for the outer caller, i.e. the concurrent cycle. 2438 assert(!concurrent || 2439 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2440 err_msg("for outer caller (concurrent cycle): " 2441 "_old_marking_cycles_started = %u " 2442 "is inconsistent with _old_marking_cycles_completed = %u", 2443 _old_marking_cycles_started, _old_marking_cycles_completed)); 2444 2445 _old_marking_cycles_completed += 1; 2446 2447 // We need to clear the "in_progress" flag in the CM thread before 2448 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2449 // is set) so that if a waiter requests another System.gc() it doesn't 2450 // incorrectly see that a marking cyle is still in progress. 2451 if (concurrent) { 2452 _cmThread->clear_in_progress(); 2453 } 2454 2455 // This notify_all() will ensure that a thread that called 2456 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2457 // and it's waiting for a full GC to finish will be woken up. It is 2458 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2459 FullGCCount_lock->notify_all(); 2460 } 2461 2462 void G1CollectedHeap::collect(GCCause::Cause cause) { 2463 assert_heap_not_locked(); 2464 2465 unsigned int gc_count_before; 2466 unsigned int old_marking_count_before; 2467 bool retry_gc; 2468 2469 do { 2470 retry_gc = false; 2471 2472 { 2473 MutexLocker ml(Heap_lock); 2474 2475 // Read the GC count while holding the Heap_lock 2476 gc_count_before = total_collections(); 2477 old_marking_count_before = _old_marking_cycles_started; 2478 } 2479 2480 if (should_do_concurrent_full_gc(cause)) { 2481 // Schedule an initial-mark evacuation pause that will start a 2482 // concurrent cycle. We're setting word_size to 0 which means that 2483 // we are not requesting a post-GC allocation. 2484 VM_G1IncCollectionPause op(gc_count_before, 2485 0, /* word_size */ 2486 true, /* should_initiate_conc_mark */ 2487 g1_policy()->max_pause_time_ms(), 2488 cause); 2489 2490 VMThread::execute(&op); 2491 if (!op.pause_succeeded()) { 2492 if (old_marking_count_before == _old_marking_cycles_started) { 2493 retry_gc = op.should_retry_gc(); 2494 } else { 2495 // A Full GC happened while we were trying to schedule the 2496 // initial-mark GC. No point in starting a new cycle given 2497 // that the whole heap was collected anyway. 2498 } 2499 2500 if (retry_gc) { 2501 if (GC_locker::is_active_and_needs_gc()) { 2502 GC_locker::stall_until_clear(); 2503 } 2504 } 2505 } 2506 } else { 2507 if (cause == GCCause::_gc_locker 2508 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2509 2510 // Schedule a standard evacuation pause. We're setting word_size 2511 // to 0 which means that we are not requesting a post-GC allocation. 2512 VM_G1IncCollectionPause op(gc_count_before, 2513 0, /* word_size */ 2514 false, /* should_initiate_conc_mark */ 2515 g1_policy()->max_pause_time_ms(), 2516 cause); 2517 VMThread::execute(&op); 2518 } else { 2519 // Schedule a Full GC. 2520 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause); 2521 VMThread::execute(&op); 2522 } 2523 } 2524 } while (retry_gc); 2525 } 2526 2527 bool G1CollectedHeap::is_in(const void* p) const { 2528 if (_g1_committed.contains(p)) { 2529 // Given that we know that p is in the committed space, 2530 // heap_region_containing_raw() should successfully 2531 // return the containing region. 2532 HeapRegion* hr = heap_region_containing_raw(p); 2533 return hr->is_in(p); 2534 } else { 2535 return false; 2536 } 2537 } 2538 2539 // Iteration functions. 2540 2541 // Iterates an OopClosure over all ref-containing fields of objects 2542 // within a HeapRegion. 2543 2544 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2545 MemRegion _mr; 2546 ExtendedOopClosure* _cl; 2547 public: 2548 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl) 2549 : _mr(mr), _cl(cl) {} 2550 bool doHeapRegion(HeapRegion* r) { 2551 if (!r->continuesHumongous()) { 2552 r->oop_iterate(_cl); 2553 } 2554 return false; 2555 } 2556 }; 2557 2558 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2559 IterateOopClosureRegionClosure blk(_g1_committed, cl); 2560 heap_region_iterate(&blk); 2561 } 2562 2563 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { 2564 IterateOopClosureRegionClosure blk(mr, cl); 2565 heap_region_iterate(&blk); 2566 } 2567 2568 // Iterates an ObjectClosure over all objects within a HeapRegion. 2569 2570 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2571 ObjectClosure* _cl; 2572 public: 2573 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2574 bool doHeapRegion(HeapRegion* r) { 2575 if (! r->continuesHumongous()) { 2576 r->object_iterate(_cl); 2577 } 2578 return false; 2579 } 2580 }; 2581 2582 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2583 IterateObjectClosureRegionClosure blk(cl); 2584 heap_region_iterate(&blk); 2585 } 2586 2587 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) { 2588 // FIXME: is this right? 2589 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap"); 2590 } 2591 2592 // Calls a SpaceClosure on a HeapRegion. 2593 2594 class SpaceClosureRegionClosure: public HeapRegionClosure { 2595 SpaceClosure* _cl; 2596 public: 2597 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2598 bool doHeapRegion(HeapRegion* r) { 2599 _cl->do_space(r); 2600 return false; 2601 } 2602 }; 2603 2604 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2605 SpaceClosureRegionClosure blk(cl); 2606 heap_region_iterate(&blk); 2607 } 2608 2609 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2610 _hrs.iterate(cl); 2611 } 2612 2613 void 2614 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2615 uint worker_id, 2616 uint no_of_par_workers, 2617 jint claim_value) { 2618 const uint regions = n_regions(); 2619 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 2620 no_of_par_workers : 2621 1); 2622 assert(UseDynamicNumberOfGCThreads || 2623 no_of_par_workers == workers()->total_workers(), 2624 "Non dynamic should use fixed number of workers"); 2625 // try to spread out the starting points of the workers 2626 const HeapRegion* start_hr = 2627 start_region_for_worker(worker_id, no_of_par_workers); 2628 const uint start_index = start_hr->hrs_index(); 2629 2630 // each worker will actually look at all regions 2631 for (uint count = 0; count < regions; ++count) { 2632 const uint index = (start_index + count) % regions; 2633 assert(0 <= index && index < regions, "sanity"); 2634 HeapRegion* r = region_at(index); 2635 // we'll ignore "continues humongous" regions (we'll process them 2636 // when we come across their corresponding "start humongous" 2637 // region) and regions already claimed 2638 if (r->claim_value() == claim_value || r->continuesHumongous()) { 2639 continue; 2640 } 2641 // OK, try to claim it 2642 if (r->claimHeapRegion(claim_value)) { 2643 // success! 2644 assert(!r->continuesHumongous(), "sanity"); 2645 if (r->startsHumongous()) { 2646 // If the region is "starts humongous" we'll iterate over its 2647 // "continues humongous" first; in fact we'll do them 2648 // first. The order is important. In on case, calling the 2649 // closure on the "starts humongous" region might de-allocate 2650 // and clear all its "continues humongous" regions and, as a 2651 // result, we might end up processing them twice. So, we'll do 2652 // them first (notice: most closures will ignore them anyway) and 2653 // then we'll do the "starts humongous" region. 2654 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) { 2655 HeapRegion* chr = region_at(ch_index); 2656 2657 // if the region has already been claimed or it's not 2658 // "continues humongous" we're done 2659 if (chr->claim_value() == claim_value || 2660 !chr->continuesHumongous()) { 2661 break; 2662 } 2663 2664 // Noone should have claimed it directly. We can given 2665 // that we claimed its "starts humongous" region. 2666 assert(chr->claim_value() != claim_value, "sanity"); 2667 assert(chr->humongous_start_region() == r, "sanity"); 2668 2669 if (chr->claimHeapRegion(claim_value)) { 2670 // we should always be able to claim it; noone else should 2671 // be trying to claim this region 2672 2673 bool res2 = cl->doHeapRegion(chr); 2674 assert(!res2, "Should not abort"); 2675 2676 // Right now, this holds (i.e., no closure that actually 2677 // does something with "continues humongous" regions 2678 // clears them). We might have to weaken it in the future, 2679 // but let's leave these two asserts here for extra safety. 2680 assert(chr->continuesHumongous(), "should still be the case"); 2681 assert(chr->humongous_start_region() == r, "sanity"); 2682 } else { 2683 guarantee(false, "we should not reach here"); 2684 } 2685 } 2686 } 2687 2688 assert(!r->continuesHumongous(), "sanity"); 2689 bool res = cl->doHeapRegion(r); 2690 assert(!res, "Should not abort"); 2691 } 2692 } 2693 } 2694 2695 class ResetClaimValuesClosure: public HeapRegionClosure { 2696 public: 2697 bool doHeapRegion(HeapRegion* r) { 2698 r->set_claim_value(HeapRegion::InitialClaimValue); 2699 return false; 2700 } 2701 }; 2702 2703 void G1CollectedHeap::reset_heap_region_claim_values() { 2704 ResetClaimValuesClosure blk; 2705 heap_region_iterate(&blk); 2706 } 2707 2708 void G1CollectedHeap::reset_cset_heap_region_claim_values() { 2709 ResetClaimValuesClosure blk; 2710 collection_set_iterate(&blk); 2711 } 2712 2713 #ifdef ASSERT 2714 // This checks whether all regions in the heap have the correct claim 2715 // value. I also piggy-backed on this a check to ensure that the 2716 // humongous_start_region() information on "continues humongous" 2717 // regions is correct. 2718 2719 class CheckClaimValuesClosure : public HeapRegionClosure { 2720 private: 2721 jint _claim_value; 2722 uint _failures; 2723 HeapRegion* _sh_region; 2724 2725 public: 2726 CheckClaimValuesClosure(jint claim_value) : 2727 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2728 bool doHeapRegion(HeapRegion* r) { 2729 if (r->claim_value() != _claim_value) { 2730 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2731 "claim value = %d, should be %d", 2732 HR_FORMAT_PARAMS(r), 2733 r->claim_value(), _claim_value); 2734 ++_failures; 2735 } 2736 if (!r->isHumongous()) { 2737 _sh_region = NULL; 2738 } else if (r->startsHumongous()) { 2739 _sh_region = r; 2740 } else if (r->continuesHumongous()) { 2741 if (r->humongous_start_region() != _sh_region) { 2742 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2743 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2744 HR_FORMAT_PARAMS(r), 2745 r->humongous_start_region(), 2746 _sh_region); 2747 ++_failures; 2748 } 2749 } 2750 return false; 2751 } 2752 uint failures() { return _failures; } 2753 }; 2754 2755 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2756 CheckClaimValuesClosure cl(claim_value); 2757 heap_region_iterate(&cl); 2758 return cl.failures() == 0; 2759 } 2760 2761 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2762 private: 2763 jint _claim_value; 2764 uint _failures; 2765 2766 public: 2767 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2768 _claim_value(claim_value), _failures(0) { } 2769 2770 uint failures() { return _failures; } 2771 2772 bool doHeapRegion(HeapRegion* hr) { 2773 assert(hr->in_collection_set(), "how?"); 2774 assert(!hr->isHumongous(), "H-region in CSet"); 2775 if (hr->claim_value() != _claim_value) { 2776 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2777 "claim value = %d, should be %d", 2778 HR_FORMAT_PARAMS(hr), 2779 hr->claim_value(), _claim_value); 2780 _failures += 1; 2781 } 2782 return false; 2783 } 2784 }; 2785 2786 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2787 CheckClaimValuesInCSetHRClosure cl(claim_value); 2788 collection_set_iterate(&cl); 2789 return cl.failures() == 0; 2790 } 2791 #endif // ASSERT 2792 2793 // Clear the cached CSet starting regions and (more importantly) 2794 // the time stamps. Called when we reset the GC time stamp. 2795 void G1CollectedHeap::clear_cset_start_regions() { 2796 assert(_worker_cset_start_region != NULL, "sanity"); 2797 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2798 2799 int n_queues = MAX2((int)ParallelGCThreads, 1); 2800 for (int i = 0; i < n_queues; i++) { 2801 _worker_cset_start_region[i] = NULL; 2802 _worker_cset_start_region_time_stamp[i] = 0; 2803 } 2804 } 2805 2806 // Given the id of a worker, obtain or calculate a suitable 2807 // starting region for iterating over the current collection set. 2808 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) { 2809 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2810 2811 HeapRegion* result = NULL; 2812 unsigned gc_time_stamp = get_gc_time_stamp(); 2813 2814 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2815 // Cached starting region for current worker was set 2816 // during the current pause - so it's valid. 2817 // Note: the cached starting heap region may be NULL 2818 // (when the collection set is empty). 2819 result = _worker_cset_start_region[worker_i]; 2820 assert(result == NULL || result->in_collection_set(), "sanity"); 2821 return result; 2822 } 2823 2824 // The cached entry was not valid so let's calculate 2825 // a suitable starting heap region for this worker. 2826 2827 // We want the parallel threads to start their collection 2828 // set iteration at different collection set regions to 2829 // avoid contention. 2830 // If we have: 2831 // n collection set regions 2832 // p threads 2833 // Then thread t will start at region floor ((t * n) / p) 2834 2835 result = g1_policy()->collection_set(); 2836 if (G1CollectedHeap::use_parallel_gc_threads()) { 2837 uint cs_size = g1_policy()->cset_region_length(); 2838 uint active_workers = workers()->active_workers(); 2839 assert(UseDynamicNumberOfGCThreads || 2840 active_workers == workers()->total_workers(), 2841 "Unless dynamic should use total workers"); 2842 2843 uint end_ind = (cs_size * worker_i) / active_workers; 2844 uint start_ind = 0; 2845 2846 if (worker_i > 0 && 2847 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2848 // Previous workers starting region is valid 2849 // so let's iterate from there 2850 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2851 result = _worker_cset_start_region[worker_i - 1]; 2852 } 2853 2854 for (uint i = start_ind; i < end_ind; i++) { 2855 result = result->next_in_collection_set(); 2856 } 2857 } 2858 2859 // Note: the calculated starting heap region may be NULL 2860 // (when the collection set is empty). 2861 assert(result == NULL || result->in_collection_set(), "sanity"); 2862 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2863 "should be updated only once per pause"); 2864 _worker_cset_start_region[worker_i] = result; 2865 OrderAccess::storestore(); 2866 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2867 return result; 2868 } 2869 2870 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i, 2871 uint no_of_par_workers) { 2872 uint worker_num = 2873 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U; 2874 assert(UseDynamicNumberOfGCThreads || 2875 no_of_par_workers == workers()->total_workers(), 2876 "Non dynamic should use fixed number of workers"); 2877 const uint start_index = n_regions() * worker_i / worker_num; 2878 return region_at(start_index); 2879 } 2880 2881 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2882 HeapRegion* r = g1_policy()->collection_set(); 2883 while (r != NULL) { 2884 HeapRegion* next = r->next_in_collection_set(); 2885 if (cl->doHeapRegion(r)) { 2886 cl->incomplete(); 2887 return; 2888 } 2889 r = next; 2890 } 2891 } 2892 2893 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2894 HeapRegionClosure *cl) { 2895 if (r == NULL) { 2896 // The CSet is empty so there's nothing to do. 2897 return; 2898 } 2899 2900 assert(r->in_collection_set(), 2901 "Start region must be a member of the collection set."); 2902 HeapRegion* cur = r; 2903 while (cur != NULL) { 2904 HeapRegion* next = cur->next_in_collection_set(); 2905 if (cl->doHeapRegion(cur) && false) { 2906 cl->incomplete(); 2907 return; 2908 } 2909 cur = next; 2910 } 2911 cur = g1_policy()->collection_set(); 2912 while (cur != r) { 2913 HeapRegion* next = cur->next_in_collection_set(); 2914 if (cl->doHeapRegion(cur) && false) { 2915 cl->incomplete(); 2916 return; 2917 } 2918 cur = next; 2919 } 2920 } 2921 2922 CompactibleSpace* G1CollectedHeap::first_compactible_space() { 2923 return n_regions() > 0 ? region_at(0) : NULL; 2924 } 2925 2926 2927 Space* G1CollectedHeap::space_containing(const void* addr) const { 2928 Space* res = heap_region_containing(addr); 2929 return res; 2930 } 2931 2932 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2933 Space* sp = space_containing(addr); 2934 if (sp != NULL) { 2935 return sp->block_start(addr); 2936 } 2937 return NULL; 2938 } 2939 2940 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2941 Space* sp = space_containing(addr); 2942 assert(sp != NULL, "block_size of address outside of heap"); 2943 return sp->block_size(addr); 2944 } 2945 2946 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2947 Space* sp = space_containing(addr); 2948 return sp->block_is_obj(addr); 2949 } 2950 2951 bool G1CollectedHeap::supports_tlab_allocation() const { 2952 return true; 2953 } 2954 2955 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2956 return HeapRegion::GrainBytes; 2957 } 2958 2959 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2960 // Return the remaining space in the cur alloc region, but not less than 2961 // the min TLAB size. 2962 2963 // Also, this value can be at most the humongous object threshold, 2964 // since we can't allow tlabs to grow big enough to accomodate 2965 // humongous objects. 2966 2967 HeapRegion* hr = _mutator_alloc_region.get(); 2968 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize; 2969 if (hr == NULL) { 2970 return max_tlab_size; 2971 } else { 2972 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size); 2973 } 2974 } 2975 2976 size_t G1CollectedHeap::max_capacity() const { 2977 return _g1_reserved.byte_size(); 2978 } 2979 2980 jlong G1CollectedHeap::millis_since_last_gc() { 2981 // assert(false, "NYI"); 2982 return 0; 2983 } 2984 2985 void G1CollectedHeap::prepare_for_verify() { 2986 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2987 ensure_parsability(false); 2988 } 2989 g1_rem_set()->prepare_for_verify(); 2990 } 2991 2992 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2993 VerifyOption vo) { 2994 switch (vo) { 2995 case VerifyOption_G1UsePrevMarking: 2996 return hr->obj_allocated_since_prev_marking(obj); 2997 case VerifyOption_G1UseNextMarking: 2998 return hr->obj_allocated_since_next_marking(obj); 2999 case VerifyOption_G1UseMarkWord: 3000 return false; 3001 default: 3002 ShouldNotReachHere(); 3003 } 3004 return false; // keep some compilers happy 3005 } 3006 3007 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 3008 switch (vo) { 3009 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 3010 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 3011 case VerifyOption_G1UseMarkWord: return NULL; 3012 default: ShouldNotReachHere(); 3013 } 3014 return NULL; // keep some compilers happy 3015 } 3016 3017 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 3018 switch (vo) { 3019 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 3020 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 3021 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 3022 default: ShouldNotReachHere(); 3023 } 3024 return false; // keep some compilers happy 3025 } 3026 3027 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 3028 switch (vo) { 3029 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 3030 case VerifyOption_G1UseNextMarking: return "NTAMS"; 3031 case VerifyOption_G1UseMarkWord: return "NONE"; 3032 default: ShouldNotReachHere(); 3033 } 3034 return NULL; // keep some compilers happy 3035 } 3036 3037 class VerifyLivenessOopClosure: public OopClosure { 3038 G1CollectedHeap* _g1h; 3039 VerifyOption _vo; 3040 public: 3041 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3042 _g1h(g1h), _vo(vo) 3043 { } 3044 void do_oop(narrowOop *p) { do_oop_work(p); } 3045 void do_oop( oop *p) { do_oop_work(p); } 3046 3047 template <class T> void do_oop_work(T *p) { 3048 oop obj = oopDesc::load_decode_heap_oop(p); 3049 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3050 "Dead object referenced by a not dead object"); 3051 } 3052 }; 3053 3054 class VerifyObjsInRegionClosure: public ObjectClosure { 3055 private: 3056 G1CollectedHeap* _g1h; 3057 size_t _live_bytes; 3058 HeapRegion *_hr; 3059 VerifyOption _vo; 3060 public: 3061 // _vo == UsePrevMarking -> use "prev" marking information, 3062 // _vo == UseNextMarking -> use "next" marking information, 3063 // _vo == UseMarkWord -> use mark word from object header. 3064 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3065 : _live_bytes(0), _hr(hr), _vo(vo) { 3066 _g1h = G1CollectedHeap::heap(); 3067 } 3068 void do_object(oop o) { 3069 VerifyLivenessOopClosure isLive(_g1h, _vo); 3070 assert(o != NULL, "Huh?"); 3071 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3072 // If the object is alive according to the mark word, 3073 // then verify that the marking information agrees. 3074 // Note we can't verify the contra-positive of the 3075 // above: if the object is dead (according to the mark 3076 // word), it may not be marked, or may have been marked 3077 // but has since became dead, or may have been allocated 3078 // since the last marking. 3079 if (_vo == VerifyOption_G1UseMarkWord) { 3080 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3081 } 3082 3083 o->oop_iterate_no_header(&isLive); 3084 if (!_hr->obj_allocated_since_prev_marking(o)) { 3085 size_t obj_size = o->size(); // Make sure we don't overflow 3086 _live_bytes += (obj_size * HeapWordSize); 3087 } 3088 } 3089 } 3090 size_t live_bytes() { return _live_bytes; } 3091 }; 3092 3093 class PrintObjsInRegionClosure : public ObjectClosure { 3094 HeapRegion *_hr; 3095 G1CollectedHeap *_g1; 3096 public: 3097 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3098 _g1 = G1CollectedHeap::heap(); 3099 }; 3100 3101 void do_object(oop o) { 3102 if (o != NULL) { 3103 HeapWord *start = (HeapWord *) o; 3104 size_t word_sz = o->size(); 3105 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3106 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3107 (void*) o, word_sz, 3108 _g1->isMarkedPrev(o), 3109 _g1->isMarkedNext(o), 3110 _hr->obj_allocated_since_prev_marking(o)); 3111 HeapWord *end = start + word_sz; 3112 HeapWord *cur; 3113 int *val; 3114 for (cur = start; cur < end; cur++) { 3115 val = (int *) cur; 3116 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 3117 } 3118 } 3119 } 3120 }; 3121 3122 class VerifyRegionClosure: public HeapRegionClosure { 3123 private: 3124 bool _par; 3125 VerifyOption _vo; 3126 bool _failures; 3127 public: 3128 // _vo == UsePrevMarking -> use "prev" marking information, 3129 // _vo == UseNextMarking -> use "next" marking information, 3130 // _vo == UseMarkWord -> use mark word from object header. 3131 VerifyRegionClosure(bool par, VerifyOption vo) 3132 : _par(par), 3133 _vo(vo), 3134 _failures(false) {} 3135 3136 bool failures() { 3137 return _failures; 3138 } 3139 3140 bool doHeapRegion(HeapRegion* r) { 3141 if (!r->continuesHumongous()) { 3142 bool failures = false; 3143 r->verify(_vo, &failures); 3144 if (failures) { 3145 _failures = true; 3146 } else { 3147 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3148 r->object_iterate(¬_dead_yet_cl); 3149 if (_vo != VerifyOption_G1UseNextMarking) { 3150 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3151 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3152 "max_live_bytes "SIZE_FORMAT" " 3153 "< calculated "SIZE_FORMAT, 3154 r->bottom(), r->end(), 3155 r->max_live_bytes(), 3156 not_dead_yet_cl.live_bytes()); 3157 _failures = true; 3158 } 3159 } else { 3160 // When vo == UseNextMarking we cannot currently do a sanity 3161 // check on the live bytes as the calculation has not been 3162 // finalized yet. 3163 } 3164 } 3165 } 3166 return false; // stop the region iteration if we hit a failure 3167 } 3168 }; 3169 3170 class YoungRefCounterClosure : public OopClosure { 3171 G1CollectedHeap* _g1h; 3172 int _count; 3173 public: 3174 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 3175 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 3176 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 3177 3178 int count() { return _count; } 3179 void reset_count() { _count = 0; }; 3180 }; 3181 3182 class VerifyKlassClosure: public KlassClosure { 3183 YoungRefCounterClosure _young_ref_counter_closure; 3184 OopClosure *_oop_closure; 3185 public: 3186 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3187 void do_klass(Klass* k) { 3188 k->oops_do(_oop_closure); 3189 3190 _young_ref_counter_closure.reset_count(); 3191 k->oops_do(&_young_ref_counter_closure); 3192 if (_young_ref_counter_closure.count() > 0) { 3193 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); 3194 } 3195 } 3196 }; 3197 3198 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can 3199 // pass it as the perm_blk to SharedHeap::process_strong_roots. 3200 // When process_strong_roots stop calling perm_blk->younger_refs_iterate 3201 // we can change this closure to extend the simpler OopClosure. 3202 class VerifyRootsClosure: public OopsInGenClosure { 3203 private: 3204 G1CollectedHeap* _g1h; 3205 VerifyOption _vo; 3206 bool _failures; 3207 public: 3208 // _vo == UsePrevMarking -> use "prev" marking information, 3209 // _vo == UseNextMarking -> use "next" marking information, 3210 // _vo == UseMarkWord -> use mark word from object header. 3211 VerifyRootsClosure(VerifyOption vo) : 3212 _g1h(G1CollectedHeap::heap()), 3213 _vo(vo), 3214 _failures(false) { } 3215 3216 bool failures() { return _failures; } 3217 3218 template <class T> void do_oop_nv(T* p) { 3219 T heap_oop = oopDesc::load_heap_oop(p); 3220 if (!oopDesc::is_null(heap_oop)) { 3221 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3222 if (_g1h->is_obj_dead_cond(obj, _vo)) { 3223 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 3224 "points to dead obj "PTR_FORMAT, p, (void*) obj); 3225 if (_vo == VerifyOption_G1UseMarkWord) { 3226 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 3227 } 3228 obj->print_on(gclog_or_tty); 3229 _failures = true; 3230 } 3231 } 3232 } 3233 3234 void do_oop(oop* p) { do_oop_nv(p); } 3235 void do_oop(narrowOop* p) { do_oop_nv(p); } 3236 }; 3237 3238 // This is the task used for parallel heap verification. 3239 3240 class G1ParVerifyTask: public AbstractGangTask { 3241 private: 3242 G1CollectedHeap* _g1h; 3243 VerifyOption _vo; 3244 bool _failures; 3245 3246 public: 3247 // _vo == UsePrevMarking -> use "prev" marking information, 3248 // _vo == UseNextMarking -> use "next" marking information, 3249 // _vo == UseMarkWord -> use mark word from object header. 3250 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3251 AbstractGangTask("Parallel verify task"), 3252 _g1h(g1h), 3253 _vo(vo), 3254 _failures(false) { } 3255 3256 bool failures() { 3257 return _failures; 3258 } 3259 3260 void work(uint worker_id) { 3261 HandleMark hm; 3262 VerifyRegionClosure blk(true, _vo); 3263 _g1h->heap_region_par_iterate_chunked(&blk, worker_id, 3264 _g1h->workers()->active_workers(), 3265 HeapRegion::ParVerifyClaimValue); 3266 if (blk.failures()) { 3267 _failures = true; 3268 } 3269 } 3270 }; 3271 3272 void G1CollectedHeap::verify(bool silent) { 3273 verify(silent, VerifyOption_G1UsePrevMarking); 3274 } 3275 3276 void G1CollectedHeap::verify(bool silent, 3277 VerifyOption vo) { 3278 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 3279 if (!silent) { gclog_or_tty->print("Roots "); } 3280 VerifyRootsClosure rootsCl(vo); 3281 3282 assert(Thread::current()->is_VM_thread(), 3283 "Expected to be executed serially by the VM thread at this point"); 3284 3285 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false); 3286 VerifyKlassClosure klassCl(this, &rootsCl); 3287 3288 // We apply the relevant closures to all the oops in the 3289 // system dictionary, the string table and the code cache. 3290 const int so = SO_AllClasses | SO_Strings | SO_CodeCache; 3291 3292 // Need cleared claim bits for the strong roots processing 3293 ClassLoaderDataGraph::clear_claimed_marks(); 3294 3295 process_strong_roots(true, // activate StrongRootsScope 3296 false, // we set "is scavenging" to false, 3297 // so we don't reset the dirty cards. 3298 ScanningOption(so), // roots scanning options 3299 &rootsCl, 3300 &blobsCl, 3301 &klassCl 3302 ); 3303 3304 bool failures = rootsCl.failures(); 3305 3306 if (vo != VerifyOption_G1UseMarkWord) { 3307 // If we're verifying during a full GC then the region sets 3308 // will have been torn down at the start of the GC. Therefore 3309 // verifying the region sets will fail. So we only verify 3310 // the region sets when not in a full GC. 3311 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3312 verify_region_sets(); 3313 } 3314 3315 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3316 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3317 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3318 "sanity check"); 3319 3320 G1ParVerifyTask task(this, vo); 3321 assert(UseDynamicNumberOfGCThreads || 3322 workers()->active_workers() == workers()->total_workers(), 3323 "If not dynamic should be using all the workers"); 3324 int n_workers = workers()->active_workers(); 3325 set_par_threads(n_workers); 3326 workers()->run_task(&task); 3327 set_par_threads(0); 3328 if (task.failures()) { 3329 failures = true; 3330 } 3331 3332 // Checks that the expected amount of parallel work was done. 3333 // The implication is that n_workers is > 0. 3334 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3335 "sanity check"); 3336 3337 reset_heap_region_claim_values(); 3338 3339 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3340 "sanity check"); 3341 } else { 3342 VerifyRegionClosure blk(false, vo); 3343 heap_region_iterate(&blk); 3344 if (blk.failures()) { 3345 failures = true; 3346 } 3347 } 3348 if (!silent) gclog_or_tty->print("RemSet "); 3349 rem_set()->verify(); 3350 3351 if (failures) { 3352 gclog_or_tty->print_cr("Heap:"); 3353 // It helps to have the per-region information in the output to 3354 // help us track down what went wrong. This is why we call 3355 // print_extended_on() instead of print_on(). 3356 print_extended_on(gclog_or_tty); 3357 gclog_or_tty->print_cr(""); 3358 #ifndef PRODUCT 3359 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3360 concurrent_mark()->print_reachable("at-verification-failure", 3361 vo, false /* all */); 3362 } 3363 #endif 3364 gclog_or_tty->flush(); 3365 } 3366 guarantee(!failures, "there should not have been any failures"); 3367 } else { 3368 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) "); 3369 } 3370 } 3371 3372 class PrintRegionClosure: public HeapRegionClosure { 3373 outputStream* _st; 3374 public: 3375 PrintRegionClosure(outputStream* st) : _st(st) {} 3376 bool doHeapRegion(HeapRegion* r) { 3377 r->print_on(_st); 3378 return false; 3379 } 3380 }; 3381 3382 void G1CollectedHeap::print_on(outputStream* st) const { 3383 st->print(" %-20s", "garbage-first heap"); 3384 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3385 capacity()/K, used_unlocked()/K); 3386 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3387 _g1_storage.low_boundary(), 3388 _g1_storage.high(), 3389 _g1_storage.high_boundary()); 3390 st->cr(); 3391 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3392 uint young_regions = _young_list->length(); 3393 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3394 (size_t) young_regions * HeapRegion::GrainBytes / K); 3395 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3396 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3397 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3398 st->cr(); 3399 } 3400 3401 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3402 print_on(st); 3403 3404 // Print the per-region information. 3405 st->cr(); 3406 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3407 "HS=humongous(starts), HC=humongous(continues), " 3408 "CS=collection set, F=free, TS=gc time stamp, " 3409 "PTAMS=previous top-at-mark-start, " 3410 "NTAMS=next top-at-mark-start)"); 3411 PrintRegionClosure blk(st); 3412 heap_region_iterate(&blk); 3413 } 3414 3415 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3416 if (G1CollectedHeap::use_parallel_gc_threads()) { 3417 workers()->print_worker_threads_on(st); 3418 } 3419 _cmThread->print_on(st); 3420 st->cr(); 3421 _cm->print_worker_threads_on(st); 3422 _cg1r->print_worker_threads_on(st); 3423 st->cr(); 3424 } 3425 3426 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3427 if (G1CollectedHeap::use_parallel_gc_threads()) { 3428 workers()->threads_do(tc); 3429 } 3430 tc->do_thread(_cmThread); 3431 _cg1r->threads_do(tc); 3432 } 3433 3434 void G1CollectedHeap::print_tracing_info() const { 3435 // We'll overload this to mean "trace GC pause statistics." 3436 if (TraceGen0Time || TraceGen1Time) { 3437 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3438 // to that. 3439 g1_policy()->print_tracing_info(); 3440 } 3441 if (G1SummarizeRSetStats) { 3442 g1_rem_set()->print_summary_info(); 3443 } 3444 if (G1SummarizeConcMark) { 3445 concurrent_mark()->print_summary_info(); 3446 } 3447 g1_policy()->print_yg_surv_rate_info(); 3448 SpecializationStats::print(); 3449 } 3450 3451 #ifndef PRODUCT 3452 // Helpful for debugging RSet issues. 3453 3454 class PrintRSetsClosure : public HeapRegionClosure { 3455 private: 3456 const char* _msg; 3457 size_t _occupied_sum; 3458 3459 public: 3460 bool doHeapRegion(HeapRegion* r) { 3461 HeapRegionRemSet* hrrs = r->rem_set(); 3462 size_t occupied = hrrs->occupied(); 3463 _occupied_sum += occupied; 3464 3465 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3466 HR_FORMAT_PARAMS(r)); 3467 if (occupied == 0) { 3468 gclog_or_tty->print_cr(" RSet is empty"); 3469 } else { 3470 hrrs->print(); 3471 } 3472 gclog_or_tty->print_cr("----------"); 3473 return false; 3474 } 3475 3476 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3477 gclog_or_tty->cr(); 3478 gclog_or_tty->print_cr("========================================"); 3479 gclog_or_tty->print_cr(msg); 3480 gclog_or_tty->cr(); 3481 } 3482 3483 ~PrintRSetsClosure() { 3484 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3485 gclog_or_tty->print_cr("========================================"); 3486 gclog_or_tty->cr(); 3487 } 3488 }; 3489 3490 void G1CollectedHeap::print_cset_rsets() { 3491 PrintRSetsClosure cl("Printing CSet RSets"); 3492 collection_set_iterate(&cl); 3493 } 3494 3495 void G1CollectedHeap::print_all_rsets() { 3496 PrintRSetsClosure cl("Printing All RSets");; 3497 heap_region_iterate(&cl); 3498 } 3499 #endif // PRODUCT 3500 3501 G1CollectedHeap* G1CollectedHeap::heap() { 3502 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3503 "not a garbage-first heap"); 3504 return _g1h; 3505 } 3506 3507 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3508 // always_do_update_barrier = false; 3509 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3510 // Call allocation profiler 3511 AllocationProfiler::iterate_since_last_gc(); 3512 // Fill TLAB's and such 3513 ensure_parsability(true); 3514 } 3515 3516 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { 3517 // FIXME: what is this about? 3518 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3519 // is set. 3520 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3521 "derived pointer present")); 3522 // always_do_update_barrier = true; 3523 3524 // We have just completed a GC. Update the soft reference 3525 // policy with the new heap occupancy 3526 Universe::update_heap_info_at_gc(); 3527 } 3528 3529 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3530 unsigned int gc_count_before, 3531 bool* succeeded) { 3532 assert_heap_not_locked_and_not_at_safepoint(); 3533 g1_policy()->record_stop_world_start(); 3534 VM_G1IncCollectionPause op(gc_count_before, 3535 word_size, 3536 false, /* should_initiate_conc_mark */ 3537 g1_policy()->max_pause_time_ms(), 3538 GCCause::_g1_inc_collection_pause); 3539 VMThread::execute(&op); 3540 3541 HeapWord* result = op.result(); 3542 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3543 assert(result == NULL || ret_succeeded, 3544 "the result should be NULL if the VM did not succeed"); 3545 *succeeded = ret_succeeded; 3546 3547 assert_heap_not_locked(); 3548 return result; 3549 } 3550 3551 void 3552 G1CollectedHeap::doConcurrentMark() { 3553 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3554 if (!_cmThread->in_progress()) { 3555 _cmThread->set_started(); 3556 CGC_lock->notify(); 3557 } 3558 } 3559 3560 size_t G1CollectedHeap::pending_card_num() { 3561 size_t extra_cards = 0; 3562 JavaThread *curr = Threads::first(); 3563 while (curr != NULL) { 3564 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3565 extra_cards += dcq.size(); 3566 curr = curr->next(); 3567 } 3568 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3569 size_t buffer_size = dcqs.buffer_size(); 3570 size_t buffer_num = dcqs.completed_buffers_num(); 3571 3572 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3573 // in bytes - not the number of 'entries'. We need to convert 3574 // into a number of cards. 3575 return (buffer_size * buffer_num + extra_cards) / oopSize; 3576 } 3577 3578 size_t G1CollectedHeap::cards_scanned() { 3579 return g1_rem_set()->cardsScanned(); 3580 } 3581 3582 void 3583 G1CollectedHeap::setup_surviving_young_words() { 3584 assert(_surviving_young_words == NULL, "pre-condition"); 3585 uint array_length = g1_policy()->young_cset_region_length(); 3586 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3587 if (_surviving_young_words == NULL) { 3588 vm_exit_out_of_memory(sizeof(size_t) * array_length, 3589 "Not enough space for young surv words summary."); 3590 } 3591 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3592 #ifdef ASSERT 3593 for (uint i = 0; i < array_length; ++i) { 3594 assert( _surviving_young_words[i] == 0, "memset above" ); 3595 } 3596 #endif // !ASSERT 3597 } 3598 3599 void 3600 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3601 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3602 uint array_length = g1_policy()->young_cset_region_length(); 3603 for (uint i = 0; i < array_length; ++i) { 3604 _surviving_young_words[i] += surv_young_words[i]; 3605 } 3606 } 3607 3608 void 3609 G1CollectedHeap::cleanup_surviving_young_words() { 3610 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3611 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3612 _surviving_young_words = NULL; 3613 } 3614 3615 #ifdef ASSERT 3616 class VerifyCSetClosure: public HeapRegionClosure { 3617 public: 3618 bool doHeapRegion(HeapRegion* hr) { 3619 // Here we check that the CSet region's RSet is ready for parallel 3620 // iteration. The fields that we'll verify are only manipulated 3621 // when the region is part of a CSet and is collected. Afterwards, 3622 // we reset these fields when we clear the region's RSet (when the 3623 // region is freed) so they are ready when the region is 3624 // re-allocated. The only exception to this is if there's an 3625 // evacuation failure and instead of freeing the region we leave 3626 // it in the heap. In that case, we reset these fields during 3627 // evacuation failure handling. 3628 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3629 3630 // Here's a good place to add any other checks we'd like to 3631 // perform on CSet regions. 3632 return false; 3633 } 3634 }; 3635 #endif // ASSERT 3636 3637 #if TASKQUEUE_STATS 3638 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3639 st->print_raw_cr("GC Task Stats"); 3640 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3641 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3642 } 3643 3644 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3645 print_taskqueue_stats_hdr(st); 3646 3647 TaskQueueStats totals; 3648 const int n = workers() != NULL ? workers()->total_workers() : 1; 3649 for (int i = 0; i < n; ++i) { 3650 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3651 totals += task_queue(i)->stats; 3652 } 3653 st->print_raw("tot "); totals.print(st); st->cr(); 3654 3655 DEBUG_ONLY(totals.verify()); 3656 } 3657 3658 void G1CollectedHeap::reset_taskqueue_stats() { 3659 const int n = workers() != NULL ? workers()->total_workers() : 1; 3660 for (int i = 0; i < n; ++i) { 3661 task_queue(i)->stats.reset(); 3662 } 3663 } 3664 #endif // TASKQUEUE_STATS 3665 3666 bool 3667 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3668 assert_at_safepoint(true /* should_be_vm_thread */); 3669 guarantee(!is_gc_active(), "collection is not reentrant"); 3670 3671 if (GC_locker::check_active_before_gc()) { 3672 return false; 3673 } 3674 3675 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3676 ResourceMark rm; 3677 3678 print_heap_before_gc(); 3679 3680 HRSPhaseSetter x(HRSPhaseEvacuation); 3681 verify_region_sets_optional(); 3682 verify_dirty_young_regions(); 3683 3684 // This call will decide whether this pause is an initial-mark 3685 // pause. If it is, during_initial_mark_pause() will return true 3686 // for the duration of this pause. 3687 g1_policy()->decide_on_conc_mark_initiation(); 3688 3689 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3690 assert(!g1_policy()->during_initial_mark_pause() || 3691 g1_policy()->gcs_are_young(), "sanity"); 3692 3693 // We also do not allow mixed GCs during marking. 3694 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3695 3696 // Record whether this pause is an initial mark. When the current 3697 // thread has completed its logging output and it's safe to signal 3698 // the CM thread, the flag's value in the policy has been reset. 3699 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3700 3701 // Inner scope for scope based logging, timers, and stats collection 3702 { 3703 if (g1_policy()->during_initial_mark_pause()) { 3704 // We are about to start a marking cycle, so we increment the 3705 // full collection counter. 3706 increment_old_marking_cycles_started(); 3707 } 3708 // if the log level is "finer" is on, we'll print long statistics information 3709 // in the collector policy code, so let's not print this as the output 3710 // is messy if we do. 3711 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps); 3712 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3713 3714 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3715 workers()->active_workers() : 1); 3716 double pause_start_sec = os::elapsedTime(); 3717 g1_policy()->phase_times()->note_gc_start(active_workers); 3718 bool initial_mark_gc = g1_policy()->during_initial_mark_pause(); 3719 3720 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3721 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3722 3723 // If the secondary_free_list is not empty, append it to the 3724 // free_list. No need to wait for the cleanup operation to finish; 3725 // the region allocation code will check the secondary_free_list 3726 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3727 // set, skip this step so that the region allocation code has to 3728 // get entries from the secondary_free_list. 3729 if (!G1StressConcRegionFreeing) { 3730 append_secondary_free_list_if_not_empty_with_lock(); 3731 } 3732 3733 assert(check_young_list_well_formed(), 3734 "young list should be well formed"); 3735 3736 // Don't dynamically change the number of GC threads this early. A value of 3737 // 0 is used to indicate serial work. When parallel work is done, 3738 // it will be set. 3739 3740 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3741 IsGCActiveMark x; 3742 3743 gc_prologue(false); 3744 increment_total_collections(false /* full gc */); 3745 increment_gc_time_stamp(); 3746 3747 verify_before_gc(); 3748 3749 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3750 3751 // Please see comment in g1CollectedHeap.hpp and 3752 // G1CollectedHeap::ref_processing_init() to see how 3753 // reference processing currently works in G1. 3754 3755 // Enable discovery in the STW reference processor 3756 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 3757 true /*verify_no_refs*/); 3758 3759 { 3760 // We want to temporarily turn off discovery by the 3761 // CM ref processor, if necessary, and turn it back on 3762 // on again later if we do. Using a scoped 3763 // NoRefDiscovery object will do this. 3764 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3765 3766 // Forget the current alloc region (we might even choose it to be part 3767 // of the collection set!). 3768 release_mutator_alloc_region(); 3769 3770 // We should call this after we retire the mutator alloc 3771 // region(s) so that all the ALLOC / RETIRE events are generated 3772 // before the start GC event. 3773 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3774 3775 // This timing is only used by the ergonomics to handle our pause target. 3776 // It is unclear why this should not include the full pause. We will 3777 // investigate this in CR 7178365. 3778 // 3779 // Preserving the old comment here if that helps the investigation: 3780 // 3781 // The elapsed time induced by the start time below deliberately elides 3782 // the possible verification above. 3783 double sample_start_time_sec = os::elapsedTime(); 3784 size_t start_used_bytes = used(); 3785 3786 #if YOUNG_LIST_VERBOSE 3787 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3788 _young_list->print(); 3789 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3790 #endif // YOUNG_LIST_VERBOSE 3791 3792 g1_policy()->record_collection_pause_start(sample_start_time_sec, 3793 start_used_bytes); 3794 3795 double scan_wait_start = os::elapsedTime(); 3796 // We have to wait until the CM threads finish scanning the 3797 // root regions as it's the only way to ensure that all the 3798 // objects on them have been correctly scanned before we start 3799 // moving them during the GC. 3800 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3801 double wait_time_ms = 0.0; 3802 if (waited) { 3803 double scan_wait_end = os::elapsedTime(); 3804 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3805 } 3806 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3807 3808 #if YOUNG_LIST_VERBOSE 3809 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3810 _young_list->print(); 3811 #endif // YOUNG_LIST_VERBOSE 3812 3813 if (g1_policy()->during_initial_mark_pause()) { 3814 concurrent_mark()->checkpointRootsInitialPre(); 3815 } 3816 3817 #if YOUNG_LIST_VERBOSE 3818 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3819 _young_list->print(); 3820 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3821 #endif // YOUNG_LIST_VERBOSE 3822 3823 g1_policy()->finalize_cset(target_pause_time_ms); 3824 3825 _cm->note_start_of_gc(); 3826 // We should not verify the per-thread SATB buffers given that 3827 // we have not filtered them yet (we'll do so during the 3828 // GC). We also call this after finalize_cset() to 3829 // ensure that the CSet has been finalized. 3830 _cm->verify_no_cset_oops(true /* verify_stacks */, 3831 true /* verify_enqueued_buffers */, 3832 false /* verify_thread_buffers */, 3833 true /* verify_fingers */); 3834 3835 if (_hr_printer.is_active()) { 3836 HeapRegion* hr = g1_policy()->collection_set(); 3837 while (hr != NULL) { 3838 G1HRPrinter::RegionType type; 3839 if (!hr->is_young()) { 3840 type = G1HRPrinter::Old; 3841 } else if (hr->is_survivor()) { 3842 type = G1HRPrinter::Survivor; 3843 } else { 3844 type = G1HRPrinter::Eden; 3845 } 3846 _hr_printer.cset(hr); 3847 hr = hr->next_in_collection_set(); 3848 } 3849 } 3850 3851 #ifdef ASSERT 3852 VerifyCSetClosure cl; 3853 collection_set_iterate(&cl); 3854 #endif // ASSERT 3855 3856 setup_surviving_young_words(); 3857 3858 // Initialize the GC alloc regions. 3859 init_gc_alloc_regions(); 3860 3861 // Actually do the work... 3862 evacuate_collection_set(); 3863 3864 // We do this to mainly verify the per-thread SATB buffers 3865 // (which have been filtered by now) since we didn't verify 3866 // them earlier. No point in re-checking the stacks / enqueued 3867 // buffers given that the CSet has not changed since last time 3868 // we checked. 3869 _cm->verify_no_cset_oops(false /* verify_stacks */, 3870 false /* verify_enqueued_buffers */, 3871 true /* verify_thread_buffers */, 3872 true /* verify_fingers */); 3873 3874 free_collection_set(g1_policy()->collection_set()); 3875 g1_policy()->clear_collection_set(); 3876 3877 cleanup_surviving_young_words(); 3878 3879 // Start a new incremental collection set for the next pause. 3880 g1_policy()->start_incremental_cset_building(); 3881 3882 // Clear the _cset_fast_test bitmap in anticipation of adding 3883 // regions to the incremental collection set for the next 3884 // evacuation pause. 3885 clear_cset_fast_test(); 3886 3887 _young_list->reset_sampled_info(); 3888 3889 // Don't check the whole heap at this point as the 3890 // GC alloc regions from this pause have been tagged 3891 // as survivors and moved on to the survivor list. 3892 // Survivor regions will fail the !is_young() check. 3893 assert(check_young_list_empty(false /* check_heap */), 3894 "young list should be empty"); 3895 3896 #if YOUNG_LIST_VERBOSE 3897 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3898 _young_list->print(); 3899 #endif // YOUNG_LIST_VERBOSE 3900 3901 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3902 _young_list->first_survivor_region(), 3903 _young_list->last_survivor_region()); 3904 3905 _young_list->reset_auxilary_lists(); 3906 3907 if (evacuation_failed()) { 3908 _summary_bytes_used = recalculate_used(); 3909 } else { 3910 // The "used" of the the collection set have already been subtracted 3911 // when they were freed. Add in the bytes evacuated. 3912 _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); 3913 } 3914 3915 if (g1_policy()->during_initial_mark_pause()) { 3916 // We have to do this before we notify the CM threads that 3917 // they can start working to make sure that all the 3918 // appropriate initialization is done on the CM object. 3919 concurrent_mark()->checkpointRootsInitialPost(); 3920 set_marking_started(); 3921 // Note that we don't actually trigger the CM thread at 3922 // this point. We do that later when we're sure that 3923 // the current thread has completed its logging output. 3924 } 3925 3926 allocate_dummy_regions(); 3927 3928 #if YOUNG_LIST_VERBOSE 3929 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 3930 _young_list->print(); 3931 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3932 #endif // YOUNG_LIST_VERBOSE 3933 3934 init_mutator_alloc_region(); 3935 3936 { 3937 size_t expand_bytes = g1_policy()->expansion_amount(); 3938 if (expand_bytes > 0) { 3939 size_t bytes_before = capacity(); 3940 // No need for an ergo verbose message here, 3941 // expansion_amount() does this when it returns a value > 0. 3942 if (!expand(expand_bytes)) { 3943 // We failed to expand the heap so let's verify that 3944 // committed/uncommitted amount match the backing store 3945 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 3946 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 3947 } 3948 } 3949 } 3950 3951 // We redo the verificaiton but now wrt to the new CSet which 3952 // has just got initialized after the previous CSet was freed. 3953 _cm->verify_no_cset_oops(true /* verify_stacks */, 3954 true /* verify_enqueued_buffers */, 3955 true /* verify_thread_buffers */, 3956 true /* verify_fingers */); 3957 _cm->note_end_of_gc(); 3958 3959 // This timing is only used by the ergonomics to handle our pause target. 3960 // It is unclear why this should not include the full pause. We will 3961 // investigate this in CR 7178365. 3962 double sample_end_time_sec = os::elapsedTime(); 3963 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3964 g1_policy()->record_collection_pause_end(pause_time_ms); 3965 3966 MemoryService::track_memory_usage(); 3967 3968 // In prepare_for_verify() below we'll need to scan the deferred 3969 // update buffers to bring the RSets up-to-date if 3970 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3971 // the update buffers we'll probably need to scan cards on the 3972 // regions we just allocated to (i.e., the GC alloc 3973 // regions). However, during the last GC we called 3974 // set_saved_mark() on all the GC alloc regions, so card 3975 // scanning might skip the [saved_mark_word()...top()] area of 3976 // those regions (i.e., the area we allocated objects into 3977 // during the last GC). But it shouldn't. Given that 3978 // saved_mark_word() is conditional on whether the GC time stamp 3979 // on the region is current or not, by incrementing the GC time 3980 // stamp here we invalidate all the GC time stamps on all the 3981 // regions and saved_mark_word() will simply return top() for 3982 // all the regions. This is a nicer way of ensuring this rather 3983 // than iterating over the regions and fixing them. In fact, the 3984 // GC time stamp increment here also ensures that 3985 // saved_mark_word() will return top() between pauses, i.e., 3986 // during concurrent refinement. So we don't need the 3987 // is_gc_active() check to decided which top to use when 3988 // scanning cards (see CR 7039627). 3989 increment_gc_time_stamp(); 3990 3991 verify_after_gc(); 3992 3993 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3994 ref_processor_stw()->verify_no_references_recorded(); 3995 3996 // CM reference discovery will be re-enabled if necessary. 3997 } 3998 3999 // We should do this after we potentially expand the heap so 4000 // that all the COMMIT events are generated before the end GC 4001 // event, and after we retire the GC alloc regions so that all 4002 // RETIRE events are generated before the end GC event. 4003 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4004 4005 if (mark_in_progress()) { 4006 concurrent_mark()->update_g1_committed(); 4007 } 4008 4009 #ifdef TRACESPINNING 4010 ParallelTaskTerminator::print_termination_counts(); 4011 #endif 4012 4013 gc_epilogue(false); 4014 4015 if (G1Log::fine()) { 4016 if (PrintGCTimeStamps) { 4017 gclog_or_tty->stamp(); 4018 gclog_or_tty->print(": "); 4019 } 4020 4021 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 4022 .append(g1_policy()->gcs_are_young() ? " (young)" : " (mixed)") 4023 .append(initial_mark_gc ? " (initial-mark)" : ""); 4024 4025 double pause_time_sec = os::elapsedTime() - pause_start_sec; 4026 4027 if (G1Log::finer()) { 4028 if (evacuation_failed()) { 4029 gc_cause_str.append(" (to-space exhausted)"); 4030 } 4031 gclog_or_tty->print_cr("[%s, %3.7f secs]", (const char*)gc_cause_str, pause_time_sec); 4032 g1_policy()->phase_times()->note_gc_end(); 4033 g1_policy()->phase_times()->print(pause_time_sec); 4034 g1_policy()->print_detailed_heap_transition(); 4035 } else { 4036 if (evacuation_failed()) { 4037 gc_cause_str.append("--"); 4038 } 4039 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 4040 g1_policy()->print_heap_transition(); 4041 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 4042 } 4043 } 4044 } 4045 4046 // It is not yet to safe to tell the concurrent mark to 4047 // start as we have some optional output below. We don't want the 4048 // output from the concurrent mark thread interfering with this 4049 // logging output either. 4050 4051 _hrs.verify_optional(); 4052 verify_region_sets_optional(); 4053 4054 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4055 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4056 4057 print_heap_after_gc(); 4058 4059 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4060 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4061 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4062 // before any GC notifications are raised. 4063 g1mm()->update_sizes(); 4064 } 4065 4066 if (G1SummarizeRSetStats && 4067 (G1SummarizeRSetStatsPeriod > 0) && 4068 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 4069 g1_rem_set()->print_summary_info(); 4070 } 4071 4072 // It should now be safe to tell the concurrent mark thread to start 4073 // without its logging output interfering with the logging output 4074 // that came from the pause. 4075 4076 if (should_start_conc_mark) { 4077 // CAUTION: after the doConcurrentMark() call below, 4078 // the concurrent marking thread(s) could be running 4079 // concurrently with us. Make sure that anything after 4080 // this point does not assume that we are the only GC thread 4081 // running. Note: of course, the actual marking work will 4082 // not start until the safepoint itself is released in 4083 // ConcurrentGCThread::safepoint_desynchronize(). 4084 doConcurrentMark(); 4085 } 4086 4087 return true; 4088 } 4089 4090 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4091 { 4092 size_t gclab_word_size; 4093 switch (purpose) { 4094 case GCAllocForSurvived: 4095 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4096 break; 4097 case GCAllocForTenured: 4098 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4099 break; 4100 default: 4101 assert(false, "unknown GCAllocPurpose"); 4102 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4103 break; 4104 } 4105 4106 // Prevent humongous PLAB sizes for two reasons: 4107 // * PLABs are allocated using a similar paths as oops, but should 4108 // never be in a humongous region 4109 // * Allowing humongous PLABs needlessly churns the region free lists 4110 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4111 } 4112 4113 void G1CollectedHeap::init_mutator_alloc_region() { 4114 assert(_mutator_alloc_region.get() == NULL, "pre-condition"); 4115 _mutator_alloc_region.init(); 4116 } 4117 4118 void G1CollectedHeap::release_mutator_alloc_region() { 4119 _mutator_alloc_region.release(); 4120 assert(_mutator_alloc_region.get() == NULL, "post-condition"); 4121 } 4122 4123 void G1CollectedHeap::init_gc_alloc_regions() { 4124 assert_at_safepoint(true /* should_be_vm_thread */); 4125 4126 _survivor_gc_alloc_region.init(); 4127 _old_gc_alloc_region.init(); 4128 HeapRegion* retained_region = _retained_old_gc_alloc_region; 4129 _retained_old_gc_alloc_region = NULL; 4130 4131 // We will discard the current GC alloc region if: 4132 // a) it's in the collection set (it can happen!), 4133 // b) it's already full (no point in using it), 4134 // c) it's empty (this means that it was emptied during 4135 // a cleanup and it should be on the free list now), or 4136 // d) it's humongous (this means that it was emptied 4137 // during a cleanup and was added to the free list, but 4138 // has been subseqently used to allocate a humongous 4139 // object that may be less than the region size). 4140 if (retained_region != NULL && 4141 !retained_region->in_collection_set() && 4142 !(retained_region->top() == retained_region->end()) && 4143 !retained_region->is_empty() && 4144 !retained_region->isHumongous()) { 4145 retained_region->set_saved_mark(); 4146 // The retained region was added to the old region set when it was 4147 // retired. We have to remove it now, since we don't allow regions 4148 // we allocate to in the region sets. We'll re-add it later, when 4149 // it's retired again. 4150 _old_set.remove(retained_region); 4151 bool during_im = g1_policy()->during_initial_mark_pause(); 4152 retained_region->note_start_of_copying(during_im); 4153 _old_gc_alloc_region.set(retained_region); 4154 _hr_printer.reuse(retained_region); 4155 } 4156 } 4157 4158 void G1CollectedHeap::release_gc_alloc_regions() { 4159 _survivor_gc_alloc_region.release(); 4160 // If we have an old GC alloc region to release, we'll save it in 4161 // _retained_old_gc_alloc_region. If we don't 4162 // _retained_old_gc_alloc_region will become NULL. This is what we 4163 // want either way so no reason to check explicitly for either 4164 // condition. 4165 _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); 4166 4167 if (ResizePLAB) { 4168 _survivor_plab_stats.adjust_desired_plab_sz(); 4169 _old_plab_stats.adjust_desired_plab_sz(); 4170 } 4171 } 4172 4173 void G1CollectedHeap::abandon_gc_alloc_regions() { 4174 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); 4175 assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); 4176 _retained_old_gc_alloc_region = NULL; 4177 } 4178 4179 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4180 _drain_in_progress = false; 4181 set_evac_failure_closure(cl); 4182 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4183 } 4184 4185 void G1CollectedHeap::finalize_for_evac_failure() { 4186 assert(_evac_failure_scan_stack != NULL && 4187 _evac_failure_scan_stack->length() == 0, 4188 "Postcondition"); 4189 assert(!_drain_in_progress, "Postcondition"); 4190 delete _evac_failure_scan_stack; 4191 _evac_failure_scan_stack = NULL; 4192 } 4193 4194 void G1CollectedHeap::remove_self_forwarding_pointers() { 4195 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4196 4197 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4198 4199 if (G1CollectedHeap::use_parallel_gc_threads()) { 4200 set_par_threads(); 4201 workers()->run_task(&rsfp_task); 4202 set_par_threads(0); 4203 } else { 4204 rsfp_task.work(0); 4205 } 4206 4207 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); 4208 4209 // Reset the claim values in the regions in the collection set. 4210 reset_cset_heap_region_claim_values(); 4211 4212 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4213 4214 // Now restore saved marks, if any. 4215 if (_objs_with_preserved_marks != NULL) { 4216 assert(_preserved_marks_of_objs != NULL, "Both or none."); 4217 guarantee(_objs_with_preserved_marks->length() == 4218 _preserved_marks_of_objs->length(), "Both or none."); 4219 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) { 4220 oop obj = _objs_with_preserved_marks->at(i); 4221 markOop m = _preserved_marks_of_objs->at(i); 4222 obj->set_mark(m); 4223 } 4224 4225 // Delete the preserved marks growable arrays (allocated on the C heap). 4226 delete _objs_with_preserved_marks; 4227 delete _preserved_marks_of_objs; 4228 _objs_with_preserved_marks = NULL; 4229 _preserved_marks_of_objs = NULL; 4230 } 4231 } 4232 4233 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4234 _evac_failure_scan_stack->push(obj); 4235 } 4236 4237 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4238 assert(_evac_failure_scan_stack != NULL, "precondition"); 4239 4240 while (_evac_failure_scan_stack->length() > 0) { 4241 oop obj = _evac_failure_scan_stack->pop(); 4242 _evac_failure_closure->set_region(heap_region_containing(obj)); 4243 obj->oop_iterate_backwards(_evac_failure_closure); 4244 } 4245 } 4246 4247 oop 4248 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, 4249 oop old) { 4250 assert(obj_in_cs(old), 4251 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4252 (HeapWord*) old)); 4253 markOop m = old->mark(); 4254 oop forward_ptr = old->forward_to_atomic(old); 4255 if (forward_ptr == NULL) { 4256 // Forward-to-self succeeded. 4257 4258 if (_evac_failure_closure != cl) { 4259 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4260 assert(!_drain_in_progress, 4261 "Should only be true while someone holds the lock."); 4262 // Set the global evac-failure closure to the current thread's. 4263 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4264 set_evac_failure_closure(cl); 4265 // Now do the common part. 4266 handle_evacuation_failure_common(old, m); 4267 // Reset to NULL. 4268 set_evac_failure_closure(NULL); 4269 } else { 4270 // The lock is already held, and this is recursive. 4271 assert(_drain_in_progress, "This should only be the recursive case."); 4272 handle_evacuation_failure_common(old, m); 4273 } 4274 return old; 4275 } else { 4276 // Forward-to-self failed. Either someone else managed to allocate 4277 // space for this object (old != forward_ptr) or they beat us in 4278 // self-forwarding it (old == forward_ptr). 4279 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4280 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4281 "should not be in the CSet", 4282 (HeapWord*) old, (HeapWord*) forward_ptr)); 4283 return forward_ptr; 4284 } 4285 } 4286 4287 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4288 set_evacuation_failed(true); 4289 4290 preserve_mark_if_necessary(old, m); 4291 4292 HeapRegion* r = heap_region_containing(old); 4293 if (!r->evacuation_failed()) { 4294 r->set_evacuation_failed(true); 4295 _hr_printer.evac_failure(r); 4296 } 4297 4298 push_on_evac_failure_scan_stack(old); 4299 4300 if (!_drain_in_progress) { 4301 // prevent recursion in copy_to_survivor_space() 4302 _drain_in_progress = true; 4303 drain_evac_failure_scan_stack(); 4304 _drain_in_progress = false; 4305 } 4306 } 4307 4308 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4309 assert(evacuation_failed(), "Oversaving!"); 4310 // We want to call the "for_promotion_failure" version only in the 4311 // case of a promotion failure. 4312 if (m->must_be_preserved_for_promotion_failure(obj)) { 4313 if (_objs_with_preserved_marks == NULL) { 4314 assert(_preserved_marks_of_objs == NULL, "Both or none."); 4315 _objs_with_preserved_marks = 4316 new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4317 _preserved_marks_of_objs = 4318 new (ResourceObj::C_HEAP, mtGC) GrowableArray<markOop>(40, true); 4319 } 4320 _objs_with_preserved_marks->push(obj); 4321 _preserved_marks_of_objs->push(m); 4322 } 4323 } 4324 4325 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4326 size_t word_size) { 4327 if (purpose == GCAllocForSurvived) { 4328 HeapWord* result = survivor_attempt_allocation(word_size); 4329 if (result != NULL) { 4330 return result; 4331 } else { 4332 // Let's try to allocate in the old gen in case we can fit the 4333 // object there. 4334 return old_attempt_allocation(word_size); 4335 } 4336 } else { 4337 assert(purpose == GCAllocForTenured, "sanity"); 4338 HeapWord* result = old_attempt_allocation(word_size); 4339 if (result != NULL) { 4340 return result; 4341 } else { 4342 // Let's try to allocate in the survivors in case we can fit the 4343 // object there. 4344 return survivor_attempt_allocation(word_size); 4345 } 4346 } 4347 4348 ShouldNotReachHere(); 4349 // Trying to keep some compilers happy. 4350 return NULL; 4351 } 4352 4353 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) : 4354 ParGCAllocBuffer(gclab_word_size), _retired(false) { } 4355 4356 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num) 4357 : _g1h(g1h), 4358 _refs(g1h->task_queue(queue_num)), 4359 _dcq(&g1h->dirty_card_queue_set()), 4360 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()), 4361 _g1_rem(g1h->g1_rem_set()), 4362 _hash_seed(17), _queue_num(queue_num), 4363 _term_attempts(0), 4364 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 4365 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 4366 _age_table(false), 4367 _strong_roots_time(0), _term_time(0), 4368 _alloc_buffer_waste(0), _undo_waste(0) { 4369 // we allocate G1YoungSurvRateNumRegions plus one entries, since 4370 // we "sacrifice" entry 0 to keep track of surviving bytes for 4371 // non-young regions (where the age is -1) 4372 // We also add a few elements at the beginning and at the end in 4373 // an attempt to eliminate cache contention 4374 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); 4375 uint array_length = PADDING_ELEM_NUM + 4376 real_length + 4377 PADDING_ELEM_NUM; 4378 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC); 4379 if (_surviving_young_words_base == NULL) 4380 vm_exit_out_of_memory(array_length * sizeof(size_t), 4381 "Not enough space for young surv histo."); 4382 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 4383 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t)); 4384 4385 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 4386 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 4387 4388 _start = os::elapsedTime(); 4389 } 4390 4391 void 4392 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 4393 { 4394 st->print_raw_cr("GC Termination Stats"); 4395 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 4396 " ------waste (KiB)------"); 4397 st->print_raw_cr("thr ms ms % ms % attempts" 4398 " total alloc undo"); 4399 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 4400 " ------- ------- -------"); 4401 } 4402 4403 void 4404 G1ParScanThreadState::print_termination_stats(int i, 4405 outputStream* const st) const 4406 { 4407 const double elapsed_ms = elapsed_time() * 1000.0; 4408 const double s_roots_ms = strong_roots_time() * 1000.0; 4409 const double term_ms = term_time() * 1000.0; 4410 st->print_cr("%3d %9.2f %9.2f %6.2f " 4411 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4412 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4413 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 4414 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 4415 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 4416 alloc_buffer_waste() * HeapWordSize / K, 4417 undo_waste() * HeapWordSize / K); 4418 } 4419 4420 #ifdef ASSERT 4421 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 4422 assert(ref != NULL, "invariant"); 4423 assert(UseCompressedOops, "sanity"); 4424 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); 4425 oop p = oopDesc::load_decode_heap_oop(ref); 4426 assert(_g1h->is_in_g1_reserved(p), 4427 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4428 return true; 4429 } 4430 4431 bool G1ParScanThreadState::verify_ref(oop* ref) const { 4432 assert(ref != NULL, "invariant"); 4433 if (has_partial_array_mask(ref)) { 4434 // Must be in the collection set--it's already been copied. 4435 oop p = clear_partial_array_mask(ref); 4436 assert(_g1h->obj_in_cs(p), 4437 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4438 } else { 4439 oop p = oopDesc::load_decode_heap_oop(ref); 4440 assert(_g1h->is_in_g1_reserved(p), 4441 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4442 } 4443 return true; 4444 } 4445 4446 bool G1ParScanThreadState::verify_task(StarTask ref) const { 4447 if (ref.is_narrow()) { 4448 return verify_ref((narrowOop*) ref); 4449 } else { 4450 return verify_ref((oop*) ref); 4451 } 4452 } 4453 #endif // ASSERT 4454 4455 void G1ParScanThreadState::trim_queue() { 4456 assert(_evac_cl != NULL, "not set"); 4457 assert(_evac_failure_cl != NULL, "not set"); 4458 assert(_partial_scan_cl != NULL, "not set"); 4459 4460 StarTask ref; 4461 do { 4462 // Drain the overflow stack first, so other threads can steal. 4463 while (refs()->pop_overflow(ref)) { 4464 deal_with_reference(ref); 4465 } 4466 4467 while (refs()->pop_local(ref)) { 4468 deal_with_reference(ref); 4469 } 4470 } while (!refs()->is_empty()); 4471 } 4472 4473 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, 4474 G1ParScanThreadState* par_scan_state) : 4475 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()), 4476 _par_scan_state(par_scan_state), 4477 _worker_id(par_scan_state->queue_num()), 4478 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()), 4479 _mark_in_progress(_g1->mark_in_progress()) { } 4480 4481 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4482 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) { 4483 #ifdef ASSERT 4484 HeapRegion* hr = _g1->heap_region_containing(obj); 4485 assert(hr != NULL, "sanity"); 4486 assert(!hr->in_collection_set(), "should not mark objects in the CSet"); 4487 #endif // ASSERT 4488 4489 // We know that the object is not moving so it's safe to read its size. 4490 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4491 } 4492 4493 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4494 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4495 ::mark_forwarded_object(oop from_obj, oop to_obj) { 4496 #ifdef ASSERT 4497 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4498 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4499 assert(from_obj != to_obj, "should not be self-forwarded"); 4500 4501 HeapRegion* from_hr = _g1->heap_region_containing(from_obj); 4502 assert(from_hr != NULL, "sanity"); 4503 assert(from_hr->in_collection_set(), "from obj should be in the CSet"); 4504 4505 HeapRegion* to_hr = _g1->heap_region_containing(to_obj); 4506 assert(to_hr != NULL, "sanity"); 4507 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet"); 4508 #endif // ASSERT 4509 4510 // The object might be in the process of being copied by another 4511 // worker so we cannot trust that its to-space image is 4512 // well-formed. So we have to read its size from its from-space 4513 // image which we know should not be changing. 4514 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4515 } 4516 4517 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4518 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4519 ::copy_to_survivor_space(oop old) { 4520 size_t word_sz = old->size(); 4521 HeapRegion* from_region = _g1->heap_region_containing_raw(old); 4522 // +1 to make the -1 indexes valid... 4523 int young_index = from_region->young_index_in_cset()+1; 4524 assert( (from_region->is_young() && young_index > 0) || 4525 (!from_region->is_young() && young_index == 0), "invariant" ); 4526 G1CollectorPolicy* g1p = _g1->g1_policy(); 4527 markOop m = old->mark(); 4528 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 4529 : m->age(); 4530 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 4531 word_sz); 4532 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz); 4533 #ifndef PRODUCT 4534 // Should this evacuation fail? 4535 if (_g1->evacuation_should_fail()) { 4536 if (obj_ptr != NULL) { 4537 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4538 obj_ptr = NULL; 4539 } 4540 } 4541 #endif // !PRODUCT 4542 4543 if (obj_ptr == NULL) { 4544 // This will either forward-to-self, or detect that someone else has 4545 // installed a forwarding pointer. 4546 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4547 return _g1->handle_evacuation_failure_par(cl, old); 4548 } 4549 4550 oop obj = oop(obj_ptr); 4551 4552 // We're going to allocate linearly, so might as well prefetch ahead. 4553 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 4554 4555 oop forward_ptr = old->forward_to_atomic(obj); 4556 if (forward_ptr == NULL) { 4557 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 4558 if (g1p->track_object_age(alloc_purpose)) { 4559 // We could simply do obj->incr_age(). However, this causes a 4560 // performance issue. obj->incr_age() will first check whether 4561 // the object has a displaced mark by checking its mark word; 4562 // getting the mark word from the new location of the object 4563 // stalls. So, given that we already have the mark word and we 4564 // are about to install it anyway, it's better to increase the 4565 // age on the mark word, when the object does not have a 4566 // displaced mark word. We're not expecting many objects to have 4567 // a displaced marked word, so that case is not optimized 4568 // further (it could be...) and we simply call obj->incr_age(). 4569 4570 if (m->has_displaced_mark_helper()) { 4571 // in this case, we have to install the mark word first, 4572 // otherwise obj looks to be forwarded (the old mark word, 4573 // which contains the forward pointer, was copied) 4574 obj->set_mark(m); 4575 obj->incr_age(); 4576 } else { 4577 m = m->incr_age(); 4578 obj->set_mark(m); 4579 } 4580 _par_scan_state->age_table()->add(obj, word_sz); 4581 } else { 4582 obj->set_mark(m); 4583 } 4584 4585 size_t* surv_young_words = _par_scan_state->surviving_young_words(); 4586 surv_young_words[young_index] += word_sz; 4587 4588 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 4589 // We keep track of the next start index in the length field of 4590 // the to-space object. The actual length can be found in the 4591 // length field of the from-space object. 4592 arrayOop(obj)->set_length(0); 4593 oop* old_p = set_partial_array_mask(old); 4594 _par_scan_state->push_on_queue(old_p); 4595 } else { 4596 // No point in using the slower heap_region_containing() method, 4597 // given that we know obj is in the heap. 4598 _scanner.set_region(_g1->heap_region_containing_raw(obj)); 4599 obj->oop_iterate_backwards(&_scanner); 4600 } 4601 } else { 4602 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4603 obj = forward_ptr; 4604 } 4605 return obj; 4606 } 4607 4608 template <class T> 4609 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4610 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4611 _scanned_klass->record_modified_oops(); 4612 } 4613 } 4614 4615 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4616 template <class T> 4617 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4618 ::do_oop_work(T* p) { 4619 oop obj = oopDesc::load_decode_heap_oop(p); 4620 assert(barrier != G1BarrierRS || obj != NULL, 4621 "Precondition: G1BarrierRS implies obj is non-NULL"); 4622 4623 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4624 4625 // here the null check is implicit in the cset_fast_test() test 4626 if (_g1->in_cset_fast_test(obj)) { 4627 oop forwardee; 4628 if (obj->is_forwarded()) { 4629 forwardee = obj->forwardee(); 4630 } else { 4631 forwardee = copy_to_survivor_space(obj); 4632 } 4633 assert(forwardee != NULL, "forwardee should not be NULL"); 4634 oopDesc::encode_store_heap_oop(p, forwardee); 4635 if (do_mark_object && forwardee != obj) { 4636 // If the object is self-forwarded we don't need to explicitly 4637 // mark it, the evacuation failure protocol will do so. 4638 mark_forwarded_object(obj, forwardee); 4639 } 4640 4641 // When scanning the RS, we only care about objs in CS. 4642 if (barrier == G1BarrierRS) { 4643 _par_scan_state->update_rs(_from, p, _worker_id); 4644 } else if (barrier == G1BarrierKlass) { 4645 do_klass_barrier(p, forwardee); 4646 } 4647 } else { 4648 // The object is not in collection set. If we're a root scanning 4649 // closure during an initial mark pause (i.e. do_mark_object will 4650 // be true) then attempt to mark the object. 4651 if (do_mark_object && _g1->is_in_g1_reserved(obj)) { 4652 mark_object(obj); 4653 } 4654 } 4655 4656 if (barrier == G1BarrierEvac && obj != NULL) { 4657 _par_scan_state->update_rs(_from, p, _worker_id); 4658 } 4659 4660 if (do_gen_barrier && obj != NULL) { 4661 par_do_barrier(p); 4662 } 4663 } 4664 4665 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p); 4666 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p); 4667 4668 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) { 4669 assert(has_partial_array_mask(p), "invariant"); 4670 oop from_obj = clear_partial_array_mask(p); 4671 4672 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap."); 4673 assert(from_obj->is_objArray(), "must be obj array"); 4674 objArrayOop from_obj_array = objArrayOop(from_obj); 4675 // The from-space object contains the real length. 4676 int length = from_obj_array->length(); 4677 4678 assert(from_obj->is_forwarded(), "must be forwarded"); 4679 oop to_obj = from_obj->forwardee(); 4680 assert(from_obj != to_obj, "should not be chunking self-forwarded objects"); 4681 objArrayOop to_obj_array = objArrayOop(to_obj); 4682 // We keep track of the next start index in the length field of the 4683 // to-space object. 4684 int next_index = to_obj_array->length(); 4685 assert(0 <= next_index && next_index < length, 4686 err_msg("invariant, next index: %d, length: %d", next_index, length)); 4687 4688 int start = next_index; 4689 int end = length; 4690 int remainder = end - start; 4691 // We'll try not to push a range that's smaller than ParGCArrayScanChunk. 4692 if (remainder > 2 * ParGCArrayScanChunk) { 4693 end = start + ParGCArrayScanChunk; 4694 to_obj_array->set_length(end); 4695 // Push the remainder before we process the range in case another 4696 // worker has run out of things to do and can steal it. 4697 oop* from_obj_p = set_partial_array_mask(from_obj); 4698 _par_scan_state->push_on_queue(from_obj_p); 4699 } else { 4700 assert(length == end, "sanity"); 4701 // We'll process the final range for this object. Restore the length 4702 // so that the heap remains parsable in case of evacuation failure. 4703 to_obj_array->set_length(end); 4704 } 4705 _scanner.set_region(_g1->heap_region_containing_raw(to_obj)); 4706 // Process indexes [start,end). It will also process the header 4707 // along with the first chunk (i.e., the chunk with start == 0). 4708 // Note that at this point the length field of to_obj_array is not 4709 // correct given that we are using it to keep track of the next 4710 // start index. oop_iterate_range() (thankfully!) ignores the length 4711 // field and only relies on the start / end parameters. It does 4712 // however return the size of the object which will be incorrect. So 4713 // we have to ignore it even if we wanted to use it. 4714 to_obj_array->oop_iterate_range(&_scanner, start, end); 4715 } 4716 4717 class G1ParEvacuateFollowersClosure : public VoidClosure { 4718 protected: 4719 G1CollectedHeap* _g1h; 4720 G1ParScanThreadState* _par_scan_state; 4721 RefToScanQueueSet* _queues; 4722 ParallelTaskTerminator* _terminator; 4723 4724 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4725 RefToScanQueueSet* queues() { return _queues; } 4726 ParallelTaskTerminator* terminator() { return _terminator; } 4727 4728 public: 4729 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4730 G1ParScanThreadState* par_scan_state, 4731 RefToScanQueueSet* queues, 4732 ParallelTaskTerminator* terminator) 4733 : _g1h(g1h), _par_scan_state(par_scan_state), 4734 _queues(queues), _terminator(terminator) {} 4735 4736 void do_void(); 4737 4738 private: 4739 inline bool offer_termination(); 4740 }; 4741 4742 bool G1ParEvacuateFollowersClosure::offer_termination() { 4743 G1ParScanThreadState* const pss = par_scan_state(); 4744 pss->start_term_time(); 4745 const bool res = terminator()->offer_termination(); 4746 pss->end_term_time(); 4747 return res; 4748 } 4749 4750 void G1ParEvacuateFollowersClosure::do_void() { 4751 StarTask stolen_task; 4752 G1ParScanThreadState* const pss = par_scan_state(); 4753 pss->trim_queue(); 4754 4755 do { 4756 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { 4757 assert(pss->verify_task(stolen_task), "sanity"); 4758 if (stolen_task.is_narrow()) { 4759 pss->deal_with_reference((narrowOop*) stolen_task); 4760 } else { 4761 pss->deal_with_reference((oop*) stolen_task); 4762 } 4763 4764 // We've just processed a reference and we might have made 4765 // available new entries on the queues. So we have to make sure 4766 // we drain the queues as necessary. 4767 pss->trim_queue(); 4768 } 4769 } while (!offer_termination()); 4770 4771 pss->retire_alloc_buffers(); 4772 } 4773 4774 class G1KlassScanClosure : public KlassClosure { 4775 G1ParCopyHelper* _closure; 4776 bool _process_only_dirty; 4777 int _count; 4778 public: 4779 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4780 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4781 void do_klass(Klass* klass) { 4782 // If the klass has not been dirtied we know that there's 4783 // no references into the young gen and we can skip it. 4784 if (!_process_only_dirty || klass->has_modified_oops()) { 4785 // Clean the klass since we're going to scavenge all the metadata. 4786 klass->clear_modified_oops(); 4787 4788 // Tell the closure that this klass is the Klass to scavenge 4789 // and is the one to dirty if oops are left pointing into the young gen. 4790 _closure->set_scanned_klass(klass); 4791 4792 klass->oops_do(_closure); 4793 4794 _closure->set_scanned_klass(NULL); 4795 } 4796 _count++; 4797 } 4798 }; 4799 4800 class G1ParTask : public AbstractGangTask { 4801 protected: 4802 G1CollectedHeap* _g1h; 4803 RefToScanQueueSet *_queues; 4804 ParallelTaskTerminator _terminator; 4805 uint _n_workers; 4806 4807 Mutex _stats_lock; 4808 Mutex* stats_lock() { return &_stats_lock; } 4809 4810 size_t getNCards() { 4811 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) 4812 / G1BlockOffsetSharedArray::N_bytes; 4813 } 4814 4815 public: 4816 G1ParTask(G1CollectedHeap* g1h, 4817 RefToScanQueueSet *task_queues) 4818 : AbstractGangTask("G1 collection"), 4819 _g1h(g1h), 4820 _queues(task_queues), 4821 _terminator(0, _queues), 4822 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4823 {} 4824 4825 RefToScanQueueSet* queues() { return _queues; } 4826 4827 RefToScanQueue *work_queue(int i) { 4828 return queues()->queue(i); 4829 } 4830 4831 ParallelTaskTerminator* terminator() { return &_terminator; } 4832 4833 virtual void set_for_termination(int active_workers) { 4834 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4835 // in the young space (_par_seq_tasks) in the G1 heap 4836 // for SequentialSubTasksDone. 4837 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4838 // both of which need setting by set_n_termination(). 4839 _g1h->SharedHeap::set_n_termination(active_workers); 4840 _g1h->set_n_termination(active_workers); 4841 terminator()->reset_for_reuse(active_workers); 4842 _n_workers = active_workers; 4843 } 4844 4845 void work(uint worker_id) { 4846 if (worker_id >= _n_workers) return; // no work needed this round 4847 4848 double start_time_ms = os::elapsedTime() * 1000.0; 4849 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 4850 4851 { 4852 ResourceMark rm; 4853 HandleMark hm; 4854 4855 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4856 4857 G1ParScanThreadState pss(_g1h, worker_id); 4858 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp); 4859 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4860 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp); 4861 4862 pss.set_evac_closure(&scan_evac_cl); 4863 pss.set_evac_failure_closure(&evac_failure_cl); 4864 pss.set_partial_scan_closure(&partial_scan_cl); 4865 4866 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp); 4867 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp); 4868 4869 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp); 4870 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp); 4871 4872 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4873 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false); 4874 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young); 4875 4876 OopClosure* scan_root_cl = &only_scan_root_cl; 4877 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s; 4878 4879 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4880 // We also need to mark copied objects. 4881 scan_root_cl = &scan_mark_root_cl; 4882 scan_klasses_cl = &scan_mark_klasses_cl_s; 4883 } 4884 4885 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4886 4887 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; 4888 4889 pss.start_strong_roots(); 4890 _g1h->g1_process_strong_roots(/* is scavenging */ true, 4891 SharedHeap::ScanningOption(so), 4892 scan_root_cl, 4893 &push_heap_rs_cl, 4894 scan_klasses_cl, 4895 worker_id); 4896 pss.end_strong_roots(); 4897 4898 { 4899 double start = os::elapsedTime(); 4900 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4901 evac.do_void(); 4902 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4903 double term_ms = pss.term_time()*1000.0; 4904 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 4905 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 4906 } 4907 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4908 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4909 4910 if (ParallelGCVerbose) { 4911 MutexLocker x(stats_lock()); 4912 pss.print_termination_stats(worker_id); 4913 } 4914 4915 assert(pss.refs()->is_empty(), "should be empty"); 4916 4917 // Close the inner scope so that the ResourceMark and HandleMark 4918 // destructors are executed here and are included as part of the 4919 // "GC Worker Time". 4920 } 4921 4922 double end_time_ms = os::elapsedTime() * 1000.0; 4923 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 4924 } 4925 }; 4926 4927 // *** Common G1 Evacuation Stuff 4928 4929 // Closures that support the filtering of CodeBlobs scanned during 4930 // external root scanning. 4931 4932 // Closure applied to reference fields in code blobs (specifically nmethods) 4933 // to determine whether an nmethod contains references that point into 4934 // the collection set. Used as a predicate when walking code roots so 4935 // that only nmethods that point into the collection set are added to the 4936 // 'marked' list. 4937 4938 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure { 4939 4940 class G1PointsIntoCSOopClosure : public OopClosure { 4941 G1CollectedHeap* _g1; 4942 bool _points_into_cs; 4943 public: 4944 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) : 4945 _g1(g1), _points_into_cs(false) { } 4946 4947 bool points_into_cs() const { return _points_into_cs; } 4948 4949 template <class T> 4950 void do_oop_nv(T* p) { 4951 if (!_points_into_cs) { 4952 T heap_oop = oopDesc::load_heap_oop(p); 4953 if (!oopDesc::is_null(heap_oop) && 4954 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) { 4955 _points_into_cs = true; 4956 } 4957 } 4958 } 4959 4960 virtual void do_oop(oop* p) { do_oop_nv(p); } 4961 virtual void do_oop(narrowOop* p) { do_oop_nv(p); } 4962 }; 4963 4964 G1CollectedHeap* _g1; 4965 4966 public: 4967 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) : 4968 CodeBlobToOopClosure(cl, true), _g1(g1) { } 4969 4970 virtual void do_code_blob(CodeBlob* cb) { 4971 nmethod* nm = cb->as_nmethod_or_null(); 4972 if (nm != NULL && !(nm->test_oops_do_mark())) { 4973 G1PointsIntoCSOopClosure predicate_cl(_g1); 4974 nm->oops_do(&predicate_cl); 4975 4976 if (predicate_cl.points_into_cs()) { 4977 // At least one of the reference fields or the oop relocations 4978 // in the nmethod points into the collection set. We have to 4979 // 'mark' this nmethod. 4980 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob() 4981 // or MarkingCodeBlobClosure::do_code_blob() change. 4982 if (!nm->test_set_oops_do_mark()) { 4983 do_newly_marked_nmethod(nm); 4984 } 4985 } 4986 } 4987 } 4988 }; 4989 4990 // This method is run in a GC worker. 4991 4992 void 4993 G1CollectedHeap:: 4994 g1_process_strong_roots(bool is_scavenging, 4995 ScanningOption so, 4996 OopClosure* scan_non_heap_roots, 4997 OopsInHeapRegionClosure* scan_rs, 4998 G1KlassScanClosure* scan_klasses, 4999 int worker_i) { 5000 5001 // First scan the strong roots 5002 double ext_roots_start = os::elapsedTime(); 5003 double closure_app_time_sec = 0.0; 5004 5005 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 5006 5007 // Walk the code cache w/o buffering, because StarTask cannot handle 5008 // unaligned oop locations. 5009 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots); 5010 5011 process_strong_roots(false, // no scoping; this is parallel code 5012 is_scavenging, so, 5013 &buf_scan_non_heap_roots, 5014 &eager_scan_code_roots, 5015 scan_klasses 5016 ); 5017 5018 // Now the CM ref_processor roots. 5019 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 5020 // We need to treat the discovered reference lists of the 5021 // concurrent mark ref processor as roots and keep entries 5022 // (which are added by the marking threads) on them live 5023 // until they can be processed at the end of marking. 5024 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 5025 } 5026 5027 // Finish up any enqueued closure apps (attributed as object copy time). 5028 buf_scan_non_heap_roots.done(); 5029 5030 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds(); 5031 5032 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 5033 5034 double ext_root_time_ms = 5035 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 5036 5037 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 5038 5039 // During conc marking we have to filter the per-thread SATB buffers 5040 // to make sure we remove any oops into the CSet (which will show up 5041 // as implicitly live). 5042 double satb_filtering_ms = 0.0; 5043 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 5044 if (mark_in_progress()) { 5045 double satb_filter_start = os::elapsedTime(); 5046 5047 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 5048 5049 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 5050 } 5051 } 5052 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 5053 5054 // Now scan the complement of the collection set. 5055 if (scan_rs != NULL) { 5056 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i); 5057 } 5058 _process_strong_tasks->all_tasks_completed(); 5059 } 5060 5061 void 5062 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure, 5063 OopClosure* non_root_closure) { 5064 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); 5065 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure); 5066 } 5067 5068 // Weak Reference Processing support 5069 5070 // An always "is_alive" closure that is used to preserve referents. 5071 // If the object is non-null then it's alive. Used in the preservation 5072 // of referent objects that are pointed to by reference objects 5073 // discovered by the CM ref processor. 5074 class G1AlwaysAliveClosure: public BoolObjectClosure { 5075 G1CollectedHeap* _g1; 5076 public: 5077 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5078 void do_object(oop p) { assert(false, "Do not call."); } 5079 bool do_object_b(oop p) { 5080 if (p != NULL) { 5081 return true; 5082 } 5083 return false; 5084 } 5085 }; 5086 5087 bool G1STWIsAliveClosure::do_object_b(oop p) { 5088 // An object is reachable if it is outside the collection set, 5089 // or is inside and copied. 5090 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5091 } 5092 5093 // Non Copying Keep Alive closure 5094 class G1KeepAliveClosure: public OopClosure { 5095 G1CollectedHeap* _g1; 5096 public: 5097 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5098 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5099 void do_oop( oop* p) { 5100 oop obj = *p; 5101 5102 if (_g1->obj_in_cs(obj)) { 5103 assert( obj->is_forwarded(), "invariant" ); 5104 *p = obj->forwardee(); 5105 } 5106 } 5107 }; 5108 5109 // Copying Keep Alive closure - can be called from both 5110 // serial and parallel code as long as different worker 5111 // threads utilize different G1ParScanThreadState instances 5112 // and different queues. 5113 5114 class G1CopyingKeepAliveClosure: public OopClosure { 5115 G1CollectedHeap* _g1h; 5116 OopClosure* _copy_non_heap_obj_cl; 5117 OopsInHeapRegionClosure* _copy_metadata_obj_cl; 5118 G1ParScanThreadState* _par_scan_state; 5119 5120 public: 5121 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5122 OopClosure* non_heap_obj_cl, 5123 OopsInHeapRegionClosure* metadata_obj_cl, 5124 G1ParScanThreadState* pss): 5125 _g1h(g1h), 5126 _copy_non_heap_obj_cl(non_heap_obj_cl), 5127 _copy_metadata_obj_cl(metadata_obj_cl), 5128 _par_scan_state(pss) 5129 {} 5130 5131 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5132 virtual void do_oop( oop* p) { do_oop_work(p); } 5133 5134 template <class T> void do_oop_work(T* p) { 5135 oop obj = oopDesc::load_decode_heap_oop(p); 5136 5137 if (_g1h->obj_in_cs(obj)) { 5138 // If the referent object has been forwarded (either copied 5139 // to a new location or to itself in the event of an 5140 // evacuation failure) then we need to update the reference 5141 // field and, if both reference and referent are in the G1 5142 // heap, update the RSet for the referent. 5143 // 5144 // If the referent has not been forwarded then we have to keep 5145 // it alive by policy. Therefore we have copy the referent. 5146 // 5147 // If the reference field is in the G1 heap then we can push 5148 // on the PSS queue. When the queue is drained (after each 5149 // phase of reference processing) the object and it's followers 5150 // will be copied, the reference field set to point to the 5151 // new location, and the RSet updated. Otherwise we need to 5152 // use the the non-heap or metadata closures directly to copy 5153 // the refernt object and update the pointer, while avoiding 5154 // updating the RSet. 5155 5156 if (_g1h->is_in_g1_reserved(p)) { 5157 _par_scan_state->push_on_queue(p); 5158 } else { 5159 assert(!ClassLoaderDataGraph::contains((address)p), 5160 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) " 5161 PTR_FORMAT, p)); 5162 _copy_non_heap_obj_cl->do_oop(p); 5163 } 5164 } 5165 } 5166 }; 5167 5168 // Serial drain queue closure. Called as the 'complete_gc' 5169 // closure for each discovered list in some of the 5170 // reference processing phases. 5171 5172 class G1STWDrainQueueClosure: public VoidClosure { 5173 protected: 5174 G1CollectedHeap* _g1h; 5175 G1ParScanThreadState* _par_scan_state; 5176 5177 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5178 5179 public: 5180 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5181 _g1h(g1h), 5182 _par_scan_state(pss) 5183 { } 5184 5185 void do_void() { 5186 G1ParScanThreadState* const pss = par_scan_state(); 5187 pss->trim_queue(); 5188 } 5189 }; 5190 5191 // Parallel Reference Processing closures 5192 5193 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5194 // processing during G1 evacuation pauses. 5195 5196 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5197 private: 5198 G1CollectedHeap* _g1h; 5199 RefToScanQueueSet* _queues; 5200 FlexibleWorkGang* _workers; 5201 int _active_workers; 5202 5203 public: 5204 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5205 FlexibleWorkGang* workers, 5206 RefToScanQueueSet *task_queues, 5207 int n_workers) : 5208 _g1h(g1h), 5209 _queues(task_queues), 5210 _workers(workers), 5211 _active_workers(n_workers) 5212 { 5213 assert(n_workers > 0, "shouldn't call this otherwise"); 5214 } 5215 5216 // Executes the given task using concurrent marking worker threads. 5217 virtual void execute(ProcessTask& task); 5218 virtual void execute(EnqueueTask& task); 5219 }; 5220 5221 // Gang task for possibly parallel reference processing 5222 5223 class G1STWRefProcTaskProxy: public AbstractGangTask { 5224 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5225 ProcessTask& _proc_task; 5226 G1CollectedHeap* _g1h; 5227 RefToScanQueueSet *_task_queues; 5228 ParallelTaskTerminator* _terminator; 5229 5230 public: 5231 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5232 G1CollectedHeap* g1h, 5233 RefToScanQueueSet *task_queues, 5234 ParallelTaskTerminator* terminator) : 5235 AbstractGangTask("Process reference objects in parallel"), 5236 _proc_task(proc_task), 5237 _g1h(g1h), 5238 _task_queues(task_queues), 5239 _terminator(terminator) 5240 {} 5241 5242 virtual void work(uint worker_id) { 5243 // The reference processing task executed by a single worker. 5244 ResourceMark rm; 5245 HandleMark hm; 5246 5247 G1STWIsAliveClosure is_alive(_g1h); 5248 5249 G1ParScanThreadState pss(_g1h, worker_id); 5250 5251 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5252 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5253 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5254 5255 pss.set_evac_closure(&scan_evac_cl); 5256 pss.set_evac_failure_closure(&evac_failure_cl); 5257 pss.set_partial_scan_closure(&partial_scan_cl); 5258 5259 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5260 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5261 5262 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5263 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5264 5265 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5266 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5267 5268 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5269 // We also need to mark copied objects. 5270 copy_non_heap_cl = ©_mark_non_heap_cl; 5271 copy_metadata_cl = ©_mark_metadata_cl; 5272 } 5273 5274 // Keep alive closure. 5275 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5276 5277 // Complete GC closure 5278 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5279 5280 // Call the reference processing task's work routine. 5281 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5282 5283 // Note we cannot assert that the refs array is empty here as not all 5284 // of the processing tasks (specifically phase2 - pp2_work) execute 5285 // the complete_gc closure (which ordinarily would drain the queue) so 5286 // the queue may not be empty. 5287 } 5288 }; 5289 5290 // Driver routine for parallel reference processing. 5291 // Creates an instance of the ref processing gang 5292 // task and has the worker threads execute it. 5293 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5294 assert(_workers != NULL, "Need parallel worker threads."); 5295 5296 ParallelTaskTerminator terminator(_active_workers, _queues); 5297 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5298 5299 _g1h->set_par_threads(_active_workers); 5300 _workers->run_task(&proc_task_proxy); 5301 _g1h->set_par_threads(0); 5302 } 5303 5304 // Gang task for parallel reference enqueueing. 5305 5306 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5307 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5308 EnqueueTask& _enq_task; 5309 5310 public: 5311 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5312 AbstractGangTask("Enqueue reference objects in parallel"), 5313 _enq_task(enq_task) 5314 { } 5315 5316 virtual void work(uint worker_id) { 5317 _enq_task.work(worker_id); 5318 } 5319 }; 5320 5321 // Driver routine for parallel reference enqueing. 5322 // Creates an instance of the ref enqueueing gang 5323 // task and has the worker threads execute it. 5324 5325 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5326 assert(_workers != NULL, "Need parallel worker threads."); 5327 5328 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5329 5330 _g1h->set_par_threads(_active_workers); 5331 _workers->run_task(&enq_task_proxy); 5332 _g1h->set_par_threads(0); 5333 } 5334 5335 // End of weak reference support closures 5336 5337 // Abstract task used to preserve (i.e. copy) any referent objects 5338 // that are in the collection set and are pointed to by reference 5339 // objects discovered by the CM ref processor. 5340 5341 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5342 protected: 5343 G1CollectedHeap* _g1h; 5344 RefToScanQueueSet *_queues; 5345 ParallelTaskTerminator _terminator; 5346 uint _n_workers; 5347 5348 public: 5349 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5350 AbstractGangTask("ParPreserveCMReferents"), 5351 _g1h(g1h), 5352 _queues(task_queues), 5353 _terminator(workers, _queues), 5354 _n_workers(workers) 5355 { } 5356 5357 void work(uint worker_id) { 5358 ResourceMark rm; 5359 HandleMark hm; 5360 5361 G1ParScanThreadState pss(_g1h, worker_id); 5362 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5363 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5364 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5365 5366 pss.set_evac_closure(&scan_evac_cl); 5367 pss.set_evac_failure_closure(&evac_failure_cl); 5368 pss.set_partial_scan_closure(&partial_scan_cl); 5369 5370 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5371 5372 5373 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5374 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5375 5376 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5377 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5378 5379 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5380 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5381 5382 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5383 // We also need to mark copied objects. 5384 copy_non_heap_cl = ©_mark_non_heap_cl; 5385 copy_metadata_cl = ©_mark_metadata_cl; 5386 } 5387 5388 // Is alive closure 5389 G1AlwaysAliveClosure always_alive(_g1h); 5390 5391 // Copying keep alive closure. Applied to referent objects that need 5392 // to be copied. 5393 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5394 5395 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5396 5397 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5398 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5399 5400 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5401 // So this must be true - but assert just in case someone decides to 5402 // change the worker ids. 5403 assert(0 <= worker_id && worker_id < limit, "sanity"); 5404 assert(!rp->discovery_is_atomic(), "check this code"); 5405 5406 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5407 for (uint idx = worker_id; idx < limit; idx += stride) { 5408 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5409 5410 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5411 while (iter.has_next()) { 5412 // Since discovery is not atomic for the CM ref processor, we 5413 // can see some null referent objects. 5414 iter.load_ptrs(DEBUG_ONLY(true)); 5415 oop ref = iter.obj(); 5416 5417 // This will filter nulls. 5418 if (iter.is_referent_alive()) { 5419 iter.make_referent_alive(); 5420 } 5421 iter.move_to_next(); 5422 } 5423 } 5424 5425 // Drain the queue - which may cause stealing 5426 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5427 drain_queue.do_void(); 5428 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5429 assert(pss.refs()->is_empty(), "should be"); 5430 } 5431 }; 5432 5433 // Weak Reference processing during an evacuation pause (part 1). 5434 void G1CollectedHeap::process_discovered_references() { 5435 double ref_proc_start = os::elapsedTime(); 5436 5437 ReferenceProcessor* rp = _ref_processor_stw; 5438 assert(rp->discovery_enabled(), "should have been enabled"); 5439 5440 // Any reference objects, in the collection set, that were 'discovered' 5441 // by the CM ref processor should have already been copied (either by 5442 // applying the external root copy closure to the discovered lists, or 5443 // by following an RSet entry). 5444 // 5445 // But some of the referents, that are in the collection set, that these 5446 // reference objects point to may not have been copied: the STW ref 5447 // processor would have seen that the reference object had already 5448 // been 'discovered' and would have skipped discovering the reference, 5449 // but would not have treated the reference object as a regular oop. 5450 // As a reult the copy closure would not have been applied to the 5451 // referent object. 5452 // 5453 // We need to explicitly copy these referent objects - the references 5454 // will be processed at the end of remarking. 5455 // 5456 // We also need to do this copying before we process the reference 5457 // objects discovered by the STW ref processor in case one of these 5458 // referents points to another object which is also referenced by an 5459 // object discovered by the STW ref processor. 5460 5461 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5462 workers()->active_workers() : 1); 5463 5464 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5465 active_workers == workers()->active_workers(), 5466 "Need to reset active_workers"); 5467 5468 set_par_threads(active_workers); 5469 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues); 5470 5471 if (G1CollectedHeap::use_parallel_gc_threads()) { 5472 workers()->run_task(&keep_cm_referents); 5473 } else { 5474 keep_cm_referents.work(0); 5475 } 5476 5477 set_par_threads(0); 5478 5479 // Closure to test whether a referent is alive. 5480 G1STWIsAliveClosure is_alive(this); 5481 5482 // Even when parallel reference processing is enabled, the processing 5483 // of JNI refs is serial and performed serially by the current thread 5484 // rather than by a worker. The following PSS will be used for processing 5485 // JNI refs. 5486 5487 // Use only a single queue for this PSS. 5488 G1ParScanThreadState pss(this, 0); 5489 5490 // We do not embed a reference processor in the copying/scanning 5491 // closures while we're actually processing the discovered 5492 // reference objects. 5493 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL); 5494 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5495 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL); 5496 5497 pss.set_evac_closure(&scan_evac_cl); 5498 pss.set_evac_failure_closure(&evac_failure_cl); 5499 pss.set_partial_scan_closure(&partial_scan_cl); 5500 5501 assert(pss.refs()->is_empty(), "pre-condition"); 5502 5503 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5504 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL); 5505 5506 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5507 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL); 5508 5509 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5510 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5511 5512 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5513 // We also need to mark copied objects. 5514 copy_non_heap_cl = ©_mark_non_heap_cl; 5515 copy_metadata_cl = ©_mark_metadata_cl; 5516 } 5517 5518 // Keep alive closure. 5519 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss); 5520 5521 // Serial Complete GC closure 5522 G1STWDrainQueueClosure drain_queue(this, &pss); 5523 5524 // Setup the soft refs policy... 5525 rp->setup_policy(false); 5526 5527 if (!rp->processing_is_mt()) { 5528 // Serial reference processing... 5529 rp->process_discovered_references(&is_alive, 5530 &keep_alive, 5531 &drain_queue, 5532 NULL); 5533 } else { 5534 // Parallel reference processing 5535 assert(rp->num_q() == active_workers, "sanity"); 5536 assert(active_workers <= rp->max_num_q(), "sanity"); 5537 5538 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers); 5539 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor); 5540 } 5541 5542 // We have completed copying any necessary live referent objects 5543 // (that were not copied during the actual pause) so we can 5544 // retire any active alloc buffers 5545 pss.retire_alloc_buffers(); 5546 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5547 5548 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5549 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5550 } 5551 5552 // Weak Reference processing during an evacuation pause (part 2). 5553 void G1CollectedHeap::enqueue_discovered_references() { 5554 double ref_enq_start = os::elapsedTime(); 5555 5556 ReferenceProcessor* rp = _ref_processor_stw; 5557 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5558 5559 // Now enqueue any remaining on the discovered lists on to 5560 // the pending list. 5561 if (!rp->processing_is_mt()) { 5562 // Serial reference processing... 5563 rp->enqueue_discovered_references(); 5564 } else { 5565 // Parallel reference enqueuing 5566 5567 uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1); 5568 assert(active_workers == workers()->active_workers(), 5569 "Need to reset active_workers"); 5570 assert(rp->num_q() == active_workers, "sanity"); 5571 assert(active_workers <= rp->max_num_q(), "sanity"); 5572 5573 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers); 5574 rp->enqueue_discovered_references(&par_task_executor); 5575 } 5576 5577 rp->verify_no_references_recorded(); 5578 assert(!rp->discovery_enabled(), "should have been disabled"); 5579 5580 // FIXME 5581 // CM's reference processing also cleans up the string and symbol tables. 5582 // Should we do that here also? We could, but it is a serial operation 5583 // and could signicantly increase the pause time. 5584 5585 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5586 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5587 } 5588 5589 void G1CollectedHeap::evacuate_collection_set() { 5590 _expand_heap_after_alloc_failure = true; 5591 set_evacuation_failed(false); 5592 5593 // Should G1EvacuationFailureALot be in effect for this GC? 5594 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5595 5596 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5597 concurrent_g1_refine()->set_use_cache(false); 5598 concurrent_g1_refine()->clear_hot_cache_claimed_index(); 5599 5600 uint n_workers; 5601 if (G1CollectedHeap::use_parallel_gc_threads()) { 5602 n_workers = 5603 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5604 workers()->active_workers(), 5605 Threads::number_of_non_daemon_threads()); 5606 assert(UseDynamicNumberOfGCThreads || 5607 n_workers == workers()->total_workers(), 5608 "If not dynamic should be using all the workers"); 5609 workers()->set_active_workers(n_workers); 5610 set_par_threads(n_workers); 5611 } else { 5612 assert(n_par_threads() == 0, 5613 "Should be the original non-parallel value"); 5614 n_workers = 1; 5615 } 5616 5617 G1ParTask g1_par_task(this, _task_queues); 5618 5619 init_for_evac_failure(NULL); 5620 5621 rem_set()->prepare_for_younger_refs_iterate(true); 5622 5623 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5624 double start_par_time_sec = os::elapsedTime(); 5625 double end_par_time_sec; 5626 5627 { 5628 StrongRootsScope srs(this); 5629 5630 if (G1CollectedHeap::use_parallel_gc_threads()) { 5631 // The individual threads will set their evac-failure closures. 5632 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5633 // These tasks use ShareHeap::_process_strong_tasks 5634 assert(UseDynamicNumberOfGCThreads || 5635 workers()->active_workers() == workers()->total_workers(), 5636 "If not dynamic should be using all the workers"); 5637 workers()->run_task(&g1_par_task); 5638 } else { 5639 g1_par_task.set_for_termination(n_workers); 5640 g1_par_task.work(0); 5641 } 5642 end_par_time_sec = os::elapsedTime(); 5643 5644 // Closing the inner scope will execute the destructor 5645 // for the StrongRootsScope object. We record the current 5646 // elapsed time before closing the scope so that time 5647 // taken for the SRS destructor is NOT included in the 5648 // reported parallel time. 5649 } 5650 5651 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5652 g1_policy()->phase_times()->record_par_time(par_time_ms); 5653 5654 double code_root_fixup_time_ms = 5655 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5656 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5657 5658 set_par_threads(0); 5659 5660 // Process any discovered reference objects - we have 5661 // to do this _before_ we retire the GC alloc regions 5662 // as we may have to copy some 'reachable' referent 5663 // objects (and their reachable sub-graphs) that were 5664 // not copied during the pause. 5665 process_discovered_references(); 5666 5667 // Weak root processing. 5668 // Note: when JSR 292 is enabled and code blobs can contain 5669 // non-perm oops then we will need to process the code blobs 5670 // here too. 5671 { 5672 G1STWIsAliveClosure is_alive(this); 5673 G1KeepAliveClosure keep_alive(this); 5674 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5675 } 5676 5677 release_gc_alloc_regions(); 5678 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5679 5680 concurrent_g1_refine()->clear_hot_cache(); 5681 concurrent_g1_refine()->set_use_cache(true); 5682 5683 finalize_for_evac_failure(); 5684 5685 if (evacuation_failed()) { 5686 remove_self_forwarding_pointers(); 5687 5688 // Reset the G1EvacuationFailureALot counters and flags 5689 // Note: the values are reset only when an actual 5690 // evacuation failure occurs. 5691 NOT_PRODUCT(reset_evacuation_should_fail();) 5692 } 5693 5694 // Enqueue any remaining references remaining on the STW 5695 // reference processor's discovered lists. We need to do 5696 // this after the card table is cleaned (and verified) as 5697 // the act of enqueuing entries on to the pending list 5698 // will log these updates (and dirty their associated 5699 // cards). We need these updates logged to update any 5700 // RSets. 5701 enqueue_discovered_references(); 5702 5703 if (G1DeferredRSUpdate) { 5704 RedirtyLoggedCardTableEntryFastClosure redirty; 5705 dirty_card_queue_set().set_closure(&redirty); 5706 dirty_card_queue_set().apply_closure_to_all_completed_buffers(); 5707 5708 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5709 dcq.merge_bufferlists(&dirty_card_queue_set()); 5710 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5711 } 5712 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5713 } 5714 5715 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr, 5716 size_t* pre_used, 5717 FreeRegionList* free_list, 5718 OldRegionSet* old_proxy_set, 5719 HumongousRegionSet* humongous_proxy_set, 5720 HRRSCleanupTask* hrrs_cleanup_task, 5721 bool par) { 5722 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 5723 if (hr->isHumongous()) { 5724 assert(hr->startsHumongous(), "we should only see starts humongous"); 5725 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par); 5726 } else { 5727 _old_set.remove_with_proxy(hr, old_proxy_set); 5728 free_region(hr, pre_used, free_list, par); 5729 } 5730 } else { 5731 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task); 5732 } 5733 } 5734 5735 void G1CollectedHeap::free_region(HeapRegion* hr, 5736 size_t* pre_used, 5737 FreeRegionList* free_list, 5738 bool par) { 5739 assert(!hr->isHumongous(), "this is only for non-humongous regions"); 5740 assert(!hr->is_empty(), "the region should not be empty"); 5741 assert(free_list != NULL, "pre-condition"); 5742 5743 *pre_used += hr->used(); 5744 hr->hr_clear(par, true /* clear_space */); 5745 free_list->add_as_head(hr); 5746 } 5747 5748 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5749 size_t* pre_used, 5750 FreeRegionList* free_list, 5751 HumongousRegionSet* humongous_proxy_set, 5752 bool par) { 5753 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 5754 assert(free_list != NULL, "pre-condition"); 5755 assert(humongous_proxy_set != NULL, "pre-condition"); 5756 5757 size_t hr_used = hr->used(); 5758 size_t hr_capacity = hr->capacity(); 5759 size_t hr_pre_used = 0; 5760 _humongous_set.remove_with_proxy(hr, humongous_proxy_set); 5761 // We need to read this before we make the region non-humongous, 5762 // otherwise the information will be gone. 5763 uint last_index = hr->last_hc_index(); 5764 hr->set_notHumongous(); 5765 free_region(hr, &hr_pre_used, free_list, par); 5766 5767 uint i = hr->hrs_index() + 1; 5768 while (i < last_index) { 5769 HeapRegion* curr_hr = region_at(i); 5770 assert(curr_hr->continuesHumongous(), "invariant"); 5771 curr_hr->set_notHumongous(); 5772 free_region(curr_hr, &hr_pre_used, free_list, par); 5773 i += 1; 5774 } 5775 assert(hr_pre_used == hr_used, 5776 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" " 5777 "should be the same", hr_pre_used, hr_used)); 5778 *pre_used += hr_pre_used; 5779 } 5780 5781 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used, 5782 FreeRegionList* free_list, 5783 OldRegionSet* old_proxy_set, 5784 HumongousRegionSet* humongous_proxy_set, 5785 bool par) { 5786 if (pre_used > 0) { 5787 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL; 5788 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); 5789 assert(_summary_bytes_used >= pre_used, 5790 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" " 5791 "should be >= pre_used: "SIZE_FORMAT, 5792 _summary_bytes_used, pre_used)); 5793 _summary_bytes_used -= pre_used; 5794 } 5795 if (free_list != NULL && !free_list->is_empty()) { 5796 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5797 _free_list.add_as_head(free_list); 5798 } 5799 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) { 5800 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5801 _old_set.update_from_proxy(old_proxy_set); 5802 } 5803 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) { 5804 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5805 _humongous_set.update_from_proxy(humongous_proxy_set); 5806 } 5807 } 5808 5809 class G1ParCleanupCTTask : public AbstractGangTask { 5810 CardTableModRefBS* _ct_bs; 5811 G1CollectedHeap* _g1h; 5812 HeapRegion* volatile _su_head; 5813 public: 5814 G1ParCleanupCTTask(CardTableModRefBS* ct_bs, 5815 G1CollectedHeap* g1h) : 5816 AbstractGangTask("G1 Par Cleanup CT Task"), 5817 _ct_bs(ct_bs), _g1h(g1h) { } 5818 5819 void work(uint worker_id) { 5820 HeapRegion* r; 5821 while (r = _g1h->pop_dirty_cards_region()) { 5822 clear_cards(r); 5823 } 5824 } 5825 5826 void clear_cards(HeapRegion* r) { 5827 // Cards of the survivors should have already been dirtied. 5828 if (!r->is_survivor()) { 5829 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5830 } 5831 } 5832 }; 5833 5834 #ifndef PRODUCT 5835 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5836 G1CollectedHeap* _g1h; 5837 CardTableModRefBS* _ct_bs; 5838 public: 5839 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs) 5840 : _g1h(g1h), _ct_bs(ct_bs) { } 5841 virtual bool doHeapRegion(HeapRegion* r) { 5842 if (r->is_survivor()) { 5843 _g1h->verify_dirty_region(r); 5844 } else { 5845 _g1h->verify_not_dirty_region(r); 5846 } 5847 return false; 5848 } 5849 }; 5850 5851 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5852 // All of the region should be clean. 5853 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 5854 MemRegion mr(hr->bottom(), hr->end()); 5855 ct_bs->verify_not_dirty_region(mr); 5856 } 5857 5858 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5859 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5860 // dirty allocated blocks as they allocate them. The thread that 5861 // retires each region and replaces it with a new one will do a 5862 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5863 // not dirty that area (one less thing to have to do while holding 5864 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5865 // is dirty. 5866 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5867 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5868 ct_bs->verify_dirty_region(mr); 5869 } 5870 5871 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5872 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5873 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5874 verify_dirty_region(hr); 5875 } 5876 } 5877 5878 void G1CollectedHeap::verify_dirty_young_regions() { 5879 verify_dirty_young_list(_young_list->first_region()); 5880 } 5881 #endif 5882 5883 void G1CollectedHeap::cleanUpCardTable() { 5884 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set()); 5885 double start = os::elapsedTime(); 5886 5887 { 5888 // Iterate over the dirty cards region list. 5889 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5890 5891 if (G1CollectedHeap::use_parallel_gc_threads()) { 5892 set_par_threads(); 5893 workers()->run_task(&cleanup_task); 5894 set_par_threads(0); 5895 } else { 5896 while (_dirty_cards_region_list) { 5897 HeapRegion* r = _dirty_cards_region_list; 5898 cleanup_task.clear_cards(r); 5899 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 5900 if (_dirty_cards_region_list == r) { 5901 // The last region. 5902 _dirty_cards_region_list = NULL; 5903 } 5904 r->set_next_dirty_cards_region(NULL); 5905 } 5906 } 5907 #ifndef PRODUCT 5908 if (G1VerifyCTCleanup || VerifyAfterGC) { 5909 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5910 heap_region_iterate(&cleanup_verifier); 5911 } 5912 #endif 5913 } 5914 5915 double elapsed = os::elapsedTime() - start; 5916 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5917 } 5918 5919 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) { 5920 size_t pre_used = 0; 5921 FreeRegionList local_free_list("Local List for CSet Freeing"); 5922 5923 double young_time_ms = 0.0; 5924 double non_young_time_ms = 0.0; 5925 5926 // Since the collection set is a superset of the the young list, 5927 // all we need to do to clear the young list is clear its 5928 // head and length, and unlink any young regions in the code below 5929 _young_list->clear(); 5930 5931 G1CollectorPolicy* policy = g1_policy(); 5932 5933 double start_sec = os::elapsedTime(); 5934 bool non_young = true; 5935 5936 HeapRegion* cur = cs_head; 5937 int age_bound = -1; 5938 size_t rs_lengths = 0; 5939 5940 while (cur != NULL) { 5941 assert(!is_on_master_free_list(cur), "sanity"); 5942 if (non_young) { 5943 if (cur->is_young()) { 5944 double end_sec = os::elapsedTime(); 5945 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5946 non_young_time_ms += elapsed_ms; 5947 5948 start_sec = os::elapsedTime(); 5949 non_young = false; 5950 } 5951 } else { 5952 if (!cur->is_young()) { 5953 double end_sec = os::elapsedTime(); 5954 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5955 young_time_ms += elapsed_ms; 5956 5957 start_sec = os::elapsedTime(); 5958 non_young = true; 5959 } 5960 } 5961 5962 rs_lengths += cur->rem_set()->occupied(); 5963 5964 HeapRegion* next = cur->next_in_collection_set(); 5965 assert(cur->in_collection_set(), "bad CS"); 5966 cur->set_next_in_collection_set(NULL); 5967 cur->set_in_collection_set(false); 5968 5969 if (cur->is_young()) { 5970 int index = cur->young_index_in_cset(); 5971 assert(index != -1, "invariant"); 5972 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5973 size_t words_survived = _surviving_young_words[index]; 5974 cur->record_surv_words_in_group(words_survived); 5975 5976 // At this point the we have 'popped' cur from the collection set 5977 // (linked via next_in_collection_set()) but it is still in the 5978 // young list (linked via next_young_region()). Clear the 5979 // _next_young_region field. 5980 cur->set_next_young_region(NULL); 5981 } else { 5982 int index = cur->young_index_in_cset(); 5983 assert(index == -1, "invariant"); 5984 } 5985 5986 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5987 (!cur->is_young() && cur->young_index_in_cset() == -1), 5988 "invariant" ); 5989 5990 if (!cur->evacuation_failed()) { 5991 MemRegion used_mr = cur->used_region(); 5992 5993 // And the region is empty. 5994 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 5995 free_region(cur, &pre_used, &local_free_list, false /* par */); 5996 } else { 5997 cur->uninstall_surv_rate_group(); 5998 if (cur->is_young()) { 5999 cur->set_young_index_in_cset(-1); 6000 } 6001 cur->set_not_young(); 6002 cur->set_evacuation_failed(false); 6003 // The region is now considered to be old. 6004 _old_set.add(cur); 6005 } 6006 cur = next; 6007 } 6008 6009 policy->record_max_rs_lengths(rs_lengths); 6010 policy->cset_regions_freed(); 6011 6012 double end_sec = os::elapsedTime(); 6013 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6014 6015 if (non_young) { 6016 non_young_time_ms += elapsed_ms; 6017 } else { 6018 young_time_ms += elapsed_ms; 6019 } 6020 6021 update_sets_after_freeing_regions(pre_used, &local_free_list, 6022 NULL /* old_proxy_set */, 6023 NULL /* humongous_proxy_set */, 6024 false /* par */); 6025 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6026 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6027 } 6028 6029 // This routine is similar to the above but does not record 6030 // any policy statistics or update free lists; we are abandoning 6031 // the current incremental collection set in preparation of a 6032 // full collection. After the full GC we will start to build up 6033 // the incremental collection set again. 6034 // This is only called when we're doing a full collection 6035 // and is immediately followed by the tearing down of the young list. 6036 6037 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6038 HeapRegion* cur = cs_head; 6039 6040 while (cur != NULL) { 6041 HeapRegion* next = cur->next_in_collection_set(); 6042 assert(cur->in_collection_set(), "bad CS"); 6043 cur->set_next_in_collection_set(NULL); 6044 cur->set_in_collection_set(false); 6045 cur->set_young_index_in_cset(-1); 6046 cur = next; 6047 } 6048 } 6049 6050 void G1CollectedHeap::set_free_regions_coming() { 6051 if (G1ConcRegionFreeingVerbose) { 6052 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6053 "setting free regions coming"); 6054 } 6055 6056 assert(!free_regions_coming(), "pre-condition"); 6057 _free_regions_coming = true; 6058 } 6059 6060 void G1CollectedHeap::reset_free_regions_coming() { 6061 assert(free_regions_coming(), "pre-condition"); 6062 6063 { 6064 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6065 _free_regions_coming = false; 6066 SecondaryFreeList_lock->notify_all(); 6067 } 6068 6069 if (G1ConcRegionFreeingVerbose) { 6070 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6071 "reset free regions coming"); 6072 } 6073 } 6074 6075 void G1CollectedHeap::wait_while_free_regions_coming() { 6076 // Most of the time we won't have to wait, so let's do a quick test 6077 // first before we take the lock. 6078 if (!free_regions_coming()) { 6079 return; 6080 } 6081 6082 if (G1ConcRegionFreeingVerbose) { 6083 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6084 "waiting for free regions"); 6085 } 6086 6087 { 6088 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6089 while (free_regions_coming()) { 6090 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6091 } 6092 } 6093 6094 if (G1ConcRegionFreeingVerbose) { 6095 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6096 "done waiting for free regions"); 6097 } 6098 } 6099 6100 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6101 assert(heap_lock_held_for_gc(), 6102 "the heap lock should already be held by or for this thread"); 6103 _young_list->push_region(hr); 6104 } 6105 6106 class NoYoungRegionsClosure: public HeapRegionClosure { 6107 private: 6108 bool _success; 6109 public: 6110 NoYoungRegionsClosure() : _success(true) { } 6111 bool doHeapRegion(HeapRegion* r) { 6112 if (r->is_young()) { 6113 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6114 r->bottom(), r->end()); 6115 _success = false; 6116 } 6117 return false; 6118 } 6119 bool success() { return _success; } 6120 }; 6121 6122 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6123 bool ret = _young_list->check_list_empty(check_sample); 6124 6125 if (check_heap) { 6126 NoYoungRegionsClosure closure; 6127 heap_region_iterate(&closure); 6128 ret = ret && closure.success(); 6129 } 6130 6131 return ret; 6132 } 6133 6134 class TearDownRegionSetsClosure : public HeapRegionClosure { 6135 private: 6136 OldRegionSet *_old_set; 6137 6138 public: 6139 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { } 6140 6141 bool doHeapRegion(HeapRegion* r) { 6142 if (r->is_empty()) { 6143 // We ignore empty regions, we'll empty the free list afterwards 6144 } else if (r->is_young()) { 6145 // We ignore young regions, we'll empty the young list afterwards 6146 } else if (r->isHumongous()) { 6147 // We ignore humongous regions, we're not tearing down the 6148 // humongous region set 6149 } else { 6150 // The rest should be old 6151 _old_set->remove(r); 6152 } 6153 return false; 6154 } 6155 6156 ~TearDownRegionSetsClosure() { 6157 assert(_old_set->is_empty(), "post-condition"); 6158 } 6159 }; 6160 6161 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6162 assert_at_safepoint(true /* should_be_vm_thread */); 6163 6164 if (!free_list_only) { 6165 TearDownRegionSetsClosure cl(&_old_set); 6166 heap_region_iterate(&cl); 6167 6168 // Need to do this after the heap iteration to be able to 6169 // recognize the young regions and ignore them during the iteration. 6170 _young_list->empty_list(); 6171 } 6172 _free_list.remove_all(); 6173 } 6174 6175 class RebuildRegionSetsClosure : public HeapRegionClosure { 6176 private: 6177 bool _free_list_only; 6178 OldRegionSet* _old_set; 6179 FreeRegionList* _free_list; 6180 size_t _total_used; 6181 6182 public: 6183 RebuildRegionSetsClosure(bool free_list_only, 6184 OldRegionSet* old_set, FreeRegionList* free_list) : 6185 _free_list_only(free_list_only), 6186 _old_set(old_set), _free_list(free_list), _total_used(0) { 6187 assert(_free_list->is_empty(), "pre-condition"); 6188 if (!free_list_only) { 6189 assert(_old_set->is_empty(), "pre-condition"); 6190 } 6191 } 6192 6193 bool doHeapRegion(HeapRegion* r) { 6194 if (r->continuesHumongous()) { 6195 return false; 6196 } 6197 6198 if (r->is_empty()) { 6199 // Add free regions to the free list 6200 _free_list->add_as_tail(r); 6201 } else if (!_free_list_only) { 6202 assert(!r->is_young(), "we should not come across young regions"); 6203 6204 if (r->isHumongous()) { 6205 // We ignore humongous regions, we left the humongous set unchanged 6206 } else { 6207 // The rest should be old, add them to the old set 6208 _old_set->add(r); 6209 } 6210 _total_used += r->used(); 6211 } 6212 6213 return false; 6214 } 6215 6216 size_t total_used() { 6217 return _total_used; 6218 } 6219 }; 6220 6221 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6222 assert_at_safepoint(true /* should_be_vm_thread */); 6223 6224 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list); 6225 heap_region_iterate(&cl); 6226 6227 if (!free_list_only) { 6228 _summary_bytes_used = cl.total_used(); 6229 } 6230 assert(_summary_bytes_used == recalculate_used(), 6231 err_msg("inconsistent _summary_bytes_used, " 6232 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6233 _summary_bytes_used, recalculate_used())); 6234 } 6235 6236 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6237 _refine_cte_cl->set_concurrent(concurrent); 6238 } 6239 6240 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6241 HeapRegion* hr = heap_region_containing(p); 6242 if (hr == NULL) { 6243 return false; 6244 } else { 6245 return hr->is_in(p); 6246 } 6247 } 6248 6249 // Methods for the mutator alloc region 6250 6251 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6252 bool force) { 6253 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6254 assert(!force || g1_policy()->can_expand_young_list(), 6255 "if force is true we should be able to expand the young list"); 6256 bool young_list_full = g1_policy()->is_young_list_full(); 6257 if (force || !young_list_full) { 6258 HeapRegion* new_alloc_region = new_region(word_size, 6259 false /* do_expand */); 6260 if (new_alloc_region != NULL) { 6261 set_region_short_lived_locked(new_alloc_region); 6262 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6263 return new_alloc_region; 6264 } 6265 } 6266 return NULL; 6267 } 6268 6269 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6270 size_t allocated_bytes) { 6271 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6272 assert(alloc_region->is_young(), "all mutator alloc regions should be young"); 6273 6274 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6275 _summary_bytes_used += allocated_bytes; 6276 _hr_printer.retire(alloc_region); 6277 // We update the eden sizes here, when the region is retired, 6278 // instead of when it's allocated, since this is the point that its 6279 // used space has been recored in _summary_bytes_used. 6280 g1mm()->update_eden_size(); 6281 } 6282 6283 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, 6284 bool force) { 6285 return _g1h->new_mutator_alloc_region(word_size, force); 6286 } 6287 6288 void G1CollectedHeap::set_par_threads() { 6289 // Don't change the number of workers. Use the value previously set 6290 // in the workgroup. 6291 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6292 uint n_workers = workers()->active_workers(); 6293 assert(UseDynamicNumberOfGCThreads || 6294 n_workers == workers()->total_workers(), 6295 "Otherwise should be using the total number of workers"); 6296 if (n_workers == 0) { 6297 assert(false, "Should have been set in prior evacuation pause."); 6298 n_workers = ParallelGCThreads; 6299 workers()->set_active_workers(n_workers); 6300 } 6301 set_par_threads(n_workers); 6302 } 6303 6304 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, 6305 size_t allocated_bytes) { 6306 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); 6307 } 6308 6309 // Methods for the GC alloc regions 6310 6311 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6312 uint count, 6313 GCAllocPurpose ap) { 6314 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6315 6316 if (count < g1_policy()->max_regions(ap)) { 6317 HeapRegion* new_alloc_region = new_region(word_size, 6318 true /* do_expand */); 6319 if (new_alloc_region != NULL) { 6320 // We really only need to do this for old regions given that we 6321 // should never scan survivors. But it doesn't hurt to do it 6322 // for survivors too. 6323 new_alloc_region->set_saved_mark(); 6324 if (ap == GCAllocForSurvived) { 6325 new_alloc_region->set_survivor(); 6326 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6327 } else { 6328 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6329 } 6330 bool during_im = g1_policy()->during_initial_mark_pause(); 6331 new_alloc_region->note_start_of_copying(during_im); 6332 return new_alloc_region; 6333 } else { 6334 g1_policy()->note_alloc_region_limit_reached(ap); 6335 } 6336 } 6337 return NULL; 6338 } 6339 6340 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6341 size_t allocated_bytes, 6342 GCAllocPurpose ap) { 6343 bool during_im = g1_policy()->during_initial_mark_pause(); 6344 alloc_region->note_end_of_copying(during_im); 6345 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6346 if (ap == GCAllocForSurvived) { 6347 young_list()->add_survivor_region(alloc_region); 6348 } else { 6349 _old_set.add(alloc_region); 6350 } 6351 _hr_printer.retire(alloc_region); 6352 } 6353 6354 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, 6355 bool force) { 6356 assert(!force, "not supported for GC alloc regions"); 6357 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); 6358 } 6359 6360 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, 6361 size_t allocated_bytes) { 6362 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6363 GCAllocForSurvived); 6364 } 6365 6366 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, 6367 bool force) { 6368 assert(!force, "not supported for GC alloc regions"); 6369 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); 6370 } 6371 6372 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, 6373 size_t allocated_bytes) { 6374 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6375 GCAllocForTenured); 6376 } 6377 // Heap region set verification 6378 6379 class VerifyRegionListsClosure : public HeapRegionClosure { 6380 private: 6381 FreeRegionList* _free_list; 6382 OldRegionSet* _old_set; 6383 HumongousRegionSet* _humongous_set; 6384 uint _region_count; 6385 6386 public: 6387 VerifyRegionListsClosure(OldRegionSet* old_set, 6388 HumongousRegionSet* humongous_set, 6389 FreeRegionList* free_list) : 6390 _old_set(old_set), _humongous_set(humongous_set), 6391 _free_list(free_list), _region_count(0) { } 6392 6393 uint region_count() { return _region_count; } 6394 6395 bool doHeapRegion(HeapRegion* hr) { 6396 _region_count += 1; 6397 6398 if (hr->continuesHumongous()) { 6399 return false; 6400 } 6401 6402 if (hr->is_young()) { 6403 // TODO 6404 } else if (hr->startsHumongous()) { 6405 _humongous_set->verify_next_region(hr); 6406 } else if (hr->is_empty()) { 6407 _free_list->verify_next_region(hr); 6408 } else { 6409 _old_set->verify_next_region(hr); 6410 } 6411 return false; 6412 } 6413 }; 6414 6415 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 6416 HeapWord* bottom) { 6417 HeapWord* end = bottom + HeapRegion::GrainWords; 6418 MemRegion mr(bottom, end); 6419 assert(_g1_reserved.contains(mr), "invariant"); 6420 // This might return NULL if the allocation fails 6421 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */); 6422 } 6423 6424 void G1CollectedHeap::verify_region_sets() { 6425 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6426 6427 // First, check the explicit lists. 6428 _free_list.verify(); 6429 { 6430 // Given that a concurrent operation might be adding regions to 6431 // the secondary free list we have to take the lock before 6432 // verifying it. 6433 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6434 _secondary_free_list.verify(); 6435 } 6436 _old_set.verify(); 6437 _humongous_set.verify(); 6438 6439 // If a concurrent region freeing operation is in progress it will 6440 // be difficult to correctly attributed any free regions we come 6441 // across to the correct free list given that they might belong to 6442 // one of several (free_list, secondary_free_list, any local lists, 6443 // etc.). So, if that's the case we will skip the rest of the 6444 // verification operation. Alternatively, waiting for the concurrent 6445 // operation to complete will have a non-trivial effect on the GC's 6446 // operation (no concurrent operation will last longer than the 6447 // interval between two calls to verification) and it might hide 6448 // any issues that we would like to catch during testing. 6449 if (free_regions_coming()) { 6450 return; 6451 } 6452 6453 // Make sure we append the secondary_free_list on the free_list so 6454 // that all free regions we will come across can be safely 6455 // attributed to the free_list. 6456 append_secondary_free_list_if_not_empty_with_lock(); 6457 6458 // Finally, make sure that the region accounting in the lists is 6459 // consistent with what we see in the heap. 6460 _old_set.verify_start(); 6461 _humongous_set.verify_start(); 6462 _free_list.verify_start(); 6463 6464 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list); 6465 heap_region_iterate(&cl); 6466 6467 _old_set.verify_end(); 6468 _humongous_set.verify_end(); 6469 _free_list.verify_end(); 6470 }