1 /* 2 * Copyright (c) 2001, 2013, 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 int dummy_gclocker_retry_count = 0; 858 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 859 } 860 861 HeapWord* 862 G1CollectedHeap::mem_allocate(size_t word_size, 863 bool* gc_overhead_limit_was_exceeded) { 864 assert_heap_not_locked_and_not_at_safepoint(); 865 866 // Loop until the allocation is satisified, or unsatisfied after GC. 867 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 868 unsigned int gc_count_before; 869 870 HeapWord* result = NULL; 871 if (!isHumongous(word_size)) { 872 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 873 } else { 874 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 875 } 876 if (result != NULL) { 877 return result; 878 } 879 880 // Create the garbage collection operation... 881 VM_G1CollectForAllocation op(gc_count_before, word_size); 882 // ...and get the VM thread to execute it. 883 VMThread::execute(&op); 884 885 if (op.prologue_succeeded() && op.pause_succeeded()) { 886 // If the operation was successful we'll return the result even 887 // if it is NULL. If the allocation attempt failed immediately 888 // after a Full GC, it's unlikely we'll be able to allocate now. 889 HeapWord* result = op.result(); 890 if (result != NULL && !isHumongous(word_size)) { 891 // Allocations that take place on VM operations do not do any 892 // card dirtying and we have to do it here. We only have to do 893 // this for non-humongous allocations, though. 894 dirty_young_block(result, word_size); 895 } 896 return result; 897 } else { 898 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 899 return NULL; 900 } 901 assert(op.result() == NULL, 902 "the result should be NULL if the VM op did not succeed"); 903 } 904 905 // Give a warning if we seem to be looping forever. 906 if ((QueuedAllocationWarningCount > 0) && 907 (try_count % QueuedAllocationWarningCount == 0)) { 908 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 909 } 910 } 911 912 ShouldNotReachHere(); 913 return NULL; 914 } 915 916 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 917 unsigned int *gc_count_before_ret, 918 int* gclocker_retry_count_ret) { 919 // Make sure you read the note in attempt_allocation_humongous(). 920 921 assert_heap_not_locked_and_not_at_safepoint(); 922 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 923 "be called for humongous allocation requests"); 924 925 // We should only get here after the first-level allocation attempt 926 // (attempt_allocation()) failed to allocate. 927 928 // We will loop until a) we manage to successfully perform the 929 // allocation or b) we successfully schedule a collection which 930 // fails to perform the allocation. b) is the only case when we'll 931 // return NULL. 932 HeapWord* result = NULL; 933 for (int try_count = 1; /* we'll return */; try_count += 1) { 934 bool should_try_gc; 935 unsigned int gc_count_before; 936 937 { 938 MutexLockerEx x(Heap_lock); 939 940 result = _mutator_alloc_region.attempt_allocation_locked(word_size, 941 false /* bot_updates */); 942 if (result != NULL) { 943 return result; 944 } 945 946 // If we reach here, attempt_allocation_locked() above failed to 947 // allocate a new region. So the mutator alloc region should be NULL. 948 assert(_mutator_alloc_region.get() == NULL, "only way to get here"); 949 950 if (GC_locker::is_active_and_needs_gc()) { 951 if (g1_policy()->can_expand_young_list()) { 952 // No need for an ergo verbose message here, 953 // can_expand_young_list() does this when it returns true. 954 result = _mutator_alloc_region.attempt_allocation_force(word_size, 955 false /* bot_updates */); 956 if (result != NULL) { 957 return result; 958 } 959 } 960 should_try_gc = false; 961 } else { 962 // The GCLocker may not be active but the GCLocker initiated 963 // GC may not yet have been performed (GCLocker::needs_gc() 964 // returns true). In this case we do not try this GC and 965 // wait until the GCLocker initiated GC is performed, and 966 // then retry the allocation. 967 if (GC_locker::needs_gc()) { 968 should_try_gc = false; 969 } else { 970 // Read the GC count while still holding the Heap_lock. 971 gc_count_before = total_collections(); 972 should_try_gc = true; 973 } 974 } 975 } 976 977 if (should_try_gc) { 978 bool succeeded; 979 result = do_collection_pause(word_size, gc_count_before, &succeeded); 980 if (result != NULL) { 981 assert(succeeded, "only way to get back a non-NULL result"); 982 return result; 983 } 984 985 if (succeeded) { 986 // If we get here we successfully scheduled a collection which 987 // failed to allocate. No point in trying to allocate 988 // further. We'll just return NULL. 989 MutexLockerEx x(Heap_lock); 990 *gc_count_before_ret = total_collections(); 991 return NULL; 992 } 993 } else { 994 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 995 MutexLockerEx x(Heap_lock); 996 *gc_count_before_ret = total_collections(); 997 return NULL; 998 } 999 // The GCLocker is either active or the GCLocker initiated 1000 // GC has not yet been performed. Stall until it is and 1001 // then retry the allocation. 1002 GC_locker::stall_until_clear(); 1003 (*gclocker_retry_count_ret) += 1; 1004 } 1005 1006 // We can reach here if we were unsuccessul in scheduling a 1007 // collection (because another thread beat us to it) or if we were 1008 // stalled due to the GC locker. In either can we should retry the 1009 // allocation attempt in case another thread successfully 1010 // performed a collection and reclaimed enough space. We do the 1011 // first attempt (without holding the Heap_lock) here and the 1012 // follow-on attempt will be at the start of the next loop 1013 // iteration (after taking the Heap_lock). 1014 result = _mutator_alloc_region.attempt_allocation(word_size, 1015 false /* bot_updates */); 1016 if (result != NULL) { 1017 return result; 1018 } 1019 1020 // Give a warning if we seem to be looping forever. 1021 if ((QueuedAllocationWarningCount > 0) && 1022 (try_count % QueuedAllocationWarningCount == 0)) { 1023 warning("G1CollectedHeap::attempt_allocation_slow() " 1024 "retries %d times", try_count); 1025 } 1026 } 1027 1028 ShouldNotReachHere(); 1029 return NULL; 1030 } 1031 1032 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1033 unsigned int * gc_count_before_ret, 1034 int* gclocker_retry_count_ret) { 1035 // The structure of this method has a lot of similarities to 1036 // attempt_allocation_slow(). The reason these two were not merged 1037 // into a single one is that such a method would require several "if 1038 // allocation is not humongous do this, otherwise do that" 1039 // conditional paths which would obscure its flow. In fact, an early 1040 // version of this code did use a unified method which was harder to 1041 // follow and, as a result, it had subtle bugs that were hard to 1042 // track down. So keeping these two methods separate allows each to 1043 // be more readable. It will be good to keep these two in sync as 1044 // much as possible. 1045 1046 assert_heap_not_locked_and_not_at_safepoint(); 1047 assert(isHumongous(word_size), "attempt_allocation_humongous() " 1048 "should only be called for humongous allocations"); 1049 1050 // Humongous objects can exhaust the heap quickly, so we should check if we 1051 // need to start a marking cycle at each humongous object allocation. We do 1052 // the check before we do the actual allocation. The reason for doing it 1053 // before the allocation is that we avoid having to keep track of the newly 1054 // allocated memory while we do a GC. 1055 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1056 word_size)) { 1057 collect(GCCause::_g1_humongous_allocation); 1058 } 1059 1060 // We will loop until a) we manage to successfully perform the 1061 // allocation or b) we successfully schedule a collection which 1062 // fails to perform the allocation. b) is the only case when we'll 1063 // return NULL. 1064 HeapWord* result = NULL; 1065 for (int try_count = 1; /* we'll return */; try_count += 1) { 1066 bool should_try_gc; 1067 unsigned int gc_count_before; 1068 1069 { 1070 MutexLockerEx x(Heap_lock); 1071 1072 // Given that humongous objects are not allocated in young 1073 // regions, we'll first try to do the allocation without doing a 1074 // collection hoping that there's enough space in the heap. 1075 result = humongous_obj_allocate(word_size); 1076 if (result != NULL) { 1077 return result; 1078 } 1079 1080 if (GC_locker::is_active_and_needs_gc()) { 1081 should_try_gc = false; 1082 } else { 1083 // The GCLocker may not be active but the GCLocker initiated 1084 // GC may not yet have been performed (GCLocker::needs_gc() 1085 // returns true). In this case we do not try this GC and 1086 // wait until the GCLocker initiated GC is performed, and 1087 // then retry the allocation. 1088 if (GC_locker::needs_gc()) { 1089 should_try_gc = false; 1090 } else { 1091 // Read the GC count while still holding the Heap_lock. 1092 gc_count_before = total_collections(); 1093 should_try_gc = true; 1094 } 1095 } 1096 } 1097 1098 if (should_try_gc) { 1099 // If we failed to allocate the humongous object, we should try to 1100 // do a collection pause (if we're allowed) in case it reclaims 1101 // enough space for the allocation to succeed after the pause. 1102 1103 bool succeeded; 1104 result = do_collection_pause(word_size, gc_count_before, &succeeded); 1105 if (result != NULL) { 1106 assert(succeeded, "only way to get back a non-NULL result"); 1107 return result; 1108 } 1109 1110 if (succeeded) { 1111 // If we get here we successfully scheduled a collection which 1112 // failed to allocate. No point in trying to allocate 1113 // further. We'll just return NULL. 1114 MutexLockerEx x(Heap_lock); 1115 *gc_count_before_ret = total_collections(); 1116 return NULL; 1117 } 1118 } else { 1119 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1120 MutexLockerEx x(Heap_lock); 1121 *gc_count_before_ret = total_collections(); 1122 return NULL; 1123 } 1124 // The GCLocker is either active or the GCLocker initiated 1125 // GC has not yet been performed. Stall until it is and 1126 // then retry the allocation. 1127 GC_locker::stall_until_clear(); 1128 (*gclocker_retry_count_ret) += 1; 1129 } 1130 1131 // We can reach here if we were unsuccessul in scheduling a 1132 // collection (because another thread beat us to it) or if we were 1133 // stalled due to the GC locker. In either can we should retry the 1134 // allocation attempt in case another thread successfully 1135 // performed a collection and reclaimed enough space. Give a 1136 // warning if we seem to be looping forever. 1137 1138 if ((QueuedAllocationWarningCount > 0) && 1139 (try_count % QueuedAllocationWarningCount == 0)) { 1140 warning("G1CollectedHeap::attempt_allocation_humongous() " 1141 "retries %d times", try_count); 1142 } 1143 } 1144 1145 ShouldNotReachHere(); 1146 return NULL; 1147 } 1148 1149 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1150 bool expect_null_mutator_alloc_region) { 1151 assert_at_safepoint(true /* should_be_vm_thread */); 1152 assert(_mutator_alloc_region.get() == NULL || 1153 !expect_null_mutator_alloc_region, 1154 "the current alloc region was unexpectedly found to be non-NULL"); 1155 1156 if (!isHumongous(word_size)) { 1157 return _mutator_alloc_region.attempt_allocation_locked(word_size, 1158 false /* bot_updates */); 1159 } else { 1160 HeapWord* result = humongous_obj_allocate(word_size); 1161 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1162 g1_policy()->set_initiate_conc_mark_if_possible(); 1163 } 1164 return result; 1165 } 1166 1167 ShouldNotReachHere(); 1168 } 1169 1170 class PostMCRemSetClearClosure: public HeapRegionClosure { 1171 G1CollectedHeap* _g1h; 1172 ModRefBarrierSet* _mr_bs; 1173 public: 1174 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1175 _g1h(g1h), _mr_bs(mr_bs) { } 1176 bool doHeapRegion(HeapRegion* r) { 1177 if (r->continuesHumongous()) { 1178 return false; 1179 } 1180 _g1h->reset_gc_time_stamps(r); 1181 HeapRegionRemSet* hrrs = r->rem_set(); 1182 if (hrrs != NULL) hrrs->clear(); 1183 // You might think here that we could clear just the cards 1184 // corresponding to the used region. But no: if we leave a dirty card 1185 // in a region we might allocate into, then it would prevent that card 1186 // from being enqueued, and cause it to be missed. 1187 // Re: the performance cost: we shouldn't be doing full GC anyway! 1188 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1189 return false; 1190 } 1191 }; 1192 1193 void G1CollectedHeap::clear_rsets_post_compaction() { 1194 PostMCRemSetClearClosure rs_clear(this, mr_bs()); 1195 heap_region_iterate(&rs_clear); 1196 } 1197 1198 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1199 G1CollectedHeap* _g1h; 1200 UpdateRSOopClosure _cl; 1201 int _worker_i; 1202 public: 1203 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1204 _cl(g1->g1_rem_set(), worker_i), 1205 _worker_i(worker_i), 1206 _g1h(g1) 1207 { } 1208 1209 bool doHeapRegion(HeapRegion* r) { 1210 if (!r->continuesHumongous()) { 1211 _cl.set_from(r); 1212 r->oop_iterate(&_cl); 1213 } 1214 return false; 1215 } 1216 }; 1217 1218 class ParRebuildRSTask: public AbstractGangTask { 1219 G1CollectedHeap* _g1; 1220 public: 1221 ParRebuildRSTask(G1CollectedHeap* g1) 1222 : AbstractGangTask("ParRebuildRSTask"), 1223 _g1(g1) 1224 { } 1225 1226 void work(uint worker_id) { 1227 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1228 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id, 1229 _g1->workers()->active_workers(), 1230 HeapRegion::RebuildRSClaimValue); 1231 } 1232 }; 1233 1234 class PostCompactionPrinterClosure: public HeapRegionClosure { 1235 private: 1236 G1HRPrinter* _hr_printer; 1237 public: 1238 bool doHeapRegion(HeapRegion* hr) { 1239 assert(!hr->is_young(), "not expecting to find young regions"); 1240 // We only generate output for non-empty regions. 1241 if (!hr->is_empty()) { 1242 if (!hr->isHumongous()) { 1243 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1244 } else if (hr->startsHumongous()) { 1245 if (hr->region_num() == 1) { 1246 // single humongous region 1247 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1248 } else { 1249 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1250 } 1251 } else { 1252 assert(hr->continuesHumongous(), "only way to get here"); 1253 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1254 } 1255 } 1256 return false; 1257 } 1258 1259 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1260 : _hr_printer(hr_printer) { } 1261 }; 1262 1263 void G1CollectedHeap::print_hrs_post_compaction() { 1264 PostCompactionPrinterClosure cl(hr_printer()); 1265 heap_region_iterate(&cl); 1266 } 1267 1268 double G1CollectedHeap::verify(bool guard, const char* msg) { 1269 double verify_time_ms = 0.0; 1270 1271 if (guard && total_collections() >= VerifyGCStartAt) { 1272 double verify_start = os::elapsedTime(); 1273 HandleMark hm; // Discard invalid handles created during verification 1274 prepare_for_verify(); 1275 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 1276 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 1277 } 1278 1279 return verify_time_ms; 1280 } 1281 1282 void G1CollectedHeap::verify_before_gc() { 1283 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 1284 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 1285 } 1286 1287 void G1CollectedHeap::verify_after_gc() { 1288 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 1289 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 1290 } 1291 1292 bool G1CollectedHeap::do_collection(bool explicit_gc, 1293 bool clear_all_soft_refs, 1294 size_t word_size) { 1295 assert_at_safepoint(true /* should_be_vm_thread */); 1296 1297 if (GC_locker::check_active_before_gc()) { 1298 return false; 1299 } 1300 1301 SvcGCMarker sgcm(SvcGCMarker::FULL); 1302 ResourceMark rm; 1303 1304 print_heap_before_gc(); 1305 1306 size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes(); 1307 1308 HRSPhaseSetter x(HRSPhaseFullGC); 1309 verify_region_sets_optional(); 1310 1311 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1312 collector_policy()->should_clear_all_soft_refs(); 1313 1314 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1315 1316 { 1317 IsGCActiveMark x; 1318 1319 // Timing 1320 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1321 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps); 1322 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1323 1324 { 1325 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty); 1326 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1327 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1328 1329 double start = os::elapsedTime(); 1330 g1_policy()->record_full_collection_start(); 1331 1332 // Note: When we have a more flexible GC logging framework that 1333 // allows us to add optional attributes to a GC log record we 1334 // could consider timing and reporting how long we wait in the 1335 // following two methods. 1336 wait_while_free_regions_coming(); 1337 // If we start the compaction before the CM threads finish 1338 // scanning the root regions we might trip them over as we'll 1339 // be moving objects / updating references. So let's wait until 1340 // they are done. By telling them to abort, they should complete 1341 // early. 1342 _cm->root_regions()->abort(); 1343 _cm->root_regions()->wait_until_scan_finished(); 1344 append_secondary_free_list_if_not_empty_with_lock(); 1345 1346 gc_prologue(true); 1347 increment_total_collections(true /* full gc */); 1348 increment_old_marking_cycles_started(); 1349 1350 assert(used() == recalculate_used(), "Should be equal"); 1351 1352 verify_before_gc(); 1353 1354 pre_full_gc_dump(); 1355 1356 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1357 1358 // Disable discovery and empty the discovered lists 1359 // for the CM ref processor. 1360 ref_processor_cm()->disable_discovery(); 1361 ref_processor_cm()->abandon_partial_discovery(); 1362 ref_processor_cm()->verify_no_references_recorded(); 1363 1364 // Abandon current iterations of concurrent marking and concurrent 1365 // refinement, if any are in progress. We have to do this before 1366 // wait_until_scan_finished() below. 1367 concurrent_mark()->abort(); 1368 1369 // Make sure we'll choose a new allocation region afterwards. 1370 release_mutator_alloc_region(); 1371 abandon_gc_alloc_regions(); 1372 g1_rem_set()->cleanupHRRS(); 1373 1374 // We should call this after we retire any currently active alloc 1375 // regions so that all the ALLOC / RETIRE events are generated 1376 // before the start GC event. 1377 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1378 1379 // We may have added regions to the current incremental collection 1380 // set between the last GC or pause and now. We need to clear the 1381 // incremental collection set and then start rebuilding it afresh 1382 // after this full GC. 1383 abandon_collection_set(g1_policy()->inc_cset_head()); 1384 g1_policy()->clear_incremental_cset(); 1385 g1_policy()->stop_incremental_cset_building(); 1386 1387 tear_down_region_sets(false /* free_list_only */); 1388 g1_policy()->set_gcs_are_young(true); 1389 1390 // See the comments in g1CollectedHeap.hpp and 1391 // G1CollectedHeap::ref_processing_init() about 1392 // how reference processing currently works in G1. 1393 1394 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1395 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1396 1397 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1398 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1399 1400 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1401 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1402 1403 // Do collection work 1404 { 1405 HandleMark hm; // Discard invalid handles created during gc 1406 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1407 } 1408 1409 assert(free_regions() == 0, "we should not have added any free regions"); 1410 rebuild_region_sets(false /* free_list_only */); 1411 1412 // Enqueue any discovered reference objects that have 1413 // not been removed from the discovered lists. 1414 ref_processor_stw()->enqueue_discovered_references(); 1415 1416 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1417 1418 MemoryService::track_memory_usage(); 1419 1420 verify_after_gc(); 1421 1422 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1423 ref_processor_stw()->verify_no_references_recorded(); 1424 1425 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1426 ClassLoaderDataGraph::purge(); 1427 MetaspaceAux::verify_metrics(); 1428 1429 // Note: since we've just done a full GC, concurrent 1430 // marking is no longer active. Therefore we need not 1431 // re-enable reference discovery for the CM ref processor. 1432 // That will be done at the start of the next marking cycle. 1433 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1434 ref_processor_cm()->verify_no_references_recorded(); 1435 1436 reset_gc_time_stamp(); 1437 // Since everything potentially moved, we will clear all remembered 1438 // sets, and clear all cards. Later we will rebuild remebered 1439 // sets. We will also reset the GC time stamps of the regions. 1440 clear_rsets_post_compaction(); 1441 check_gc_time_stamps(); 1442 1443 // Resize the heap if necessary. 1444 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1445 1446 if (_hr_printer.is_active()) { 1447 // We should do this after we potentially resize the heap so 1448 // that all the COMMIT / UNCOMMIT events are generated before 1449 // the end GC event. 1450 1451 print_hrs_post_compaction(); 1452 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1453 } 1454 1455 if (_cg1r->use_cache()) { 1456 _cg1r->clear_and_record_card_counts(); 1457 _cg1r->clear_hot_cache(); 1458 } 1459 1460 // Rebuild remembered sets of all regions. 1461 if (G1CollectedHeap::use_parallel_gc_threads()) { 1462 uint n_workers = 1463 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1464 workers()->active_workers(), 1465 Threads::number_of_non_daemon_threads()); 1466 assert(UseDynamicNumberOfGCThreads || 1467 n_workers == workers()->total_workers(), 1468 "If not dynamic should be using all the workers"); 1469 workers()->set_active_workers(n_workers); 1470 // Set parallel threads in the heap (_n_par_threads) only 1471 // before a parallel phase and always reset it to 0 after 1472 // the phase so that the number of parallel threads does 1473 // no get carried forward to a serial phase where there 1474 // may be code that is "possibly_parallel". 1475 set_par_threads(n_workers); 1476 1477 ParRebuildRSTask rebuild_rs_task(this); 1478 assert(check_heap_region_claim_values( 1479 HeapRegion::InitialClaimValue), "sanity check"); 1480 assert(UseDynamicNumberOfGCThreads || 1481 workers()->active_workers() == workers()->total_workers(), 1482 "Unless dynamic should use total workers"); 1483 // Use the most recent number of active workers 1484 assert(workers()->active_workers() > 0, 1485 "Active workers not properly set"); 1486 set_par_threads(workers()->active_workers()); 1487 workers()->run_task(&rebuild_rs_task); 1488 set_par_threads(0); 1489 assert(check_heap_region_claim_values( 1490 HeapRegion::RebuildRSClaimValue), "sanity check"); 1491 reset_heap_region_claim_values(); 1492 } else { 1493 RebuildRSOutOfRegionClosure rebuild_rs(this); 1494 heap_region_iterate(&rebuild_rs); 1495 } 1496 1497 if (true) { // FIXME 1498 MetaspaceGC::compute_new_size(); 1499 } 1500 1501 #ifdef TRACESPINNING 1502 ParallelTaskTerminator::print_termination_counts(); 1503 #endif 1504 1505 // Discard all rset updates 1506 JavaThread::dirty_card_queue_set().abandon_logs(); 1507 assert(!G1DeferredRSUpdate 1508 || (G1DeferredRSUpdate && 1509 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); 1510 1511 _young_list->reset_sampled_info(); 1512 // At this point there should be no regions in the 1513 // entire heap tagged as young. 1514 assert(check_young_list_empty(true /* check_heap */), 1515 "young list should be empty at this point"); 1516 1517 // Update the number of full collections that have been completed. 1518 increment_old_marking_cycles_completed(false /* concurrent */); 1519 1520 _hrs.verify_optional(); 1521 verify_region_sets_optional(); 1522 1523 // Start a new incremental collection set for the next pause 1524 assert(g1_policy()->collection_set() == NULL, "must be"); 1525 g1_policy()->start_incremental_cset_building(); 1526 1527 // Clear the _cset_fast_test bitmap in anticipation of adding 1528 // regions to the incremental collection set for the next 1529 // evacuation pause. 1530 clear_cset_fast_test(); 1531 1532 init_mutator_alloc_region(); 1533 1534 double end = os::elapsedTime(); 1535 g1_policy()->record_full_collection_end(); 1536 1537 if (G1Log::fine()) { 1538 g1_policy()->print_heap_transition(); 1539 } 1540 1541 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1542 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1543 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1544 // before any GC notifications are raised. 1545 g1mm()->update_sizes(); 1546 1547 gc_epilogue(true); 1548 } 1549 1550 if (G1Log::finer()) { 1551 g1_policy()->print_detailed_heap_transition(); 1552 } 1553 1554 print_heap_after_gc(); 1555 1556 post_full_gc_dump(); 1557 } 1558 1559 return true; 1560 } 1561 1562 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1563 // do_collection() will return whether it succeeded in performing 1564 // the GC. Currently, there is no facility on the 1565 // do_full_collection() API to notify the caller than the collection 1566 // did not succeed (e.g., because it was locked out by the GC 1567 // locker). So, right now, we'll ignore the return value. 1568 bool dummy = do_collection(true, /* explicit_gc */ 1569 clear_all_soft_refs, 1570 0 /* word_size */); 1571 } 1572 1573 // This code is mostly copied from TenuredGeneration. 1574 void 1575 G1CollectedHeap:: 1576 resize_if_necessary_after_full_collection(size_t word_size) { 1577 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check"); 1578 1579 // Include the current allocation, if any, and bytes that will be 1580 // pre-allocated to support collections, as "used". 1581 const size_t used_after_gc = used(); 1582 const size_t capacity_after_gc = capacity(); 1583 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1584 1585 // This is enforced in arguments.cpp. 1586 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1587 "otherwise the code below doesn't make sense"); 1588 1589 // We don't have floating point command-line arguments 1590 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1591 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1592 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1593 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1594 1595 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1596 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1597 1598 // We have to be careful here as these two calculations can overflow 1599 // 32-bit size_t's. 1600 double used_after_gc_d = (double) used_after_gc; 1601 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1602 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1603 1604 // Let's make sure that they are both under the max heap size, which 1605 // by default will make them fit into a size_t. 1606 double desired_capacity_upper_bound = (double) max_heap_size; 1607 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1608 desired_capacity_upper_bound); 1609 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1610 desired_capacity_upper_bound); 1611 1612 // We can now safely turn them into size_t's. 1613 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1614 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1615 1616 // This assert only makes sense here, before we adjust them 1617 // with respect to the min and max heap size. 1618 assert(minimum_desired_capacity <= maximum_desired_capacity, 1619 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1620 "maximum_desired_capacity = "SIZE_FORMAT, 1621 minimum_desired_capacity, maximum_desired_capacity)); 1622 1623 // Should not be greater than the heap max size. No need to adjust 1624 // it with respect to the heap min size as it's a lower bound (i.e., 1625 // we'll try to make the capacity larger than it, not smaller). 1626 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1627 // Should not be less than the heap min size. No need to adjust it 1628 // with respect to the heap max size as it's an upper bound (i.e., 1629 // we'll try to make the capacity smaller than it, not greater). 1630 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1631 1632 if (capacity_after_gc < minimum_desired_capacity) { 1633 // Don't expand unless it's significant 1634 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1635 ergo_verbose4(ErgoHeapSizing, 1636 "attempt heap expansion", 1637 ergo_format_reason("capacity lower than " 1638 "min desired capacity after Full GC") 1639 ergo_format_byte("capacity") 1640 ergo_format_byte("occupancy") 1641 ergo_format_byte_perc("min desired capacity"), 1642 capacity_after_gc, used_after_gc, 1643 minimum_desired_capacity, (double) MinHeapFreeRatio); 1644 expand(expand_bytes); 1645 1646 // No expansion, now see if we want to shrink 1647 } else if (capacity_after_gc > maximum_desired_capacity) { 1648 // Capacity too large, compute shrinking size 1649 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1650 ergo_verbose4(ErgoHeapSizing, 1651 "attempt heap shrinking", 1652 ergo_format_reason("capacity higher than " 1653 "max desired capacity after Full GC") 1654 ergo_format_byte("capacity") 1655 ergo_format_byte("occupancy") 1656 ergo_format_byte_perc("max desired capacity"), 1657 capacity_after_gc, used_after_gc, 1658 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1659 shrink(shrink_bytes); 1660 } 1661 } 1662 1663 1664 HeapWord* 1665 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1666 bool* succeeded) { 1667 assert_at_safepoint(true /* should_be_vm_thread */); 1668 1669 *succeeded = true; 1670 // Let's attempt the allocation first. 1671 HeapWord* result = 1672 attempt_allocation_at_safepoint(word_size, 1673 false /* expect_null_mutator_alloc_region */); 1674 if (result != NULL) { 1675 assert(*succeeded, "sanity"); 1676 return result; 1677 } 1678 1679 // In a G1 heap, we're supposed to keep allocation from failing by 1680 // incremental pauses. Therefore, at least for now, we'll favor 1681 // expansion over collection. (This might change in the future if we can 1682 // do something smarter than full collection to satisfy a failed alloc.) 1683 result = expand_and_allocate(word_size); 1684 if (result != NULL) { 1685 assert(*succeeded, "sanity"); 1686 return result; 1687 } 1688 1689 // Expansion didn't work, we'll try to do a Full GC. 1690 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1691 false, /* clear_all_soft_refs */ 1692 word_size); 1693 if (!gc_succeeded) { 1694 *succeeded = false; 1695 return NULL; 1696 } 1697 1698 // Retry the allocation 1699 result = attempt_allocation_at_safepoint(word_size, 1700 true /* expect_null_mutator_alloc_region */); 1701 if (result != NULL) { 1702 assert(*succeeded, "sanity"); 1703 return result; 1704 } 1705 1706 // Then, try a Full GC that will collect all soft references. 1707 gc_succeeded = do_collection(false, /* explicit_gc */ 1708 true, /* clear_all_soft_refs */ 1709 word_size); 1710 if (!gc_succeeded) { 1711 *succeeded = false; 1712 return NULL; 1713 } 1714 1715 // Retry the allocation once more 1716 result = attempt_allocation_at_safepoint(word_size, 1717 true /* expect_null_mutator_alloc_region */); 1718 if (result != NULL) { 1719 assert(*succeeded, "sanity"); 1720 return result; 1721 } 1722 1723 assert(!collector_policy()->should_clear_all_soft_refs(), 1724 "Flag should have been handled and cleared prior to this point"); 1725 1726 // What else? We might try synchronous finalization later. If the total 1727 // space available is large enough for the allocation, then a more 1728 // complete compaction phase than we've tried so far might be 1729 // appropriate. 1730 assert(*succeeded, "sanity"); 1731 return NULL; 1732 } 1733 1734 // Attempting to expand the heap sufficiently 1735 // to support an allocation of the given "word_size". If 1736 // successful, perform the allocation and return the address of the 1737 // allocated block, or else "NULL". 1738 1739 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1740 assert_at_safepoint(true /* should_be_vm_thread */); 1741 1742 verify_region_sets_optional(); 1743 1744 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1745 ergo_verbose1(ErgoHeapSizing, 1746 "attempt heap expansion", 1747 ergo_format_reason("allocation request failed") 1748 ergo_format_byte("allocation request"), 1749 word_size * HeapWordSize); 1750 if (expand(expand_bytes)) { 1751 _hrs.verify_optional(); 1752 verify_region_sets_optional(); 1753 return attempt_allocation_at_safepoint(word_size, 1754 false /* expect_null_mutator_alloc_region */); 1755 } 1756 return NULL; 1757 } 1758 1759 void G1CollectedHeap::update_committed_space(HeapWord* old_end, 1760 HeapWord* new_end) { 1761 assert(old_end != new_end, "don't call this otherwise"); 1762 assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); 1763 1764 // Update the committed mem region. 1765 _g1_committed.set_end(new_end); 1766 // Tell the card table about the update. 1767 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); 1768 // Tell the BOT about the update. 1769 _bot_shared->resize(_g1_committed.word_size()); 1770 } 1771 1772 bool G1CollectedHeap::expand(size_t expand_bytes) { 1773 size_t old_mem_size = _g1_storage.committed_size(); 1774 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1775 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1776 HeapRegion::GrainBytes); 1777 ergo_verbose2(ErgoHeapSizing, 1778 "expand the heap", 1779 ergo_format_byte("requested expansion amount") 1780 ergo_format_byte("attempted expansion amount"), 1781 expand_bytes, aligned_expand_bytes); 1782 1783 // First commit the memory. 1784 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1785 bool successful = _g1_storage.expand_by(aligned_expand_bytes); 1786 if (successful) { 1787 // Then propagate this update to the necessary data structures. 1788 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1789 update_committed_space(old_end, new_end); 1790 1791 FreeRegionList expansion_list("Local Expansion List"); 1792 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); 1793 assert(mr.start() == old_end, "post-condition"); 1794 // mr might be a smaller region than what was requested if 1795 // expand_by() was unable to allocate the HeapRegion instances 1796 assert(mr.end() <= new_end, "post-condition"); 1797 1798 size_t actual_expand_bytes = mr.byte_size(); 1799 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1800 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), 1801 "post-condition"); 1802 if (actual_expand_bytes < aligned_expand_bytes) { 1803 // We could not expand _hrs to the desired size. In this case we 1804 // need to shrink the committed space accordingly. 1805 assert(mr.end() < new_end, "invariant"); 1806 1807 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; 1808 // First uncommit the memory. 1809 _g1_storage.shrink_by(diff_bytes); 1810 // Then propagate this update to the necessary data structures. 1811 update_committed_space(new_end, mr.end()); 1812 } 1813 _free_list.add_as_tail(&expansion_list); 1814 1815 if (_hr_printer.is_active()) { 1816 HeapWord* curr = mr.start(); 1817 while (curr < mr.end()) { 1818 HeapWord* curr_end = curr + HeapRegion::GrainWords; 1819 _hr_printer.commit(curr, curr_end); 1820 curr = curr_end; 1821 } 1822 assert(curr == mr.end(), "post-condition"); 1823 } 1824 g1_policy()->record_new_heap_size(n_regions()); 1825 } else { 1826 ergo_verbose0(ErgoHeapSizing, 1827 "did not expand the heap", 1828 ergo_format_reason("heap expansion operation failed")); 1829 // The expansion of the virtual storage space was unsuccessful. 1830 // Let's see if it was because we ran out of swap. 1831 if (G1ExitOnExpansionFailure && 1832 _g1_storage.uncommitted_size() >= aligned_expand_bytes) { 1833 // We had head room... 1834 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1835 } 1836 } 1837 return successful; 1838 } 1839 1840 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1841 size_t old_mem_size = _g1_storage.committed_size(); 1842 size_t aligned_shrink_bytes = 1843 ReservedSpace::page_align_size_down(shrink_bytes); 1844 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1845 HeapRegion::GrainBytes); 1846 uint num_regions_deleted = 0; 1847 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted); 1848 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1849 assert(mr.end() == old_end, "post-condition"); 1850 1851 ergo_verbose3(ErgoHeapSizing, 1852 "shrink the heap", 1853 ergo_format_byte("requested shrinking amount") 1854 ergo_format_byte("aligned shrinking amount") 1855 ergo_format_byte("attempted shrinking amount"), 1856 shrink_bytes, aligned_shrink_bytes, mr.byte_size()); 1857 if (mr.byte_size() > 0) { 1858 if (_hr_printer.is_active()) { 1859 HeapWord* curr = mr.end(); 1860 while (curr > mr.start()) { 1861 HeapWord* curr_end = curr; 1862 curr -= HeapRegion::GrainWords; 1863 _hr_printer.uncommit(curr, curr_end); 1864 } 1865 assert(curr == mr.start(), "post-condition"); 1866 } 1867 1868 _g1_storage.shrink_by(mr.byte_size()); 1869 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1870 assert(mr.start() == new_end, "post-condition"); 1871 1872 _expansion_regions += num_regions_deleted; 1873 update_committed_space(old_end, new_end); 1874 HeapRegionRemSet::shrink_heap(n_regions()); 1875 g1_policy()->record_new_heap_size(n_regions()); 1876 } else { 1877 ergo_verbose0(ErgoHeapSizing, 1878 "did not shrink the heap", 1879 ergo_format_reason("heap shrinking operation failed")); 1880 } 1881 } 1882 1883 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1884 verify_region_sets_optional(); 1885 1886 // We should only reach here at the end of a Full GC which means we 1887 // should not not be holding to any GC alloc regions. The method 1888 // below will make sure of that and do any remaining clean up. 1889 abandon_gc_alloc_regions(); 1890 1891 // Instead of tearing down / rebuilding the free lists here, we 1892 // could instead use the remove_all_pending() method on free_list to 1893 // remove only the ones that we need to remove. 1894 tear_down_region_sets(true /* free_list_only */); 1895 shrink_helper(shrink_bytes); 1896 rebuild_region_sets(true /* free_list_only */); 1897 1898 _hrs.verify_optional(); 1899 verify_region_sets_optional(); 1900 } 1901 1902 // Public methods. 1903 1904 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1905 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1906 #endif // _MSC_VER 1907 1908 1909 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1910 SharedHeap(policy_), 1911 _g1_policy(policy_), 1912 _dirty_card_queue_set(false), 1913 _into_cset_dirty_card_queue_set(false), 1914 _is_alive_closure_cm(this), 1915 _is_alive_closure_stw(this), 1916 _ref_processor_cm(NULL), 1917 _ref_processor_stw(NULL), 1918 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1919 _bot_shared(NULL), 1920 _evac_failure_scan_stack(NULL) , 1921 _mark_in_progress(false), 1922 _cg1r(NULL), _summary_bytes_used(0), 1923 _g1mm(NULL), 1924 _refine_cte_cl(NULL), 1925 _full_collection(false), 1926 _free_list("Master Free List"), 1927 _secondary_free_list("Secondary Free List"), 1928 _old_set("Old Set"), 1929 _humongous_set("Master Humongous Set"), 1930 _free_regions_coming(false), 1931 _young_list(new YoungList(this)), 1932 _gc_time_stamp(0), 1933 _retained_old_gc_alloc_region(NULL), 1934 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1935 _old_plab_stats(OldPLABSize, PLABWeight), 1936 _expand_heap_after_alloc_failure(true), 1937 _surviving_young_words(NULL), 1938 _old_marking_cycles_started(0), 1939 _old_marking_cycles_completed(0), 1940 _in_cset_fast_test(NULL), 1941 _in_cset_fast_test_base(NULL), 1942 _dirty_cards_region_list(NULL), 1943 _worker_cset_start_region(NULL), 1944 _worker_cset_start_region_time_stamp(NULL) { 1945 _g1h = this; // To catch bugs. 1946 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1947 vm_exit_during_initialization("Failed necessary allocation."); 1948 } 1949 1950 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1951 1952 int n_queues = MAX2((int)ParallelGCThreads, 1); 1953 _task_queues = new RefToScanQueueSet(n_queues); 1954 1955 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1956 assert(n_rem_sets > 0, "Invariant."); 1957 1958 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1959 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1960 1961 for (int i = 0; i < n_queues; i++) { 1962 RefToScanQueue* q = new RefToScanQueue(); 1963 q->initialize(); 1964 _task_queues->register_queue(i, q); 1965 } 1966 1967 clear_cset_start_regions(); 1968 1969 // Initialize the G1EvacuationFailureALot counters and flags. 1970 NOT_PRODUCT(reset_evacuation_should_fail();) 1971 1972 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1973 } 1974 1975 jint G1CollectedHeap::initialize() { 1976 CollectedHeap::pre_initialize(); 1977 os::enable_vtime(); 1978 1979 G1Log::init(); 1980 1981 // Necessary to satisfy locking discipline assertions. 1982 1983 MutexLocker x(Heap_lock); 1984 1985 // We have to initialize the printer before committing the heap, as 1986 // it will be used then. 1987 _hr_printer.set_active(G1PrintHeapRegions); 1988 1989 // While there are no constraints in the GC code that HeapWordSize 1990 // be any particular value, there are multiple other areas in the 1991 // system which believe this to be true (e.g. oop->object_size in some 1992 // cases incorrectly returns the size in wordSize units rather than 1993 // HeapWordSize). 1994 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1995 1996 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1997 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1998 1999 // Ensure that the sizes are properly aligned. 2000 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2001 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2002 2003 _cg1r = new ConcurrentG1Refine(); 2004 2005 // Reserve the maximum. 2006 2007 // When compressed oops are enabled, the preferred heap base 2008 // is calculated by subtracting the requested size from the 2009 // 32Gb boundary and using the result as the base address for 2010 // heap reservation. If the requested size is not aligned to 2011 // HeapRegion::GrainBytes (i.e. the alignment that is passed 2012 // into the ReservedHeapSpace constructor) then the actual 2013 // base of the reserved heap may end up differing from the 2014 // address that was requested (i.e. the preferred heap base). 2015 // If this happens then we could end up using a non-optimal 2016 // compressed oops mode. 2017 2018 // Since max_byte_size is aligned to the size of a heap region (checked 2019 // above). 2020 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2021 2022 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 2023 HeapRegion::GrainBytes); 2024 2025 // It is important to do this in a way such that concurrent readers can't 2026 // temporarily think somethings in the heap. (I've actually seen this 2027 // happen in asserts: DLD.) 2028 _reserved.set_word_size(0); 2029 _reserved.set_start((HeapWord*)heap_rs.base()); 2030 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 2031 2032 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes); 2033 2034 // Create the gen rem set (and barrier set) for the entire reserved region. 2035 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 2036 set_barrier_set(rem_set()->bs()); 2037 if (barrier_set()->is_a(BarrierSet::ModRef)) { 2038 _mr_bs = (ModRefBarrierSet*)_barrier_set; 2039 } else { 2040 vm_exit_during_initialization("G1 requires a mod ref bs."); 2041 return JNI_ENOMEM; 2042 } 2043 2044 // Also create a G1 rem set. 2045 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) { 2046 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs()); 2047 } else { 2048 vm_exit_during_initialization("G1 requires a cardtable mod ref bs."); 2049 return JNI_ENOMEM; 2050 } 2051 2052 // Carve out the G1 part of the heap. 2053 2054 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 2055 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), 2056 g1_rs.size()/HeapWordSize); 2057 2058 _g1_storage.initialize(g1_rs, 0); 2059 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); 2060 _hrs.initialize((HeapWord*) _g1_reserved.start(), 2061 (HeapWord*) _g1_reserved.end(), 2062 _expansion_regions); 2063 2064 // 6843694 - ensure that the maximum region index can fit 2065 // in the remembered set structures. 2066 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2067 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2068 2069 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2070 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2071 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2072 "too many cards per region"); 2073 2074 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1); 2075 2076 _bot_shared = new G1BlockOffsetSharedArray(_reserved, 2077 heap_word_size(init_byte_size)); 2078 2079 _g1h = this; 2080 2081 _in_cset_fast_test_length = max_regions(); 2082 _in_cset_fast_test_base = 2083 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC); 2084 2085 // We're biasing _in_cset_fast_test to avoid subtracting the 2086 // beginning of the heap every time we want to index; basically 2087 // it's the same with what we do with the card table. 2088 _in_cset_fast_test = _in_cset_fast_test_base - 2089 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes); 2090 2091 // Clear the _cset_fast_test bitmap in anticipation of adding 2092 // regions to the incremental collection set for the first 2093 // evacuation pause. 2094 clear_cset_fast_test(); 2095 2096 // Create the ConcurrentMark data structure and thread. 2097 // (Must do this late, so that "max_regions" is defined.) 2098 _cm = new ConcurrentMark(this, heap_rs); 2099 if (_cm == NULL || !_cm->completed_initialization()) { 2100 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2101 return JNI_ENOMEM; 2102 } 2103 _cmThread = _cm->cmThread(); 2104 2105 // Initialize the from_card cache structure of HeapRegionRemSet. 2106 HeapRegionRemSet::init_heap(max_regions()); 2107 2108 // Now expand into the initial heap size. 2109 if (!expand(init_byte_size)) { 2110 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2111 return JNI_ENOMEM; 2112 } 2113 2114 // Perform any initialization actions delegated to the policy. 2115 g1_policy()->init(); 2116 2117 _refine_cte_cl = 2118 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(), 2119 g1_rem_set(), 2120 concurrent_g1_refine()); 2121 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 2122 2123 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2124 SATB_Q_FL_lock, 2125 G1SATBProcessCompletedThreshold, 2126 Shared_SATB_Q_lock); 2127 2128 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2129 DirtyCardQ_FL_lock, 2130 concurrent_g1_refine()->yellow_zone(), 2131 concurrent_g1_refine()->red_zone(), 2132 Shared_DirtyCardQ_lock); 2133 2134 if (G1DeferredRSUpdate) { 2135 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2136 DirtyCardQ_FL_lock, 2137 -1, // never trigger processing 2138 -1, // no limit on length 2139 Shared_DirtyCardQ_lock, 2140 &JavaThread::dirty_card_queue_set()); 2141 } 2142 2143 // Initialize the card queue set used to hold cards containing 2144 // references into the collection set. 2145 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon, 2146 DirtyCardQ_FL_lock, 2147 -1, // never trigger processing 2148 -1, // no limit on length 2149 Shared_DirtyCardQ_lock, 2150 &JavaThread::dirty_card_queue_set()); 2151 2152 // In case we're keeping closure specialization stats, initialize those 2153 // counts and that mechanism. 2154 SpecializationStats::clear(); 2155 2156 // Do later initialization work for concurrent refinement. 2157 _cg1r->init(); 2158 2159 // Here we allocate the dummy full region that is required by the 2160 // G1AllocRegion class. If we don't pass an address in the reserved 2161 // space here, lots of asserts fire. 2162 2163 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, 2164 _g1_reserved.start()); 2165 // We'll re-use the same region whether the alloc region will 2166 // require BOT updates or not and, if it doesn't, then a non-young 2167 // region will complain that it cannot support allocations without 2168 // BOT updates. So we'll tag the dummy region as young to avoid that. 2169 dummy_region->set_young(); 2170 // Make sure it's full. 2171 dummy_region->set_top(dummy_region->end()); 2172 G1AllocRegion::setup(this, dummy_region); 2173 2174 init_mutator_alloc_region(); 2175 2176 // Do create of the monitoring and management support so that 2177 // values in the heap have been properly initialized. 2178 _g1mm = new G1MonitoringSupport(this); 2179 2180 return JNI_OK; 2181 } 2182 2183 void G1CollectedHeap::ref_processing_init() { 2184 // Reference processing in G1 currently works as follows: 2185 // 2186 // * There are two reference processor instances. One is 2187 // used to record and process discovered references 2188 // during concurrent marking; the other is used to 2189 // record and process references during STW pauses 2190 // (both full and incremental). 2191 // * Both ref processors need to 'span' the entire heap as 2192 // the regions in the collection set may be dotted around. 2193 // 2194 // * For the concurrent marking ref processor: 2195 // * Reference discovery is enabled at initial marking. 2196 // * Reference discovery is disabled and the discovered 2197 // references processed etc during remarking. 2198 // * Reference discovery is MT (see below). 2199 // * Reference discovery requires a barrier (see below). 2200 // * Reference processing may or may not be MT 2201 // (depending on the value of ParallelRefProcEnabled 2202 // and ParallelGCThreads). 2203 // * A full GC disables reference discovery by the CM 2204 // ref processor and abandons any entries on it's 2205 // discovered lists. 2206 // 2207 // * For the STW processor: 2208 // * Non MT discovery is enabled at the start of a full GC. 2209 // * Processing and enqueueing during a full GC is non-MT. 2210 // * During a full GC, references are processed after marking. 2211 // 2212 // * Discovery (may or may not be MT) is enabled at the start 2213 // of an incremental evacuation pause. 2214 // * References are processed near the end of a STW evacuation pause. 2215 // * For both types of GC: 2216 // * Discovery is atomic - i.e. not concurrent. 2217 // * Reference discovery will not need a barrier. 2218 2219 SharedHeap::ref_processing_init(); 2220 MemRegion mr = reserved_region(); 2221 2222 // Concurrent Mark ref processor 2223 _ref_processor_cm = 2224 new ReferenceProcessor(mr, // span 2225 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2226 // mt processing 2227 (int) ParallelGCThreads, 2228 // degree of mt processing 2229 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2230 // mt discovery 2231 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2232 // degree of mt discovery 2233 false, 2234 // Reference discovery is not atomic 2235 &_is_alive_closure_cm, 2236 // is alive closure 2237 // (for efficiency/performance) 2238 true); 2239 // Setting next fields of discovered 2240 // lists requires a barrier. 2241 2242 // STW ref processor 2243 _ref_processor_stw = 2244 new ReferenceProcessor(mr, // span 2245 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2246 // mt processing 2247 MAX2((int)ParallelGCThreads, 1), 2248 // degree of mt processing 2249 (ParallelGCThreads > 1), 2250 // mt discovery 2251 MAX2((int)ParallelGCThreads, 1), 2252 // degree of mt discovery 2253 true, 2254 // Reference discovery is atomic 2255 &_is_alive_closure_stw, 2256 // is alive closure 2257 // (for efficiency/performance) 2258 false); 2259 // Setting next fields of discovered 2260 // lists requires a barrier. 2261 } 2262 2263 size_t G1CollectedHeap::capacity() const { 2264 return _g1_committed.byte_size(); 2265 } 2266 2267 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2268 assert(!hr->continuesHumongous(), "pre-condition"); 2269 hr->reset_gc_time_stamp(); 2270 if (hr->startsHumongous()) { 2271 uint first_index = hr->hrs_index() + 1; 2272 uint last_index = hr->last_hc_index(); 2273 for (uint i = first_index; i < last_index; i += 1) { 2274 HeapRegion* chr = region_at(i); 2275 assert(chr->continuesHumongous(), "sanity"); 2276 chr->reset_gc_time_stamp(); 2277 } 2278 } 2279 } 2280 2281 #ifndef PRODUCT 2282 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2283 private: 2284 unsigned _gc_time_stamp; 2285 bool _failures; 2286 2287 public: 2288 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2289 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2290 2291 virtual bool doHeapRegion(HeapRegion* hr) { 2292 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2293 if (_gc_time_stamp != region_gc_time_stamp) { 2294 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2295 "expected %d", HR_FORMAT_PARAMS(hr), 2296 region_gc_time_stamp, _gc_time_stamp); 2297 _failures = true; 2298 } 2299 return false; 2300 } 2301 2302 bool failures() { return _failures; } 2303 }; 2304 2305 void G1CollectedHeap::check_gc_time_stamps() { 2306 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2307 heap_region_iterate(&cl); 2308 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2309 } 2310 #endif // PRODUCT 2311 2312 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2313 DirtyCardQueue* into_cset_dcq, 2314 bool concurrent, 2315 int worker_i) { 2316 // Clean cards in the hot card cache 2317 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq); 2318 2319 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2320 int n_completed_buffers = 0; 2321 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2322 n_completed_buffers++; 2323 } 2324 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2325 dcqs.clear_n_completed_buffers(); 2326 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2327 } 2328 2329 2330 // Computes the sum of the storage used by the various regions. 2331 2332 size_t G1CollectedHeap::used() const { 2333 assert(Heap_lock->owner() != NULL, 2334 "Should be owned on this thread's behalf."); 2335 size_t result = _summary_bytes_used; 2336 // Read only once in case it is set to NULL concurrently 2337 HeapRegion* hr = _mutator_alloc_region.get(); 2338 if (hr != NULL) 2339 result += hr->used(); 2340 return result; 2341 } 2342 2343 size_t G1CollectedHeap::used_unlocked() const { 2344 size_t result = _summary_bytes_used; 2345 return result; 2346 } 2347 2348 class SumUsedClosure: public HeapRegionClosure { 2349 size_t _used; 2350 public: 2351 SumUsedClosure() : _used(0) {} 2352 bool doHeapRegion(HeapRegion* r) { 2353 if (!r->continuesHumongous()) { 2354 _used += r->used(); 2355 } 2356 return false; 2357 } 2358 size_t result() { return _used; } 2359 }; 2360 2361 size_t G1CollectedHeap::recalculate_used() const { 2362 SumUsedClosure blk; 2363 heap_region_iterate(&blk); 2364 return blk.result(); 2365 } 2366 2367 size_t G1CollectedHeap::unsafe_max_alloc() { 2368 if (free_regions() > 0) return HeapRegion::GrainBytes; 2369 // otherwise, is there space in the current allocation region? 2370 2371 // We need to store the current allocation region in a local variable 2372 // here. The problem is that this method doesn't take any locks and 2373 // there may be other threads which overwrite the current allocation 2374 // region field. attempt_allocation(), for example, sets it to NULL 2375 // and this can happen *after* the NULL check here but before the call 2376 // to free(), resulting in a SIGSEGV. Note that this doesn't appear 2377 // to be a problem in the optimized build, since the two loads of the 2378 // current allocation region field are optimized away. 2379 HeapRegion* hr = _mutator_alloc_region.get(); 2380 if (hr == NULL) { 2381 return 0; 2382 } 2383 return hr->free(); 2384 } 2385 2386 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2387 switch (cause) { 2388 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2389 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2390 case GCCause::_g1_humongous_allocation: return true; 2391 default: return false; 2392 } 2393 } 2394 2395 #ifndef PRODUCT 2396 void G1CollectedHeap::allocate_dummy_regions() { 2397 // Let's fill up most of the region 2398 size_t word_size = HeapRegion::GrainWords - 1024; 2399 // And as a result the region we'll allocate will be humongous. 2400 guarantee(isHumongous(word_size), "sanity"); 2401 2402 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2403 // Let's use the existing mechanism for the allocation 2404 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2405 if (dummy_obj != NULL) { 2406 MemRegion mr(dummy_obj, word_size); 2407 CollectedHeap::fill_with_object(mr); 2408 } else { 2409 // If we can't allocate once, we probably cannot allocate 2410 // again. Let's get out of the loop. 2411 break; 2412 } 2413 } 2414 } 2415 #endif // !PRODUCT 2416 2417 void G1CollectedHeap::increment_old_marking_cycles_started() { 2418 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2419 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2420 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2421 _old_marking_cycles_started, _old_marking_cycles_completed)); 2422 2423 _old_marking_cycles_started++; 2424 } 2425 2426 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2427 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2428 2429 // We assume that if concurrent == true, then the caller is a 2430 // concurrent thread that was joined the Suspendible Thread 2431 // Set. If there's ever a cheap way to check this, we should add an 2432 // assert here. 2433 2434 // Given that this method is called at the end of a Full GC or of a 2435 // concurrent cycle, and those can be nested (i.e., a Full GC can 2436 // interrupt a concurrent cycle), the number of full collections 2437 // completed should be either one (in the case where there was no 2438 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2439 // behind the number of full collections started. 2440 2441 // This is the case for the inner caller, i.e. a Full GC. 2442 assert(concurrent || 2443 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2444 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2445 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2446 "is inconsistent with _old_marking_cycles_completed = %u", 2447 _old_marking_cycles_started, _old_marking_cycles_completed)); 2448 2449 // This is the case for the outer caller, i.e. the concurrent cycle. 2450 assert(!concurrent || 2451 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2452 err_msg("for outer caller (concurrent cycle): " 2453 "_old_marking_cycles_started = %u " 2454 "is inconsistent with _old_marking_cycles_completed = %u", 2455 _old_marking_cycles_started, _old_marking_cycles_completed)); 2456 2457 _old_marking_cycles_completed += 1; 2458 2459 // We need to clear the "in_progress" flag in the CM thread before 2460 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2461 // is set) so that if a waiter requests another System.gc() it doesn't 2462 // incorrectly see that a marking cyle is still in progress. 2463 if (concurrent) { 2464 _cmThread->clear_in_progress(); 2465 } 2466 2467 // This notify_all() will ensure that a thread that called 2468 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2469 // and it's waiting for a full GC to finish will be woken up. It is 2470 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2471 FullGCCount_lock->notify_all(); 2472 } 2473 2474 void G1CollectedHeap::collect(GCCause::Cause cause) { 2475 assert_heap_not_locked(); 2476 2477 unsigned int gc_count_before; 2478 unsigned int old_marking_count_before; 2479 bool retry_gc; 2480 2481 do { 2482 retry_gc = false; 2483 2484 { 2485 MutexLocker ml(Heap_lock); 2486 2487 // Read the GC count while holding the Heap_lock 2488 gc_count_before = total_collections(); 2489 old_marking_count_before = _old_marking_cycles_started; 2490 } 2491 2492 if (should_do_concurrent_full_gc(cause)) { 2493 // Schedule an initial-mark evacuation pause that will start a 2494 // concurrent cycle. We're setting word_size to 0 which means that 2495 // we are not requesting a post-GC allocation. 2496 VM_G1IncCollectionPause op(gc_count_before, 2497 0, /* word_size */ 2498 true, /* should_initiate_conc_mark */ 2499 g1_policy()->max_pause_time_ms(), 2500 cause); 2501 2502 VMThread::execute(&op); 2503 if (!op.pause_succeeded()) { 2504 if (old_marking_count_before == _old_marking_cycles_started) { 2505 retry_gc = op.should_retry_gc(); 2506 } else { 2507 // A Full GC happened while we were trying to schedule the 2508 // initial-mark GC. No point in starting a new cycle given 2509 // that the whole heap was collected anyway. 2510 } 2511 2512 if (retry_gc) { 2513 if (GC_locker::is_active_and_needs_gc()) { 2514 GC_locker::stall_until_clear(); 2515 } 2516 } 2517 } 2518 } else { 2519 if (cause == GCCause::_gc_locker 2520 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2521 2522 // Schedule a standard evacuation pause. We're setting word_size 2523 // to 0 which means that we are not requesting a post-GC allocation. 2524 VM_G1IncCollectionPause op(gc_count_before, 2525 0, /* word_size */ 2526 false, /* should_initiate_conc_mark */ 2527 g1_policy()->max_pause_time_ms(), 2528 cause); 2529 VMThread::execute(&op); 2530 } else { 2531 // Schedule a Full GC. 2532 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause); 2533 VMThread::execute(&op); 2534 } 2535 } 2536 } while (retry_gc); 2537 } 2538 2539 bool G1CollectedHeap::is_in(const void* p) const { 2540 if (_g1_committed.contains(p)) { 2541 // Given that we know that p is in the committed space, 2542 // heap_region_containing_raw() should successfully 2543 // return the containing region. 2544 HeapRegion* hr = heap_region_containing_raw(p); 2545 return hr->is_in(p); 2546 } else { 2547 return false; 2548 } 2549 } 2550 2551 // Iteration functions. 2552 2553 // Iterates an OopClosure over all ref-containing fields of objects 2554 // within a HeapRegion. 2555 2556 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2557 MemRegion _mr; 2558 ExtendedOopClosure* _cl; 2559 public: 2560 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl) 2561 : _mr(mr), _cl(cl) {} 2562 bool doHeapRegion(HeapRegion* r) { 2563 if (!r->continuesHumongous()) { 2564 r->oop_iterate(_cl); 2565 } 2566 return false; 2567 } 2568 }; 2569 2570 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2571 IterateOopClosureRegionClosure blk(_g1_committed, cl); 2572 heap_region_iterate(&blk); 2573 } 2574 2575 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { 2576 IterateOopClosureRegionClosure blk(mr, cl); 2577 heap_region_iterate(&blk); 2578 } 2579 2580 // Iterates an ObjectClosure over all objects within a HeapRegion. 2581 2582 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2583 ObjectClosure* _cl; 2584 public: 2585 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2586 bool doHeapRegion(HeapRegion* r) { 2587 if (! r->continuesHumongous()) { 2588 r->object_iterate(_cl); 2589 } 2590 return false; 2591 } 2592 }; 2593 2594 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2595 IterateObjectClosureRegionClosure blk(cl); 2596 heap_region_iterate(&blk); 2597 } 2598 2599 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) { 2600 // FIXME: is this right? 2601 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap"); 2602 } 2603 2604 // Calls a SpaceClosure on a HeapRegion. 2605 2606 class SpaceClosureRegionClosure: public HeapRegionClosure { 2607 SpaceClosure* _cl; 2608 public: 2609 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2610 bool doHeapRegion(HeapRegion* r) { 2611 _cl->do_space(r); 2612 return false; 2613 } 2614 }; 2615 2616 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2617 SpaceClosureRegionClosure blk(cl); 2618 heap_region_iterate(&blk); 2619 } 2620 2621 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2622 _hrs.iterate(cl); 2623 } 2624 2625 void 2626 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2627 uint worker_id, 2628 uint no_of_par_workers, 2629 jint claim_value) { 2630 const uint regions = n_regions(); 2631 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 2632 no_of_par_workers : 2633 1); 2634 assert(UseDynamicNumberOfGCThreads || 2635 no_of_par_workers == workers()->total_workers(), 2636 "Non dynamic should use fixed number of workers"); 2637 // try to spread out the starting points of the workers 2638 const HeapRegion* start_hr = 2639 start_region_for_worker(worker_id, no_of_par_workers); 2640 const uint start_index = start_hr->hrs_index(); 2641 2642 // each worker will actually look at all regions 2643 for (uint count = 0; count < regions; ++count) { 2644 const uint index = (start_index + count) % regions; 2645 assert(0 <= index && index < regions, "sanity"); 2646 HeapRegion* r = region_at(index); 2647 // we'll ignore "continues humongous" regions (we'll process them 2648 // when we come across their corresponding "start humongous" 2649 // region) and regions already claimed 2650 if (r->claim_value() == claim_value || r->continuesHumongous()) { 2651 continue; 2652 } 2653 // OK, try to claim it 2654 if (r->claimHeapRegion(claim_value)) { 2655 // success! 2656 assert(!r->continuesHumongous(), "sanity"); 2657 if (r->startsHumongous()) { 2658 // If the region is "starts humongous" we'll iterate over its 2659 // "continues humongous" first; in fact we'll do them 2660 // first. The order is important. In on case, calling the 2661 // closure on the "starts humongous" region might de-allocate 2662 // and clear all its "continues humongous" regions and, as a 2663 // result, we might end up processing them twice. So, we'll do 2664 // them first (notice: most closures will ignore them anyway) and 2665 // then we'll do the "starts humongous" region. 2666 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) { 2667 HeapRegion* chr = region_at(ch_index); 2668 2669 // if the region has already been claimed or it's not 2670 // "continues humongous" we're done 2671 if (chr->claim_value() == claim_value || 2672 !chr->continuesHumongous()) { 2673 break; 2674 } 2675 2676 // Noone should have claimed it directly. We can given 2677 // that we claimed its "starts humongous" region. 2678 assert(chr->claim_value() != claim_value, "sanity"); 2679 assert(chr->humongous_start_region() == r, "sanity"); 2680 2681 if (chr->claimHeapRegion(claim_value)) { 2682 // we should always be able to claim it; noone else should 2683 // be trying to claim this region 2684 2685 bool res2 = cl->doHeapRegion(chr); 2686 assert(!res2, "Should not abort"); 2687 2688 // Right now, this holds (i.e., no closure that actually 2689 // does something with "continues humongous" regions 2690 // clears them). We might have to weaken it in the future, 2691 // but let's leave these two asserts here for extra safety. 2692 assert(chr->continuesHumongous(), "should still be the case"); 2693 assert(chr->humongous_start_region() == r, "sanity"); 2694 } else { 2695 guarantee(false, "we should not reach here"); 2696 } 2697 } 2698 } 2699 2700 assert(!r->continuesHumongous(), "sanity"); 2701 bool res = cl->doHeapRegion(r); 2702 assert(!res, "Should not abort"); 2703 } 2704 } 2705 } 2706 2707 class ResetClaimValuesClosure: public HeapRegionClosure { 2708 public: 2709 bool doHeapRegion(HeapRegion* r) { 2710 r->set_claim_value(HeapRegion::InitialClaimValue); 2711 return false; 2712 } 2713 }; 2714 2715 void G1CollectedHeap::reset_heap_region_claim_values() { 2716 ResetClaimValuesClosure blk; 2717 heap_region_iterate(&blk); 2718 } 2719 2720 void G1CollectedHeap::reset_cset_heap_region_claim_values() { 2721 ResetClaimValuesClosure blk; 2722 collection_set_iterate(&blk); 2723 } 2724 2725 #ifdef ASSERT 2726 // This checks whether all regions in the heap have the correct claim 2727 // value. I also piggy-backed on this a check to ensure that the 2728 // humongous_start_region() information on "continues humongous" 2729 // regions is correct. 2730 2731 class CheckClaimValuesClosure : public HeapRegionClosure { 2732 private: 2733 jint _claim_value; 2734 uint _failures; 2735 HeapRegion* _sh_region; 2736 2737 public: 2738 CheckClaimValuesClosure(jint claim_value) : 2739 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2740 bool doHeapRegion(HeapRegion* r) { 2741 if (r->claim_value() != _claim_value) { 2742 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2743 "claim value = %d, should be %d", 2744 HR_FORMAT_PARAMS(r), 2745 r->claim_value(), _claim_value); 2746 ++_failures; 2747 } 2748 if (!r->isHumongous()) { 2749 _sh_region = NULL; 2750 } else if (r->startsHumongous()) { 2751 _sh_region = r; 2752 } else if (r->continuesHumongous()) { 2753 if (r->humongous_start_region() != _sh_region) { 2754 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2755 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2756 HR_FORMAT_PARAMS(r), 2757 r->humongous_start_region(), 2758 _sh_region); 2759 ++_failures; 2760 } 2761 } 2762 return false; 2763 } 2764 uint failures() { return _failures; } 2765 }; 2766 2767 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2768 CheckClaimValuesClosure cl(claim_value); 2769 heap_region_iterate(&cl); 2770 return cl.failures() == 0; 2771 } 2772 2773 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2774 private: 2775 jint _claim_value; 2776 uint _failures; 2777 2778 public: 2779 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2780 _claim_value(claim_value), _failures(0) { } 2781 2782 uint failures() { return _failures; } 2783 2784 bool doHeapRegion(HeapRegion* hr) { 2785 assert(hr->in_collection_set(), "how?"); 2786 assert(!hr->isHumongous(), "H-region in CSet"); 2787 if (hr->claim_value() != _claim_value) { 2788 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2789 "claim value = %d, should be %d", 2790 HR_FORMAT_PARAMS(hr), 2791 hr->claim_value(), _claim_value); 2792 _failures += 1; 2793 } 2794 return false; 2795 } 2796 }; 2797 2798 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2799 CheckClaimValuesInCSetHRClosure cl(claim_value); 2800 collection_set_iterate(&cl); 2801 return cl.failures() == 0; 2802 } 2803 #endif // ASSERT 2804 2805 // Clear the cached CSet starting regions and (more importantly) 2806 // the time stamps. Called when we reset the GC time stamp. 2807 void G1CollectedHeap::clear_cset_start_regions() { 2808 assert(_worker_cset_start_region != NULL, "sanity"); 2809 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2810 2811 int n_queues = MAX2((int)ParallelGCThreads, 1); 2812 for (int i = 0; i < n_queues; i++) { 2813 _worker_cset_start_region[i] = NULL; 2814 _worker_cset_start_region_time_stamp[i] = 0; 2815 } 2816 } 2817 2818 // Given the id of a worker, obtain or calculate a suitable 2819 // starting region for iterating over the current collection set. 2820 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) { 2821 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2822 2823 HeapRegion* result = NULL; 2824 unsigned gc_time_stamp = get_gc_time_stamp(); 2825 2826 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2827 // Cached starting region for current worker was set 2828 // during the current pause - so it's valid. 2829 // Note: the cached starting heap region may be NULL 2830 // (when the collection set is empty). 2831 result = _worker_cset_start_region[worker_i]; 2832 assert(result == NULL || result->in_collection_set(), "sanity"); 2833 return result; 2834 } 2835 2836 // The cached entry was not valid so let's calculate 2837 // a suitable starting heap region for this worker. 2838 2839 // We want the parallel threads to start their collection 2840 // set iteration at different collection set regions to 2841 // avoid contention. 2842 // If we have: 2843 // n collection set regions 2844 // p threads 2845 // Then thread t will start at region floor ((t * n) / p) 2846 2847 result = g1_policy()->collection_set(); 2848 if (G1CollectedHeap::use_parallel_gc_threads()) { 2849 uint cs_size = g1_policy()->cset_region_length(); 2850 uint active_workers = workers()->active_workers(); 2851 assert(UseDynamicNumberOfGCThreads || 2852 active_workers == workers()->total_workers(), 2853 "Unless dynamic should use total workers"); 2854 2855 uint end_ind = (cs_size * worker_i) / active_workers; 2856 uint start_ind = 0; 2857 2858 if (worker_i > 0 && 2859 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2860 // Previous workers starting region is valid 2861 // so let's iterate from there 2862 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2863 result = _worker_cset_start_region[worker_i - 1]; 2864 } 2865 2866 for (uint i = start_ind; i < end_ind; i++) { 2867 result = result->next_in_collection_set(); 2868 } 2869 } 2870 2871 // Note: the calculated starting heap region may be NULL 2872 // (when the collection set is empty). 2873 assert(result == NULL || result->in_collection_set(), "sanity"); 2874 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2875 "should be updated only once per pause"); 2876 _worker_cset_start_region[worker_i] = result; 2877 OrderAccess::storestore(); 2878 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2879 return result; 2880 } 2881 2882 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i, 2883 uint no_of_par_workers) { 2884 uint worker_num = 2885 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U; 2886 assert(UseDynamicNumberOfGCThreads || 2887 no_of_par_workers == workers()->total_workers(), 2888 "Non dynamic should use fixed number of workers"); 2889 const uint start_index = n_regions() * worker_i / worker_num; 2890 return region_at(start_index); 2891 } 2892 2893 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2894 HeapRegion* r = g1_policy()->collection_set(); 2895 while (r != NULL) { 2896 HeapRegion* next = r->next_in_collection_set(); 2897 if (cl->doHeapRegion(r)) { 2898 cl->incomplete(); 2899 return; 2900 } 2901 r = next; 2902 } 2903 } 2904 2905 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2906 HeapRegionClosure *cl) { 2907 if (r == NULL) { 2908 // The CSet is empty so there's nothing to do. 2909 return; 2910 } 2911 2912 assert(r->in_collection_set(), 2913 "Start region must be a member of the collection set."); 2914 HeapRegion* cur = r; 2915 while (cur != NULL) { 2916 HeapRegion* next = cur->next_in_collection_set(); 2917 if (cl->doHeapRegion(cur) && false) { 2918 cl->incomplete(); 2919 return; 2920 } 2921 cur = next; 2922 } 2923 cur = g1_policy()->collection_set(); 2924 while (cur != r) { 2925 HeapRegion* next = cur->next_in_collection_set(); 2926 if (cl->doHeapRegion(cur) && false) { 2927 cl->incomplete(); 2928 return; 2929 } 2930 cur = next; 2931 } 2932 } 2933 2934 CompactibleSpace* G1CollectedHeap::first_compactible_space() { 2935 return n_regions() > 0 ? region_at(0) : NULL; 2936 } 2937 2938 2939 Space* G1CollectedHeap::space_containing(const void* addr) const { 2940 Space* res = heap_region_containing(addr); 2941 return res; 2942 } 2943 2944 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2945 Space* sp = space_containing(addr); 2946 if (sp != NULL) { 2947 return sp->block_start(addr); 2948 } 2949 return NULL; 2950 } 2951 2952 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2953 Space* sp = space_containing(addr); 2954 assert(sp != NULL, "block_size of address outside of heap"); 2955 return sp->block_size(addr); 2956 } 2957 2958 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2959 Space* sp = space_containing(addr); 2960 return sp->block_is_obj(addr); 2961 } 2962 2963 bool G1CollectedHeap::supports_tlab_allocation() const { 2964 return true; 2965 } 2966 2967 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2968 return HeapRegion::GrainBytes; 2969 } 2970 2971 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2972 // Return the remaining space in the cur alloc region, but not less than 2973 // the min TLAB size. 2974 2975 // Also, this value can be at most the humongous object threshold, 2976 // since we can't allow tlabs to grow big enough to accomodate 2977 // humongous objects. 2978 2979 HeapRegion* hr = _mutator_alloc_region.get(); 2980 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize; 2981 if (hr == NULL) { 2982 return max_tlab_size; 2983 } else { 2984 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size); 2985 } 2986 } 2987 2988 size_t G1CollectedHeap::max_capacity() const { 2989 return _g1_reserved.byte_size(); 2990 } 2991 2992 jlong G1CollectedHeap::millis_since_last_gc() { 2993 // assert(false, "NYI"); 2994 return 0; 2995 } 2996 2997 void G1CollectedHeap::prepare_for_verify() { 2998 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2999 ensure_parsability(false); 3000 } 3001 g1_rem_set()->prepare_for_verify(); 3002 } 3003 3004 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 3005 VerifyOption vo) { 3006 switch (vo) { 3007 case VerifyOption_G1UsePrevMarking: 3008 return hr->obj_allocated_since_prev_marking(obj); 3009 case VerifyOption_G1UseNextMarking: 3010 return hr->obj_allocated_since_next_marking(obj); 3011 case VerifyOption_G1UseMarkWord: 3012 return false; 3013 default: 3014 ShouldNotReachHere(); 3015 } 3016 return false; // keep some compilers happy 3017 } 3018 3019 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 3020 switch (vo) { 3021 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 3022 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 3023 case VerifyOption_G1UseMarkWord: return NULL; 3024 default: ShouldNotReachHere(); 3025 } 3026 return NULL; // keep some compilers happy 3027 } 3028 3029 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 3030 switch (vo) { 3031 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 3032 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 3033 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 3034 default: ShouldNotReachHere(); 3035 } 3036 return false; // keep some compilers happy 3037 } 3038 3039 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 3040 switch (vo) { 3041 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 3042 case VerifyOption_G1UseNextMarking: return "NTAMS"; 3043 case VerifyOption_G1UseMarkWord: return "NONE"; 3044 default: ShouldNotReachHere(); 3045 } 3046 return NULL; // keep some compilers happy 3047 } 3048 3049 class VerifyLivenessOopClosure: public OopClosure { 3050 G1CollectedHeap* _g1h; 3051 VerifyOption _vo; 3052 public: 3053 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3054 _g1h(g1h), _vo(vo) 3055 { } 3056 void do_oop(narrowOop *p) { do_oop_work(p); } 3057 void do_oop( oop *p) { do_oop_work(p); } 3058 3059 template <class T> void do_oop_work(T *p) { 3060 oop obj = oopDesc::load_decode_heap_oop(p); 3061 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3062 "Dead object referenced by a not dead object"); 3063 } 3064 }; 3065 3066 class VerifyObjsInRegionClosure: public ObjectClosure { 3067 private: 3068 G1CollectedHeap* _g1h; 3069 size_t _live_bytes; 3070 HeapRegion *_hr; 3071 VerifyOption _vo; 3072 public: 3073 // _vo == UsePrevMarking -> use "prev" marking information, 3074 // _vo == UseNextMarking -> use "next" marking information, 3075 // _vo == UseMarkWord -> use mark word from object header. 3076 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3077 : _live_bytes(0), _hr(hr), _vo(vo) { 3078 _g1h = G1CollectedHeap::heap(); 3079 } 3080 void do_object(oop o) { 3081 VerifyLivenessOopClosure isLive(_g1h, _vo); 3082 assert(o != NULL, "Huh?"); 3083 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3084 // If the object is alive according to the mark word, 3085 // then verify that the marking information agrees. 3086 // Note we can't verify the contra-positive of the 3087 // above: if the object is dead (according to the mark 3088 // word), it may not be marked, or may have been marked 3089 // but has since became dead, or may have been allocated 3090 // since the last marking. 3091 if (_vo == VerifyOption_G1UseMarkWord) { 3092 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3093 } 3094 3095 o->oop_iterate_no_header(&isLive); 3096 if (!_hr->obj_allocated_since_prev_marking(o)) { 3097 size_t obj_size = o->size(); // Make sure we don't overflow 3098 _live_bytes += (obj_size * HeapWordSize); 3099 } 3100 } 3101 } 3102 size_t live_bytes() { return _live_bytes; } 3103 }; 3104 3105 class PrintObjsInRegionClosure : public ObjectClosure { 3106 HeapRegion *_hr; 3107 G1CollectedHeap *_g1; 3108 public: 3109 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3110 _g1 = G1CollectedHeap::heap(); 3111 }; 3112 3113 void do_object(oop o) { 3114 if (o != NULL) { 3115 HeapWord *start = (HeapWord *) o; 3116 size_t word_sz = o->size(); 3117 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3118 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3119 (void*) o, word_sz, 3120 _g1->isMarkedPrev(o), 3121 _g1->isMarkedNext(o), 3122 _hr->obj_allocated_since_prev_marking(o)); 3123 HeapWord *end = start + word_sz; 3124 HeapWord *cur; 3125 int *val; 3126 for (cur = start; cur < end; cur++) { 3127 val = (int *) cur; 3128 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 3129 } 3130 } 3131 } 3132 }; 3133 3134 class VerifyRegionClosure: public HeapRegionClosure { 3135 private: 3136 bool _par; 3137 VerifyOption _vo; 3138 bool _failures; 3139 public: 3140 // _vo == UsePrevMarking -> use "prev" marking information, 3141 // _vo == UseNextMarking -> use "next" marking information, 3142 // _vo == UseMarkWord -> use mark word from object header. 3143 VerifyRegionClosure(bool par, VerifyOption vo) 3144 : _par(par), 3145 _vo(vo), 3146 _failures(false) {} 3147 3148 bool failures() { 3149 return _failures; 3150 } 3151 3152 bool doHeapRegion(HeapRegion* r) { 3153 if (!r->continuesHumongous()) { 3154 bool failures = false; 3155 r->verify(_vo, &failures); 3156 if (failures) { 3157 _failures = true; 3158 } else { 3159 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3160 r->object_iterate(¬_dead_yet_cl); 3161 if (_vo != VerifyOption_G1UseNextMarking) { 3162 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3163 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3164 "max_live_bytes "SIZE_FORMAT" " 3165 "< calculated "SIZE_FORMAT, 3166 r->bottom(), r->end(), 3167 r->max_live_bytes(), 3168 not_dead_yet_cl.live_bytes()); 3169 _failures = true; 3170 } 3171 } else { 3172 // When vo == UseNextMarking we cannot currently do a sanity 3173 // check on the live bytes as the calculation has not been 3174 // finalized yet. 3175 } 3176 } 3177 } 3178 return false; // stop the region iteration if we hit a failure 3179 } 3180 }; 3181 3182 class YoungRefCounterClosure : public OopClosure { 3183 G1CollectedHeap* _g1h; 3184 int _count; 3185 public: 3186 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 3187 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 3188 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 3189 3190 int count() { return _count; } 3191 void reset_count() { _count = 0; }; 3192 }; 3193 3194 class VerifyKlassClosure: public KlassClosure { 3195 YoungRefCounterClosure _young_ref_counter_closure; 3196 OopClosure *_oop_closure; 3197 public: 3198 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3199 void do_klass(Klass* k) { 3200 k->oops_do(_oop_closure); 3201 3202 _young_ref_counter_closure.reset_count(); 3203 k->oops_do(&_young_ref_counter_closure); 3204 if (_young_ref_counter_closure.count() > 0) { 3205 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); 3206 } 3207 } 3208 }; 3209 3210 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can 3211 // pass it as the perm_blk to SharedHeap::process_strong_roots. 3212 // When process_strong_roots stop calling perm_blk->younger_refs_iterate 3213 // we can change this closure to extend the simpler OopClosure. 3214 class VerifyRootsClosure: public OopsInGenClosure { 3215 private: 3216 G1CollectedHeap* _g1h; 3217 VerifyOption _vo; 3218 bool _failures; 3219 public: 3220 // _vo == UsePrevMarking -> use "prev" marking information, 3221 // _vo == UseNextMarking -> use "next" marking information, 3222 // _vo == UseMarkWord -> use mark word from object header. 3223 VerifyRootsClosure(VerifyOption vo) : 3224 _g1h(G1CollectedHeap::heap()), 3225 _vo(vo), 3226 _failures(false) { } 3227 3228 bool failures() { return _failures; } 3229 3230 template <class T> void do_oop_nv(T* p) { 3231 T heap_oop = oopDesc::load_heap_oop(p); 3232 if (!oopDesc::is_null(heap_oop)) { 3233 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3234 if (_g1h->is_obj_dead_cond(obj, _vo)) { 3235 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 3236 "points to dead obj "PTR_FORMAT, p, (void*) obj); 3237 if (_vo == VerifyOption_G1UseMarkWord) { 3238 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 3239 } 3240 obj->print_on(gclog_or_tty); 3241 _failures = true; 3242 } 3243 } 3244 } 3245 3246 void do_oop(oop* p) { do_oop_nv(p); } 3247 void do_oop(narrowOop* p) { do_oop_nv(p); } 3248 }; 3249 3250 // This is the task used for parallel heap verification. 3251 3252 class G1ParVerifyTask: public AbstractGangTask { 3253 private: 3254 G1CollectedHeap* _g1h; 3255 VerifyOption _vo; 3256 bool _failures; 3257 3258 public: 3259 // _vo == UsePrevMarking -> use "prev" marking information, 3260 // _vo == UseNextMarking -> use "next" marking information, 3261 // _vo == UseMarkWord -> use mark word from object header. 3262 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3263 AbstractGangTask("Parallel verify task"), 3264 _g1h(g1h), 3265 _vo(vo), 3266 _failures(false) { } 3267 3268 bool failures() { 3269 return _failures; 3270 } 3271 3272 void work(uint worker_id) { 3273 HandleMark hm; 3274 VerifyRegionClosure blk(true, _vo); 3275 _g1h->heap_region_par_iterate_chunked(&blk, worker_id, 3276 _g1h->workers()->active_workers(), 3277 HeapRegion::ParVerifyClaimValue); 3278 if (blk.failures()) { 3279 _failures = true; 3280 } 3281 } 3282 }; 3283 3284 void G1CollectedHeap::verify(bool silent) { 3285 verify(silent, VerifyOption_G1UsePrevMarking); 3286 } 3287 3288 void G1CollectedHeap::verify(bool silent, 3289 VerifyOption vo) { 3290 if (SafepointSynchronize::is_at_safepoint()) { 3291 if (!silent) { gclog_or_tty->print("Roots "); } 3292 VerifyRootsClosure rootsCl(vo); 3293 3294 assert(Thread::current()->is_VM_thread(), 3295 "Expected to be executed serially by the VM thread at this point"); 3296 3297 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false); 3298 VerifyKlassClosure klassCl(this, &rootsCl); 3299 3300 // We apply the relevant closures to all the oops in the 3301 // system dictionary, the string table and the code cache. 3302 const int so = SO_AllClasses | SO_Strings | SO_CodeCache; 3303 3304 // Need cleared claim bits for the strong roots processing 3305 ClassLoaderDataGraph::clear_claimed_marks(); 3306 3307 process_strong_roots(true, // activate StrongRootsScope 3308 false, // we set "is scavenging" to false, 3309 // so we don't reset the dirty cards. 3310 ScanningOption(so), // roots scanning options 3311 &rootsCl, 3312 &blobsCl, 3313 &klassCl 3314 ); 3315 3316 bool failures = rootsCl.failures(); 3317 3318 if (vo != VerifyOption_G1UseMarkWord) { 3319 // If we're verifying during a full GC then the region sets 3320 // will have been torn down at the start of the GC. Therefore 3321 // verifying the region sets will fail. So we only verify 3322 // the region sets when not in a full GC. 3323 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3324 verify_region_sets(); 3325 } 3326 3327 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3328 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3329 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3330 "sanity check"); 3331 3332 G1ParVerifyTask task(this, vo); 3333 assert(UseDynamicNumberOfGCThreads || 3334 workers()->active_workers() == workers()->total_workers(), 3335 "If not dynamic should be using all the workers"); 3336 int n_workers = workers()->active_workers(); 3337 set_par_threads(n_workers); 3338 workers()->run_task(&task); 3339 set_par_threads(0); 3340 if (task.failures()) { 3341 failures = true; 3342 } 3343 3344 // Checks that the expected amount of parallel work was done. 3345 // The implication is that n_workers is > 0. 3346 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3347 "sanity check"); 3348 3349 reset_heap_region_claim_values(); 3350 3351 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3352 "sanity check"); 3353 } else { 3354 VerifyRegionClosure blk(false, vo); 3355 heap_region_iterate(&blk); 3356 if (blk.failures()) { 3357 failures = true; 3358 } 3359 } 3360 if (!silent) gclog_or_tty->print("RemSet "); 3361 rem_set()->verify(); 3362 3363 if (failures) { 3364 gclog_or_tty->print_cr("Heap:"); 3365 // It helps to have the per-region information in the output to 3366 // help us track down what went wrong. This is why we call 3367 // print_extended_on() instead of print_on(). 3368 print_extended_on(gclog_or_tty); 3369 gclog_or_tty->print_cr(""); 3370 #ifndef PRODUCT 3371 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3372 concurrent_mark()->print_reachable("at-verification-failure", 3373 vo, false /* all */); 3374 } 3375 #endif 3376 gclog_or_tty->flush(); 3377 } 3378 guarantee(!failures, "there should not have been any failures"); 3379 } else { 3380 if (!silent) 3381 gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) "); 3382 } 3383 } 3384 3385 class PrintRegionClosure: public HeapRegionClosure { 3386 outputStream* _st; 3387 public: 3388 PrintRegionClosure(outputStream* st) : _st(st) {} 3389 bool doHeapRegion(HeapRegion* r) { 3390 r->print_on(_st); 3391 return false; 3392 } 3393 }; 3394 3395 void G1CollectedHeap::print_on(outputStream* st) const { 3396 st->print(" %-20s", "garbage-first heap"); 3397 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3398 capacity()/K, used_unlocked()/K); 3399 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3400 _g1_storage.low_boundary(), 3401 _g1_storage.high(), 3402 _g1_storage.high_boundary()); 3403 st->cr(); 3404 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3405 uint young_regions = _young_list->length(); 3406 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3407 (size_t) young_regions * HeapRegion::GrainBytes / K); 3408 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3409 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3410 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3411 st->cr(); 3412 MetaspaceAux::print_on(st); 3413 } 3414 3415 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3416 print_on(st); 3417 3418 // Print the per-region information. 3419 st->cr(); 3420 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3421 "HS=humongous(starts), HC=humongous(continues), " 3422 "CS=collection set, F=free, TS=gc time stamp, " 3423 "PTAMS=previous top-at-mark-start, " 3424 "NTAMS=next top-at-mark-start)"); 3425 PrintRegionClosure blk(st); 3426 heap_region_iterate(&blk); 3427 } 3428 3429 void G1CollectedHeap::print_on_error(outputStream* st) const { 3430 this->CollectedHeap::print_on_error(st); 3431 3432 if (_cm != NULL) { 3433 st->cr(); 3434 _cm->print_on_error(st); 3435 } 3436 } 3437 3438 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3439 if (G1CollectedHeap::use_parallel_gc_threads()) { 3440 workers()->print_worker_threads_on(st); 3441 } 3442 _cmThread->print_on(st); 3443 st->cr(); 3444 _cm->print_worker_threads_on(st); 3445 _cg1r->print_worker_threads_on(st); 3446 } 3447 3448 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3449 if (G1CollectedHeap::use_parallel_gc_threads()) { 3450 workers()->threads_do(tc); 3451 } 3452 tc->do_thread(_cmThread); 3453 _cg1r->threads_do(tc); 3454 } 3455 3456 void G1CollectedHeap::print_tracing_info() const { 3457 // We'll overload this to mean "trace GC pause statistics." 3458 if (TraceGen0Time || TraceGen1Time) { 3459 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3460 // to that. 3461 g1_policy()->print_tracing_info(); 3462 } 3463 if (G1SummarizeRSetStats) { 3464 g1_rem_set()->print_summary_info(); 3465 } 3466 if (G1SummarizeConcMark) { 3467 concurrent_mark()->print_summary_info(); 3468 } 3469 g1_policy()->print_yg_surv_rate_info(); 3470 SpecializationStats::print(); 3471 } 3472 3473 #ifndef PRODUCT 3474 // Helpful for debugging RSet issues. 3475 3476 class PrintRSetsClosure : public HeapRegionClosure { 3477 private: 3478 const char* _msg; 3479 size_t _occupied_sum; 3480 3481 public: 3482 bool doHeapRegion(HeapRegion* r) { 3483 HeapRegionRemSet* hrrs = r->rem_set(); 3484 size_t occupied = hrrs->occupied(); 3485 _occupied_sum += occupied; 3486 3487 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3488 HR_FORMAT_PARAMS(r)); 3489 if (occupied == 0) { 3490 gclog_or_tty->print_cr(" RSet is empty"); 3491 } else { 3492 hrrs->print(); 3493 } 3494 gclog_or_tty->print_cr("----------"); 3495 return false; 3496 } 3497 3498 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3499 gclog_or_tty->cr(); 3500 gclog_or_tty->print_cr("========================================"); 3501 gclog_or_tty->print_cr(msg); 3502 gclog_or_tty->cr(); 3503 } 3504 3505 ~PrintRSetsClosure() { 3506 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3507 gclog_or_tty->print_cr("========================================"); 3508 gclog_or_tty->cr(); 3509 } 3510 }; 3511 3512 void G1CollectedHeap::print_cset_rsets() { 3513 PrintRSetsClosure cl("Printing CSet RSets"); 3514 collection_set_iterate(&cl); 3515 } 3516 3517 void G1CollectedHeap::print_all_rsets() { 3518 PrintRSetsClosure cl("Printing All RSets");; 3519 heap_region_iterate(&cl); 3520 } 3521 #endif // PRODUCT 3522 3523 G1CollectedHeap* G1CollectedHeap::heap() { 3524 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3525 "not a garbage-first heap"); 3526 return _g1h; 3527 } 3528 3529 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3530 // always_do_update_barrier = false; 3531 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3532 // Call allocation profiler 3533 AllocationProfiler::iterate_since_last_gc(); 3534 // Fill TLAB's and such 3535 ensure_parsability(true); 3536 } 3537 3538 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { 3539 // FIXME: what is this about? 3540 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3541 // is set. 3542 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3543 "derived pointer present")); 3544 // always_do_update_barrier = true; 3545 3546 // We have just completed a GC. Update the soft reference 3547 // policy with the new heap occupancy 3548 Universe::update_heap_info_at_gc(); 3549 } 3550 3551 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3552 unsigned int gc_count_before, 3553 bool* succeeded) { 3554 assert_heap_not_locked_and_not_at_safepoint(); 3555 g1_policy()->record_stop_world_start(); 3556 VM_G1IncCollectionPause op(gc_count_before, 3557 word_size, 3558 false, /* should_initiate_conc_mark */ 3559 g1_policy()->max_pause_time_ms(), 3560 GCCause::_g1_inc_collection_pause); 3561 VMThread::execute(&op); 3562 3563 HeapWord* result = op.result(); 3564 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3565 assert(result == NULL || ret_succeeded, 3566 "the result should be NULL if the VM did not succeed"); 3567 *succeeded = ret_succeeded; 3568 3569 assert_heap_not_locked(); 3570 return result; 3571 } 3572 3573 void 3574 G1CollectedHeap::doConcurrentMark() { 3575 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3576 if (!_cmThread->in_progress()) { 3577 _cmThread->set_started(); 3578 CGC_lock->notify(); 3579 } 3580 } 3581 3582 size_t G1CollectedHeap::pending_card_num() { 3583 size_t extra_cards = 0; 3584 JavaThread *curr = Threads::first(); 3585 while (curr != NULL) { 3586 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3587 extra_cards += dcq.size(); 3588 curr = curr->next(); 3589 } 3590 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3591 size_t buffer_size = dcqs.buffer_size(); 3592 size_t buffer_num = dcqs.completed_buffers_num(); 3593 3594 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3595 // in bytes - not the number of 'entries'. We need to convert 3596 // into a number of cards. 3597 return (buffer_size * buffer_num + extra_cards) / oopSize; 3598 } 3599 3600 size_t G1CollectedHeap::cards_scanned() { 3601 return g1_rem_set()->cardsScanned(); 3602 } 3603 3604 void 3605 G1CollectedHeap::setup_surviving_young_words() { 3606 assert(_surviving_young_words == NULL, "pre-condition"); 3607 uint array_length = g1_policy()->young_cset_region_length(); 3608 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3609 if (_surviving_young_words == NULL) { 3610 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3611 "Not enough space for young surv words summary."); 3612 } 3613 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3614 #ifdef ASSERT 3615 for (uint i = 0; i < array_length; ++i) { 3616 assert( _surviving_young_words[i] == 0, "memset above" ); 3617 } 3618 #endif // !ASSERT 3619 } 3620 3621 void 3622 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3623 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3624 uint array_length = g1_policy()->young_cset_region_length(); 3625 for (uint i = 0; i < array_length; ++i) { 3626 _surviving_young_words[i] += surv_young_words[i]; 3627 } 3628 } 3629 3630 void 3631 G1CollectedHeap::cleanup_surviving_young_words() { 3632 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3633 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3634 _surviving_young_words = NULL; 3635 } 3636 3637 #ifdef ASSERT 3638 class VerifyCSetClosure: public HeapRegionClosure { 3639 public: 3640 bool doHeapRegion(HeapRegion* hr) { 3641 // Here we check that the CSet region's RSet is ready for parallel 3642 // iteration. The fields that we'll verify are only manipulated 3643 // when the region is part of a CSet and is collected. Afterwards, 3644 // we reset these fields when we clear the region's RSet (when the 3645 // region is freed) so they are ready when the region is 3646 // re-allocated. The only exception to this is if there's an 3647 // evacuation failure and instead of freeing the region we leave 3648 // it in the heap. In that case, we reset these fields during 3649 // evacuation failure handling. 3650 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3651 3652 // Here's a good place to add any other checks we'd like to 3653 // perform on CSet regions. 3654 return false; 3655 } 3656 }; 3657 #endif // ASSERT 3658 3659 #if TASKQUEUE_STATS 3660 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3661 st->print_raw_cr("GC Task Stats"); 3662 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3663 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3664 } 3665 3666 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3667 print_taskqueue_stats_hdr(st); 3668 3669 TaskQueueStats totals; 3670 const int n = workers() != NULL ? workers()->total_workers() : 1; 3671 for (int i = 0; i < n; ++i) { 3672 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3673 totals += task_queue(i)->stats; 3674 } 3675 st->print_raw("tot "); totals.print(st); st->cr(); 3676 3677 DEBUG_ONLY(totals.verify()); 3678 } 3679 3680 void G1CollectedHeap::reset_taskqueue_stats() { 3681 const int n = workers() != NULL ? workers()->total_workers() : 1; 3682 for (int i = 0; i < n; ++i) { 3683 task_queue(i)->stats.reset(); 3684 } 3685 } 3686 #endif // TASKQUEUE_STATS 3687 3688 void G1CollectedHeap::log_gc_header() { 3689 if (!G1Log::fine()) { 3690 return; 3691 } 3692 3693 gclog_or_tty->date_stamp(PrintGCDateStamps); 3694 gclog_or_tty->stamp(PrintGCTimeStamps); 3695 3696 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3697 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3698 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3699 3700 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3701 } 3702 3703 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3704 if (!G1Log::fine()) { 3705 return; 3706 } 3707 3708 if (G1Log::finer()) { 3709 if (evacuation_failed()) { 3710 gclog_or_tty->print(" (to-space exhausted)"); 3711 } 3712 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3713 g1_policy()->phase_times()->note_gc_end(); 3714 g1_policy()->phase_times()->print(pause_time_sec); 3715 g1_policy()->print_detailed_heap_transition(); 3716 } else { 3717 if (evacuation_failed()) { 3718 gclog_or_tty->print("--"); 3719 } 3720 g1_policy()->print_heap_transition(); 3721 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3722 } 3723 gclog_or_tty->flush(); 3724 } 3725 3726 bool 3727 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3728 assert_at_safepoint(true /* should_be_vm_thread */); 3729 guarantee(!is_gc_active(), "collection is not reentrant"); 3730 3731 if (GC_locker::check_active_before_gc()) { 3732 return false; 3733 } 3734 3735 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3736 ResourceMark rm; 3737 3738 print_heap_before_gc(); 3739 3740 HRSPhaseSetter x(HRSPhaseEvacuation); 3741 verify_region_sets_optional(); 3742 verify_dirty_young_regions(); 3743 3744 // This call will decide whether this pause is an initial-mark 3745 // pause. If it is, during_initial_mark_pause() will return true 3746 // for the duration of this pause. 3747 g1_policy()->decide_on_conc_mark_initiation(); 3748 3749 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3750 assert(!g1_policy()->during_initial_mark_pause() || 3751 g1_policy()->gcs_are_young(), "sanity"); 3752 3753 // We also do not allow mixed GCs during marking. 3754 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3755 3756 // Record whether this pause is an initial mark. When the current 3757 // thread has completed its logging output and it's safe to signal 3758 // the CM thread, the flag's value in the policy has been reset. 3759 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3760 3761 // Inner scope for scope based logging, timers, and stats collection 3762 { 3763 if (g1_policy()->during_initial_mark_pause()) { 3764 // We are about to start a marking cycle, so we increment the 3765 // full collection counter. 3766 increment_old_marking_cycles_started(); 3767 } 3768 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3769 3770 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3771 workers()->active_workers() : 1); 3772 double pause_start_sec = os::elapsedTime(); 3773 g1_policy()->phase_times()->note_gc_start(active_workers); 3774 log_gc_header(); 3775 3776 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3777 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3778 3779 // If the secondary_free_list is not empty, append it to the 3780 // free_list. No need to wait for the cleanup operation to finish; 3781 // the region allocation code will check the secondary_free_list 3782 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3783 // set, skip this step so that the region allocation code has to 3784 // get entries from the secondary_free_list. 3785 if (!G1StressConcRegionFreeing) { 3786 append_secondary_free_list_if_not_empty_with_lock(); 3787 } 3788 3789 assert(check_young_list_well_formed(), 3790 "young list should be well formed"); 3791 3792 // Don't dynamically change the number of GC threads this early. A value of 3793 // 0 is used to indicate serial work. When parallel work is done, 3794 // it will be set. 3795 3796 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3797 IsGCActiveMark x; 3798 3799 gc_prologue(false); 3800 increment_total_collections(false /* full gc */); 3801 increment_gc_time_stamp(); 3802 3803 verify_before_gc(); 3804 3805 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3806 3807 // Please see comment in g1CollectedHeap.hpp and 3808 // G1CollectedHeap::ref_processing_init() to see how 3809 // reference processing currently works in G1. 3810 3811 // Enable discovery in the STW reference processor 3812 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 3813 true /*verify_no_refs*/); 3814 3815 { 3816 // We want to temporarily turn off discovery by the 3817 // CM ref processor, if necessary, and turn it back on 3818 // on again later if we do. Using a scoped 3819 // NoRefDiscovery object will do this. 3820 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3821 3822 // Forget the current alloc region (we might even choose it to be part 3823 // of the collection set!). 3824 release_mutator_alloc_region(); 3825 3826 // We should call this after we retire the mutator alloc 3827 // region(s) so that all the ALLOC / RETIRE events are generated 3828 // before the start GC event. 3829 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3830 3831 // This timing is only used by the ergonomics to handle our pause target. 3832 // It is unclear why this should not include the full pause. We will 3833 // investigate this in CR 7178365. 3834 // 3835 // Preserving the old comment here if that helps the investigation: 3836 // 3837 // The elapsed time induced by the start time below deliberately elides 3838 // the possible verification above. 3839 double sample_start_time_sec = os::elapsedTime(); 3840 3841 #if YOUNG_LIST_VERBOSE 3842 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3843 _young_list->print(); 3844 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3845 #endif // YOUNG_LIST_VERBOSE 3846 3847 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3848 3849 double scan_wait_start = os::elapsedTime(); 3850 // We have to wait until the CM threads finish scanning the 3851 // root regions as it's the only way to ensure that all the 3852 // objects on them have been correctly scanned before we start 3853 // moving them during the GC. 3854 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3855 double wait_time_ms = 0.0; 3856 if (waited) { 3857 double scan_wait_end = os::elapsedTime(); 3858 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3859 } 3860 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3861 3862 #if YOUNG_LIST_VERBOSE 3863 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3864 _young_list->print(); 3865 #endif // YOUNG_LIST_VERBOSE 3866 3867 if (g1_policy()->during_initial_mark_pause()) { 3868 concurrent_mark()->checkpointRootsInitialPre(); 3869 } 3870 3871 #if YOUNG_LIST_VERBOSE 3872 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3873 _young_list->print(); 3874 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3875 #endif // YOUNG_LIST_VERBOSE 3876 3877 g1_policy()->finalize_cset(target_pause_time_ms); 3878 3879 _cm->note_start_of_gc(); 3880 // We should not verify the per-thread SATB buffers given that 3881 // we have not filtered them yet (we'll do so during the 3882 // GC). We also call this after finalize_cset() to 3883 // ensure that the CSet has been finalized. 3884 _cm->verify_no_cset_oops(true /* verify_stacks */, 3885 true /* verify_enqueued_buffers */, 3886 false /* verify_thread_buffers */, 3887 true /* verify_fingers */); 3888 3889 if (_hr_printer.is_active()) { 3890 HeapRegion* hr = g1_policy()->collection_set(); 3891 while (hr != NULL) { 3892 G1HRPrinter::RegionType type; 3893 if (!hr->is_young()) { 3894 type = G1HRPrinter::Old; 3895 } else if (hr->is_survivor()) { 3896 type = G1HRPrinter::Survivor; 3897 } else { 3898 type = G1HRPrinter::Eden; 3899 } 3900 _hr_printer.cset(hr); 3901 hr = hr->next_in_collection_set(); 3902 } 3903 } 3904 3905 #ifdef ASSERT 3906 VerifyCSetClosure cl; 3907 collection_set_iterate(&cl); 3908 #endif // ASSERT 3909 3910 setup_surviving_young_words(); 3911 3912 // Initialize the GC alloc regions. 3913 init_gc_alloc_regions(); 3914 3915 // Actually do the work... 3916 evacuate_collection_set(); 3917 3918 // We do this to mainly verify the per-thread SATB buffers 3919 // (which have been filtered by now) since we didn't verify 3920 // them earlier. No point in re-checking the stacks / enqueued 3921 // buffers given that the CSet has not changed since last time 3922 // we checked. 3923 _cm->verify_no_cset_oops(false /* verify_stacks */, 3924 false /* verify_enqueued_buffers */, 3925 true /* verify_thread_buffers */, 3926 true /* verify_fingers */); 3927 3928 free_collection_set(g1_policy()->collection_set()); 3929 g1_policy()->clear_collection_set(); 3930 3931 cleanup_surviving_young_words(); 3932 3933 // Start a new incremental collection set for the next pause. 3934 g1_policy()->start_incremental_cset_building(); 3935 3936 // Clear the _cset_fast_test bitmap in anticipation of adding 3937 // regions to the incremental collection set for the next 3938 // evacuation pause. 3939 clear_cset_fast_test(); 3940 3941 _young_list->reset_sampled_info(); 3942 3943 // Don't check the whole heap at this point as the 3944 // GC alloc regions from this pause have been tagged 3945 // as survivors and moved on to the survivor list. 3946 // Survivor regions will fail the !is_young() check. 3947 assert(check_young_list_empty(false /* check_heap */), 3948 "young list should be empty"); 3949 3950 #if YOUNG_LIST_VERBOSE 3951 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3952 _young_list->print(); 3953 #endif // YOUNG_LIST_VERBOSE 3954 3955 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3956 _young_list->first_survivor_region(), 3957 _young_list->last_survivor_region()); 3958 3959 _young_list->reset_auxilary_lists(); 3960 3961 if (evacuation_failed()) { 3962 _summary_bytes_used = recalculate_used(); 3963 } else { 3964 // The "used" of the the collection set have already been subtracted 3965 // when they were freed. Add in the bytes evacuated. 3966 _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); 3967 } 3968 3969 if (g1_policy()->during_initial_mark_pause()) { 3970 // We have to do this before we notify the CM threads that 3971 // they can start working to make sure that all the 3972 // appropriate initialization is done on the CM object. 3973 concurrent_mark()->checkpointRootsInitialPost(); 3974 set_marking_started(); 3975 // Note that we don't actually trigger the CM thread at 3976 // this point. We do that later when we're sure that 3977 // the current thread has completed its logging output. 3978 } 3979 3980 allocate_dummy_regions(); 3981 3982 #if YOUNG_LIST_VERBOSE 3983 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 3984 _young_list->print(); 3985 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3986 #endif // YOUNG_LIST_VERBOSE 3987 3988 init_mutator_alloc_region(); 3989 3990 { 3991 size_t expand_bytes = g1_policy()->expansion_amount(); 3992 if (expand_bytes > 0) { 3993 size_t bytes_before = capacity(); 3994 // No need for an ergo verbose message here, 3995 // expansion_amount() does this when it returns a value > 0. 3996 if (!expand(expand_bytes)) { 3997 // We failed to expand the heap so let's verify that 3998 // committed/uncommitted amount match the backing store 3999 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 4000 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 4001 } 4002 } 4003 } 4004 4005 // We redo the verificaiton but now wrt to the new CSet which 4006 // has just got initialized after the previous CSet was freed. 4007 _cm->verify_no_cset_oops(true /* verify_stacks */, 4008 true /* verify_enqueued_buffers */, 4009 true /* verify_thread_buffers */, 4010 true /* verify_fingers */); 4011 _cm->note_end_of_gc(); 4012 4013 // This timing is only used by the ergonomics to handle our pause target. 4014 // It is unclear why this should not include the full pause. We will 4015 // investigate this in CR 7178365. 4016 double sample_end_time_sec = os::elapsedTime(); 4017 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 4018 g1_policy()->record_collection_pause_end(pause_time_ms); 4019 4020 MemoryService::track_memory_usage(); 4021 4022 // In prepare_for_verify() below we'll need to scan the deferred 4023 // update buffers to bring the RSets up-to-date if 4024 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 4025 // the update buffers we'll probably need to scan cards on the 4026 // regions we just allocated to (i.e., the GC alloc 4027 // regions). However, during the last GC we called 4028 // set_saved_mark() on all the GC alloc regions, so card 4029 // scanning might skip the [saved_mark_word()...top()] area of 4030 // those regions (i.e., the area we allocated objects into 4031 // during the last GC). But it shouldn't. Given that 4032 // saved_mark_word() is conditional on whether the GC time stamp 4033 // on the region is current or not, by incrementing the GC time 4034 // stamp here we invalidate all the GC time stamps on all the 4035 // regions and saved_mark_word() will simply return top() for 4036 // all the regions. This is a nicer way of ensuring this rather 4037 // than iterating over the regions and fixing them. In fact, the 4038 // GC time stamp increment here also ensures that 4039 // saved_mark_word() will return top() between pauses, i.e., 4040 // during concurrent refinement. So we don't need the 4041 // is_gc_active() check to decided which top to use when 4042 // scanning cards (see CR 7039627). 4043 increment_gc_time_stamp(); 4044 4045 verify_after_gc(); 4046 4047 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4048 ref_processor_stw()->verify_no_references_recorded(); 4049 4050 // CM reference discovery will be re-enabled if necessary. 4051 } 4052 4053 // We should do this after we potentially expand the heap so 4054 // that all the COMMIT events are generated before the end GC 4055 // event, and after we retire the GC alloc regions so that all 4056 // RETIRE events are generated before the end GC event. 4057 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4058 4059 if (mark_in_progress()) { 4060 concurrent_mark()->update_g1_committed(); 4061 } 4062 4063 #ifdef TRACESPINNING 4064 ParallelTaskTerminator::print_termination_counts(); 4065 #endif 4066 4067 gc_epilogue(false); 4068 } 4069 4070 // Print the remainder of the GC log output. 4071 log_gc_footer(os::elapsedTime() - pause_start_sec); 4072 4073 // It is not yet to safe to tell the concurrent mark to 4074 // start as we have some optional output below. We don't want the 4075 // output from the concurrent mark thread interfering with this 4076 // logging output either. 4077 4078 _hrs.verify_optional(); 4079 verify_region_sets_optional(); 4080 4081 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4082 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4083 4084 print_heap_after_gc(); 4085 4086 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4087 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4088 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4089 // before any GC notifications are raised. 4090 g1mm()->update_sizes(); 4091 } 4092 4093 if (G1SummarizeRSetStats && 4094 (G1SummarizeRSetStatsPeriod > 0) && 4095 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 4096 g1_rem_set()->print_summary_info(); 4097 } 4098 4099 // It should now be safe to tell the concurrent mark thread to start 4100 // without its logging output interfering with the logging output 4101 // that came from the pause. 4102 4103 if (should_start_conc_mark) { 4104 // CAUTION: after the doConcurrentMark() call below, 4105 // the concurrent marking thread(s) could be running 4106 // concurrently with us. Make sure that anything after 4107 // this point does not assume that we are the only GC thread 4108 // running. Note: of course, the actual marking work will 4109 // not start until the safepoint itself is released in 4110 // ConcurrentGCThread::safepoint_desynchronize(). 4111 doConcurrentMark(); 4112 } 4113 4114 return true; 4115 } 4116 4117 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4118 { 4119 size_t gclab_word_size; 4120 switch (purpose) { 4121 case GCAllocForSurvived: 4122 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4123 break; 4124 case GCAllocForTenured: 4125 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4126 break; 4127 default: 4128 assert(false, "unknown GCAllocPurpose"); 4129 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4130 break; 4131 } 4132 4133 // Prevent humongous PLAB sizes for two reasons: 4134 // * PLABs are allocated using a similar paths as oops, but should 4135 // never be in a humongous region 4136 // * Allowing humongous PLABs needlessly churns the region free lists 4137 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4138 } 4139 4140 void G1CollectedHeap::init_mutator_alloc_region() { 4141 assert(_mutator_alloc_region.get() == NULL, "pre-condition"); 4142 _mutator_alloc_region.init(); 4143 } 4144 4145 void G1CollectedHeap::release_mutator_alloc_region() { 4146 _mutator_alloc_region.release(); 4147 assert(_mutator_alloc_region.get() == NULL, "post-condition"); 4148 } 4149 4150 void G1CollectedHeap::init_gc_alloc_regions() { 4151 assert_at_safepoint(true /* should_be_vm_thread */); 4152 4153 _survivor_gc_alloc_region.init(); 4154 _old_gc_alloc_region.init(); 4155 HeapRegion* retained_region = _retained_old_gc_alloc_region; 4156 _retained_old_gc_alloc_region = NULL; 4157 4158 // We will discard the current GC alloc region if: 4159 // a) it's in the collection set (it can happen!), 4160 // b) it's already full (no point in using it), 4161 // c) it's empty (this means that it was emptied during 4162 // a cleanup and it should be on the free list now), or 4163 // d) it's humongous (this means that it was emptied 4164 // during a cleanup and was added to the free list, but 4165 // has been subseqently used to allocate a humongous 4166 // object that may be less than the region size). 4167 if (retained_region != NULL && 4168 !retained_region->in_collection_set() && 4169 !(retained_region->top() == retained_region->end()) && 4170 !retained_region->is_empty() && 4171 !retained_region->isHumongous()) { 4172 retained_region->set_saved_mark(); 4173 // The retained region was added to the old region set when it was 4174 // retired. We have to remove it now, since we don't allow regions 4175 // we allocate to in the region sets. We'll re-add it later, when 4176 // it's retired again. 4177 _old_set.remove(retained_region); 4178 bool during_im = g1_policy()->during_initial_mark_pause(); 4179 retained_region->note_start_of_copying(during_im); 4180 _old_gc_alloc_region.set(retained_region); 4181 _hr_printer.reuse(retained_region); 4182 } 4183 } 4184 4185 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers) { 4186 _survivor_gc_alloc_region.release(); 4187 // If we have an old GC alloc region to release, we'll save it in 4188 // _retained_old_gc_alloc_region. If we don't 4189 // _retained_old_gc_alloc_region will become NULL. This is what we 4190 // want either way so no reason to check explicitly for either 4191 // condition. 4192 _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); 4193 4194 if (ResizePLAB) { 4195 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4196 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4197 } 4198 } 4199 4200 void G1CollectedHeap::abandon_gc_alloc_regions() { 4201 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); 4202 assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); 4203 _retained_old_gc_alloc_region = NULL; 4204 } 4205 4206 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4207 _drain_in_progress = false; 4208 set_evac_failure_closure(cl); 4209 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4210 } 4211 4212 void G1CollectedHeap::finalize_for_evac_failure() { 4213 assert(_evac_failure_scan_stack != NULL && 4214 _evac_failure_scan_stack->length() == 0, 4215 "Postcondition"); 4216 assert(!_drain_in_progress, "Postcondition"); 4217 delete _evac_failure_scan_stack; 4218 _evac_failure_scan_stack = NULL; 4219 } 4220 4221 void G1CollectedHeap::remove_self_forwarding_pointers() { 4222 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4223 4224 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4225 4226 if (G1CollectedHeap::use_parallel_gc_threads()) { 4227 set_par_threads(); 4228 workers()->run_task(&rsfp_task); 4229 set_par_threads(0); 4230 } else { 4231 rsfp_task.work(0); 4232 } 4233 4234 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); 4235 4236 // Reset the claim values in the regions in the collection set. 4237 reset_cset_heap_region_claim_values(); 4238 4239 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4240 4241 // Now restore saved marks, if any. 4242 assert(_objs_with_preserved_marks.size() == 4243 _preserved_marks_of_objs.size(), "Both or none."); 4244 while (!_objs_with_preserved_marks.is_empty()) { 4245 oop obj = _objs_with_preserved_marks.pop(); 4246 markOop m = _preserved_marks_of_objs.pop(); 4247 obj->set_mark(m); 4248 } 4249 _objs_with_preserved_marks.clear(true); 4250 _preserved_marks_of_objs.clear(true); 4251 } 4252 4253 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4254 _evac_failure_scan_stack->push(obj); 4255 } 4256 4257 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4258 assert(_evac_failure_scan_stack != NULL, "precondition"); 4259 4260 while (_evac_failure_scan_stack->length() > 0) { 4261 oop obj = _evac_failure_scan_stack->pop(); 4262 _evac_failure_closure->set_region(heap_region_containing(obj)); 4263 obj->oop_iterate_backwards(_evac_failure_closure); 4264 } 4265 } 4266 4267 oop 4268 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, 4269 oop old) { 4270 assert(obj_in_cs(old), 4271 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4272 (HeapWord*) old)); 4273 markOop m = old->mark(); 4274 oop forward_ptr = old->forward_to_atomic(old); 4275 if (forward_ptr == NULL) { 4276 // Forward-to-self succeeded. 4277 4278 if (_evac_failure_closure != cl) { 4279 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4280 assert(!_drain_in_progress, 4281 "Should only be true while someone holds the lock."); 4282 // Set the global evac-failure closure to the current thread's. 4283 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4284 set_evac_failure_closure(cl); 4285 // Now do the common part. 4286 handle_evacuation_failure_common(old, m); 4287 // Reset to NULL. 4288 set_evac_failure_closure(NULL); 4289 } else { 4290 // The lock is already held, and this is recursive. 4291 assert(_drain_in_progress, "This should only be the recursive case."); 4292 handle_evacuation_failure_common(old, m); 4293 } 4294 return old; 4295 } else { 4296 // Forward-to-self failed. Either someone else managed to allocate 4297 // space for this object (old != forward_ptr) or they beat us in 4298 // self-forwarding it (old == forward_ptr). 4299 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4300 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4301 "should not be in the CSet", 4302 (HeapWord*) old, (HeapWord*) forward_ptr)); 4303 return forward_ptr; 4304 } 4305 } 4306 4307 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4308 set_evacuation_failed(true); 4309 4310 preserve_mark_if_necessary(old, m); 4311 4312 HeapRegion* r = heap_region_containing(old); 4313 if (!r->evacuation_failed()) { 4314 r->set_evacuation_failed(true); 4315 _hr_printer.evac_failure(r); 4316 } 4317 4318 push_on_evac_failure_scan_stack(old); 4319 4320 if (!_drain_in_progress) { 4321 // prevent recursion in copy_to_survivor_space() 4322 _drain_in_progress = true; 4323 drain_evac_failure_scan_stack(); 4324 _drain_in_progress = false; 4325 } 4326 } 4327 4328 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4329 assert(evacuation_failed(), "Oversaving!"); 4330 // We want to call the "for_promotion_failure" version only in the 4331 // case of a promotion failure. 4332 if (m->must_be_preserved_for_promotion_failure(obj)) { 4333 _objs_with_preserved_marks.push(obj); 4334 _preserved_marks_of_objs.push(m); 4335 } 4336 } 4337 4338 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4339 size_t word_size) { 4340 if (purpose == GCAllocForSurvived) { 4341 HeapWord* result = survivor_attempt_allocation(word_size); 4342 if (result != NULL) { 4343 return result; 4344 } else { 4345 // Let's try to allocate in the old gen in case we can fit the 4346 // object there. 4347 return old_attempt_allocation(word_size); 4348 } 4349 } else { 4350 assert(purpose == GCAllocForTenured, "sanity"); 4351 HeapWord* result = old_attempt_allocation(word_size); 4352 if (result != NULL) { 4353 return result; 4354 } else { 4355 // Let's try to allocate in the survivors in case we can fit the 4356 // object there. 4357 return survivor_attempt_allocation(word_size); 4358 } 4359 } 4360 4361 ShouldNotReachHere(); 4362 // Trying to keep some compilers happy. 4363 return NULL; 4364 } 4365 4366 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) : 4367 ParGCAllocBuffer(gclab_word_size), _retired(false) { } 4368 4369 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num) 4370 : _g1h(g1h), 4371 _refs(g1h->task_queue(queue_num)), 4372 _dcq(&g1h->dirty_card_queue_set()), 4373 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()), 4374 _g1_rem(g1h->g1_rem_set()), 4375 _hash_seed(17), _queue_num(queue_num), 4376 _term_attempts(0), 4377 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 4378 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 4379 _age_table(false), 4380 _strong_roots_time(0), _term_time(0), 4381 _alloc_buffer_waste(0), _undo_waste(0) { 4382 // we allocate G1YoungSurvRateNumRegions plus one entries, since 4383 // we "sacrifice" entry 0 to keep track of surviving bytes for 4384 // non-young regions (where the age is -1) 4385 // We also add a few elements at the beginning and at the end in 4386 // an attempt to eliminate cache contention 4387 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); 4388 uint array_length = PADDING_ELEM_NUM + 4389 real_length + 4390 PADDING_ELEM_NUM; 4391 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC); 4392 if (_surviving_young_words_base == NULL) 4393 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR, 4394 "Not enough space for young surv histo."); 4395 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 4396 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t)); 4397 4398 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 4399 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 4400 4401 _start = os::elapsedTime(); 4402 } 4403 4404 void 4405 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 4406 { 4407 st->print_raw_cr("GC Termination Stats"); 4408 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 4409 " ------waste (KiB)------"); 4410 st->print_raw_cr("thr ms ms % ms % attempts" 4411 " total alloc undo"); 4412 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 4413 " ------- ------- -------"); 4414 } 4415 4416 void 4417 G1ParScanThreadState::print_termination_stats(int i, 4418 outputStream* const st) const 4419 { 4420 const double elapsed_ms = elapsed_time() * 1000.0; 4421 const double s_roots_ms = strong_roots_time() * 1000.0; 4422 const double term_ms = term_time() * 1000.0; 4423 st->print_cr("%3d %9.2f %9.2f %6.2f " 4424 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4425 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4426 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 4427 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 4428 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 4429 alloc_buffer_waste() * HeapWordSize / K, 4430 undo_waste() * HeapWordSize / K); 4431 } 4432 4433 #ifdef ASSERT 4434 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 4435 assert(ref != NULL, "invariant"); 4436 assert(UseCompressedOops, "sanity"); 4437 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); 4438 oop p = oopDesc::load_decode_heap_oop(ref); 4439 assert(_g1h->is_in_g1_reserved(p), 4440 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4441 return true; 4442 } 4443 4444 bool G1ParScanThreadState::verify_ref(oop* ref) const { 4445 assert(ref != NULL, "invariant"); 4446 if (has_partial_array_mask(ref)) { 4447 // Must be in the collection set--it's already been copied. 4448 oop p = clear_partial_array_mask(ref); 4449 assert(_g1h->obj_in_cs(p), 4450 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4451 } else { 4452 oop p = oopDesc::load_decode_heap_oop(ref); 4453 assert(_g1h->is_in_g1_reserved(p), 4454 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4455 } 4456 return true; 4457 } 4458 4459 bool G1ParScanThreadState::verify_task(StarTask ref) const { 4460 if (ref.is_narrow()) { 4461 return verify_ref((narrowOop*) ref); 4462 } else { 4463 return verify_ref((oop*) ref); 4464 } 4465 } 4466 #endif // ASSERT 4467 4468 void G1ParScanThreadState::trim_queue() { 4469 assert(_evac_cl != NULL, "not set"); 4470 assert(_evac_failure_cl != NULL, "not set"); 4471 assert(_partial_scan_cl != NULL, "not set"); 4472 4473 StarTask ref; 4474 do { 4475 // Drain the overflow stack first, so other threads can steal. 4476 while (refs()->pop_overflow(ref)) { 4477 deal_with_reference(ref); 4478 } 4479 4480 while (refs()->pop_local(ref)) { 4481 deal_with_reference(ref); 4482 } 4483 } while (!refs()->is_empty()); 4484 } 4485 4486 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, 4487 G1ParScanThreadState* par_scan_state) : 4488 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()), 4489 _par_scan_state(par_scan_state), 4490 _worker_id(par_scan_state->queue_num()), 4491 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()), 4492 _mark_in_progress(_g1->mark_in_progress()) { } 4493 4494 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4495 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) { 4496 #ifdef ASSERT 4497 HeapRegion* hr = _g1->heap_region_containing(obj); 4498 assert(hr != NULL, "sanity"); 4499 assert(!hr->in_collection_set(), "should not mark objects in the CSet"); 4500 #endif // ASSERT 4501 4502 // We know that the object is not moving so it's safe to read its size. 4503 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4504 } 4505 4506 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4507 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4508 ::mark_forwarded_object(oop from_obj, oop to_obj) { 4509 #ifdef ASSERT 4510 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4511 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4512 assert(from_obj != to_obj, "should not be self-forwarded"); 4513 4514 HeapRegion* from_hr = _g1->heap_region_containing(from_obj); 4515 assert(from_hr != NULL, "sanity"); 4516 assert(from_hr->in_collection_set(), "from obj should be in the CSet"); 4517 4518 HeapRegion* to_hr = _g1->heap_region_containing(to_obj); 4519 assert(to_hr != NULL, "sanity"); 4520 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet"); 4521 #endif // ASSERT 4522 4523 // The object might be in the process of being copied by another 4524 // worker so we cannot trust that its to-space image is 4525 // well-formed. So we have to read its size from its from-space 4526 // image which we know should not be changing. 4527 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4528 } 4529 4530 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4531 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4532 ::copy_to_survivor_space(oop old) { 4533 size_t word_sz = old->size(); 4534 HeapRegion* from_region = _g1->heap_region_containing_raw(old); 4535 // +1 to make the -1 indexes valid... 4536 int young_index = from_region->young_index_in_cset()+1; 4537 assert( (from_region->is_young() && young_index > 0) || 4538 (!from_region->is_young() && young_index == 0), "invariant" ); 4539 G1CollectorPolicy* g1p = _g1->g1_policy(); 4540 markOop m = old->mark(); 4541 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 4542 : m->age(); 4543 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 4544 word_sz); 4545 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz); 4546 #ifndef PRODUCT 4547 // Should this evacuation fail? 4548 if (_g1->evacuation_should_fail()) { 4549 if (obj_ptr != NULL) { 4550 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4551 obj_ptr = NULL; 4552 } 4553 } 4554 #endif // !PRODUCT 4555 4556 if (obj_ptr == NULL) { 4557 // This will either forward-to-self, or detect that someone else has 4558 // installed a forwarding pointer. 4559 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4560 return _g1->handle_evacuation_failure_par(cl, old); 4561 } 4562 4563 oop obj = oop(obj_ptr); 4564 4565 // We're going to allocate linearly, so might as well prefetch ahead. 4566 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 4567 4568 oop forward_ptr = old->forward_to_atomic(obj); 4569 if (forward_ptr == NULL) { 4570 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 4571 if (g1p->track_object_age(alloc_purpose)) { 4572 // We could simply do obj->incr_age(). However, this causes a 4573 // performance issue. obj->incr_age() will first check whether 4574 // the object has a displaced mark by checking its mark word; 4575 // getting the mark word from the new location of the object 4576 // stalls. So, given that we already have the mark word and we 4577 // are about to install it anyway, it's better to increase the 4578 // age on the mark word, when the object does not have a 4579 // displaced mark word. We're not expecting many objects to have 4580 // a displaced marked word, so that case is not optimized 4581 // further (it could be...) and we simply call obj->incr_age(). 4582 4583 if (m->has_displaced_mark_helper()) { 4584 // in this case, we have to install the mark word first, 4585 // otherwise obj looks to be forwarded (the old mark word, 4586 // which contains the forward pointer, was copied) 4587 obj->set_mark(m); 4588 obj->incr_age(); 4589 } else { 4590 m = m->incr_age(); 4591 obj->set_mark(m); 4592 } 4593 _par_scan_state->age_table()->add(obj, word_sz); 4594 } else { 4595 obj->set_mark(m); 4596 } 4597 4598 size_t* surv_young_words = _par_scan_state->surviving_young_words(); 4599 surv_young_words[young_index] += word_sz; 4600 4601 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 4602 // We keep track of the next start index in the length field of 4603 // the to-space object. The actual length can be found in the 4604 // length field of the from-space object. 4605 arrayOop(obj)->set_length(0); 4606 oop* old_p = set_partial_array_mask(old); 4607 _par_scan_state->push_on_queue(old_p); 4608 } else { 4609 // No point in using the slower heap_region_containing() method, 4610 // given that we know obj is in the heap. 4611 _scanner.set_region(_g1->heap_region_containing_raw(obj)); 4612 obj->oop_iterate_backwards(&_scanner); 4613 } 4614 } else { 4615 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4616 obj = forward_ptr; 4617 } 4618 return obj; 4619 } 4620 4621 template <class T> 4622 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4623 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4624 _scanned_klass->record_modified_oops(); 4625 } 4626 } 4627 4628 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4629 template <class T> 4630 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4631 ::do_oop_work(T* p) { 4632 oop obj = oopDesc::load_decode_heap_oop(p); 4633 assert(barrier != G1BarrierRS || obj != NULL, 4634 "Precondition: G1BarrierRS implies obj is non-NULL"); 4635 4636 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4637 4638 // here the null check is implicit in the cset_fast_test() test 4639 if (_g1->in_cset_fast_test(obj)) { 4640 oop forwardee; 4641 if (obj->is_forwarded()) { 4642 forwardee = obj->forwardee(); 4643 } else { 4644 forwardee = copy_to_survivor_space(obj); 4645 } 4646 assert(forwardee != NULL, "forwardee should not be NULL"); 4647 oopDesc::encode_store_heap_oop(p, forwardee); 4648 if (do_mark_object && forwardee != obj) { 4649 // If the object is self-forwarded we don't need to explicitly 4650 // mark it, the evacuation failure protocol will do so. 4651 mark_forwarded_object(obj, forwardee); 4652 } 4653 4654 // When scanning the RS, we only care about objs in CS. 4655 if (barrier == G1BarrierRS) { 4656 _par_scan_state->update_rs(_from, p, _worker_id); 4657 } else if (barrier == G1BarrierKlass) { 4658 do_klass_barrier(p, forwardee); 4659 } 4660 } else { 4661 // The object is not in collection set. If we're a root scanning 4662 // closure during an initial mark pause (i.e. do_mark_object will 4663 // be true) then attempt to mark the object. 4664 if (do_mark_object && _g1->is_in_g1_reserved(obj)) { 4665 mark_object(obj); 4666 } 4667 } 4668 4669 if (barrier == G1BarrierEvac && obj != NULL) { 4670 _par_scan_state->update_rs(_from, p, _worker_id); 4671 } 4672 4673 if (do_gen_barrier && obj != NULL) { 4674 par_do_barrier(p); 4675 } 4676 } 4677 4678 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p); 4679 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p); 4680 4681 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) { 4682 assert(has_partial_array_mask(p), "invariant"); 4683 oop from_obj = clear_partial_array_mask(p); 4684 4685 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap."); 4686 assert(from_obj->is_objArray(), "must be obj array"); 4687 objArrayOop from_obj_array = objArrayOop(from_obj); 4688 // The from-space object contains the real length. 4689 int length = from_obj_array->length(); 4690 4691 assert(from_obj->is_forwarded(), "must be forwarded"); 4692 oop to_obj = from_obj->forwardee(); 4693 assert(from_obj != to_obj, "should not be chunking self-forwarded objects"); 4694 objArrayOop to_obj_array = objArrayOop(to_obj); 4695 // We keep track of the next start index in the length field of the 4696 // to-space object. 4697 int next_index = to_obj_array->length(); 4698 assert(0 <= next_index && next_index < length, 4699 err_msg("invariant, next index: %d, length: %d", next_index, length)); 4700 4701 int start = next_index; 4702 int end = length; 4703 int remainder = end - start; 4704 // We'll try not to push a range that's smaller than ParGCArrayScanChunk. 4705 if (remainder > 2 * ParGCArrayScanChunk) { 4706 end = start + ParGCArrayScanChunk; 4707 to_obj_array->set_length(end); 4708 // Push the remainder before we process the range in case another 4709 // worker has run out of things to do and can steal it. 4710 oop* from_obj_p = set_partial_array_mask(from_obj); 4711 _par_scan_state->push_on_queue(from_obj_p); 4712 } else { 4713 assert(length == end, "sanity"); 4714 // We'll process the final range for this object. Restore the length 4715 // so that the heap remains parsable in case of evacuation failure. 4716 to_obj_array->set_length(end); 4717 } 4718 _scanner.set_region(_g1->heap_region_containing_raw(to_obj)); 4719 // Process indexes [start,end). It will also process the header 4720 // along with the first chunk (i.e., the chunk with start == 0). 4721 // Note that at this point the length field of to_obj_array is not 4722 // correct given that we are using it to keep track of the next 4723 // start index. oop_iterate_range() (thankfully!) ignores the length 4724 // field and only relies on the start / end parameters. It does 4725 // however return the size of the object which will be incorrect. So 4726 // we have to ignore it even if we wanted to use it. 4727 to_obj_array->oop_iterate_range(&_scanner, start, end); 4728 } 4729 4730 class G1ParEvacuateFollowersClosure : public VoidClosure { 4731 protected: 4732 G1CollectedHeap* _g1h; 4733 G1ParScanThreadState* _par_scan_state; 4734 RefToScanQueueSet* _queues; 4735 ParallelTaskTerminator* _terminator; 4736 4737 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4738 RefToScanQueueSet* queues() { return _queues; } 4739 ParallelTaskTerminator* terminator() { return _terminator; } 4740 4741 public: 4742 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4743 G1ParScanThreadState* par_scan_state, 4744 RefToScanQueueSet* queues, 4745 ParallelTaskTerminator* terminator) 4746 : _g1h(g1h), _par_scan_state(par_scan_state), 4747 _queues(queues), _terminator(terminator) {} 4748 4749 void do_void(); 4750 4751 private: 4752 inline bool offer_termination(); 4753 }; 4754 4755 bool G1ParEvacuateFollowersClosure::offer_termination() { 4756 G1ParScanThreadState* const pss = par_scan_state(); 4757 pss->start_term_time(); 4758 const bool res = terminator()->offer_termination(); 4759 pss->end_term_time(); 4760 return res; 4761 } 4762 4763 void G1ParEvacuateFollowersClosure::do_void() { 4764 StarTask stolen_task; 4765 G1ParScanThreadState* const pss = par_scan_state(); 4766 pss->trim_queue(); 4767 4768 do { 4769 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { 4770 assert(pss->verify_task(stolen_task), "sanity"); 4771 if (stolen_task.is_narrow()) { 4772 pss->deal_with_reference((narrowOop*) stolen_task); 4773 } else { 4774 pss->deal_with_reference((oop*) stolen_task); 4775 } 4776 4777 // We've just processed a reference and we might have made 4778 // available new entries on the queues. So we have to make sure 4779 // we drain the queues as necessary. 4780 pss->trim_queue(); 4781 } 4782 } while (!offer_termination()); 4783 4784 pss->retire_alloc_buffers(); 4785 } 4786 4787 class G1KlassScanClosure : public KlassClosure { 4788 G1ParCopyHelper* _closure; 4789 bool _process_only_dirty; 4790 int _count; 4791 public: 4792 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4793 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4794 void do_klass(Klass* klass) { 4795 // If the klass has not been dirtied we know that there's 4796 // no references into the young gen and we can skip it. 4797 if (!_process_only_dirty || klass->has_modified_oops()) { 4798 // Clean the klass since we're going to scavenge all the metadata. 4799 klass->clear_modified_oops(); 4800 4801 // Tell the closure that this klass is the Klass to scavenge 4802 // and is the one to dirty if oops are left pointing into the young gen. 4803 _closure->set_scanned_klass(klass); 4804 4805 klass->oops_do(_closure); 4806 4807 _closure->set_scanned_klass(NULL); 4808 } 4809 _count++; 4810 } 4811 }; 4812 4813 class G1ParTask : public AbstractGangTask { 4814 protected: 4815 G1CollectedHeap* _g1h; 4816 RefToScanQueueSet *_queues; 4817 ParallelTaskTerminator _terminator; 4818 uint _n_workers; 4819 4820 Mutex _stats_lock; 4821 Mutex* stats_lock() { return &_stats_lock; } 4822 4823 size_t getNCards() { 4824 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) 4825 / G1BlockOffsetSharedArray::N_bytes; 4826 } 4827 4828 public: 4829 G1ParTask(G1CollectedHeap* g1h, 4830 RefToScanQueueSet *task_queues) 4831 : AbstractGangTask("G1 collection"), 4832 _g1h(g1h), 4833 _queues(task_queues), 4834 _terminator(0, _queues), 4835 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4836 {} 4837 4838 RefToScanQueueSet* queues() { return _queues; } 4839 4840 RefToScanQueue *work_queue(int i) { 4841 return queues()->queue(i); 4842 } 4843 4844 ParallelTaskTerminator* terminator() { return &_terminator; } 4845 4846 virtual void set_for_termination(int active_workers) { 4847 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4848 // in the young space (_par_seq_tasks) in the G1 heap 4849 // for SequentialSubTasksDone. 4850 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4851 // both of which need setting by set_n_termination(). 4852 _g1h->SharedHeap::set_n_termination(active_workers); 4853 _g1h->set_n_termination(active_workers); 4854 terminator()->reset_for_reuse(active_workers); 4855 _n_workers = active_workers; 4856 } 4857 4858 void work(uint worker_id) { 4859 if (worker_id >= _n_workers) return; // no work needed this round 4860 4861 double start_time_ms = os::elapsedTime() * 1000.0; 4862 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 4863 4864 { 4865 ResourceMark rm; 4866 HandleMark hm; 4867 4868 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4869 4870 G1ParScanThreadState pss(_g1h, worker_id); 4871 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp); 4872 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4873 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp); 4874 4875 pss.set_evac_closure(&scan_evac_cl); 4876 pss.set_evac_failure_closure(&evac_failure_cl); 4877 pss.set_partial_scan_closure(&partial_scan_cl); 4878 4879 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp); 4880 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp); 4881 4882 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp); 4883 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp); 4884 4885 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4886 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false); 4887 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young); 4888 4889 OopClosure* scan_root_cl = &only_scan_root_cl; 4890 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s; 4891 4892 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4893 // We also need to mark copied objects. 4894 scan_root_cl = &scan_mark_root_cl; 4895 scan_klasses_cl = &scan_mark_klasses_cl_s; 4896 } 4897 4898 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4899 4900 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; 4901 4902 pss.start_strong_roots(); 4903 _g1h->g1_process_strong_roots(/* is scavenging */ true, 4904 SharedHeap::ScanningOption(so), 4905 scan_root_cl, 4906 &push_heap_rs_cl, 4907 scan_klasses_cl, 4908 worker_id); 4909 pss.end_strong_roots(); 4910 4911 { 4912 double start = os::elapsedTime(); 4913 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4914 evac.do_void(); 4915 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4916 double term_ms = pss.term_time()*1000.0; 4917 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 4918 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 4919 } 4920 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4921 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4922 4923 if (ParallelGCVerbose) { 4924 MutexLocker x(stats_lock()); 4925 pss.print_termination_stats(worker_id); 4926 } 4927 4928 assert(pss.refs()->is_empty(), "should be empty"); 4929 4930 // Close the inner scope so that the ResourceMark and HandleMark 4931 // destructors are executed here and are included as part of the 4932 // "GC Worker Time". 4933 } 4934 4935 double end_time_ms = os::elapsedTime() * 1000.0; 4936 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 4937 } 4938 }; 4939 4940 // *** Common G1 Evacuation Stuff 4941 4942 // Closures that support the filtering of CodeBlobs scanned during 4943 // external root scanning. 4944 4945 // Closure applied to reference fields in code blobs (specifically nmethods) 4946 // to determine whether an nmethod contains references that point into 4947 // the collection set. Used as a predicate when walking code roots so 4948 // that only nmethods that point into the collection set are added to the 4949 // 'marked' list. 4950 4951 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure { 4952 4953 class G1PointsIntoCSOopClosure : public OopClosure { 4954 G1CollectedHeap* _g1; 4955 bool _points_into_cs; 4956 public: 4957 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) : 4958 _g1(g1), _points_into_cs(false) { } 4959 4960 bool points_into_cs() const { return _points_into_cs; } 4961 4962 template <class T> 4963 void do_oop_nv(T* p) { 4964 if (!_points_into_cs) { 4965 T heap_oop = oopDesc::load_heap_oop(p); 4966 if (!oopDesc::is_null(heap_oop) && 4967 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) { 4968 _points_into_cs = true; 4969 } 4970 } 4971 } 4972 4973 virtual void do_oop(oop* p) { do_oop_nv(p); } 4974 virtual void do_oop(narrowOop* p) { do_oop_nv(p); } 4975 }; 4976 4977 G1CollectedHeap* _g1; 4978 4979 public: 4980 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) : 4981 CodeBlobToOopClosure(cl, true), _g1(g1) { } 4982 4983 virtual void do_code_blob(CodeBlob* cb) { 4984 nmethod* nm = cb->as_nmethod_or_null(); 4985 if (nm != NULL && !(nm->test_oops_do_mark())) { 4986 G1PointsIntoCSOopClosure predicate_cl(_g1); 4987 nm->oops_do(&predicate_cl); 4988 4989 if (predicate_cl.points_into_cs()) { 4990 // At least one of the reference fields or the oop relocations 4991 // in the nmethod points into the collection set. We have to 4992 // 'mark' this nmethod. 4993 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob() 4994 // or MarkingCodeBlobClosure::do_code_blob() change. 4995 if (!nm->test_set_oops_do_mark()) { 4996 do_newly_marked_nmethod(nm); 4997 } 4998 } 4999 } 5000 } 5001 }; 5002 5003 // This method is run in a GC worker. 5004 5005 void 5006 G1CollectedHeap:: 5007 g1_process_strong_roots(bool is_scavenging, 5008 ScanningOption so, 5009 OopClosure* scan_non_heap_roots, 5010 OopsInHeapRegionClosure* scan_rs, 5011 G1KlassScanClosure* scan_klasses, 5012 int worker_i) { 5013 5014 // First scan the strong roots 5015 double ext_roots_start = os::elapsedTime(); 5016 double closure_app_time_sec = 0.0; 5017 5018 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 5019 5020 // Walk the code cache w/o buffering, because StarTask cannot handle 5021 // unaligned oop locations. 5022 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots); 5023 5024 process_strong_roots(false, // no scoping; this is parallel code 5025 is_scavenging, so, 5026 &buf_scan_non_heap_roots, 5027 &eager_scan_code_roots, 5028 scan_klasses 5029 ); 5030 5031 // Now the CM ref_processor roots. 5032 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 5033 // We need to treat the discovered reference lists of the 5034 // concurrent mark ref processor as roots and keep entries 5035 // (which are added by the marking threads) on them live 5036 // until they can be processed at the end of marking. 5037 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 5038 } 5039 5040 // Finish up any enqueued closure apps (attributed as object copy time). 5041 buf_scan_non_heap_roots.done(); 5042 5043 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds(); 5044 5045 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 5046 5047 double ext_root_time_ms = 5048 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 5049 5050 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 5051 5052 // During conc marking we have to filter the per-thread SATB buffers 5053 // to make sure we remove any oops into the CSet (which will show up 5054 // as implicitly live). 5055 double satb_filtering_ms = 0.0; 5056 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 5057 if (mark_in_progress()) { 5058 double satb_filter_start = os::elapsedTime(); 5059 5060 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 5061 5062 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 5063 } 5064 } 5065 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 5066 5067 // Now scan the complement of the collection set. 5068 if (scan_rs != NULL) { 5069 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i); 5070 } 5071 _process_strong_tasks->all_tasks_completed(); 5072 } 5073 5074 void 5075 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) { 5076 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); 5077 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs); 5078 } 5079 5080 // Weak Reference Processing support 5081 5082 // An always "is_alive" closure that is used to preserve referents. 5083 // If the object is non-null then it's alive. Used in the preservation 5084 // of referent objects that are pointed to by reference objects 5085 // discovered by the CM ref processor. 5086 class G1AlwaysAliveClosure: public BoolObjectClosure { 5087 G1CollectedHeap* _g1; 5088 public: 5089 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5090 void do_object(oop p) { assert(false, "Do not call."); } 5091 bool do_object_b(oop p) { 5092 if (p != NULL) { 5093 return true; 5094 } 5095 return false; 5096 } 5097 }; 5098 5099 bool G1STWIsAliveClosure::do_object_b(oop p) { 5100 // An object is reachable if it is outside the collection set, 5101 // or is inside and copied. 5102 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5103 } 5104 5105 // Non Copying Keep Alive closure 5106 class G1KeepAliveClosure: public OopClosure { 5107 G1CollectedHeap* _g1; 5108 public: 5109 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5110 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5111 void do_oop( oop* p) { 5112 oop obj = *p; 5113 5114 if (_g1->obj_in_cs(obj)) { 5115 assert( obj->is_forwarded(), "invariant" ); 5116 *p = obj->forwardee(); 5117 } 5118 } 5119 }; 5120 5121 // Copying Keep Alive closure - can be called from both 5122 // serial and parallel code as long as different worker 5123 // threads utilize different G1ParScanThreadState instances 5124 // and different queues. 5125 5126 class G1CopyingKeepAliveClosure: public OopClosure { 5127 G1CollectedHeap* _g1h; 5128 OopClosure* _copy_non_heap_obj_cl; 5129 OopsInHeapRegionClosure* _copy_metadata_obj_cl; 5130 G1ParScanThreadState* _par_scan_state; 5131 5132 public: 5133 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5134 OopClosure* non_heap_obj_cl, 5135 OopsInHeapRegionClosure* metadata_obj_cl, 5136 G1ParScanThreadState* pss): 5137 _g1h(g1h), 5138 _copy_non_heap_obj_cl(non_heap_obj_cl), 5139 _copy_metadata_obj_cl(metadata_obj_cl), 5140 _par_scan_state(pss) 5141 {} 5142 5143 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5144 virtual void do_oop( oop* p) { do_oop_work(p); } 5145 5146 template <class T> void do_oop_work(T* p) { 5147 oop obj = oopDesc::load_decode_heap_oop(p); 5148 5149 if (_g1h->obj_in_cs(obj)) { 5150 // If the referent object has been forwarded (either copied 5151 // to a new location or to itself in the event of an 5152 // evacuation failure) then we need to update the reference 5153 // field and, if both reference and referent are in the G1 5154 // heap, update the RSet for the referent. 5155 // 5156 // If the referent has not been forwarded then we have to keep 5157 // it alive by policy. Therefore we have copy the referent. 5158 // 5159 // If the reference field is in the G1 heap then we can push 5160 // on the PSS queue. When the queue is drained (after each 5161 // phase of reference processing) the object and it's followers 5162 // will be copied, the reference field set to point to the 5163 // new location, and the RSet updated. Otherwise we need to 5164 // use the the non-heap or metadata closures directly to copy 5165 // the refernt object and update the pointer, while avoiding 5166 // updating the RSet. 5167 5168 if (_g1h->is_in_g1_reserved(p)) { 5169 _par_scan_state->push_on_queue(p); 5170 } else { 5171 assert(!ClassLoaderDataGraph::contains((address)p), 5172 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) " 5173 PTR_FORMAT, p)); 5174 _copy_non_heap_obj_cl->do_oop(p); 5175 } 5176 } 5177 } 5178 }; 5179 5180 // Serial drain queue closure. Called as the 'complete_gc' 5181 // closure for each discovered list in some of the 5182 // reference processing phases. 5183 5184 class G1STWDrainQueueClosure: public VoidClosure { 5185 protected: 5186 G1CollectedHeap* _g1h; 5187 G1ParScanThreadState* _par_scan_state; 5188 5189 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5190 5191 public: 5192 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5193 _g1h(g1h), 5194 _par_scan_state(pss) 5195 { } 5196 5197 void do_void() { 5198 G1ParScanThreadState* const pss = par_scan_state(); 5199 pss->trim_queue(); 5200 } 5201 }; 5202 5203 // Parallel Reference Processing closures 5204 5205 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5206 // processing during G1 evacuation pauses. 5207 5208 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5209 private: 5210 G1CollectedHeap* _g1h; 5211 RefToScanQueueSet* _queues; 5212 FlexibleWorkGang* _workers; 5213 int _active_workers; 5214 5215 public: 5216 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5217 FlexibleWorkGang* workers, 5218 RefToScanQueueSet *task_queues, 5219 int n_workers) : 5220 _g1h(g1h), 5221 _queues(task_queues), 5222 _workers(workers), 5223 _active_workers(n_workers) 5224 { 5225 assert(n_workers > 0, "shouldn't call this otherwise"); 5226 } 5227 5228 // Executes the given task using concurrent marking worker threads. 5229 virtual void execute(ProcessTask& task); 5230 virtual void execute(EnqueueTask& task); 5231 }; 5232 5233 // Gang task for possibly parallel reference processing 5234 5235 class G1STWRefProcTaskProxy: public AbstractGangTask { 5236 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5237 ProcessTask& _proc_task; 5238 G1CollectedHeap* _g1h; 5239 RefToScanQueueSet *_task_queues; 5240 ParallelTaskTerminator* _terminator; 5241 5242 public: 5243 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5244 G1CollectedHeap* g1h, 5245 RefToScanQueueSet *task_queues, 5246 ParallelTaskTerminator* terminator) : 5247 AbstractGangTask("Process reference objects in parallel"), 5248 _proc_task(proc_task), 5249 _g1h(g1h), 5250 _task_queues(task_queues), 5251 _terminator(terminator) 5252 {} 5253 5254 virtual void work(uint worker_id) { 5255 // The reference processing task executed by a single worker. 5256 ResourceMark rm; 5257 HandleMark hm; 5258 5259 G1STWIsAliveClosure is_alive(_g1h); 5260 5261 G1ParScanThreadState pss(_g1h, worker_id); 5262 5263 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5264 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5265 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5266 5267 pss.set_evac_closure(&scan_evac_cl); 5268 pss.set_evac_failure_closure(&evac_failure_cl); 5269 pss.set_partial_scan_closure(&partial_scan_cl); 5270 5271 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5272 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5273 5274 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5275 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5276 5277 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5278 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5279 5280 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5281 // We also need to mark copied objects. 5282 copy_non_heap_cl = ©_mark_non_heap_cl; 5283 copy_metadata_cl = ©_mark_metadata_cl; 5284 } 5285 5286 // Keep alive closure. 5287 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5288 5289 // Complete GC closure 5290 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5291 5292 // Call the reference processing task's work routine. 5293 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5294 5295 // Note we cannot assert that the refs array is empty here as not all 5296 // of the processing tasks (specifically phase2 - pp2_work) execute 5297 // the complete_gc closure (which ordinarily would drain the queue) so 5298 // the queue may not be empty. 5299 } 5300 }; 5301 5302 // Driver routine for parallel reference processing. 5303 // Creates an instance of the ref processing gang 5304 // task and has the worker threads execute it. 5305 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5306 assert(_workers != NULL, "Need parallel worker threads."); 5307 5308 ParallelTaskTerminator terminator(_active_workers, _queues); 5309 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5310 5311 _g1h->set_par_threads(_active_workers); 5312 _workers->run_task(&proc_task_proxy); 5313 _g1h->set_par_threads(0); 5314 } 5315 5316 // Gang task for parallel reference enqueueing. 5317 5318 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5319 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5320 EnqueueTask& _enq_task; 5321 5322 public: 5323 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5324 AbstractGangTask("Enqueue reference objects in parallel"), 5325 _enq_task(enq_task) 5326 { } 5327 5328 virtual void work(uint worker_id) { 5329 _enq_task.work(worker_id); 5330 } 5331 }; 5332 5333 // Driver routine for parallel reference enqueing. 5334 // Creates an instance of the ref enqueueing gang 5335 // task and has the worker threads execute it. 5336 5337 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5338 assert(_workers != NULL, "Need parallel worker threads."); 5339 5340 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5341 5342 _g1h->set_par_threads(_active_workers); 5343 _workers->run_task(&enq_task_proxy); 5344 _g1h->set_par_threads(0); 5345 } 5346 5347 // End of weak reference support closures 5348 5349 // Abstract task used to preserve (i.e. copy) any referent objects 5350 // that are in the collection set and are pointed to by reference 5351 // objects discovered by the CM ref processor. 5352 5353 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5354 protected: 5355 G1CollectedHeap* _g1h; 5356 RefToScanQueueSet *_queues; 5357 ParallelTaskTerminator _terminator; 5358 uint _n_workers; 5359 5360 public: 5361 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5362 AbstractGangTask("ParPreserveCMReferents"), 5363 _g1h(g1h), 5364 _queues(task_queues), 5365 _terminator(workers, _queues), 5366 _n_workers(workers) 5367 { } 5368 5369 void work(uint worker_id) { 5370 ResourceMark rm; 5371 HandleMark hm; 5372 5373 G1ParScanThreadState pss(_g1h, worker_id); 5374 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5375 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5376 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5377 5378 pss.set_evac_closure(&scan_evac_cl); 5379 pss.set_evac_failure_closure(&evac_failure_cl); 5380 pss.set_partial_scan_closure(&partial_scan_cl); 5381 5382 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5383 5384 5385 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5386 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5387 5388 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5389 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5390 5391 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5392 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5393 5394 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5395 // We also need to mark copied objects. 5396 copy_non_heap_cl = ©_mark_non_heap_cl; 5397 copy_metadata_cl = ©_mark_metadata_cl; 5398 } 5399 5400 // Is alive closure 5401 G1AlwaysAliveClosure always_alive(_g1h); 5402 5403 // Copying keep alive closure. Applied to referent objects that need 5404 // to be copied. 5405 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5406 5407 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5408 5409 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5410 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5411 5412 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5413 // So this must be true - but assert just in case someone decides to 5414 // change the worker ids. 5415 assert(0 <= worker_id && worker_id < limit, "sanity"); 5416 assert(!rp->discovery_is_atomic(), "check this code"); 5417 5418 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5419 for (uint idx = worker_id; idx < limit; idx += stride) { 5420 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5421 5422 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5423 while (iter.has_next()) { 5424 // Since discovery is not atomic for the CM ref processor, we 5425 // can see some null referent objects. 5426 iter.load_ptrs(DEBUG_ONLY(true)); 5427 oop ref = iter.obj(); 5428 5429 // This will filter nulls. 5430 if (iter.is_referent_alive()) { 5431 iter.make_referent_alive(); 5432 } 5433 iter.move_to_next(); 5434 } 5435 } 5436 5437 // Drain the queue - which may cause stealing 5438 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5439 drain_queue.do_void(); 5440 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5441 assert(pss.refs()->is_empty(), "should be"); 5442 } 5443 }; 5444 5445 // Weak Reference processing during an evacuation pause (part 1). 5446 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5447 double ref_proc_start = os::elapsedTime(); 5448 5449 ReferenceProcessor* rp = _ref_processor_stw; 5450 assert(rp->discovery_enabled(), "should have been enabled"); 5451 5452 // Any reference objects, in the collection set, that were 'discovered' 5453 // by the CM ref processor should have already been copied (either by 5454 // applying the external root copy closure to the discovered lists, or 5455 // by following an RSet entry). 5456 // 5457 // But some of the referents, that are in the collection set, that these 5458 // reference objects point to may not have been copied: the STW ref 5459 // processor would have seen that the reference object had already 5460 // been 'discovered' and would have skipped discovering the reference, 5461 // but would not have treated the reference object as a regular oop. 5462 // As a reult the copy closure would not have been applied to the 5463 // referent object. 5464 // 5465 // We need to explicitly copy these referent objects - the references 5466 // will be processed at the end of remarking. 5467 // 5468 // We also need to do this copying before we process the reference 5469 // objects discovered by the STW ref processor in case one of these 5470 // referents points to another object which is also referenced by an 5471 // object discovered by the STW ref processor. 5472 5473 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5474 no_of_gc_workers == workers()->active_workers(), 5475 "Need to reset active GC workers"); 5476 5477 set_par_threads(no_of_gc_workers); 5478 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5479 no_of_gc_workers, 5480 _task_queues); 5481 5482 if (G1CollectedHeap::use_parallel_gc_threads()) { 5483 workers()->run_task(&keep_cm_referents); 5484 } else { 5485 keep_cm_referents.work(0); 5486 } 5487 5488 set_par_threads(0); 5489 5490 // Closure to test whether a referent is alive. 5491 G1STWIsAliveClosure is_alive(this); 5492 5493 // Even when parallel reference processing is enabled, the processing 5494 // of JNI refs is serial and performed serially by the current thread 5495 // rather than by a worker. The following PSS will be used for processing 5496 // JNI refs. 5497 5498 // Use only a single queue for this PSS. 5499 G1ParScanThreadState pss(this, 0); 5500 5501 // We do not embed a reference processor in the copying/scanning 5502 // closures while we're actually processing the discovered 5503 // reference objects. 5504 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL); 5505 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5506 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL); 5507 5508 pss.set_evac_closure(&scan_evac_cl); 5509 pss.set_evac_failure_closure(&evac_failure_cl); 5510 pss.set_partial_scan_closure(&partial_scan_cl); 5511 5512 assert(pss.refs()->is_empty(), "pre-condition"); 5513 5514 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5515 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL); 5516 5517 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5518 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL); 5519 5520 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5521 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5522 5523 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5524 // We also need to mark copied objects. 5525 copy_non_heap_cl = ©_mark_non_heap_cl; 5526 copy_metadata_cl = ©_mark_metadata_cl; 5527 } 5528 5529 // Keep alive closure. 5530 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss); 5531 5532 // Serial Complete GC closure 5533 G1STWDrainQueueClosure drain_queue(this, &pss); 5534 5535 // Setup the soft refs policy... 5536 rp->setup_policy(false); 5537 5538 if (!rp->processing_is_mt()) { 5539 // Serial reference processing... 5540 rp->process_discovered_references(&is_alive, 5541 &keep_alive, 5542 &drain_queue, 5543 NULL); 5544 } else { 5545 // Parallel reference processing 5546 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5547 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5548 5549 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5550 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor); 5551 } 5552 5553 // We have completed copying any necessary live referent objects 5554 // (that were not copied during the actual pause) so we can 5555 // retire any active alloc buffers 5556 pss.retire_alloc_buffers(); 5557 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5558 5559 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5560 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5561 } 5562 5563 // Weak Reference processing during an evacuation pause (part 2). 5564 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5565 double ref_enq_start = os::elapsedTime(); 5566 5567 ReferenceProcessor* rp = _ref_processor_stw; 5568 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5569 5570 // Now enqueue any remaining on the discovered lists on to 5571 // the pending list. 5572 if (!rp->processing_is_mt()) { 5573 // Serial reference processing... 5574 rp->enqueue_discovered_references(); 5575 } else { 5576 // Parallel reference enqueuing 5577 5578 assert(no_of_gc_workers == workers()->active_workers(), 5579 "Need to reset active workers"); 5580 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5581 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5582 5583 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5584 rp->enqueue_discovered_references(&par_task_executor); 5585 } 5586 5587 rp->verify_no_references_recorded(); 5588 assert(!rp->discovery_enabled(), "should have been disabled"); 5589 5590 // FIXME 5591 // CM's reference processing also cleans up the string and symbol tables. 5592 // Should we do that here also? We could, but it is a serial operation 5593 // and could signicantly increase the pause time. 5594 5595 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5596 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5597 } 5598 5599 void G1CollectedHeap::evacuate_collection_set() { 5600 _expand_heap_after_alloc_failure = true; 5601 set_evacuation_failed(false); 5602 5603 // Should G1EvacuationFailureALot be in effect for this GC? 5604 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5605 5606 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5607 concurrent_g1_refine()->set_use_cache(false); 5608 concurrent_g1_refine()->clear_hot_cache_claimed_index(); 5609 5610 uint n_workers; 5611 if (G1CollectedHeap::use_parallel_gc_threads()) { 5612 n_workers = 5613 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5614 workers()->active_workers(), 5615 Threads::number_of_non_daemon_threads()); 5616 assert(UseDynamicNumberOfGCThreads || 5617 n_workers == workers()->total_workers(), 5618 "If not dynamic should be using all the workers"); 5619 workers()->set_active_workers(n_workers); 5620 set_par_threads(n_workers); 5621 } else { 5622 assert(n_par_threads() == 0, 5623 "Should be the original non-parallel value"); 5624 n_workers = 1; 5625 } 5626 5627 G1ParTask g1_par_task(this, _task_queues); 5628 5629 init_for_evac_failure(NULL); 5630 5631 rem_set()->prepare_for_younger_refs_iterate(true); 5632 5633 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5634 double start_par_time_sec = os::elapsedTime(); 5635 double end_par_time_sec; 5636 5637 { 5638 StrongRootsScope srs(this); 5639 5640 if (G1CollectedHeap::use_parallel_gc_threads()) { 5641 // The individual threads will set their evac-failure closures. 5642 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5643 // These tasks use ShareHeap::_process_strong_tasks 5644 assert(UseDynamicNumberOfGCThreads || 5645 workers()->active_workers() == workers()->total_workers(), 5646 "If not dynamic should be using all the workers"); 5647 workers()->run_task(&g1_par_task); 5648 } else { 5649 g1_par_task.set_for_termination(n_workers); 5650 g1_par_task.work(0); 5651 } 5652 end_par_time_sec = os::elapsedTime(); 5653 5654 // Closing the inner scope will execute the destructor 5655 // for the StrongRootsScope object. We record the current 5656 // elapsed time before closing the scope so that time 5657 // taken for the SRS destructor is NOT included in the 5658 // reported parallel time. 5659 } 5660 5661 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5662 g1_policy()->phase_times()->record_par_time(par_time_ms); 5663 5664 double code_root_fixup_time_ms = 5665 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5666 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5667 5668 set_par_threads(0); 5669 5670 // Process any discovered reference objects - we have 5671 // to do this _before_ we retire the GC alloc regions 5672 // as we may have to copy some 'reachable' referent 5673 // objects (and their reachable sub-graphs) that were 5674 // not copied during the pause. 5675 process_discovered_references(n_workers); 5676 5677 // Weak root processing. 5678 // Note: when JSR 292 is enabled and code blobs can contain 5679 // non-perm oops then we will need to process the code blobs 5680 // here too. 5681 { 5682 G1STWIsAliveClosure is_alive(this); 5683 G1KeepAliveClosure keep_alive(this); 5684 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5685 } 5686 5687 release_gc_alloc_regions(n_workers); 5688 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5689 5690 concurrent_g1_refine()->clear_hot_cache(); 5691 concurrent_g1_refine()->set_use_cache(true); 5692 5693 finalize_for_evac_failure(); 5694 5695 if (evacuation_failed()) { 5696 remove_self_forwarding_pointers(); 5697 5698 // Reset the G1EvacuationFailureALot counters and flags 5699 // Note: the values are reset only when an actual 5700 // evacuation failure occurs. 5701 NOT_PRODUCT(reset_evacuation_should_fail();) 5702 } 5703 5704 // Enqueue any remaining references remaining on the STW 5705 // reference processor's discovered lists. We need to do 5706 // this after the card table is cleaned (and verified) as 5707 // the act of enqueuing entries on to the pending list 5708 // will log these updates (and dirty their associated 5709 // cards). We need these updates logged to update any 5710 // RSets. 5711 enqueue_discovered_references(n_workers); 5712 5713 if (G1DeferredRSUpdate) { 5714 RedirtyLoggedCardTableEntryFastClosure redirty; 5715 dirty_card_queue_set().set_closure(&redirty); 5716 dirty_card_queue_set().apply_closure_to_all_completed_buffers(); 5717 5718 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5719 dcq.merge_bufferlists(&dirty_card_queue_set()); 5720 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5721 } 5722 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5723 } 5724 5725 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr, 5726 size_t* pre_used, 5727 FreeRegionList* free_list, 5728 OldRegionSet* old_proxy_set, 5729 HumongousRegionSet* humongous_proxy_set, 5730 HRRSCleanupTask* hrrs_cleanup_task, 5731 bool par) { 5732 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 5733 if (hr->isHumongous()) { 5734 assert(hr->startsHumongous(), "we should only see starts humongous"); 5735 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par); 5736 } else { 5737 _old_set.remove_with_proxy(hr, old_proxy_set); 5738 free_region(hr, pre_used, free_list, par); 5739 } 5740 } else { 5741 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task); 5742 } 5743 } 5744 5745 void G1CollectedHeap::free_region(HeapRegion* hr, 5746 size_t* pre_used, 5747 FreeRegionList* free_list, 5748 bool par) { 5749 assert(!hr->isHumongous(), "this is only for non-humongous regions"); 5750 assert(!hr->is_empty(), "the region should not be empty"); 5751 assert(free_list != NULL, "pre-condition"); 5752 5753 *pre_used += hr->used(); 5754 hr->hr_clear(par, true /* clear_space */); 5755 free_list->add_as_head(hr); 5756 } 5757 5758 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5759 size_t* pre_used, 5760 FreeRegionList* free_list, 5761 HumongousRegionSet* humongous_proxy_set, 5762 bool par) { 5763 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 5764 assert(free_list != NULL, "pre-condition"); 5765 assert(humongous_proxy_set != NULL, "pre-condition"); 5766 5767 size_t hr_used = hr->used(); 5768 size_t hr_capacity = hr->capacity(); 5769 size_t hr_pre_used = 0; 5770 _humongous_set.remove_with_proxy(hr, humongous_proxy_set); 5771 // We need to read this before we make the region non-humongous, 5772 // otherwise the information will be gone. 5773 uint last_index = hr->last_hc_index(); 5774 hr->set_notHumongous(); 5775 free_region(hr, &hr_pre_used, free_list, par); 5776 5777 uint i = hr->hrs_index() + 1; 5778 while (i < last_index) { 5779 HeapRegion* curr_hr = region_at(i); 5780 assert(curr_hr->continuesHumongous(), "invariant"); 5781 curr_hr->set_notHumongous(); 5782 free_region(curr_hr, &hr_pre_used, free_list, par); 5783 i += 1; 5784 } 5785 assert(hr_pre_used == hr_used, 5786 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" " 5787 "should be the same", hr_pre_used, hr_used)); 5788 *pre_used += hr_pre_used; 5789 } 5790 5791 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used, 5792 FreeRegionList* free_list, 5793 OldRegionSet* old_proxy_set, 5794 HumongousRegionSet* humongous_proxy_set, 5795 bool par) { 5796 if (pre_used > 0) { 5797 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL; 5798 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); 5799 assert(_summary_bytes_used >= pre_used, 5800 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" " 5801 "should be >= pre_used: "SIZE_FORMAT, 5802 _summary_bytes_used, pre_used)); 5803 _summary_bytes_used -= pre_used; 5804 } 5805 if (free_list != NULL && !free_list->is_empty()) { 5806 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5807 _free_list.add_as_head(free_list); 5808 } 5809 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) { 5810 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5811 _old_set.update_from_proxy(old_proxy_set); 5812 } 5813 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) { 5814 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5815 _humongous_set.update_from_proxy(humongous_proxy_set); 5816 } 5817 } 5818 5819 class G1ParCleanupCTTask : public AbstractGangTask { 5820 CardTableModRefBS* _ct_bs; 5821 G1CollectedHeap* _g1h; 5822 HeapRegion* volatile _su_head; 5823 public: 5824 G1ParCleanupCTTask(CardTableModRefBS* ct_bs, 5825 G1CollectedHeap* g1h) : 5826 AbstractGangTask("G1 Par Cleanup CT Task"), 5827 _ct_bs(ct_bs), _g1h(g1h) { } 5828 5829 void work(uint worker_id) { 5830 HeapRegion* r; 5831 while (r = _g1h->pop_dirty_cards_region()) { 5832 clear_cards(r); 5833 } 5834 } 5835 5836 void clear_cards(HeapRegion* r) { 5837 // Cards of the survivors should have already been dirtied. 5838 if (!r->is_survivor()) { 5839 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5840 } 5841 } 5842 }; 5843 5844 #ifndef PRODUCT 5845 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5846 G1CollectedHeap* _g1h; 5847 CardTableModRefBS* _ct_bs; 5848 public: 5849 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs) 5850 : _g1h(g1h), _ct_bs(ct_bs) { } 5851 virtual bool doHeapRegion(HeapRegion* r) { 5852 if (r->is_survivor()) { 5853 _g1h->verify_dirty_region(r); 5854 } else { 5855 _g1h->verify_not_dirty_region(r); 5856 } 5857 return false; 5858 } 5859 }; 5860 5861 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5862 // All of the region should be clean. 5863 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 5864 MemRegion mr(hr->bottom(), hr->end()); 5865 ct_bs->verify_not_dirty_region(mr); 5866 } 5867 5868 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5869 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5870 // dirty allocated blocks as they allocate them. The thread that 5871 // retires each region and replaces it with a new one will do a 5872 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5873 // not dirty that area (one less thing to have to do while holding 5874 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5875 // is dirty. 5876 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5877 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5878 ct_bs->verify_dirty_region(mr); 5879 } 5880 5881 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5882 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5883 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5884 verify_dirty_region(hr); 5885 } 5886 } 5887 5888 void G1CollectedHeap::verify_dirty_young_regions() { 5889 verify_dirty_young_list(_young_list->first_region()); 5890 } 5891 #endif 5892 5893 void G1CollectedHeap::cleanUpCardTable() { 5894 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set()); 5895 double start = os::elapsedTime(); 5896 5897 { 5898 // Iterate over the dirty cards region list. 5899 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5900 5901 if (G1CollectedHeap::use_parallel_gc_threads()) { 5902 set_par_threads(); 5903 workers()->run_task(&cleanup_task); 5904 set_par_threads(0); 5905 } else { 5906 while (_dirty_cards_region_list) { 5907 HeapRegion* r = _dirty_cards_region_list; 5908 cleanup_task.clear_cards(r); 5909 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 5910 if (_dirty_cards_region_list == r) { 5911 // The last region. 5912 _dirty_cards_region_list = NULL; 5913 } 5914 r->set_next_dirty_cards_region(NULL); 5915 } 5916 } 5917 #ifndef PRODUCT 5918 if (G1VerifyCTCleanup || VerifyAfterGC) { 5919 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5920 heap_region_iterate(&cleanup_verifier); 5921 } 5922 #endif 5923 } 5924 5925 double elapsed = os::elapsedTime() - start; 5926 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5927 } 5928 5929 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) { 5930 size_t pre_used = 0; 5931 FreeRegionList local_free_list("Local List for CSet Freeing"); 5932 5933 double young_time_ms = 0.0; 5934 double non_young_time_ms = 0.0; 5935 5936 // Since the collection set is a superset of the the young list, 5937 // all we need to do to clear the young list is clear its 5938 // head and length, and unlink any young regions in the code below 5939 _young_list->clear(); 5940 5941 G1CollectorPolicy* policy = g1_policy(); 5942 5943 double start_sec = os::elapsedTime(); 5944 bool non_young = true; 5945 5946 HeapRegion* cur = cs_head; 5947 int age_bound = -1; 5948 size_t rs_lengths = 0; 5949 5950 while (cur != NULL) { 5951 assert(!is_on_master_free_list(cur), "sanity"); 5952 if (non_young) { 5953 if (cur->is_young()) { 5954 double end_sec = os::elapsedTime(); 5955 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5956 non_young_time_ms += elapsed_ms; 5957 5958 start_sec = os::elapsedTime(); 5959 non_young = false; 5960 } 5961 } else { 5962 if (!cur->is_young()) { 5963 double end_sec = os::elapsedTime(); 5964 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5965 young_time_ms += elapsed_ms; 5966 5967 start_sec = os::elapsedTime(); 5968 non_young = true; 5969 } 5970 } 5971 5972 rs_lengths += cur->rem_set()->occupied(); 5973 5974 HeapRegion* next = cur->next_in_collection_set(); 5975 assert(cur->in_collection_set(), "bad CS"); 5976 cur->set_next_in_collection_set(NULL); 5977 cur->set_in_collection_set(false); 5978 5979 if (cur->is_young()) { 5980 int index = cur->young_index_in_cset(); 5981 assert(index != -1, "invariant"); 5982 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5983 size_t words_survived = _surviving_young_words[index]; 5984 cur->record_surv_words_in_group(words_survived); 5985 5986 // At this point the we have 'popped' cur from the collection set 5987 // (linked via next_in_collection_set()) but it is still in the 5988 // young list (linked via next_young_region()). Clear the 5989 // _next_young_region field. 5990 cur->set_next_young_region(NULL); 5991 } else { 5992 int index = cur->young_index_in_cset(); 5993 assert(index == -1, "invariant"); 5994 } 5995 5996 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 5997 (!cur->is_young() && cur->young_index_in_cset() == -1), 5998 "invariant" ); 5999 6000 if (!cur->evacuation_failed()) { 6001 MemRegion used_mr = cur->used_region(); 6002 6003 // And the region is empty. 6004 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6005 free_region(cur, &pre_used, &local_free_list, false /* par */); 6006 } else { 6007 cur->uninstall_surv_rate_group(); 6008 if (cur->is_young()) { 6009 cur->set_young_index_in_cset(-1); 6010 } 6011 cur->set_not_young(); 6012 cur->set_evacuation_failed(false); 6013 // The region is now considered to be old. 6014 _old_set.add(cur); 6015 } 6016 cur = next; 6017 } 6018 6019 policy->record_max_rs_lengths(rs_lengths); 6020 policy->cset_regions_freed(); 6021 6022 double end_sec = os::elapsedTime(); 6023 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6024 6025 if (non_young) { 6026 non_young_time_ms += elapsed_ms; 6027 } else { 6028 young_time_ms += elapsed_ms; 6029 } 6030 6031 update_sets_after_freeing_regions(pre_used, &local_free_list, 6032 NULL /* old_proxy_set */, 6033 NULL /* humongous_proxy_set */, 6034 false /* par */); 6035 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6036 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6037 } 6038 6039 // This routine is similar to the above but does not record 6040 // any policy statistics or update free lists; we are abandoning 6041 // the current incremental collection set in preparation of a 6042 // full collection. After the full GC we will start to build up 6043 // the incremental collection set again. 6044 // This is only called when we're doing a full collection 6045 // and is immediately followed by the tearing down of the young list. 6046 6047 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6048 HeapRegion* cur = cs_head; 6049 6050 while (cur != NULL) { 6051 HeapRegion* next = cur->next_in_collection_set(); 6052 assert(cur->in_collection_set(), "bad CS"); 6053 cur->set_next_in_collection_set(NULL); 6054 cur->set_in_collection_set(false); 6055 cur->set_young_index_in_cset(-1); 6056 cur = next; 6057 } 6058 } 6059 6060 void G1CollectedHeap::set_free_regions_coming() { 6061 if (G1ConcRegionFreeingVerbose) { 6062 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6063 "setting free regions coming"); 6064 } 6065 6066 assert(!free_regions_coming(), "pre-condition"); 6067 _free_regions_coming = true; 6068 } 6069 6070 void G1CollectedHeap::reset_free_regions_coming() { 6071 assert(free_regions_coming(), "pre-condition"); 6072 6073 { 6074 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6075 _free_regions_coming = false; 6076 SecondaryFreeList_lock->notify_all(); 6077 } 6078 6079 if (G1ConcRegionFreeingVerbose) { 6080 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6081 "reset free regions coming"); 6082 } 6083 } 6084 6085 void G1CollectedHeap::wait_while_free_regions_coming() { 6086 // Most of the time we won't have to wait, so let's do a quick test 6087 // first before we take the lock. 6088 if (!free_regions_coming()) { 6089 return; 6090 } 6091 6092 if (G1ConcRegionFreeingVerbose) { 6093 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6094 "waiting for free regions"); 6095 } 6096 6097 { 6098 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6099 while (free_regions_coming()) { 6100 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6101 } 6102 } 6103 6104 if (G1ConcRegionFreeingVerbose) { 6105 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6106 "done waiting for free regions"); 6107 } 6108 } 6109 6110 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6111 assert(heap_lock_held_for_gc(), 6112 "the heap lock should already be held by or for this thread"); 6113 _young_list->push_region(hr); 6114 } 6115 6116 class NoYoungRegionsClosure: public HeapRegionClosure { 6117 private: 6118 bool _success; 6119 public: 6120 NoYoungRegionsClosure() : _success(true) { } 6121 bool doHeapRegion(HeapRegion* r) { 6122 if (r->is_young()) { 6123 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6124 r->bottom(), r->end()); 6125 _success = false; 6126 } 6127 return false; 6128 } 6129 bool success() { return _success; } 6130 }; 6131 6132 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6133 bool ret = _young_list->check_list_empty(check_sample); 6134 6135 if (check_heap) { 6136 NoYoungRegionsClosure closure; 6137 heap_region_iterate(&closure); 6138 ret = ret && closure.success(); 6139 } 6140 6141 return ret; 6142 } 6143 6144 class TearDownRegionSetsClosure : public HeapRegionClosure { 6145 private: 6146 OldRegionSet *_old_set; 6147 6148 public: 6149 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { } 6150 6151 bool doHeapRegion(HeapRegion* r) { 6152 if (r->is_empty()) { 6153 // We ignore empty regions, we'll empty the free list afterwards 6154 } else if (r->is_young()) { 6155 // We ignore young regions, we'll empty the young list afterwards 6156 } else if (r->isHumongous()) { 6157 // We ignore humongous regions, we're not tearing down the 6158 // humongous region set 6159 } else { 6160 // The rest should be old 6161 _old_set->remove(r); 6162 } 6163 return false; 6164 } 6165 6166 ~TearDownRegionSetsClosure() { 6167 assert(_old_set->is_empty(), "post-condition"); 6168 } 6169 }; 6170 6171 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6172 assert_at_safepoint(true /* should_be_vm_thread */); 6173 6174 if (!free_list_only) { 6175 TearDownRegionSetsClosure cl(&_old_set); 6176 heap_region_iterate(&cl); 6177 6178 // Need to do this after the heap iteration to be able to 6179 // recognize the young regions and ignore them during the iteration. 6180 _young_list->empty_list(); 6181 } 6182 _free_list.remove_all(); 6183 } 6184 6185 class RebuildRegionSetsClosure : public HeapRegionClosure { 6186 private: 6187 bool _free_list_only; 6188 OldRegionSet* _old_set; 6189 FreeRegionList* _free_list; 6190 size_t _total_used; 6191 6192 public: 6193 RebuildRegionSetsClosure(bool free_list_only, 6194 OldRegionSet* old_set, FreeRegionList* free_list) : 6195 _free_list_only(free_list_only), 6196 _old_set(old_set), _free_list(free_list), _total_used(0) { 6197 assert(_free_list->is_empty(), "pre-condition"); 6198 if (!free_list_only) { 6199 assert(_old_set->is_empty(), "pre-condition"); 6200 } 6201 } 6202 6203 bool doHeapRegion(HeapRegion* r) { 6204 if (r->continuesHumongous()) { 6205 return false; 6206 } 6207 6208 if (r->is_empty()) { 6209 // Add free regions to the free list 6210 _free_list->add_as_tail(r); 6211 } else if (!_free_list_only) { 6212 assert(!r->is_young(), "we should not come across young regions"); 6213 6214 if (r->isHumongous()) { 6215 // We ignore humongous regions, we left the humongous set unchanged 6216 } else { 6217 // The rest should be old, add them to the old set 6218 _old_set->add(r); 6219 } 6220 _total_used += r->used(); 6221 } 6222 6223 return false; 6224 } 6225 6226 size_t total_used() { 6227 return _total_used; 6228 } 6229 }; 6230 6231 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6232 assert_at_safepoint(true /* should_be_vm_thread */); 6233 6234 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list); 6235 heap_region_iterate(&cl); 6236 6237 if (!free_list_only) { 6238 _summary_bytes_used = cl.total_used(); 6239 } 6240 assert(_summary_bytes_used == recalculate_used(), 6241 err_msg("inconsistent _summary_bytes_used, " 6242 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6243 _summary_bytes_used, recalculate_used())); 6244 } 6245 6246 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6247 _refine_cte_cl->set_concurrent(concurrent); 6248 } 6249 6250 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6251 HeapRegion* hr = heap_region_containing(p); 6252 if (hr == NULL) { 6253 return false; 6254 } else { 6255 return hr->is_in(p); 6256 } 6257 } 6258 6259 // Methods for the mutator alloc region 6260 6261 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6262 bool force) { 6263 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6264 assert(!force || g1_policy()->can_expand_young_list(), 6265 "if force is true we should be able to expand the young list"); 6266 bool young_list_full = g1_policy()->is_young_list_full(); 6267 if (force || !young_list_full) { 6268 HeapRegion* new_alloc_region = new_region(word_size, 6269 false /* do_expand */); 6270 if (new_alloc_region != NULL) { 6271 set_region_short_lived_locked(new_alloc_region); 6272 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6273 return new_alloc_region; 6274 } 6275 } 6276 return NULL; 6277 } 6278 6279 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6280 size_t allocated_bytes) { 6281 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6282 assert(alloc_region->is_young(), "all mutator alloc regions should be young"); 6283 6284 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6285 _summary_bytes_used += allocated_bytes; 6286 _hr_printer.retire(alloc_region); 6287 // We update the eden sizes here, when the region is retired, 6288 // instead of when it's allocated, since this is the point that its 6289 // used space has been recored in _summary_bytes_used. 6290 g1mm()->update_eden_size(); 6291 } 6292 6293 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, 6294 bool force) { 6295 return _g1h->new_mutator_alloc_region(word_size, force); 6296 } 6297 6298 void G1CollectedHeap::set_par_threads() { 6299 // Don't change the number of workers. Use the value previously set 6300 // in the workgroup. 6301 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6302 uint n_workers = workers()->active_workers(); 6303 assert(UseDynamicNumberOfGCThreads || 6304 n_workers == workers()->total_workers(), 6305 "Otherwise should be using the total number of workers"); 6306 if (n_workers == 0) { 6307 assert(false, "Should have been set in prior evacuation pause."); 6308 n_workers = ParallelGCThreads; 6309 workers()->set_active_workers(n_workers); 6310 } 6311 set_par_threads(n_workers); 6312 } 6313 6314 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, 6315 size_t allocated_bytes) { 6316 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); 6317 } 6318 6319 // Methods for the GC alloc regions 6320 6321 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6322 uint count, 6323 GCAllocPurpose ap) { 6324 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6325 6326 if (count < g1_policy()->max_regions(ap)) { 6327 HeapRegion* new_alloc_region = new_region(word_size, 6328 true /* do_expand */); 6329 if (new_alloc_region != NULL) { 6330 // We really only need to do this for old regions given that we 6331 // should never scan survivors. But it doesn't hurt to do it 6332 // for survivors too. 6333 new_alloc_region->set_saved_mark(); 6334 if (ap == GCAllocForSurvived) { 6335 new_alloc_region->set_survivor(); 6336 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6337 } else { 6338 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6339 } 6340 bool during_im = g1_policy()->during_initial_mark_pause(); 6341 new_alloc_region->note_start_of_copying(during_im); 6342 return new_alloc_region; 6343 } else { 6344 g1_policy()->note_alloc_region_limit_reached(ap); 6345 } 6346 } 6347 return NULL; 6348 } 6349 6350 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6351 size_t allocated_bytes, 6352 GCAllocPurpose ap) { 6353 bool during_im = g1_policy()->during_initial_mark_pause(); 6354 alloc_region->note_end_of_copying(during_im); 6355 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6356 if (ap == GCAllocForSurvived) { 6357 young_list()->add_survivor_region(alloc_region); 6358 } else { 6359 _old_set.add(alloc_region); 6360 } 6361 _hr_printer.retire(alloc_region); 6362 } 6363 6364 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, 6365 bool force) { 6366 assert(!force, "not supported for GC alloc regions"); 6367 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); 6368 } 6369 6370 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, 6371 size_t allocated_bytes) { 6372 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6373 GCAllocForSurvived); 6374 } 6375 6376 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, 6377 bool force) { 6378 assert(!force, "not supported for GC alloc regions"); 6379 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); 6380 } 6381 6382 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, 6383 size_t allocated_bytes) { 6384 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6385 GCAllocForTenured); 6386 } 6387 // Heap region set verification 6388 6389 class VerifyRegionListsClosure : public HeapRegionClosure { 6390 private: 6391 FreeRegionList* _free_list; 6392 OldRegionSet* _old_set; 6393 HumongousRegionSet* _humongous_set; 6394 uint _region_count; 6395 6396 public: 6397 VerifyRegionListsClosure(OldRegionSet* old_set, 6398 HumongousRegionSet* humongous_set, 6399 FreeRegionList* free_list) : 6400 _old_set(old_set), _humongous_set(humongous_set), 6401 _free_list(free_list), _region_count(0) { } 6402 6403 uint region_count() { return _region_count; } 6404 6405 bool doHeapRegion(HeapRegion* hr) { 6406 _region_count += 1; 6407 6408 if (hr->continuesHumongous()) { 6409 return false; 6410 } 6411 6412 if (hr->is_young()) { 6413 // TODO 6414 } else if (hr->startsHumongous()) { 6415 _humongous_set->verify_next_region(hr); 6416 } else if (hr->is_empty()) { 6417 _free_list->verify_next_region(hr); 6418 } else { 6419 _old_set->verify_next_region(hr); 6420 } 6421 return false; 6422 } 6423 }; 6424 6425 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 6426 HeapWord* bottom) { 6427 HeapWord* end = bottom + HeapRegion::GrainWords; 6428 MemRegion mr(bottom, end); 6429 assert(_g1_reserved.contains(mr), "invariant"); 6430 // This might return NULL if the allocation fails 6431 return new HeapRegion(hrs_index, _bot_shared, mr); 6432 } 6433 6434 void G1CollectedHeap::verify_region_sets() { 6435 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6436 6437 // First, check the explicit lists. 6438 _free_list.verify(); 6439 { 6440 // Given that a concurrent operation might be adding regions to 6441 // the secondary free list we have to take the lock before 6442 // verifying it. 6443 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6444 _secondary_free_list.verify(); 6445 } 6446 _old_set.verify(); 6447 _humongous_set.verify(); 6448 6449 // If a concurrent region freeing operation is in progress it will 6450 // be difficult to correctly attributed any free regions we come 6451 // across to the correct free list given that they might belong to 6452 // one of several (free_list, secondary_free_list, any local lists, 6453 // etc.). So, if that's the case we will skip the rest of the 6454 // verification operation. Alternatively, waiting for the concurrent 6455 // operation to complete will have a non-trivial effect on the GC's 6456 // operation (no concurrent operation will last longer than the 6457 // interval between two calls to verification) and it might hide 6458 // any issues that we would like to catch during testing. 6459 if (free_regions_coming()) { 6460 return; 6461 } 6462 6463 // Make sure we append the secondary_free_list on the free_list so 6464 // that all free regions we will come across can be safely 6465 // attributed to the free_list. 6466 append_secondary_free_list_if_not_empty_with_lock(); 6467 6468 // Finally, make sure that the region accounting in the lists is 6469 // consistent with what we see in the heap. 6470 _old_set.verify_start(); 6471 _humongous_set.verify_start(); 6472 _free_list.verify_start(); 6473 6474 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list); 6475 heap_region_iterate(&cl); 6476 6477 _old_set.verify_end(); 6478 _humongous_set.verify_end(); 6479 _free_list.verify_end(); 6480 }