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->refine_card(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 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1456 if (hot_card_cache->use_cache()) { 1457 hot_card_cache->reset_card_counts(); 1458 hot_card_cache->reset_hot_cache(); 1459 } 1460 1461 // Rebuild remembered sets of all regions. 1462 if (G1CollectedHeap::use_parallel_gc_threads()) { 1463 uint n_workers = 1464 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1465 workers()->active_workers(), 1466 Threads::number_of_non_daemon_threads()); 1467 assert(UseDynamicNumberOfGCThreads || 1468 n_workers == workers()->total_workers(), 1469 "If not dynamic should be using all the workers"); 1470 workers()->set_active_workers(n_workers); 1471 // Set parallel threads in the heap (_n_par_threads) only 1472 // before a parallel phase and always reset it to 0 after 1473 // the phase so that the number of parallel threads does 1474 // no get carried forward to a serial phase where there 1475 // may be code that is "possibly_parallel". 1476 set_par_threads(n_workers); 1477 1478 ParRebuildRSTask rebuild_rs_task(this); 1479 assert(check_heap_region_claim_values( 1480 HeapRegion::InitialClaimValue), "sanity check"); 1481 assert(UseDynamicNumberOfGCThreads || 1482 workers()->active_workers() == workers()->total_workers(), 1483 "Unless dynamic should use total workers"); 1484 // Use the most recent number of active workers 1485 assert(workers()->active_workers() > 0, 1486 "Active workers not properly set"); 1487 set_par_threads(workers()->active_workers()); 1488 workers()->run_task(&rebuild_rs_task); 1489 set_par_threads(0); 1490 assert(check_heap_region_claim_values( 1491 HeapRegion::RebuildRSClaimValue), "sanity check"); 1492 reset_heap_region_claim_values(); 1493 } else { 1494 RebuildRSOutOfRegionClosure rebuild_rs(this); 1495 heap_region_iterate(&rebuild_rs); 1496 } 1497 1498 if (true) { // FIXME 1499 MetaspaceGC::compute_new_size(); 1500 } 1501 1502 #ifdef TRACESPINNING 1503 ParallelTaskTerminator::print_termination_counts(); 1504 #endif 1505 1506 // Discard all rset updates 1507 JavaThread::dirty_card_queue_set().abandon_logs(); 1508 assert(!G1DeferredRSUpdate 1509 || (G1DeferredRSUpdate && 1510 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); 1511 1512 _young_list->reset_sampled_info(); 1513 // At this point there should be no regions in the 1514 // entire heap tagged as young. 1515 assert(check_young_list_empty(true /* check_heap */), 1516 "young list should be empty at this point"); 1517 1518 // Update the number of full collections that have been completed. 1519 increment_old_marking_cycles_completed(false /* concurrent */); 1520 1521 _hrs.verify_optional(); 1522 verify_region_sets_optional(); 1523 1524 // Start a new incremental collection set for the next pause 1525 assert(g1_policy()->collection_set() == NULL, "must be"); 1526 g1_policy()->start_incremental_cset_building(); 1527 1528 // Clear the _cset_fast_test bitmap in anticipation of adding 1529 // regions to the incremental collection set for the next 1530 // evacuation pause. 1531 clear_cset_fast_test(); 1532 1533 init_mutator_alloc_region(); 1534 1535 double end = os::elapsedTime(); 1536 g1_policy()->record_full_collection_end(); 1537 1538 if (G1Log::fine()) { 1539 g1_policy()->print_heap_transition(); 1540 } 1541 1542 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1543 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1544 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1545 // before any GC notifications are raised. 1546 g1mm()->update_sizes(); 1547 1548 gc_epilogue(true); 1549 } 1550 1551 if (G1Log::finer()) { 1552 g1_policy()->print_detailed_heap_transition(true /* full */); 1553 } 1554 1555 print_heap_after_gc(); 1556 1557 post_full_gc_dump(); 1558 } 1559 1560 return true; 1561 } 1562 1563 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1564 // do_collection() will return whether it succeeded in performing 1565 // the GC. Currently, there is no facility on the 1566 // do_full_collection() API to notify the caller than the collection 1567 // did not succeed (e.g., because it was locked out by the GC 1568 // locker). So, right now, we'll ignore the return value. 1569 bool dummy = do_collection(true, /* explicit_gc */ 1570 clear_all_soft_refs, 1571 0 /* word_size */); 1572 } 1573 1574 // This code is mostly copied from TenuredGeneration. 1575 void 1576 G1CollectedHeap:: 1577 resize_if_necessary_after_full_collection(size_t word_size) { 1578 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check"); 1579 1580 // Include the current allocation, if any, and bytes that will be 1581 // pre-allocated to support collections, as "used". 1582 const size_t used_after_gc = used(); 1583 const size_t capacity_after_gc = capacity(); 1584 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1585 1586 // This is enforced in arguments.cpp. 1587 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1588 "otherwise the code below doesn't make sense"); 1589 1590 // We don't have floating point command-line arguments 1591 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1592 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1593 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1594 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1595 1596 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1597 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1598 1599 // We have to be careful here as these two calculations can overflow 1600 // 32-bit size_t's. 1601 double used_after_gc_d = (double) used_after_gc; 1602 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1603 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1604 1605 // Let's make sure that they are both under the max heap size, which 1606 // by default will make them fit into a size_t. 1607 double desired_capacity_upper_bound = (double) max_heap_size; 1608 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1609 desired_capacity_upper_bound); 1610 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1611 desired_capacity_upper_bound); 1612 1613 // We can now safely turn them into size_t's. 1614 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1615 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1616 1617 // This assert only makes sense here, before we adjust them 1618 // with respect to the min and max heap size. 1619 assert(minimum_desired_capacity <= maximum_desired_capacity, 1620 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1621 "maximum_desired_capacity = "SIZE_FORMAT, 1622 minimum_desired_capacity, maximum_desired_capacity)); 1623 1624 // Should not be greater than the heap max size. No need to adjust 1625 // it with respect to the heap min size as it's a lower bound (i.e., 1626 // we'll try to make the capacity larger than it, not smaller). 1627 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1628 // Should not be less than the heap min size. No need to adjust it 1629 // with respect to the heap max size as it's an upper bound (i.e., 1630 // we'll try to make the capacity smaller than it, not greater). 1631 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1632 1633 if (capacity_after_gc < minimum_desired_capacity) { 1634 // Don't expand unless it's significant 1635 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1636 ergo_verbose4(ErgoHeapSizing, 1637 "attempt heap expansion", 1638 ergo_format_reason("capacity lower than " 1639 "min desired capacity after Full GC") 1640 ergo_format_byte("capacity") 1641 ergo_format_byte("occupancy") 1642 ergo_format_byte_perc("min desired capacity"), 1643 capacity_after_gc, used_after_gc, 1644 minimum_desired_capacity, (double) MinHeapFreeRatio); 1645 expand(expand_bytes); 1646 1647 // No expansion, now see if we want to shrink 1648 } else if (capacity_after_gc > maximum_desired_capacity) { 1649 // Capacity too large, compute shrinking size 1650 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1651 ergo_verbose4(ErgoHeapSizing, 1652 "attempt heap shrinking", 1653 ergo_format_reason("capacity higher than " 1654 "max desired capacity after Full GC") 1655 ergo_format_byte("capacity") 1656 ergo_format_byte("occupancy") 1657 ergo_format_byte_perc("max desired capacity"), 1658 capacity_after_gc, used_after_gc, 1659 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1660 shrink(shrink_bytes); 1661 } 1662 } 1663 1664 1665 HeapWord* 1666 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1667 bool* succeeded) { 1668 assert_at_safepoint(true /* should_be_vm_thread */); 1669 1670 *succeeded = true; 1671 // Let's attempt the allocation first. 1672 HeapWord* result = 1673 attempt_allocation_at_safepoint(word_size, 1674 false /* expect_null_mutator_alloc_region */); 1675 if (result != NULL) { 1676 assert(*succeeded, "sanity"); 1677 return result; 1678 } 1679 1680 // In a G1 heap, we're supposed to keep allocation from failing by 1681 // incremental pauses. Therefore, at least for now, we'll favor 1682 // expansion over collection. (This might change in the future if we can 1683 // do something smarter than full collection to satisfy a failed alloc.) 1684 result = expand_and_allocate(word_size); 1685 if (result != NULL) { 1686 assert(*succeeded, "sanity"); 1687 return result; 1688 } 1689 1690 // Expansion didn't work, we'll try to do a Full GC. 1691 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1692 false, /* clear_all_soft_refs */ 1693 word_size); 1694 if (!gc_succeeded) { 1695 *succeeded = false; 1696 return NULL; 1697 } 1698 1699 // Retry the allocation 1700 result = attempt_allocation_at_safepoint(word_size, 1701 true /* expect_null_mutator_alloc_region */); 1702 if (result != NULL) { 1703 assert(*succeeded, "sanity"); 1704 return result; 1705 } 1706 1707 // Then, try a Full GC that will collect all soft references. 1708 gc_succeeded = do_collection(false, /* explicit_gc */ 1709 true, /* clear_all_soft_refs */ 1710 word_size); 1711 if (!gc_succeeded) { 1712 *succeeded = false; 1713 return NULL; 1714 } 1715 1716 // Retry the allocation once more 1717 result = attempt_allocation_at_safepoint(word_size, 1718 true /* expect_null_mutator_alloc_region */); 1719 if (result != NULL) { 1720 assert(*succeeded, "sanity"); 1721 return result; 1722 } 1723 1724 assert(!collector_policy()->should_clear_all_soft_refs(), 1725 "Flag should have been handled and cleared prior to this point"); 1726 1727 // What else? We might try synchronous finalization later. If the total 1728 // space available is large enough for the allocation, then a more 1729 // complete compaction phase than we've tried so far might be 1730 // appropriate. 1731 assert(*succeeded, "sanity"); 1732 return NULL; 1733 } 1734 1735 // Attempting to expand the heap sufficiently 1736 // to support an allocation of the given "word_size". If 1737 // successful, perform the allocation and return the address of the 1738 // allocated block, or else "NULL". 1739 1740 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1741 assert_at_safepoint(true /* should_be_vm_thread */); 1742 1743 verify_region_sets_optional(); 1744 1745 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1746 ergo_verbose1(ErgoHeapSizing, 1747 "attempt heap expansion", 1748 ergo_format_reason("allocation request failed") 1749 ergo_format_byte("allocation request"), 1750 word_size * HeapWordSize); 1751 if (expand(expand_bytes)) { 1752 _hrs.verify_optional(); 1753 verify_region_sets_optional(); 1754 return attempt_allocation_at_safepoint(word_size, 1755 false /* expect_null_mutator_alloc_region */); 1756 } 1757 return NULL; 1758 } 1759 1760 void G1CollectedHeap::update_committed_space(HeapWord* old_end, 1761 HeapWord* new_end) { 1762 assert(old_end != new_end, "don't call this otherwise"); 1763 assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); 1764 1765 // Update the committed mem region. 1766 _g1_committed.set_end(new_end); 1767 // Tell the card table about the update. 1768 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); 1769 // Tell the BOT about the update. 1770 _bot_shared->resize(_g1_committed.word_size()); 1771 // Tell the hot card cache about the update 1772 _cg1r->hot_card_cache()->resize_card_counts(capacity()); 1773 } 1774 1775 bool G1CollectedHeap::expand(size_t expand_bytes) { 1776 size_t old_mem_size = _g1_storage.committed_size(); 1777 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1778 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1779 HeapRegion::GrainBytes); 1780 ergo_verbose2(ErgoHeapSizing, 1781 "expand the heap", 1782 ergo_format_byte("requested expansion amount") 1783 ergo_format_byte("attempted expansion amount"), 1784 expand_bytes, aligned_expand_bytes); 1785 1786 // First commit the memory. 1787 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1788 bool successful = _g1_storage.expand_by(aligned_expand_bytes); 1789 if (successful) { 1790 // Then propagate this update to the necessary data structures. 1791 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1792 update_committed_space(old_end, new_end); 1793 1794 FreeRegionList expansion_list("Local Expansion List"); 1795 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); 1796 assert(mr.start() == old_end, "post-condition"); 1797 // mr might be a smaller region than what was requested if 1798 // expand_by() was unable to allocate the HeapRegion instances 1799 assert(mr.end() <= new_end, "post-condition"); 1800 1801 size_t actual_expand_bytes = mr.byte_size(); 1802 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1803 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), 1804 "post-condition"); 1805 if (actual_expand_bytes < aligned_expand_bytes) { 1806 // We could not expand _hrs to the desired size. In this case we 1807 // need to shrink the committed space accordingly. 1808 assert(mr.end() < new_end, "invariant"); 1809 1810 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; 1811 // First uncommit the memory. 1812 _g1_storage.shrink_by(diff_bytes); 1813 // Then propagate this update to the necessary data structures. 1814 update_committed_space(new_end, mr.end()); 1815 } 1816 _free_list.add_as_tail(&expansion_list); 1817 1818 if (_hr_printer.is_active()) { 1819 HeapWord* curr = mr.start(); 1820 while (curr < mr.end()) { 1821 HeapWord* curr_end = curr + HeapRegion::GrainWords; 1822 _hr_printer.commit(curr, curr_end); 1823 curr = curr_end; 1824 } 1825 assert(curr == mr.end(), "post-condition"); 1826 } 1827 g1_policy()->record_new_heap_size(n_regions()); 1828 } else { 1829 ergo_verbose0(ErgoHeapSizing, 1830 "did not expand the heap", 1831 ergo_format_reason("heap expansion operation failed")); 1832 // The expansion of the virtual storage space was unsuccessful. 1833 // Let's see if it was because we ran out of swap. 1834 if (G1ExitOnExpansionFailure && 1835 _g1_storage.uncommitted_size() >= aligned_expand_bytes) { 1836 // We had head room... 1837 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1838 } 1839 } 1840 return successful; 1841 } 1842 1843 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1844 size_t old_mem_size = _g1_storage.committed_size(); 1845 size_t aligned_shrink_bytes = 1846 ReservedSpace::page_align_size_down(shrink_bytes); 1847 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1848 HeapRegion::GrainBytes); 1849 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1850 1851 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove); 1852 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1853 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1854 1855 ergo_verbose3(ErgoHeapSizing, 1856 "shrink the heap", 1857 ergo_format_byte("requested shrinking amount") 1858 ergo_format_byte("aligned shrinking amount") 1859 ergo_format_byte("attempted shrinking amount"), 1860 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1861 if (num_regions_removed > 0) { 1862 _g1_storage.shrink_by(shrunk_bytes); 1863 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1864 1865 if (_hr_printer.is_active()) { 1866 HeapWord* curr = old_end; 1867 while (curr > new_end) { 1868 HeapWord* curr_end = curr; 1869 curr -= HeapRegion::GrainWords; 1870 _hr_printer.uncommit(curr, curr_end); 1871 } 1872 } 1873 1874 _expansion_regions += num_regions_removed; 1875 update_committed_space(old_end, new_end); 1876 HeapRegionRemSet::shrink_heap(n_regions()); 1877 g1_policy()->record_new_heap_size(n_regions()); 1878 } else { 1879 ergo_verbose0(ErgoHeapSizing, 1880 "did not shrink the heap", 1881 ergo_format_reason("heap shrinking operation failed")); 1882 } 1883 } 1884 1885 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1886 verify_region_sets_optional(); 1887 1888 // We should only reach here at the end of a Full GC which means we 1889 // should not not be holding to any GC alloc regions. The method 1890 // below will make sure of that and do any remaining clean up. 1891 abandon_gc_alloc_regions(); 1892 1893 // Instead of tearing down / rebuilding the free lists here, we 1894 // could instead use the remove_all_pending() method on free_list to 1895 // remove only the ones that we need to remove. 1896 tear_down_region_sets(true /* free_list_only */); 1897 shrink_helper(shrink_bytes); 1898 rebuild_region_sets(true /* free_list_only */); 1899 1900 _hrs.verify_optional(); 1901 verify_region_sets_optional(); 1902 } 1903 1904 // Public methods. 1905 1906 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1907 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1908 #endif // _MSC_VER 1909 1910 1911 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1912 SharedHeap(policy_), 1913 _g1_policy(policy_), 1914 _dirty_card_queue_set(false), 1915 _into_cset_dirty_card_queue_set(false), 1916 _is_alive_closure_cm(this), 1917 _is_alive_closure_stw(this), 1918 _ref_processor_cm(NULL), 1919 _ref_processor_stw(NULL), 1920 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1921 _bot_shared(NULL), 1922 _evac_failure_scan_stack(NULL) , 1923 _mark_in_progress(false), 1924 _cg1r(NULL), _summary_bytes_used(0), 1925 _g1mm(NULL), 1926 _refine_cte_cl(NULL), 1927 _full_collection(false), 1928 _free_list("Master Free List"), 1929 _secondary_free_list("Secondary Free List"), 1930 _old_set("Old Set"), 1931 _humongous_set("Master Humongous Set"), 1932 _free_regions_coming(false), 1933 _young_list(new YoungList(this)), 1934 _gc_time_stamp(0), 1935 _retained_old_gc_alloc_region(NULL), 1936 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1937 _old_plab_stats(OldPLABSize, PLABWeight), 1938 _expand_heap_after_alloc_failure(true), 1939 _surviving_young_words(NULL), 1940 _old_marking_cycles_started(0), 1941 _old_marking_cycles_completed(0), 1942 _in_cset_fast_test(NULL), 1943 _in_cset_fast_test_base(NULL), 1944 _dirty_cards_region_list(NULL), 1945 _worker_cset_start_region(NULL), 1946 _worker_cset_start_region_time_stamp(NULL) { 1947 _g1h = this; // To catch bugs. 1948 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1949 vm_exit_during_initialization("Failed necessary allocation."); 1950 } 1951 1952 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1953 1954 int n_queues = MAX2((int)ParallelGCThreads, 1); 1955 _task_queues = new RefToScanQueueSet(n_queues); 1956 1957 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1958 assert(n_rem_sets > 0, "Invariant."); 1959 1960 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1961 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1962 1963 for (int i = 0; i < n_queues; i++) { 1964 RefToScanQueue* q = new RefToScanQueue(); 1965 q->initialize(); 1966 _task_queues->register_queue(i, q); 1967 } 1968 1969 clear_cset_start_regions(); 1970 1971 // Initialize the G1EvacuationFailureALot counters and flags. 1972 NOT_PRODUCT(reset_evacuation_should_fail();) 1973 1974 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1975 } 1976 1977 jint G1CollectedHeap::initialize() { 1978 CollectedHeap::pre_initialize(); 1979 os::enable_vtime(); 1980 1981 G1Log::init(); 1982 1983 // Necessary to satisfy locking discipline assertions. 1984 1985 MutexLocker x(Heap_lock); 1986 1987 // We have to initialize the printer before committing the heap, as 1988 // it will be used then. 1989 _hr_printer.set_active(G1PrintHeapRegions); 1990 1991 // While there are no constraints in the GC code that HeapWordSize 1992 // be any particular value, there are multiple other areas in the 1993 // system which believe this to be true (e.g. oop->object_size in some 1994 // cases incorrectly returns the size in wordSize units rather than 1995 // HeapWordSize). 1996 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1997 1998 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1999 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 2000 2001 // Ensure that the sizes are properly aligned. 2002 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2003 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2004 2005 _cg1r = new ConcurrentG1Refine(this); 2006 2007 // Reserve the maximum. 2008 2009 // When compressed oops are enabled, the preferred heap base 2010 // is calculated by subtracting the requested size from the 2011 // 32Gb boundary and using the result as the base address for 2012 // heap reservation. If the requested size is not aligned to 2013 // HeapRegion::GrainBytes (i.e. the alignment that is passed 2014 // into the ReservedHeapSpace constructor) then the actual 2015 // base of the reserved heap may end up differing from the 2016 // address that was requested (i.e. the preferred heap base). 2017 // If this happens then we could end up using a non-optimal 2018 // compressed oops mode. 2019 2020 // Since max_byte_size is aligned to the size of a heap region (checked 2021 // above). 2022 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2023 2024 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 2025 HeapRegion::GrainBytes); 2026 2027 // It is important to do this in a way such that concurrent readers can't 2028 // temporarily think somethings in the heap. (I've actually seen this 2029 // happen in asserts: DLD.) 2030 _reserved.set_word_size(0); 2031 _reserved.set_start((HeapWord*)heap_rs.base()); 2032 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 2033 2034 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes); 2035 2036 // Create the gen rem set (and barrier set) for the entire reserved region. 2037 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 2038 set_barrier_set(rem_set()->bs()); 2039 if (barrier_set()->is_a(BarrierSet::ModRef)) { 2040 _mr_bs = (ModRefBarrierSet*)_barrier_set; 2041 } else { 2042 vm_exit_during_initialization("G1 requires a mod ref bs."); 2043 return JNI_ENOMEM; 2044 } 2045 2046 // Also create a G1 rem set. 2047 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) { 2048 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs()); 2049 } else { 2050 vm_exit_during_initialization("G1 requires a cardtable mod ref bs."); 2051 return JNI_ENOMEM; 2052 } 2053 2054 // Carve out the G1 part of the heap. 2055 2056 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 2057 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), 2058 g1_rs.size()/HeapWordSize); 2059 2060 _g1_storage.initialize(g1_rs, 0); 2061 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); 2062 _hrs.initialize((HeapWord*) _g1_reserved.start(), 2063 (HeapWord*) _g1_reserved.end(), 2064 _expansion_regions); 2065 2066 // Do later initialization work for concurrent refinement. 2067 _cg1r->init(); 2068 2069 // 6843694 - ensure that the maximum region index can fit 2070 // in the remembered set structures. 2071 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2072 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2073 2074 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2075 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2076 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2077 "too many cards per region"); 2078 2079 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1); 2080 2081 _bot_shared = new G1BlockOffsetSharedArray(_reserved, 2082 heap_word_size(init_byte_size)); 2083 2084 _g1h = this; 2085 2086 _in_cset_fast_test_length = max_regions(); 2087 _in_cset_fast_test_base = 2088 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC); 2089 2090 // We're biasing _in_cset_fast_test to avoid subtracting the 2091 // beginning of the heap every time we want to index; basically 2092 // it's the same with what we do with the card table. 2093 _in_cset_fast_test = _in_cset_fast_test_base - 2094 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes); 2095 2096 // Clear the _cset_fast_test bitmap in anticipation of adding 2097 // regions to the incremental collection set for the first 2098 // evacuation pause. 2099 clear_cset_fast_test(); 2100 2101 // Create the ConcurrentMark data structure and thread. 2102 // (Must do this late, so that "max_regions" is defined.) 2103 _cm = new ConcurrentMark(this, heap_rs); 2104 if (_cm == NULL || !_cm->completed_initialization()) { 2105 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2106 return JNI_ENOMEM; 2107 } 2108 _cmThread = _cm->cmThread(); 2109 2110 // Initialize the from_card cache structure of HeapRegionRemSet. 2111 HeapRegionRemSet::init_heap(max_regions()); 2112 2113 // Now expand into the initial heap size. 2114 if (!expand(init_byte_size)) { 2115 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2116 return JNI_ENOMEM; 2117 } 2118 2119 // Perform any initialization actions delegated to the policy. 2120 g1_policy()->init(); 2121 2122 _refine_cte_cl = 2123 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(), 2124 g1_rem_set(), 2125 concurrent_g1_refine()); 2126 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 2127 2128 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2129 SATB_Q_FL_lock, 2130 G1SATBProcessCompletedThreshold, 2131 Shared_SATB_Q_lock); 2132 2133 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2134 DirtyCardQ_FL_lock, 2135 concurrent_g1_refine()->yellow_zone(), 2136 concurrent_g1_refine()->red_zone(), 2137 Shared_DirtyCardQ_lock); 2138 2139 if (G1DeferredRSUpdate) { 2140 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2141 DirtyCardQ_FL_lock, 2142 -1, // never trigger processing 2143 -1, // no limit on length 2144 Shared_DirtyCardQ_lock, 2145 &JavaThread::dirty_card_queue_set()); 2146 } 2147 2148 // Initialize the card queue set used to hold cards containing 2149 // references into the collection set. 2150 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon, 2151 DirtyCardQ_FL_lock, 2152 -1, // never trigger processing 2153 -1, // no limit on length 2154 Shared_DirtyCardQ_lock, 2155 &JavaThread::dirty_card_queue_set()); 2156 2157 // In case we're keeping closure specialization stats, initialize those 2158 // counts and that mechanism. 2159 SpecializationStats::clear(); 2160 2161 // Here we allocate the dummy full region that is required by the 2162 // G1AllocRegion class. If we don't pass an address in the reserved 2163 // space here, lots of asserts fire. 2164 2165 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, 2166 _g1_reserved.start()); 2167 // We'll re-use the same region whether the alloc region will 2168 // require BOT updates or not and, if it doesn't, then a non-young 2169 // region will complain that it cannot support allocations without 2170 // BOT updates. So we'll tag the dummy region as young to avoid that. 2171 dummy_region->set_young(); 2172 // Make sure it's full. 2173 dummy_region->set_top(dummy_region->end()); 2174 G1AllocRegion::setup(this, dummy_region); 2175 2176 init_mutator_alloc_region(); 2177 2178 // Do create of the monitoring and management support so that 2179 // values in the heap have been properly initialized. 2180 _g1mm = new G1MonitoringSupport(this); 2181 2182 return JNI_OK; 2183 } 2184 2185 void G1CollectedHeap::ref_processing_init() { 2186 // Reference processing in G1 currently works as follows: 2187 // 2188 // * There are two reference processor instances. One is 2189 // used to record and process discovered references 2190 // during concurrent marking; the other is used to 2191 // record and process references during STW pauses 2192 // (both full and incremental). 2193 // * Both ref processors need to 'span' the entire heap as 2194 // the regions in the collection set may be dotted around. 2195 // 2196 // * For the concurrent marking ref processor: 2197 // * Reference discovery is enabled at initial marking. 2198 // * Reference discovery is disabled and the discovered 2199 // references processed etc during remarking. 2200 // * Reference discovery is MT (see below). 2201 // * Reference discovery requires a barrier (see below). 2202 // * Reference processing may or may not be MT 2203 // (depending on the value of ParallelRefProcEnabled 2204 // and ParallelGCThreads). 2205 // * A full GC disables reference discovery by the CM 2206 // ref processor and abandons any entries on it's 2207 // discovered lists. 2208 // 2209 // * For the STW processor: 2210 // * Non MT discovery is enabled at the start of a full GC. 2211 // * Processing and enqueueing during a full GC is non-MT. 2212 // * During a full GC, references are processed after marking. 2213 // 2214 // * Discovery (may or may not be MT) is enabled at the start 2215 // of an incremental evacuation pause. 2216 // * References are processed near the end of a STW evacuation pause. 2217 // * For both types of GC: 2218 // * Discovery is atomic - i.e. not concurrent. 2219 // * Reference discovery will not need a barrier. 2220 2221 SharedHeap::ref_processing_init(); 2222 MemRegion mr = reserved_region(); 2223 2224 // Concurrent Mark ref processor 2225 _ref_processor_cm = 2226 new ReferenceProcessor(mr, // span 2227 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2228 // mt processing 2229 (int) ParallelGCThreads, 2230 // degree of mt processing 2231 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2232 // mt discovery 2233 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2234 // degree of mt discovery 2235 false, 2236 // Reference discovery is not atomic 2237 &_is_alive_closure_cm, 2238 // is alive closure 2239 // (for efficiency/performance) 2240 true); 2241 // Setting next fields of discovered 2242 // lists requires a barrier. 2243 2244 // STW ref processor 2245 _ref_processor_stw = 2246 new ReferenceProcessor(mr, // span 2247 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2248 // mt processing 2249 MAX2((int)ParallelGCThreads, 1), 2250 // degree of mt processing 2251 (ParallelGCThreads > 1), 2252 // mt discovery 2253 MAX2((int)ParallelGCThreads, 1), 2254 // degree of mt discovery 2255 true, 2256 // Reference discovery is atomic 2257 &_is_alive_closure_stw, 2258 // is alive closure 2259 // (for efficiency/performance) 2260 false); 2261 // Setting next fields of discovered 2262 // lists requires a barrier. 2263 } 2264 2265 size_t G1CollectedHeap::capacity() const { 2266 return _g1_committed.byte_size(); 2267 } 2268 2269 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2270 assert(!hr->continuesHumongous(), "pre-condition"); 2271 hr->reset_gc_time_stamp(); 2272 if (hr->startsHumongous()) { 2273 uint first_index = hr->hrs_index() + 1; 2274 uint last_index = hr->last_hc_index(); 2275 for (uint i = first_index; i < last_index; i += 1) { 2276 HeapRegion* chr = region_at(i); 2277 assert(chr->continuesHumongous(), "sanity"); 2278 chr->reset_gc_time_stamp(); 2279 } 2280 } 2281 } 2282 2283 #ifndef PRODUCT 2284 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2285 private: 2286 unsigned _gc_time_stamp; 2287 bool _failures; 2288 2289 public: 2290 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2291 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2292 2293 virtual bool doHeapRegion(HeapRegion* hr) { 2294 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2295 if (_gc_time_stamp != region_gc_time_stamp) { 2296 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2297 "expected %d", HR_FORMAT_PARAMS(hr), 2298 region_gc_time_stamp, _gc_time_stamp); 2299 _failures = true; 2300 } 2301 return false; 2302 } 2303 2304 bool failures() { return _failures; } 2305 }; 2306 2307 void G1CollectedHeap::check_gc_time_stamps() { 2308 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2309 heap_region_iterate(&cl); 2310 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2311 } 2312 #endif // PRODUCT 2313 2314 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2315 DirtyCardQueue* into_cset_dcq, 2316 bool concurrent, 2317 int worker_i) { 2318 // Clean cards in the hot card cache 2319 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2320 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2321 2322 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2323 int n_completed_buffers = 0; 2324 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2325 n_completed_buffers++; 2326 } 2327 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2328 dcqs.clear_n_completed_buffers(); 2329 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2330 } 2331 2332 2333 // Computes the sum of the storage used by the various regions. 2334 2335 size_t G1CollectedHeap::used() const { 2336 assert(Heap_lock->owner() != NULL, 2337 "Should be owned on this thread's behalf."); 2338 size_t result = _summary_bytes_used; 2339 // Read only once in case it is set to NULL concurrently 2340 HeapRegion* hr = _mutator_alloc_region.get(); 2341 if (hr != NULL) 2342 result += hr->used(); 2343 return result; 2344 } 2345 2346 size_t G1CollectedHeap::used_unlocked() const { 2347 size_t result = _summary_bytes_used; 2348 return result; 2349 } 2350 2351 class SumUsedClosure: public HeapRegionClosure { 2352 size_t _used; 2353 public: 2354 SumUsedClosure() : _used(0) {} 2355 bool doHeapRegion(HeapRegion* r) { 2356 if (!r->continuesHumongous()) { 2357 _used += r->used(); 2358 } 2359 return false; 2360 } 2361 size_t result() { return _used; } 2362 }; 2363 2364 size_t G1CollectedHeap::recalculate_used() const { 2365 SumUsedClosure blk; 2366 heap_region_iterate(&blk); 2367 return blk.result(); 2368 } 2369 2370 size_t G1CollectedHeap::unsafe_max_alloc() { 2371 if (free_regions() > 0) return HeapRegion::GrainBytes; 2372 // otherwise, is there space in the current allocation region? 2373 2374 // We need to store the current allocation region in a local variable 2375 // here. The problem is that this method doesn't take any locks and 2376 // there may be other threads which overwrite the current allocation 2377 // region field. attempt_allocation(), for example, sets it to NULL 2378 // and this can happen *after* the NULL check here but before the call 2379 // to free(), resulting in a SIGSEGV. Note that this doesn't appear 2380 // to be a problem in the optimized build, since the two loads of the 2381 // current allocation region field are optimized away. 2382 HeapRegion* hr = _mutator_alloc_region.get(); 2383 if (hr == NULL) { 2384 return 0; 2385 } 2386 return hr->free(); 2387 } 2388 2389 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2390 switch (cause) { 2391 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2392 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2393 case GCCause::_g1_humongous_allocation: return true; 2394 default: return false; 2395 } 2396 } 2397 2398 #ifndef PRODUCT 2399 void G1CollectedHeap::allocate_dummy_regions() { 2400 // Let's fill up most of the region 2401 size_t word_size = HeapRegion::GrainWords - 1024; 2402 // And as a result the region we'll allocate will be humongous. 2403 guarantee(isHumongous(word_size), "sanity"); 2404 2405 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2406 // Let's use the existing mechanism for the allocation 2407 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2408 if (dummy_obj != NULL) { 2409 MemRegion mr(dummy_obj, word_size); 2410 CollectedHeap::fill_with_object(mr); 2411 } else { 2412 // If we can't allocate once, we probably cannot allocate 2413 // again. Let's get out of the loop. 2414 break; 2415 } 2416 } 2417 } 2418 #endif // !PRODUCT 2419 2420 void G1CollectedHeap::increment_old_marking_cycles_started() { 2421 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2422 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2423 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2424 _old_marking_cycles_started, _old_marking_cycles_completed)); 2425 2426 _old_marking_cycles_started++; 2427 } 2428 2429 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2430 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2431 2432 // We assume that if concurrent == true, then the caller is a 2433 // concurrent thread that was joined the Suspendible Thread 2434 // Set. If there's ever a cheap way to check this, we should add an 2435 // assert here. 2436 2437 // Given that this method is called at the end of a Full GC or of a 2438 // concurrent cycle, and those can be nested (i.e., a Full GC can 2439 // interrupt a concurrent cycle), the number of full collections 2440 // completed should be either one (in the case where there was no 2441 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2442 // behind the number of full collections started. 2443 2444 // This is the case for the inner caller, i.e. a Full GC. 2445 assert(concurrent || 2446 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2447 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2448 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2449 "is inconsistent with _old_marking_cycles_completed = %u", 2450 _old_marking_cycles_started, _old_marking_cycles_completed)); 2451 2452 // This is the case for the outer caller, i.e. the concurrent cycle. 2453 assert(!concurrent || 2454 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2455 err_msg("for outer caller (concurrent cycle): " 2456 "_old_marking_cycles_started = %u " 2457 "is inconsistent with _old_marking_cycles_completed = %u", 2458 _old_marking_cycles_started, _old_marking_cycles_completed)); 2459 2460 _old_marking_cycles_completed += 1; 2461 2462 // We need to clear the "in_progress" flag in the CM thread before 2463 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2464 // is set) so that if a waiter requests another System.gc() it doesn't 2465 // incorrectly see that a marking cyle is still in progress. 2466 if (concurrent) { 2467 _cmThread->clear_in_progress(); 2468 } 2469 2470 // This notify_all() will ensure that a thread that called 2471 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2472 // and it's waiting for a full GC to finish will be woken up. It is 2473 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2474 FullGCCount_lock->notify_all(); 2475 } 2476 2477 void G1CollectedHeap::collect(GCCause::Cause cause) { 2478 assert_heap_not_locked(); 2479 2480 unsigned int gc_count_before; 2481 unsigned int old_marking_count_before; 2482 bool retry_gc; 2483 2484 do { 2485 retry_gc = false; 2486 2487 { 2488 MutexLocker ml(Heap_lock); 2489 2490 // Read the GC count while holding the Heap_lock 2491 gc_count_before = total_collections(); 2492 old_marking_count_before = _old_marking_cycles_started; 2493 } 2494 2495 if (should_do_concurrent_full_gc(cause)) { 2496 // Schedule an initial-mark evacuation pause that will start a 2497 // concurrent cycle. We're setting word_size to 0 which means that 2498 // we are not requesting a post-GC allocation. 2499 VM_G1IncCollectionPause op(gc_count_before, 2500 0, /* word_size */ 2501 true, /* should_initiate_conc_mark */ 2502 g1_policy()->max_pause_time_ms(), 2503 cause); 2504 2505 VMThread::execute(&op); 2506 if (!op.pause_succeeded()) { 2507 if (old_marking_count_before == _old_marking_cycles_started) { 2508 retry_gc = op.should_retry_gc(); 2509 } else { 2510 // A Full GC happened while we were trying to schedule the 2511 // initial-mark GC. No point in starting a new cycle given 2512 // that the whole heap was collected anyway. 2513 } 2514 2515 if (retry_gc) { 2516 if (GC_locker::is_active_and_needs_gc()) { 2517 GC_locker::stall_until_clear(); 2518 } 2519 } 2520 } 2521 } else { 2522 if (cause == GCCause::_gc_locker 2523 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2524 2525 // Schedule a standard evacuation pause. We're setting word_size 2526 // to 0 which means that we are not requesting a post-GC allocation. 2527 VM_G1IncCollectionPause op(gc_count_before, 2528 0, /* word_size */ 2529 false, /* should_initiate_conc_mark */ 2530 g1_policy()->max_pause_time_ms(), 2531 cause); 2532 VMThread::execute(&op); 2533 } else { 2534 // Schedule a Full GC. 2535 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause); 2536 VMThread::execute(&op); 2537 } 2538 } 2539 } while (retry_gc); 2540 } 2541 2542 bool G1CollectedHeap::is_in(const void* p) const { 2543 if (_g1_committed.contains(p)) { 2544 // Given that we know that p is in the committed space, 2545 // heap_region_containing_raw() should successfully 2546 // return the containing region. 2547 HeapRegion* hr = heap_region_containing_raw(p); 2548 return hr->is_in(p); 2549 } else { 2550 return false; 2551 } 2552 } 2553 2554 // Iteration functions. 2555 2556 // Iterates an OopClosure over all ref-containing fields of objects 2557 // within a HeapRegion. 2558 2559 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2560 MemRegion _mr; 2561 ExtendedOopClosure* _cl; 2562 public: 2563 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl) 2564 : _mr(mr), _cl(cl) {} 2565 bool doHeapRegion(HeapRegion* r) { 2566 if (!r->continuesHumongous()) { 2567 r->oop_iterate(_cl); 2568 } 2569 return false; 2570 } 2571 }; 2572 2573 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2574 IterateOopClosureRegionClosure blk(_g1_committed, cl); 2575 heap_region_iterate(&blk); 2576 } 2577 2578 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { 2579 IterateOopClosureRegionClosure blk(mr, cl); 2580 heap_region_iterate(&blk); 2581 } 2582 2583 // Iterates an ObjectClosure over all objects within a HeapRegion. 2584 2585 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2586 ObjectClosure* _cl; 2587 public: 2588 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2589 bool doHeapRegion(HeapRegion* r) { 2590 if (! r->continuesHumongous()) { 2591 r->object_iterate(_cl); 2592 } 2593 return false; 2594 } 2595 }; 2596 2597 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2598 IterateObjectClosureRegionClosure blk(cl); 2599 heap_region_iterate(&blk); 2600 } 2601 2602 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) { 2603 // FIXME: is this right? 2604 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap"); 2605 } 2606 2607 // Calls a SpaceClosure on a HeapRegion. 2608 2609 class SpaceClosureRegionClosure: public HeapRegionClosure { 2610 SpaceClosure* _cl; 2611 public: 2612 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2613 bool doHeapRegion(HeapRegion* r) { 2614 _cl->do_space(r); 2615 return false; 2616 } 2617 }; 2618 2619 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2620 SpaceClosureRegionClosure blk(cl); 2621 heap_region_iterate(&blk); 2622 } 2623 2624 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2625 _hrs.iterate(cl); 2626 } 2627 2628 void 2629 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2630 uint worker_id, 2631 uint no_of_par_workers, 2632 jint claim_value) { 2633 const uint regions = n_regions(); 2634 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 2635 no_of_par_workers : 2636 1); 2637 assert(UseDynamicNumberOfGCThreads || 2638 no_of_par_workers == workers()->total_workers(), 2639 "Non dynamic should use fixed number of workers"); 2640 // try to spread out the starting points of the workers 2641 const HeapRegion* start_hr = 2642 start_region_for_worker(worker_id, no_of_par_workers); 2643 const uint start_index = start_hr->hrs_index(); 2644 2645 // each worker will actually look at all regions 2646 for (uint count = 0; count < regions; ++count) { 2647 const uint index = (start_index + count) % regions; 2648 assert(0 <= index && index < regions, "sanity"); 2649 HeapRegion* r = region_at(index); 2650 // we'll ignore "continues humongous" regions (we'll process them 2651 // when we come across their corresponding "start humongous" 2652 // region) and regions already claimed 2653 if (r->claim_value() == claim_value || r->continuesHumongous()) { 2654 continue; 2655 } 2656 // OK, try to claim it 2657 if (r->claimHeapRegion(claim_value)) { 2658 // success! 2659 assert(!r->continuesHumongous(), "sanity"); 2660 if (r->startsHumongous()) { 2661 // If the region is "starts humongous" we'll iterate over its 2662 // "continues humongous" first; in fact we'll do them 2663 // first. The order is important. In on case, calling the 2664 // closure on the "starts humongous" region might de-allocate 2665 // and clear all its "continues humongous" regions and, as a 2666 // result, we might end up processing them twice. So, we'll do 2667 // them first (notice: most closures will ignore them anyway) and 2668 // then we'll do the "starts humongous" region. 2669 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) { 2670 HeapRegion* chr = region_at(ch_index); 2671 2672 // if the region has already been claimed or it's not 2673 // "continues humongous" we're done 2674 if (chr->claim_value() == claim_value || 2675 !chr->continuesHumongous()) { 2676 break; 2677 } 2678 2679 // Noone should have claimed it directly. We can given 2680 // that we claimed its "starts humongous" region. 2681 assert(chr->claim_value() != claim_value, "sanity"); 2682 assert(chr->humongous_start_region() == r, "sanity"); 2683 2684 if (chr->claimHeapRegion(claim_value)) { 2685 // we should always be able to claim it; noone else should 2686 // be trying to claim this region 2687 2688 bool res2 = cl->doHeapRegion(chr); 2689 assert(!res2, "Should not abort"); 2690 2691 // Right now, this holds (i.e., no closure that actually 2692 // does something with "continues humongous" regions 2693 // clears them). We might have to weaken it in the future, 2694 // but let's leave these two asserts here for extra safety. 2695 assert(chr->continuesHumongous(), "should still be the case"); 2696 assert(chr->humongous_start_region() == r, "sanity"); 2697 } else { 2698 guarantee(false, "we should not reach here"); 2699 } 2700 } 2701 } 2702 2703 assert(!r->continuesHumongous(), "sanity"); 2704 bool res = cl->doHeapRegion(r); 2705 assert(!res, "Should not abort"); 2706 } 2707 } 2708 } 2709 2710 class ResetClaimValuesClosure: public HeapRegionClosure { 2711 public: 2712 bool doHeapRegion(HeapRegion* r) { 2713 r->set_claim_value(HeapRegion::InitialClaimValue); 2714 return false; 2715 } 2716 }; 2717 2718 void G1CollectedHeap::reset_heap_region_claim_values() { 2719 ResetClaimValuesClosure blk; 2720 heap_region_iterate(&blk); 2721 } 2722 2723 void G1CollectedHeap::reset_cset_heap_region_claim_values() { 2724 ResetClaimValuesClosure blk; 2725 collection_set_iterate(&blk); 2726 } 2727 2728 #ifdef ASSERT 2729 // This checks whether all regions in the heap have the correct claim 2730 // value. I also piggy-backed on this a check to ensure that the 2731 // humongous_start_region() information on "continues humongous" 2732 // regions is correct. 2733 2734 class CheckClaimValuesClosure : public HeapRegionClosure { 2735 private: 2736 jint _claim_value; 2737 uint _failures; 2738 HeapRegion* _sh_region; 2739 2740 public: 2741 CheckClaimValuesClosure(jint claim_value) : 2742 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2743 bool doHeapRegion(HeapRegion* r) { 2744 if (r->claim_value() != _claim_value) { 2745 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2746 "claim value = %d, should be %d", 2747 HR_FORMAT_PARAMS(r), 2748 r->claim_value(), _claim_value); 2749 ++_failures; 2750 } 2751 if (!r->isHumongous()) { 2752 _sh_region = NULL; 2753 } else if (r->startsHumongous()) { 2754 _sh_region = r; 2755 } else if (r->continuesHumongous()) { 2756 if (r->humongous_start_region() != _sh_region) { 2757 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2758 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2759 HR_FORMAT_PARAMS(r), 2760 r->humongous_start_region(), 2761 _sh_region); 2762 ++_failures; 2763 } 2764 } 2765 return false; 2766 } 2767 uint failures() { return _failures; } 2768 }; 2769 2770 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2771 CheckClaimValuesClosure cl(claim_value); 2772 heap_region_iterate(&cl); 2773 return cl.failures() == 0; 2774 } 2775 2776 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2777 private: 2778 jint _claim_value; 2779 uint _failures; 2780 2781 public: 2782 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2783 _claim_value(claim_value), _failures(0) { } 2784 2785 uint failures() { return _failures; } 2786 2787 bool doHeapRegion(HeapRegion* hr) { 2788 assert(hr->in_collection_set(), "how?"); 2789 assert(!hr->isHumongous(), "H-region in CSet"); 2790 if (hr->claim_value() != _claim_value) { 2791 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2792 "claim value = %d, should be %d", 2793 HR_FORMAT_PARAMS(hr), 2794 hr->claim_value(), _claim_value); 2795 _failures += 1; 2796 } 2797 return false; 2798 } 2799 }; 2800 2801 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2802 CheckClaimValuesInCSetHRClosure cl(claim_value); 2803 collection_set_iterate(&cl); 2804 return cl.failures() == 0; 2805 } 2806 #endif // ASSERT 2807 2808 // Clear the cached CSet starting regions and (more importantly) 2809 // the time stamps. Called when we reset the GC time stamp. 2810 void G1CollectedHeap::clear_cset_start_regions() { 2811 assert(_worker_cset_start_region != NULL, "sanity"); 2812 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2813 2814 int n_queues = MAX2((int)ParallelGCThreads, 1); 2815 for (int i = 0; i < n_queues; i++) { 2816 _worker_cset_start_region[i] = NULL; 2817 _worker_cset_start_region_time_stamp[i] = 0; 2818 } 2819 } 2820 2821 // Given the id of a worker, obtain or calculate a suitable 2822 // starting region for iterating over the current collection set. 2823 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) { 2824 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2825 2826 HeapRegion* result = NULL; 2827 unsigned gc_time_stamp = get_gc_time_stamp(); 2828 2829 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2830 // Cached starting region for current worker was set 2831 // during the current pause - so it's valid. 2832 // Note: the cached starting heap region may be NULL 2833 // (when the collection set is empty). 2834 result = _worker_cset_start_region[worker_i]; 2835 assert(result == NULL || result->in_collection_set(), "sanity"); 2836 return result; 2837 } 2838 2839 // The cached entry was not valid so let's calculate 2840 // a suitable starting heap region for this worker. 2841 2842 // We want the parallel threads to start their collection 2843 // set iteration at different collection set regions to 2844 // avoid contention. 2845 // If we have: 2846 // n collection set regions 2847 // p threads 2848 // Then thread t will start at region floor ((t * n) / p) 2849 2850 result = g1_policy()->collection_set(); 2851 if (G1CollectedHeap::use_parallel_gc_threads()) { 2852 uint cs_size = g1_policy()->cset_region_length(); 2853 uint active_workers = workers()->active_workers(); 2854 assert(UseDynamicNumberOfGCThreads || 2855 active_workers == workers()->total_workers(), 2856 "Unless dynamic should use total workers"); 2857 2858 uint end_ind = (cs_size * worker_i) / active_workers; 2859 uint start_ind = 0; 2860 2861 if (worker_i > 0 && 2862 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2863 // Previous workers starting region is valid 2864 // so let's iterate from there 2865 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2866 result = _worker_cset_start_region[worker_i - 1]; 2867 } 2868 2869 for (uint i = start_ind; i < end_ind; i++) { 2870 result = result->next_in_collection_set(); 2871 } 2872 } 2873 2874 // Note: the calculated starting heap region may be NULL 2875 // (when the collection set is empty). 2876 assert(result == NULL || result->in_collection_set(), "sanity"); 2877 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2878 "should be updated only once per pause"); 2879 _worker_cset_start_region[worker_i] = result; 2880 OrderAccess::storestore(); 2881 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2882 return result; 2883 } 2884 2885 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i, 2886 uint no_of_par_workers) { 2887 uint worker_num = 2888 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U; 2889 assert(UseDynamicNumberOfGCThreads || 2890 no_of_par_workers == workers()->total_workers(), 2891 "Non dynamic should use fixed number of workers"); 2892 const uint start_index = n_regions() * worker_i / worker_num; 2893 return region_at(start_index); 2894 } 2895 2896 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2897 HeapRegion* r = g1_policy()->collection_set(); 2898 while (r != NULL) { 2899 HeapRegion* next = r->next_in_collection_set(); 2900 if (cl->doHeapRegion(r)) { 2901 cl->incomplete(); 2902 return; 2903 } 2904 r = next; 2905 } 2906 } 2907 2908 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2909 HeapRegionClosure *cl) { 2910 if (r == NULL) { 2911 // The CSet is empty so there's nothing to do. 2912 return; 2913 } 2914 2915 assert(r->in_collection_set(), 2916 "Start region must be a member of the collection set."); 2917 HeapRegion* cur = r; 2918 while (cur != NULL) { 2919 HeapRegion* next = cur->next_in_collection_set(); 2920 if (cl->doHeapRegion(cur) && false) { 2921 cl->incomplete(); 2922 return; 2923 } 2924 cur = next; 2925 } 2926 cur = g1_policy()->collection_set(); 2927 while (cur != r) { 2928 HeapRegion* next = cur->next_in_collection_set(); 2929 if (cl->doHeapRegion(cur) && false) { 2930 cl->incomplete(); 2931 return; 2932 } 2933 cur = next; 2934 } 2935 } 2936 2937 CompactibleSpace* G1CollectedHeap::first_compactible_space() { 2938 return n_regions() > 0 ? region_at(0) : NULL; 2939 } 2940 2941 2942 Space* G1CollectedHeap::space_containing(const void* addr) const { 2943 Space* res = heap_region_containing(addr); 2944 return res; 2945 } 2946 2947 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2948 Space* sp = space_containing(addr); 2949 if (sp != NULL) { 2950 return sp->block_start(addr); 2951 } 2952 return NULL; 2953 } 2954 2955 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2956 Space* sp = space_containing(addr); 2957 assert(sp != NULL, "block_size of address outside of heap"); 2958 return sp->block_size(addr); 2959 } 2960 2961 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2962 Space* sp = space_containing(addr); 2963 return sp->block_is_obj(addr); 2964 } 2965 2966 bool G1CollectedHeap::supports_tlab_allocation() const { 2967 return true; 2968 } 2969 2970 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2971 return HeapRegion::GrainBytes; 2972 } 2973 2974 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2975 // Return the remaining space in the cur alloc region, but not less than 2976 // the min TLAB size. 2977 2978 // Also, this value can be at most the humongous object threshold, 2979 // since we can't allow tlabs to grow big enough to accomodate 2980 // humongous objects. 2981 2982 HeapRegion* hr = _mutator_alloc_region.get(); 2983 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize; 2984 if (hr == NULL) { 2985 return max_tlab_size; 2986 } else { 2987 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size); 2988 } 2989 } 2990 2991 size_t G1CollectedHeap::max_capacity() const { 2992 return _g1_reserved.byte_size(); 2993 } 2994 2995 jlong G1CollectedHeap::millis_since_last_gc() { 2996 // assert(false, "NYI"); 2997 return 0; 2998 } 2999 3000 void G1CollectedHeap::prepare_for_verify() { 3001 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 3002 ensure_parsability(false); 3003 } 3004 g1_rem_set()->prepare_for_verify(); 3005 } 3006 3007 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 3008 VerifyOption vo) { 3009 switch (vo) { 3010 case VerifyOption_G1UsePrevMarking: 3011 return hr->obj_allocated_since_prev_marking(obj); 3012 case VerifyOption_G1UseNextMarking: 3013 return hr->obj_allocated_since_next_marking(obj); 3014 case VerifyOption_G1UseMarkWord: 3015 return false; 3016 default: 3017 ShouldNotReachHere(); 3018 } 3019 return false; // keep some compilers happy 3020 } 3021 3022 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 3023 switch (vo) { 3024 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 3025 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 3026 case VerifyOption_G1UseMarkWord: return NULL; 3027 default: ShouldNotReachHere(); 3028 } 3029 return NULL; // keep some compilers happy 3030 } 3031 3032 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 3033 switch (vo) { 3034 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 3035 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 3036 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 3037 default: ShouldNotReachHere(); 3038 } 3039 return false; // keep some compilers happy 3040 } 3041 3042 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 3043 switch (vo) { 3044 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 3045 case VerifyOption_G1UseNextMarking: return "NTAMS"; 3046 case VerifyOption_G1UseMarkWord: return "NONE"; 3047 default: ShouldNotReachHere(); 3048 } 3049 return NULL; // keep some compilers happy 3050 } 3051 3052 class VerifyLivenessOopClosure: public OopClosure { 3053 G1CollectedHeap* _g1h; 3054 VerifyOption _vo; 3055 public: 3056 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3057 _g1h(g1h), _vo(vo) 3058 { } 3059 void do_oop(narrowOop *p) { do_oop_work(p); } 3060 void do_oop( oop *p) { do_oop_work(p); } 3061 3062 template <class T> void do_oop_work(T *p) { 3063 oop obj = oopDesc::load_decode_heap_oop(p); 3064 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3065 "Dead object referenced by a not dead object"); 3066 } 3067 }; 3068 3069 class VerifyObjsInRegionClosure: public ObjectClosure { 3070 private: 3071 G1CollectedHeap* _g1h; 3072 size_t _live_bytes; 3073 HeapRegion *_hr; 3074 VerifyOption _vo; 3075 public: 3076 // _vo == UsePrevMarking -> use "prev" marking information, 3077 // _vo == UseNextMarking -> use "next" marking information, 3078 // _vo == UseMarkWord -> use mark word from object header. 3079 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3080 : _live_bytes(0), _hr(hr), _vo(vo) { 3081 _g1h = G1CollectedHeap::heap(); 3082 } 3083 void do_object(oop o) { 3084 VerifyLivenessOopClosure isLive(_g1h, _vo); 3085 assert(o != NULL, "Huh?"); 3086 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3087 // If the object is alive according to the mark word, 3088 // then verify that the marking information agrees. 3089 // Note we can't verify the contra-positive of the 3090 // above: if the object is dead (according to the mark 3091 // word), it may not be marked, or may have been marked 3092 // but has since became dead, or may have been allocated 3093 // since the last marking. 3094 if (_vo == VerifyOption_G1UseMarkWord) { 3095 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3096 } 3097 3098 o->oop_iterate_no_header(&isLive); 3099 if (!_hr->obj_allocated_since_prev_marking(o)) { 3100 size_t obj_size = o->size(); // Make sure we don't overflow 3101 _live_bytes += (obj_size * HeapWordSize); 3102 } 3103 } 3104 } 3105 size_t live_bytes() { return _live_bytes; } 3106 }; 3107 3108 class PrintObjsInRegionClosure : public ObjectClosure { 3109 HeapRegion *_hr; 3110 G1CollectedHeap *_g1; 3111 public: 3112 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3113 _g1 = G1CollectedHeap::heap(); 3114 }; 3115 3116 void do_object(oop o) { 3117 if (o != NULL) { 3118 HeapWord *start = (HeapWord *) o; 3119 size_t word_sz = o->size(); 3120 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3121 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3122 (void*) o, word_sz, 3123 _g1->isMarkedPrev(o), 3124 _g1->isMarkedNext(o), 3125 _hr->obj_allocated_since_prev_marking(o)); 3126 HeapWord *end = start + word_sz; 3127 HeapWord *cur; 3128 int *val; 3129 for (cur = start; cur < end; cur++) { 3130 val = (int *) cur; 3131 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 3132 } 3133 } 3134 } 3135 }; 3136 3137 class VerifyRegionClosure: public HeapRegionClosure { 3138 private: 3139 bool _par; 3140 VerifyOption _vo; 3141 bool _failures; 3142 public: 3143 // _vo == UsePrevMarking -> use "prev" marking information, 3144 // _vo == UseNextMarking -> use "next" marking information, 3145 // _vo == UseMarkWord -> use mark word from object header. 3146 VerifyRegionClosure(bool par, VerifyOption vo) 3147 : _par(par), 3148 _vo(vo), 3149 _failures(false) {} 3150 3151 bool failures() { 3152 return _failures; 3153 } 3154 3155 bool doHeapRegion(HeapRegion* r) { 3156 if (!r->continuesHumongous()) { 3157 bool failures = false; 3158 r->verify(_vo, &failures); 3159 if (failures) { 3160 _failures = true; 3161 } else { 3162 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3163 r->object_iterate(¬_dead_yet_cl); 3164 if (_vo != VerifyOption_G1UseNextMarking) { 3165 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3166 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3167 "max_live_bytes "SIZE_FORMAT" " 3168 "< calculated "SIZE_FORMAT, 3169 r->bottom(), r->end(), 3170 r->max_live_bytes(), 3171 not_dead_yet_cl.live_bytes()); 3172 _failures = true; 3173 } 3174 } else { 3175 // When vo == UseNextMarking we cannot currently do a sanity 3176 // check on the live bytes as the calculation has not been 3177 // finalized yet. 3178 } 3179 } 3180 } 3181 return false; // stop the region iteration if we hit a failure 3182 } 3183 }; 3184 3185 class YoungRefCounterClosure : public OopClosure { 3186 G1CollectedHeap* _g1h; 3187 int _count; 3188 public: 3189 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 3190 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 3191 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 3192 3193 int count() { return _count; } 3194 void reset_count() { _count = 0; }; 3195 }; 3196 3197 class VerifyKlassClosure: public KlassClosure { 3198 YoungRefCounterClosure _young_ref_counter_closure; 3199 OopClosure *_oop_closure; 3200 public: 3201 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3202 void do_klass(Klass* k) { 3203 k->oops_do(_oop_closure); 3204 3205 _young_ref_counter_closure.reset_count(); 3206 k->oops_do(&_young_ref_counter_closure); 3207 if (_young_ref_counter_closure.count() > 0) { 3208 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); 3209 } 3210 } 3211 }; 3212 3213 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can 3214 // pass it as the perm_blk to SharedHeap::process_strong_roots. 3215 // When process_strong_roots stop calling perm_blk->younger_refs_iterate 3216 // we can change this closure to extend the simpler OopClosure. 3217 class VerifyRootsClosure: public OopsInGenClosure { 3218 private: 3219 G1CollectedHeap* _g1h; 3220 VerifyOption _vo; 3221 bool _failures; 3222 public: 3223 // _vo == UsePrevMarking -> use "prev" marking information, 3224 // _vo == UseNextMarking -> use "next" marking information, 3225 // _vo == UseMarkWord -> use mark word from object header. 3226 VerifyRootsClosure(VerifyOption vo) : 3227 _g1h(G1CollectedHeap::heap()), 3228 _vo(vo), 3229 _failures(false) { } 3230 3231 bool failures() { return _failures; } 3232 3233 template <class T> void do_oop_nv(T* p) { 3234 T heap_oop = oopDesc::load_heap_oop(p); 3235 if (!oopDesc::is_null(heap_oop)) { 3236 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3237 if (_g1h->is_obj_dead_cond(obj, _vo)) { 3238 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 3239 "points to dead obj "PTR_FORMAT, p, (void*) obj); 3240 if (_vo == VerifyOption_G1UseMarkWord) { 3241 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 3242 } 3243 obj->print_on(gclog_or_tty); 3244 _failures = true; 3245 } 3246 } 3247 } 3248 3249 void do_oop(oop* p) { do_oop_nv(p); } 3250 void do_oop(narrowOop* p) { do_oop_nv(p); } 3251 }; 3252 3253 // This is the task used for parallel heap verification. 3254 3255 class G1ParVerifyTask: public AbstractGangTask { 3256 private: 3257 G1CollectedHeap* _g1h; 3258 VerifyOption _vo; 3259 bool _failures; 3260 3261 public: 3262 // _vo == UsePrevMarking -> use "prev" marking information, 3263 // _vo == UseNextMarking -> use "next" marking information, 3264 // _vo == UseMarkWord -> use mark word from object header. 3265 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3266 AbstractGangTask("Parallel verify task"), 3267 _g1h(g1h), 3268 _vo(vo), 3269 _failures(false) { } 3270 3271 bool failures() { 3272 return _failures; 3273 } 3274 3275 void work(uint worker_id) { 3276 HandleMark hm; 3277 VerifyRegionClosure blk(true, _vo); 3278 _g1h->heap_region_par_iterate_chunked(&blk, worker_id, 3279 _g1h->workers()->active_workers(), 3280 HeapRegion::ParVerifyClaimValue); 3281 if (blk.failures()) { 3282 _failures = true; 3283 } 3284 } 3285 }; 3286 3287 void G1CollectedHeap::verify(bool silent) { 3288 verify(silent, VerifyOption_G1UsePrevMarking); 3289 } 3290 3291 void G1CollectedHeap::verify(bool silent, 3292 VerifyOption vo) { 3293 if (SafepointSynchronize::is_at_safepoint()) { 3294 if (!silent) { gclog_or_tty->print("Roots "); } 3295 VerifyRootsClosure rootsCl(vo); 3296 3297 assert(Thread::current()->is_VM_thread(), 3298 "Expected to be executed serially by the VM thread at this point"); 3299 3300 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false); 3301 VerifyKlassClosure klassCl(this, &rootsCl); 3302 3303 // We apply the relevant closures to all the oops in the 3304 // system dictionary, the string table and the code cache. 3305 const int so = SO_AllClasses | SO_Strings | SO_CodeCache; 3306 3307 // Need cleared claim bits for the strong roots processing 3308 ClassLoaderDataGraph::clear_claimed_marks(); 3309 3310 process_strong_roots(true, // activate StrongRootsScope 3311 false, // we set "is scavenging" to false, 3312 // so we don't reset the dirty cards. 3313 ScanningOption(so), // roots scanning options 3314 &rootsCl, 3315 &blobsCl, 3316 &klassCl 3317 ); 3318 3319 bool failures = rootsCl.failures(); 3320 3321 if (vo != VerifyOption_G1UseMarkWord) { 3322 // If we're verifying during a full GC then the region sets 3323 // will have been torn down at the start of the GC. Therefore 3324 // verifying the region sets will fail. So we only verify 3325 // the region sets when not in a full GC. 3326 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3327 verify_region_sets(); 3328 } 3329 3330 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3331 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3332 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3333 "sanity check"); 3334 3335 G1ParVerifyTask task(this, vo); 3336 assert(UseDynamicNumberOfGCThreads || 3337 workers()->active_workers() == workers()->total_workers(), 3338 "If not dynamic should be using all the workers"); 3339 int n_workers = workers()->active_workers(); 3340 set_par_threads(n_workers); 3341 workers()->run_task(&task); 3342 set_par_threads(0); 3343 if (task.failures()) { 3344 failures = true; 3345 } 3346 3347 // Checks that the expected amount of parallel work was done. 3348 // The implication is that n_workers is > 0. 3349 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3350 "sanity check"); 3351 3352 reset_heap_region_claim_values(); 3353 3354 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3355 "sanity check"); 3356 } else { 3357 VerifyRegionClosure blk(false, vo); 3358 heap_region_iterate(&blk); 3359 if (blk.failures()) { 3360 failures = true; 3361 } 3362 } 3363 if (!silent) gclog_or_tty->print("RemSet "); 3364 rem_set()->verify(); 3365 3366 if (failures) { 3367 gclog_or_tty->print_cr("Heap:"); 3368 // It helps to have the per-region information in the output to 3369 // help us track down what went wrong. This is why we call 3370 // print_extended_on() instead of print_on(). 3371 print_extended_on(gclog_or_tty); 3372 gclog_or_tty->print_cr(""); 3373 #ifndef PRODUCT 3374 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3375 concurrent_mark()->print_reachable("at-verification-failure", 3376 vo, false /* all */); 3377 } 3378 #endif 3379 gclog_or_tty->flush(); 3380 } 3381 guarantee(!failures, "there should not have been any failures"); 3382 } else { 3383 if (!silent) 3384 gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) "); 3385 } 3386 } 3387 3388 class PrintRegionClosure: public HeapRegionClosure { 3389 outputStream* _st; 3390 public: 3391 PrintRegionClosure(outputStream* st) : _st(st) {} 3392 bool doHeapRegion(HeapRegion* r) { 3393 r->print_on(_st); 3394 return false; 3395 } 3396 }; 3397 3398 void G1CollectedHeap::print_on(outputStream* st) const { 3399 st->print(" %-20s", "garbage-first heap"); 3400 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3401 capacity()/K, used_unlocked()/K); 3402 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3403 _g1_storage.low_boundary(), 3404 _g1_storage.high(), 3405 _g1_storage.high_boundary()); 3406 st->cr(); 3407 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3408 uint young_regions = _young_list->length(); 3409 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3410 (size_t) young_regions * HeapRegion::GrainBytes / K); 3411 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3412 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3413 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3414 st->cr(); 3415 MetaspaceAux::print_on(st); 3416 } 3417 3418 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3419 print_on(st); 3420 3421 // Print the per-region information. 3422 st->cr(); 3423 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3424 "HS=humongous(starts), HC=humongous(continues), " 3425 "CS=collection set, F=free, TS=gc time stamp, " 3426 "PTAMS=previous top-at-mark-start, " 3427 "NTAMS=next top-at-mark-start)"); 3428 PrintRegionClosure blk(st); 3429 heap_region_iterate(&blk); 3430 } 3431 3432 void G1CollectedHeap::print_on_error(outputStream* st) const { 3433 this->CollectedHeap::print_on_error(st); 3434 3435 if (_cm != NULL) { 3436 st->cr(); 3437 _cm->print_on_error(st); 3438 } 3439 } 3440 3441 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3442 if (G1CollectedHeap::use_parallel_gc_threads()) { 3443 workers()->print_worker_threads_on(st); 3444 } 3445 _cmThread->print_on(st); 3446 st->cr(); 3447 _cm->print_worker_threads_on(st); 3448 _cg1r->print_worker_threads_on(st); 3449 } 3450 3451 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3452 if (G1CollectedHeap::use_parallel_gc_threads()) { 3453 workers()->threads_do(tc); 3454 } 3455 tc->do_thread(_cmThread); 3456 _cg1r->threads_do(tc); 3457 } 3458 3459 void G1CollectedHeap::print_tracing_info() const { 3460 // We'll overload this to mean "trace GC pause statistics." 3461 if (TraceGen0Time || TraceGen1Time) { 3462 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3463 // to that. 3464 g1_policy()->print_tracing_info(); 3465 } 3466 if (G1SummarizeRSetStats) { 3467 g1_rem_set()->print_summary_info(); 3468 } 3469 if (G1SummarizeConcMark) { 3470 concurrent_mark()->print_summary_info(); 3471 } 3472 g1_policy()->print_yg_surv_rate_info(); 3473 SpecializationStats::print(); 3474 } 3475 3476 #ifndef PRODUCT 3477 // Helpful for debugging RSet issues. 3478 3479 class PrintRSetsClosure : public HeapRegionClosure { 3480 private: 3481 const char* _msg; 3482 size_t _occupied_sum; 3483 3484 public: 3485 bool doHeapRegion(HeapRegion* r) { 3486 HeapRegionRemSet* hrrs = r->rem_set(); 3487 size_t occupied = hrrs->occupied(); 3488 _occupied_sum += occupied; 3489 3490 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3491 HR_FORMAT_PARAMS(r)); 3492 if (occupied == 0) { 3493 gclog_or_tty->print_cr(" RSet is empty"); 3494 } else { 3495 hrrs->print(); 3496 } 3497 gclog_or_tty->print_cr("----------"); 3498 return false; 3499 } 3500 3501 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3502 gclog_or_tty->cr(); 3503 gclog_or_tty->print_cr("========================================"); 3504 gclog_or_tty->print_cr(msg); 3505 gclog_or_tty->cr(); 3506 } 3507 3508 ~PrintRSetsClosure() { 3509 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3510 gclog_or_tty->print_cr("========================================"); 3511 gclog_or_tty->cr(); 3512 } 3513 }; 3514 3515 void G1CollectedHeap::print_cset_rsets() { 3516 PrintRSetsClosure cl("Printing CSet RSets"); 3517 collection_set_iterate(&cl); 3518 } 3519 3520 void G1CollectedHeap::print_all_rsets() { 3521 PrintRSetsClosure cl("Printing All RSets");; 3522 heap_region_iterate(&cl); 3523 } 3524 #endif // PRODUCT 3525 3526 G1CollectedHeap* G1CollectedHeap::heap() { 3527 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3528 "not a garbage-first heap"); 3529 return _g1h; 3530 } 3531 3532 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3533 // always_do_update_barrier = false; 3534 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3535 // Call allocation profiler 3536 AllocationProfiler::iterate_since_last_gc(); 3537 // Fill TLAB's and such 3538 ensure_parsability(true); 3539 } 3540 3541 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { 3542 // FIXME: what is this about? 3543 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3544 // is set. 3545 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3546 "derived pointer present")); 3547 // always_do_update_barrier = true; 3548 3549 // We have just completed a GC. Update the soft reference 3550 // policy with the new heap occupancy 3551 Universe::update_heap_info_at_gc(); 3552 } 3553 3554 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3555 unsigned int gc_count_before, 3556 bool* succeeded) { 3557 assert_heap_not_locked_and_not_at_safepoint(); 3558 g1_policy()->record_stop_world_start(); 3559 VM_G1IncCollectionPause op(gc_count_before, 3560 word_size, 3561 false, /* should_initiate_conc_mark */ 3562 g1_policy()->max_pause_time_ms(), 3563 GCCause::_g1_inc_collection_pause); 3564 VMThread::execute(&op); 3565 3566 HeapWord* result = op.result(); 3567 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3568 assert(result == NULL || ret_succeeded, 3569 "the result should be NULL if the VM did not succeed"); 3570 *succeeded = ret_succeeded; 3571 3572 assert_heap_not_locked(); 3573 return result; 3574 } 3575 3576 void 3577 G1CollectedHeap::doConcurrentMark() { 3578 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3579 if (!_cmThread->in_progress()) { 3580 _cmThread->set_started(); 3581 CGC_lock->notify(); 3582 } 3583 } 3584 3585 size_t G1CollectedHeap::pending_card_num() { 3586 size_t extra_cards = 0; 3587 JavaThread *curr = Threads::first(); 3588 while (curr != NULL) { 3589 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3590 extra_cards += dcq.size(); 3591 curr = curr->next(); 3592 } 3593 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3594 size_t buffer_size = dcqs.buffer_size(); 3595 size_t buffer_num = dcqs.completed_buffers_num(); 3596 3597 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3598 // in bytes - not the number of 'entries'. We need to convert 3599 // into a number of cards. 3600 return (buffer_size * buffer_num + extra_cards) / oopSize; 3601 } 3602 3603 size_t G1CollectedHeap::cards_scanned() { 3604 return g1_rem_set()->cardsScanned(); 3605 } 3606 3607 void 3608 G1CollectedHeap::setup_surviving_young_words() { 3609 assert(_surviving_young_words == NULL, "pre-condition"); 3610 uint array_length = g1_policy()->young_cset_region_length(); 3611 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3612 if (_surviving_young_words == NULL) { 3613 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3614 "Not enough space for young surv words summary."); 3615 } 3616 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3617 #ifdef ASSERT 3618 for (uint i = 0; i < array_length; ++i) { 3619 assert( _surviving_young_words[i] == 0, "memset above" ); 3620 } 3621 #endif // !ASSERT 3622 } 3623 3624 void 3625 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3626 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3627 uint array_length = g1_policy()->young_cset_region_length(); 3628 for (uint i = 0; i < array_length; ++i) { 3629 _surviving_young_words[i] += surv_young_words[i]; 3630 } 3631 } 3632 3633 void 3634 G1CollectedHeap::cleanup_surviving_young_words() { 3635 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3636 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3637 _surviving_young_words = NULL; 3638 } 3639 3640 #ifdef ASSERT 3641 class VerifyCSetClosure: public HeapRegionClosure { 3642 public: 3643 bool doHeapRegion(HeapRegion* hr) { 3644 // Here we check that the CSet region's RSet is ready for parallel 3645 // iteration. The fields that we'll verify are only manipulated 3646 // when the region is part of a CSet and is collected. Afterwards, 3647 // we reset these fields when we clear the region's RSet (when the 3648 // region is freed) so they are ready when the region is 3649 // re-allocated. The only exception to this is if there's an 3650 // evacuation failure and instead of freeing the region we leave 3651 // it in the heap. In that case, we reset these fields during 3652 // evacuation failure handling. 3653 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3654 3655 // Here's a good place to add any other checks we'd like to 3656 // perform on CSet regions. 3657 return false; 3658 } 3659 }; 3660 #endif // ASSERT 3661 3662 #if TASKQUEUE_STATS 3663 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3664 st->print_raw_cr("GC Task Stats"); 3665 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3666 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3667 } 3668 3669 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3670 print_taskqueue_stats_hdr(st); 3671 3672 TaskQueueStats totals; 3673 const int n = workers() != NULL ? workers()->total_workers() : 1; 3674 for (int i = 0; i < n; ++i) { 3675 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3676 totals += task_queue(i)->stats; 3677 } 3678 st->print_raw("tot "); totals.print(st); st->cr(); 3679 3680 DEBUG_ONLY(totals.verify()); 3681 } 3682 3683 void G1CollectedHeap::reset_taskqueue_stats() { 3684 const int n = workers() != NULL ? workers()->total_workers() : 1; 3685 for (int i = 0; i < n; ++i) { 3686 task_queue(i)->stats.reset(); 3687 } 3688 } 3689 #endif // TASKQUEUE_STATS 3690 3691 void G1CollectedHeap::log_gc_header() { 3692 if (!G1Log::fine()) { 3693 return; 3694 } 3695 3696 gclog_or_tty->date_stamp(PrintGCDateStamps); 3697 gclog_or_tty->stamp(PrintGCTimeStamps); 3698 3699 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3700 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3701 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3702 3703 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3704 } 3705 3706 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3707 if (!G1Log::fine()) { 3708 return; 3709 } 3710 3711 if (G1Log::finer()) { 3712 if (evacuation_failed()) { 3713 gclog_or_tty->print(" (to-space exhausted)"); 3714 } 3715 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3716 g1_policy()->phase_times()->note_gc_end(); 3717 g1_policy()->phase_times()->print(pause_time_sec); 3718 g1_policy()->print_detailed_heap_transition(); 3719 } else { 3720 if (evacuation_failed()) { 3721 gclog_or_tty->print("--"); 3722 } 3723 g1_policy()->print_heap_transition(); 3724 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3725 } 3726 gclog_or_tty->flush(); 3727 } 3728 3729 bool 3730 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3731 assert_at_safepoint(true /* should_be_vm_thread */); 3732 guarantee(!is_gc_active(), "collection is not reentrant"); 3733 3734 if (GC_locker::check_active_before_gc()) { 3735 return false; 3736 } 3737 3738 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3739 ResourceMark rm; 3740 3741 print_heap_before_gc(); 3742 3743 HRSPhaseSetter x(HRSPhaseEvacuation); 3744 verify_region_sets_optional(); 3745 verify_dirty_young_regions(); 3746 3747 // This call will decide whether this pause is an initial-mark 3748 // pause. If it is, during_initial_mark_pause() will return true 3749 // for the duration of this pause. 3750 g1_policy()->decide_on_conc_mark_initiation(); 3751 3752 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3753 assert(!g1_policy()->during_initial_mark_pause() || 3754 g1_policy()->gcs_are_young(), "sanity"); 3755 3756 // We also do not allow mixed GCs during marking. 3757 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3758 3759 // Record whether this pause is an initial mark. When the current 3760 // thread has completed its logging output and it's safe to signal 3761 // the CM thread, the flag's value in the policy has been reset. 3762 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3763 3764 // Inner scope for scope based logging, timers, and stats collection 3765 { 3766 if (g1_policy()->during_initial_mark_pause()) { 3767 // We are about to start a marking cycle, so we increment the 3768 // full collection counter. 3769 increment_old_marking_cycles_started(); 3770 } 3771 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3772 3773 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3774 workers()->active_workers() : 1); 3775 double pause_start_sec = os::elapsedTime(); 3776 g1_policy()->phase_times()->note_gc_start(active_workers); 3777 log_gc_header(); 3778 3779 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3780 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3781 3782 // If the secondary_free_list is not empty, append it to the 3783 // free_list. No need to wait for the cleanup operation to finish; 3784 // the region allocation code will check the secondary_free_list 3785 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3786 // set, skip this step so that the region allocation code has to 3787 // get entries from the secondary_free_list. 3788 if (!G1StressConcRegionFreeing) { 3789 append_secondary_free_list_if_not_empty_with_lock(); 3790 } 3791 3792 assert(check_young_list_well_formed(), 3793 "young list should be well formed"); 3794 3795 // Don't dynamically change the number of GC threads this early. A value of 3796 // 0 is used to indicate serial work. When parallel work is done, 3797 // it will be set. 3798 3799 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3800 IsGCActiveMark x; 3801 3802 gc_prologue(false); 3803 increment_total_collections(false /* full gc */); 3804 increment_gc_time_stamp(); 3805 3806 verify_before_gc(); 3807 3808 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3809 3810 // Please see comment in g1CollectedHeap.hpp and 3811 // G1CollectedHeap::ref_processing_init() to see how 3812 // reference processing currently works in G1. 3813 3814 // Enable discovery in the STW reference processor 3815 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 3816 true /*verify_no_refs*/); 3817 3818 { 3819 // We want to temporarily turn off discovery by the 3820 // CM ref processor, if necessary, and turn it back on 3821 // on again later if we do. Using a scoped 3822 // NoRefDiscovery object will do this. 3823 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3824 3825 // Forget the current alloc region (we might even choose it to be part 3826 // of the collection set!). 3827 release_mutator_alloc_region(); 3828 3829 // We should call this after we retire the mutator alloc 3830 // region(s) so that all the ALLOC / RETIRE events are generated 3831 // before the start GC event. 3832 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3833 3834 // This timing is only used by the ergonomics to handle our pause target. 3835 // It is unclear why this should not include the full pause. We will 3836 // investigate this in CR 7178365. 3837 // 3838 // Preserving the old comment here if that helps the investigation: 3839 // 3840 // The elapsed time induced by the start time below deliberately elides 3841 // the possible verification above. 3842 double sample_start_time_sec = os::elapsedTime(); 3843 3844 #if YOUNG_LIST_VERBOSE 3845 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3846 _young_list->print(); 3847 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3848 #endif // YOUNG_LIST_VERBOSE 3849 3850 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3851 3852 double scan_wait_start = os::elapsedTime(); 3853 // We have to wait until the CM threads finish scanning the 3854 // root regions as it's the only way to ensure that all the 3855 // objects on them have been correctly scanned before we start 3856 // moving them during the GC. 3857 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3858 double wait_time_ms = 0.0; 3859 if (waited) { 3860 double scan_wait_end = os::elapsedTime(); 3861 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3862 } 3863 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3864 3865 #if YOUNG_LIST_VERBOSE 3866 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3867 _young_list->print(); 3868 #endif // YOUNG_LIST_VERBOSE 3869 3870 if (g1_policy()->during_initial_mark_pause()) { 3871 concurrent_mark()->checkpointRootsInitialPre(); 3872 } 3873 3874 #if YOUNG_LIST_VERBOSE 3875 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3876 _young_list->print(); 3877 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3878 #endif // YOUNG_LIST_VERBOSE 3879 3880 g1_policy()->finalize_cset(target_pause_time_ms); 3881 3882 _cm->note_start_of_gc(); 3883 // We should not verify the per-thread SATB buffers given that 3884 // we have not filtered them yet (we'll do so during the 3885 // GC). We also call this after finalize_cset() to 3886 // ensure that the CSet has been finalized. 3887 _cm->verify_no_cset_oops(true /* verify_stacks */, 3888 true /* verify_enqueued_buffers */, 3889 false /* verify_thread_buffers */, 3890 true /* verify_fingers */); 3891 3892 if (_hr_printer.is_active()) { 3893 HeapRegion* hr = g1_policy()->collection_set(); 3894 while (hr != NULL) { 3895 G1HRPrinter::RegionType type; 3896 if (!hr->is_young()) { 3897 type = G1HRPrinter::Old; 3898 } else if (hr->is_survivor()) { 3899 type = G1HRPrinter::Survivor; 3900 } else { 3901 type = G1HRPrinter::Eden; 3902 } 3903 _hr_printer.cset(hr); 3904 hr = hr->next_in_collection_set(); 3905 } 3906 } 3907 3908 #ifdef ASSERT 3909 VerifyCSetClosure cl; 3910 collection_set_iterate(&cl); 3911 #endif // ASSERT 3912 3913 setup_surviving_young_words(); 3914 3915 // Initialize the GC alloc regions. 3916 init_gc_alloc_regions(); 3917 3918 // Actually do the work... 3919 evacuate_collection_set(); 3920 3921 // We do this to mainly verify the per-thread SATB buffers 3922 // (which have been filtered by now) since we didn't verify 3923 // them earlier. No point in re-checking the stacks / enqueued 3924 // buffers given that the CSet has not changed since last time 3925 // we checked. 3926 _cm->verify_no_cset_oops(false /* verify_stacks */, 3927 false /* verify_enqueued_buffers */, 3928 true /* verify_thread_buffers */, 3929 true /* verify_fingers */); 3930 3931 free_collection_set(g1_policy()->collection_set()); 3932 g1_policy()->clear_collection_set(); 3933 3934 cleanup_surviving_young_words(); 3935 3936 // Start a new incremental collection set for the next pause. 3937 g1_policy()->start_incremental_cset_building(); 3938 3939 // Clear the _cset_fast_test bitmap in anticipation of adding 3940 // regions to the incremental collection set for the next 3941 // evacuation pause. 3942 clear_cset_fast_test(); 3943 3944 _young_list->reset_sampled_info(); 3945 3946 // Don't check the whole heap at this point as the 3947 // GC alloc regions from this pause have been tagged 3948 // as survivors and moved on to the survivor list. 3949 // Survivor regions will fail the !is_young() check. 3950 assert(check_young_list_empty(false /* check_heap */), 3951 "young list should be empty"); 3952 3953 #if YOUNG_LIST_VERBOSE 3954 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3955 _young_list->print(); 3956 #endif // YOUNG_LIST_VERBOSE 3957 3958 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3959 _young_list->first_survivor_region(), 3960 _young_list->last_survivor_region()); 3961 3962 _young_list->reset_auxilary_lists(); 3963 3964 if (evacuation_failed()) { 3965 _summary_bytes_used = recalculate_used(); 3966 } else { 3967 // The "used" of the the collection set have already been subtracted 3968 // when they were freed. Add in the bytes evacuated. 3969 _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); 3970 } 3971 3972 if (g1_policy()->during_initial_mark_pause()) { 3973 // We have to do this before we notify the CM threads that 3974 // they can start working to make sure that all the 3975 // appropriate initialization is done on the CM object. 3976 concurrent_mark()->checkpointRootsInitialPost(); 3977 set_marking_started(); 3978 // Note that we don't actually trigger the CM thread at 3979 // this point. We do that later when we're sure that 3980 // the current thread has completed its logging output. 3981 } 3982 3983 allocate_dummy_regions(); 3984 3985 #if YOUNG_LIST_VERBOSE 3986 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 3987 _young_list->print(); 3988 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3989 #endif // YOUNG_LIST_VERBOSE 3990 3991 init_mutator_alloc_region(); 3992 3993 { 3994 size_t expand_bytes = g1_policy()->expansion_amount(); 3995 if (expand_bytes > 0) { 3996 size_t bytes_before = capacity(); 3997 // No need for an ergo verbose message here, 3998 // expansion_amount() does this when it returns a value > 0. 3999 if (!expand(expand_bytes)) { 4000 // We failed to expand the heap so let's verify that 4001 // committed/uncommitted amount match the backing store 4002 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 4003 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 4004 } 4005 } 4006 } 4007 4008 // We redo the verificaiton but now wrt to the new CSet which 4009 // has just got initialized after the previous CSet was freed. 4010 _cm->verify_no_cset_oops(true /* verify_stacks */, 4011 true /* verify_enqueued_buffers */, 4012 true /* verify_thread_buffers */, 4013 true /* verify_fingers */); 4014 _cm->note_end_of_gc(); 4015 4016 // This timing is only used by the ergonomics to handle our pause target. 4017 // It is unclear why this should not include the full pause. We will 4018 // investigate this in CR 7178365. 4019 double sample_end_time_sec = os::elapsedTime(); 4020 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 4021 g1_policy()->record_collection_pause_end(pause_time_ms); 4022 4023 MemoryService::track_memory_usage(); 4024 4025 // In prepare_for_verify() below we'll need to scan the deferred 4026 // update buffers to bring the RSets up-to-date if 4027 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 4028 // the update buffers we'll probably need to scan cards on the 4029 // regions we just allocated to (i.e., the GC alloc 4030 // regions). However, during the last GC we called 4031 // set_saved_mark() on all the GC alloc regions, so card 4032 // scanning might skip the [saved_mark_word()...top()] area of 4033 // those regions (i.e., the area we allocated objects into 4034 // during the last GC). But it shouldn't. Given that 4035 // saved_mark_word() is conditional on whether the GC time stamp 4036 // on the region is current or not, by incrementing the GC time 4037 // stamp here we invalidate all the GC time stamps on all the 4038 // regions and saved_mark_word() will simply return top() for 4039 // all the regions. This is a nicer way of ensuring this rather 4040 // than iterating over the regions and fixing them. In fact, the 4041 // GC time stamp increment here also ensures that 4042 // saved_mark_word() will return top() between pauses, i.e., 4043 // during concurrent refinement. So we don't need the 4044 // is_gc_active() check to decided which top to use when 4045 // scanning cards (see CR 7039627). 4046 increment_gc_time_stamp(); 4047 4048 verify_after_gc(); 4049 4050 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4051 ref_processor_stw()->verify_no_references_recorded(); 4052 4053 // CM reference discovery will be re-enabled if necessary. 4054 } 4055 4056 // We should do this after we potentially expand the heap so 4057 // that all the COMMIT events are generated before the end GC 4058 // event, and after we retire the GC alloc regions so that all 4059 // RETIRE events are generated before the end GC event. 4060 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4061 4062 if (mark_in_progress()) { 4063 concurrent_mark()->update_g1_committed(); 4064 } 4065 4066 #ifdef TRACESPINNING 4067 ParallelTaskTerminator::print_termination_counts(); 4068 #endif 4069 4070 gc_epilogue(false); 4071 } 4072 4073 // Print the remainder of the GC log output. 4074 log_gc_footer(os::elapsedTime() - pause_start_sec); 4075 4076 // It is not yet to safe to tell the concurrent mark to 4077 // start as we have some optional output below. We don't want the 4078 // output from the concurrent mark thread interfering with this 4079 // logging output either. 4080 4081 _hrs.verify_optional(); 4082 verify_region_sets_optional(); 4083 4084 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4085 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4086 4087 print_heap_after_gc(); 4088 4089 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4090 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4091 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4092 // before any GC notifications are raised. 4093 g1mm()->update_sizes(); 4094 } 4095 4096 if (G1SummarizeRSetStats && 4097 (G1SummarizeRSetStatsPeriod > 0) && 4098 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 4099 g1_rem_set()->print_summary_info(); 4100 } 4101 4102 // It should now be safe to tell the concurrent mark thread to start 4103 // without its logging output interfering with the logging output 4104 // that came from the pause. 4105 4106 if (should_start_conc_mark) { 4107 // CAUTION: after the doConcurrentMark() call below, 4108 // the concurrent marking thread(s) could be running 4109 // concurrently with us. Make sure that anything after 4110 // this point does not assume that we are the only GC thread 4111 // running. Note: of course, the actual marking work will 4112 // not start until the safepoint itself is released in 4113 // ConcurrentGCThread::safepoint_desynchronize(). 4114 doConcurrentMark(); 4115 } 4116 4117 return true; 4118 } 4119 4120 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4121 { 4122 size_t gclab_word_size; 4123 switch (purpose) { 4124 case GCAllocForSurvived: 4125 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4126 break; 4127 case GCAllocForTenured: 4128 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4129 break; 4130 default: 4131 assert(false, "unknown GCAllocPurpose"); 4132 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4133 break; 4134 } 4135 4136 // Prevent humongous PLAB sizes for two reasons: 4137 // * PLABs are allocated using a similar paths as oops, but should 4138 // never be in a humongous region 4139 // * Allowing humongous PLABs needlessly churns the region free lists 4140 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4141 } 4142 4143 void G1CollectedHeap::init_mutator_alloc_region() { 4144 assert(_mutator_alloc_region.get() == NULL, "pre-condition"); 4145 _mutator_alloc_region.init(); 4146 } 4147 4148 void G1CollectedHeap::release_mutator_alloc_region() { 4149 _mutator_alloc_region.release(); 4150 assert(_mutator_alloc_region.get() == NULL, "post-condition"); 4151 } 4152 4153 void G1CollectedHeap::init_gc_alloc_regions() { 4154 assert_at_safepoint(true /* should_be_vm_thread */); 4155 4156 _survivor_gc_alloc_region.init(); 4157 _old_gc_alloc_region.init(); 4158 HeapRegion* retained_region = _retained_old_gc_alloc_region; 4159 _retained_old_gc_alloc_region = NULL; 4160 4161 // We will discard the current GC alloc region if: 4162 // a) it's in the collection set (it can happen!), 4163 // b) it's already full (no point in using it), 4164 // c) it's empty (this means that it was emptied during 4165 // a cleanup and it should be on the free list now), or 4166 // d) it's humongous (this means that it was emptied 4167 // during a cleanup and was added to the free list, but 4168 // has been subseqently used to allocate a humongous 4169 // object that may be less than the region size). 4170 if (retained_region != NULL && 4171 !retained_region->in_collection_set() && 4172 !(retained_region->top() == retained_region->end()) && 4173 !retained_region->is_empty() && 4174 !retained_region->isHumongous()) { 4175 retained_region->set_saved_mark(); 4176 // The retained region was added to the old region set when it was 4177 // retired. We have to remove it now, since we don't allow regions 4178 // we allocate to in the region sets. We'll re-add it later, when 4179 // it's retired again. 4180 _old_set.remove(retained_region); 4181 bool during_im = g1_policy()->during_initial_mark_pause(); 4182 retained_region->note_start_of_copying(during_im); 4183 _old_gc_alloc_region.set(retained_region); 4184 _hr_printer.reuse(retained_region); 4185 } 4186 } 4187 4188 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers) { 4189 _survivor_gc_alloc_region.release(); 4190 // If we have an old GC alloc region to release, we'll save it in 4191 // _retained_old_gc_alloc_region. If we don't 4192 // _retained_old_gc_alloc_region will become NULL. This is what we 4193 // want either way so no reason to check explicitly for either 4194 // condition. 4195 _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); 4196 4197 if (ResizePLAB) { 4198 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4199 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4200 } 4201 } 4202 4203 void G1CollectedHeap::abandon_gc_alloc_regions() { 4204 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); 4205 assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); 4206 _retained_old_gc_alloc_region = NULL; 4207 } 4208 4209 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4210 _drain_in_progress = false; 4211 set_evac_failure_closure(cl); 4212 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4213 } 4214 4215 void G1CollectedHeap::finalize_for_evac_failure() { 4216 assert(_evac_failure_scan_stack != NULL && 4217 _evac_failure_scan_stack->length() == 0, 4218 "Postcondition"); 4219 assert(!_drain_in_progress, "Postcondition"); 4220 delete _evac_failure_scan_stack; 4221 _evac_failure_scan_stack = NULL; 4222 } 4223 4224 void G1CollectedHeap::remove_self_forwarding_pointers() { 4225 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4226 4227 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4228 4229 if (G1CollectedHeap::use_parallel_gc_threads()) { 4230 set_par_threads(); 4231 workers()->run_task(&rsfp_task); 4232 set_par_threads(0); 4233 } else { 4234 rsfp_task.work(0); 4235 } 4236 4237 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); 4238 4239 // Reset the claim values in the regions in the collection set. 4240 reset_cset_heap_region_claim_values(); 4241 4242 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4243 4244 // Now restore saved marks, if any. 4245 assert(_objs_with_preserved_marks.size() == 4246 _preserved_marks_of_objs.size(), "Both or none."); 4247 while (!_objs_with_preserved_marks.is_empty()) { 4248 oop obj = _objs_with_preserved_marks.pop(); 4249 markOop m = _preserved_marks_of_objs.pop(); 4250 obj->set_mark(m); 4251 } 4252 _objs_with_preserved_marks.clear(true); 4253 _preserved_marks_of_objs.clear(true); 4254 } 4255 4256 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4257 _evac_failure_scan_stack->push(obj); 4258 } 4259 4260 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4261 assert(_evac_failure_scan_stack != NULL, "precondition"); 4262 4263 while (_evac_failure_scan_stack->length() > 0) { 4264 oop obj = _evac_failure_scan_stack->pop(); 4265 _evac_failure_closure->set_region(heap_region_containing(obj)); 4266 obj->oop_iterate_backwards(_evac_failure_closure); 4267 } 4268 } 4269 4270 oop 4271 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, 4272 oop old) { 4273 assert(obj_in_cs(old), 4274 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4275 (HeapWord*) old)); 4276 markOop m = old->mark(); 4277 oop forward_ptr = old->forward_to_atomic(old); 4278 if (forward_ptr == NULL) { 4279 // Forward-to-self succeeded. 4280 4281 if (_evac_failure_closure != cl) { 4282 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4283 assert(!_drain_in_progress, 4284 "Should only be true while someone holds the lock."); 4285 // Set the global evac-failure closure to the current thread's. 4286 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4287 set_evac_failure_closure(cl); 4288 // Now do the common part. 4289 handle_evacuation_failure_common(old, m); 4290 // Reset to NULL. 4291 set_evac_failure_closure(NULL); 4292 } else { 4293 // The lock is already held, and this is recursive. 4294 assert(_drain_in_progress, "This should only be the recursive case."); 4295 handle_evacuation_failure_common(old, m); 4296 } 4297 return old; 4298 } else { 4299 // Forward-to-self failed. Either someone else managed to allocate 4300 // space for this object (old != forward_ptr) or they beat us in 4301 // self-forwarding it (old == forward_ptr). 4302 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4303 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4304 "should not be in the CSet", 4305 (HeapWord*) old, (HeapWord*) forward_ptr)); 4306 return forward_ptr; 4307 } 4308 } 4309 4310 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4311 set_evacuation_failed(true); 4312 4313 preserve_mark_if_necessary(old, m); 4314 4315 HeapRegion* r = heap_region_containing(old); 4316 if (!r->evacuation_failed()) { 4317 r->set_evacuation_failed(true); 4318 _hr_printer.evac_failure(r); 4319 } 4320 4321 push_on_evac_failure_scan_stack(old); 4322 4323 if (!_drain_in_progress) { 4324 // prevent recursion in copy_to_survivor_space() 4325 _drain_in_progress = true; 4326 drain_evac_failure_scan_stack(); 4327 _drain_in_progress = false; 4328 } 4329 } 4330 4331 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4332 assert(evacuation_failed(), "Oversaving!"); 4333 // We want to call the "for_promotion_failure" version only in the 4334 // case of a promotion failure. 4335 if (m->must_be_preserved_for_promotion_failure(obj)) { 4336 _objs_with_preserved_marks.push(obj); 4337 _preserved_marks_of_objs.push(m); 4338 } 4339 } 4340 4341 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4342 size_t word_size) { 4343 if (purpose == GCAllocForSurvived) { 4344 HeapWord* result = survivor_attempt_allocation(word_size); 4345 if (result != NULL) { 4346 return result; 4347 } else { 4348 // Let's try to allocate in the old gen in case we can fit the 4349 // object there. 4350 return old_attempt_allocation(word_size); 4351 } 4352 } else { 4353 assert(purpose == GCAllocForTenured, "sanity"); 4354 HeapWord* result = old_attempt_allocation(word_size); 4355 if (result != NULL) { 4356 return result; 4357 } else { 4358 // Let's try to allocate in the survivors in case we can fit the 4359 // object there. 4360 return survivor_attempt_allocation(word_size); 4361 } 4362 } 4363 4364 ShouldNotReachHere(); 4365 // Trying to keep some compilers happy. 4366 return NULL; 4367 } 4368 4369 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) : 4370 ParGCAllocBuffer(gclab_word_size), _retired(false) { } 4371 4372 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num) 4373 : _g1h(g1h), 4374 _refs(g1h->task_queue(queue_num)), 4375 _dcq(&g1h->dirty_card_queue_set()), 4376 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()), 4377 _g1_rem(g1h->g1_rem_set()), 4378 _hash_seed(17), _queue_num(queue_num), 4379 _term_attempts(0), 4380 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 4381 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 4382 _age_table(false), 4383 _strong_roots_time(0), _term_time(0), 4384 _alloc_buffer_waste(0), _undo_waste(0) { 4385 // we allocate G1YoungSurvRateNumRegions plus one entries, since 4386 // we "sacrifice" entry 0 to keep track of surviving bytes for 4387 // non-young regions (where the age is -1) 4388 // We also add a few elements at the beginning and at the end in 4389 // an attempt to eliminate cache contention 4390 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); 4391 uint array_length = PADDING_ELEM_NUM + 4392 real_length + 4393 PADDING_ELEM_NUM; 4394 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC); 4395 if (_surviving_young_words_base == NULL) 4396 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR, 4397 "Not enough space for young surv histo."); 4398 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 4399 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t)); 4400 4401 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 4402 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 4403 4404 _start = os::elapsedTime(); 4405 } 4406 4407 void 4408 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 4409 { 4410 st->print_raw_cr("GC Termination Stats"); 4411 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 4412 " ------waste (KiB)------"); 4413 st->print_raw_cr("thr ms ms % ms % attempts" 4414 " total alloc undo"); 4415 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 4416 " ------- ------- -------"); 4417 } 4418 4419 void 4420 G1ParScanThreadState::print_termination_stats(int i, 4421 outputStream* const st) const 4422 { 4423 const double elapsed_ms = elapsed_time() * 1000.0; 4424 const double s_roots_ms = strong_roots_time() * 1000.0; 4425 const double term_ms = term_time() * 1000.0; 4426 st->print_cr("%3d %9.2f %9.2f %6.2f " 4427 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4428 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4429 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 4430 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 4431 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 4432 alloc_buffer_waste() * HeapWordSize / K, 4433 undo_waste() * HeapWordSize / K); 4434 } 4435 4436 #ifdef ASSERT 4437 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 4438 assert(ref != NULL, "invariant"); 4439 assert(UseCompressedOops, "sanity"); 4440 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); 4441 oop p = oopDesc::load_decode_heap_oop(ref); 4442 assert(_g1h->is_in_g1_reserved(p), 4443 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4444 return true; 4445 } 4446 4447 bool G1ParScanThreadState::verify_ref(oop* ref) const { 4448 assert(ref != NULL, "invariant"); 4449 if (has_partial_array_mask(ref)) { 4450 // Must be in the collection set--it's already been copied. 4451 oop p = clear_partial_array_mask(ref); 4452 assert(_g1h->obj_in_cs(p), 4453 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4454 } else { 4455 oop p = oopDesc::load_decode_heap_oop(ref); 4456 assert(_g1h->is_in_g1_reserved(p), 4457 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4458 } 4459 return true; 4460 } 4461 4462 bool G1ParScanThreadState::verify_task(StarTask ref) const { 4463 if (ref.is_narrow()) { 4464 return verify_ref((narrowOop*) ref); 4465 } else { 4466 return verify_ref((oop*) ref); 4467 } 4468 } 4469 #endif // ASSERT 4470 4471 void G1ParScanThreadState::trim_queue() { 4472 assert(_evac_cl != NULL, "not set"); 4473 assert(_evac_failure_cl != NULL, "not set"); 4474 assert(_partial_scan_cl != NULL, "not set"); 4475 4476 StarTask ref; 4477 do { 4478 // Drain the overflow stack first, so other threads can steal. 4479 while (refs()->pop_overflow(ref)) { 4480 deal_with_reference(ref); 4481 } 4482 4483 while (refs()->pop_local(ref)) { 4484 deal_with_reference(ref); 4485 } 4486 } while (!refs()->is_empty()); 4487 } 4488 4489 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, 4490 G1ParScanThreadState* par_scan_state) : 4491 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()), 4492 _par_scan_state(par_scan_state), 4493 _worker_id(par_scan_state->queue_num()), 4494 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()), 4495 _mark_in_progress(_g1->mark_in_progress()) { } 4496 4497 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4498 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) { 4499 #ifdef ASSERT 4500 HeapRegion* hr = _g1->heap_region_containing(obj); 4501 assert(hr != NULL, "sanity"); 4502 assert(!hr->in_collection_set(), "should not mark objects in the CSet"); 4503 #endif // ASSERT 4504 4505 // We know that the object is not moving so it's safe to read its size. 4506 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4507 } 4508 4509 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4510 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4511 ::mark_forwarded_object(oop from_obj, oop to_obj) { 4512 #ifdef ASSERT 4513 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4514 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4515 assert(from_obj != to_obj, "should not be self-forwarded"); 4516 4517 HeapRegion* from_hr = _g1->heap_region_containing(from_obj); 4518 assert(from_hr != NULL, "sanity"); 4519 assert(from_hr->in_collection_set(), "from obj should be in the CSet"); 4520 4521 HeapRegion* to_hr = _g1->heap_region_containing(to_obj); 4522 assert(to_hr != NULL, "sanity"); 4523 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet"); 4524 #endif // ASSERT 4525 4526 // The object might be in the process of being copied by another 4527 // worker so we cannot trust that its to-space image is 4528 // well-formed. So we have to read its size from its from-space 4529 // image which we know should not be changing. 4530 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4531 } 4532 4533 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4534 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4535 ::copy_to_survivor_space(oop old) { 4536 size_t word_sz = old->size(); 4537 HeapRegion* from_region = _g1->heap_region_containing_raw(old); 4538 // +1 to make the -1 indexes valid... 4539 int young_index = from_region->young_index_in_cset()+1; 4540 assert( (from_region->is_young() && young_index > 0) || 4541 (!from_region->is_young() && young_index == 0), "invariant" ); 4542 G1CollectorPolicy* g1p = _g1->g1_policy(); 4543 markOop m = old->mark(); 4544 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 4545 : m->age(); 4546 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 4547 word_sz); 4548 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz); 4549 #ifndef PRODUCT 4550 // Should this evacuation fail? 4551 if (_g1->evacuation_should_fail()) { 4552 if (obj_ptr != NULL) { 4553 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4554 obj_ptr = NULL; 4555 } 4556 } 4557 #endif // !PRODUCT 4558 4559 if (obj_ptr == NULL) { 4560 // This will either forward-to-self, or detect that someone else has 4561 // installed a forwarding pointer. 4562 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4563 return _g1->handle_evacuation_failure_par(cl, old); 4564 } 4565 4566 oop obj = oop(obj_ptr); 4567 4568 // We're going to allocate linearly, so might as well prefetch ahead. 4569 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 4570 4571 oop forward_ptr = old->forward_to_atomic(obj); 4572 if (forward_ptr == NULL) { 4573 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 4574 if (g1p->track_object_age(alloc_purpose)) { 4575 // We could simply do obj->incr_age(). However, this causes a 4576 // performance issue. obj->incr_age() will first check whether 4577 // the object has a displaced mark by checking its mark word; 4578 // getting the mark word from the new location of the object 4579 // stalls. So, given that we already have the mark word and we 4580 // are about to install it anyway, it's better to increase the 4581 // age on the mark word, when the object does not have a 4582 // displaced mark word. We're not expecting many objects to have 4583 // a displaced marked word, so that case is not optimized 4584 // further (it could be...) and we simply call obj->incr_age(). 4585 4586 if (m->has_displaced_mark_helper()) { 4587 // in this case, we have to install the mark word first, 4588 // otherwise obj looks to be forwarded (the old mark word, 4589 // which contains the forward pointer, was copied) 4590 obj->set_mark(m); 4591 obj->incr_age(); 4592 } else { 4593 m = m->incr_age(); 4594 obj->set_mark(m); 4595 } 4596 _par_scan_state->age_table()->add(obj, word_sz); 4597 } else { 4598 obj->set_mark(m); 4599 } 4600 4601 size_t* surv_young_words = _par_scan_state->surviving_young_words(); 4602 surv_young_words[young_index] += word_sz; 4603 4604 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 4605 // We keep track of the next start index in the length field of 4606 // the to-space object. The actual length can be found in the 4607 // length field of the from-space object. 4608 arrayOop(obj)->set_length(0); 4609 oop* old_p = set_partial_array_mask(old); 4610 _par_scan_state->push_on_queue(old_p); 4611 } else { 4612 // No point in using the slower heap_region_containing() method, 4613 // given that we know obj is in the heap. 4614 _scanner.set_region(_g1->heap_region_containing_raw(obj)); 4615 obj->oop_iterate_backwards(&_scanner); 4616 } 4617 } else { 4618 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4619 obj = forward_ptr; 4620 } 4621 return obj; 4622 } 4623 4624 template <class T> 4625 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4626 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4627 _scanned_klass->record_modified_oops(); 4628 } 4629 } 4630 4631 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4632 template <class T> 4633 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4634 ::do_oop_work(T* p) { 4635 oop obj = oopDesc::load_decode_heap_oop(p); 4636 assert(barrier != G1BarrierRS || obj != NULL, 4637 "Precondition: G1BarrierRS implies obj is non-NULL"); 4638 4639 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4640 4641 // here the null check is implicit in the cset_fast_test() test 4642 if (_g1->in_cset_fast_test(obj)) { 4643 oop forwardee; 4644 if (obj->is_forwarded()) { 4645 forwardee = obj->forwardee(); 4646 } else { 4647 forwardee = copy_to_survivor_space(obj); 4648 } 4649 assert(forwardee != NULL, "forwardee should not be NULL"); 4650 oopDesc::encode_store_heap_oop(p, forwardee); 4651 if (do_mark_object && forwardee != obj) { 4652 // If the object is self-forwarded we don't need to explicitly 4653 // mark it, the evacuation failure protocol will do so. 4654 mark_forwarded_object(obj, forwardee); 4655 } 4656 4657 // When scanning the RS, we only care about objs in CS. 4658 if (barrier == G1BarrierRS) { 4659 _par_scan_state->update_rs(_from, p, _worker_id); 4660 } else if (barrier == G1BarrierKlass) { 4661 do_klass_barrier(p, forwardee); 4662 } 4663 } else { 4664 // The object is not in collection set. If we're a root scanning 4665 // closure during an initial mark pause (i.e. do_mark_object will 4666 // be true) then attempt to mark the object. 4667 if (do_mark_object && _g1->is_in_g1_reserved(obj)) { 4668 mark_object(obj); 4669 } 4670 } 4671 4672 if (barrier == G1BarrierEvac && obj != NULL) { 4673 _par_scan_state->update_rs(_from, p, _worker_id); 4674 } 4675 4676 if (do_gen_barrier && obj != NULL) { 4677 par_do_barrier(p); 4678 } 4679 } 4680 4681 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p); 4682 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p); 4683 4684 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) { 4685 assert(has_partial_array_mask(p), "invariant"); 4686 oop from_obj = clear_partial_array_mask(p); 4687 4688 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap."); 4689 assert(from_obj->is_objArray(), "must be obj array"); 4690 objArrayOop from_obj_array = objArrayOop(from_obj); 4691 // The from-space object contains the real length. 4692 int length = from_obj_array->length(); 4693 4694 assert(from_obj->is_forwarded(), "must be forwarded"); 4695 oop to_obj = from_obj->forwardee(); 4696 assert(from_obj != to_obj, "should not be chunking self-forwarded objects"); 4697 objArrayOop to_obj_array = objArrayOop(to_obj); 4698 // We keep track of the next start index in the length field of the 4699 // to-space object. 4700 int next_index = to_obj_array->length(); 4701 assert(0 <= next_index && next_index < length, 4702 err_msg("invariant, next index: %d, length: %d", next_index, length)); 4703 4704 int start = next_index; 4705 int end = length; 4706 int remainder = end - start; 4707 // We'll try not to push a range that's smaller than ParGCArrayScanChunk. 4708 if (remainder > 2 * ParGCArrayScanChunk) { 4709 end = start + ParGCArrayScanChunk; 4710 to_obj_array->set_length(end); 4711 // Push the remainder before we process the range in case another 4712 // worker has run out of things to do and can steal it. 4713 oop* from_obj_p = set_partial_array_mask(from_obj); 4714 _par_scan_state->push_on_queue(from_obj_p); 4715 } else { 4716 assert(length == end, "sanity"); 4717 // We'll process the final range for this object. Restore the length 4718 // so that the heap remains parsable in case of evacuation failure. 4719 to_obj_array->set_length(end); 4720 } 4721 _scanner.set_region(_g1->heap_region_containing_raw(to_obj)); 4722 // Process indexes [start,end). It will also process the header 4723 // along with the first chunk (i.e., the chunk with start == 0). 4724 // Note that at this point the length field of to_obj_array is not 4725 // correct given that we are using it to keep track of the next 4726 // start index. oop_iterate_range() (thankfully!) ignores the length 4727 // field and only relies on the start / end parameters. It does 4728 // however return the size of the object which will be incorrect. So 4729 // we have to ignore it even if we wanted to use it. 4730 to_obj_array->oop_iterate_range(&_scanner, start, end); 4731 } 4732 4733 class G1ParEvacuateFollowersClosure : public VoidClosure { 4734 protected: 4735 G1CollectedHeap* _g1h; 4736 G1ParScanThreadState* _par_scan_state; 4737 RefToScanQueueSet* _queues; 4738 ParallelTaskTerminator* _terminator; 4739 4740 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4741 RefToScanQueueSet* queues() { return _queues; } 4742 ParallelTaskTerminator* terminator() { return _terminator; } 4743 4744 public: 4745 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4746 G1ParScanThreadState* par_scan_state, 4747 RefToScanQueueSet* queues, 4748 ParallelTaskTerminator* terminator) 4749 : _g1h(g1h), _par_scan_state(par_scan_state), 4750 _queues(queues), _terminator(terminator) {} 4751 4752 void do_void(); 4753 4754 private: 4755 inline bool offer_termination(); 4756 }; 4757 4758 bool G1ParEvacuateFollowersClosure::offer_termination() { 4759 G1ParScanThreadState* const pss = par_scan_state(); 4760 pss->start_term_time(); 4761 const bool res = terminator()->offer_termination(); 4762 pss->end_term_time(); 4763 return res; 4764 } 4765 4766 void G1ParEvacuateFollowersClosure::do_void() { 4767 StarTask stolen_task; 4768 G1ParScanThreadState* const pss = par_scan_state(); 4769 pss->trim_queue(); 4770 4771 do { 4772 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { 4773 assert(pss->verify_task(stolen_task), "sanity"); 4774 if (stolen_task.is_narrow()) { 4775 pss->deal_with_reference((narrowOop*) stolen_task); 4776 } else { 4777 pss->deal_with_reference((oop*) stolen_task); 4778 } 4779 4780 // We've just processed a reference and we might have made 4781 // available new entries on the queues. So we have to make sure 4782 // we drain the queues as necessary. 4783 pss->trim_queue(); 4784 } 4785 } while (!offer_termination()); 4786 4787 pss->retire_alloc_buffers(); 4788 } 4789 4790 class G1KlassScanClosure : public KlassClosure { 4791 G1ParCopyHelper* _closure; 4792 bool _process_only_dirty; 4793 int _count; 4794 public: 4795 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4796 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4797 void do_klass(Klass* klass) { 4798 // If the klass has not been dirtied we know that there's 4799 // no references into the young gen and we can skip it. 4800 if (!_process_only_dirty || klass->has_modified_oops()) { 4801 // Clean the klass since we're going to scavenge all the metadata. 4802 klass->clear_modified_oops(); 4803 4804 // Tell the closure that this klass is the Klass to scavenge 4805 // and is the one to dirty if oops are left pointing into the young gen. 4806 _closure->set_scanned_klass(klass); 4807 4808 klass->oops_do(_closure); 4809 4810 _closure->set_scanned_klass(NULL); 4811 } 4812 _count++; 4813 } 4814 }; 4815 4816 class G1ParTask : public AbstractGangTask { 4817 protected: 4818 G1CollectedHeap* _g1h; 4819 RefToScanQueueSet *_queues; 4820 ParallelTaskTerminator _terminator; 4821 uint _n_workers; 4822 4823 Mutex _stats_lock; 4824 Mutex* stats_lock() { return &_stats_lock; } 4825 4826 size_t getNCards() { 4827 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) 4828 / G1BlockOffsetSharedArray::N_bytes; 4829 } 4830 4831 public: 4832 G1ParTask(G1CollectedHeap* g1h, 4833 RefToScanQueueSet *task_queues) 4834 : AbstractGangTask("G1 collection"), 4835 _g1h(g1h), 4836 _queues(task_queues), 4837 _terminator(0, _queues), 4838 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4839 {} 4840 4841 RefToScanQueueSet* queues() { return _queues; } 4842 4843 RefToScanQueue *work_queue(int i) { 4844 return queues()->queue(i); 4845 } 4846 4847 ParallelTaskTerminator* terminator() { return &_terminator; } 4848 4849 virtual void set_for_termination(int active_workers) { 4850 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4851 // in the young space (_par_seq_tasks) in the G1 heap 4852 // for SequentialSubTasksDone. 4853 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4854 // both of which need setting by set_n_termination(). 4855 _g1h->SharedHeap::set_n_termination(active_workers); 4856 _g1h->set_n_termination(active_workers); 4857 terminator()->reset_for_reuse(active_workers); 4858 _n_workers = active_workers; 4859 } 4860 4861 void work(uint worker_id) { 4862 if (worker_id >= _n_workers) return; // no work needed this round 4863 4864 double start_time_ms = os::elapsedTime() * 1000.0; 4865 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 4866 4867 { 4868 ResourceMark rm; 4869 HandleMark hm; 4870 4871 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4872 4873 G1ParScanThreadState pss(_g1h, worker_id); 4874 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp); 4875 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4876 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp); 4877 4878 pss.set_evac_closure(&scan_evac_cl); 4879 pss.set_evac_failure_closure(&evac_failure_cl); 4880 pss.set_partial_scan_closure(&partial_scan_cl); 4881 4882 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp); 4883 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp); 4884 4885 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp); 4886 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp); 4887 4888 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4889 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false); 4890 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young); 4891 4892 OopClosure* scan_root_cl = &only_scan_root_cl; 4893 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s; 4894 4895 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4896 // We also need to mark copied objects. 4897 scan_root_cl = &scan_mark_root_cl; 4898 scan_klasses_cl = &scan_mark_klasses_cl_s; 4899 } 4900 4901 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4902 4903 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; 4904 4905 pss.start_strong_roots(); 4906 _g1h->g1_process_strong_roots(/* is scavenging */ true, 4907 SharedHeap::ScanningOption(so), 4908 scan_root_cl, 4909 &push_heap_rs_cl, 4910 scan_klasses_cl, 4911 worker_id); 4912 pss.end_strong_roots(); 4913 4914 { 4915 double start = os::elapsedTime(); 4916 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4917 evac.do_void(); 4918 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4919 double term_ms = pss.term_time()*1000.0; 4920 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 4921 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 4922 } 4923 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4924 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4925 4926 if (ParallelGCVerbose) { 4927 MutexLocker x(stats_lock()); 4928 pss.print_termination_stats(worker_id); 4929 } 4930 4931 assert(pss.refs()->is_empty(), "should be empty"); 4932 4933 // Close the inner scope so that the ResourceMark and HandleMark 4934 // destructors are executed here and are included as part of the 4935 // "GC Worker Time". 4936 } 4937 4938 double end_time_ms = os::elapsedTime() * 1000.0; 4939 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 4940 } 4941 }; 4942 4943 // *** Common G1 Evacuation Stuff 4944 4945 // Closures that support the filtering of CodeBlobs scanned during 4946 // external root scanning. 4947 4948 // Closure applied to reference fields in code blobs (specifically nmethods) 4949 // to determine whether an nmethod contains references that point into 4950 // the collection set. Used as a predicate when walking code roots so 4951 // that only nmethods that point into the collection set are added to the 4952 // 'marked' list. 4953 4954 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure { 4955 4956 class G1PointsIntoCSOopClosure : public OopClosure { 4957 G1CollectedHeap* _g1; 4958 bool _points_into_cs; 4959 public: 4960 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) : 4961 _g1(g1), _points_into_cs(false) { } 4962 4963 bool points_into_cs() const { return _points_into_cs; } 4964 4965 template <class T> 4966 void do_oop_nv(T* p) { 4967 if (!_points_into_cs) { 4968 T heap_oop = oopDesc::load_heap_oop(p); 4969 if (!oopDesc::is_null(heap_oop) && 4970 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) { 4971 _points_into_cs = true; 4972 } 4973 } 4974 } 4975 4976 virtual void do_oop(oop* p) { do_oop_nv(p); } 4977 virtual void do_oop(narrowOop* p) { do_oop_nv(p); } 4978 }; 4979 4980 G1CollectedHeap* _g1; 4981 4982 public: 4983 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) : 4984 CodeBlobToOopClosure(cl, true), _g1(g1) { } 4985 4986 virtual void do_code_blob(CodeBlob* cb) { 4987 nmethod* nm = cb->as_nmethod_or_null(); 4988 if (nm != NULL && !(nm->test_oops_do_mark())) { 4989 G1PointsIntoCSOopClosure predicate_cl(_g1); 4990 nm->oops_do(&predicate_cl); 4991 4992 if (predicate_cl.points_into_cs()) { 4993 // At least one of the reference fields or the oop relocations 4994 // in the nmethod points into the collection set. We have to 4995 // 'mark' this nmethod. 4996 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob() 4997 // or MarkingCodeBlobClosure::do_code_blob() change. 4998 if (!nm->test_set_oops_do_mark()) { 4999 do_newly_marked_nmethod(nm); 5000 } 5001 } 5002 } 5003 } 5004 }; 5005 5006 // This method is run in a GC worker. 5007 5008 void 5009 G1CollectedHeap:: 5010 g1_process_strong_roots(bool is_scavenging, 5011 ScanningOption so, 5012 OopClosure* scan_non_heap_roots, 5013 OopsInHeapRegionClosure* scan_rs, 5014 G1KlassScanClosure* scan_klasses, 5015 int worker_i) { 5016 5017 // First scan the strong roots 5018 double ext_roots_start = os::elapsedTime(); 5019 double closure_app_time_sec = 0.0; 5020 5021 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 5022 5023 // Walk the code cache w/o buffering, because StarTask cannot handle 5024 // unaligned oop locations. 5025 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots); 5026 5027 process_strong_roots(false, // no scoping; this is parallel code 5028 is_scavenging, so, 5029 &buf_scan_non_heap_roots, 5030 &eager_scan_code_roots, 5031 scan_klasses 5032 ); 5033 5034 // Now the CM ref_processor roots. 5035 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 5036 // We need to treat the discovered reference lists of the 5037 // concurrent mark ref processor as roots and keep entries 5038 // (which are added by the marking threads) on them live 5039 // until they can be processed at the end of marking. 5040 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 5041 } 5042 5043 // Finish up any enqueued closure apps (attributed as object copy time). 5044 buf_scan_non_heap_roots.done(); 5045 5046 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds(); 5047 5048 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 5049 5050 double ext_root_time_ms = 5051 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 5052 5053 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 5054 5055 // During conc marking we have to filter the per-thread SATB buffers 5056 // to make sure we remove any oops into the CSet (which will show up 5057 // as implicitly live). 5058 double satb_filtering_ms = 0.0; 5059 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 5060 if (mark_in_progress()) { 5061 double satb_filter_start = os::elapsedTime(); 5062 5063 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 5064 5065 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 5066 } 5067 } 5068 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 5069 5070 // Now scan the complement of the collection set. 5071 if (scan_rs != NULL) { 5072 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i); 5073 } 5074 _process_strong_tasks->all_tasks_completed(); 5075 } 5076 5077 void 5078 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) { 5079 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); 5080 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs); 5081 } 5082 5083 // Weak Reference Processing support 5084 5085 // An always "is_alive" closure that is used to preserve referents. 5086 // If the object is non-null then it's alive. Used in the preservation 5087 // of referent objects that are pointed to by reference objects 5088 // discovered by the CM ref processor. 5089 class G1AlwaysAliveClosure: public BoolObjectClosure { 5090 G1CollectedHeap* _g1; 5091 public: 5092 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5093 bool do_object_b(oop p) { 5094 if (p != NULL) { 5095 return true; 5096 } 5097 return false; 5098 } 5099 }; 5100 5101 bool G1STWIsAliveClosure::do_object_b(oop p) { 5102 // An object is reachable if it is outside the collection set, 5103 // or is inside and copied. 5104 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5105 } 5106 5107 // Non Copying Keep Alive closure 5108 class G1KeepAliveClosure: public OopClosure { 5109 G1CollectedHeap* _g1; 5110 public: 5111 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5112 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5113 void do_oop( oop* p) { 5114 oop obj = *p; 5115 5116 if (_g1->obj_in_cs(obj)) { 5117 assert( obj->is_forwarded(), "invariant" ); 5118 *p = obj->forwardee(); 5119 } 5120 } 5121 }; 5122 5123 // Copying Keep Alive closure - can be called from both 5124 // serial and parallel code as long as different worker 5125 // threads utilize different G1ParScanThreadState instances 5126 // and different queues. 5127 5128 class G1CopyingKeepAliveClosure: public OopClosure { 5129 G1CollectedHeap* _g1h; 5130 OopClosure* _copy_non_heap_obj_cl; 5131 OopsInHeapRegionClosure* _copy_metadata_obj_cl; 5132 G1ParScanThreadState* _par_scan_state; 5133 5134 public: 5135 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5136 OopClosure* non_heap_obj_cl, 5137 OopsInHeapRegionClosure* metadata_obj_cl, 5138 G1ParScanThreadState* pss): 5139 _g1h(g1h), 5140 _copy_non_heap_obj_cl(non_heap_obj_cl), 5141 _copy_metadata_obj_cl(metadata_obj_cl), 5142 _par_scan_state(pss) 5143 {} 5144 5145 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5146 virtual void do_oop( oop* p) { do_oop_work(p); } 5147 5148 template <class T> void do_oop_work(T* p) { 5149 oop obj = oopDesc::load_decode_heap_oop(p); 5150 5151 if (_g1h->obj_in_cs(obj)) { 5152 // If the referent object has been forwarded (either copied 5153 // to a new location or to itself in the event of an 5154 // evacuation failure) then we need to update the reference 5155 // field and, if both reference and referent are in the G1 5156 // heap, update the RSet for the referent. 5157 // 5158 // If the referent has not been forwarded then we have to keep 5159 // it alive by policy. Therefore we have copy the referent. 5160 // 5161 // If the reference field is in the G1 heap then we can push 5162 // on the PSS queue. When the queue is drained (after each 5163 // phase of reference processing) the object and it's followers 5164 // will be copied, the reference field set to point to the 5165 // new location, and the RSet updated. Otherwise we need to 5166 // use the the non-heap or metadata closures directly to copy 5167 // the refernt object and update the pointer, while avoiding 5168 // updating the RSet. 5169 5170 if (_g1h->is_in_g1_reserved(p)) { 5171 _par_scan_state->push_on_queue(p); 5172 } else { 5173 assert(!ClassLoaderDataGraph::contains((address)p), 5174 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) " 5175 PTR_FORMAT, p)); 5176 _copy_non_heap_obj_cl->do_oop(p); 5177 } 5178 } 5179 } 5180 }; 5181 5182 // Serial drain queue closure. Called as the 'complete_gc' 5183 // closure for each discovered list in some of the 5184 // reference processing phases. 5185 5186 class G1STWDrainQueueClosure: public VoidClosure { 5187 protected: 5188 G1CollectedHeap* _g1h; 5189 G1ParScanThreadState* _par_scan_state; 5190 5191 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5192 5193 public: 5194 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5195 _g1h(g1h), 5196 _par_scan_state(pss) 5197 { } 5198 5199 void do_void() { 5200 G1ParScanThreadState* const pss = par_scan_state(); 5201 pss->trim_queue(); 5202 } 5203 }; 5204 5205 // Parallel Reference Processing closures 5206 5207 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5208 // processing during G1 evacuation pauses. 5209 5210 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5211 private: 5212 G1CollectedHeap* _g1h; 5213 RefToScanQueueSet* _queues; 5214 FlexibleWorkGang* _workers; 5215 int _active_workers; 5216 5217 public: 5218 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5219 FlexibleWorkGang* workers, 5220 RefToScanQueueSet *task_queues, 5221 int n_workers) : 5222 _g1h(g1h), 5223 _queues(task_queues), 5224 _workers(workers), 5225 _active_workers(n_workers) 5226 { 5227 assert(n_workers > 0, "shouldn't call this otherwise"); 5228 } 5229 5230 // Executes the given task using concurrent marking worker threads. 5231 virtual void execute(ProcessTask& task); 5232 virtual void execute(EnqueueTask& task); 5233 }; 5234 5235 // Gang task for possibly parallel reference processing 5236 5237 class G1STWRefProcTaskProxy: public AbstractGangTask { 5238 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5239 ProcessTask& _proc_task; 5240 G1CollectedHeap* _g1h; 5241 RefToScanQueueSet *_task_queues; 5242 ParallelTaskTerminator* _terminator; 5243 5244 public: 5245 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5246 G1CollectedHeap* g1h, 5247 RefToScanQueueSet *task_queues, 5248 ParallelTaskTerminator* terminator) : 5249 AbstractGangTask("Process reference objects in parallel"), 5250 _proc_task(proc_task), 5251 _g1h(g1h), 5252 _task_queues(task_queues), 5253 _terminator(terminator) 5254 {} 5255 5256 virtual void work(uint worker_id) { 5257 // The reference processing task executed by a single worker. 5258 ResourceMark rm; 5259 HandleMark hm; 5260 5261 G1STWIsAliveClosure is_alive(_g1h); 5262 5263 G1ParScanThreadState pss(_g1h, worker_id); 5264 5265 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5266 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5267 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5268 5269 pss.set_evac_closure(&scan_evac_cl); 5270 pss.set_evac_failure_closure(&evac_failure_cl); 5271 pss.set_partial_scan_closure(&partial_scan_cl); 5272 5273 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5274 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5275 5276 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5277 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5278 5279 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5280 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5281 5282 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5283 // We also need to mark copied objects. 5284 copy_non_heap_cl = ©_mark_non_heap_cl; 5285 copy_metadata_cl = ©_mark_metadata_cl; 5286 } 5287 5288 // Keep alive closure. 5289 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5290 5291 // Complete GC closure 5292 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5293 5294 // Call the reference processing task's work routine. 5295 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5296 5297 // Note we cannot assert that the refs array is empty here as not all 5298 // of the processing tasks (specifically phase2 - pp2_work) execute 5299 // the complete_gc closure (which ordinarily would drain the queue) so 5300 // the queue may not be empty. 5301 } 5302 }; 5303 5304 // Driver routine for parallel reference processing. 5305 // Creates an instance of the ref processing gang 5306 // task and has the worker threads execute it. 5307 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5308 assert(_workers != NULL, "Need parallel worker threads."); 5309 5310 ParallelTaskTerminator terminator(_active_workers, _queues); 5311 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5312 5313 _g1h->set_par_threads(_active_workers); 5314 _workers->run_task(&proc_task_proxy); 5315 _g1h->set_par_threads(0); 5316 } 5317 5318 // Gang task for parallel reference enqueueing. 5319 5320 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5321 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5322 EnqueueTask& _enq_task; 5323 5324 public: 5325 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5326 AbstractGangTask("Enqueue reference objects in parallel"), 5327 _enq_task(enq_task) 5328 { } 5329 5330 virtual void work(uint worker_id) { 5331 _enq_task.work(worker_id); 5332 } 5333 }; 5334 5335 // Driver routine for parallel reference enqueing. 5336 // Creates an instance of the ref enqueueing gang 5337 // task and has the worker threads execute it. 5338 5339 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5340 assert(_workers != NULL, "Need parallel worker threads."); 5341 5342 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5343 5344 _g1h->set_par_threads(_active_workers); 5345 _workers->run_task(&enq_task_proxy); 5346 _g1h->set_par_threads(0); 5347 } 5348 5349 // End of weak reference support closures 5350 5351 // Abstract task used to preserve (i.e. copy) any referent objects 5352 // that are in the collection set and are pointed to by reference 5353 // objects discovered by the CM ref processor. 5354 5355 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5356 protected: 5357 G1CollectedHeap* _g1h; 5358 RefToScanQueueSet *_queues; 5359 ParallelTaskTerminator _terminator; 5360 uint _n_workers; 5361 5362 public: 5363 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5364 AbstractGangTask("ParPreserveCMReferents"), 5365 _g1h(g1h), 5366 _queues(task_queues), 5367 _terminator(workers, _queues), 5368 _n_workers(workers) 5369 { } 5370 5371 void work(uint worker_id) { 5372 ResourceMark rm; 5373 HandleMark hm; 5374 5375 G1ParScanThreadState pss(_g1h, worker_id); 5376 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5377 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5378 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5379 5380 pss.set_evac_closure(&scan_evac_cl); 5381 pss.set_evac_failure_closure(&evac_failure_cl); 5382 pss.set_partial_scan_closure(&partial_scan_cl); 5383 5384 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5385 5386 5387 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5388 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5389 5390 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5391 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5392 5393 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5394 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5395 5396 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5397 // We also need to mark copied objects. 5398 copy_non_heap_cl = ©_mark_non_heap_cl; 5399 copy_metadata_cl = ©_mark_metadata_cl; 5400 } 5401 5402 // Is alive closure 5403 G1AlwaysAliveClosure always_alive(_g1h); 5404 5405 // Copying keep alive closure. Applied to referent objects that need 5406 // to be copied. 5407 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5408 5409 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5410 5411 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5412 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5413 5414 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5415 // So this must be true - but assert just in case someone decides to 5416 // change the worker ids. 5417 assert(0 <= worker_id && worker_id < limit, "sanity"); 5418 assert(!rp->discovery_is_atomic(), "check this code"); 5419 5420 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5421 for (uint idx = worker_id; idx < limit; idx += stride) { 5422 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5423 5424 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5425 while (iter.has_next()) { 5426 // Since discovery is not atomic for the CM ref processor, we 5427 // can see some null referent objects. 5428 iter.load_ptrs(DEBUG_ONLY(true)); 5429 oop ref = iter.obj(); 5430 5431 // This will filter nulls. 5432 if (iter.is_referent_alive()) { 5433 iter.make_referent_alive(); 5434 } 5435 iter.move_to_next(); 5436 } 5437 } 5438 5439 // Drain the queue - which may cause stealing 5440 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5441 drain_queue.do_void(); 5442 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5443 assert(pss.refs()->is_empty(), "should be"); 5444 } 5445 }; 5446 5447 // Weak Reference processing during an evacuation pause (part 1). 5448 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5449 double ref_proc_start = os::elapsedTime(); 5450 5451 ReferenceProcessor* rp = _ref_processor_stw; 5452 assert(rp->discovery_enabled(), "should have been enabled"); 5453 5454 // Any reference objects, in the collection set, that were 'discovered' 5455 // by the CM ref processor should have already been copied (either by 5456 // applying the external root copy closure to the discovered lists, or 5457 // by following an RSet entry). 5458 // 5459 // But some of the referents, that are in the collection set, that these 5460 // reference objects point to may not have been copied: the STW ref 5461 // processor would have seen that the reference object had already 5462 // been 'discovered' and would have skipped discovering the reference, 5463 // but would not have treated the reference object as a regular oop. 5464 // As a reult the copy closure would not have been applied to the 5465 // referent object. 5466 // 5467 // We need to explicitly copy these referent objects - the references 5468 // will be processed at the end of remarking. 5469 // 5470 // We also need to do this copying before we process the reference 5471 // objects discovered by the STW ref processor in case one of these 5472 // referents points to another object which is also referenced by an 5473 // object discovered by the STW ref processor. 5474 5475 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5476 no_of_gc_workers == workers()->active_workers(), 5477 "Need to reset active GC workers"); 5478 5479 set_par_threads(no_of_gc_workers); 5480 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5481 no_of_gc_workers, 5482 _task_queues); 5483 5484 if (G1CollectedHeap::use_parallel_gc_threads()) { 5485 workers()->run_task(&keep_cm_referents); 5486 } else { 5487 keep_cm_referents.work(0); 5488 } 5489 5490 set_par_threads(0); 5491 5492 // Closure to test whether a referent is alive. 5493 G1STWIsAliveClosure is_alive(this); 5494 5495 // Even when parallel reference processing is enabled, the processing 5496 // of JNI refs is serial and performed serially by the current thread 5497 // rather than by a worker. The following PSS will be used for processing 5498 // JNI refs. 5499 5500 // Use only a single queue for this PSS. 5501 G1ParScanThreadState pss(this, 0); 5502 5503 // We do not embed a reference processor in the copying/scanning 5504 // closures while we're actually processing the discovered 5505 // reference objects. 5506 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL); 5507 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5508 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL); 5509 5510 pss.set_evac_closure(&scan_evac_cl); 5511 pss.set_evac_failure_closure(&evac_failure_cl); 5512 pss.set_partial_scan_closure(&partial_scan_cl); 5513 5514 assert(pss.refs()->is_empty(), "pre-condition"); 5515 5516 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5517 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL); 5518 5519 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5520 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL); 5521 5522 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5523 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5524 5525 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5526 // We also need to mark copied objects. 5527 copy_non_heap_cl = ©_mark_non_heap_cl; 5528 copy_metadata_cl = ©_mark_metadata_cl; 5529 } 5530 5531 // Keep alive closure. 5532 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss); 5533 5534 // Serial Complete GC closure 5535 G1STWDrainQueueClosure drain_queue(this, &pss); 5536 5537 // Setup the soft refs policy... 5538 rp->setup_policy(false); 5539 5540 if (!rp->processing_is_mt()) { 5541 // Serial reference processing... 5542 rp->process_discovered_references(&is_alive, 5543 &keep_alive, 5544 &drain_queue, 5545 NULL); 5546 } else { 5547 // Parallel reference processing 5548 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5549 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5550 5551 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5552 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor); 5553 } 5554 5555 // We have completed copying any necessary live referent objects 5556 // (that were not copied during the actual pause) so we can 5557 // retire any active alloc buffers 5558 pss.retire_alloc_buffers(); 5559 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5560 5561 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5562 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5563 } 5564 5565 // Weak Reference processing during an evacuation pause (part 2). 5566 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5567 double ref_enq_start = os::elapsedTime(); 5568 5569 ReferenceProcessor* rp = _ref_processor_stw; 5570 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5571 5572 // Now enqueue any remaining on the discovered lists on to 5573 // the pending list. 5574 if (!rp->processing_is_mt()) { 5575 // Serial reference processing... 5576 rp->enqueue_discovered_references(); 5577 } else { 5578 // Parallel reference enqueuing 5579 5580 assert(no_of_gc_workers == workers()->active_workers(), 5581 "Need to reset active workers"); 5582 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5583 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5584 5585 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5586 rp->enqueue_discovered_references(&par_task_executor); 5587 } 5588 5589 rp->verify_no_references_recorded(); 5590 assert(!rp->discovery_enabled(), "should have been disabled"); 5591 5592 // FIXME 5593 // CM's reference processing also cleans up the string and symbol tables. 5594 // Should we do that here also? We could, but it is a serial operation 5595 // and could signicantly increase the pause time. 5596 5597 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5598 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5599 } 5600 5601 void G1CollectedHeap::evacuate_collection_set() { 5602 _expand_heap_after_alloc_failure = true; 5603 set_evacuation_failed(false); 5604 5605 // Should G1EvacuationFailureALot be in effect for this GC? 5606 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5607 5608 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5609 5610 // Disable the hot card cache. 5611 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5612 hot_card_cache->reset_hot_cache_claimed_index(); 5613 hot_card_cache->set_use_cache(false); 5614 5615 uint n_workers; 5616 if (G1CollectedHeap::use_parallel_gc_threads()) { 5617 n_workers = 5618 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5619 workers()->active_workers(), 5620 Threads::number_of_non_daemon_threads()); 5621 assert(UseDynamicNumberOfGCThreads || 5622 n_workers == workers()->total_workers(), 5623 "If not dynamic should be using all the workers"); 5624 workers()->set_active_workers(n_workers); 5625 set_par_threads(n_workers); 5626 } else { 5627 assert(n_par_threads() == 0, 5628 "Should be the original non-parallel value"); 5629 n_workers = 1; 5630 } 5631 5632 G1ParTask g1_par_task(this, _task_queues); 5633 5634 init_for_evac_failure(NULL); 5635 5636 rem_set()->prepare_for_younger_refs_iterate(true); 5637 5638 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5639 double start_par_time_sec = os::elapsedTime(); 5640 double end_par_time_sec; 5641 5642 { 5643 StrongRootsScope srs(this); 5644 5645 if (G1CollectedHeap::use_parallel_gc_threads()) { 5646 // The individual threads will set their evac-failure closures. 5647 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5648 // These tasks use ShareHeap::_process_strong_tasks 5649 assert(UseDynamicNumberOfGCThreads || 5650 workers()->active_workers() == workers()->total_workers(), 5651 "If not dynamic should be using all the workers"); 5652 workers()->run_task(&g1_par_task); 5653 } else { 5654 g1_par_task.set_for_termination(n_workers); 5655 g1_par_task.work(0); 5656 } 5657 end_par_time_sec = os::elapsedTime(); 5658 5659 // Closing the inner scope will execute the destructor 5660 // for the StrongRootsScope object. We record the current 5661 // elapsed time before closing the scope so that time 5662 // taken for the SRS destructor is NOT included in the 5663 // reported parallel time. 5664 } 5665 5666 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5667 g1_policy()->phase_times()->record_par_time(par_time_ms); 5668 5669 double code_root_fixup_time_ms = 5670 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5671 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5672 5673 set_par_threads(0); 5674 5675 // Process any discovered reference objects - we have 5676 // to do this _before_ we retire the GC alloc regions 5677 // as we may have to copy some 'reachable' referent 5678 // objects (and their reachable sub-graphs) that were 5679 // not copied during the pause. 5680 process_discovered_references(n_workers); 5681 5682 // Weak root processing. 5683 // Note: when JSR 292 is enabled and code blobs can contain 5684 // non-perm oops then we will need to process the code blobs 5685 // here too. 5686 { 5687 G1STWIsAliveClosure is_alive(this); 5688 G1KeepAliveClosure keep_alive(this); 5689 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5690 } 5691 5692 release_gc_alloc_regions(n_workers); 5693 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5694 5695 // Reset and re-enable the hot card cache. 5696 // Note the counts for the cards in the regions in the 5697 // collection set are reset when the collection set is freed. 5698 hot_card_cache->reset_hot_cache(); 5699 hot_card_cache->set_use_cache(true); 5700 5701 finalize_for_evac_failure(); 5702 5703 if (evacuation_failed()) { 5704 remove_self_forwarding_pointers(); 5705 5706 // Reset the G1EvacuationFailureALot counters and flags 5707 // Note: the values are reset only when an actual 5708 // evacuation failure occurs. 5709 NOT_PRODUCT(reset_evacuation_should_fail();) 5710 } 5711 5712 // Enqueue any remaining references remaining on the STW 5713 // reference processor's discovered lists. We need to do 5714 // this after the card table is cleaned (and verified) as 5715 // the act of enqueuing entries on to the pending list 5716 // will log these updates (and dirty their associated 5717 // cards). We need these updates logged to update any 5718 // RSets. 5719 enqueue_discovered_references(n_workers); 5720 5721 if (G1DeferredRSUpdate) { 5722 RedirtyLoggedCardTableEntryFastClosure redirty; 5723 dirty_card_queue_set().set_closure(&redirty); 5724 dirty_card_queue_set().apply_closure_to_all_completed_buffers(); 5725 5726 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5727 dcq.merge_bufferlists(&dirty_card_queue_set()); 5728 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5729 } 5730 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5731 } 5732 5733 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr, 5734 size_t* pre_used, 5735 FreeRegionList* free_list, 5736 OldRegionSet* old_proxy_set, 5737 HumongousRegionSet* humongous_proxy_set, 5738 HRRSCleanupTask* hrrs_cleanup_task, 5739 bool par) { 5740 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 5741 if (hr->isHumongous()) { 5742 assert(hr->startsHumongous(), "we should only see starts humongous"); 5743 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par); 5744 } else { 5745 _old_set.remove_with_proxy(hr, old_proxy_set); 5746 free_region(hr, pre_used, free_list, par); 5747 } 5748 } else { 5749 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task); 5750 } 5751 } 5752 5753 void G1CollectedHeap::free_region(HeapRegion* hr, 5754 size_t* pre_used, 5755 FreeRegionList* free_list, 5756 bool par) { 5757 assert(!hr->isHumongous(), "this is only for non-humongous regions"); 5758 assert(!hr->is_empty(), "the region should not be empty"); 5759 assert(free_list != NULL, "pre-condition"); 5760 5761 // Clear the card counts for this region. 5762 // Note: we only need to do this if the region is not young 5763 // (since we don't refine cards in young regions). 5764 if (!hr->is_young()) { 5765 _cg1r->hot_card_cache()->reset_card_counts(hr); 5766 } 5767 *pre_used += hr->used(); 5768 hr->hr_clear(par, true /* clear_space */); 5769 free_list->add_as_head(hr); 5770 } 5771 5772 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5773 size_t* pre_used, 5774 FreeRegionList* free_list, 5775 HumongousRegionSet* humongous_proxy_set, 5776 bool par) { 5777 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 5778 assert(free_list != NULL, "pre-condition"); 5779 assert(humongous_proxy_set != NULL, "pre-condition"); 5780 5781 size_t hr_used = hr->used(); 5782 size_t hr_capacity = hr->capacity(); 5783 size_t hr_pre_used = 0; 5784 _humongous_set.remove_with_proxy(hr, humongous_proxy_set); 5785 // We need to read this before we make the region non-humongous, 5786 // otherwise the information will be gone. 5787 uint last_index = hr->last_hc_index(); 5788 hr->set_notHumongous(); 5789 free_region(hr, &hr_pre_used, free_list, par); 5790 5791 uint i = hr->hrs_index() + 1; 5792 while (i < last_index) { 5793 HeapRegion* curr_hr = region_at(i); 5794 assert(curr_hr->continuesHumongous(), "invariant"); 5795 curr_hr->set_notHumongous(); 5796 free_region(curr_hr, &hr_pre_used, free_list, par); 5797 i += 1; 5798 } 5799 assert(hr_pre_used == hr_used, 5800 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" " 5801 "should be the same", hr_pre_used, hr_used)); 5802 *pre_used += hr_pre_used; 5803 } 5804 5805 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used, 5806 FreeRegionList* free_list, 5807 OldRegionSet* old_proxy_set, 5808 HumongousRegionSet* humongous_proxy_set, 5809 bool par) { 5810 if (pre_used > 0) { 5811 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL; 5812 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); 5813 assert(_summary_bytes_used >= pre_used, 5814 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" " 5815 "should be >= pre_used: "SIZE_FORMAT, 5816 _summary_bytes_used, pre_used)); 5817 _summary_bytes_used -= pre_used; 5818 } 5819 if (free_list != NULL && !free_list->is_empty()) { 5820 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5821 _free_list.add_as_head(free_list); 5822 } 5823 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) { 5824 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5825 _old_set.update_from_proxy(old_proxy_set); 5826 } 5827 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) { 5828 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5829 _humongous_set.update_from_proxy(humongous_proxy_set); 5830 } 5831 } 5832 5833 class G1ParCleanupCTTask : public AbstractGangTask { 5834 CardTableModRefBS* _ct_bs; 5835 G1CollectedHeap* _g1h; 5836 HeapRegion* volatile _su_head; 5837 public: 5838 G1ParCleanupCTTask(CardTableModRefBS* ct_bs, 5839 G1CollectedHeap* g1h) : 5840 AbstractGangTask("G1 Par Cleanup CT Task"), 5841 _ct_bs(ct_bs), _g1h(g1h) { } 5842 5843 void work(uint worker_id) { 5844 HeapRegion* r; 5845 while (r = _g1h->pop_dirty_cards_region()) { 5846 clear_cards(r); 5847 } 5848 } 5849 5850 void clear_cards(HeapRegion* r) { 5851 // Cards of the survivors should have already been dirtied. 5852 if (!r->is_survivor()) { 5853 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5854 } 5855 } 5856 }; 5857 5858 #ifndef PRODUCT 5859 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5860 G1CollectedHeap* _g1h; 5861 CardTableModRefBS* _ct_bs; 5862 public: 5863 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs) 5864 : _g1h(g1h), _ct_bs(ct_bs) { } 5865 virtual bool doHeapRegion(HeapRegion* r) { 5866 if (r->is_survivor()) { 5867 _g1h->verify_dirty_region(r); 5868 } else { 5869 _g1h->verify_not_dirty_region(r); 5870 } 5871 return false; 5872 } 5873 }; 5874 5875 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5876 // All of the region should be clean. 5877 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 5878 MemRegion mr(hr->bottom(), hr->end()); 5879 ct_bs->verify_not_dirty_region(mr); 5880 } 5881 5882 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5883 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5884 // dirty allocated blocks as they allocate them. The thread that 5885 // retires each region and replaces it with a new one will do a 5886 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5887 // not dirty that area (one less thing to have to do while holding 5888 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5889 // is dirty. 5890 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5891 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5892 ct_bs->verify_dirty_region(mr); 5893 } 5894 5895 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5896 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5897 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5898 verify_dirty_region(hr); 5899 } 5900 } 5901 5902 void G1CollectedHeap::verify_dirty_young_regions() { 5903 verify_dirty_young_list(_young_list->first_region()); 5904 } 5905 #endif 5906 5907 void G1CollectedHeap::cleanUpCardTable() { 5908 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set()); 5909 double start = os::elapsedTime(); 5910 5911 { 5912 // Iterate over the dirty cards region list. 5913 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5914 5915 if (G1CollectedHeap::use_parallel_gc_threads()) { 5916 set_par_threads(); 5917 workers()->run_task(&cleanup_task); 5918 set_par_threads(0); 5919 } else { 5920 while (_dirty_cards_region_list) { 5921 HeapRegion* r = _dirty_cards_region_list; 5922 cleanup_task.clear_cards(r); 5923 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 5924 if (_dirty_cards_region_list == r) { 5925 // The last region. 5926 _dirty_cards_region_list = NULL; 5927 } 5928 r->set_next_dirty_cards_region(NULL); 5929 } 5930 } 5931 #ifndef PRODUCT 5932 if (G1VerifyCTCleanup || VerifyAfterGC) { 5933 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5934 heap_region_iterate(&cleanup_verifier); 5935 } 5936 #endif 5937 } 5938 5939 double elapsed = os::elapsedTime() - start; 5940 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5941 } 5942 5943 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) { 5944 size_t pre_used = 0; 5945 FreeRegionList local_free_list("Local List for CSet Freeing"); 5946 5947 double young_time_ms = 0.0; 5948 double non_young_time_ms = 0.0; 5949 5950 // Since the collection set is a superset of the the young list, 5951 // all we need to do to clear the young list is clear its 5952 // head and length, and unlink any young regions in the code below 5953 _young_list->clear(); 5954 5955 G1CollectorPolicy* policy = g1_policy(); 5956 5957 double start_sec = os::elapsedTime(); 5958 bool non_young = true; 5959 5960 HeapRegion* cur = cs_head; 5961 int age_bound = -1; 5962 size_t rs_lengths = 0; 5963 5964 while (cur != NULL) { 5965 assert(!is_on_master_free_list(cur), "sanity"); 5966 if (non_young) { 5967 if (cur->is_young()) { 5968 double end_sec = os::elapsedTime(); 5969 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5970 non_young_time_ms += elapsed_ms; 5971 5972 start_sec = os::elapsedTime(); 5973 non_young = false; 5974 } 5975 } else { 5976 if (!cur->is_young()) { 5977 double end_sec = os::elapsedTime(); 5978 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5979 young_time_ms += elapsed_ms; 5980 5981 start_sec = os::elapsedTime(); 5982 non_young = true; 5983 } 5984 } 5985 5986 rs_lengths += cur->rem_set()->occupied(); 5987 5988 HeapRegion* next = cur->next_in_collection_set(); 5989 assert(cur->in_collection_set(), "bad CS"); 5990 cur->set_next_in_collection_set(NULL); 5991 cur->set_in_collection_set(false); 5992 5993 if (cur->is_young()) { 5994 int index = cur->young_index_in_cset(); 5995 assert(index != -1, "invariant"); 5996 assert((uint) index < policy->young_cset_region_length(), "invariant"); 5997 size_t words_survived = _surviving_young_words[index]; 5998 cur->record_surv_words_in_group(words_survived); 5999 6000 // At this point the we have 'popped' cur from the collection set 6001 // (linked via next_in_collection_set()) but it is still in the 6002 // young list (linked via next_young_region()). Clear the 6003 // _next_young_region field. 6004 cur->set_next_young_region(NULL); 6005 } else { 6006 int index = cur->young_index_in_cset(); 6007 assert(index == -1, "invariant"); 6008 } 6009 6010 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 6011 (!cur->is_young() && cur->young_index_in_cset() == -1), 6012 "invariant" ); 6013 6014 if (!cur->evacuation_failed()) { 6015 MemRegion used_mr = cur->used_region(); 6016 6017 // And the region is empty. 6018 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6019 free_region(cur, &pre_used, &local_free_list, false /* par */); 6020 } else { 6021 cur->uninstall_surv_rate_group(); 6022 if (cur->is_young()) { 6023 cur->set_young_index_in_cset(-1); 6024 } 6025 cur->set_not_young(); 6026 cur->set_evacuation_failed(false); 6027 // The region is now considered to be old. 6028 _old_set.add(cur); 6029 } 6030 cur = next; 6031 } 6032 6033 policy->record_max_rs_lengths(rs_lengths); 6034 policy->cset_regions_freed(); 6035 6036 double end_sec = os::elapsedTime(); 6037 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6038 6039 if (non_young) { 6040 non_young_time_ms += elapsed_ms; 6041 } else { 6042 young_time_ms += elapsed_ms; 6043 } 6044 6045 update_sets_after_freeing_regions(pre_used, &local_free_list, 6046 NULL /* old_proxy_set */, 6047 NULL /* humongous_proxy_set */, 6048 false /* par */); 6049 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6050 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6051 } 6052 6053 // This routine is similar to the above but does not record 6054 // any policy statistics or update free lists; we are abandoning 6055 // the current incremental collection set in preparation of a 6056 // full collection. After the full GC we will start to build up 6057 // the incremental collection set again. 6058 // This is only called when we're doing a full collection 6059 // and is immediately followed by the tearing down of the young list. 6060 6061 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6062 HeapRegion* cur = cs_head; 6063 6064 while (cur != NULL) { 6065 HeapRegion* next = cur->next_in_collection_set(); 6066 assert(cur->in_collection_set(), "bad CS"); 6067 cur->set_next_in_collection_set(NULL); 6068 cur->set_in_collection_set(false); 6069 cur->set_young_index_in_cset(-1); 6070 cur = next; 6071 } 6072 } 6073 6074 void G1CollectedHeap::set_free_regions_coming() { 6075 if (G1ConcRegionFreeingVerbose) { 6076 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6077 "setting free regions coming"); 6078 } 6079 6080 assert(!free_regions_coming(), "pre-condition"); 6081 _free_regions_coming = true; 6082 } 6083 6084 void G1CollectedHeap::reset_free_regions_coming() { 6085 assert(free_regions_coming(), "pre-condition"); 6086 6087 { 6088 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6089 _free_regions_coming = false; 6090 SecondaryFreeList_lock->notify_all(); 6091 } 6092 6093 if (G1ConcRegionFreeingVerbose) { 6094 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6095 "reset free regions coming"); 6096 } 6097 } 6098 6099 void G1CollectedHeap::wait_while_free_regions_coming() { 6100 // Most of the time we won't have to wait, so let's do a quick test 6101 // first before we take the lock. 6102 if (!free_regions_coming()) { 6103 return; 6104 } 6105 6106 if (G1ConcRegionFreeingVerbose) { 6107 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6108 "waiting for free regions"); 6109 } 6110 6111 { 6112 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6113 while (free_regions_coming()) { 6114 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6115 } 6116 } 6117 6118 if (G1ConcRegionFreeingVerbose) { 6119 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6120 "done waiting for free regions"); 6121 } 6122 } 6123 6124 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6125 assert(heap_lock_held_for_gc(), 6126 "the heap lock should already be held by or for this thread"); 6127 _young_list->push_region(hr); 6128 } 6129 6130 class NoYoungRegionsClosure: public HeapRegionClosure { 6131 private: 6132 bool _success; 6133 public: 6134 NoYoungRegionsClosure() : _success(true) { } 6135 bool doHeapRegion(HeapRegion* r) { 6136 if (r->is_young()) { 6137 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6138 r->bottom(), r->end()); 6139 _success = false; 6140 } 6141 return false; 6142 } 6143 bool success() { return _success; } 6144 }; 6145 6146 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6147 bool ret = _young_list->check_list_empty(check_sample); 6148 6149 if (check_heap) { 6150 NoYoungRegionsClosure closure; 6151 heap_region_iterate(&closure); 6152 ret = ret && closure.success(); 6153 } 6154 6155 return ret; 6156 } 6157 6158 class TearDownRegionSetsClosure : public HeapRegionClosure { 6159 private: 6160 OldRegionSet *_old_set; 6161 6162 public: 6163 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { } 6164 6165 bool doHeapRegion(HeapRegion* r) { 6166 if (r->is_empty()) { 6167 // We ignore empty regions, we'll empty the free list afterwards 6168 } else if (r->is_young()) { 6169 // We ignore young regions, we'll empty the young list afterwards 6170 } else if (r->isHumongous()) { 6171 // We ignore humongous regions, we're not tearing down the 6172 // humongous region set 6173 } else { 6174 // The rest should be old 6175 _old_set->remove(r); 6176 } 6177 return false; 6178 } 6179 6180 ~TearDownRegionSetsClosure() { 6181 assert(_old_set->is_empty(), "post-condition"); 6182 } 6183 }; 6184 6185 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6186 assert_at_safepoint(true /* should_be_vm_thread */); 6187 6188 if (!free_list_only) { 6189 TearDownRegionSetsClosure cl(&_old_set); 6190 heap_region_iterate(&cl); 6191 6192 // Need to do this after the heap iteration to be able to 6193 // recognize the young regions and ignore them during the iteration. 6194 _young_list->empty_list(); 6195 } 6196 _free_list.remove_all(); 6197 } 6198 6199 class RebuildRegionSetsClosure : public HeapRegionClosure { 6200 private: 6201 bool _free_list_only; 6202 OldRegionSet* _old_set; 6203 FreeRegionList* _free_list; 6204 size_t _total_used; 6205 6206 public: 6207 RebuildRegionSetsClosure(bool free_list_only, 6208 OldRegionSet* old_set, FreeRegionList* free_list) : 6209 _free_list_only(free_list_only), 6210 _old_set(old_set), _free_list(free_list), _total_used(0) { 6211 assert(_free_list->is_empty(), "pre-condition"); 6212 if (!free_list_only) { 6213 assert(_old_set->is_empty(), "pre-condition"); 6214 } 6215 } 6216 6217 bool doHeapRegion(HeapRegion* r) { 6218 if (r->continuesHumongous()) { 6219 return false; 6220 } 6221 6222 if (r->is_empty()) { 6223 // Add free regions to the free list 6224 _free_list->add_as_tail(r); 6225 } else if (!_free_list_only) { 6226 assert(!r->is_young(), "we should not come across young regions"); 6227 6228 if (r->isHumongous()) { 6229 // We ignore humongous regions, we left the humongous set unchanged 6230 } else { 6231 // The rest should be old, add them to the old set 6232 _old_set->add(r); 6233 } 6234 _total_used += r->used(); 6235 } 6236 6237 return false; 6238 } 6239 6240 size_t total_used() { 6241 return _total_used; 6242 } 6243 }; 6244 6245 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6246 assert_at_safepoint(true /* should_be_vm_thread */); 6247 6248 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list); 6249 heap_region_iterate(&cl); 6250 6251 if (!free_list_only) { 6252 _summary_bytes_used = cl.total_used(); 6253 } 6254 assert(_summary_bytes_used == recalculate_used(), 6255 err_msg("inconsistent _summary_bytes_used, " 6256 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6257 _summary_bytes_used, recalculate_used())); 6258 } 6259 6260 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6261 _refine_cte_cl->set_concurrent(concurrent); 6262 } 6263 6264 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6265 HeapRegion* hr = heap_region_containing(p); 6266 if (hr == NULL) { 6267 return false; 6268 } else { 6269 return hr->is_in(p); 6270 } 6271 } 6272 6273 // Methods for the mutator alloc region 6274 6275 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6276 bool force) { 6277 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6278 assert(!force || g1_policy()->can_expand_young_list(), 6279 "if force is true we should be able to expand the young list"); 6280 bool young_list_full = g1_policy()->is_young_list_full(); 6281 if (force || !young_list_full) { 6282 HeapRegion* new_alloc_region = new_region(word_size, 6283 false /* do_expand */); 6284 if (new_alloc_region != NULL) { 6285 set_region_short_lived_locked(new_alloc_region); 6286 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6287 return new_alloc_region; 6288 } 6289 } 6290 return NULL; 6291 } 6292 6293 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6294 size_t allocated_bytes) { 6295 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6296 assert(alloc_region->is_young(), "all mutator alloc regions should be young"); 6297 6298 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6299 _summary_bytes_used += allocated_bytes; 6300 _hr_printer.retire(alloc_region); 6301 // We update the eden sizes here, when the region is retired, 6302 // instead of when it's allocated, since this is the point that its 6303 // used space has been recored in _summary_bytes_used. 6304 g1mm()->update_eden_size(); 6305 } 6306 6307 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, 6308 bool force) { 6309 return _g1h->new_mutator_alloc_region(word_size, force); 6310 } 6311 6312 void G1CollectedHeap::set_par_threads() { 6313 // Don't change the number of workers. Use the value previously set 6314 // in the workgroup. 6315 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6316 uint n_workers = workers()->active_workers(); 6317 assert(UseDynamicNumberOfGCThreads || 6318 n_workers == workers()->total_workers(), 6319 "Otherwise should be using the total number of workers"); 6320 if (n_workers == 0) { 6321 assert(false, "Should have been set in prior evacuation pause."); 6322 n_workers = ParallelGCThreads; 6323 workers()->set_active_workers(n_workers); 6324 } 6325 set_par_threads(n_workers); 6326 } 6327 6328 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, 6329 size_t allocated_bytes) { 6330 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); 6331 } 6332 6333 // Methods for the GC alloc regions 6334 6335 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6336 uint count, 6337 GCAllocPurpose ap) { 6338 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6339 6340 if (count < g1_policy()->max_regions(ap)) { 6341 HeapRegion* new_alloc_region = new_region(word_size, 6342 true /* do_expand */); 6343 if (new_alloc_region != NULL) { 6344 // We really only need to do this for old regions given that we 6345 // should never scan survivors. But it doesn't hurt to do it 6346 // for survivors too. 6347 new_alloc_region->set_saved_mark(); 6348 if (ap == GCAllocForSurvived) { 6349 new_alloc_region->set_survivor(); 6350 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6351 } else { 6352 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6353 } 6354 bool during_im = g1_policy()->during_initial_mark_pause(); 6355 new_alloc_region->note_start_of_copying(during_im); 6356 return new_alloc_region; 6357 } else { 6358 g1_policy()->note_alloc_region_limit_reached(ap); 6359 } 6360 } 6361 return NULL; 6362 } 6363 6364 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6365 size_t allocated_bytes, 6366 GCAllocPurpose ap) { 6367 bool during_im = g1_policy()->during_initial_mark_pause(); 6368 alloc_region->note_end_of_copying(during_im); 6369 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6370 if (ap == GCAllocForSurvived) { 6371 young_list()->add_survivor_region(alloc_region); 6372 } else { 6373 _old_set.add(alloc_region); 6374 } 6375 _hr_printer.retire(alloc_region); 6376 } 6377 6378 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, 6379 bool force) { 6380 assert(!force, "not supported for GC alloc regions"); 6381 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); 6382 } 6383 6384 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, 6385 size_t allocated_bytes) { 6386 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6387 GCAllocForSurvived); 6388 } 6389 6390 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, 6391 bool force) { 6392 assert(!force, "not supported for GC alloc regions"); 6393 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); 6394 } 6395 6396 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, 6397 size_t allocated_bytes) { 6398 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6399 GCAllocForTenured); 6400 } 6401 // Heap region set verification 6402 6403 class VerifyRegionListsClosure : public HeapRegionClosure { 6404 private: 6405 FreeRegionList* _free_list; 6406 OldRegionSet* _old_set; 6407 HumongousRegionSet* _humongous_set; 6408 uint _region_count; 6409 6410 public: 6411 VerifyRegionListsClosure(OldRegionSet* old_set, 6412 HumongousRegionSet* humongous_set, 6413 FreeRegionList* free_list) : 6414 _old_set(old_set), _humongous_set(humongous_set), 6415 _free_list(free_list), _region_count(0) { } 6416 6417 uint region_count() { return _region_count; } 6418 6419 bool doHeapRegion(HeapRegion* hr) { 6420 _region_count += 1; 6421 6422 if (hr->continuesHumongous()) { 6423 return false; 6424 } 6425 6426 if (hr->is_young()) { 6427 // TODO 6428 } else if (hr->startsHumongous()) { 6429 _humongous_set->verify_next_region(hr); 6430 } else if (hr->is_empty()) { 6431 _free_list->verify_next_region(hr); 6432 } else { 6433 _old_set->verify_next_region(hr); 6434 } 6435 return false; 6436 } 6437 }; 6438 6439 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 6440 HeapWord* bottom) { 6441 HeapWord* end = bottom + HeapRegion::GrainWords; 6442 MemRegion mr(bottom, end); 6443 assert(_g1_reserved.contains(mr), "invariant"); 6444 // This might return NULL if the allocation fails 6445 return new HeapRegion(hrs_index, _bot_shared, mr); 6446 } 6447 6448 void G1CollectedHeap::verify_region_sets() { 6449 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6450 6451 // First, check the explicit lists. 6452 _free_list.verify(); 6453 { 6454 // Given that a concurrent operation might be adding regions to 6455 // the secondary free list we have to take the lock before 6456 // verifying it. 6457 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6458 _secondary_free_list.verify(); 6459 } 6460 _old_set.verify(); 6461 _humongous_set.verify(); 6462 6463 // If a concurrent region freeing operation is in progress it will 6464 // be difficult to correctly attributed any free regions we come 6465 // across to the correct free list given that they might belong to 6466 // one of several (free_list, secondary_free_list, any local lists, 6467 // etc.). So, if that's the case we will skip the rest of the 6468 // verification operation. Alternatively, waiting for the concurrent 6469 // operation to complete will have a non-trivial effect on the GC's 6470 // operation (no concurrent operation will last longer than the 6471 // interval between two calls to verification) and it might hide 6472 // any issues that we would like to catch during testing. 6473 if (free_regions_coming()) { 6474 return; 6475 } 6476 6477 // Make sure we append the secondary_free_list on the free_list so 6478 // that all free regions we will come across can be safely 6479 // attributed to the free_list. 6480 append_secondary_free_list_if_not_empty_with_lock(); 6481 6482 // Finally, make sure that the region accounting in the lists is 6483 // consistent with what we see in the heap. 6484 _old_set.verify_start(); 6485 _humongous_set.verify_start(); 6486 _free_list.verify_start(); 6487 6488 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list); 6489 heap_region_iterate(&cl); 6490 6491 _old_set.verify_end(); 6492 _humongous_set.verify_end(); 6493 _free_list.verify_end(); 6494 }