1 /* 2 * Copyright (c) 2001, 2014, 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 #if !defined(__clang_major__) && defined(__GNUC__) 26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess. 27 #endif 28 29 #include "precompiled.hpp" 30 #include "classfile/metadataOnStackMark.hpp" 31 #include "code/codeCache.hpp" 32 #include "code/icBuffer.hpp" 33 #include "gc_implementation/g1/bufferingOopClosure.hpp" 34 #include "gc_implementation/g1/concurrentG1Refine.hpp" 35 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 36 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" 37 #include "gc_implementation/g1/g1AllocRegion.inline.hpp" 38 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 39 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 40 #include "gc_implementation/g1/g1ErgoVerbose.hpp" 41 #include "gc_implementation/g1/g1EvacFailure.hpp" 42 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 43 #include "gc_implementation/g1/g1Log.hpp" 44 #include "gc_implementation/g1/g1MarkSweep.hpp" 45 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 46 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp" 47 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp" 48 #include "gc_implementation/g1/g1RemSet.inline.hpp" 49 #include "gc_implementation/g1/g1StringDedup.hpp" 50 #include "gc_implementation/g1/g1YCTypes.hpp" 51 #include "gc_implementation/g1/heapRegion.inline.hpp" 52 #include "gc_implementation/g1/heapRegionRemSet.hpp" 53 #include "gc_implementation/g1/heapRegionSet.inline.hpp" 54 #include "gc_implementation/g1/vm_operations_g1.hpp" 55 #include "gc_implementation/shared/gcHeapSummary.hpp" 56 #include "gc_implementation/shared/gcTimer.hpp" 57 #include "gc_implementation/shared/gcTrace.hpp" 58 #include "gc_implementation/shared/gcTraceTime.hpp" 59 #include "gc_implementation/shared/isGCActiveMark.hpp" 60 #include "memory/allocation.hpp" 61 #include "memory/gcLocker.inline.hpp" 62 #include "memory/generationSpec.hpp" 63 #include "memory/iterator.hpp" 64 #include "memory/referenceProcessor.hpp" 65 #include "oops/oop.inline.hpp" 66 #include "oops/oop.pcgc.inline.hpp" 67 #include "runtime/orderAccess.inline.hpp" 68 #include "runtime/vmThread.hpp" 69 70 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 71 72 // turn it on so that the contents of the young list (scan-only / 73 // to-be-collected) are printed at "strategic" points before / during 74 // / after the collection --- this is useful for debugging 75 #define YOUNG_LIST_VERBOSE 0 76 // CURRENT STATUS 77 // This file is under construction. Search for "FIXME". 78 79 // INVARIANTS/NOTES 80 // 81 // All allocation activity covered by the G1CollectedHeap interface is 82 // serialized by acquiring the HeapLock. This happens in mem_allocate 83 // and allocate_new_tlab, which are the "entry" points to the 84 // allocation code from the rest of the JVM. (Note that this does not 85 // apply to TLAB allocation, which is not part of this interface: it 86 // is done by clients of this interface.) 87 88 // Notes on implementation of parallelism in different tasks. 89 // 90 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism. 91 // The number of GC workers is passed to heap_region_par_iterate_chunked(). 92 // It does use run_task() which sets _n_workers in the task. 93 // G1ParTask executes g1_process_roots() -> 94 // SharedHeap::process_roots() which calls eventually to 95 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses 96 // SequentialSubTasksDone. SharedHeap::process_roots() also 97 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap). 98 // 99 100 // Local to this file. 101 102 class RefineCardTableEntryClosure: public CardTableEntryClosure { 103 bool _concurrent; 104 public: 105 RefineCardTableEntryClosure() : _concurrent(true) { } 106 107 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 108 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 109 // This path is executed by the concurrent refine or mutator threads, 110 // concurrently, and so we do not care if card_ptr contains references 111 // that point into the collection set. 112 assert(!oops_into_cset, "should be"); 113 114 if (_concurrent && SuspendibleThreadSet::should_yield()) { 115 // Caller will actually yield. 116 return false; 117 } 118 // Otherwise, we finished successfully; return true. 119 return true; 120 } 121 122 void set_concurrent(bool b) { _concurrent = b; } 123 }; 124 125 126 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 127 size_t _num_processed; 128 CardTableModRefBS* _ctbs; 129 int _histo[256]; 130 131 public: 132 ClearLoggedCardTableEntryClosure() : 133 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set()) 134 { 135 for (int i = 0; i < 256; i++) _histo[i] = 0; 136 } 137 138 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 139 unsigned char* ujb = (unsigned char*)card_ptr; 140 int ind = (int)(*ujb); 141 _histo[ind]++; 142 143 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val(); 144 _num_processed++; 145 146 return true; 147 } 148 149 size_t num_processed() { return _num_processed; } 150 151 void print_histo() { 152 gclog_or_tty->print_cr("Card table value histogram:"); 153 for (int i = 0; i < 256; i++) { 154 if (_histo[i] != 0) { 155 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); 156 } 157 } 158 } 159 }; 160 161 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 162 private: 163 size_t _num_processed; 164 165 public: 166 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 167 168 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 169 *card_ptr = CardTableModRefBS::dirty_card_val(); 170 _num_processed++; 171 return true; 172 } 173 174 size_t num_processed() const { return _num_processed; } 175 }; 176 177 YoungList::YoungList(G1CollectedHeap* g1h) : 178 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 179 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 180 guarantee(check_list_empty(false), "just making sure..."); 181 } 182 183 void YoungList::push_region(HeapRegion *hr) { 184 assert(!hr->is_young(), "should not already be young"); 185 assert(hr->get_next_young_region() == NULL, "cause it should!"); 186 187 hr->set_next_young_region(_head); 188 _head = hr; 189 190 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 191 ++_length; 192 } 193 194 void YoungList::add_survivor_region(HeapRegion* hr) { 195 assert(hr->is_survivor(), "should be flagged as survivor region"); 196 assert(hr->get_next_young_region() == NULL, "cause it should!"); 197 198 hr->set_next_young_region(_survivor_head); 199 if (_survivor_head == NULL) { 200 _survivor_tail = hr; 201 } 202 _survivor_head = hr; 203 ++_survivor_length; 204 } 205 206 void YoungList::empty_list(HeapRegion* list) { 207 while (list != NULL) { 208 HeapRegion* next = list->get_next_young_region(); 209 list->set_next_young_region(NULL); 210 list->uninstall_surv_rate_group(); 211 // This is called before a Full GC and all the non-empty / 212 // non-humongous regions at the end of the Full GC will end up as 213 // old anyway. 214 list->set_old(); 215 list = next; 216 } 217 } 218 219 void YoungList::empty_list() { 220 assert(check_list_well_formed(), "young list should be well formed"); 221 222 empty_list(_head); 223 _head = NULL; 224 _length = 0; 225 226 empty_list(_survivor_head); 227 _survivor_head = NULL; 228 _survivor_tail = NULL; 229 _survivor_length = 0; 230 231 _last_sampled_rs_lengths = 0; 232 233 assert(check_list_empty(false), "just making sure..."); 234 } 235 236 bool YoungList::check_list_well_formed() { 237 bool ret = true; 238 239 uint length = 0; 240 HeapRegion* curr = _head; 241 HeapRegion* last = NULL; 242 while (curr != NULL) { 243 if (!curr->is_young()) { 244 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 245 "incorrectly tagged (y: %d, surv: %d)", 246 curr->bottom(), curr->end(), 247 curr->is_young(), curr->is_survivor()); 248 ret = false; 249 } 250 ++length; 251 last = curr; 252 curr = curr->get_next_young_region(); 253 } 254 ret = ret && (length == _length); 255 256 if (!ret) { 257 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 258 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 259 length, _length); 260 } 261 262 return ret; 263 } 264 265 bool YoungList::check_list_empty(bool check_sample) { 266 bool ret = true; 267 268 if (_length != 0) { 269 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 270 _length); 271 ret = false; 272 } 273 if (check_sample && _last_sampled_rs_lengths != 0) { 274 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 275 ret = false; 276 } 277 if (_head != NULL) { 278 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 279 ret = false; 280 } 281 if (!ret) { 282 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 283 } 284 285 return ret; 286 } 287 288 void 289 YoungList::rs_length_sampling_init() { 290 _sampled_rs_lengths = 0; 291 _curr = _head; 292 } 293 294 bool 295 YoungList::rs_length_sampling_more() { 296 return _curr != NULL; 297 } 298 299 void 300 YoungList::rs_length_sampling_next() { 301 assert( _curr != NULL, "invariant" ); 302 size_t rs_length = _curr->rem_set()->occupied(); 303 304 _sampled_rs_lengths += rs_length; 305 306 // The current region may not yet have been added to the 307 // incremental collection set (it gets added when it is 308 // retired as the current allocation region). 309 if (_curr->in_collection_set()) { 310 // Update the collection set policy information for this region 311 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 312 } 313 314 _curr = _curr->get_next_young_region(); 315 if (_curr == NULL) { 316 _last_sampled_rs_lengths = _sampled_rs_lengths; 317 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 318 } 319 } 320 321 void 322 YoungList::reset_auxilary_lists() { 323 guarantee( is_empty(), "young list should be empty" ); 324 assert(check_list_well_formed(), "young list should be well formed"); 325 326 // Add survivor regions to SurvRateGroup. 327 _g1h->g1_policy()->note_start_adding_survivor_regions(); 328 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 329 330 int young_index_in_cset = 0; 331 for (HeapRegion* curr = _survivor_head; 332 curr != NULL; 333 curr = curr->get_next_young_region()) { 334 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 335 336 // The region is a non-empty survivor so let's add it to 337 // the incremental collection set for the next evacuation 338 // pause. 339 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 340 young_index_in_cset += 1; 341 } 342 assert((uint) young_index_in_cset == _survivor_length, "post-condition"); 343 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 344 345 _head = _survivor_head; 346 _length = _survivor_length; 347 if (_survivor_head != NULL) { 348 assert(_survivor_tail != NULL, "cause it shouldn't be"); 349 assert(_survivor_length > 0, "invariant"); 350 _survivor_tail->set_next_young_region(NULL); 351 } 352 353 // Don't clear the survivor list handles until the start of 354 // the next evacuation pause - we need it in order to re-tag 355 // the survivor regions from this evacuation pause as 'young' 356 // at the start of the next. 357 358 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 359 360 assert(check_list_well_formed(), "young list should be well formed"); 361 } 362 363 void YoungList::print() { 364 HeapRegion* lists[] = {_head, _survivor_head}; 365 const char* names[] = {"YOUNG", "SURVIVOR"}; 366 367 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { 368 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 369 HeapRegion *curr = lists[list]; 370 if (curr == NULL) 371 gclog_or_tty->print_cr(" empty"); 372 while (curr != NULL) { 373 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d", 374 HR_FORMAT_PARAMS(curr), 375 curr->prev_top_at_mark_start(), 376 curr->next_top_at_mark_start(), 377 curr->age_in_surv_rate_group_cond()); 378 curr = curr->get_next_young_region(); 379 } 380 } 381 382 gclog_or_tty->cr(); 383 } 384 385 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 386 OtherRegionsTable::invalidate(start_idx, num_regions); 387 } 388 389 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 390 // The from card cache is not the memory that is actually committed. So we cannot 391 // take advantage of the zero_filled parameter. 392 reset_from_card_cache(start_idx, num_regions); 393 } 394 395 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 396 { 397 // Claim the right to put the region on the dirty cards region list 398 // by installing a self pointer. 399 HeapRegion* next = hr->get_next_dirty_cards_region(); 400 if (next == NULL) { 401 HeapRegion* res = (HeapRegion*) 402 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 403 NULL); 404 if (res == NULL) { 405 HeapRegion* head; 406 do { 407 // Put the region to the dirty cards region list. 408 head = _dirty_cards_region_list; 409 next = (HeapRegion*) 410 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 411 if (next == head) { 412 assert(hr->get_next_dirty_cards_region() == hr, 413 "hr->get_next_dirty_cards_region() != hr"); 414 if (next == NULL) { 415 // The last region in the list points to itself. 416 hr->set_next_dirty_cards_region(hr); 417 } else { 418 hr->set_next_dirty_cards_region(next); 419 } 420 } 421 } while (next != head); 422 } 423 } 424 } 425 426 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 427 { 428 HeapRegion* head; 429 HeapRegion* hr; 430 do { 431 head = _dirty_cards_region_list; 432 if (head == NULL) { 433 return NULL; 434 } 435 HeapRegion* new_head = head->get_next_dirty_cards_region(); 436 if (head == new_head) { 437 // The last region. 438 new_head = NULL; 439 } 440 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 441 head); 442 } while (hr != head); 443 assert(hr != NULL, "invariant"); 444 hr->set_next_dirty_cards_region(NULL); 445 return hr; 446 } 447 448 #ifdef ASSERT 449 // A region is added to the collection set as it is retired 450 // so an address p can point to a region which will be in the 451 // collection set but has not yet been retired. This method 452 // therefore is only accurate during a GC pause after all 453 // regions have been retired. It is used for debugging 454 // to check if an nmethod has references to objects that can 455 // be move during a partial collection. Though it can be 456 // inaccurate, it is sufficient for G1 because the conservative 457 // implementation of is_scavengable() for G1 will indicate that 458 // all nmethods must be scanned during a partial collection. 459 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 460 if (p == NULL) { 461 return false; 462 } 463 return heap_region_containing(p)->in_collection_set(); 464 } 465 #endif 466 467 // Returns true if the reference points to an object that 468 // can move in an incremental collection. 469 bool G1CollectedHeap::is_scavengable(const void* p) { 470 HeapRegion* hr = heap_region_containing(p); 471 return !hr->isHumongous(); 472 } 473 474 void G1CollectedHeap::check_ct_logs_at_safepoint() { 475 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 476 CardTableModRefBS* ct_bs = g1_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.apply_closure_to_all_completed_buffers(&clear); 486 dcqs.iterate_closure_all_threads(&clear, false); 487 clear.print_histo(); 488 489 // Now ensure that there's no dirty cards. 490 CountNonCleanMemRegionClosure count2(this); 491 ct_bs->mod_card_iterate(&count2); 492 if (count2.n() != 0) { 493 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 494 count2.n(), orig_count); 495 } 496 guarantee(count2.n() == 0, "Card table should be clean."); 497 498 RedirtyLoggedCardTableEntryClosure redirty; 499 dcqs.apply_closure_to_all_completed_buffers(&redirty); 500 dcqs.iterate_closure_all_threads(&redirty, false); 501 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 502 clear.num_processed(), orig_count); 503 guarantee(redirty.num_processed() == clear.num_processed(), 504 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT, 505 redirty.num_processed(), clear.num_processed())); 506 507 CountNonCleanMemRegionClosure count3(this); 508 ct_bs->mod_card_iterate(&count3); 509 if (count3.n() != orig_count) { 510 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 511 orig_count, count3.n()); 512 guarantee(count3.n() >= orig_count, "Should have restored them all."); 513 } 514 } 515 516 // Private class members. 517 518 G1CollectedHeap* G1CollectedHeap::_g1h; 519 520 // Private methods. 521 522 HeapRegion* 523 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 524 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 525 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 526 if (!_secondary_free_list.is_empty()) { 527 if (G1ConcRegionFreeingVerbose) { 528 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 529 "secondary_free_list has %u entries", 530 _secondary_free_list.length()); 531 } 532 // It looks as if there are free regions available on the 533 // secondary_free_list. Let's move them to the free_list and try 534 // again to allocate from it. 535 append_secondary_free_list(); 536 537 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 538 "empty we should have moved at least one entry to the free_list"); 539 HeapRegion* res = _hrm.allocate_free_region(is_old); 540 if (G1ConcRegionFreeingVerbose) { 541 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 542 "allocated "HR_FORMAT" from secondary_free_list", 543 HR_FORMAT_PARAMS(res)); 544 } 545 return res; 546 } 547 548 // Wait here until we get notified either when (a) there are no 549 // more free regions coming or (b) some regions have been moved on 550 // the secondary_free_list. 551 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 552 } 553 554 if (G1ConcRegionFreeingVerbose) { 555 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 556 "could not allocate from secondary_free_list"); 557 } 558 return NULL; 559 } 560 561 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 562 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords, 563 "the only time we use this to allocate a humongous region is " 564 "when we are allocating a single humongous region"); 565 566 HeapRegion* res; 567 if (G1StressConcRegionFreeing) { 568 if (!_secondary_free_list.is_empty()) { 569 if (G1ConcRegionFreeingVerbose) { 570 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 571 "forced to look at the secondary_free_list"); 572 } 573 res = new_region_try_secondary_free_list(is_old); 574 if (res != NULL) { 575 return res; 576 } 577 } 578 } 579 580 res = _hrm.allocate_free_region(is_old); 581 582 if (res == NULL) { 583 if (G1ConcRegionFreeingVerbose) { 584 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 585 "res == NULL, trying the secondary_free_list"); 586 } 587 res = new_region_try_secondary_free_list(is_old); 588 } 589 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 590 // Currently, only attempts to allocate GC alloc regions set 591 // do_expand to true. So, we should only reach here during a 592 // safepoint. If this assumption changes we might have to 593 // reconsider the use of _expand_heap_after_alloc_failure. 594 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 595 596 ergo_verbose1(ErgoHeapSizing, 597 "attempt heap expansion", 598 ergo_format_reason("region allocation request failed") 599 ergo_format_byte("allocation request"), 600 word_size * HeapWordSize); 601 if (expand(word_size * HeapWordSize)) { 602 // Given that expand() succeeded in expanding the heap, and we 603 // always expand the heap by an amount aligned to the heap 604 // region size, the free list should in theory not be empty. 605 // In either case allocate_free_region() will check for NULL. 606 res = _hrm.allocate_free_region(is_old); 607 } else { 608 _expand_heap_after_alloc_failure = false; 609 } 610 } 611 return res; 612 } 613 614 HeapWord* 615 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 616 uint num_regions, 617 size_t word_size, 618 AllocationContext_t context) { 619 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 620 assert(isHumongous(word_size), "word_size should be humongous"); 621 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 622 623 // Index of last region in the series + 1. 624 uint last = first + num_regions; 625 626 // We need to initialize the region(s) we just discovered. This is 627 // a bit tricky given that it can happen concurrently with 628 // refinement threads refining cards on these regions and 629 // potentially wanting to refine the BOT as they are scanning 630 // those cards (this can happen shortly after a cleanup; see CR 631 // 6991377). So we have to set up the region(s) carefully and in 632 // a specific order. 633 634 // The word size sum of all the regions we will allocate. 635 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 636 assert(word_size <= word_size_sum, "sanity"); 637 638 // This will be the "starts humongous" region. 639 HeapRegion* first_hr = region_at(first); 640 // The header of the new object will be placed at the bottom of 641 // the first region. 642 HeapWord* new_obj = first_hr->bottom(); 643 // This will be the new end of the first region in the series that 644 // should also match the end of the last region in the series. 645 HeapWord* new_end = new_obj + word_size_sum; 646 // This will be the new top of the first region that will reflect 647 // this allocation. 648 HeapWord* new_top = new_obj + word_size; 649 650 // First, we need to zero the header of the space that we will be 651 // allocating. When we update top further down, some refinement 652 // threads might try to scan the region. By zeroing the header we 653 // ensure that any thread that will try to scan the region will 654 // come across the zero klass word and bail out. 655 // 656 // NOTE: It would not have been correct to have used 657 // CollectedHeap::fill_with_object() and make the space look like 658 // an int array. The thread that is doing the allocation will 659 // later update the object header to a potentially different array 660 // type and, for a very short period of time, the klass and length 661 // fields will be inconsistent. This could cause a refinement 662 // thread to calculate the object size incorrectly. 663 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 664 665 // We will set up the first region as "starts humongous". This 666 // will also update the BOT covering all the regions to reflect 667 // that there is a single object that starts at the bottom of the 668 // first region. 669 first_hr->set_startsHumongous(new_top, new_end); 670 first_hr->set_allocation_context(context); 671 // Then, if there are any, we will set up the "continues 672 // humongous" regions. 673 HeapRegion* hr = NULL; 674 for (uint i = first + 1; i < last; ++i) { 675 hr = region_at(i); 676 hr->set_continuesHumongous(first_hr); 677 hr->set_allocation_context(context); 678 } 679 // If we have "continues humongous" regions (hr != NULL), then the 680 // end of the last one should match new_end. 681 assert(hr == NULL || hr->end() == new_end, "sanity"); 682 683 // Up to this point no concurrent thread would have been able to 684 // do any scanning on any region in this series. All the top 685 // fields still point to bottom, so the intersection between 686 // [bottom,top] and [card_start,card_end] will be empty. Before we 687 // update the top fields, we'll do a storestore to make sure that 688 // no thread sees the update to top before the zeroing of the 689 // object header and the BOT initialization. 690 OrderAccess::storestore(); 691 692 // Now that the BOT and the object header have been initialized, 693 // we can update top of the "starts humongous" region. 694 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 695 "new_top should be in this region"); 696 first_hr->set_top(new_top); 697 if (_hr_printer.is_active()) { 698 HeapWord* bottom = first_hr->bottom(); 699 HeapWord* end = first_hr->orig_end(); 700 if ((first + 1) == last) { 701 // the series has a single humongous region 702 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 703 } else { 704 // the series has more than one humongous regions 705 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 706 } 707 } 708 709 // Now, we will update the top fields of the "continues humongous" 710 // regions. The reason we need to do this is that, otherwise, 711 // these regions would look empty and this will confuse parts of 712 // G1. For example, the code that looks for a consecutive number 713 // of empty regions will consider them empty and try to 714 // re-allocate them. We can extend is_empty() to also include 715 // !continuesHumongous(), but it is easier to just update the top 716 // fields here. The way we set top for all regions (i.e., top == 717 // end for all regions but the last one, top == new_top for the 718 // last one) is actually used when we will free up the humongous 719 // region in free_humongous_region(). 720 hr = NULL; 721 for (uint i = first + 1; i < last; ++i) { 722 hr = region_at(i); 723 if ((i + 1) == last) { 724 // last continues humongous region 725 assert(hr->bottom() < new_top && new_top <= hr->end(), 726 "new_top should fall on this region"); 727 hr->set_top(new_top); 728 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 729 } else { 730 // not last one 731 assert(new_top > hr->end(), "new_top should be above this region"); 732 hr->set_top(hr->end()); 733 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 734 } 735 } 736 // If we have continues humongous regions (hr != NULL), then the 737 // end of the last one should match new_end and its top should 738 // match new_top. 739 assert(hr == NULL || 740 (hr->end() == new_end && hr->top() == new_top), "sanity"); 741 check_bitmaps("Humongous Region Allocation", first_hr); 742 743 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 744 _allocator->increase_used(first_hr->used()); 745 _humongous_set.add(first_hr); 746 747 return new_obj; 748 } 749 750 // If could fit into free regions w/o expansion, try. 751 // Otherwise, if can expand, do so. 752 // Otherwise, if using ex regions might help, try with ex given back. 753 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 754 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 755 756 verify_region_sets_optional(); 757 758 uint first = G1_NO_HRM_INDEX; 759 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 760 761 if (obj_regions == 1) { 762 // Only one region to allocate, try to use a fast path by directly allocating 763 // from the free lists. Do not try to expand here, we will potentially do that 764 // later. 765 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 766 if (hr != NULL) { 767 first = hr->hrm_index(); 768 } 769 } else { 770 // We can't allocate humongous regions spanning more than one region while 771 // cleanupComplete() is running, since some of the regions we find to be 772 // empty might not yet be added to the free list. It is not straightforward 773 // to know in which list they are on so that we can remove them. We only 774 // need to do this if we need to allocate more than one region to satisfy the 775 // current humongous allocation request. If we are only allocating one region 776 // we use the one-region region allocation code (see above), that already 777 // potentially waits for regions from the secondary free list. 778 wait_while_free_regions_coming(); 779 append_secondary_free_list_if_not_empty_with_lock(); 780 781 // Policy: Try only empty regions (i.e. already committed first). Maybe we 782 // are lucky enough to find some. 783 first = _hrm.find_contiguous_only_empty(obj_regions); 784 if (first != G1_NO_HRM_INDEX) { 785 _hrm.allocate_free_regions_starting_at(first, obj_regions); 786 } 787 } 788 789 if (first == G1_NO_HRM_INDEX) { 790 // Policy: We could not find enough regions for the humongous object in the 791 // free list. Look through the heap to find a mix of free and uncommitted regions. 792 // If so, try expansion. 793 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 794 if (first != G1_NO_HRM_INDEX) { 795 // We found something. Make sure these regions are committed, i.e. expand 796 // the heap. Alternatively we could do a defragmentation GC. 797 ergo_verbose1(ErgoHeapSizing, 798 "attempt heap expansion", 799 ergo_format_reason("humongous allocation request failed") 800 ergo_format_byte("allocation request"), 801 word_size * HeapWordSize); 802 803 _hrm.expand_at(first, obj_regions); 804 g1_policy()->record_new_heap_size(num_regions()); 805 806 #ifdef ASSERT 807 for (uint i = first; i < first + obj_regions; ++i) { 808 HeapRegion* hr = region_at(i); 809 assert(hr->is_free(), "sanity"); 810 assert(hr->is_empty(), "sanity"); 811 assert(is_on_master_free_list(hr), "sanity"); 812 } 813 #endif 814 _hrm.allocate_free_regions_starting_at(first, obj_regions); 815 } else { 816 // Policy: Potentially trigger a defragmentation GC. 817 } 818 } 819 820 HeapWord* result = NULL; 821 if (first != G1_NO_HRM_INDEX) { 822 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 823 word_size, context); 824 assert(result != NULL, "it should always return a valid result"); 825 826 // A successful humongous object allocation changes the used space 827 // information of the old generation so we need to recalculate the 828 // sizes and update the jstat counters here. 829 g1mm()->update_sizes(); 830 } 831 832 verify_region_sets_optional(); 833 834 return result; 835 } 836 837 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 838 assert_heap_not_locked_and_not_at_safepoint(); 839 assert(!isHumongous(word_size), "we do not allow humongous TLABs"); 840 841 unsigned int dummy_gc_count_before; 842 int dummy_gclocker_retry_count = 0; 843 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 844 } 845 846 HeapWord* 847 G1CollectedHeap::mem_allocate(size_t word_size, 848 bool* gc_overhead_limit_was_exceeded) { 849 assert_heap_not_locked_and_not_at_safepoint(); 850 851 // Loop until the allocation is satisfied, or unsatisfied after GC. 852 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 853 unsigned int gc_count_before; 854 855 HeapWord* result = NULL; 856 if (!isHumongous(word_size)) { 857 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 858 } else { 859 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 860 } 861 if (result != NULL) { 862 return result; 863 } 864 865 // Create the garbage collection operation... 866 VM_G1CollectForAllocation op(gc_count_before, word_size); 867 op.set_allocation_context(AllocationContext::current()); 868 869 // ...and get the VM thread to execute it. 870 VMThread::execute(&op); 871 872 if (op.prologue_succeeded() && op.pause_succeeded()) { 873 // If the operation was successful we'll return the result even 874 // if it is NULL. If the allocation attempt failed immediately 875 // after a Full GC, it's unlikely we'll be able to allocate now. 876 HeapWord* result = op.result(); 877 if (result != NULL && !isHumongous(word_size)) { 878 // Allocations that take place on VM operations do not do any 879 // card dirtying and we have to do it here. We only have to do 880 // this for non-humongous allocations, though. 881 dirty_young_block(result, word_size); 882 } 883 return result; 884 } else { 885 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 886 return NULL; 887 } 888 assert(op.result() == NULL, 889 "the result should be NULL if the VM op did not succeed"); 890 } 891 892 // Give a warning if we seem to be looping forever. 893 if ((QueuedAllocationWarningCount > 0) && 894 (try_count % QueuedAllocationWarningCount == 0)) { 895 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 896 } 897 } 898 899 ShouldNotReachHere(); 900 return NULL; 901 } 902 903 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 904 AllocationContext_t context, 905 unsigned int *gc_count_before_ret, 906 int* gclocker_retry_count_ret) { 907 // Make sure you read the note in attempt_allocation_humongous(). 908 909 assert_heap_not_locked_and_not_at_safepoint(); 910 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 911 "be called for humongous allocation requests"); 912 913 // We should only get here after the first-level allocation attempt 914 // (attempt_allocation()) failed to allocate. 915 916 // We will loop until a) we manage to successfully perform the 917 // allocation or b) we successfully schedule a collection which 918 // fails to perform the allocation. b) is the only case when we'll 919 // return NULL. 920 HeapWord* result = NULL; 921 for (int try_count = 1; /* we'll return */; try_count += 1) { 922 bool should_try_gc; 923 unsigned int gc_count_before; 924 925 { 926 MutexLockerEx x(Heap_lock); 927 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 928 false /* bot_updates */); 929 if (result != NULL) { 930 return result; 931 } 932 933 // If we reach here, attempt_allocation_locked() above failed to 934 // allocate a new region. So the mutator alloc region should be NULL. 935 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here"); 936 937 if (GC_locker::is_active_and_needs_gc()) { 938 if (g1_policy()->can_expand_young_list()) { 939 // No need for an ergo verbose message here, 940 // can_expand_young_list() does this when it returns true. 941 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size, 942 false /* bot_updates */); 943 if (result != NULL) { 944 return result; 945 } 946 } 947 should_try_gc = false; 948 } else { 949 // The GCLocker may not be active but the GCLocker initiated 950 // GC may not yet have been performed (GCLocker::needs_gc() 951 // returns true). In this case we do not try this GC and 952 // wait until the GCLocker initiated GC is performed, and 953 // then retry the allocation. 954 if (GC_locker::needs_gc()) { 955 should_try_gc = false; 956 } else { 957 // Read the GC count while still holding the Heap_lock. 958 gc_count_before = total_collections(); 959 should_try_gc = true; 960 } 961 } 962 } 963 964 if (should_try_gc) { 965 bool succeeded; 966 result = do_collection_pause(word_size, gc_count_before, &succeeded, 967 GCCause::_g1_inc_collection_pause); 968 if (result != NULL) { 969 assert(succeeded, "only way to get back a non-NULL result"); 970 return result; 971 } 972 973 if (succeeded) { 974 // If we get here we successfully scheduled a collection which 975 // failed to allocate. No point in trying to allocate 976 // further. We'll just return NULL. 977 MutexLockerEx x(Heap_lock); 978 *gc_count_before_ret = total_collections(); 979 return NULL; 980 } 981 } else { 982 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 983 MutexLockerEx x(Heap_lock); 984 *gc_count_before_ret = total_collections(); 985 return NULL; 986 } 987 // The GCLocker is either active or the GCLocker initiated 988 // GC has not yet been performed. Stall until it is and 989 // then retry the allocation. 990 GC_locker::stall_until_clear(); 991 (*gclocker_retry_count_ret) += 1; 992 } 993 994 // We can reach here if we were unsuccessful in scheduling a 995 // collection (because another thread beat us to it) or if we were 996 // stalled due to the GC locker. In either can we should retry the 997 // allocation attempt in case another thread successfully 998 // performed a collection and reclaimed enough space. We do the 999 // first attempt (without holding the Heap_lock) here and the 1000 // follow-on attempt will be at the start of the next loop 1001 // iteration (after taking the Heap_lock). 1002 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size, 1003 false /* bot_updates */); 1004 if (result != NULL) { 1005 return result; 1006 } 1007 1008 // Give a warning if we seem to be looping forever. 1009 if ((QueuedAllocationWarningCount > 0) && 1010 (try_count % QueuedAllocationWarningCount == 0)) { 1011 warning("G1CollectedHeap::attempt_allocation_slow() " 1012 "retries %d times", try_count); 1013 } 1014 } 1015 1016 ShouldNotReachHere(); 1017 return NULL; 1018 } 1019 1020 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1021 unsigned int * gc_count_before_ret, 1022 int* gclocker_retry_count_ret) { 1023 // The structure of this method has a lot of similarities to 1024 // attempt_allocation_slow(). The reason these two were not merged 1025 // into a single one is that such a method would require several "if 1026 // allocation is not humongous do this, otherwise do that" 1027 // conditional paths which would obscure its flow. In fact, an early 1028 // version of this code did use a unified method which was harder to 1029 // follow and, as a result, it had subtle bugs that were hard to 1030 // track down. So keeping these two methods separate allows each to 1031 // be more readable. It will be good to keep these two in sync as 1032 // much as possible. 1033 1034 assert_heap_not_locked_and_not_at_safepoint(); 1035 assert(isHumongous(word_size), "attempt_allocation_humongous() " 1036 "should only be called for humongous allocations"); 1037 1038 // Humongous objects can exhaust the heap quickly, so we should check if we 1039 // need to start a marking cycle at each humongous object allocation. We do 1040 // the check before we do the actual allocation. The reason for doing it 1041 // before the allocation is that we avoid having to keep track of the newly 1042 // allocated memory while we do a GC. 1043 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1044 word_size)) { 1045 collect(GCCause::_g1_humongous_allocation); 1046 } 1047 1048 // We will loop until a) we manage to successfully perform the 1049 // allocation or b) we successfully schedule a collection which 1050 // fails to perform the allocation. b) is the only case when we'll 1051 // return NULL. 1052 HeapWord* result = NULL; 1053 for (int try_count = 1; /* we'll return */; try_count += 1) { 1054 bool should_try_gc; 1055 unsigned int gc_count_before; 1056 1057 { 1058 MutexLockerEx x(Heap_lock); 1059 1060 // Given that humongous objects are not allocated in young 1061 // regions, we'll first try to do the allocation without doing a 1062 // collection hoping that there's enough space in the heap. 1063 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1064 if (result != NULL) { 1065 return result; 1066 } 1067 1068 if (GC_locker::is_active_and_needs_gc()) { 1069 should_try_gc = false; 1070 } else { 1071 // The GCLocker may not be active but the GCLocker initiated 1072 // GC may not yet have been performed (GCLocker::needs_gc() 1073 // returns true). In this case we do not try this GC and 1074 // wait until the GCLocker initiated GC is performed, and 1075 // then retry the allocation. 1076 if (GC_locker::needs_gc()) { 1077 should_try_gc = false; 1078 } else { 1079 // Read the GC count while still holding the Heap_lock. 1080 gc_count_before = total_collections(); 1081 should_try_gc = true; 1082 } 1083 } 1084 } 1085 1086 if (should_try_gc) { 1087 // If we failed to allocate the humongous object, we should try to 1088 // do a collection pause (if we're allowed) in case it reclaims 1089 // enough space for the allocation to succeed after the pause. 1090 1091 bool succeeded; 1092 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1093 GCCause::_g1_humongous_allocation); 1094 if (result != NULL) { 1095 assert(succeeded, "only way to get back a non-NULL result"); 1096 return result; 1097 } 1098 1099 if (succeeded) { 1100 // If we get here we successfully scheduled a collection which 1101 // failed to allocate. No point in trying to allocate 1102 // further. We'll just return NULL. 1103 MutexLockerEx x(Heap_lock); 1104 *gc_count_before_ret = total_collections(); 1105 return NULL; 1106 } 1107 } else { 1108 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1109 MutexLockerEx x(Heap_lock); 1110 *gc_count_before_ret = total_collections(); 1111 return NULL; 1112 } 1113 // The GCLocker is either active or the GCLocker initiated 1114 // GC has not yet been performed. Stall until it is and 1115 // then retry the allocation. 1116 GC_locker::stall_until_clear(); 1117 (*gclocker_retry_count_ret) += 1; 1118 } 1119 1120 // We can reach here if we were unsuccessful in scheduling a 1121 // collection (because another thread beat us to it) or if we were 1122 // stalled due to the GC locker. In either can we should retry the 1123 // allocation attempt in case another thread successfully 1124 // performed a collection and reclaimed enough space. Give a 1125 // warning if we seem to be looping forever. 1126 1127 if ((QueuedAllocationWarningCount > 0) && 1128 (try_count % QueuedAllocationWarningCount == 0)) { 1129 warning("G1CollectedHeap::attempt_allocation_humongous() " 1130 "retries %d times", try_count); 1131 } 1132 } 1133 1134 ShouldNotReachHere(); 1135 return NULL; 1136 } 1137 1138 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1139 AllocationContext_t context, 1140 bool expect_null_mutator_alloc_region) { 1141 assert_at_safepoint(true /* should_be_vm_thread */); 1142 assert(_allocator->mutator_alloc_region(context)->get() == NULL || 1143 !expect_null_mutator_alloc_region, 1144 "the current alloc region was unexpectedly found to be non-NULL"); 1145 1146 if (!isHumongous(word_size)) { 1147 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 1148 false /* bot_updates */); 1149 } else { 1150 HeapWord* result = humongous_obj_allocate(word_size, context); 1151 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1152 g1_policy()->set_initiate_conc_mark_if_possible(); 1153 } 1154 return result; 1155 } 1156 1157 ShouldNotReachHere(); 1158 } 1159 1160 class PostMCRemSetClearClosure: public HeapRegionClosure { 1161 G1CollectedHeap* _g1h; 1162 ModRefBarrierSet* _mr_bs; 1163 public: 1164 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1165 _g1h(g1h), _mr_bs(mr_bs) {} 1166 1167 bool doHeapRegion(HeapRegion* r) { 1168 HeapRegionRemSet* hrrs = r->rem_set(); 1169 1170 if (r->continuesHumongous()) { 1171 // We'll assert that the strong code root list and RSet is empty 1172 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1173 assert(hrrs->occupied() == 0, "RSet should be empty"); 1174 return false; 1175 } 1176 1177 _g1h->reset_gc_time_stamps(r); 1178 hrrs->clear(); 1179 // You might think here that we could clear just the cards 1180 // corresponding to the used region. But no: if we leave a dirty card 1181 // in a region we might allocate into, then it would prevent that card 1182 // from being enqueued, and cause it to be missed. 1183 // Re: the performance cost: we shouldn't be doing full GC anyway! 1184 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1185 1186 return false; 1187 } 1188 }; 1189 1190 void G1CollectedHeap::clear_rsets_post_compaction() { 1191 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1192 heap_region_iterate(&rs_clear); 1193 } 1194 1195 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1196 G1CollectedHeap* _g1h; 1197 UpdateRSOopClosure _cl; 1198 int _worker_i; 1199 public: 1200 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1201 _cl(g1->g1_rem_set(), worker_i), 1202 _worker_i(worker_i), 1203 _g1h(g1) 1204 { } 1205 1206 bool doHeapRegion(HeapRegion* r) { 1207 if (!r->continuesHumongous()) { 1208 _cl.set_from(r); 1209 r->oop_iterate(&_cl); 1210 } 1211 return false; 1212 } 1213 }; 1214 1215 class ParRebuildRSTask: public AbstractGangTask { 1216 G1CollectedHeap* _g1; 1217 public: 1218 ParRebuildRSTask(G1CollectedHeap* g1) 1219 : AbstractGangTask("ParRebuildRSTask"), 1220 _g1(g1) 1221 { } 1222 1223 void work(uint worker_id) { 1224 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1225 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id, 1226 _g1->workers()->active_workers(), 1227 HeapRegion::RebuildRSClaimValue); 1228 } 1229 }; 1230 1231 class PostCompactionPrinterClosure: public HeapRegionClosure { 1232 private: 1233 G1HRPrinter* _hr_printer; 1234 public: 1235 bool doHeapRegion(HeapRegion* hr) { 1236 assert(!hr->is_young(), "not expecting to find young regions"); 1237 if (hr->is_free()) { 1238 // We only generate output for non-empty regions. 1239 } else if (hr->startsHumongous()) { 1240 if (hr->region_num() == 1) { 1241 // single humongous region 1242 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1243 } else { 1244 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1245 } 1246 } else if (hr->continuesHumongous()) { 1247 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1248 } else if (hr->is_old()) { 1249 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1250 } else { 1251 ShouldNotReachHere(); 1252 } 1253 return false; 1254 } 1255 1256 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1257 : _hr_printer(hr_printer) { } 1258 }; 1259 1260 void G1CollectedHeap::print_hrm_post_compaction() { 1261 PostCompactionPrinterClosure cl(hr_printer()); 1262 heap_region_iterate(&cl); 1263 } 1264 1265 bool G1CollectedHeap::do_collection(bool explicit_gc, 1266 bool clear_all_soft_refs, 1267 size_t word_size) { 1268 assert_at_safepoint(true /* should_be_vm_thread */); 1269 1270 if (GC_locker::check_active_before_gc()) { 1271 return false; 1272 } 1273 1274 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1275 gc_timer->register_gc_start(); 1276 1277 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1278 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1279 1280 SvcGCMarker sgcm(SvcGCMarker::FULL); 1281 ResourceMark rm; 1282 1283 print_heap_before_gc(); 1284 trace_heap_before_gc(gc_tracer); 1285 1286 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1287 1288 verify_region_sets_optional(); 1289 1290 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1291 collector_policy()->should_clear_all_soft_refs(); 1292 1293 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1294 1295 { 1296 IsGCActiveMark x; 1297 1298 // Timing 1299 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1300 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1301 1302 { 1303 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id()); 1304 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1305 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1306 1307 double start = os::elapsedTime(); 1308 g1_policy()->record_full_collection_start(); 1309 1310 // Note: When we have a more flexible GC logging framework that 1311 // allows us to add optional attributes to a GC log record we 1312 // could consider timing and reporting how long we wait in the 1313 // following two methods. 1314 wait_while_free_regions_coming(); 1315 // If we start the compaction before the CM threads finish 1316 // scanning the root regions we might trip them over as we'll 1317 // be moving objects / updating references. So let's wait until 1318 // they are done. By telling them to abort, they should complete 1319 // early. 1320 _cm->root_regions()->abort(); 1321 _cm->root_regions()->wait_until_scan_finished(); 1322 append_secondary_free_list_if_not_empty_with_lock(); 1323 1324 gc_prologue(true); 1325 increment_total_collections(true /* full gc */); 1326 increment_old_marking_cycles_started(); 1327 1328 assert(used() == recalculate_used(), "Should be equal"); 1329 1330 verify_before_gc(); 1331 1332 check_bitmaps("Full GC Start"); 1333 pre_full_gc_dump(gc_timer); 1334 1335 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1336 1337 // Disable discovery and empty the discovered lists 1338 // for the CM ref processor. 1339 ref_processor_cm()->disable_discovery(); 1340 ref_processor_cm()->abandon_partial_discovery(); 1341 ref_processor_cm()->verify_no_references_recorded(); 1342 1343 // Abandon current iterations of concurrent marking and concurrent 1344 // refinement, if any are in progress. We have to do this before 1345 // wait_until_scan_finished() below. 1346 concurrent_mark()->abort(); 1347 1348 // Make sure we'll choose a new allocation region afterwards. 1349 _allocator->release_mutator_alloc_region(); 1350 _allocator->abandon_gc_alloc_regions(); 1351 g1_rem_set()->cleanupHRRS(); 1352 1353 // We should call this after we retire any currently active alloc 1354 // regions so that all the ALLOC / RETIRE events are generated 1355 // before the start GC event. 1356 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1357 1358 // We may have added regions to the current incremental collection 1359 // set between the last GC or pause and now. We need to clear the 1360 // incremental collection set and then start rebuilding it afresh 1361 // after this full GC. 1362 abandon_collection_set(g1_policy()->inc_cset_head()); 1363 g1_policy()->clear_incremental_cset(); 1364 g1_policy()->stop_incremental_cset_building(); 1365 1366 tear_down_region_sets(false /* free_list_only */); 1367 g1_policy()->set_gcs_are_young(true); 1368 1369 // See the comments in g1CollectedHeap.hpp and 1370 // G1CollectedHeap::ref_processing_init() about 1371 // how reference processing currently works in G1. 1372 1373 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1374 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1375 1376 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1377 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1378 1379 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1380 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1381 1382 // Do collection work 1383 { 1384 HandleMark hm; // Discard invalid handles created during gc 1385 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1386 } 1387 1388 assert(num_free_regions() == 0, "we should not have added any free regions"); 1389 rebuild_region_sets(false /* free_list_only */); 1390 1391 // Enqueue any discovered reference objects that have 1392 // not been removed from the discovered lists. 1393 ref_processor_stw()->enqueue_discovered_references(); 1394 1395 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1396 1397 MemoryService::track_memory_usage(); 1398 1399 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1400 ref_processor_stw()->verify_no_references_recorded(); 1401 1402 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1403 ClassLoaderDataGraph::purge(); 1404 MetaspaceAux::verify_metrics(); 1405 1406 // Note: since we've just done a full GC, concurrent 1407 // marking is no longer active. Therefore we need not 1408 // re-enable reference discovery for the CM ref processor. 1409 // That will be done at the start of the next marking cycle. 1410 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1411 ref_processor_cm()->verify_no_references_recorded(); 1412 1413 reset_gc_time_stamp(); 1414 // Since everything potentially moved, we will clear all remembered 1415 // sets, and clear all cards. Later we will rebuild remembered 1416 // sets. We will also reset the GC time stamps of the regions. 1417 clear_rsets_post_compaction(); 1418 check_gc_time_stamps(); 1419 1420 // Resize the heap if necessary. 1421 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1422 1423 if (_hr_printer.is_active()) { 1424 // We should do this after we potentially resize the heap so 1425 // that all the COMMIT / UNCOMMIT events are generated before 1426 // the end GC event. 1427 1428 print_hrm_post_compaction(); 1429 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1430 } 1431 1432 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1433 if (hot_card_cache->use_cache()) { 1434 hot_card_cache->reset_card_counts(); 1435 hot_card_cache->reset_hot_cache(); 1436 } 1437 1438 // Rebuild remembered sets of all regions. 1439 if (G1CollectedHeap::use_parallel_gc_threads()) { 1440 uint n_workers = 1441 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1442 workers()->active_workers(), 1443 Threads::number_of_non_daemon_threads()); 1444 assert(UseDynamicNumberOfGCThreads || 1445 n_workers == workers()->total_workers(), 1446 "If not dynamic should be using all the workers"); 1447 workers()->set_active_workers(n_workers); 1448 // Set parallel threads in the heap (_n_par_threads) only 1449 // before a parallel phase and always reset it to 0 after 1450 // the phase so that the number of parallel threads does 1451 // no get carried forward to a serial phase where there 1452 // may be code that is "possibly_parallel". 1453 set_par_threads(n_workers); 1454 1455 ParRebuildRSTask rebuild_rs_task(this); 1456 assert(check_heap_region_claim_values( 1457 HeapRegion::InitialClaimValue), "sanity check"); 1458 assert(UseDynamicNumberOfGCThreads || 1459 workers()->active_workers() == workers()->total_workers(), 1460 "Unless dynamic should use total workers"); 1461 // Use the most recent number of active workers 1462 assert(workers()->active_workers() > 0, 1463 "Active workers not properly set"); 1464 set_par_threads(workers()->active_workers()); 1465 workers()->run_task(&rebuild_rs_task); 1466 set_par_threads(0); 1467 assert(check_heap_region_claim_values( 1468 HeapRegion::RebuildRSClaimValue), "sanity check"); 1469 reset_heap_region_claim_values(); 1470 } else { 1471 RebuildRSOutOfRegionClosure rebuild_rs(this); 1472 heap_region_iterate(&rebuild_rs); 1473 } 1474 1475 // Rebuild the strong code root lists for each region 1476 rebuild_strong_code_roots(); 1477 1478 if (true) { // FIXME 1479 MetaspaceGC::compute_new_size(); 1480 } 1481 1482 #ifdef TRACESPINNING 1483 ParallelTaskTerminator::print_termination_counts(); 1484 #endif 1485 1486 // Discard all rset updates 1487 JavaThread::dirty_card_queue_set().abandon_logs(); 1488 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1489 1490 _young_list->reset_sampled_info(); 1491 // At this point there should be no regions in the 1492 // entire heap tagged as young. 1493 assert(check_young_list_empty(true /* check_heap */), 1494 "young list should be empty at this point"); 1495 1496 // Update the number of full collections that have been completed. 1497 increment_old_marking_cycles_completed(false /* concurrent */); 1498 1499 _hrm.verify_optional(); 1500 verify_region_sets_optional(); 1501 1502 verify_after_gc(); 1503 1504 // Clear the previous marking bitmap, if needed for bitmap verification. 1505 // Note we cannot do this when we clear the next marking bitmap in 1506 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1507 // objects marked during a full GC against the previous bitmap. 1508 // But we need to clear it before calling check_bitmaps below since 1509 // the full GC has compacted objects and updated TAMS but not updated 1510 // the prev bitmap. 1511 if (G1VerifyBitmaps) { 1512 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1513 } 1514 check_bitmaps("Full GC End"); 1515 1516 // Start a new incremental collection set for the next pause 1517 assert(g1_policy()->collection_set() == NULL, "must be"); 1518 g1_policy()->start_incremental_cset_building(); 1519 1520 clear_cset_fast_test(); 1521 1522 _allocator->init_mutator_alloc_region(); 1523 1524 double end = os::elapsedTime(); 1525 g1_policy()->record_full_collection_end(); 1526 1527 if (G1Log::fine()) { 1528 g1_policy()->print_heap_transition(); 1529 } 1530 1531 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1532 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1533 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1534 // before any GC notifications are raised. 1535 g1mm()->update_sizes(); 1536 1537 gc_epilogue(true); 1538 } 1539 1540 if (G1Log::finer()) { 1541 g1_policy()->print_detailed_heap_transition(true /* full */); 1542 } 1543 1544 print_heap_after_gc(); 1545 trace_heap_after_gc(gc_tracer); 1546 1547 post_full_gc_dump(gc_timer); 1548 1549 gc_timer->register_gc_end(); 1550 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1551 } 1552 1553 return true; 1554 } 1555 1556 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1557 // do_collection() will return whether it succeeded in performing 1558 // the GC. Currently, there is no facility on the 1559 // do_full_collection() API to notify the caller than the collection 1560 // did not succeed (e.g., because it was locked out by the GC 1561 // locker). So, right now, we'll ignore the return value. 1562 bool dummy = do_collection(true, /* explicit_gc */ 1563 clear_all_soft_refs, 1564 0 /* word_size */); 1565 } 1566 1567 // This code is mostly copied from TenuredGeneration. 1568 void 1569 G1CollectedHeap:: 1570 resize_if_necessary_after_full_collection(size_t word_size) { 1571 // Include the current allocation, if any, and bytes that will be 1572 // pre-allocated to support collections, as "used". 1573 const size_t used_after_gc = used(); 1574 const size_t capacity_after_gc = capacity(); 1575 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1576 1577 // This is enforced in arguments.cpp. 1578 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1579 "otherwise the code below doesn't make sense"); 1580 1581 // We don't have floating point command-line arguments 1582 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1583 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1584 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1585 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1586 1587 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1588 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1589 1590 // We have to be careful here as these two calculations can overflow 1591 // 32-bit size_t's. 1592 double used_after_gc_d = (double) used_after_gc; 1593 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1594 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1595 1596 // Let's make sure that they are both under the max heap size, which 1597 // by default will make them fit into a size_t. 1598 double desired_capacity_upper_bound = (double) max_heap_size; 1599 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1600 desired_capacity_upper_bound); 1601 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1602 desired_capacity_upper_bound); 1603 1604 // We can now safely turn them into size_t's. 1605 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1606 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1607 1608 // This assert only makes sense here, before we adjust them 1609 // with respect to the min and max heap size. 1610 assert(minimum_desired_capacity <= maximum_desired_capacity, 1611 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1612 "maximum_desired_capacity = "SIZE_FORMAT, 1613 minimum_desired_capacity, maximum_desired_capacity)); 1614 1615 // Should not be greater than the heap max size. No need to adjust 1616 // it with respect to the heap min size as it's a lower bound (i.e., 1617 // we'll try to make the capacity larger than it, not smaller). 1618 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1619 // Should not be less than the heap min size. No need to adjust it 1620 // with respect to the heap max size as it's an upper bound (i.e., 1621 // we'll try to make the capacity smaller than it, not greater). 1622 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1623 1624 if (capacity_after_gc < minimum_desired_capacity) { 1625 // Don't expand unless it's significant 1626 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1627 ergo_verbose4(ErgoHeapSizing, 1628 "attempt heap expansion", 1629 ergo_format_reason("capacity lower than " 1630 "min desired capacity after Full GC") 1631 ergo_format_byte("capacity") 1632 ergo_format_byte("occupancy") 1633 ergo_format_byte_perc("min desired capacity"), 1634 capacity_after_gc, used_after_gc, 1635 minimum_desired_capacity, (double) MinHeapFreeRatio); 1636 expand(expand_bytes); 1637 1638 // No expansion, now see if we want to shrink 1639 } else if (capacity_after_gc > maximum_desired_capacity) { 1640 // Capacity too large, compute shrinking size 1641 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1642 ergo_verbose4(ErgoHeapSizing, 1643 "attempt heap shrinking", 1644 ergo_format_reason("capacity higher than " 1645 "max desired capacity after Full GC") 1646 ergo_format_byte("capacity") 1647 ergo_format_byte("occupancy") 1648 ergo_format_byte_perc("max desired capacity"), 1649 capacity_after_gc, used_after_gc, 1650 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1651 shrink(shrink_bytes); 1652 } 1653 } 1654 1655 1656 HeapWord* 1657 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1658 AllocationContext_t context, 1659 bool* succeeded) { 1660 assert_at_safepoint(true /* should_be_vm_thread */); 1661 1662 *succeeded = true; 1663 // Let's attempt the allocation first. 1664 HeapWord* result = 1665 attempt_allocation_at_safepoint(word_size, 1666 context, 1667 false /* expect_null_mutator_alloc_region */); 1668 if (result != NULL) { 1669 assert(*succeeded, "sanity"); 1670 return result; 1671 } 1672 1673 // In a G1 heap, we're supposed to keep allocation from failing by 1674 // incremental pauses. Therefore, at least for now, we'll favor 1675 // expansion over collection. (This might change in the future if we can 1676 // do something smarter than full collection to satisfy a failed alloc.) 1677 result = expand_and_allocate(word_size, context); 1678 if (result != NULL) { 1679 assert(*succeeded, "sanity"); 1680 return result; 1681 } 1682 1683 // Expansion didn't work, we'll try to do a Full GC. 1684 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1685 false, /* clear_all_soft_refs */ 1686 word_size); 1687 if (!gc_succeeded) { 1688 *succeeded = false; 1689 return NULL; 1690 } 1691 1692 // Retry the allocation 1693 result = attempt_allocation_at_safepoint(word_size, 1694 context, 1695 true /* expect_null_mutator_alloc_region */); 1696 if (result != NULL) { 1697 assert(*succeeded, "sanity"); 1698 return result; 1699 } 1700 1701 // Then, try a Full GC that will collect all soft references. 1702 gc_succeeded = do_collection(false, /* explicit_gc */ 1703 true, /* clear_all_soft_refs */ 1704 word_size); 1705 if (!gc_succeeded) { 1706 *succeeded = false; 1707 return NULL; 1708 } 1709 1710 // Retry the allocation once more 1711 result = attempt_allocation_at_safepoint(word_size, 1712 context, 1713 true /* expect_null_mutator_alloc_region */); 1714 if (result != NULL) { 1715 assert(*succeeded, "sanity"); 1716 return result; 1717 } 1718 1719 assert(!collector_policy()->should_clear_all_soft_refs(), 1720 "Flag should have been handled and cleared prior to this point"); 1721 1722 // What else? We might try synchronous finalization later. If the total 1723 // space available is large enough for the allocation, then a more 1724 // complete compaction phase than we've tried so far might be 1725 // appropriate. 1726 assert(*succeeded, "sanity"); 1727 return NULL; 1728 } 1729 1730 // Attempting to expand the heap sufficiently 1731 // to support an allocation of the given "word_size". If 1732 // successful, perform the allocation and return the address of the 1733 // allocated block, or else "NULL". 1734 1735 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1736 assert_at_safepoint(true /* should_be_vm_thread */); 1737 1738 verify_region_sets_optional(); 1739 1740 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1741 ergo_verbose1(ErgoHeapSizing, 1742 "attempt heap expansion", 1743 ergo_format_reason("allocation request failed") 1744 ergo_format_byte("allocation request"), 1745 word_size * HeapWordSize); 1746 if (expand(expand_bytes)) { 1747 _hrm.verify_optional(); 1748 verify_region_sets_optional(); 1749 return attempt_allocation_at_safepoint(word_size, 1750 context, 1751 false /* expect_null_mutator_alloc_region */); 1752 } 1753 return NULL; 1754 } 1755 1756 bool G1CollectedHeap::expand(size_t expand_bytes) { 1757 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1758 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1759 HeapRegion::GrainBytes); 1760 ergo_verbose2(ErgoHeapSizing, 1761 "expand the heap", 1762 ergo_format_byte("requested expansion amount") 1763 ergo_format_byte("attempted expansion amount"), 1764 expand_bytes, aligned_expand_bytes); 1765 1766 if (is_maximal_no_gc()) { 1767 ergo_verbose0(ErgoHeapSizing, 1768 "did not expand the heap", 1769 ergo_format_reason("heap already fully expanded")); 1770 return false; 1771 } 1772 1773 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1774 assert(regions_to_expand > 0, "Must expand by at least one region"); 1775 1776 uint expanded_by = _hrm.expand_by(regions_to_expand); 1777 1778 if (expanded_by > 0) { 1779 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1780 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1781 g1_policy()->record_new_heap_size(num_regions()); 1782 } else { 1783 ergo_verbose0(ErgoHeapSizing, 1784 "did not expand the heap", 1785 ergo_format_reason("heap expansion operation failed")); 1786 // The expansion of the virtual storage space was unsuccessful. 1787 // Let's see if it was because we ran out of swap. 1788 if (G1ExitOnExpansionFailure && 1789 _hrm.available() >= regions_to_expand) { 1790 // We had head room... 1791 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1792 } 1793 } 1794 return regions_to_expand > 0; 1795 } 1796 1797 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1798 size_t aligned_shrink_bytes = 1799 ReservedSpace::page_align_size_down(shrink_bytes); 1800 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1801 HeapRegion::GrainBytes); 1802 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1803 1804 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1805 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1806 1807 ergo_verbose3(ErgoHeapSizing, 1808 "shrink the heap", 1809 ergo_format_byte("requested shrinking amount") 1810 ergo_format_byte("aligned shrinking amount") 1811 ergo_format_byte("attempted shrinking amount"), 1812 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1813 if (num_regions_removed > 0) { 1814 g1_policy()->record_new_heap_size(num_regions()); 1815 } else { 1816 ergo_verbose0(ErgoHeapSizing, 1817 "did not shrink the heap", 1818 ergo_format_reason("heap shrinking operation failed")); 1819 } 1820 } 1821 1822 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1823 verify_region_sets_optional(); 1824 1825 // We should only reach here at the end of a Full GC which means we 1826 // should not not be holding to any GC alloc regions. The method 1827 // below will make sure of that and do any remaining clean up. 1828 _allocator->abandon_gc_alloc_regions(); 1829 1830 // Instead of tearing down / rebuilding the free lists here, we 1831 // could instead use the remove_all_pending() method on free_list to 1832 // remove only the ones that we need to remove. 1833 tear_down_region_sets(true /* free_list_only */); 1834 shrink_helper(shrink_bytes); 1835 rebuild_region_sets(true /* free_list_only */); 1836 1837 _hrm.verify_optional(); 1838 verify_region_sets_optional(); 1839 } 1840 1841 // Public methods. 1842 1843 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1844 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1845 #endif // _MSC_VER 1846 1847 1848 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1849 SharedHeap(policy_), 1850 _g1_policy(policy_), 1851 _dirty_card_queue_set(false), 1852 _into_cset_dirty_card_queue_set(false), 1853 _is_alive_closure_cm(this), 1854 _is_alive_closure_stw(this), 1855 _ref_processor_cm(NULL), 1856 _ref_processor_stw(NULL), 1857 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1858 _bot_shared(NULL), 1859 _evac_failure_scan_stack(NULL), 1860 _mark_in_progress(false), 1861 _cg1r(NULL), 1862 _g1mm(NULL), 1863 _refine_cte_cl(NULL), 1864 _full_collection(false), 1865 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1866 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1867 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1868 _humongous_is_live(), 1869 _has_humongous_reclaim_candidates(false), 1870 _free_regions_coming(false), 1871 _young_list(new YoungList(this)), 1872 _gc_time_stamp(0), 1873 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1874 _old_plab_stats(OldPLABSize, PLABWeight), 1875 _expand_heap_after_alloc_failure(true), 1876 _surviving_young_words(NULL), 1877 _old_marking_cycles_started(0), 1878 _old_marking_cycles_completed(0), 1879 _concurrent_cycle_started(false), 1880 _in_cset_fast_test(), 1881 _dirty_cards_region_list(NULL), 1882 _worker_cset_start_region(NULL), 1883 _worker_cset_start_region_time_stamp(NULL), 1884 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1885 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1886 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1887 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1888 1889 _g1h = this; 1890 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1891 vm_exit_during_initialization("Failed necessary allocation."); 1892 } 1893 1894 _allocator = G1Allocator::create_allocator(_g1h); 1895 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1896 1897 int n_queues = MAX2((int)ParallelGCThreads, 1); 1898 _task_queues = new RefToScanQueueSet(n_queues); 1899 1900 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1901 assert(n_rem_sets > 0, "Invariant."); 1902 1903 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1904 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1905 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1906 1907 for (int i = 0; i < n_queues; i++) { 1908 RefToScanQueue* q = new RefToScanQueue(); 1909 q->initialize(); 1910 _task_queues->register_queue(i, q); 1911 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1912 } 1913 clear_cset_start_regions(); 1914 1915 // Initialize the G1EvacuationFailureALot counters and flags. 1916 NOT_PRODUCT(reset_evacuation_should_fail();) 1917 1918 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1919 } 1920 1921 jint G1CollectedHeap::initialize() { 1922 CollectedHeap::pre_initialize(); 1923 os::enable_vtime(); 1924 1925 G1Log::init(); 1926 1927 // Necessary to satisfy locking discipline assertions. 1928 1929 MutexLocker x(Heap_lock); 1930 1931 // We have to initialize the printer before committing the heap, as 1932 // it will be used then. 1933 _hr_printer.set_active(G1PrintHeapRegions); 1934 1935 // While there are no constraints in the GC code that HeapWordSize 1936 // be any particular value, there are multiple other areas in the 1937 // system which believe this to be true (e.g. oop->object_size in some 1938 // cases incorrectly returns the size in wordSize units rather than 1939 // HeapWordSize). 1940 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1941 1942 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1943 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1944 size_t heap_alignment = collector_policy()->heap_alignment(); 1945 1946 // Ensure that the sizes are properly aligned. 1947 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1948 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1949 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1950 1951 _refine_cte_cl = new RefineCardTableEntryClosure(); 1952 1953 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl); 1954 1955 // Reserve the maximum. 1956 1957 // When compressed oops are enabled, the preferred heap base 1958 // is calculated by subtracting the requested size from the 1959 // 32Gb boundary and using the result as the base address for 1960 // heap reservation. If the requested size is not aligned to 1961 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1962 // into the ReservedHeapSpace constructor) then the actual 1963 // base of the reserved heap may end up differing from the 1964 // address that was requested (i.e. the preferred heap base). 1965 // If this happens then we could end up using a non-optimal 1966 // compressed oops mode. 1967 1968 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1969 heap_alignment); 1970 1971 // It is important to do this in a way such that concurrent readers can't 1972 // temporarily think something is in the heap. (I've actually seen this 1973 // happen in asserts: DLD.) 1974 _reserved.set_word_size(0); 1975 _reserved.set_start((HeapWord*)heap_rs.base()); 1976 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 1977 1978 // Create the gen rem set (and barrier set) for the entire reserved region. 1979 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 1980 set_barrier_set(rem_set()->bs()); 1981 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) { 1982 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS"); 1983 return JNI_ENOMEM; 1984 } 1985 1986 // Also create a G1 rem set. 1987 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1988 1989 // Carve out the G1 part of the heap. 1990 1991 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1992 G1RegionToSpaceMapper* heap_storage = 1993 G1RegionToSpaceMapper::create_mapper(g1_rs, 1994 UseLargePages ? os::large_page_size() : os::vm_page_size(), 1995 HeapRegion::GrainBytes, 1996 1, 1997 mtJavaHeap); 1998 heap_storage->set_mapping_changed_listener(&_listener); 1999 2000 // Reserve space for the block offset table. We do not support automatic uncommit 2001 // for the card table at this time. BOT only. 2002 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize)); 2003 G1RegionToSpaceMapper* bot_storage = 2004 G1RegionToSpaceMapper::create_mapper(bot_rs, 2005 os::vm_page_size(), 2006 HeapRegion::GrainBytes, 2007 G1BlockOffsetSharedArray::N_bytes, 2008 mtGC); 2009 2010 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 2011 G1RegionToSpaceMapper* cardtable_storage = 2012 G1RegionToSpaceMapper::create_mapper(cardtable_rs, 2013 os::vm_page_size(), 2014 HeapRegion::GrainBytes, 2015 G1BlockOffsetSharedArray::N_bytes, 2016 mtGC); 2017 2018 // Reserve space for the card counts table. 2019 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize)); 2020 G1RegionToSpaceMapper* card_counts_storage = 2021 G1RegionToSpaceMapper::create_mapper(card_counts_rs, 2022 os::vm_page_size(), 2023 HeapRegion::GrainBytes, 2024 G1BlockOffsetSharedArray::N_bytes, 2025 mtGC); 2026 2027 // Reserve space for prev and next bitmap. 2028 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 2029 2030 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size)); 2031 G1RegionToSpaceMapper* prev_bitmap_storage = 2032 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs, 2033 os::vm_page_size(), 2034 HeapRegion::GrainBytes, 2035 CMBitMap::mark_distance(), 2036 mtGC); 2037 2038 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size)); 2039 G1RegionToSpaceMapper* next_bitmap_storage = 2040 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs, 2041 os::vm_page_size(), 2042 HeapRegion::GrainBytes, 2043 CMBitMap::mark_distance(), 2044 mtGC); 2045 2046 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 2047 g1_barrier_set()->initialize(cardtable_storage); 2048 // Do later initialization work for concurrent refinement. 2049 _cg1r->init(card_counts_storage); 2050 2051 // 6843694 - ensure that the maximum region index can fit 2052 // in the remembered set structures. 2053 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2054 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2055 2056 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2057 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2058 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2059 "too many cards per region"); 2060 2061 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 2062 2063 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage); 2064 2065 _g1h = this; 2066 2067 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes); 2068 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes); 2069 2070 // Create the ConcurrentMark data structure and thread. 2071 // (Must do this late, so that "max_regions" is defined.) 2072 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 2073 if (_cm == NULL || !_cm->completed_initialization()) { 2074 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2075 return JNI_ENOMEM; 2076 } 2077 _cmThread = _cm->cmThread(); 2078 2079 // Initialize the from_card cache structure of HeapRegionRemSet. 2080 HeapRegionRemSet::init_heap(max_regions()); 2081 2082 // Now expand into the initial heap size. 2083 if (!expand(init_byte_size)) { 2084 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2085 return JNI_ENOMEM; 2086 } 2087 2088 // Perform any initialization actions delegated to the policy. 2089 g1_policy()->init(); 2090 2091 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2092 SATB_Q_FL_lock, 2093 G1SATBProcessCompletedThreshold, 2094 Shared_SATB_Q_lock); 2095 2096 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2097 DirtyCardQ_CBL_mon, 2098 DirtyCardQ_FL_lock, 2099 concurrent_g1_refine()->yellow_zone(), 2100 concurrent_g1_refine()->red_zone(), 2101 Shared_DirtyCardQ_lock); 2102 2103 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2104 DirtyCardQ_CBL_mon, 2105 DirtyCardQ_FL_lock, 2106 -1, // never trigger processing 2107 -1, // no limit on length 2108 Shared_DirtyCardQ_lock, 2109 &JavaThread::dirty_card_queue_set()); 2110 2111 // Initialize the card queue set used to hold cards containing 2112 // references into the collection set. 2113 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code 2114 DirtyCardQ_CBL_mon, 2115 DirtyCardQ_FL_lock, 2116 -1, // never trigger processing 2117 -1, // no limit on length 2118 Shared_DirtyCardQ_lock, 2119 &JavaThread::dirty_card_queue_set()); 2120 2121 // In case we're keeping closure specialization stats, initialize those 2122 // counts and that mechanism. 2123 SpecializationStats::clear(); 2124 2125 // Here we allocate the dummy HeapRegion that is required by the 2126 // G1AllocRegion class. 2127 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2128 2129 // We'll re-use the same region whether the alloc region will 2130 // require BOT updates or not and, if it doesn't, then a non-young 2131 // region will complain that it cannot support allocations without 2132 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2133 dummy_region->set_eden(); 2134 // Make sure it's full. 2135 dummy_region->set_top(dummy_region->end()); 2136 G1AllocRegion::setup(this, dummy_region); 2137 2138 _allocator->init_mutator_alloc_region(); 2139 2140 // Do create of the monitoring and management support so that 2141 // values in the heap have been properly initialized. 2142 _g1mm = new G1MonitoringSupport(this); 2143 2144 G1StringDedup::initialize(); 2145 2146 return JNI_OK; 2147 } 2148 2149 void G1CollectedHeap::stop() { 2150 // Stop all concurrent threads. We do this to make sure these threads 2151 // do not continue to execute and access resources (e.g. gclog_or_tty) 2152 // that are destroyed during shutdown. 2153 _cg1r->stop(); 2154 _cmThread->stop(); 2155 if (G1StringDedup::is_enabled()) { 2156 G1StringDedup::stop(); 2157 } 2158 } 2159 2160 void G1CollectedHeap::clear_humongous_is_live_table() { 2161 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true"); 2162 _humongous_is_live.clear(); 2163 } 2164 2165 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2166 return HeapRegion::max_region_size(); 2167 } 2168 2169 void G1CollectedHeap::ref_processing_init() { 2170 // Reference processing in G1 currently works as follows: 2171 // 2172 // * There are two reference processor instances. One is 2173 // used to record and process discovered references 2174 // during concurrent marking; the other is used to 2175 // record and process references during STW pauses 2176 // (both full and incremental). 2177 // * Both ref processors need to 'span' the entire heap as 2178 // the regions in the collection set may be dotted around. 2179 // 2180 // * For the concurrent marking ref processor: 2181 // * Reference discovery is enabled at initial marking. 2182 // * Reference discovery is disabled and the discovered 2183 // references processed etc during remarking. 2184 // * Reference discovery is MT (see below). 2185 // * Reference discovery requires a barrier (see below). 2186 // * Reference processing may or may not be MT 2187 // (depending on the value of ParallelRefProcEnabled 2188 // and ParallelGCThreads). 2189 // * A full GC disables reference discovery by the CM 2190 // ref processor and abandons any entries on it's 2191 // discovered lists. 2192 // 2193 // * For the STW processor: 2194 // * Non MT discovery is enabled at the start of a full GC. 2195 // * Processing and enqueueing during a full GC is non-MT. 2196 // * During a full GC, references are processed after marking. 2197 // 2198 // * Discovery (may or may not be MT) is enabled at the start 2199 // of an incremental evacuation pause. 2200 // * References are processed near the end of a STW evacuation pause. 2201 // * For both types of GC: 2202 // * Discovery is atomic - i.e. not concurrent. 2203 // * Reference discovery will not need a barrier. 2204 2205 SharedHeap::ref_processing_init(); 2206 MemRegion mr = reserved_region(); 2207 2208 // Concurrent Mark ref processor 2209 _ref_processor_cm = 2210 new ReferenceProcessor(mr, // span 2211 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2212 // mt processing 2213 (int) ParallelGCThreads, 2214 // degree of mt processing 2215 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2216 // mt discovery 2217 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2218 // degree of mt discovery 2219 false, 2220 // Reference discovery is not atomic 2221 &_is_alive_closure_cm); 2222 // is alive closure 2223 // (for efficiency/performance) 2224 2225 // STW ref processor 2226 _ref_processor_stw = 2227 new ReferenceProcessor(mr, // span 2228 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2229 // mt processing 2230 MAX2((int)ParallelGCThreads, 1), 2231 // degree of mt processing 2232 (ParallelGCThreads > 1), 2233 // mt discovery 2234 MAX2((int)ParallelGCThreads, 1), 2235 // degree of mt discovery 2236 true, 2237 // Reference discovery is atomic 2238 &_is_alive_closure_stw); 2239 // is alive closure 2240 // (for efficiency/performance) 2241 } 2242 2243 size_t G1CollectedHeap::capacity() const { 2244 return _hrm.length() * HeapRegion::GrainBytes; 2245 } 2246 2247 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2248 assert(!hr->continuesHumongous(), "pre-condition"); 2249 hr->reset_gc_time_stamp(); 2250 if (hr->startsHumongous()) { 2251 uint first_index = hr->hrm_index() + 1; 2252 uint last_index = hr->last_hc_index(); 2253 for (uint i = first_index; i < last_index; i += 1) { 2254 HeapRegion* chr = region_at(i); 2255 assert(chr->continuesHumongous(), "sanity"); 2256 chr->reset_gc_time_stamp(); 2257 } 2258 } 2259 } 2260 2261 #ifndef PRODUCT 2262 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2263 private: 2264 unsigned _gc_time_stamp; 2265 bool _failures; 2266 2267 public: 2268 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2269 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2270 2271 virtual bool doHeapRegion(HeapRegion* hr) { 2272 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2273 if (_gc_time_stamp != region_gc_time_stamp) { 2274 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2275 "expected %d", HR_FORMAT_PARAMS(hr), 2276 region_gc_time_stamp, _gc_time_stamp); 2277 _failures = true; 2278 } 2279 return false; 2280 } 2281 2282 bool failures() { return _failures; } 2283 }; 2284 2285 void G1CollectedHeap::check_gc_time_stamps() { 2286 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2287 heap_region_iterate(&cl); 2288 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2289 } 2290 #endif // PRODUCT 2291 2292 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2293 DirtyCardQueue* into_cset_dcq, 2294 bool concurrent, 2295 uint worker_i) { 2296 // Clean cards in the hot card cache 2297 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2298 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2299 2300 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2301 int n_completed_buffers = 0; 2302 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2303 n_completed_buffers++; 2304 } 2305 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2306 dcqs.clear_n_completed_buffers(); 2307 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2308 } 2309 2310 2311 // Computes the sum of the storage used by the various regions. 2312 size_t G1CollectedHeap::used() const { 2313 return _allocator->used(); 2314 } 2315 2316 size_t G1CollectedHeap::used_unlocked() const { 2317 return _allocator->used_unlocked(); 2318 } 2319 2320 class SumUsedClosure: public HeapRegionClosure { 2321 size_t _used; 2322 public: 2323 SumUsedClosure() : _used(0) {} 2324 bool doHeapRegion(HeapRegion* r) { 2325 if (!r->continuesHumongous()) { 2326 _used += r->used(); 2327 } 2328 return false; 2329 } 2330 size_t result() { return _used; } 2331 }; 2332 2333 size_t G1CollectedHeap::recalculate_used() const { 2334 double recalculate_used_start = os::elapsedTime(); 2335 2336 SumUsedClosure blk; 2337 heap_region_iterate(&blk); 2338 2339 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2340 return blk.result(); 2341 } 2342 2343 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2344 switch (cause) { 2345 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2346 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2347 case GCCause::_g1_humongous_allocation: return true; 2348 case GCCause::_update_allocation_context_stats_inc: return true; 2349 default: return false; 2350 } 2351 } 2352 2353 #ifndef PRODUCT 2354 void G1CollectedHeap::allocate_dummy_regions() { 2355 // Let's fill up most of the region 2356 size_t word_size = HeapRegion::GrainWords - 1024; 2357 // And as a result the region we'll allocate will be humongous. 2358 guarantee(isHumongous(word_size), "sanity"); 2359 2360 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2361 // Let's use the existing mechanism for the allocation 2362 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2363 AllocationContext::system()); 2364 if (dummy_obj != NULL) { 2365 MemRegion mr(dummy_obj, word_size); 2366 CollectedHeap::fill_with_object(mr); 2367 } else { 2368 // If we can't allocate once, we probably cannot allocate 2369 // again. Let's get out of the loop. 2370 break; 2371 } 2372 } 2373 } 2374 #endif // !PRODUCT 2375 2376 void G1CollectedHeap::increment_old_marking_cycles_started() { 2377 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2378 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2379 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2380 _old_marking_cycles_started, _old_marking_cycles_completed)); 2381 2382 _old_marking_cycles_started++; 2383 } 2384 2385 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2386 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2387 2388 // We assume that if concurrent == true, then the caller is a 2389 // concurrent thread that was joined the Suspendible Thread 2390 // Set. If there's ever a cheap way to check this, we should add an 2391 // assert here. 2392 2393 // Given that this method is called at the end of a Full GC or of a 2394 // concurrent cycle, and those can be nested (i.e., a Full GC can 2395 // interrupt a concurrent cycle), the number of full collections 2396 // completed should be either one (in the case where there was no 2397 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2398 // behind the number of full collections started. 2399 2400 // This is the case for the inner caller, i.e. a Full GC. 2401 assert(concurrent || 2402 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2403 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2404 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2405 "is inconsistent with _old_marking_cycles_completed = %u", 2406 _old_marking_cycles_started, _old_marking_cycles_completed)); 2407 2408 // This is the case for the outer caller, i.e. the concurrent cycle. 2409 assert(!concurrent || 2410 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2411 err_msg("for outer caller (concurrent cycle): " 2412 "_old_marking_cycles_started = %u " 2413 "is inconsistent with _old_marking_cycles_completed = %u", 2414 _old_marking_cycles_started, _old_marking_cycles_completed)); 2415 2416 _old_marking_cycles_completed += 1; 2417 2418 // We need to clear the "in_progress" flag in the CM thread before 2419 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2420 // is set) so that if a waiter requests another System.gc() it doesn't 2421 // incorrectly see that a marking cycle is still in progress. 2422 if (concurrent) { 2423 _cmThread->clear_in_progress(); 2424 } 2425 2426 // This notify_all() will ensure that a thread that called 2427 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2428 // and it's waiting for a full GC to finish will be woken up. It is 2429 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2430 FullGCCount_lock->notify_all(); 2431 } 2432 2433 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2434 _concurrent_cycle_started = true; 2435 _gc_timer_cm->register_gc_start(start_time); 2436 2437 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2438 trace_heap_before_gc(_gc_tracer_cm); 2439 } 2440 2441 void G1CollectedHeap::register_concurrent_cycle_end() { 2442 if (_concurrent_cycle_started) { 2443 if (_cm->has_aborted()) { 2444 _gc_tracer_cm->report_concurrent_mode_failure(); 2445 } 2446 2447 _gc_timer_cm->register_gc_end(); 2448 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2449 2450 _concurrent_cycle_started = false; 2451 } 2452 } 2453 2454 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2455 if (_concurrent_cycle_started) { 2456 trace_heap_after_gc(_gc_tracer_cm); 2457 } 2458 } 2459 2460 G1YCType G1CollectedHeap::yc_type() { 2461 bool is_young = g1_policy()->gcs_are_young(); 2462 bool is_initial_mark = g1_policy()->during_initial_mark_pause(); 2463 bool is_during_mark = mark_in_progress(); 2464 2465 if (is_initial_mark) { 2466 return InitialMark; 2467 } else if (is_during_mark) { 2468 return DuringMark; 2469 } else if (is_young) { 2470 return Normal; 2471 } else { 2472 return Mixed; 2473 } 2474 } 2475 2476 void G1CollectedHeap::collect(GCCause::Cause cause) { 2477 assert_heap_not_locked(); 2478 2479 unsigned int gc_count_before; 2480 unsigned int old_marking_count_before; 2481 unsigned int full_gc_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 full_gc_count_before = total_full_collections(); 2493 old_marking_count_before = _old_marking_cycles_started; 2494 } 2495 2496 if (should_do_concurrent_full_gc(cause)) { 2497 // Schedule an initial-mark evacuation pause that will start a 2498 // concurrent cycle. We're setting word_size to 0 which means that 2499 // we are not requesting a post-GC allocation. 2500 VM_G1IncCollectionPause op(gc_count_before, 2501 0, /* word_size */ 2502 true, /* should_initiate_conc_mark */ 2503 g1_policy()->max_pause_time_ms(), 2504 cause); 2505 op.set_allocation_context(AllocationContext::current()); 2506 2507 VMThread::execute(&op); 2508 if (!op.pause_succeeded()) { 2509 if (old_marking_count_before == _old_marking_cycles_started) { 2510 retry_gc = op.should_retry_gc(); 2511 } else { 2512 // A Full GC happened while we were trying to schedule the 2513 // initial-mark GC. No point in starting a new cycle given 2514 // that the whole heap was collected anyway. 2515 } 2516 2517 if (retry_gc) { 2518 if (GC_locker::is_active_and_needs_gc()) { 2519 GC_locker::stall_until_clear(); 2520 } 2521 } 2522 } 2523 } else { 2524 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2525 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2526 2527 // Schedule a standard evacuation pause. We're setting word_size 2528 // to 0 which means that we are not requesting a post-GC allocation. 2529 VM_G1IncCollectionPause op(gc_count_before, 2530 0, /* word_size */ 2531 false, /* should_initiate_conc_mark */ 2532 g1_policy()->max_pause_time_ms(), 2533 cause); 2534 VMThread::execute(&op); 2535 } else { 2536 // Schedule a Full GC. 2537 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2538 VMThread::execute(&op); 2539 } 2540 } 2541 } while (retry_gc); 2542 } 2543 2544 bool G1CollectedHeap::is_in(const void* p) const { 2545 if (_hrm.reserved().contains(p)) { 2546 // Given that we know that p is in the reserved space, 2547 // heap_region_containing_raw() should successfully 2548 // return the containing region. 2549 HeapRegion* hr = heap_region_containing_raw(p); 2550 return hr->is_in(p); 2551 } else { 2552 return false; 2553 } 2554 } 2555 2556 #ifdef ASSERT 2557 bool G1CollectedHeap::is_in_exact(const void* p) const { 2558 bool contains = reserved_region().contains(p); 2559 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2560 if (contains && available) { 2561 return true; 2562 } else { 2563 return false; 2564 } 2565 } 2566 #endif 2567 2568 // Iteration functions. 2569 2570 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2571 2572 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2573 ExtendedOopClosure* _cl; 2574 public: 2575 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2576 bool doHeapRegion(HeapRegion* r) { 2577 if (!r->continuesHumongous()) { 2578 r->oop_iterate(_cl); 2579 } 2580 return false; 2581 } 2582 }; 2583 2584 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2585 IterateOopClosureRegionClosure blk(cl); 2586 heap_region_iterate(&blk); 2587 } 2588 2589 // Iterates an ObjectClosure over all objects within a HeapRegion. 2590 2591 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2592 ObjectClosure* _cl; 2593 public: 2594 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2595 bool doHeapRegion(HeapRegion* r) { 2596 if (! r->continuesHumongous()) { 2597 r->object_iterate(_cl); 2598 } 2599 return false; 2600 } 2601 }; 2602 2603 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2604 IterateObjectClosureRegionClosure blk(cl); 2605 heap_region_iterate(&blk); 2606 } 2607 2608 // Calls a SpaceClosure on a HeapRegion. 2609 2610 class SpaceClosureRegionClosure: public HeapRegionClosure { 2611 SpaceClosure* _cl; 2612 public: 2613 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2614 bool doHeapRegion(HeapRegion* r) { 2615 _cl->do_space(r); 2616 return false; 2617 } 2618 }; 2619 2620 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2621 SpaceClosureRegionClosure blk(cl); 2622 heap_region_iterate(&blk); 2623 } 2624 2625 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2626 _hrm.iterate(cl); 2627 } 2628 2629 void 2630 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2631 uint worker_id, 2632 uint num_workers, 2633 jint claim_value) const { 2634 _hrm.par_iterate(cl, worker_id, num_workers, claim_value); 2635 } 2636 2637 class ResetClaimValuesClosure: public HeapRegionClosure { 2638 public: 2639 bool doHeapRegion(HeapRegion* r) { 2640 r->set_claim_value(HeapRegion::InitialClaimValue); 2641 return false; 2642 } 2643 }; 2644 2645 void G1CollectedHeap::reset_heap_region_claim_values() { 2646 ResetClaimValuesClosure blk; 2647 heap_region_iterate(&blk); 2648 } 2649 2650 void G1CollectedHeap::reset_cset_heap_region_claim_values() { 2651 ResetClaimValuesClosure blk; 2652 collection_set_iterate(&blk); 2653 } 2654 2655 #ifdef ASSERT 2656 // This checks whether all regions in the heap have the correct claim 2657 // value. I also piggy-backed on this a check to ensure that the 2658 // humongous_start_region() information on "continues humongous" 2659 // regions is correct. 2660 2661 class CheckClaimValuesClosure : public HeapRegionClosure { 2662 private: 2663 jint _claim_value; 2664 uint _failures; 2665 HeapRegion* _sh_region; 2666 2667 public: 2668 CheckClaimValuesClosure(jint claim_value) : 2669 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2670 bool doHeapRegion(HeapRegion* r) { 2671 if (r->claim_value() != _claim_value) { 2672 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2673 "claim value = %d, should be %d", 2674 HR_FORMAT_PARAMS(r), 2675 r->claim_value(), _claim_value); 2676 ++_failures; 2677 } 2678 if (!r->isHumongous()) { 2679 _sh_region = NULL; 2680 } else if (r->startsHumongous()) { 2681 _sh_region = r; 2682 } else if (r->continuesHumongous()) { 2683 if (r->humongous_start_region() != _sh_region) { 2684 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2685 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2686 HR_FORMAT_PARAMS(r), 2687 r->humongous_start_region(), 2688 _sh_region); 2689 ++_failures; 2690 } 2691 } 2692 return false; 2693 } 2694 uint failures() { return _failures; } 2695 }; 2696 2697 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2698 CheckClaimValuesClosure cl(claim_value); 2699 heap_region_iterate(&cl); 2700 return cl.failures() == 0; 2701 } 2702 2703 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2704 private: 2705 jint _claim_value; 2706 uint _failures; 2707 2708 public: 2709 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2710 _claim_value(claim_value), _failures(0) { } 2711 2712 uint failures() { return _failures; } 2713 2714 bool doHeapRegion(HeapRegion* hr) { 2715 assert(hr->in_collection_set(), "how?"); 2716 assert(!hr->isHumongous(), "H-region in CSet"); 2717 if (hr->claim_value() != _claim_value) { 2718 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2719 "claim value = %d, should be %d", 2720 HR_FORMAT_PARAMS(hr), 2721 hr->claim_value(), _claim_value); 2722 _failures += 1; 2723 } 2724 return false; 2725 } 2726 }; 2727 2728 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2729 CheckClaimValuesInCSetHRClosure cl(claim_value); 2730 collection_set_iterate(&cl); 2731 return cl.failures() == 0; 2732 } 2733 #endif // ASSERT 2734 2735 // Clear the cached CSet starting regions and (more importantly) 2736 // the time stamps. Called when we reset the GC time stamp. 2737 void G1CollectedHeap::clear_cset_start_regions() { 2738 assert(_worker_cset_start_region != NULL, "sanity"); 2739 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2740 2741 int n_queues = MAX2((int)ParallelGCThreads, 1); 2742 for (int i = 0; i < n_queues; i++) { 2743 _worker_cset_start_region[i] = NULL; 2744 _worker_cset_start_region_time_stamp[i] = 0; 2745 } 2746 } 2747 2748 // Given the id of a worker, obtain or calculate a suitable 2749 // starting region for iterating over the current collection set. 2750 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2751 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2752 2753 HeapRegion* result = NULL; 2754 unsigned gc_time_stamp = get_gc_time_stamp(); 2755 2756 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2757 // Cached starting region for current worker was set 2758 // during the current pause - so it's valid. 2759 // Note: the cached starting heap region may be NULL 2760 // (when the collection set is empty). 2761 result = _worker_cset_start_region[worker_i]; 2762 assert(result == NULL || result->in_collection_set(), "sanity"); 2763 return result; 2764 } 2765 2766 // The cached entry was not valid so let's calculate 2767 // a suitable starting heap region for this worker. 2768 2769 // We want the parallel threads to start their collection 2770 // set iteration at different collection set regions to 2771 // avoid contention. 2772 // If we have: 2773 // n collection set regions 2774 // p threads 2775 // Then thread t will start at region floor ((t * n) / p) 2776 2777 result = g1_policy()->collection_set(); 2778 if (G1CollectedHeap::use_parallel_gc_threads()) { 2779 uint cs_size = g1_policy()->cset_region_length(); 2780 uint active_workers = workers()->active_workers(); 2781 assert(UseDynamicNumberOfGCThreads || 2782 active_workers == workers()->total_workers(), 2783 "Unless dynamic should use total workers"); 2784 2785 uint end_ind = (cs_size * worker_i) / active_workers; 2786 uint start_ind = 0; 2787 2788 if (worker_i > 0 && 2789 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2790 // Previous workers starting region is valid 2791 // so let's iterate from there 2792 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2793 result = _worker_cset_start_region[worker_i - 1]; 2794 } 2795 2796 for (uint i = start_ind; i < end_ind; i++) { 2797 result = result->next_in_collection_set(); 2798 } 2799 } 2800 2801 // Note: the calculated starting heap region may be NULL 2802 // (when the collection set is empty). 2803 assert(result == NULL || result->in_collection_set(), "sanity"); 2804 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2805 "should be updated only once per pause"); 2806 _worker_cset_start_region[worker_i] = result; 2807 OrderAccess::storestore(); 2808 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2809 return result; 2810 } 2811 2812 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2813 HeapRegion* r = g1_policy()->collection_set(); 2814 while (r != NULL) { 2815 HeapRegion* next = r->next_in_collection_set(); 2816 if (cl->doHeapRegion(r)) { 2817 cl->incomplete(); 2818 return; 2819 } 2820 r = next; 2821 } 2822 } 2823 2824 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2825 HeapRegionClosure *cl) { 2826 if (r == NULL) { 2827 // The CSet is empty so there's nothing to do. 2828 return; 2829 } 2830 2831 assert(r->in_collection_set(), 2832 "Start region must be a member of the collection set."); 2833 HeapRegion* cur = r; 2834 while (cur != NULL) { 2835 HeapRegion* next = cur->next_in_collection_set(); 2836 if (cl->doHeapRegion(cur) && false) { 2837 cl->incomplete(); 2838 return; 2839 } 2840 cur = next; 2841 } 2842 cur = g1_policy()->collection_set(); 2843 while (cur != r) { 2844 HeapRegion* next = cur->next_in_collection_set(); 2845 if (cl->doHeapRegion(cur) && false) { 2846 cl->incomplete(); 2847 return; 2848 } 2849 cur = next; 2850 } 2851 } 2852 2853 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2854 HeapRegion* result = _hrm.next_region_in_heap(from); 2855 while (result != NULL && result->isHumongous()) { 2856 result = _hrm.next_region_in_heap(result); 2857 } 2858 return result; 2859 } 2860 2861 Space* G1CollectedHeap::space_containing(const void* addr) const { 2862 return heap_region_containing(addr); 2863 } 2864 2865 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2866 Space* sp = space_containing(addr); 2867 return sp->block_start(addr); 2868 } 2869 2870 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2871 Space* sp = space_containing(addr); 2872 return sp->block_size(addr); 2873 } 2874 2875 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2876 Space* sp = space_containing(addr); 2877 return sp->block_is_obj(addr); 2878 } 2879 2880 bool G1CollectedHeap::supports_tlab_allocation() const { 2881 return true; 2882 } 2883 2884 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2885 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2886 } 2887 2888 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2889 return young_list()->eden_used_bytes(); 2890 } 2891 2892 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2893 // must be smaller than the humongous object limit. 2894 size_t G1CollectedHeap::max_tlab_size() const { 2895 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment); 2896 } 2897 2898 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2899 // Return the remaining space in the cur alloc region, but not less than 2900 // the min TLAB size. 2901 2902 // Also, this value can be at most the humongous object threshold, 2903 // since we can't allow tlabs to grow big enough to accommodate 2904 // humongous objects. 2905 2906 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get(); 2907 size_t max_tlab = max_tlab_size() * wordSize; 2908 if (hr == NULL) { 2909 return max_tlab; 2910 } else { 2911 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab); 2912 } 2913 } 2914 2915 size_t G1CollectedHeap::max_capacity() const { 2916 return _hrm.reserved().byte_size(); 2917 } 2918 2919 jlong G1CollectedHeap::millis_since_last_gc() { 2920 // assert(false, "NYI"); 2921 return 0; 2922 } 2923 2924 void G1CollectedHeap::prepare_for_verify() { 2925 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2926 ensure_parsability(false); 2927 } 2928 g1_rem_set()->prepare_for_verify(); 2929 } 2930 2931 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2932 VerifyOption vo) { 2933 switch (vo) { 2934 case VerifyOption_G1UsePrevMarking: 2935 return hr->obj_allocated_since_prev_marking(obj); 2936 case VerifyOption_G1UseNextMarking: 2937 return hr->obj_allocated_since_next_marking(obj); 2938 case VerifyOption_G1UseMarkWord: 2939 return false; 2940 default: 2941 ShouldNotReachHere(); 2942 } 2943 return false; // keep some compilers happy 2944 } 2945 2946 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2947 switch (vo) { 2948 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2949 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2950 case VerifyOption_G1UseMarkWord: return NULL; 2951 default: ShouldNotReachHere(); 2952 } 2953 return NULL; // keep some compilers happy 2954 } 2955 2956 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2957 switch (vo) { 2958 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2959 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2960 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2961 default: ShouldNotReachHere(); 2962 } 2963 return false; // keep some compilers happy 2964 } 2965 2966 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2967 switch (vo) { 2968 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2969 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2970 case VerifyOption_G1UseMarkWord: return "NONE"; 2971 default: ShouldNotReachHere(); 2972 } 2973 return NULL; // keep some compilers happy 2974 } 2975 2976 class VerifyRootsClosure: public OopClosure { 2977 private: 2978 G1CollectedHeap* _g1h; 2979 VerifyOption _vo; 2980 bool _failures; 2981 public: 2982 // _vo == UsePrevMarking -> use "prev" marking information, 2983 // _vo == UseNextMarking -> use "next" marking information, 2984 // _vo == UseMarkWord -> use mark word from object header. 2985 VerifyRootsClosure(VerifyOption vo) : 2986 _g1h(G1CollectedHeap::heap()), 2987 _vo(vo), 2988 _failures(false) { } 2989 2990 bool failures() { return _failures; } 2991 2992 template <class T> void do_oop_nv(T* p) { 2993 T heap_oop = oopDesc::load_heap_oop(p); 2994 if (!oopDesc::is_null(heap_oop)) { 2995 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2996 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2997 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 2998 "points to dead obj "PTR_FORMAT, p, (void*) obj); 2999 if (_vo == VerifyOption_G1UseMarkWord) { 3000 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 3001 } 3002 obj->print_on(gclog_or_tty); 3003 _failures = true; 3004 } 3005 } 3006 } 3007 3008 void do_oop(oop* p) { do_oop_nv(p); } 3009 void do_oop(narrowOop* p) { do_oop_nv(p); } 3010 }; 3011 3012 class G1VerifyCodeRootOopClosure: public OopClosure { 3013 G1CollectedHeap* _g1h; 3014 OopClosure* _root_cl; 3015 nmethod* _nm; 3016 VerifyOption _vo; 3017 bool _failures; 3018 3019 template <class T> void do_oop_work(T* p) { 3020 // First verify that this root is live 3021 _root_cl->do_oop(p); 3022 3023 if (!G1VerifyHeapRegionCodeRoots) { 3024 // We're not verifying the code roots attached to heap region. 3025 return; 3026 } 3027 3028 // Don't check the code roots during marking verification in a full GC 3029 if (_vo == VerifyOption_G1UseMarkWord) { 3030 return; 3031 } 3032 3033 // Now verify that the current nmethod (which contains p) is 3034 // in the code root list of the heap region containing the 3035 // object referenced by p. 3036 3037 T heap_oop = oopDesc::load_heap_oop(p); 3038 if (!oopDesc::is_null(heap_oop)) { 3039 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3040 3041 // Now fetch the region containing the object 3042 HeapRegion* hr = _g1h->heap_region_containing(obj); 3043 HeapRegionRemSet* hrrs = hr->rem_set(); 3044 // Verify that the strong code root list for this region 3045 // contains the nmethod 3046 if (!hrrs->strong_code_roots_list_contains(_nm)) { 3047 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" " 3048 "from nmethod "PTR_FORMAT" not in strong " 3049 "code roots for region ["PTR_FORMAT","PTR_FORMAT")", 3050 p, _nm, hr->bottom(), hr->end()); 3051 _failures = true; 3052 } 3053 } 3054 } 3055 3056 public: 3057 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 3058 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 3059 3060 void do_oop(oop* p) { do_oop_work(p); } 3061 void do_oop(narrowOop* p) { do_oop_work(p); } 3062 3063 void set_nmethod(nmethod* nm) { _nm = nm; } 3064 bool failures() { return _failures; } 3065 }; 3066 3067 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 3068 G1VerifyCodeRootOopClosure* _oop_cl; 3069 3070 public: 3071 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 3072 _oop_cl(oop_cl) {} 3073 3074 void do_code_blob(CodeBlob* cb) { 3075 nmethod* nm = cb->as_nmethod_or_null(); 3076 if (nm != NULL) { 3077 _oop_cl->set_nmethod(nm); 3078 nm->oops_do(_oop_cl); 3079 } 3080 } 3081 }; 3082 3083 class YoungRefCounterClosure : public OopClosure { 3084 G1CollectedHeap* _g1h; 3085 int _count; 3086 public: 3087 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 3088 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 3089 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 3090 3091 int count() { return _count; } 3092 void reset_count() { _count = 0; }; 3093 }; 3094 3095 class VerifyKlassClosure: public KlassClosure { 3096 YoungRefCounterClosure _young_ref_counter_closure; 3097 OopClosure *_oop_closure; 3098 public: 3099 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3100 void do_klass(Klass* k) { 3101 k->oops_do(_oop_closure); 3102 3103 _young_ref_counter_closure.reset_count(); 3104 k->oops_do(&_young_ref_counter_closure); 3105 if (_young_ref_counter_closure.count() > 0) { 3106 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); 3107 } 3108 } 3109 }; 3110 3111 class VerifyLivenessOopClosure: public OopClosure { 3112 G1CollectedHeap* _g1h; 3113 VerifyOption _vo; 3114 public: 3115 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3116 _g1h(g1h), _vo(vo) 3117 { } 3118 void do_oop(narrowOop *p) { do_oop_work(p); } 3119 void do_oop( oop *p) { do_oop_work(p); } 3120 3121 template <class T> void do_oop_work(T *p) { 3122 oop obj = oopDesc::load_decode_heap_oop(p); 3123 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3124 "Dead object referenced by a not dead object"); 3125 } 3126 }; 3127 3128 class VerifyObjsInRegionClosure: public ObjectClosure { 3129 private: 3130 G1CollectedHeap* _g1h; 3131 size_t _live_bytes; 3132 HeapRegion *_hr; 3133 VerifyOption _vo; 3134 public: 3135 // _vo == UsePrevMarking -> use "prev" marking information, 3136 // _vo == UseNextMarking -> use "next" marking information, 3137 // _vo == UseMarkWord -> use mark word from object header. 3138 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3139 : _live_bytes(0), _hr(hr), _vo(vo) { 3140 _g1h = G1CollectedHeap::heap(); 3141 } 3142 void do_object(oop o) { 3143 VerifyLivenessOopClosure isLive(_g1h, _vo); 3144 assert(o != NULL, "Huh?"); 3145 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3146 // If the object is alive according to the mark word, 3147 // then verify that the marking information agrees. 3148 // Note we can't verify the contra-positive of the 3149 // above: if the object is dead (according to the mark 3150 // word), it may not be marked, or may have been marked 3151 // but has since became dead, or may have been allocated 3152 // since the last marking. 3153 if (_vo == VerifyOption_G1UseMarkWord) { 3154 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3155 } 3156 3157 o->oop_iterate_no_header(&isLive); 3158 if (!_hr->obj_allocated_since_prev_marking(o)) { 3159 size_t obj_size = o->size(); // Make sure we don't overflow 3160 _live_bytes += (obj_size * HeapWordSize); 3161 } 3162 } 3163 } 3164 size_t live_bytes() { return _live_bytes; } 3165 }; 3166 3167 class PrintObjsInRegionClosure : public ObjectClosure { 3168 HeapRegion *_hr; 3169 G1CollectedHeap *_g1; 3170 public: 3171 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3172 _g1 = G1CollectedHeap::heap(); 3173 }; 3174 3175 void do_object(oop o) { 3176 if (o != NULL) { 3177 HeapWord *start = (HeapWord *) o; 3178 size_t word_sz = o->size(); 3179 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3180 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3181 (void*) o, word_sz, 3182 _g1->isMarkedPrev(o), 3183 _g1->isMarkedNext(o), 3184 _hr->obj_allocated_since_prev_marking(o)); 3185 HeapWord *end = start + word_sz; 3186 HeapWord *cur; 3187 int *val; 3188 for (cur = start; cur < end; cur++) { 3189 val = (int *) cur; 3190 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 3191 } 3192 } 3193 } 3194 }; 3195 3196 class VerifyRegionClosure: public HeapRegionClosure { 3197 private: 3198 bool _par; 3199 VerifyOption _vo; 3200 bool _failures; 3201 public: 3202 // _vo == UsePrevMarking -> use "prev" marking information, 3203 // _vo == UseNextMarking -> use "next" marking information, 3204 // _vo == UseMarkWord -> use mark word from object header. 3205 VerifyRegionClosure(bool par, VerifyOption vo) 3206 : _par(par), 3207 _vo(vo), 3208 _failures(false) {} 3209 3210 bool failures() { 3211 return _failures; 3212 } 3213 3214 bool doHeapRegion(HeapRegion* r) { 3215 if (!r->continuesHumongous()) { 3216 bool failures = false; 3217 r->verify(_vo, &failures); 3218 if (failures) { 3219 _failures = true; 3220 } else { 3221 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3222 r->object_iterate(¬_dead_yet_cl); 3223 if (_vo != VerifyOption_G1UseNextMarking) { 3224 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3225 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3226 "max_live_bytes "SIZE_FORMAT" " 3227 "< calculated "SIZE_FORMAT, 3228 r->bottom(), r->end(), 3229 r->max_live_bytes(), 3230 not_dead_yet_cl.live_bytes()); 3231 _failures = true; 3232 } 3233 } else { 3234 // When vo == UseNextMarking we cannot currently do a sanity 3235 // check on the live bytes as the calculation has not been 3236 // finalized yet. 3237 } 3238 } 3239 } 3240 return false; // stop the region iteration if we hit a failure 3241 } 3242 }; 3243 3244 // This is the task used for parallel verification of the heap regions 3245 3246 class G1ParVerifyTask: public AbstractGangTask { 3247 private: 3248 G1CollectedHeap* _g1h; 3249 VerifyOption _vo; 3250 bool _failures; 3251 3252 public: 3253 // _vo == UsePrevMarking -> use "prev" marking information, 3254 // _vo == UseNextMarking -> use "next" marking information, 3255 // _vo == UseMarkWord -> use mark word from object header. 3256 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3257 AbstractGangTask("Parallel verify task"), 3258 _g1h(g1h), 3259 _vo(vo), 3260 _failures(false) { } 3261 3262 bool failures() { 3263 return _failures; 3264 } 3265 3266 void work(uint worker_id) { 3267 HandleMark hm; 3268 VerifyRegionClosure blk(true, _vo); 3269 _g1h->heap_region_par_iterate_chunked(&blk, worker_id, 3270 _g1h->workers()->active_workers(), 3271 HeapRegion::ParVerifyClaimValue); 3272 if (blk.failures()) { 3273 _failures = true; 3274 } 3275 } 3276 }; 3277 3278 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3279 if (SafepointSynchronize::is_at_safepoint()) { 3280 assert(Thread::current()->is_VM_thread(), 3281 "Expected to be executed serially by the VM thread at this point"); 3282 3283 if (!silent) { gclog_or_tty->print("Roots "); } 3284 VerifyRootsClosure rootsCl(vo); 3285 VerifyKlassClosure klassCl(this, &rootsCl); 3286 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3287 3288 // We apply the relevant closures to all the oops in the 3289 // system dictionary, class loader data graph, the string table 3290 // and the nmethods in the code cache. 3291 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3292 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3293 3294 process_all_roots(true, // activate StrongRootsScope 3295 SO_AllCodeCache, // roots scanning options 3296 &rootsCl, 3297 &cldCl, 3298 &blobsCl); 3299 3300 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3301 3302 if (vo != VerifyOption_G1UseMarkWord) { 3303 // If we're verifying during a full GC then the region sets 3304 // will have been torn down at the start of the GC. Therefore 3305 // verifying the region sets will fail. So we only verify 3306 // the region sets when not in a full GC. 3307 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3308 verify_region_sets(); 3309 } 3310 3311 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3312 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3313 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3314 "sanity check"); 3315 3316 G1ParVerifyTask task(this, vo); 3317 assert(UseDynamicNumberOfGCThreads || 3318 workers()->active_workers() == workers()->total_workers(), 3319 "If not dynamic should be using all the workers"); 3320 int n_workers = workers()->active_workers(); 3321 set_par_threads(n_workers); 3322 workers()->run_task(&task); 3323 set_par_threads(0); 3324 if (task.failures()) { 3325 failures = true; 3326 } 3327 3328 // Checks that the expected amount of parallel work was done. 3329 // The implication is that n_workers is > 0. 3330 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3331 "sanity check"); 3332 3333 reset_heap_region_claim_values(); 3334 3335 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3336 "sanity check"); 3337 } else { 3338 VerifyRegionClosure blk(false, vo); 3339 heap_region_iterate(&blk); 3340 if (blk.failures()) { 3341 failures = true; 3342 } 3343 } 3344 if (!silent) gclog_or_tty->print("RemSet "); 3345 rem_set()->verify(); 3346 3347 if (G1StringDedup::is_enabled()) { 3348 if (!silent) gclog_or_tty->print("StrDedup "); 3349 G1StringDedup::verify(); 3350 } 3351 3352 if (failures) { 3353 gclog_or_tty->print_cr("Heap:"); 3354 // It helps to have the per-region information in the output to 3355 // help us track down what went wrong. This is why we call 3356 // print_extended_on() instead of print_on(). 3357 print_extended_on(gclog_or_tty); 3358 gclog_or_tty->cr(); 3359 #ifndef PRODUCT 3360 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3361 concurrent_mark()->print_reachable("at-verification-failure", 3362 vo, false /* all */); 3363 } 3364 #endif 3365 gclog_or_tty->flush(); 3366 } 3367 guarantee(!failures, "there should not have been any failures"); 3368 } else { 3369 if (!silent) { 3370 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3371 if (G1StringDedup::is_enabled()) { 3372 gclog_or_tty->print(", StrDedup"); 3373 } 3374 gclog_or_tty->print(") "); 3375 } 3376 } 3377 } 3378 3379 void G1CollectedHeap::verify(bool silent) { 3380 verify(silent, VerifyOption_G1UsePrevMarking); 3381 } 3382 3383 double G1CollectedHeap::verify(bool guard, const char* msg) { 3384 double verify_time_ms = 0.0; 3385 3386 if (guard && total_collections() >= VerifyGCStartAt) { 3387 double verify_start = os::elapsedTime(); 3388 HandleMark hm; // Discard invalid handles created during verification 3389 prepare_for_verify(); 3390 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3391 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3392 } 3393 3394 return verify_time_ms; 3395 } 3396 3397 void G1CollectedHeap::verify_before_gc() { 3398 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3399 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3400 } 3401 3402 void G1CollectedHeap::verify_after_gc() { 3403 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3404 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3405 } 3406 3407 class PrintRegionClosure: public HeapRegionClosure { 3408 outputStream* _st; 3409 public: 3410 PrintRegionClosure(outputStream* st) : _st(st) {} 3411 bool doHeapRegion(HeapRegion* r) { 3412 r->print_on(_st); 3413 return false; 3414 } 3415 }; 3416 3417 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3418 const HeapRegion* hr, 3419 const VerifyOption vo) const { 3420 switch (vo) { 3421 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3422 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3423 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3424 default: ShouldNotReachHere(); 3425 } 3426 return false; // keep some compilers happy 3427 } 3428 3429 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3430 const VerifyOption vo) const { 3431 switch (vo) { 3432 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3433 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3434 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3435 default: ShouldNotReachHere(); 3436 } 3437 return false; // keep some compilers happy 3438 } 3439 3440 void G1CollectedHeap::print_on(outputStream* st) const { 3441 st->print(" %-20s", "garbage-first heap"); 3442 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3443 capacity()/K, used_unlocked()/K); 3444 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3445 _hrm.reserved().start(), 3446 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords, 3447 _hrm.reserved().end()); 3448 st->cr(); 3449 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3450 uint young_regions = _young_list->length(); 3451 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3452 (size_t) young_regions * HeapRegion::GrainBytes / K); 3453 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3454 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3455 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3456 st->cr(); 3457 MetaspaceAux::print_on(st); 3458 } 3459 3460 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3461 print_on(st); 3462 3463 // Print the per-region information. 3464 st->cr(); 3465 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3466 "HS=humongous(starts), HC=humongous(continues), " 3467 "CS=collection set, F=free, TS=gc time stamp, " 3468 "PTAMS=previous top-at-mark-start, " 3469 "NTAMS=next top-at-mark-start)"); 3470 PrintRegionClosure blk(st); 3471 heap_region_iterate(&blk); 3472 } 3473 3474 void G1CollectedHeap::print_on_error(outputStream* st) const { 3475 this->CollectedHeap::print_on_error(st); 3476 3477 if (_cm != NULL) { 3478 st->cr(); 3479 _cm->print_on_error(st); 3480 } 3481 } 3482 3483 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3484 if (G1CollectedHeap::use_parallel_gc_threads()) { 3485 workers()->print_worker_threads_on(st); 3486 } 3487 _cmThread->print_on(st); 3488 st->cr(); 3489 _cm->print_worker_threads_on(st); 3490 _cg1r->print_worker_threads_on(st); 3491 if (G1StringDedup::is_enabled()) { 3492 G1StringDedup::print_worker_threads_on(st); 3493 } 3494 } 3495 3496 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3497 if (G1CollectedHeap::use_parallel_gc_threads()) { 3498 workers()->threads_do(tc); 3499 } 3500 tc->do_thread(_cmThread); 3501 _cg1r->threads_do(tc); 3502 if (G1StringDedup::is_enabled()) { 3503 G1StringDedup::threads_do(tc); 3504 } 3505 } 3506 3507 void G1CollectedHeap::print_tracing_info() const { 3508 // We'll overload this to mean "trace GC pause statistics." 3509 if (TraceGen0Time || TraceGen1Time) { 3510 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3511 // to that. 3512 g1_policy()->print_tracing_info(); 3513 } 3514 if (G1SummarizeRSetStats) { 3515 g1_rem_set()->print_summary_info(); 3516 } 3517 if (G1SummarizeConcMark) { 3518 concurrent_mark()->print_summary_info(); 3519 } 3520 g1_policy()->print_yg_surv_rate_info(); 3521 SpecializationStats::print(); 3522 } 3523 3524 #ifndef PRODUCT 3525 // Helpful for debugging RSet issues. 3526 3527 class PrintRSetsClosure : public HeapRegionClosure { 3528 private: 3529 const char* _msg; 3530 size_t _occupied_sum; 3531 3532 public: 3533 bool doHeapRegion(HeapRegion* r) { 3534 HeapRegionRemSet* hrrs = r->rem_set(); 3535 size_t occupied = hrrs->occupied(); 3536 _occupied_sum += occupied; 3537 3538 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3539 HR_FORMAT_PARAMS(r)); 3540 if (occupied == 0) { 3541 gclog_or_tty->print_cr(" RSet is empty"); 3542 } else { 3543 hrrs->print(); 3544 } 3545 gclog_or_tty->print_cr("----------"); 3546 return false; 3547 } 3548 3549 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3550 gclog_or_tty->cr(); 3551 gclog_or_tty->print_cr("========================================"); 3552 gclog_or_tty->print_cr("%s", msg); 3553 gclog_or_tty->cr(); 3554 } 3555 3556 ~PrintRSetsClosure() { 3557 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3558 gclog_or_tty->print_cr("========================================"); 3559 gclog_or_tty->cr(); 3560 } 3561 }; 3562 3563 void G1CollectedHeap::print_cset_rsets() { 3564 PrintRSetsClosure cl("Printing CSet RSets"); 3565 collection_set_iterate(&cl); 3566 } 3567 3568 void G1CollectedHeap::print_all_rsets() { 3569 PrintRSetsClosure cl("Printing All RSets");; 3570 heap_region_iterate(&cl); 3571 } 3572 #endif // PRODUCT 3573 3574 G1CollectedHeap* G1CollectedHeap::heap() { 3575 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3576 "not a garbage-first heap"); 3577 return _g1h; 3578 } 3579 3580 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3581 // always_do_update_barrier = false; 3582 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3583 // Fill TLAB's and such 3584 accumulate_statistics_all_tlabs(); 3585 ensure_parsability(true); 3586 3587 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3588 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3589 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3590 } 3591 } 3592 3593 void G1CollectedHeap::gc_epilogue(bool full) { 3594 3595 if (G1SummarizeRSetStats && 3596 (G1SummarizeRSetStatsPeriod > 0) && 3597 // we are at the end of the GC. Total collections has already been increased. 3598 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3599 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3600 } 3601 3602 // FIXME: what is this about? 3603 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3604 // is set. 3605 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3606 "derived pointer present")); 3607 // always_do_update_barrier = true; 3608 3609 resize_all_tlabs(); 3610 allocation_context_stats().update(full); 3611 3612 // We have just completed a GC. Update the soft reference 3613 // policy with the new heap occupancy 3614 Universe::update_heap_info_at_gc(); 3615 } 3616 3617 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3618 unsigned int gc_count_before, 3619 bool* succeeded, 3620 GCCause::Cause gc_cause) { 3621 assert_heap_not_locked_and_not_at_safepoint(); 3622 g1_policy()->record_stop_world_start(); 3623 VM_G1IncCollectionPause op(gc_count_before, 3624 word_size, 3625 false, /* should_initiate_conc_mark */ 3626 g1_policy()->max_pause_time_ms(), 3627 gc_cause); 3628 3629 op.set_allocation_context(AllocationContext::current()); 3630 VMThread::execute(&op); 3631 3632 HeapWord* result = op.result(); 3633 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3634 assert(result == NULL || ret_succeeded, 3635 "the result should be NULL if the VM did not succeed"); 3636 *succeeded = ret_succeeded; 3637 3638 assert_heap_not_locked(); 3639 return result; 3640 } 3641 3642 void 3643 G1CollectedHeap::doConcurrentMark() { 3644 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3645 if (!_cmThread->in_progress()) { 3646 _cmThread->set_started(); 3647 CGC_lock->notify(); 3648 } 3649 } 3650 3651 size_t G1CollectedHeap::pending_card_num() { 3652 size_t extra_cards = 0; 3653 JavaThread *curr = Threads::first(); 3654 while (curr != NULL) { 3655 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3656 extra_cards += dcq.size(); 3657 curr = curr->next(); 3658 } 3659 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3660 size_t buffer_size = dcqs.buffer_size(); 3661 size_t buffer_num = dcqs.completed_buffers_num(); 3662 3663 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3664 // in bytes - not the number of 'entries'. We need to convert 3665 // into a number of cards. 3666 return (buffer_size * buffer_num + extra_cards) / oopSize; 3667 } 3668 3669 size_t G1CollectedHeap::cards_scanned() { 3670 return g1_rem_set()->cardsScanned(); 3671 } 3672 3673 bool G1CollectedHeap::humongous_region_is_always_live(uint index) { 3674 HeapRegion* region = region_at(index); 3675 assert(region->startsHumongous(), "Must start a humongous object"); 3676 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty(); 3677 } 3678 3679 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3680 private: 3681 size_t _total_humongous; 3682 size_t _candidate_humongous; 3683 public: 3684 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) { 3685 } 3686 3687 virtual bool doHeapRegion(HeapRegion* r) { 3688 if (!r->startsHumongous()) { 3689 return false; 3690 } 3691 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3692 3693 uint region_idx = r->hrm_index(); 3694 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx); 3695 // Is_candidate already filters out humongous regions with some remembered set. 3696 // This will not lead to humongous object that we mistakenly keep alive because 3697 // during young collection the remembered sets will only be added to. 3698 if (is_candidate) { 3699 g1h->register_humongous_region_with_in_cset_fast_test(region_idx); 3700 _candidate_humongous++; 3701 } 3702 _total_humongous++; 3703 3704 return false; 3705 } 3706 3707 size_t total_humongous() const { return _total_humongous; } 3708 size_t candidate_humongous() const { return _candidate_humongous; } 3709 }; 3710 3711 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() { 3712 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) { 3713 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0); 3714 return; 3715 } 3716 3717 RegisterHumongousWithInCSetFastTestClosure cl; 3718 heap_region_iterate(&cl); 3719 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(), 3720 cl.candidate_humongous()); 3721 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3722 3723 if (_has_humongous_reclaim_candidates || G1TraceReclaimDeadHumongousObjectsAtYoungGC) { 3724 clear_humongous_is_live_table(); 3725 } 3726 } 3727 3728 void 3729 G1CollectedHeap::setup_surviving_young_words() { 3730 assert(_surviving_young_words == NULL, "pre-condition"); 3731 uint array_length = g1_policy()->young_cset_region_length(); 3732 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3733 if (_surviving_young_words == NULL) { 3734 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3735 "Not enough space for young surv words summary."); 3736 } 3737 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3738 #ifdef ASSERT 3739 for (uint i = 0; i < array_length; ++i) { 3740 assert( _surviving_young_words[i] == 0, "memset above" ); 3741 } 3742 #endif // !ASSERT 3743 } 3744 3745 void 3746 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3747 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3748 uint array_length = g1_policy()->young_cset_region_length(); 3749 for (uint i = 0; i < array_length; ++i) { 3750 _surviving_young_words[i] += surv_young_words[i]; 3751 } 3752 } 3753 3754 void 3755 G1CollectedHeap::cleanup_surviving_young_words() { 3756 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3757 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3758 _surviving_young_words = NULL; 3759 } 3760 3761 #ifdef ASSERT 3762 class VerifyCSetClosure: public HeapRegionClosure { 3763 public: 3764 bool doHeapRegion(HeapRegion* hr) { 3765 // Here we check that the CSet region's RSet is ready for parallel 3766 // iteration. The fields that we'll verify are only manipulated 3767 // when the region is part of a CSet and is collected. Afterwards, 3768 // we reset these fields when we clear the region's RSet (when the 3769 // region is freed) so they are ready when the region is 3770 // re-allocated. The only exception to this is if there's an 3771 // evacuation failure and instead of freeing the region we leave 3772 // it in the heap. In that case, we reset these fields during 3773 // evacuation failure handling. 3774 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3775 3776 // Here's a good place to add any other checks we'd like to 3777 // perform on CSet regions. 3778 return false; 3779 } 3780 }; 3781 #endif // ASSERT 3782 3783 #if TASKQUEUE_STATS 3784 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3785 st->print_raw_cr("GC Task Stats"); 3786 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3787 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3788 } 3789 3790 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3791 print_taskqueue_stats_hdr(st); 3792 3793 TaskQueueStats totals; 3794 const int n = workers() != NULL ? workers()->total_workers() : 1; 3795 for (int i = 0; i < n; ++i) { 3796 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3797 totals += task_queue(i)->stats; 3798 } 3799 st->print_raw("tot "); totals.print(st); st->cr(); 3800 3801 DEBUG_ONLY(totals.verify()); 3802 } 3803 3804 void G1CollectedHeap::reset_taskqueue_stats() { 3805 const int n = workers() != NULL ? workers()->total_workers() : 1; 3806 for (int i = 0; i < n; ++i) { 3807 task_queue(i)->stats.reset(); 3808 } 3809 } 3810 #endif // TASKQUEUE_STATS 3811 3812 void G1CollectedHeap::log_gc_header() { 3813 if (!G1Log::fine()) { 3814 return; 3815 } 3816 3817 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id()); 3818 3819 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3820 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3821 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3822 3823 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3824 } 3825 3826 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3827 if (!G1Log::fine()) { 3828 return; 3829 } 3830 3831 if (G1Log::finer()) { 3832 if (evacuation_failed()) { 3833 gclog_or_tty->print(" (to-space exhausted)"); 3834 } 3835 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3836 g1_policy()->phase_times()->note_gc_end(); 3837 g1_policy()->phase_times()->print(pause_time_sec); 3838 g1_policy()->print_detailed_heap_transition(); 3839 } else { 3840 if (evacuation_failed()) { 3841 gclog_or_tty->print("--"); 3842 } 3843 g1_policy()->print_heap_transition(); 3844 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3845 } 3846 gclog_or_tty->flush(); 3847 } 3848 3849 bool 3850 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3851 assert_at_safepoint(true /* should_be_vm_thread */); 3852 guarantee(!is_gc_active(), "collection is not reentrant"); 3853 3854 if (GC_locker::check_active_before_gc()) { 3855 return false; 3856 } 3857 3858 _gc_timer_stw->register_gc_start(); 3859 3860 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3861 3862 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3863 ResourceMark rm; 3864 3865 print_heap_before_gc(); 3866 trace_heap_before_gc(_gc_tracer_stw); 3867 3868 verify_region_sets_optional(); 3869 verify_dirty_young_regions(); 3870 3871 // This call will decide whether this pause is an initial-mark 3872 // pause. If it is, during_initial_mark_pause() will return true 3873 // for the duration of this pause. 3874 g1_policy()->decide_on_conc_mark_initiation(); 3875 3876 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3877 assert(!g1_policy()->during_initial_mark_pause() || 3878 g1_policy()->gcs_are_young(), "sanity"); 3879 3880 // We also do not allow mixed GCs during marking. 3881 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3882 3883 // Record whether this pause is an initial mark. When the current 3884 // thread has completed its logging output and it's safe to signal 3885 // the CM thread, the flag's value in the policy has been reset. 3886 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3887 3888 // Inner scope for scope based logging, timers, and stats collection 3889 { 3890 EvacuationInfo evacuation_info; 3891 3892 if (g1_policy()->during_initial_mark_pause()) { 3893 // We are about to start a marking cycle, so we increment the 3894 // full collection counter. 3895 increment_old_marking_cycles_started(); 3896 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3897 } 3898 3899 _gc_tracer_stw->report_yc_type(yc_type()); 3900 3901 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3902 3903 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3904 workers()->active_workers() : 1); 3905 double pause_start_sec = os::elapsedTime(); 3906 g1_policy()->phase_times()->note_gc_start(active_workers); 3907 log_gc_header(); 3908 3909 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3910 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3911 3912 // If the secondary_free_list is not empty, append it to the 3913 // free_list. No need to wait for the cleanup operation to finish; 3914 // the region allocation code will check the secondary_free_list 3915 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3916 // set, skip this step so that the region allocation code has to 3917 // get entries from the secondary_free_list. 3918 if (!G1StressConcRegionFreeing) { 3919 append_secondary_free_list_if_not_empty_with_lock(); 3920 } 3921 3922 assert(check_young_list_well_formed(), "young list should be well formed"); 3923 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3924 "sanity check"); 3925 3926 // Don't dynamically change the number of GC threads this early. A value of 3927 // 0 is used to indicate serial work. When parallel work is done, 3928 // it will be set. 3929 3930 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3931 IsGCActiveMark x; 3932 3933 gc_prologue(false); 3934 increment_total_collections(false /* full gc */); 3935 increment_gc_time_stamp(); 3936 3937 verify_before_gc(); 3938 check_bitmaps("GC Start"); 3939 3940 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3941 3942 // Please see comment in g1CollectedHeap.hpp and 3943 // G1CollectedHeap::ref_processing_init() to see how 3944 // reference processing currently works in G1. 3945 3946 // Enable discovery in the STW reference processor 3947 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 3948 true /*verify_no_refs*/); 3949 3950 { 3951 // We want to temporarily turn off discovery by the 3952 // CM ref processor, if necessary, and turn it back on 3953 // on again later if we do. Using a scoped 3954 // NoRefDiscovery object will do this. 3955 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3956 3957 // Forget the current alloc region (we might even choose it to be part 3958 // of the collection set!). 3959 _allocator->release_mutator_alloc_region(); 3960 3961 // We should call this after we retire the mutator alloc 3962 // region(s) so that all the ALLOC / RETIRE events are generated 3963 // before the start GC event. 3964 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3965 3966 // This timing is only used by the ergonomics to handle our pause target. 3967 // It is unclear why this should not include the full pause. We will 3968 // investigate this in CR 7178365. 3969 // 3970 // Preserving the old comment here if that helps the investigation: 3971 // 3972 // The elapsed time induced by the start time below deliberately elides 3973 // the possible verification above. 3974 double sample_start_time_sec = os::elapsedTime(); 3975 3976 #if YOUNG_LIST_VERBOSE 3977 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3978 _young_list->print(); 3979 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3980 #endif // YOUNG_LIST_VERBOSE 3981 3982 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3983 3984 double scan_wait_start = os::elapsedTime(); 3985 // We have to wait until the CM threads finish scanning the 3986 // root regions as it's the only way to ensure that all the 3987 // objects on them have been correctly scanned before we start 3988 // moving them during the GC. 3989 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3990 double wait_time_ms = 0.0; 3991 if (waited) { 3992 double scan_wait_end = os::elapsedTime(); 3993 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3994 } 3995 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3996 3997 #if YOUNG_LIST_VERBOSE 3998 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3999 _young_list->print(); 4000 #endif // YOUNG_LIST_VERBOSE 4001 4002 if (g1_policy()->during_initial_mark_pause()) { 4003 concurrent_mark()->checkpointRootsInitialPre(); 4004 } 4005 4006 #if YOUNG_LIST_VERBOSE 4007 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 4008 _young_list->print(); 4009 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4010 #endif // YOUNG_LIST_VERBOSE 4011 4012 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info); 4013 4014 register_humongous_regions_with_in_cset_fast_test(); 4015 4016 _cm->note_start_of_gc(); 4017 // We should not verify the per-thread SATB buffers given that 4018 // we have not filtered them yet (we'll do so during the 4019 // GC). We also call this after finalize_cset() to 4020 // ensure that the CSet has been finalized. 4021 _cm->verify_no_cset_oops(true /* verify_stacks */, 4022 true /* verify_enqueued_buffers */, 4023 false /* verify_thread_buffers */, 4024 true /* verify_fingers */); 4025 4026 if (_hr_printer.is_active()) { 4027 HeapRegion* hr = g1_policy()->collection_set(); 4028 while (hr != NULL) { 4029 _hr_printer.cset(hr); 4030 hr = hr->next_in_collection_set(); 4031 } 4032 } 4033 4034 #ifdef ASSERT 4035 VerifyCSetClosure cl; 4036 collection_set_iterate(&cl); 4037 #endif // ASSERT 4038 4039 setup_surviving_young_words(); 4040 4041 // Initialize the GC alloc regions. 4042 _allocator->init_gc_alloc_regions(evacuation_info); 4043 4044 // Actually do the work... 4045 evacuate_collection_set(evacuation_info); 4046 4047 // We do this to mainly verify the per-thread SATB buffers 4048 // (which have been filtered by now) since we didn't verify 4049 // them earlier. No point in re-checking the stacks / enqueued 4050 // buffers given that the CSet has not changed since last time 4051 // we checked. 4052 _cm->verify_no_cset_oops(false /* verify_stacks */, 4053 false /* verify_enqueued_buffers */, 4054 true /* verify_thread_buffers */, 4055 true /* verify_fingers */); 4056 4057 free_collection_set(g1_policy()->collection_set(), evacuation_info); 4058 4059 eagerly_reclaim_humongous_regions(); 4060 4061 g1_policy()->clear_collection_set(); 4062 4063 cleanup_surviving_young_words(); 4064 4065 // Start a new incremental collection set for the next pause. 4066 g1_policy()->start_incremental_cset_building(); 4067 4068 clear_cset_fast_test(); 4069 4070 _young_list->reset_sampled_info(); 4071 4072 // Don't check the whole heap at this point as the 4073 // GC alloc regions from this pause have been tagged 4074 // as survivors and moved on to the survivor list. 4075 // Survivor regions will fail the !is_young() check. 4076 assert(check_young_list_empty(false /* check_heap */), 4077 "young list should be empty"); 4078 4079 #if YOUNG_LIST_VERBOSE 4080 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 4081 _young_list->print(); 4082 #endif // YOUNG_LIST_VERBOSE 4083 4084 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 4085 _young_list->first_survivor_region(), 4086 _young_list->last_survivor_region()); 4087 4088 _young_list->reset_auxilary_lists(); 4089 4090 if (evacuation_failed()) { 4091 _allocator->set_used(recalculate_used()); 4092 uint n_queues = MAX2((int)ParallelGCThreads, 1); 4093 for (uint i = 0; i < n_queues; i++) { 4094 if (_evacuation_failed_info_array[i].has_failed()) { 4095 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 4096 } 4097 } 4098 } else { 4099 // The "used" of the the collection set have already been subtracted 4100 // when they were freed. Add in the bytes evacuated. 4101 _allocator->increase_used(g1_policy()->bytes_copied_during_gc()); 4102 } 4103 4104 if (g1_policy()->during_initial_mark_pause()) { 4105 // We have to do this before we notify the CM threads that 4106 // they can start working to make sure that all the 4107 // appropriate initialization is done on the CM object. 4108 concurrent_mark()->checkpointRootsInitialPost(); 4109 set_marking_started(); 4110 // Note that we don't actually trigger the CM thread at 4111 // this point. We do that later when we're sure that 4112 // the current thread has completed its logging output. 4113 } 4114 4115 allocate_dummy_regions(); 4116 4117 #if YOUNG_LIST_VERBOSE 4118 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 4119 _young_list->print(); 4120 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4121 #endif // YOUNG_LIST_VERBOSE 4122 4123 _allocator->init_mutator_alloc_region(); 4124 4125 { 4126 size_t expand_bytes = g1_policy()->expansion_amount(); 4127 if (expand_bytes > 0) { 4128 size_t bytes_before = capacity(); 4129 // No need for an ergo verbose message here, 4130 // expansion_amount() does this when it returns a value > 0. 4131 if (!expand(expand_bytes)) { 4132 // We failed to expand the heap. Cannot do anything about it. 4133 } 4134 } 4135 } 4136 4137 // We redo the verification but now wrt to the new CSet which 4138 // has just got initialized after the previous CSet was freed. 4139 _cm->verify_no_cset_oops(true /* verify_stacks */, 4140 true /* verify_enqueued_buffers */, 4141 true /* verify_thread_buffers */, 4142 true /* verify_fingers */); 4143 _cm->note_end_of_gc(); 4144 4145 // This timing is only used by the ergonomics to handle our pause target. 4146 // It is unclear why this should not include the full pause. We will 4147 // investigate this in CR 7178365. 4148 double sample_end_time_sec = os::elapsedTime(); 4149 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 4150 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info); 4151 4152 MemoryService::track_memory_usage(); 4153 4154 // In prepare_for_verify() below we'll need to scan the deferred 4155 // update buffers to bring the RSets up-to-date if 4156 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 4157 // the update buffers we'll probably need to scan cards on the 4158 // regions we just allocated to (i.e., the GC alloc 4159 // regions). However, during the last GC we called 4160 // set_saved_mark() on all the GC alloc regions, so card 4161 // scanning might skip the [saved_mark_word()...top()] area of 4162 // those regions (i.e., the area we allocated objects into 4163 // during the last GC). But it shouldn't. Given that 4164 // saved_mark_word() is conditional on whether the GC time stamp 4165 // on the region is current or not, by incrementing the GC time 4166 // stamp here we invalidate all the GC time stamps on all the 4167 // regions and saved_mark_word() will simply return top() for 4168 // all the regions. This is a nicer way of ensuring this rather 4169 // than iterating over the regions and fixing them. In fact, the 4170 // GC time stamp increment here also ensures that 4171 // saved_mark_word() will return top() between pauses, i.e., 4172 // during concurrent refinement. So we don't need the 4173 // is_gc_active() check to decided which top to use when 4174 // scanning cards (see CR 7039627). 4175 increment_gc_time_stamp(); 4176 4177 verify_after_gc(); 4178 check_bitmaps("GC End"); 4179 4180 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4181 ref_processor_stw()->verify_no_references_recorded(); 4182 4183 // CM reference discovery will be re-enabled if necessary. 4184 } 4185 4186 // We should do this after we potentially expand the heap so 4187 // that all the COMMIT events are generated before the end GC 4188 // event, and after we retire the GC alloc regions so that all 4189 // RETIRE events are generated before the end GC event. 4190 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4191 4192 #ifdef TRACESPINNING 4193 ParallelTaskTerminator::print_termination_counts(); 4194 #endif 4195 4196 gc_epilogue(false); 4197 } 4198 4199 // Print the remainder of the GC log output. 4200 log_gc_footer(os::elapsedTime() - pause_start_sec); 4201 4202 // It is not yet to safe to tell the concurrent mark to 4203 // start as we have some optional output below. We don't want the 4204 // output from the concurrent mark thread interfering with this 4205 // logging output either. 4206 4207 _hrm.verify_optional(); 4208 verify_region_sets_optional(); 4209 4210 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4211 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4212 4213 print_heap_after_gc(); 4214 trace_heap_after_gc(_gc_tracer_stw); 4215 4216 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4217 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4218 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4219 // before any GC notifications are raised. 4220 g1mm()->update_sizes(); 4221 4222 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4223 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4224 _gc_timer_stw->register_gc_end(); 4225 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4226 } 4227 // It should now be safe to tell the concurrent mark thread to start 4228 // without its logging output interfering with the logging output 4229 // that came from the pause. 4230 4231 if (should_start_conc_mark) { 4232 // CAUTION: after the doConcurrentMark() call below, 4233 // the concurrent marking thread(s) could be running 4234 // concurrently with us. Make sure that anything after 4235 // this point does not assume that we are the only GC thread 4236 // running. Note: of course, the actual marking work will 4237 // not start until the safepoint itself is released in 4238 // SuspendibleThreadSet::desynchronize(). 4239 doConcurrentMark(); 4240 } 4241 4242 return true; 4243 } 4244 4245 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4246 { 4247 size_t gclab_word_size; 4248 switch (purpose) { 4249 case GCAllocForSurvived: 4250 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4251 break; 4252 case GCAllocForTenured: 4253 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4254 break; 4255 default: 4256 assert(false, "unknown GCAllocPurpose"); 4257 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4258 break; 4259 } 4260 4261 // Prevent humongous PLAB sizes for two reasons: 4262 // * PLABs are allocated using a similar paths as oops, but should 4263 // never be in a humongous region 4264 // * Allowing humongous PLABs needlessly churns the region free lists 4265 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4266 } 4267 4268 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4269 _drain_in_progress = false; 4270 set_evac_failure_closure(cl); 4271 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4272 } 4273 4274 void G1CollectedHeap::finalize_for_evac_failure() { 4275 assert(_evac_failure_scan_stack != NULL && 4276 _evac_failure_scan_stack->length() == 0, 4277 "Postcondition"); 4278 assert(!_drain_in_progress, "Postcondition"); 4279 delete _evac_failure_scan_stack; 4280 _evac_failure_scan_stack = NULL; 4281 } 4282 4283 void G1CollectedHeap::remove_self_forwarding_pointers() { 4284 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4285 4286 double remove_self_forwards_start = os::elapsedTime(); 4287 4288 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4289 4290 if (G1CollectedHeap::use_parallel_gc_threads()) { 4291 set_par_threads(); 4292 workers()->run_task(&rsfp_task); 4293 set_par_threads(0); 4294 } else { 4295 rsfp_task.work(0); 4296 } 4297 4298 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); 4299 4300 // Reset the claim values in the regions in the collection set. 4301 reset_cset_heap_region_claim_values(); 4302 4303 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4304 4305 // Now restore saved marks, if any. 4306 assert(_objs_with_preserved_marks.size() == 4307 _preserved_marks_of_objs.size(), "Both or none."); 4308 while (!_objs_with_preserved_marks.is_empty()) { 4309 oop obj = _objs_with_preserved_marks.pop(); 4310 markOop m = _preserved_marks_of_objs.pop(); 4311 obj->set_mark(m); 4312 } 4313 _objs_with_preserved_marks.clear(true); 4314 _preserved_marks_of_objs.clear(true); 4315 4316 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4317 } 4318 4319 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4320 _evac_failure_scan_stack->push(obj); 4321 } 4322 4323 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4324 assert(_evac_failure_scan_stack != NULL, "precondition"); 4325 4326 while (_evac_failure_scan_stack->length() > 0) { 4327 oop obj = _evac_failure_scan_stack->pop(); 4328 _evac_failure_closure->set_region(heap_region_containing(obj)); 4329 obj->oop_iterate_backwards(_evac_failure_closure); 4330 } 4331 } 4332 4333 oop 4334 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, 4335 oop old) { 4336 assert(obj_in_cs(old), 4337 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4338 (HeapWord*) old)); 4339 markOop m = old->mark(); 4340 oop forward_ptr = old->forward_to_atomic(old); 4341 if (forward_ptr == NULL) { 4342 // Forward-to-self succeeded. 4343 assert(_par_scan_state != NULL, "par scan state"); 4344 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4345 uint queue_num = _par_scan_state->queue_num(); 4346 4347 _evacuation_failed = true; 4348 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size()); 4349 if (_evac_failure_closure != cl) { 4350 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4351 assert(!_drain_in_progress, 4352 "Should only be true while someone holds the lock."); 4353 // Set the global evac-failure closure to the current thread's. 4354 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4355 set_evac_failure_closure(cl); 4356 // Now do the common part. 4357 handle_evacuation_failure_common(old, m); 4358 // Reset to NULL. 4359 set_evac_failure_closure(NULL); 4360 } else { 4361 // The lock is already held, and this is recursive. 4362 assert(_drain_in_progress, "This should only be the recursive case."); 4363 handle_evacuation_failure_common(old, m); 4364 } 4365 return old; 4366 } else { 4367 // Forward-to-self failed. Either someone else managed to allocate 4368 // space for this object (old != forward_ptr) or they beat us in 4369 // self-forwarding it (old == forward_ptr). 4370 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4371 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4372 "should not be in the CSet", 4373 (HeapWord*) old, (HeapWord*) forward_ptr)); 4374 return forward_ptr; 4375 } 4376 } 4377 4378 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4379 preserve_mark_if_necessary(old, m); 4380 4381 HeapRegion* r = heap_region_containing(old); 4382 if (!r->evacuation_failed()) { 4383 r->set_evacuation_failed(true); 4384 _hr_printer.evac_failure(r); 4385 } 4386 4387 push_on_evac_failure_scan_stack(old); 4388 4389 if (!_drain_in_progress) { 4390 // prevent recursion in copy_to_survivor_space() 4391 _drain_in_progress = true; 4392 drain_evac_failure_scan_stack(); 4393 _drain_in_progress = false; 4394 } 4395 } 4396 4397 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4398 assert(evacuation_failed(), "Oversaving!"); 4399 // We want to call the "for_promotion_failure" version only in the 4400 // case of a promotion failure. 4401 if (m->must_be_preserved_for_promotion_failure(obj)) { 4402 _objs_with_preserved_marks.push(obj); 4403 _preserved_marks_of_objs.push(m); 4404 } 4405 } 4406 4407 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4408 size_t word_size, 4409 AllocationContext_t context) { 4410 if (purpose == GCAllocForSurvived) { 4411 HeapWord* result = survivor_attempt_allocation(word_size, context); 4412 if (result != NULL) { 4413 return result; 4414 } else { 4415 // Let's try to allocate in the old gen in case we can fit the 4416 // object there. 4417 return old_attempt_allocation(word_size, context); 4418 } 4419 } else { 4420 assert(purpose == GCAllocForTenured, "sanity"); 4421 HeapWord* result = old_attempt_allocation(word_size, context); 4422 if (result != NULL) { 4423 return result; 4424 } else { 4425 // Let's try to allocate in the survivors in case we can fit the 4426 // object there. 4427 return survivor_attempt_allocation(word_size, context); 4428 } 4429 } 4430 4431 ShouldNotReachHere(); 4432 // Trying to keep some compilers happy. 4433 return NULL; 4434 } 4435 4436 void G1ParCopyHelper::mark_object(oop obj) { 4437 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet"); 4438 4439 // We know that the object is not moving so it's safe to read its size. 4440 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4441 } 4442 4443 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) { 4444 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4445 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4446 assert(from_obj != to_obj, "should not be self-forwarded"); 4447 4448 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet"); 4449 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet"); 4450 4451 // The object might be in the process of being copied by another 4452 // worker so we cannot trust that its to-space image is 4453 // well-formed. So we have to read its size from its from-space 4454 // image which we know should not be changing. 4455 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4456 } 4457 4458 template <class T> 4459 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4460 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4461 _scanned_klass->record_modified_oops(); 4462 } 4463 } 4464 4465 template <G1Barrier barrier, G1Mark do_mark_object> 4466 template <class T> 4467 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) { 4468 T heap_oop = oopDesc::load_heap_oop(p); 4469 4470 if (oopDesc::is_null(heap_oop)) { 4471 return; 4472 } 4473 4474 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 4475 4476 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4477 4478 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj); 4479 4480 if (state == G1CollectedHeap::InCSet) { 4481 oop forwardee; 4482 if (obj->is_forwarded()) { 4483 forwardee = obj->forwardee(); 4484 } else { 4485 forwardee = _par_scan_state->copy_to_survivor_space(obj); 4486 } 4487 assert(forwardee != NULL, "forwardee should not be NULL"); 4488 oopDesc::encode_store_heap_oop(p, forwardee); 4489 if (do_mark_object != G1MarkNone && forwardee != obj) { 4490 // If the object is self-forwarded we don't need to explicitly 4491 // mark it, the evacuation failure protocol will do so. 4492 mark_forwarded_object(obj, forwardee); 4493 } 4494 4495 if (barrier == G1BarrierKlass) { 4496 do_klass_barrier(p, forwardee); 4497 } 4498 } else { 4499 if (state == G1CollectedHeap::IsHumongous) { 4500 _g1->set_humongous_is_live(obj); 4501 } 4502 // The object is not in collection set. If we're a root scanning 4503 // closure during an initial mark pause then attempt to mark the object. 4504 if (do_mark_object == G1MarkFromRoot) { 4505 mark_object(obj); 4506 } 4507 } 4508 4509 if (barrier == G1BarrierEvac) { 4510 _par_scan_state->update_rs(_from, p, _worker_id); 4511 } 4512 } 4513 4514 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p); 4515 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p); 4516 4517 class G1ParEvacuateFollowersClosure : public VoidClosure { 4518 protected: 4519 G1CollectedHeap* _g1h; 4520 G1ParScanThreadState* _par_scan_state; 4521 RefToScanQueueSet* _queues; 4522 ParallelTaskTerminator* _terminator; 4523 4524 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4525 RefToScanQueueSet* queues() { return _queues; } 4526 ParallelTaskTerminator* terminator() { return _terminator; } 4527 4528 public: 4529 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4530 G1ParScanThreadState* par_scan_state, 4531 RefToScanQueueSet* queues, 4532 ParallelTaskTerminator* terminator) 4533 : _g1h(g1h), _par_scan_state(par_scan_state), 4534 _queues(queues), _terminator(terminator) {} 4535 4536 void do_void(); 4537 4538 private: 4539 inline bool offer_termination(); 4540 }; 4541 4542 bool G1ParEvacuateFollowersClosure::offer_termination() { 4543 G1ParScanThreadState* const pss = par_scan_state(); 4544 pss->start_term_time(); 4545 const bool res = terminator()->offer_termination(); 4546 pss->end_term_time(); 4547 return res; 4548 } 4549 4550 void G1ParEvacuateFollowersClosure::do_void() { 4551 G1ParScanThreadState* const pss = par_scan_state(); 4552 pss->trim_queue(); 4553 do { 4554 pss->steal_and_trim_queue(queues()); 4555 } while (!offer_termination()); 4556 } 4557 4558 class G1KlassScanClosure : public KlassClosure { 4559 G1ParCopyHelper* _closure; 4560 bool _process_only_dirty; 4561 int _count; 4562 public: 4563 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4564 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4565 void do_klass(Klass* klass) { 4566 // If the klass has not been dirtied we know that there's 4567 // no references into the young gen and we can skip it. 4568 if (!_process_only_dirty || klass->has_modified_oops()) { 4569 // Clean the klass since we're going to scavenge all the metadata. 4570 klass->clear_modified_oops(); 4571 4572 // Tell the closure that this klass is the Klass to scavenge 4573 // and is the one to dirty if oops are left pointing into the young gen. 4574 _closure->set_scanned_klass(klass); 4575 4576 klass->oops_do(_closure); 4577 4578 _closure->set_scanned_klass(NULL); 4579 } 4580 _count++; 4581 } 4582 }; 4583 4584 class G1CodeBlobClosure : public CodeBlobClosure { 4585 class HeapRegionGatheringOopClosure : public OopClosure { 4586 G1CollectedHeap* _g1h; 4587 OopClosure* _work; 4588 nmethod* _nm; 4589 4590 template <typename T> 4591 void do_oop_work(T* p) { 4592 _work->do_oop(p); 4593 T oop_or_narrowoop = oopDesc::load_heap_oop(p); 4594 if (!oopDesc::is_null(oop_or_narrowoop)) { 4595 oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop); 4596 HeapRegion* hr = _g1h->heap_region_containing_raw(o); 4597 assert(!_g1h->obj_in_cs(o) || hr->rem_set()->strong_code_roots_list_contains(_nm), "if o still in CS then evacuation failed and nm must already be in the remset"); 4598 hr->add_strong_code_root(_nm); 4599 } 4600 } 4601 4602 public: 4603 HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {} 4604 4605 void do_oop(oop* o) { 4606 do_oop_work(o); 4607 } 4608 4609 void do_oop(narrowOop* o) { 4610 do_oop_work(o); 4611 } 4612 4613 void set_nm(nmethod* nm) { 4614 _nm = nm; 4615 } 4616 }; 4617 4618 HeapRegionGatheringOopClosure _oc; 4619 public: 4620 G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {} 4621 4622 void do_code_blob(CodeBlob* cb) { 4623 nmethod* nm = cb->as_nmethod_or_null(); 4624 if (nm != NULL) { 4625 if (!nm->test_set_oops_do_mark()) { 4626 _oc.set_nm(nm); 4627 nm->oops_do(&_oc); 4628 nm->fix_oop_relocations(); 4629 } 4630 } 4631 } 4632 }; 4633 4634 class G1ParTask : public AbstractGangTask { 4635 protected: 4636 G1CollectedHeap* _g1h; 4637 RefToScanQueueSet *_queues; 4638 ParallelTaskTerminator _terminator; 4639 uint _n_workers; 4640 4641 Mutex _stats_lock; 4642 Mutex* stats_lock() { return &_stats_lock; } 4643 4644 public: 4645 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues) 4646 : AbstractGangTask("G1 collection"), 4647 _g1h(g1h), 4648 _queues(task_queues), 4649 _terminator(0, _queues), 4650 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4651 {} 4652 4653 RefToScanQueueSet* queues() { return _queues; } 4654 4655 RefToScanQueue *work_queue(int i) { 4656 return queues()->queue(i); 4657 } 4658 4659 ParallelTaskTerminator* terminator() { return &_terminator; } 4660 4661 virtual void set_for_termination(int active_workers) { 4662 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4663 // in the young space (_par_seq_tasks) in the G1 heap 4664 // for SequentialSubTasksDone. 4665 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4666 // both of which need setting by set_n_termination(). 4667 _g1h->SharedHeap::set_n_termination(active_workers); 4668 _g1h->set_n_termination(active_workers); 4669 terminator()->reset_for_reuse(active_workers); 4670 _n_workers = active_workers; 4671 } 4672 4673 // Helps out with CLD processing. 4674 // 4675 // During InitialMark we need to: 4676 // 1) Scavenge all CLDs for the young GC. 4677 // 2) Mark all objects directly reachable from strong CLDs. 4678 template <G1Mark do_mark_object> 4679 class G1CLDClosure : public CLDClosure { 4680 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure; 4681 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure; 4682 G1KlassScanClosure _klass_in_cld_closure; 4683 bool _claim; 4684 4685 public: 4686 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure, 4687 bool only_young, bool claim) 4688 : _oop_closure(oop_closure), 4689 _oop_in_klass_closure(oop_closure->g1(), 4690 oop_closure->pss(), 4691 oop_closure->rp()), 4692 _klass_in_cld_closure(&_oop_in_klass_closure, only_young), 4693 _claim(claim) { 4694 4695 } 4696 4697 void do_cld(ClassLoaderData* cld) { 4698 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim); 4699 } 4700 }; 4701 4702 void work(uint worker_id) { 4703 if (worker_id >= _n_workers) return; // no work needed this round 4704 4705 double start_time_ms = os::elapsedTime() * 1000.0; 4706 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 4707 4708 { 4709 ResourceMark rm; 4710 HandleMark hm; 4711 4712 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4713 4714 G1ParScanThreadState pss(_g1h, worker_id, rp); 4715 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4716 4717 pss.set_evac_failure_closure(&evac_failure_cl); 4718 4719 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4720 4721 // Non-IM young GC. 4722 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp); 4723 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl, 4724 only_young, // Only process dirty klasses. 4725 false); // No need to claim CLDs. 4726 // IM young GC. 4727 // Strong roots closures. 4728 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp); 4729 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl, 4730 false, // Process all klasses. 4731 true); // Need to claim CLDs. 4732 // Weak roots closures. 4733 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp); 4734 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl, 4735 false, // Process all klasses. 4736 true); // Need to claim CLDs. 4737 4738 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl); 4739 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl); 4740 // IM Weak code roots are handled later. 4741 4742 OopClosure* strong_root_cl; 4743 OopClosure* weak_root_cl; 4744 CLDClosure* strong_cld_cl; 4745 CLDClosure* weak_cld_cl; 4746 CodeBlobClosure* strong_code_cl; 4747 4748 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4749 // We also need to mark copied objects. 4750 strong_root_cl = &scan_mark_root_cl; 4751 strong_cld_cl = &scan_mark_cld_cl; 4752 strong_code_cl = &scan_mark_code_cl; 4753 if (ClassUnloadingWithConcurrentMark) { 4754 weak_root_cl = &scan_mark_weak_root_cl; 4755 weak_cld_cl = &scan_mark_weak_cld_cl; 4756 } else { 4757 weak_root_cl = &scan_mark_root_cl; 4758 weak_cld_cl = &scan_mark_cld_cl; 4759 } 4760 } else { 4761 strong_root_cl = &scan_only_root_cl; 4762 weak_root_cl = &scan_only_root_cl; 4763 strong_cld_cl = &scan_only_cld_cl; 4764 weak_cld_cl = &scan_only_cld_cl; 4765 strong_code_cl = &scan_only_code_cl; 4766 } 4767 4768 4769 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4770 4771 pss.start_strong_roots(); 4772 _g1h->g1_process_roots(strong_root_cl, 4773 weak_root_cl, 4774 &push_heap_rs_cl, 4775 strong_cld_cl, 4776 weak_cld_cl, 4777 strong_code_cl, 4778 worker_id); 4779 4780 pss.end_strong_roots(); 4781 4782 { 4783 double start = os::elapsedTime(); 4784 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4785 evac.do_void(); 4786 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4787 double term_ms = pss.term_time()*1000.0; 4788 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 4789 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 4790 } 4791 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4792 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4793 4794 if (ParallelGCVerbose) { 4795 MutexLocker x(stats_lock()); 4796 pss.print_termination_stats(worker_id); 4797 } 4798 4799 assert(pss.queue_is_empty(), "should be empty"); 4800 4801 // Close the inner scope so that the ResourceMark and HandleMark 4802 // destructors are executed here and are included as part of the 4803 // "GC Worker Time". 4804 } 4805 4806 double end_time_ms = os::elapsedTime() * 1000.0; 4807 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 4808 } 4809 }; 4810 4811 // *** Common G1 Evacuation Stuff 4812 4813 // This method is run in a GC worker. 4814 4815 void 4816 G1CollectedHeap:: 4817 g1_process_roots(OopClosure* scan_non_heap_roots, 4818 OopClosure* scan_non_heap_weak_roots, 4819 OopsInHeapRegionClosure* scan_rs, 4820 CLDClosure* scan_strong_clds, 4821 CLDClosure* scan_weak_clds, 4822 CodeBlobClosure* scan_strong_code, 4823 uint worker_i) { 4824 4825 // First scan the shared roots. 4826 double ext_roots_start = os::elapsedTime(); 4827 double closure_app_time_sec = 0.0; 4828 4829 bool during_im = _g1h->g1_policy()->during_initial_mark_pause(); 4830 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark; 4831 4832 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 4833 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots); 4834 4835 process_roots(false, // no scoping; this is parallel code 4836 SharedHeap::SO_None, 4837 &buf_scan_non_heap_roots, 4838 &buf_scan_non_heap_weak_roots, 4839 scan_strong_clds, 4840 // Unloading Initial Marks handle the weak CLDs separately. 4841 (trace_metadata ? NULL : scan_weak_clds), 4842 scan_strong_code); 4843 4844 // Now the CM ref_processor roots. 4845 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 4846 // We need to treat the discovered reference lists of the 4847 // concurrent mark ref processor as roots and keep entries 4848 // (which are added by the marking threads) on them live 4849 // until they can be processed at the end of marking. 4850 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 4851 } 4852 4853 if (trace_metadata) { 4854 // Barrier to make sure all workers passed 4855 // the strong CLD and strong nmethods phases. 4856 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads()); 4857 4858 // Now take the complement of the strong CLDs. 4859 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds); 4860 } 4861 4862 // Finish up any enqueued closure apps (attributed as object copy time). 4863 buf_scan_non_heap_roots.done(); 4864 buf_scan_non_heap_weak_roots.done(); 4865 4866 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds() 4867 + buf_scan_non_heap_weak_roots.closure_app_seconds(); 4868 4869 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 4870 4871 double ext_root_time_ms = 4872 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 4873 4874 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 4875 4876 // During conc marking we have to filter the per-thread SATB buffers 4877 // to make sure we remove any oops into the CSet (which will show up 4878 // as implicitly live). 4879 double satb_filtering_ms = 0.0; 4880 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 4881 if (mark_in_progress()) { 4882 double satb_filter_start = os::elapsedTime(); 4883 4884 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 4885 4886 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 4887 } 4888 } 4889 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 4890 4891 // Now scan the complement of the collection set. 4892 G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots); 4893 4894 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i); 4895 4896 _process_strong_tasks->all_tasks_completed(); 4897 } 4898 4899 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4900 private: 4901 BoolObjectClosure* _is_alive; 4902 int _initial_string_table_size; 4903 int _initial_symbol_table_size; 4904 4905 bool _process_strings; 4906 int _strings_processed; 4907 int _strings_removed; 4908 4909 bool _process_symbols; 4910 int _symbols_processed; 4911 int _symbols_removed; 4912 4913 bool _do_in_parallel; 4914 public: 4915 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4916 AbstractGangTask("String/Symbol Unlinking"), 4917 _is_alive(is_alive), 4918 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()), 4919 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4920 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4921 4922 _initial_string_table_size = StringTable::the_table()->table_size(); 4923 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4924 if (process_strings) { 4925 StringTable::clear_parallel_claimed_index(); 4926 } 4927 if (process_symbols) { 4928 SymbolTable::clear_parallel_claimed_index(); 4929 } 4930 } 4931 4932 ~G1StringSymbolTableUnlinkTask() { 4933 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4934 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT, 4935 StringTable::parallel_claimed_index(), _initial_string_table_size)); 4936 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4937 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT, 4938 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size)); 4939 4940 if (G1TraceStringSymbolTableScrubbing) { 4941 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4942 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, " 4943 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed", 4944 strings_processed(), strings_removed(), 4945 symbols_processed(), symbols_removed()); 4946 } 4947 } 4948 4949 void work(uint worker_id) { 4950 if (_do_in_parallel) { 4951 int strings_processed = 0; 4952 int strings_removed = 0; 4953 int symbols_processed = 0; 4954 int symbols_removed = 0; 4955 if (_process_strings) { 4956 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4957 Atomic::add(strings_processed, &_strings_processed); 4958 Atomic::add(strings_removed, &_strings_removed); 4959 } 4960 if (_process_symbols) { 4961 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4962 Atomic::add(symbols_processed, &_symbols_processed); 4963 Atomic::add(symbols_removed, &_symbols_removed); 4964 } 4965 } else { 4966 if (_process_strings) { 4967 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed); 4968 } 4969 if (_process_symbols) { 4970 SymbolTable::unlink(&_symbols_processed, &_symbols_removed); 4971 } 4972 } 4973 } 4974 4975 size_t strings_processed() const { return (size_t)_strings_processed; } 4976 size_t strings_removed() const { return (size_t)_strings_removed; } 4977 4978 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4979 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4980 }; 4981 4982 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4983 private: 4984 static Monitor* _lock; 4985 4986 BoolObjectClosure* const _is_alive; 4987 const bool _unloading_occurred; 4988 const uint _num_workers; 4989 4990 // Variables used to claim nmethods. 4991 nmethod* _first_nmethod; 4992 volatile nmethod* _claimed_nmethod; 4993 4994 // The list of nmethods that need to be processed by the second pass. 4995 volatile nmethod* _postponed_list; 4996 volatile uint _num_entered_barrier; 4997 4998 public: 4999 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 5000 _is_alive(is_alive), 5001 _unloading_occurred(unloading_occurred), 5002 _num_workers(num_workers), 5003 _first_nmethod(NULL), 5004 _claimed_nmethod(NULL), 5005 _postponed_list(NULL), 5006 _num_entered_barrier(0) 5007 { 5008 nmethod::increase_unloading_clock(); 5009 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first()); 5010 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 5011 } 5012 5013 ~G1CodeCacheUnloadingTask() { 5014 CodeCache::verify_clean_inline_caches(); 5015 5016 CodeCache::set_needs_cache_clean(false); 5017 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 5018 5019 CodeCache::verify_icholder_relocations(); 5020 } 5021 5022 private: 5023 void add_to_postponed_list(nmethod* nm) { 5024 nmethod* old; 5025 do { 5026 old = (nmethod*)_postponed_list; 5027 nm->set_unloading_next(old); 5028 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 5029 } 5030 5031 void clean_nmethod(nmethod* nm) { 5032 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 5033 5034 if (postponed) { 5035 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 5036 add_to_postponed_list(nm); 5037 } 5038 5039 // Mark that this thread has been cleaned/unloaded. 5040 // After this call, it will be safe to ask if this nmethod was unloaded or not. 5041 nm->set_unloading_clock(nmethod::global_unloading_clock()); 5042 } 5043 5044 void clean_nmethod_postponed(nmethod* nm) { 5045 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 5046 } 5047 5048 static const int MaxClaimNmethods = 16; 5049 5050 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 5051 nmethod* first; 5052 nmethod* last; 5053 5054 do { 5055 *num_claimed_nmethods = 0; 5056 5057 first = last = (nmethod*)_claimed_nmethod; 5058 5059 if (first != NULL) { 5060 for (int i = 0; i < MaxClaimNmethods; i++) { 5061 last = CodeCache::alive_nmethod(CodeCache::next(last)); 5062 5063 if (last == NULL) { 5064 break; 5065 } 5066 5067 claimed_nmethods[i] = last; 5068 (*num_claimed_nmethods)++; 5069 } 5070 } 5071 5072 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first); 5073 } 5074 5075 nmethod* claim_postponed_nmethod() { 5076 nmethod* claim; 5077 nmethod* next; 5078 5079 do { 5080 claim = (nmethod*)_postponed_list; 5081 if (claim == NULL) { 5082 return NULL; 5083 } 5084 5085 next = claim->unloading_next(); 5086 5087 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 5088 5089 return claim; 5090 } 5091 5092 public: 5093 // Mark that we're done with the first pass of nmethod cleaning. 5094 void barrier_mark(uint worker_id) { 5095 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 5096 _num_entered_barrier++; 5097 if (_num_entered_barrier == _num_workers) { 5098 ml.notify_all(); 5099 } 5100 } 5101 5102 // See if we have to wait for the other workers to 5103 // finish their first-pass nmethod cleaning work. 5104 void barrier_wait(uint worker_id) { 5105 if (_num_entered_barrier < _num_workers) { 5106 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 5107 while (_num_entered_barrier < _num_workers) { 5108 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 5109 } 5110 } 5111 } 5112 5113 // Cleaning and unloading of nmethods. Some work has to be postponed 5114 // to the second pass, when we know which nmethods survive. 5115 void work_first_pass(uint worker_id) { 5116 // The first nmethods is claimed by the first worker. 5117 if (worker_id == 0 && _first_nmethod != NULL) { 5118 clean_nmethod(_first_nmethod); 5119 _first_nmethod = NULL; 5120 } 5121 5122 int num_claimed_nmethods; 5123 nmethod* claimed_nmethods[MaxClaimNmethods]; 5124 5125 while (true) { 5126 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 5127 5128 if (num_claimed_nmethods == 0) { 5129 break; 5130 } 5131 5132 for (int i = 0; i < num_claimed_nmethods; i++) { 5133 clean_nmethod(claimed_nmethods[i]); 5134 } 5135 } 5136 5137 // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark. 5138 // Need to retire the buffers now that this thread has stopped cleaning nmethods. 5139 MetadataOnStackMark::retire_buffer_for_thread(Thread::current()); 5140 } 5141 5142 void work_second_pass(uint worker_id) { 5143 nmethod* nm; 5144 // Take care of postponed nmethods. 5145 while ((nm = claim_postponed_nmethod()) != NULL) { 5146 clean_nmethod_postponed(nm); 5147 } 5148 } 5149 }; 5150 5151 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock"); 5152 5153 class G1KlassCleaningTask : public StackObj { 5154 BoolObjectClosure* _is_alive; 5155 volatile jint _clean_klass_tree_claimed; 5156 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 5157 5158 public: 5159 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 5160 _is_alive(is_alive), 5161 _clean_klass_tree_claimed(0), 5162 _klass_iterator() { 5163 } 5164 5165 private: 5166 bool claim_clean_klass_tree_task() { 5167 if (_clean_klass_tree_claimed) { 5168 return false; 5169 } 5170 5171 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 5172 } 5173 5174 InstanceKlass* claim_next_klass() { 5175 Klass* klass; 5176 do { 5177 klass =_klass_iterator.next_klass(); 5178 } while (klass != NULL && !klass->oop_is_instance()); 5179 5180 return (InstanceKlass*)klass; 5181 } 5182 5183 public: 5184 5185 void clean_klass(InstanceKlass* ik) { 5186 ik->clean_implementors_list(_is_alive); 5187 ik->clean_method_data(_is_alive); 5188 5189 // G1 specific cleanup work that has 5190 // been moved here to be done in parallel. 5191 ik->clean_dependent_nmethods(); 5192 if (JvmtiExport::has_redefined_a_class()) { 5193 InstanceKlass::purge_previous_versions(ik); 5194 } 5195 } 5196 5197 void work() { 5198 ResourceMark rm; 5199 5200 // One worker will clean the subklass/sibling klass tree. 5201 if (claim_clean_klass_tree_task()) { 5202 Klass::clean_subklass_tree(_is_alive); 5203 } 5204 5205 // All workers will help cleaning the classes, 5206 InstanceKlass* klass; 5207 while ((klass = claim_next_klass()) != NULL) { 5208 clean_klass(klass); 5209 } 5210 } 5211 }; 5212 5213 // To minimize the remark pause times, the tasks below are done in parallel. 5214 class G1ParallelCleaningTask : public AbstractGangTask { 5215 private: 5216 G1StringSymbolTableUnlinkTask _string_symbol_task; 5217 G1CodeCacheUnloadingTask _code_cache_task; 5218 G1KlassCleaningTask _klass_cleaning_task; 5219 5220 public: 5221 // The constructor is run in the VMThread. 5222 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 5223 AbstractGangTask("Parallel Cleaning"), 5224 _string_symbol_task(is_alive, process_strings, process_symbols), 5225 _code_cache_task(num_workers, is_alive, unloading_occurred), 5226 _klass_cleaning_task(is_alive) { 5227 } 5228 5229 void pre_work_verification() { 5230 // The VM Thread will have registered Metadata during the single-threaded phase of MetadataStackOnMark. 5231 assert(Thread::current()->is_VM_thread() 5232 || !MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty"); 5233 } 5234 5235 void post_work_verification() { 5236 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty"); 5237 } 5238 5239 // The parallel work done by all worker threads. 5240 void work(uint worker_id) { 5241 pre_work_verification(); 5242 5243 // Do first pass of code cache cleaning. 5244 _code_cache_task.work_first_pass(worker_id); 5245 5246 // Let the threads mark that the first pass is done. 5247 _code_cache_task.barrier_mark(worker_id); 5248 5249 // Clean the Strings and Symbols. 5250 _string_symbol_task.work(worker_id); 5251 5252 // Wait for all workers to finish the first code cache cleaning pass. 5253 _code_cache_task.barrier_wait(worker_id); 5254 5255 // Do the second code cache cleaning work, which realize on 5256 // the liveness information gathered during the first pass. 5257 _code_cache_task.work_second_pass(worker_id); 5258 5259 // Clean all klasses that were not unloaded. 5260 _klass_cleaning_task.work(); 5261 5262 post_work_verification(); 5263 } 5264 }; 5265 5266 5267 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 5268 bool process_strings, 5269 bool process_symbols, 5270 bool class_unloading_occurred) { 5271 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5272 workers()->active_workers() : 1); 5273 5274 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 5275 n_workers, class_unloading_occurred); 5276 if (G1CollectedHeap::use_parallel_gc_threads()) { 5277 set_par_threads(n_workers); 5278 workers()->run_task(&g1_unlink_task); 5279 set_par_threads(0); 5280 } else { 5281 g1_unlink_task.work(0); 5282 } 5283 } 5284 5285 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 5286 bool process_strings, bool process_symbols) { 5287 { 5288 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5289 _g1h->workers()->active_workers() : 1); 5290 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 5291 if (G1CollectedHeap::use_parallel_gc_threads()) { 5292 set_par_threads(n_workers); 5293 workers()->run_task(&g1_unlink_task); 5294 set_par_threads(0); 5295 } else { 5296 g1_unlink_task.work(0); 5297 } 5298 } 5299 5300 if (G1StringDedup::is_enabled()) { 5301 G1StringDedup::unlink(is_alive); 5302 } 5303 } 5304 5305 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 5306 private: 5307 DirtyCardQueueSet* _queue; 5308 public: 5309 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 5310 5311 virtual void work(uint worker_id) { 5312 double start_time = os::elapsedTime(); 5313 5314 RedirtyLoggedCardTableEntryClosure cl; 5315 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) { 5316 _queue->par_apply_closure_to_all_completed_buffers(&cl); 5317 } else { 5318 _queue->apply_closure_to_all_completed_buffers(&cl); 5319 } 5320 5321 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 5322 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0); 5323 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed()); 5324 } 5325 }; 5326 5327 void G1CollectedHeap::redirty_logged_cards() { 5328 double redirty_logged_cards_start = os::elapsedTime(); 5329 5330 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5331 _g1h->workers()->active_workers() : 1); 5332 5333 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 5334 dirty_card_queue_set().reset_for_par_iteration(); 5335 if (use_parallel_gc_threads()) { 5336 set_par_threads(n_workers); 5337 workers()->run_task(&redirty_task); 5338 set_par_threads(0); 5339 } else { 5340 redirty_task.work(0); 5341 } 5342 5343 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5344 dcq.merge_bufferlists(&dirty_card_queue_set()); 5345 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5346 5347 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 5348 } 5349 5350 // Weak Reference Processing support 5351 5352 // An always "is_alive" closure that is used to preserve referents. 5353 // If the object is non-null then it's alive. Used in the preservation 5354 // of referent objects that are pointed to by reference objects 5355 // discovered by the CM ref processor. 5356 class G1AlwaysAliveClosure: public BoolObjectClosure { 5357 G1CollectedHeap* _g1; 5358 public: 5359 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5360 bool do_object_b(oop p) { 5361 if (p != NULL) { 5362 return true; 5363 } 5364 return false; 5365 } 5366 }; 5367 5368 bool G1STWIsAliveClosure::do_object_b(oop p) { 5369 // An object is reachable if it is outside the collection set, 5370 // or is inside and copied. 5371 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5372 } 5373 5374 // Non Copying Keep Alive closure 5375 class G1KeepAliveClosure: public OopClosure { 5376 G1CollectedHeap* _g1; 5377 public: 5378 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5379 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5380 void do_oop(oop* p) { 5381 oop obj = *p; 5382 assert(obj != NULL, "the caller should have filtered out NULL values"); 5383 5384 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj); 5385 if (cset_state == G1CollectedHeap::InNeither) { 5386 return; 5387 } 5388 if (cset_state == G1CollectedHeap::InCSet) { 5389 assert( obj->is_forwarded(), "invariant" ); 5390 *p = obj->forwardee(); 5391 } else { 5392 assert(!obj->is_forwarded(), "invariant" ); 5393 assert(cset_state == G1CollectedHeap::IsHumongous, 5394 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state)); 5395 _g1->set_humongous_is_live(obj); 5396 } 5397 } 5398 }; 5399 5400 // Copying Keep Alive closure - can be called from both 5401 // serial and parallel code as long as different worker 5402 // threads utilize different G1ParScanThreadState instances 5403 // and different queues. 5404 5405 class G1CopyingKeepAliveClosure: public OopClosure { 5406 G1CollectedHeap* _g1h; 5407 OopClosure* _copy_non_heap_obj_cl; 5408 G1ParScanThreadState* _par_scan_state; 5409 5410 public: 5411 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5412 OopClosure* non_heap_obj_cl, 5413 G1ParScanThreadState* pss): 5414 _g1h(g1h), 5415 _copy_non_heap_obj_cl(non_heap_obj_cl), 5416 _par_scan_state(pss) 5417 {} 5418 5419 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5420 virtual void do_oop( oop* p) { do_oop_work(p); } 5421 5422 template <class T> void do_oop_work(T* p) { 5423 oop obj = oopDesc::load_decode_heap_oop(p); 5424 5425 if (_g1h->is_in_cset_or_humongous(obj)) { 5426 // If the referent object has been forwarded (either copied 5427 // to a new location or to itself in the event of an 5428 // evacuation failure) then we need to update the reference 5429 // field and, if both reference and referent are in the G1 5430 // heap, update the RSet for the referent. 5431 // 5432 // If the referent has not been forwarded then we have to keep 5433 // it alive by policy. Therefore we have copy the referent. 5434 // 5435 // If the reference field is in the G1 heap then we can push 5436 // on the PSS queue. When the queue is drained (after each 5437 // phase of reference processing) the object and it's followers 5438 // will be copied, the reference field set to point to the 5439 // new location, and the RSet updated. Otherwise we need to 5440 // use the the non-heap or metadata closures directly to copy 5441 // the referent object and update the pointer, while avoiding 5442 // updating the RSet. 5443 5444 if (_g1h->is_in_g1_reserved(p)) { 5445 _par_scan_state->push_on_queue(p); 5446 } else { 5447 assert(!Metaspace::contains((const void*)p), 5448 err_msg("Unexpectedly found a pointer from metadata: " 5449 PTR_FORMAT, p)); 5450 _copy_non_heap_obj_cl->do_oop(p); 5451 } 5452 } 5453 } 5454 }; 5455 5456 // Serial drain queue closure. Called as the 'complete_gc' 5457 // closure for each discovered list in some of the 5458 // reference processing phases. 5459 5460 class G1STWDrainQueueClosure: public VoidClosure { 5461 protected: 5462 G1CollectedHeap* _g1h; 5463 G1ParScanThreadState* _par_scan_state; 5464 5465 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5466 5467 public: 5468 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5469 _g1h(g1h), 5470 _par_scan_state(pss) 5471 { } 5472 5473 void do_void() { 5474 G1ParScanThreadState* const pss = par_scan_state(); 5475 pss->trim_queue(); 5476 } 5477 }; 5478 5479 // Parallel Reference Processing closures 5480 5481 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5482 // processing during G1 evacuation pauses. 5483 5484 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5485 private: 5486 G1CollectedHeap* _g1h; 5487 RefToScanQueueSet* _queues; 5488 FlexibleWorkGang* _workers; 5489 int _active_workers; 5490 5491 public: 5492 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5493 FlexibleWorkGang* workers, 5494 RefToScanQueueSet *task_queues, 5495 int n_workers) : 5496 _g1h(g1h), 5497 _queues(task_queues), 5498 _workers(workers), 5499 _active_workers(n_workers) 5500 { 5501 assert(n_workers > 0, "shouldn't call this otherwise"); 5502 } 5503 5504 // Executes the given task using concurrent marking worker threads. 5505 virtual void execute(ProcessTask& task); 5506 virtual void execute(EnqueueTask& task); 5507 }; 5508 5509 // Gang task for possibly parallel reference processing 5510 5511 class G1STWRefProcTaskProxy: public AbstractGangTask { 5512 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5513 ProcessTask& _proc_task; 5514 G1CollectedHeap* _g1h; 5515 RefToScanQueueSet *_task_queues; 5516 ParallelTaskTerminator* _terminator; 5517 5518 public: 5519 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5520 G1CollectedHeap* g1h, 5521 RefToScanQueueSet *task_queues, 5522 ParallelTaskTerminator* terminator) : 5523 AbstractGangTask("Process reference objects in parallel"), 5524 _proc_task(proc_task), 5525 _g1h(g1h), 5526 _task_queues(task_queues), 5527 _terminator(terminator) 5528 {} 5529 5530 virtual void work(uint worker_id) { 5531 // The reference processing task executed by a single worker. 5532 ResourceMark rm; 5533 HandleMark hm; 5534 5535 G1STWIsAliveClosure is_alive(_g1h); 5536 5537 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5538 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5539 5540 pss.set_evac_failure_closure(&evac_failure_cl); 5541 5542 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5543 5544 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5545 5546 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5547 5548 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5549 // We also need to mark copied objects. 5550 copy_non_heap_cl = ©_mark_non_heap_cl; 5551 } 5552 5553 // Keep alive closure. 5554 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5555 5556 // Complete GC closure 5557 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5558 5559 // Call the reference processing task's work routine. 5560 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5561 5562 // Note we cannot assert that the refs array is empty here as not all 5563 // of the processing tasks (specifically phase2 - pp2_work) execute 5564 // the complete_gc closure (which ordinarily would drain the queue) so 5565 // the queue may not be empty. 5566 } 5567 }; 5568 5569 // Driver routine for parallel reference processing. 5570 // Creates an instance of the ref processing gang 5571 // task and has the worker threads execute it. 5572 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5573 assert(_workers != NULL, "Need parallel worker threads."); 5574 5575 ParallelTaskTerminator terminator(_active_workers, _queues); 5576 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5577 5578 _g1h->set_par_threads(_active_workers); 5579 _workers->run_task(&proc_task_proxy); 5580 _g1h->set_par_threads(0); 5581 } 5582 5583 // Gang task for parallel reference enqueueing. 5584 5585 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5586 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5587 EnqueueTask& _enq_task; 5588 5589 public: 5590 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5591 AbstractGangTask("Enqueue reference objects in parallel"), 5592 _enq_task(enq_task) 5593 { } 5594 5595 virtual void work(uint worker_id) { 5596 _enq_task.work(worker_id); 5597 } 5598 }; 5599 5600 // Driver routine for parallel reference enqueueing. 5601 // Creates an instance of the ref enqueueing gang 5602 // task and has the worker threads execute it. 5603 5604 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5605 assert(_workers != NULL, "Need parallel worker threads."); 5606 5607 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5608 5609 _g1h->set_par_threads(_active_workers); 5610 _workers->run_task(&enq_task_proxy); 5611 _g1h->set_par_threads(0); 5612 } 5613 5614 // End of weak reference support closures 5615 5616 // Abstract task used to preserve (i.e. copy) any referent objects 5617 // that are in the collection set and are pointed to by reference 5618 // objects discovered by the CM ref processor. 5619 5620 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5621 protected: 5622 G1CollectedHeap* _g1h; 5623 RefToScanQueueSet *_queues; 5624 ParallelTaskTerminator _terminator; 5625 uint _n_workers; 5626 5627 public: 5628 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5629 AbstractGangTask("ParPreserveCMReferents"), 5630 _g1h(g1h), 5631 _queues(task_queues), 5632 _terminator(workers, _queues), 5633 _n_workers(workers) 5634 { } 5635 5636 void work(uint worker_id) { 5637 ResourceMark rm; 5638 HandleMark hm; 5639 5640 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5641 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5642 5643 pss.set_evac_failure_closure(&evac_failure_cl); 5644 5645 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5646 5647 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5648 5649 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5650 5651 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5652 5653 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5654 // We also need to mark copied objects. 5655 copy_non_heap_cl = ©_mark_non_heap_cl; 5656 } 5657 5658 // Is alive closure 5659 G1AlwaysAliveClosure always_alive(_g1h); 5660 5661 // Copying keep alive closure. Applied to referent objects that need 5662 // to be copied. 5663 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5664 5665 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5666 5667 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5668 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5669 5670 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5671 // So this must be true - but assert just in case someone decides to 5672 // change the worker ids. 5673 assert(0 <= worker_id && worker_id < limit, "sanity"); 5674 assert(!rp->discovery_is_atomic(), "check this code"); 5675 5676 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5677 for (uint idx = worker_id; idx < limit; idx += stride) { 5678 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5679 5680 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5681 while (iter.has_next()) { 5682 // Since discovery is not atomic for the CM ref processor, we 5683 // can see some null referent objects. 5684 iter.load_ptrs(DEBUG_ONLY(true)); 5685 oop ref = iter.obj(); 5686 5687 // This will filter nulls. 5688 if (iter.is_referent_alive()) { 5689 iter.make_referent_alive(); 5690 } 5691 iter.move_to_next(); 5692 } 5693 } 5694 5695 // Drain the queue - which may cause stealing 5696 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5697 drain_queue.do_void(); 5698 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5699 assert(pss.queue_is_empty(), "should be"); 5700 } 5701 }; 5702 5703 // Weak Reference processing during an evacuation pause (part 1). 5704 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5705 double ref_proc_start = os::elapsedTime(); 5706 5707 ReferenceProcessor* rp = _ref_processor_stw; 5708 assert(rp->discovery_enabled(), "should have been enabled"); 5709 5710 // Any reference objects, in the collection set, that were 'discovered' 5711 // by the CM ref processor should have already been copied (either by 5712 // applying the external root copy closure to the discovered lists, or 5713 // by following an RSet entry). 5714 // 5715 // But some of the referents, that are in the collection set, that these 5716 // reference objects point to may not have been copied: the STW ref 5717 // processor would have seen that the reference object had already 5718 // been 'discovered' and would have skipped discovering the reference, 5719 // but would not have treated the reference object as a regular oop. 5720 // As a result the copy closure would not have been applied to the 5721 // referent object. 5722 // 5723 // We need to explicitly copy these referent objects - the references 5724 // will be processed at the end of remarking. 5725 // 5726 // We also need to do this copying before we process the reference 5727 // objects discovered by the STW ref processor in case one of these 5728 // referents points to another object which is also referenced by an 5729 // object discovered by the STW ref processor. 5730 5731 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5732 no_of_gc_workers == workers()->active_workers(), 5733 "Need to reset active GC workers"); 5734 5735 set_par_threads(no_of_gc_workers); 5736 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5737 no_of_gc_workers, 5738 _task_queues); 5739 5740 if (G1CollectedHeap::use_parallel_gc_threads()) { 5741 workers()->run_task(&keep_cm_referents); 5742 } else { 5743 keep_cm_referents.work(0); 5744 } 5745 5746 set_par_threads(0); 5747 5748 // Closure to test whether a referent is alive. 5749 G1STWIsAliveClosure is_alive(this); 5750 5751 // Even when parallel reference processing is enabled, the processing 5752 // of JNI refs is serial and performed serially by the current thread 5753 // rather than by a worker. The following PSS will be used for processing 5754 // JNI refs. 5755 5756 // Use only a single queue for this PSS. 5757 G1ParScanThreadState pss(this, 0, NULL); 5758 5759 // We do not embed a reference processor in the copying/scanning 5760 // closures while we're actually processing the discovered 5761 // reference objects. 5762 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5763 5764 pss.set_evac_failure_closure(&evac_failure_cl); 5765 5766 assert(pss.queue_is_empty(), "pre-condition"); 5767 5768 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5769 5770 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5771 5772 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5773 5774 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5775 // We also need to mark copied objects. 5776 copy_non_heap_cl = ©_mark_non_heap_cl; 5777 } 5778 5779 // Keep alive closure. 5780 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss); 5781 5782 // Serial Complete GC closure 5783 G1STWDrainQueueClosure drain_queue(this, &pss); 5784 5785 // Setup the soft refs policy... 5786 rp->setup_policy(false); 5787 5788 ReferenceProcessorStats stats; 5789 if (!rp->processing_is_mt()) { 5790 // Serial reference processing... 5791 stats = rp->process_discovered_references(&is_alive, 5792 &keep_alive, 5793 &drain_queue, 5794 NULL, 5795 _gc_timer_stw, 5796 _gc_tracer_stw->gc_id()); 5797 } else { 5798 // Parallel reference processing 5799 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5800 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5801 5802 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5803 stats = rp->process_discovered_references(&is_alive, 5804 &keep_alive, 5805 &drain_queue, 5806 &par_task_executor, 5807 _gc_timer_stw, 5808 _gc_tracer_stw->gc_id()); 5809 } 5810 5811 _gc_tracer_stw->report_gc_reference_stats(stats); 5812 5813 // We have completed copying any necessary live referent objects. 5814 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5815 5816 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5817 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5818 } 5819 5820 // Weak Reference processing during an evacuation pause (part 2). 5821 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5822 double ref_enq_start = os::elapsedTime(); 5823 5824 ReferenceProcessor* rp = _ref_processor_stw; 5825 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5826 5827 // Now enqueue any remaining on the discovered lists on to 5828 // the pending list. 5829 if (!rp->processing_is_mt()) { 5830 // Serial reference processing... 5831 rp->enqueue_discovered_references(); 5832 } else { 5833 // Parallel reference enqueueing 5834 5835 assert(no_of_gc_workers == workers()->active_workers(), 5836 "Need to reset active workers"); 5837 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5838 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5839 5840 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5841 rp->enqueue_discovered_references(&par_task_executor); 5842 } 5843 5844 rp->verify_no_references_recorded(); 5845 assert(!rp->discovery_enabled(), "should have been disabled"); 5846 5847 // FIXME 5848 // CM's reference processing also cleans up the string and symbol tables. 5849 // Should we do that here also? We could, but it is a serial operation 5850 // and could significantly increase the pause time. 5851 5852 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5853 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5854 } 5855 5856 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) { 5857 _expand_heap_after_alloc_failure = true; 5858 _evacuation_failed = false; 5859 5860 // Should G1EvacuationFailureALot be in effect for this GC? 5861 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5862 5863 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5864 5865 // Disable the hot card cache. 5866 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5867 hot_card_cache->reset_hot_cache_claimed_index(); 5868 hot_card_cache->set_use_cache(false); 5869 5870 uint n_workers; 5871 if (G1CollectedHeap::use_parallel_gc_threads()) { 5872 n_workers = 5873 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5874 workers()->active_workers(), 5875 Threads::number_of_non_daemon_threads()); 5876 assert(UseDynamicNumberOfGCThreads || 5877 n_workers == workers()->total_workers(), 5878 "If not dynamic should be using all the workers"); 5879 workers()->set_active_workers(n_workers); 5880 set_par_threads(n_workers); 5881 } else { 5882 assert(n_par_threads() == 0, 5883 "Should be the original non-parallel value"); 5884 n_workers = 1; 5885 } 5886 5887 G1ParTask g1_par_task(this, _task_queues); 5888 5889 init_for_evac_failure(NULL); 5890 5891 rem_set()->prepare_for_younger_refs_iterate(true); 5892 5893 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5894 double start_par_time_sec = os::elapsedTime(); 5895 double end_par_time_sec; 5896 5897 { 5898 StrongRootsScope srs(this); 5899 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5900 if (g1_policy()->during_initial_mark_pause()) { 5901 ClassLoaderDataGraph::clear_claimed_marks(); 5902 } 5903 5904 if (G1CollectedHeap::use_parallel_gc_threads()) { 5905 // The individual threads will set their evac-failure closures. 5906 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5907 // These tasks use ShareHeap::_process_strong_tasks 5908 assert(UseDynamicNumberOfGCThreads || 5909 workers()->active_workers() == workers()->total_workers(), 5910 "If not dynamic should be using all the workers"); 5911 workers()->run_task(&g1_par_task); 5912 } else { 5913 g1_par_task.set_for_termination(n_workers); 5914 g1_par_task.work(0); 5915 } 5916 end_par_time_sec = os::elapsedTime(); 5917 5918 // Closing the inner scope will execute the destructor 5919 // for the StrongRootsScope object. We record the current 5920 // elapsed time before closing the scope so that time 5921 // taken for the SRS destructor is NOT included in the 5922 // reported parallel time. 5923 } 5924 5925 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5926 g1_policy()->phase_times()->record_par_time(par_time_ms); 5927 5928 double code_root_fixup_time_ms = 5929 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5930 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5931 5932 set_par_threads(0); 5933 5934 // Process any discovered reference objects - we have 5935 // to do this _before_ we retire the GC alloc regions 5936 // as we may have to copy some 'reachable' referent 5937 // objects (and their reachable sub-graphs) that were 5938 // not copied during the pause. 5939 process_discovered_references(n_workers); 5940 5941 // Weak root processing. 5942 { 5943 G1STWIsAliveClosure is_alive(this); 5944 G1KeepAliveClosure keep_alive(this); 5945 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5946 if (G1StringDedup::is_enabled()) { 5947 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive); 5948 } 5949 } 5950 5951 _allocator->release_gc_alloc_regions(n_workers, evacuation_info); 5952 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5953 5954 // Reset and re-enable the hot card cache. 5955 // Note the counts for the cards in the regions in the 5956 // collection set are reset when the collection set is freed. 5957 hot_card_cache->reset_hot_cache(); 5958 hot_card_cache->set_use_cache(true); 5959 5960 purge_code_root_memory(); 5961 5962 if (g1_policy()->during_initial_mark_pause()) { 5963 // Reset the claim values set during marking the strong code roots 5964 reset_heap_region_claim_values(); 5965 } 5966 5967 finalize_for_evac_failure(); 5968 5969 if (evacuation_failed()) { 5970 remove_self_forwarding_pointers(); 5971 5972 // Reset the G1EvacuationFailureALot counters and flags 5973 // Note: the values are reset only when an actual 5974 // evacuation failure occurs. 5975 NOT_PRODUCT(reset_evacuation_should_fail();) 5976 } 5977 5978 // Enqueue any remaining references remaining on the STW 5979 // reference processor's discovered lists. We need to do 5980 // this after the card table is cleaned (and verified) as 5981 // the act of enqueueing entries on to the pending list 5982 // will log these updates (and dirty their associated 5983 // cards). We need these updates logged to update any 5984 // RSets. 5985 enqueue_discovered_references(n_workers); 5986 5987 redirty_logged_cards(); 5988 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5989 } 5990 5991 void G1CollectedHeap::free_region(HeapRegion* hr, 5992 FreeRegionList* free_list, 5993 bool par, 5994 bool locked) { 5995 assert(!hr->is_free(), "the region should not be free"); 5996 assert(!hr->is_empty(), "the region should not be empty"); 5997 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5998 assert(free_list != NULL, "pre-condition"); 5999 6000 if (G1VerifyBitmaps) { 6001 MemRegion mr(hr->bottom(), hr->end()); 6002 concurrent_mark()->clearRangePrevBitmap(mr); 6003 } 6004 6005 // Clear the card counts for this region. 6006 // Note: we only need to do this if the region is not young 6007 // (since we don't refine cards in young regions). 6008 if (!hr->is_young()) { 6009 _cg1r->hot_card_cache()->reset_card_counts(hr); 6010 } 6011 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 6012 free_list->add_ordered(hr); 6013 } 6014 6015 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 6016 FreeRegionList* free_list, 6017 bool par) { 6018 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 6019 assert(free_list != NULL, "pre-condition"); 6020 6021 size_t hr_capacity = hr->capacity(); 6022 // We need to read this before we make the region non-humongous, 6023 // otherwise the information will be gone. 6024 uint last_index = hr->last_hc_index(); 6025 hr->clear_humongous(); 6026 free_region(hr, free_list, par); 6027 6028 uint i = hr->hrm_index() + 1; 6029 while (i < last_index) { 6030 HeapRegion* curr_hr = region_at(i); 6031 assert(curr_hr->continuesHumongous(), "invariant"); 6032 curr_hr->clear_humongous(); 6033 free_region(curr_hr, free_list, par); 6034 i += 1; 6035 } 6036 } 6037 6038 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 6039 const HeapRegionSetCount& humongous_regions_removed) { 6040 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 6041 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 6042 _old_set.bulk_remove(old_regions_removed); 6043 _humongous_set.bulk_remove(humongous_regions_removed); 6044 } 6045 6046 } 6047 6048 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 6049 assert(list != NULL, "list can't be null"); 6050 if (!list->is_empty()) { 6051 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 6052 _hrm.insert_list_into_free_list(list); 6053 } 6054 } 6055 6056 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 6057 _allocator->decrease_used(bytes); 6058 } 6059 6060 class G1ParCleanupCTTask : public AbstractGangTask { 6061 G1SATBCardTableModRefBS* _ct_bs; 6062 G1CollectedHeap* _g1h; 6063 HeapRegion* volatile _su_head; 6064 public: 6065 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 6066 G1CollectedHeap* g1h) : 6067 AbstractGangTask("G1 Par Cleanup CT Task"), 6068 _ct_bs(ct_bs), _g1h(g1h) { } 6069 6070 void work(uint worker_id) { 6071 HeapRegion* r; 6072 while (r = _g1h->pop_dirty_cards_region()) { 6073 clear_cards(r); 6074 } 6075 } 6076 6077 void clear_cards(HeapRegion* r) { 6078 // Cards of the survivors should have already been dirtied. 6079 if (!r->is_survivor()) { 6080 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 6081 } 6082 } 6083 }; 6084 6085 #ifndef PRODUCT 6086 class G1VerifyCardTableCleanup: public HeapRegionClosure { 6087 G1CollectedHeap* _g1h; 6088 G1SATBCardTableModRefBS* _ct_bs; 6089 public: 6090 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 6091 : _g1h(g1h), _ct_bs(ct_bs) { } 6092 virtual bool doHeapRegion(HeapRegion* r) { 6093 if (r->is_survivor()) { 6094 _g1h->verify_dirty_region(r); 6095 } else { 6096 _g1h->verify_not_dirty_region(r); 6097 } 6098 return false; 6099 } 6100 }; 6101 6102 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 6103 // All of the region should be clean. 6104 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6105 MemRegion mr(hr->bottom(), hr->end()); 6106 ct_bs->verify_not_dirty_region(mr); 6107 } 6108 6109 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 6110 // We cannot guarantee that [bottom(),end()] is dirty. Threads 6111 // dirty allocated blocks as they allocate them. The thread that 6112 // retires each region and replaces it with a new one will do a 6113 // maximal allocation to fill in [pre_dummy_top(),end()] but will 6114 // not dirty that area (one less thing to have to do while holding 6115 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 6116 // is dirty. 6117 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6118 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 6119 if (hr->is_young()) { 6120 ct_bs->verify_g1_young_region(mr); 6121 } else { 6122 ct_bs->verify_dirty_region(mr); 6123 } 6124 } 6125 6126 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 6127 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6128 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 6129 verify_dirty_region(hr); 6130 } 6131 } 6132 6133 void G1CollectedHeap::verify_dirty_young_regions() { 6134 verify_dirty_young_list(_young_list->first_region()); 6135 } 6136 6137 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 6138 HeapWord* tams, HeapWord* end) { 6139 guarantee(tams <= end, 6140 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end)); 6141 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 6142 if (result < end) { 6143 gclog_or_tty->cr(); 6144 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT, 6145 bitmap_name, result); 6146 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT, 6147 bitmap_name, tams, end); 6148 return false; 6149 } 6150 return true; 6151 } 6152 6153 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 6154 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 6155 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 6156 6157 HeapWord* bottom = hr->bottom(); 6158 HeapWord* ptams = hr->prev_top_at_mark_start(); 6159 HeapWord* ntams = hr->next_top_at_mark_start(); 6160 HeapWord* end = hr->end(); 6161 6162 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 6163 6164 bool res_n = true; 6165 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 6166 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 6167 // if we happen to be in that state. 6168 if (mark_in_progress() || !_cmThread->in_progress()) { 6169 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 6170 } 6171 if (!res_p || !res_n) { 6172 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT, 6173 HR_FORMAT_PARAMS(hr)); 6174 gclog_or_tty->print_cr("#### Caller: %s", caller); 6175 return false; 6176 } 6177 return true; 6178 } 6179 6180 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 6181 if (!G1VerifyBitmaps) return; 6182 6183 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 6184 } 6185 6186 class G1VerifyBitmapClosure : public HeapRegionClosure { 6187 private: 6188 const char* _caller; 6189 G1CollectedHeap* _g1h; 6190 bool _failures; 6191 6192 public: 6193 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 6194 _caller(caller), _g1h(g1h), _failures(false) { } 6195 6196 bool failures() { return _failures; } 6197 6198 virtual bool doHeapRegion(HeapRegion* hr) { 6199 if (hr->continuesHumongous()) return false; 6200 6201 bool result = _g1h->verify_bitmaps(_caller, hr); 6202 if (!result) { 6203 _failures = true; 6204 } 6205 return false; 6206 } 6207 }; 6208 6209 void G1CollectedHeap::check_bitmaps(const char* caller) { 6210 if (!G1VerifyBitmaps) return; 6211 6212 G1VerifyBitmapClosure cl(caller, this); 6213 heap_region_iterate(&cl); 6214 guarantee(!cl.failures(), "bitmap verification"); 6215 } 6216 #endif // PRODUCT 6217 6218 void G1CollectedHeap::cleanUpCardTable() { 6219 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6220 double start = os::elapsedTime(); 6221 6222 { 6223 // Iterate over the dirty cards region list. 6224 G1ParCleanupCTTask cleanup_task(ct_bs, this); 6225 6226 if (G1CollectedHeap::use_parallel_gc_threads()) { 6227 set_par_threads(); 6228 workers()->run_task(&cleanup_task); 6229 set_par_threads(0); 6230 } else { 6231 while (_dirty_cards_region_list) { 6232 HeapRegion* r = _dirty_cards_region_list; 6233 cleanup_task.clear_cards(r); 6234 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 6235 if (_dirty_cards_region_list == r) { 6236 // The last region. 6237 _dirty_cards_region_list = NULL; 6238 } 6239 r->set_next_dirty_cards_region(NULL); 6240 } 6241 } 6242 #ifndef PRODUCT 6243 if (G1VerifyCTCleanup || VerifyAfterGC) { 6244 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 6245 heap_region_iterate(&cleanup_verifier); 6246 } 6247 #endif 6248 } 6249 6250 double elapsed = os::elapsedTime() - start; 6251 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 6252 } 6253 6254 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) { 6255 size_t pre_used = 0; 6256 FreeRegionList local_free_list("Local List for CSet Freeing"); 6257 6258 double young_time_ms = 0.0; 6259 double non_young_time_ms = 0.0; 6260 6261 // Since the collection set is a superset of the the young list, 6262 // all we need to do to clear the young list is clear its 6263 // head and length, and unlink any young regions in the code below 6264 _young_list->clear(); 6265 6266 G1CollectorPolicy* policy = g1_policy(); 6267 6268 double start_sec = os::elapsedTime(); 6269 bool non_young = true; 6270 6271 HeapRegion* cur = cs_head; 6272 int age_bound = -1; 6273 size_t rs_lengths = 0; 6274 6275 while (cur != NULL) { 6276 assert(!is_on_master_free_list(cur), "sanity"); 6277 if (non_young) { 6278 if (cur->is_young()) { 6279 double end_sec = os::elapsedTime(); 6280 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6281 non_young_time_ms += elapsed_ms; 6282 6283 start_sec = os::elapsedTime(); 6284 non_young = false; 6285 } 6286 } else { 6287 if (!cur->is_young()) { 6288 double end_sec = os::elapsedTime(); 6289 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6290 young_time_ms += elapsed_ms; 6291 6292 start_sec = os::elapsedTime(); 6293 non_young = true; 6294 } 6295 } 6296 6297 rs_lengths += cur->rem_set()->occupied_locked(); 6298 6299 HeapRegion* next = cur->next_in_collection_set(); 6300 assert(cur->in_collection_set(), "bad CS"); 6301 cur->set_next_in_collection_set(NULL); 6302 cur->set_in_collection_set(false); 6303 6304 if (cur->is_young()) { 6305 int index = cur->young_index_in_cset(); 6306 assert(index != -1, "invariant"); 6307 assert((uint) index < policy->young_cset_region_length(), "invariant"); 6308 size_t words_survived = _surviving_young_words[index]; 6309 cur->record_surv_words_in_group(words_survived); 6310 6311 // At this point the we have 'popped' cur from the collection set 6312 // (linked via next_in_collection_set()) but it is still in the 6313 // young list (linked via next_young_region()). Clear the 6314 // _next_young_region field. 6315 cur->set_next_young_region(NULL); 6316 } else { 6317 int index = cur->young_index_in_cset(); 6318 assert(index == -1, "invariant"); 6319 } 6320 6321 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 6322 (!cur->is_young() && cur->young_index_in_cset() == -1), 6323 "invariant" ); 6324 6325 if (!cur->evacuation_failed()) { 6326 MemRegion used_mr = cur->used_region(); 6327 6328 // And the region is empty. 6329 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6330 pre_used += cur->used(); 6331 free_region(cur, &local_free_list, false /* par */, true /* locked */); 6332 } else { 6333 cur->uninstall_surv_rate_group(); 6334 if (cur->is_young()) { 6335 cur->set_young_index_in_cset(-1); 6336 } 6337 cur->set_evacuation_failed(false); 6338 // The region is now considered to be old. 6339 cur->set_old(); 6340 _old_set.add(cur); 6341 evacuation_info.increment_collectionset_used_after(cur->used()); 6342 } 6343 cur = next; 6344 } 6345 6346 evacuation_info.set_regions_freed(local_free_list.length()); 6347 policy->record_max_rs_lengths(rs_lengths); 6348 policy->cset_regions_freed(); 6349 6350 double end_sec = os::elapsedTime(); 6351 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6352 6353 if (non_young) { 6354 non_young_time_ms += elapsed_ms; 6355 } else { 6356 young_time_ms += elapsed_ms; 6357 } 6358 6359 prepend_to_freelist(&local_free_list); 6360 decrement_summary_bytes(pre_used); 6361 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6362 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6363 } 6364 6365 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 6366 private: 6367 FreeRegionList* _free_region_list; 6368 HeapRegionSet* _proxy_set; 6369 HeapRegionSetCount _humongous_regions_removed; 6370 size_t _freed_bytes; 6371 public: 6372 6373 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 6374 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 6375 } 6376 6377 virtual bool doHeapRegion(HeapRegion* r) { 6378 if (!r->startsHumongous()) { 6379 return false; 6380 } 6381 6382 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 6383 6384 oop obj = (oop)r->bottom(); 6385 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 6386 6387 // The following checks whether the humongous object is live are sufficient. 6388 // The main additional check (in addition to having a reference from the roots 6389 // or the young gen) is whether the humongous object has a remembered set entry. 6390 // 6391 // A humongous object cannot be live if there is no remembered set for it 6392 // because: 6393 // - there can be no references from within humongous starts regions referencing 6394 // the object because we never allocate other objects into them. 6395 // (I.e. there are no intra-region references that may be missed by the 6396 // remembered set) 6397 // - as soon there is a remembered set entry to the humongous starts region 6398 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 6399 // until the end of a concurrent mark. 6400 // 6401 // It is not required to check whether the object has been found dead by marking 6402 // or not, in fact it would prevent reclamation within a concurrent cycle, as 6403 // all objects allocated during that time are considered live. 6404 // SATB marking is even more conservative than the remembered set. 6405 // So if at this point in the collection there is no remembered set entry, 6406 // nobody has a reference to it. 6407 // At the start of collection we flush all refinement logs, and remembered sets 6408 // are completely up-to-date wrt to references to the humongous object. 6409 // 6410 // Other implementation considerations: 6411 // - never consider object arrays: while they are a valid target, they have not 6412 // been observed to be used as temporary objects. 6413 // - they would also pose considerable effort for cleaning up the the remembered 6414 // sets. 6415 // While this cleanup is not strictly necessary to be done (or done instantly), 6416 // given that their occurrence is very low, this saves us this additional 6417 // complexity. 6418 uint region_idx = r->hrm_index(); 6419 if (g1h->humongous_is_live(region_idx) || 6420 g1h->humongous_region_is_always_live(region_idx)) { 6421 6422 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) { 6423 gclog_or_tty->print_cr("Live humongous %d region %d size "SIZE_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d", 6424 r->isHumongous(), 6425 region_idx, 6426 obj->size()*HeapWordSize, 6427 r->rem_set()->occupied(), 6428 r->rem_set()->strong_code_roots_list_length(), 6429 next_bitmap->isMarked(r->bottom()), 6430 g1h->humongous_is_live(region_idx), 6431 obj->is_objArray() 6432 ); 6433 } 6434 6435 return false; 6436 } 6437 6438 guarantee(!obj->is_objArray(), 6439 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.", 6440 r->bottom())); 6441 6442 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) { 6443 gclog_or_tty->print_cr("Reclaim humongous region %d size "SIZE_FORMAT" start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other ", 6444 r->isHumongous(), 6445 obj->size()*HeapWordSize, 6446 r->bottom(), 6447 region_idx, 6448 r->region_num(), 6449 r->rem_set()->occupied(), 6450 r->rem_set()->strong_code_roots_list_length(), 6451 next_bitmap->isMarked(r->bottom()), 6452 g1h->humongous_is_live(region_idx), 6453 obj->is_objArray() 6454 ); 6455 } 6456 // Need to clear mark bit of the humongous object if already set. 6457 if (next_bitmap->isMarked(r->bottom())) { 6458 next_bitmap->clear(r->bottom()); 6459 } 6460 _freed_bytes += r->used(); 6461 r->set_containing_set(NULL); 6462 _humongous_regions_removed.increment(1u, r->capacity()); 6463 g1h->free_humongous_region(r, _free_region_list, false); 6464 6465 return false; 6466 } 6467 6468 HeapRegionSetCount& humongous_free_count() { 6469 return _humongous_regions_removed; 6470 } 6471 6472 size_t bytes_freed() const { 6473 return _freed_bytes; 6474 } 6475 6476 size_t humongous_reclaimed() const { 6477 return _humongous_regions_removed.length(); 6478 } 6479 }; 6480 6481 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 6482 assert_at_safepoint(true); 6483 6484 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || 6485 (!_has_humongous_reclaim_candidates && !G1TraceReclaimDeadHumongousObjectsAtYoungGC)) { 6486 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 6487 return; 6488 } 6489 6490 double start_time = os::elapsedTime(); 6491 6492 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 6493 6494 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 6495 heap_region_iterate(&cl); 6496 6497 HeapRegionSetCount empty_set; 6498 remove_from_old_sets(empty_set, cl.humongous_free_count()); 6499 6500 G1HRPrinter* hr_printer = _g1h->hr_printer(); 6501 if (hr_printer->is_active()) { 6502 FreeRegionListIterator iter(&local_cleanup_list); 6503 while (iter.more_available()) { 6504 HeapRegion* hr = iter.get_next(); 6505 hr_printer->cleanup(hr); 6506 } 6507 } 6508 6509 prepend_to_freelist(&local_cleanup_list); 6510 decrement_summary_bytes(cl.bytes_freed()); 6511 6512 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 6513 cl.humongous_reclaimed()); 6514 } 6515 6516 // This routine is similar to the above but does not record 6517 // any policy statistics or update free lists; we are abandoning 6518 // the current incremental collection set in preparation of a 6519 // full collection. After the full GC we will start to build up 6520 // the incremental collection set again. 6521 // This is only called when we're doing a full collection 6522 // and is immediately followed by the tearing down of the young list. 6523 6524 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6525 HeapRegion* cur = cs_head; 6526 6527 while (cur != NULL) { 6528 HeapRegion* next = cur->next_in_collection_set(); 6529 assert(cur->in_collection_set(), "bad CS"); 6530 cur->set_next_in_collection_set(NULL); 6531 cur->set_in_collection_set(false); 6532 cur->set_young_index_in_cset(-1); 6533 cur = next; 6534 } 6535 } 6536 6537 void G1CollectedHeap::set_free_regions_coming() { 6538 if (G1ConcRegionFreeingVerbose) { 6539 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6540 "setting free regions coming"); 6541 } 6542 6543 assert(!free_regions_coming(), "pre-condition"); 6544 _free_regions_coming = true; 6545 } 6546 6547 void G1CollectedHeap::reset_free_regions_coming() { 6548 assert(free_regions_coming(), "pre-condition"); 6549 6550 { 6551 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6552 _free_regions_coming = false; 6553 SecondaryFreeList_lock->notify_all(); 6554 } 6555 6556 if (G1ConcRegionFreeingVerbose) { 6557 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6558 "reset free regions coming"); 6559 } 6560 } 6561 6562 void G1CollectedHeap::wait_while_free_regions_coming() { 6563 // Most of the time we won't have to wait, so let's do a quick test 6564 // first before we take the lock. 6565 if (!free_regions_coming()) { 6566 return; 6567 } 6568 6569 if (G1ConcRegionFreeingVerbose) { 6570 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6571 "waiting for free regions"); 6572 } 6573 6574 { 6575 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6576 while (free_regions_coming()) { 6577 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6578 } 6579 } 6580 6581 if (G1ConcRegionFreeingVerbose) { 6582 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6583 "done waiting for free regions"); 6584 } 6585 } 6586 6587 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6588 assert(heap_lock_held_for_gc(), 6589 "the heap lock should already be held by or for this thread"); 6590 _young_list->push_region(hr); 6591 } 6592 6593 class NoYoungRegionsClosure: public HeapRegionClosure { 6594 private: 6595 bool _success; 6596 public: 6597 NoYoungRegionsClosure() : _success(true) { } 6598 bool doHeapRegion(HeapRegion* r) { 6599 if (r->is_young()) { 6600 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6601 r->bottom(), r->end()); 6602 _success = false; 6603 } 6604 return false; 6605 } 6606 bool success() { return _success; } 6607 }; 6608 6609 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6610 bool ret = _young_list->check_list_empty(check_sample); 6611 6612 if (check_heap) { 6613 NoYoungRegionsClosure closure; 6614 heap_region_iterate(&closure); 6615 ret = ret && closure.success(); 6616 } 6617 6618 return ret; 6619 } 6620 6621 class TearDownRegionSetsClosure : public HeapRegionClosure { 6622 private: 6623 HeapRegionSet *_old_set; 6624 6625 public: 6626 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 6627 6628 bool doHeapRegion(HeapRegion* r) { 6629 if (r->is_old()) { 6630 _old_set->remove(r); 6631 } else { 6632 // We ignore free regions, we'll empty the free list afterwards. 6633 // We ignore young regions, we'll empty the young list afterwards. 6634 // We ignore humongous regions, we're not tearing down the 6635 // humongous regions set. 6636 assert(r->is_free() || r->is_young() || r->isHumongous(), 6637 "it cannot be another type"); 6638 } 6639 return false; 6640 } 6641 6642 ~TearDownRegionSetsClosure() { 6643 assert(_old_set->is_empty(), "post-condition"); 6644 } 6645 }; 6646 6647 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6648 assert_at_safepoint(true /* should_be_vm_thread */); 6649 6650 if (!free_list_only) { 6651 TearDownRegionSetsClosure cl(&_old_set); 6652 heap_region_iterate(&cl); 6653 6654 // Note that emptying the _young_list is postponed and instead done as 6655 // the first step when rebuilding the regions sets again. The reason for 6656 // this is that during a full GC string deduplication needs to know if 6657 // a collected region was young or old when the full GC was initiated. 6658 } 6659 _hrm.remove_all_free_regions(); 6660 } 6661 6662 class RebuildRegionSetsClosure : public HeapRegionClosure { 6663 private: 6664 bool _free_list_only; 6665 HeapRegionSet* _old_set; 6666 HeapRegionManager* _hrm; 6667 size_t _total_used; 6668 6669 public: 6670 RebuildRegionSetsClosure(bool free_list_only, 6671 HeapRegionSet* old_set, HeapRegionManager* hrm) : 6672 _free_list_only(free_list_only), 6673 _old_set(old_set), _hrm(hrm), _total_used(0) { 6674 assert(_hrm->num_free_regions() == 0, "pre-condition"); 6675 if (!free_list_only) { 6676 assert(_old_set->is_empty(), "pre-condition"); 6677 } 6678 } 6679 6680 bool doHeapRegion(HeapRegion* r) { 6681 if (r->continuesHumongous()) { 6682 return false; 6683 } 6684 6685 if (r->is_empty()) { 6686 // Add free regions to the free list 6687 r->set_free(); 6688 r->set_allocation_context(AllocationContext::system()); 6689 _hrm->insert_into_free_list(r); 6690 } else if (!_free_list_only) { 6691 assert(!r->is_young(), "we should not come across young regions"); 6692 6693 if (r->isHumongous()) { 6694 // We ignore humongous regions, we left the humongous set unchanged 6695 } else { 6696 // Objects that were compacted would have ended up on regions 6697 // that were previously old or free. 6698 assert(r->is_free() || r->is_old(), "invariant"); 6699 // We now consider them old, so register as such. 6700 r->set_old(); 6701 _old_set->add(r); 6702 } 6703 _total_used += r->used(); 6704 } 6705 6706 return false; 6707 } 6708 6709 size_t total_used() { 6710 return _total_used; 6711 } 6712 }; 6713 6714 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6715 assert_at_safepoint(true /* should_be_vm_thread */); 6716 6717 if (!free_list_only) { 6718 _young_list->empty_list(); 6719 } 6720 6721 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6722 heap_region_iterate(&cl); 6723 6724 if (!free_list_only) { 6725 _allocator->set_used(cl.total_used()); 6726 } 6727 assert(_allocator->used_unlocked() == recalculate_used(), 6728 err_msg("inconsistent _allocator->used_unlocked(), " 6729 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6730 _allocator->used_unlocked(), recalculate_used())); 6731 } 6732 6733 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6734 _refine_cte_cl->set_concurrent(concurrent); 6735 } 6736 6737 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6738 HeapRegion* hr = heap_region_containing(p); 6739 return hr->is_in(p); 6740 } 6741 6742 // Methods for the mutator alloc region 6743 6744 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6745 bool force) { 6746 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6747 assert(!force || g1_policy()->can_expand_young_list(), 6748 "if force is true we should be able to expand the young list"); 6749 bool young_list_full = g1_policy()->is_young_list_full(); 6750 if (force || !young_list_full) { 6751 HeapRegion* new_alloc_region = new_region(word_size, 6752 false /* is_old */, 6753 false /* do_expand */); 6754 if (new_alloc_region != NULL) { 6755 set_region_short_lived_locked(new_alloc_region); 6756 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6757 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6758 return new_alloc_region; 6759 } 6760 } 6761 return NULL; 6762 } 6763 6764 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6765 size_t allocated_bytes) { 6766 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6767 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6768 6769 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6770 _allocator->increase_used(allocated_bytes); 6771 _hr_printer.retire(alloc_region); 6772 // We update the eden sizes here, when the region is retired, 6773 // instead of when it's allocated, since this is the point that its 6774 // used space has been recored in _summary_bytes_used. 6775 g1mm()->update_eden_size(); 6776 } 6777 6778 void G1CollectedHeap::set_par_threads() { 6779 // Don't change the number of workers. Use the value previously set 6780 // in the workgroup. 6781 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6782 uint n_workers = workers()->active_workers(); 6783 assert(UseDynamicNumberOfGCThreads || 6784 n_workers == workers()->total_workers(), 6785 "Otherwise should be using the total number of workers"); 6786 if (n_workers == 0) { 6787 assert(false, "Should have been set in prior evacuation pause."); 6788 n_workers = ParallelGCThreads; 6789 workers()->set_active_workers(n_workers); 6790 } 6791 set_par_threads(n_workers); 6792 } 6793 6794 // Methods for the GC alloc regions 6795 6796 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6797 uint count, 6798 GCAllocPurpose ap) { 6799 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6800 6801 if (count < g1_policy()->max_regions(ap)) { 6802 bool survivor = (ap == GCAllocForSurvived); 6803 HeapRegion* new_alloc_region = new_region(word_size, 6804 !survivor, 6805 true /* do_expand */); 6806 if (new_alloc_region != NULL) { 6807 // We really only need to do this for old regions given that we 6808 // should never scan survivors. But it doesn't hurt to do it 6809 // for survivors too. 6810 new_alloc_region->record_top_and_timestamp(); 6811 if (survivor) { 6812 new_alloc_region->set_survivor(); 6813 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6814 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6815 } else { 6816 new_alloc_region->set_old(); 6817 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6818 check_bitmaps("Old Region Allocation", new_alloc_region); 6819 } 6820 bool during_im = g1_policy()->during_initial_mark_pause(); 6821 new_alloc_region->note_start_of_copying(during_im); 6822 return new_alloc_region; 6823 } else { 6824 g1_policy()->note_alloc_region_limit_reached(ap); 6825 } 6826 } 6827 return NULL; 6828 } 6829 6830 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6831 size_t allocated_bytes, 6832 GCAllocPurpose ap) { 6833 bool during_im = g1_policy()->during_initial_mark_pause(); 6834 alloc_region->note_end_of_copying(during_im); 6835 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6836 if (ap == GCAllocForSurvived) { 6837 young_list()->add_survivor_region(alloc_region); 6838 } else { 6839 _old_set.add(alloc_region); 6840 } 6841 _hr_printer.retire(alloc_region); 6842 } 6843 6844 // Heap region set verification 6845 6846 class VerifyRegionListsClosure : public HeapRegionClosure { 6847 private: 6848 HeapRegionSet* _old_set; 6849 HeapRegionSet* _humongous_set; 6850 HeapRegionManager* _hrm; 6851 6852 public: 6853 HeapRegionSetCount _old_count; 6854 HeapRegionSetCount _humongous_count; 6855 HeapRegionSetCount _free_count; 6856 6857 VerifyRegionListsClosure(HeapRegionSet* old_set, 6858 HeapRegionSet* humongous_set, 6859 HeapRegionManager* hrm) : 6860 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6861 _old_count(), _humongous_count(), _free_count(){ } 6862 6863 bool doHeapRegion(HeapRegion* hr) { 6864 if (hr->continuesHumongous()) { 6865 return false; 6866 } 6867 6868 if (hr->is_young()) { 6869 // TODO 6870 } else if (hr->startsHumongous()) { 6871 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index())); 6872 _humongous_count.increment(1u, hr->capacity()); 6873 } else if (hr->is_empty()) { 6874 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index())); 6875 _free_count.increment(1u, hr->capacity()); 6876 } else if (hr->is_old()) { 6877 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index())); 6878 _old_count.increment(1u, hr->capacity()); 6879 } else { 6880 ShouldNotReachHere(); 6881 } 6882 return false; 6883 } 6884 6885 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6886 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length())); 6887 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6888 old_set->total_capacity_bytes(), _old_count.capacity())); 6889 6890 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length())); 6891 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6892 humongous_set->total_capacity_bytes(), _humongous_count.capacity())); 6893 6894 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length())); 6895 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6896 free_list->total_capacity_bytes(), _free_count.capacity())); 6897 } 6898 }; 6899 6900 void G1CollectedHeap::verify_region_sets() { 6901 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6902 6903 // First, check the explicit lists. 6904 _hrm.verify(); 6905 { 6906 // Given that a concurrent operation might be adding regions to 6907 // the secondary free list we have to take the lock before 6908 // verifying it. 6909 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6910 _secondary_free_list.verify_list(); 6911 } 6912 6913 // If a concurrent region freeing operation is in progress it will 6914 // be difficult to correctly attributed any free regions we come 6915 // across to the correct free list given that they might belong to 6916 // one of several (free_list, secondary_free_list, any local lists, 6917 // etc.). So, if that's the case we will skip the rest of the 6918 // verification operation. Alternatively, waiting for the concurrent 6919 // operation to complete will have a non-trivial effect on the GC's 6920 // operation (no concurrent operation will last longer than the 6921 // interval between two calls to verification) and it might hide 6922 // any issues that we would like to catch during testing. 6923 if (free_regions_coming()) { 6924 return; 6925 } 6926 6927 // Make sure we append the secondary_free_list on the free_list so 6928 // that all free regions we will come across can be safely 6929 // attributed to the free_list. 6930 append_secondary_free_list_if_not_empty_with_lock(); 6931 6932 // Finally, make sure that the region accounting in the lists is 6933 // consistent with what we see in the heap. 6934 6935 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6936 heap_region_iterate(&cl); 6937 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6938 } 6939 6940 // Optimized nmethod scanning 6941 6942 class RegisterNMethodOopClosure: public OopClosure { 6943 G1CollectedHeap* _g1h; 6944 nmethod* _nm; 6945 6946 template <class T> void do_oop_work(T* p) { 6947 T heap_oop = oopDesc::load_heap_oop(p); 6948 if (!oopDesc::is_null(heap_oop)) { 6949 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6950 HeapRegion* hr = _g1h->heap_region_containing(obj); 6951 assert(!hr->continuesHumongous(), 6952 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6953 " starting at "HR_FORMAT, 6954 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6955 6956 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6957 hr->add_strong_code_root_locked(_nm); 6958 } 6959 } 6960 6961 public: 6962 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6963 _g1h(g1h), _nm(nm) {} 6964 6965 void do_oop(oop* p) { do_oop_work(p); } 6966 void do_oop(narrowOop* p) { do_oop_work(p); } 6967 }; 6968 6969 class UnregisterNMethodOopClosure: public OopClosure { 6970 G1CollectedHeap* _g1h; 6971 nmethod* _nm; 6972 6973 template <class T> void do_oop_work(T* p) { 6974 T heap_oop = oopDesc::load_heap_oop(p); 6975 if (!oopDesc::is_null(heap_oop)) { 6976 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6977 HeapRegion* hr = _g1h->heap_region_containing(obj); 6978 assert(!hr->continuesHumongous(), 6979 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6980 " starting at "HR_FORMAT, 6981 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6982 6983 hr->remove_strong_code_root(_nm); 6984 } 6985 } 6986 6987 public: 6988 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6989 _g1h(g1h), _nm(nm) {} 6990 6991 void do_oop(oop* p) { do_oop_work(p); } 6992 void do_oop(narrowOop* p) { do_oop_work(p); } 6993 }; 6994 6995 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6996 CollectedHeap::register_nmethod(nm); 6997 6998 guarantee(nm != NULL, "sanity"); 6999 RegisterNMethodOopClosure reg_cl(this, nm); 7000 nm->oops_do(®_cl); 7001 } 7002 7003 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 7004 CollectedHeap::unregister_nmethod(nm); 7005 7006 guarantee(nm != NULL, "sanity"); 7007 UnregisterNMethodOopClosure reg_cl(this, nm); 7008 nm->oops_do(®_cl, true); 7009 } 7010 7011 void G1CollectedHeap::purge_code_root_memory() { 7012 double purge_start = os::elapsedTime(); 7013 G1CodeRootSet::purge(); 7014 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 7015 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 7016 } 7017 7018 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 7019 G1CollectedHeap* _g1h; 7020 7021 public: 7022 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 7023 _g1h(g1h) {} 7024 7025 void do_code_blob(CodeBlob* cb) { 7026 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 7027 if (nm == NULL) { 7028 return; 7029 } 7030 7031 if (ScavengeRootsInCode) { 7032 _g1h->register_nmethod(nm); 7033 } 7034 } 7035 }; 7036 7037 void G1CollectedHeap::rebuild_strong_code_roots() { 7038 RebuildStrongCodeRootClosure blob_cl(this); 7039 CodeCache::blobs_do(&blob_cl); 7040 }