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 // FIXME, formats have issues. Disable this macro definition, compile, and study warnings for more information. 27 #define ATTRIBUTE_PRINTF(x,y) 28 #endif 29 30 #include "precompiled.hpp" 31 #include "classfile/stringTable.hpp" 32 #include "code/codeCache.hpp" 33 #include "code/icBuffer.hpp" 34 #include "gc_implementation/g1/bufferingOopClosure.hpp" 35 #include "gc_implementation/g1/concurrentG1Refine.hpp" 36 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 37 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" 38 #include "gc_implementation/g1/g1AllocRegion.inline.hpp" 39 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 40 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 41 #include "gc_implementation/g1/g1ErgoVerbose.hpp" 42 #include "gc_implementation/g1/g1EvacFailure.hpp" 43 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 44 #include "gc_implementation/g1/g1Log.hpp" 45 #include "gc_implementation/g1/g1MarkSweep.hpp" 46 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 47 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp" 48 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp" 49 #include "gc_implementation/g1/g1RemSet.inline.hpp" 50 #include "gc_implementation/g1/g1StringDedup.hpp" 51 #include "gc_implementation/g1/g1YCTypes.hpp" 52 #include "gc_implementation/g1/heapRegion.inline.hpp" 53 #include "gc_implementation/g1/heapRegionRemSet.hpp" 54 #include "gc_implementation/g1/heapRegionSet.inline.hpp" 55 #include "gc_implementation/g1/vm_operations_g1.hpp" 56 #include "gc_implementation/shared/gcHeapSummary.hpp" 57 #include "gc_implementation/shared/gcTimer.hpp" 58 #include "gc_implementation/shared/gcTrace.hpp" 59 #include "gc_implementation/shared/gcTraceTime.hpp" 60 #include "gc_implementation/shared/isGCActiveMark.hpp" 61 #include "memory/allocation.hpp" 62 #include "memory/gcLocker.inline.hpp" 63 #include "memory/generationSpec.hpp" 64 #include "memory/iterator.hpp" 65 #include "memory/referenceProcessor.hpp" 66 #include "oops/oop.inline.hpp" 67 #include "oops/oop.pcgc.inline.hpp" 68 #include "runtime/atomic.inline.hpp" 69 #include "runtime/orderAccess.inline.hpp" 70 #include "runtime/vmThread.hpp" 71 #include "utilities/globalDefinitions.hpp" 72 73 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 74 75 // turn it on so that the contents of the young list (scan-only / 76 // to-be-collected) are printed at "strategic" points before / during 77 // / after the collection --- this is useful for debugging 78 #define YOUNG_LIST_VERBOSE 0 79 // CURRENT STATUS 80 // This file is under construction. Search for "FIXME". 81 82 // INVARIANTS/NOTES 83 // 84 // All allocation activity covered by the G1CollectedHeap interface is 85 // serialized by acquiring the HeapLock. This happens in mem_allocate 86 // and allocate_new_tlab, which are the "entry" points to the 87 // allocation code from the rest of the JVM. (Note that this does not 88 // apply to TLAB allocation, which is not part of this interface: it 89 // is done by clients of this interface.) 90 91 // Notes on implementation of parallelism in different tasks. 92 // 93 // G1ParVerifyTask uses heap_region_par_iterate() for parallelism. 94 // The number of GC workers is passed to heap_region_par_iterate(). 95 // It does use run_task() which sets _n_workers in the task. 96 // G1ParTask executes g1_process_roots() -> 97 // SharedHeap::process_roots() which calls eventually to 98 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses 99 // SequentialSubTasksDone. SharedHeap::process_roots() also 100 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap). 101 // 102 103 // Local to this file. 104 105 class RefineCardTableEntryClosure: public CardTableEntryClosure { 106 bool _concurrent; 107 public: 108 RefineCardTableEntryClosure() : _concurrent(true) { } 109 110 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 111 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 112 // This path is executed by the concurrent refine or mutator threads, 113 // concurrently, and so we do not care if card_ptr contains references 114 // that point into the collection set. 115 assert(!oops_into_cset, "should be"); 116 117 if (_concurrent && SuspendibleThreadSet::should_yield()) { 118 // Caller will actually yield. 119 return false; 120 } 121 // Otherwise, we finished successfully; return true. 122 return true; 123 } 124 125 void set_concurrent(bool b) { _concurrent = b; } 126 }; 127 128 129 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 130 size_t _num_processed; 131 CardTableModRefBS* _ctbs; 132 int _histo[256]; 133 134 public: 135 ClearLoggedCardTableEntryClosure() : 136 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set()) 137 { 138 for (int i = 0; i < 256; i++) _histo[i] = 0; 139 } 140 141 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 142 unsigned char* ujb = (unsigned char*)card_ptr; 143 int ind = (int)(*ujb); 144 _histo[ind]++; 145 146 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val(); 147 _num_processed++; 148 149 return true; 150 } 151 152 size_t num_processed() { return _num_processed; } 153 154 void print_histo() { 155 gclog_or_tty->print_cr("Card table value histogram:"); 156 for (int i = 0; i < 256; i++) { 157 if (_histo[i] != 0) { 158 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); 159 } 160 } 161 } 162 }; 163 164 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 165 private: 166 size_t _num_processed; 167 168 public: 169 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 170 171 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 172 *card_ptr = CardTableModRefBS::dirty_card_val(); 173 _num_processed++; 174 return true; 175 } 176 177 size_t num_processed() const { return _num_processed; } 178 }; 179 180 YoungList::YoungList(G1CollectedHeap* g1h) : 181 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 182 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 183 guarantee(check_list_empty(false), "just making sure..."); 184 } 185 186 void YoungList::push_region(HeapRegion *hr) { 187 assert(!hr->is_young(), "should not already be young"); 188 assert(hr->get_next_young_region() == NULL, "cause it should!"); 189 190 hr->set_next_young_region(_head); 191 _head = hr; 192 193 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 194 ++_length; 195 } 196 197 void YoungList::add_survivor_region(HeapRegion* hr) { 198 assert(hr->is_survivor(), "should be flagged as survivor region"); 199 assert(hr->get_next_young_region() == NULL, "cause it should!"); 200 201 hr->set_next_young_region(_survivor_head); 202 if (_survivor_head == NULL) { 203 _survivor_tail = hr; 204 } 205 _survivor_head = hr; 206 ++_survivor_length; 207 } 208 209 void YoungList::empty_list(HeapRegion* list) { 210 while (list != NULL) { 211 HeapRegion* next = list->get_next_young_region(); 212 list->set_next_young_region(NULL); 213 list->uninstall_surv_rate_group(); 214 // This is called before a Full GC and all the non-empty / 215 // non-humongous regions at the end of the Full GC will end up as 216 // old anyway. 217 list->set_old(); 218 list = next; 219 } 220 } 221 222 void YoungList::empty_list() { 223 assert(check_list_well_formed(), "young list should be well formed"); 224 225 empty_list(_head); 226 _head = NULL; 227 _length = 0; 228 229 empty_list(_survivor_head); 230 _survivor_head = NULL; 231 _survivor_tail = NULL; 232 _survivor_length = 0; 233 234 _last_sampled_rs_lengths = 0; 235 236 assert(check_list_empty(false), "just making sure..."); 237 } 238 239 bool YoungList::check_list_well_formed() { 240 bool ret = true; 241 242 uint length = 0; 243 HeapRegion* curr = _head; 244 HeapRegion* last = NULL; 245 while (curr != NULL) { 246 if (!curr->is_young()) { 247 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 248 "incorrectly tagged (y: %d, surv: %d)", 249 curr->bottom(), curr->end(), 250 curr->is_young(), curr->is_survivor()); 251 ret = false; 252 } 253 ++length; 254 last = curr; 255 curr = curr->get_next_young_region(); 256 } 257 ret = ret && (length == _length); 258 259 if (!ret) { 260 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 261 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 262 length, _length); 263 } 264 265 return ret; 266 } 267 268 bool YoungList::check_list_empty(bool check_sample) { 269 bool ret = true; 270 271 if (_length != 0) { 272 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 273 _length); 274 ret = false; 275 } 276 if (check_sample && _last_sampled_rs_lengths != 0) { 277 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 278 ret = false; 279 } 280 if (_head != NULL) { 281 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 282 ret = false; 283 } 284 if (!ret) { 285 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 286 } 287 288 return ret; 289 } 290 291 void 292 YoungList::rs_length_sampling_init() { 293 _sampled_rs_lengths = 0; 294 _curr = _head; 295 } 296 297 bool 298 YoungList::rs_length_sampling_more() { 299 return _curr != NULL; 300 } 301 302 void 303 YoungList::rs_length_sampling_next() { 304 assert( _curr != NULL, "invariant" ); 305 size_t rs_length = _curr->rem_set()->occupied(); 306 307 _sampled_rs_lengths += rs_length; 308 309 // The current region may not yet have been added to the 310 // incremental collection set (it gets added when it is 311 // retired as the current allocation region). 312 if (_curr->in_collection_set()) { 313 // Update the collection set policy information for this region 314 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 315 } 316 317 _curr = _curr->get_next_young_region(); 318 if (_curr == NULL) { 319 _last_sampled_rs_lengths = _sampled_rs_lengths; 320 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 321 } 322 } 323 324 void 325 YoungList::reset_auxilary_lists() { 326 guarantee( is_empty(), "young list should be empty" ); 327 assert(check_list_well_formed(), "young list should be well formed"); 328 329 // Add survivor regions to SurvRateGroup. 330 _g1h->g1_policy()->note_start_adding_survivor_regions(); 331 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 332 333 int young_index_in_cset = 0; 334 for (HeapRegion* curr = _survivor_head; 335 curr != NULL; 336 curr = curr->get_next_young_region()) { 337 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 338 339 // The region is a non-empty survivor so let's add it to 340 // the incremental collection set for the next evacuation 341 // pause. 342 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 343 young_index_in_cset += 1; 344 } 345 assert((uint) young_index_in_cset == _survivor_length, "post-condition"); 346 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 347 348 _head = _survivor_head; 349 _length = _survivor_length; 350 if (_survivor_head != NULL) { 351 assert(_survivor_tail != NULL, "cause it shouldn't be"); 352 assert(_survivor_length > 0, "invariant"); 353 _survivor_tail->set_next_young_region(NULL); 354 } 355 356 // Don't clear the survivor list handles until the start of 357 // the next evacuation pause - we need it in order to re-tag 358 // the survivor regions from this evacuation pause as 'young' 359 // at the start of the next. 360 361 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 362 363 assert(check_list_well_formed(), "young list should be well formed"); 364 } 365 366 void YoungList::print() { 367 HeapRegion* lists[] = {_head, _survivor_head}; 368 const char* names[] = {"YOUNG", "SURVIVOR"}; 369 370 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { 371 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 372 HeapRegion *curr = lists[list]; 373 if (curr == NULL) 374 gclog_or_tty->print_cr(" empty"); 375 while (curr != NULL) { 376 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d", 377 HR_FORMAT_PARAMS(curr), 378 curr->prev_top_at_mark_start(), 379 curr->next_top_at_mark_start(), 380 curr->age_in_surv_rate_group_cond()); 381 curr = curr->get_next_young_region(); 382 } 383 } 384 385 gclog_or_tty->cr(); 386 } 387 388 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 389 OtherRegionsTable::invalidate(start_idx, num_regions); 390 } 391 392 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions) { 393 reset_from_card_cache(start_idx, num_regions); 394 } 395 396 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 397 { 398 // Claim the right to put the region on the dirty cards region list 399 // by installing a self pointer. 400 HeapRegion* next = hr->get_next_dirty_cards_region(); 401 if (next == NULL) { 402 HeapRegion* res = (HeapRegion*) 403 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 404 NULL); 405 if (res == NULL) { 406 HeapRegion* head; 407 do { 408 // Put the region to the dirty cards region list. 409 head = _dirty_cards_region_list; 410 next = (HeapRegion*) 411 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 412 if (next == head) { 413 assert(hr->get_next_dirty_cards_region() == hr, 414 "hr->get_next_dirty_cards_region() != hr"); 415 if (next == NULL) { 416 // The last region in the list points to itself. 417 hr->set_next_dirty_cards_region(hr); 418 } else { 419 hr->set_next_dirty_cards_region(next); 420 } 421 } 422 } while (next != head); 423 } 424 } 425 } 426 427 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 428 { 429 HeapRegion* head; 430 HeapRegion* hr; 431 do { 432 head = _dirty_cards_region_list; 433 if (head == NULL) { 434 return NULL; 435 } 436 HeapRegion* new_head = head->get_next_dirty_cards_region(); 437 if (head == new_head) { 438 // The last region. 439 new_head = NULL; 440 } 441 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 442 head); 443 } while (hr != head); 444 assert(hr != NULL, "invariant"); 445 hr->set_next_dirty_cards_region(NULL); 446 return hr; 447 } 448 449 #ifdef ASSERT 450 // A region is added to the collection set as it is retired 451 // so an address p can point to a region which will be in the 452 // collection set but has not yet been retired. This method 453 // therefore is only accurate during a GC pause after all 454 // regions have been retired. It is used for debugging 455 // to check if an nmethod has references to objects that can 456 // be move during a partial collection. Though it can be 457 // inaccurate, it is sufficient for G1 because the conservative 458 // implementation of is_scavengable() for G1 will indicate that 459 // all nmethods must be scanned during a partial collection. 460 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 461 if (p == NULL) { 462 return false; 463 } 464 return heap_region_containing(p)->in_collection_set(); 465 } 466 #endif 467 468 // Returns true if the reference points to an object that 469 // can move in an incremental collection. 470 bool G1CollectedHeap::is_scavengable(const void* p) { 471 HeapRegion* hr = heap_region_containing(p); 472 return !hr->is_humongous(); 473 } 474 475 void G1CollectedHeap::check_ct_logs_at_safepoint() { 476 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 477 CardTableModRefBS* ct_bs = g1_barrier_set(); 478 479 // Count the dirty cards at the start. 480 CountNonCleanMemRegionClosure count1(this); 481 ct_bs->mod_card_iterate(&count1); 482 int orig_count = count1.n(); 483 484 // First clear the logged cards. 485 ClearLoggedCardTableEntryClosure clear; 486 dcqs.apply_closure_to_all_completed_buffers(&clear); 487 dcqs.iterate_closure_all_threads(&clear, false); 488 clear.print_histo(); 489 490 // Now ensure that there's no dirty cards. 491 CountNonCleanMemRegionClosure count2(this); 492 ct_bs->mod_card_iterate(&count2); 493 if (count2.n() != 0) { 494 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 495 count2.n(), orig_count); 496 } 497 guarantee(count2.n() == 0, "Card table should be clean."); 498 499 RedirtyLoggedCardTableEntryClosure redirty; 500 dcqs.apply_closure_to_all_completed_buffers(&redirty); 501 dcqs.iterate_closure_all_threads(&redirty, false); 502 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 503 clear.num_processed(), orig_count); 504 guarantee(redirty.num_processed() == clear.num_processed(), 505 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT, 506 redirty.num_processed(), clear.num_processed())); 507 508 CountNonCleanMemRegionClosure count3(this); 509 ct_bs->mod_card_iterate(&count3); 510 if (count3.n() != orig_count) { 511 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 512 orig_count, count3.n()); 513 guarantee(count3.n() >= orig_count, "Should have restored them all."); 514 } 515 } 516 517 // Private class members. 518 519 G1CollectedHeap* G1CollectedHeap::_g1h; 520 521 // Private methods. 522 523 HeapRegion* 524 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 525 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 526 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 527 if (!_secondary_free_list.is_empty()) { 528 if (G1ConcRegionFreeingVerbose) { 529 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 530 "secondary_free_list has %u entries", 531 _secondary_free_list.length()); 532 } 533 // It looks as if there are free regions available on the 534 // secondary_free_list. Let's move them to the free_list and try 535 // again to allocate from it. 536 append_secondary_free_list(); 537 538 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 539 "empty we should have moved at least one entry to the free_list"); 540 HeapRegion* res = _hrm.allocate_free_region(is_old); 541 if (G1ConcRegionFreeingVerbose) { 542 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 543 "allocated "HR_FORMAT" from secondary_free_list", 544 HR_FORMAT_PARAMS(res)); 545 } 546 return res; 547 } 548 549 // Wait here until we get notified either when (a) there are no 550 // more free regions coming or (b) some regions have been moved on 551 // the secondary_free_list. 552 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 553 } 554 555 if (G1ConcRegionFreeingVerbose) { 556 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 557 "could not allocate from secondary_free_list"); 558 } 559 return NULL; 560 } 561 562 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 563 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 564 "the only time we use this to allocate a humongous region is " 565 "when we are allocating a single humongous region"); 566 567 HeapRegion* res; 568 if (G1StressConcRegionFreeing) { 569 if (!_secondary_free_list.is_empty()) { 570 if (G1ConcRegionFreeingVerbose) { 571 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 572 "forced to look at the secondary_free_list"); 573 } 574 res = new_region_try_secondary_free_list(is_old); 575 if (res != NULL) { 576 return res; 577 } 578 } 579 } 580 581 res = _hrm.allocate_free_region(is_old); 582 583 if (res == NULL) { 584 if (G1ConcRegionFreeingVerbose) { 585 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 586 "res == NULL, trying the secondary_free_list"); 587 } 588 res = new_region_try_secondary_free_list(is_old); 589 } 590 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 591 // Currently, only attempts to allocate GC alloc regions set 592 // do_expand to true. So, we should only reach here during a 593 // safepoint. If this assumption changes we might have to 594 // reconsider the use of _expand_heap_after_alloc_failure. 595 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 596 597 ergo_verbose1(ErgoHeapSizing, 598 "attempt heap expansion", 599 ergo_format_reason("region allocation request failed") 600 ergo_format_byte("allocation request"), 601 word_size * HeapWordSize); 602 if (expand(word_size * HeapWordSize)) { 603 // Given that expand() succeeded in expanding the heap, and we 604 // always expand the heap by an amount aligned to the heap 605 // region size, the free list should in theory not be empty. 606 // In either case allocate_free_region() will check for NULL. 607 res = _hrm.allocate_free_region(is_old); 608 } else { 609 _expand_heap_after_alloc_failure = false; 610 } 611 } 612 return res; 613 } 614 615 HeapWord* 616 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 617 uint num_regions, 618 size_t word_size, 619 AllocationContext_t context) { 620 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 621 assert(is_humongous(word_size), "word_size should be humongous"); 622 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 623 624 // Index of last region in the series + 1. 625 uint last = first + num_regions; 626 627 // We need to initialize the region(s) we just discovered. This is 628 // a bit tricky given that it can happen concurrently with 629 // refinement threads refining cards on these regions and 630 // potentially wanting to refine the BOT as they are scanning 631 // those cards (this can happen shortly after a cleanup; see CR 632 // 6991377). So we have to set up the region(s) carefully and in 633 // a specific order. 634 635 // The word size sum of all the regions we will allocate. 636 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 637 assert(word_size <= word_size_sum, "sanity"); 638 639 // This will be the "starts humongous" region. 640 HeapRegion* first_hr = region_at(first); 641 // The header of the new object will be placed at the bottom of 642 // the first region. 643 HeapWord* new_obj = first_hr->bottom(); 644 // This will be the new end of the first region in the series that 645 // should also match the end of the last region in the series. 646 HeapWord* new_end = new_obj + word_size_sum; 647 // This will be the new top of the first region that will reflect 648 // this allocation. 649 HeapWord* new_top = new_obj + word_size; 650 651 // First, we need to zero the header of the space that we will be 652 // allocating. When we update top further down, some refinement 653 // threads might try to scan the region. By zeroing the header we 654 // ensure that any thread that will try to scan the region will 655 // come across the zero klass word and bail out. 656 // 657 // NOTE: It would not have been correct to have used 658 // CollectedHeap::fill_with_object() and make the space look like 659 // an int array. The thread that is doing the allocation will 660 // later update the object header to a potentially different array 661 // type and, for a very short period of time, the klass and length 662 // fields will be inconsistent. This could cause a refinement 663 // thread to calculate the object size incorrectly. 664 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 665 666 // We will set up the first region as "starts humongous". This 667 // will also update the BOT covering all the regions to reflect 668 // that there is a single object that starts at the bottom of the 669 // first region. 670 first_hr->set_starts_humongous(new_top, new_end); 671 first_hr->set_allocation_context(context); 672 // Then, if there are any, we will set up the "continues 673 // humongous" regions. 674 HeapRegion* hr = NULL; 675 for (uint i = first + 1; i < last; ++i) { 676 hr = region_at(i); 677 hr->set_continues_humongous(first_hr); 678 hr->set_allocation_context(context); 679 } 680 // If we have "continues humongous" regions (hr != NULL), then the 681 // end of the last one should match new_end. 682 assert(hr == NULL || hr->end() == new_end, "sanity"); 683 684 // Up to this point no concurrent thread would have been able to 685 // do any scanning on any region in this series. All the top 686 // fields still point to bottom, so the intersection between 687 // [bottom,top] and [card_start,card_end] will be empty. Before we 688 // update the top fields, we'll do a storestore to make sure that 689 // no thread sees the update to top before the zeroing of the 690 // object header and the BOT initialization. 691 OrderAccess::storestore(); 692 693 // Now that the BOT and the object header have been initialized, 694 // we can update top of the "starts humongous" region. 695 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 696 "new_top should be in this region"); 697 first_hr->set_top(new_top); 698 if (_hr_printer.is_active()) { 699 HeapWord* bottom = first_hr->bottom(); 700 HeapWord* end = first_hr->orig_end(); 701 if ((first + 1) == last) { 702 // the series has a single humongous region 703 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 704 } else { 705 // the series has more than one humongous regions 706 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 707 } 708 } 709 710 // Now, we will update the top fields of the "continues humongous" 711 // regions. The reason we need to do this is that, otherwise, 712 // these regions would look empty and this will confuse parts of 713 // G1. For example, the code that looks for a consecutive number 714 // of empty regions will consider them empty and try to 715 // re-allocate them. We can extend is_empty() to also include 716 // !is_continues_humongous(), but it is easier to just update the top 717 // fields here. The way we set top for all regions (i.e., top == 718 // end for all regions but the last one, top == new_top for the 719 // last one) is actually used when we will free up the humongous 720 // region in free_humongous_region(). 721 hr = NULL; 722 for (uint i = first + 1; i < last; ++i) { 723 hr = region_at(i); 724 if ((i + 1) == last) { 725 // last continues humongous region 726 assert(hr->bottom() < new_top && new_top <= hr->end(), 727 "new_top should fall on this region"); 728 hr->set_top(new_top); 729 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 730 } else { 731 // not last one 732 assert(new_top > hr->end(), "new_top should be above this region"); 733 hr->set_top(hr->end()); 734 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 735 } 736 } 737 // If we have continues humongous regions (hr != NULL), then the 738 // end of the last one should match new_end and its top should 739 // match new_top. 740 assert(hr == NULL || 741 (hr->end() == new_end && hr->top() == new_top), "sanity"); 742 check_bitmaps("Humongous Region Allocation", first_hr); 743 744 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 745 _allocator->increase_used(first_hr->used()); 746 _humongous_set.add(first_hr); 747 748 return new_obj; 749 } 750 751 // If could fit into free regions w/o expansion, try. 752 // Otherwise, if can expand, do so. 753 // Otherwise, if using ex regions might help, try with ex given back. 754 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 755 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 756 757 verify_region_sets_optional(); 758 759 uint first = G1_NO_HRM_INDEX; 760 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 761 762 if (obj_regions == 1) { 763 // Only one region to allocate, try to use a fast path by directly allocating 764 // from the free lists. Do not try to expand here, we will potentially do that 765 // later. 766 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 767 if (hr != NULL) { 768 first = hr->hrm_index(); 769 } 770 } else { 771 // We can't allocate humongous regions spanning more than one region while 772 // cleanupComplete() is running, since some of the regions we find to be 773 // empty might not yet be added to the free list. It is not straightforward 774 // to know in which list they are on so that we can remove them. We only 775 // need to do this if we need to allocate more than one region to satisfy the 776 // current humongous allocation request. If we are only allocating one region 777 // we use the one-region region allocation code (see above), that already 778 // potentially waits for regions from the secondary free list. 779 wait_while_free_regions_coming(); 780 append_secondary_free_list_if_not_empty_with_lock(); 781 782 // Policy: Try only empty regions (i.e. already committed first). Maybe we 783 // are lucky enough to find some. 784 first = _hrm.find_contiguous_only_empty(obj_regions); 785 if (first != G1_NO_HRM_INDEX) { 786 _hrm.allocate_free_regions_starting_at(first, obj_regions); 787 } 788 } 789 790 if (first == G1_NO_HRM_INDEX) { 791 // Policy: We could not find enough regions for the humongous object in the 792 // free list. Look through the heap to find a mix of free and uncommitted regions. 793 // If so, try expansion. 794 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 795 if (first != G1_NO_HRM_INDEX) { 796 // We found something. Make sure these regions are committed, i.e. expand 797 // the heap. Alternatively we could do a defragmentation GC. 798 ergo_verbose1(ErgoHeapSizing, 799 "attempt heap expansion", 800 ergo_format_reason("humongous allocation request failed") 801 ergo_format_byte("allocation request"), 802 word_size * HeapWordSize); 803 804 _hrm.expand_at(first, obj_regions); 805 g1_policy()->record_new_heap_size(num_regions()); 806 807 #ifdef ASSERT 808 for (uint i = first; i < first + obj_regions; ++i) { 809 HeapRegion* hr = region_at(i); 810 assert(hr->is_free(), "sanity"); 811 assert(hr->is_empty(), "sanity"); 812 assert(is_on_master_free_list(hr), "sanity"); 813 } 814 #endif 815 _hrm.allocate_free_regions_starting_at(first, obj_regions); 816 } else { 817 // Policy: Potentially trigger a defragmentation GC. 818 } 819 } 820 821 HeapWord* result = NULL; 822 if (first != G1_NO_HRM_INDEX) { 823 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 824 word_size, context); 825 assert(result != NULL, "it should always return a valid result"); 826 827 // A successful humongous object allocation changes the used space 828 // information of the old generation so we need to recalculate the 829 // sizes and update the jstat counters here. 830 g1mm()->update_sizes(); 831 } 832 833 verify_region_sets_optional(); 834 835 return result; 836 } 837 838 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 839 assert_heap_not_locked_and_not_at_safepoint(); 840 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 841 842 unsigned int dummy_gc_count_before; 843 int dummy_gclocker_retry_count = 0; 844 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 845 } 846 847 HeapWord* 848 G1CollectedHeap::mem_allocate(size_t word_size, 849 bool* gc_overhead_limit_was_exceeded) { 850 assert_heap_not_locked_and_not_at_safepoint(); 851 852 // Loop until the allocation is satisfied, or unsatisfied after GC. 853 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 854 unsigned int gc_count_before; 855 856 HeapWord* result = NULL; 857 if (!is_humongous(word_size)) { 858 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 859 } else { 860 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 861 } 862 if (result != NULL) { 863 return result; 864 } 865 866 // Create the garbage collection operation... 867 VM_G1CollectForAllocation op(gc_count_before, word_size); 868 op.set_allocation_context(AllocationContext::current()); 869 870 // ...and get the VM thread to execute it. 871 VMThread::execute(&op); 872 873 if (op.prologue_succeeded() && op.pause_succeeded()) { 874 // If the operation was successful we'll return the result even 875 // if it is NULL. If the allocation attempt failed immediately 876 // after a Full GC, it's unlikely we'll be able to allocate now. 877 HeapWord* result = op.result(); 878 if (result != NULL && !is_humongous(word_size)) { 879 // Allocations that take place on VM operations do not do any 880 // card dirtying and we have to do it here. We only have to do 881 // this for non-humongous allocations, though. 882 dirty_young_block(result, word_size); 883 } 884 return result; 885 } else { 886 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 887 return NULL; 888 } 889 assert(op.result() == NULL, 890 "the result should be NULL if the VM op did not succeed"); 891 } 892 893 // Give a warning if we seem to be looping forever. 894 if ((QueuedAllocationWarningCount > 0) && 895 (try_count % QueuedAllocationWarningCount == 0)) { 896 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 897 } 898 } 899 900 ShouldNotReachHere(); 901 return NULL; 902 } 903 904 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 905 AllocationContext_t context, 906 unsigned int *gc_count_before_ret, 907 int* gclocker_retry_count_ret) { 908 // Make sure you read the note in attempt_allocation_humongous(). 909 910 assert_heap_not_locked_and_not_at_safepoint(); 911 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 912 "be called for humongous allocation requests"); 913 914 // We should only get here after the first-level allocation attempt 915 // (attempt_allocation()) failed to allocate. 916 917 // We will loop until a) we manage to successfully perform the 918 // allocation or b) we successfully schedule a collection which 919 // fails to perform the allocation. b) is the only case when we'll 920 // return NULL. 921 HeapWord* result = NULL; 922 for (int try_count = 1; /* we'll return */; try_count += 1) { 923 bool should_try_gc; 924 unsigned int gc_count_before; 925 926 { 927 MutexLockerEx x(Heap_lock); 928 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 929 false /* bot_updates */); 930 if (result != NULL) { 931 return result; 932 } 933 934 // If we reach here, attempt_allocation_locked() above failed to 935 // allocate a new region. So the mutator alloc region should be NULL. 936 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here"); 937 938 if (GC_locker::is_active_and_needs_gc()) { 939 if (g1_policy()->can_expand_young_list()) { 940 // No need for an ergo verbose message here, 941 // can_expand_young_list() does this when it returns true. 942 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size, 943 false /* bot_updates */); 944 if (result != NULL) { 945 return result; 946 } 947 } 948 should_try_gc = false; 949 } else { 950 // The GCLocker may not be active but the GCLocker initiated 951 // GC may not yet have been performed (GCLocker::needs_gc() 952 // returns true). In this case we do not try this GC and 953 // wait until the GCLocker initiated GC is performed, and 954 // then retry the allocation. 955 if (GC_locker::needs_gc()) { 956 should_try_gc = false; 957 } else { 958 // Read the GC count while still holding the Heap_lock. 959 gc_count_before = total_collections(); 960 should_try_gc = true; 961 } 962 } 963 } 964 965 if (should_try_gc) { 966 bool succeeded; 967 result = do_collection_pause(word_size, gc_count_before, &succeeded, 968 GCCause::_g1_inc_collection_pause); 969 if (result != NULL) { 970 assert(succeeded, "only way to get back a non-NULL result"); 971 return result; 972 } 973 974 if (succeeded) { 975 // If we get here we successfully scheduled a collection which 976 // failed to allocate. No point in trying to allocate 977 // further. We'll just return NULL. 978 MutexLockerEx x(Heap_lock); 979 *gc_count_before_ret = total_collections(); 980 return NULL; 981 } 982 } else { 983 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 984 MutexLockerEx x(Heap_lock); 985 *gc_count_before_ret = total_collections(); 986 return NULL; 987 } 988 // The GCLocker is either active or the GCLocker initiated 989 // GC has not yet been performed. Stall until it is and 990 // then retry the allocation. 991 GC_locker::stall_until_clear(); 992 (*gclocker_retry_count_ret) += 1; 993 } 994 995 // We can reach here if we were unsuccessful in scheduling a 996 // collection (because another thread beat us to it) or if we were 997 // stalled due to the GC locker. In either can we should retry the 998 // allocation attempt in case another thread successfully 999 // performed a collection and reclaimed enough space. We do the 1000 // first attempt (without holding the Heap_lock) here and the 1001 // follow-on attempt will be at the start of the next loop 1002 // iteration (after taking the Heap_lock). 1003 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size, 1004 false /* bot_updates */); 1005 if (result != NULL) { 1006 return result; 1007 } 1008 1009 // Give a warning if we seem to be looping forever. 1010 if ((QueuedAllocationWarningCount > 0) && 1011 (try_count % QueuedAllocationWarningCount == 0)) { 1012 warning("G1CollectedHeap::attempt_allocation_slow() " 1013 "retries %d times", try_count); 1014 } 1015 } 1016 1017 ShouldNotReachHere(); 1018 return NULL; 1019 } 1020 1021 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1022 unsigned int * gc_count_before_ret, 1023 int* gclocker_retry_count_ret) { 1024 // The structure of this method has a lot of similarities to 1025 // attempt_allocation_slow(). The reason these two were not merged 1026 // into a single one is that such a method would require several "if 1027 // allocation is not humongous do this, otherwise do that" 1028 // conditional paths which would obscure its flow. In fact, an early 1029 // version of this code did use a unified method which was harder to 1030 // follow and, as a result, it had subtle bugs that were hard to 1031 // track down. So keeping these two methods separate allows each to 1032 // be more readable. It will be good to keep these two in sync as 1033 // much as possible. 1034 1035 assert_heap_not_locked_and_not_at_safepoint(); 1036 assert(is_humongous(word_size), "attempt_allocation_humongous() " 1037 "should only be called for humongous allocations"); 1038 1039 // Humongous objects can exhaust the heap quickly, so we should check if we 1040 // need to start a marking cycle at each humongous object allocation. We do 1041 // the check before we do the actual allocation. The reason for doing it 1042 // before the allocation is that we avoid having to keep track of the newly 1043 // allocated memory while we do a GC. 1044 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1045 word_size)) { 1046 collect(GCCause::_g1_humongous_allocation); 1047 } 1048 1049 // We will loop until a) we manage to successfully perform the 1050 // allocation or b) we successfully schedule a collection which 1051 // fails to perform the allocation. b) is the only case when we'll 1052 // return NULL. 1053 HeapWord* result = NULL; 1054 for (int try_count = 1; /* we'll return */; try_count += 1) { 1055 bool should_try_gc; 1056 unsigned int gc_count_before; 1057 1058 { 1059 MutexLockerEx x(Heap_lock); 1060 1061 // Given that humongous objects are not allocated in young 1062 // regions, we'll first try to do the allocation without doing a 1063 // collection hoping that there's enough space in the heap. 1064 result = humongous_obj_allocate(word_size, AllocationContext::current()); 1065 if (result != NULL) { 1066 return result; 1067 } 1068 1069 if (GC_locker::is_active_and_needs_gc()) { 1070 should_try_gc = false; 1071 } else { 1072 // The GCLocker may not be active but the GCLocker initiated 1073 // GC may not yet have been performed (GCLocker::needs_gc() 1074 // returns true). In this case we do not try this GC and 1075 // wait until the GCLocker initiated GC is performed, and 1076 // then retry the allocation. 1077 if (GC_locker::needs_gc()) { 1078 should_try_gc = false; 1079 } else { 1080 // Read the GC count while still holding the Heap_lock. 1081 gc_count_before = total_collections(); 1082 should_try_gc = true; 1083 } 1084 } 1085 } 1086 1087 if (should_try_gc) { 1088 // If we failed to allocate the humongous object, we should try to 1089 // do a collection pause (if we're allowed) in case it reclaims 1090 // enough space for the allocation to succeed after the pause. 1091 1092 bool succeeded; 1093 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1094 GCCause::_g1_humongous_allocation); 1095 if (result != NULL) { 1096 assert(succeeded, "only way to get back a non-NULL result"); 1097 return result; 1098 } 1099 1100 if (succeeded) { 1101 // If we get here we successfully scheduled a collection which 1102 // failed to allocate. No point in trying to allocate 1103 // further. We'll just return NULL. 1104 MutexLockerEx x(Heap_lock); 1105 *gc_count_before_ret = total_collections(); 1106 return NULL; 1107 } 1108 } else { 1109 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1110 MutexLockerEx x(Heap_lock); 1111 *gc_count_before_ret = total_collections(); 1112 return NULL; 1113 } 1114 // The GCLocker is either active or the GCLocker initiated 1115 // GC has not yet been performed. Stall until it is and 1116 // then retry the allocation. 1117 GC_locker::stall_until_clear(); 1118 (*gclocker_retry_count_ret) += 1; 1119 } 1120 1121 // We can reach here if we were unsuccessful in scheduling a 1122 // collection (because another thread beat us to it) or if we were 1123 // stalled due to the GC locker. In either can we should retry the 1124 // allocation attempt in case another thread successfully 1125 // performed a collection and reclaimed enough space. Give a 1126 // warning if we seem to be looping forever. 1127 1128 if ((QueuedAllocationWarningCount > 0) && 1129 (try_count % QueuedAllocationWarningCount == 0)) { 1130 warning("G1CollectedHeap::attempt_allocation_humongous() " 1131 "retries %d times", try_count); 1132 } 1133 } 1134 1135 ShouldNotReachHere(); 1136 return NULL; 1137 } 1138 1139 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1140 AllocationContext_t context, 1141 bool expect_null_mutator_alloc_region) { 1142 assert_at_safepoint(true /* should_be_vm_thread */); 1143 assert(_allocator->mutator_alloc_region(context)->get() == NULL || 1144 !expect_null_mutator_alloc_region, 1145 "the current alloc region was unexpectedly found to be non-NULL"); 1146 1147 if (!is_humongous(word_size)) { 1148 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 1149 false /* bot_updates */); 1150 } else { 1151 HeapWord* result = humongous_obj_allocate(word_size, context); 1152 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1153 g1_policy()->set_initiate_conc_mark_if_possible(); 1154 } 1155 return result; 1156 } 1157 1158 ShouldNotReachHere(); 1159 } 1160 1161 class PostMCRemSetClearClosure: public HeapRegionClosure { 1162 G1CollectedHeap* _g1h; 1163 ModRefBarrierSet* _mr_bs; 1164 public: 1165 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1166 _g1h(g1h), _mr_bs(mr_bs) {} 1167 1168 bool doHeapRegion(HeapRegion* r) { 1169 HeapRegionRemSet* hrrs = r->rem_set(); 1170 1171 if (r->is_continues_humongous()) { 1172 // We'll assert that the strong code root list and RSet is empty 1173 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1174 assert(hrrs->occupied() == 0, "RSet should be empty"); 1175 return false; 1176 } 1177 1178 _g1h->reset_gc_time_stamps(r); 1179 hrrs->clear(); 1180 // You might think here that we could clear just the cards 1181 // corresponding to the used region. But no: if we leave a dirty card 1182 // in a region we might allocate into, then it would prevent that card 1183 // from being enqueued, and cause it to be missed. 1184 // Re: the performance cost: we shouldn't be doing full GC anyway! 1185 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1186 1187 return false; 1188 } 1189 }; 1190 1191 void G1CollectedHeap::clear_rsets_post_compaction() { 1192 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1193 heap_region_iterate(&rs_clear); 1194 } 1195 1196 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1197 G1CollectedHeap* _g1h; 1198 UpdateRSOopClosure _cl; 1199 int _worker_i; 1200 public: 1201 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1202 _cl(g1->g1_rem_set(), worker_i), 1203 _worker_i(worker_i), 1204 _g1h(g1) 1205 { } 1206 1207 bool doHeapRegion(HeapRegion* r) { 1208 if (!r->is_continues_humongous()) { 1209 _cl.set_from(r); 1210 r->oop_iterate(&_cl); 1211 } 1212 return false; 1213 } 1214 }; 1215 1216 class ParRebuildRSTask: public AbstractGangTask { 1217 G1CollectedHeap* _g1; 1218 HeapRegionClaimer _hrclaimer; 1219 1220 public: 1221 ParRebuildRSTask(G1CollectedHeap* g1) : 1222 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1223 1224 void work(uint worker_id) { 1225 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1226 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1227 } 1228 }; 1229 1230 class PostCompactionPrinterClosure: public HeapRegionClosure { 1231 private: 1232 G1HRPrinter* _hr_printer; 1233 public: 1234 bool doHeapRegion(HeapRegion* hr) { 1235 assert(!hr->is_young(), "not expecting to find young regions"); 1236 if (hr->is_free()) { 1237 // We only generate output for non-empty regions. 1238 } else if (hr->is_starts_humongous()) { 1239 if (hr->region_num() == 1) { 1240 // single humongous region 1241 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1242 } else { 1243 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1244 } 1245 } else if (hr->is_continues_humongous()) { 1246 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1247 } else if (hr->is_old()) { 1248 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1249 } else { 1250 ShouldNotReachHere(); 1251 } 1252 return false; 1253 } 1254 1255 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1256 : _hr_printer(hr_printer) { } 1257 }; 1258 1259 void G1CollectedHeap::print_hrm_post_compaction() { 1260 PostCompactionPrinterClosure cl(hr_printer()); 1261 heap_region_iterate(&cl); 1262 } 1263 1264 bool G1CollectedHeap::do_collection(bool explicit_gc, 1265 bool clear_all_soft_refs, 1266 size_t word_size) { 1267 assert_at_safepoint(true /* should_be_vm_thread */); 1268 1269 if (GC_locker::check_active_before_gc()) { 1270 return false; 1271 } 1272 1273 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1274 gc_timer->register_gc_start(); 1275 1276 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1277 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1278 1279 SvcGCMarker sgcm(SvcGCMarker::FULL); 1280 ResourceMark rm; 1281 1282 print_heap_before_gc(); 1283 trace_heap_before_gc(gc_tracer); 1284 1285 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1286 1287 verify_region_sets_optional(); 1288 1289 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1290 collector_policy()->should_clear_all_soft_refs(); 1291 1292 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1293 1294 { 1295 IsGCActiveMark x; 1296 1297 // Timing 1298 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1299 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps); 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(UseDynamicNumberOfGCThreads || 1457 workers()->active_workers() == workers()->total_workers(), 1458 "Unless dynamic should use total workers"); 1459 // Use the most recent number of active workers 1460 assert(workers()->active_workers() > 0, 1461 "Active workers not properly set"); 1462 set_par_threads(workers()->active_workers()); 1463 workers()->run_task(&rebuild_rs_task); 1464 set_par_threads(0); 1465 } else { 1466 RebuildRSOutOfRegionClosure rebuild_rs(this); 1467 heap_region_iterate(&rebuild_rs); 1468 } 1469 1470 // Rebuild the strong code root lists for each region 1471 rebuild_strong_code_roots(); 1472 1473 if (true) { // FIXME 1474 MetaspaceGC::compute_new_size(); 1475 } 1476 1477 #ifdef TRACESPINNING 1478 ParallelTaskTerminator::print_termination_counts(); 1479 #endif 1480 1481 // Discard all rset updates 1482 JavaThread::dirty_card_queue_set().abandon_logs(); 1483 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1484 1485 _young_list->reset_sampled_info(); 1486 // At this point there should be no regions in the 1487 // entire heap tagged as young. 1488 assert(check_young_list_empty(true /* check_heap */), 1489 "young list should be empty at this point"); 1490 1491 // Update the number of full collections that have been completed. 1492 increment_old_marking_cycles_completed(false /* concurrent */); 1493 1494 _hrm.verify_optional(); 1495 verify_region_sets_optional(); 1496 1497 verify_after_gc(); 1498 1499 // Clear the previous marking bitmap, if needed for bitmap verification. 1500 // Note we cannot do this when we clear the next marking bitmap in 1501 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1502 // objects marked during a full GC against the previous bitmap. 1503 // But we need to clear it before calling check_bitmaps below since 1504 // the full GC has compacted objects and updated TAMS but not updated 1505 // the prev bitmap. 1506 if (G1VerifyBitmaps) { 1507 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1508 } 1509 check_bitmaps("Full GC End"); 1510 1511 // Start a new incremental collection set for the next pause 1512 assert(g1_policy()->collection_set() == NULL, "must be"); 1513 g1_policy()->start_incremental_cset_building(); 1514 1515 clear_cset_fast_test(); 1516 1517 _allocator->init_mutator_alloc_region(); 1518 1519 double end = os::elapsedTime(); 1520 g1_policy()->record_full_collection_end(); 1521 1522 if (G1Log::fine()) { 1523 g1_policy()->print_heap_transition(); 1524 } 1525 1526 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1527 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1528 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1529 // before any GC notifications are raised. 1530 g1mm()->update_sizes(); 1531 1532 gc_epilogue(true); 1533 } 1534 1535 if (G1Log::finer()) { 1536 g1_policy()->print_detailed_heap_transition(true /* full */); 1537 } 1538 1539 print_heap_after_gc(); 1540 trace_heap_after_gc(gc_tracer); 1541 1542 post_full_gc_dump(gc_timer); 1543 1544 gc_timer->register_gc_end(); 1545 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1546 } 1547 1548 return true; 1549 } 1550 1551 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1552 // do_collection() will return whether it succeeded in performing 1553 // the GC. Currently, there is no facility on the 1554 // do_full_collection() API to notify the caller than the collection 1555 // did not succeed (e.g., because it was locked out by the GC 1556 // locker). So, right now, we'll ignore the return value. 1557 bool dummy = do_collection(true, /* explicit_gc */ 1558 clear_all_soft_refs, 1559 0 /* word_size */); 1560 } 1561 1562 // This code is mostly copied from TenuredGeneration. 1563 void 1564 G1CollectedHeap:: 1565 resize_if_necessary_after_full_collection(size_t word_size) { 1566 // Include the current allocation, if any, and bytes that will be 1567 // pre-allocated to support collections, as "used". 1568 const size_t used_after_gc = used(); 1569 const size_t capacity_after_gc = capacity(); 1570 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1571 1572 // This is enforced in arguments.cpp. 1573 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1574 "otherwise the code below doesn't make sense"); 1575 1576 // We don't have floating point command-line arguments 1577 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1578 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1579 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1580 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1581 1582 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1583 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1584 1585 // We have to be careful here as these two calculations can overflow 1586 // 32-bit size_t's. 1587 double used_after_gc_d = (double) used_after_gc; 1588 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1589 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1590 1591 // Let's make sure that they are both under the max heap size, which 1592 // by default will make them fit into a size_t. 1593 double desired_capacity_upper_bound = (double) max_heap_size; 1594 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1595 desired_capacity_upper_bound); 1596 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1597 desired_capacity_upper_bound); 1598 1599 // We can now safely turn them into size_t's. 1600 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1601 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1602 1603 // This assert only makes sense here, before we adjust them 1604 // with respect to the min and max heap size. 1605 assert(minimum_desired_capacity <= maximum_desired_capacity, 1606 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1607 "maximum_desired_capacity = "SIZE_FORMAT, 1608 minimum_desired_capacity, maximum_desired_capacity)); 1609 1610 // Should not be greater than the heap max size. No need to adjust 1611 // it with respect to the heap min size as it's a lower bound (i.e., 1612 // we'll try to make the capacity larger than it, not smaller). 1613 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1614 // Should not be less than the heap min size. No need to adjust it 1615 // with respect to the heap max size as it's an upper bound (i.e., 1616 // we'll try to make the capacity smaller than it, not greater). 1617 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1618 1619 if (capacity_after_gc < minimum_desired_capacity) { 1620 // Don't expand unless it's significant 1621 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1622 ergo_verbose4(ErgoHeapSizing, 1623 "attempt heap expansion", 1624 ergo_format_reason("capacity lower than " 1625 "min desired capacity after Full GC") 1626 ergo_format_byte("capacity") 1627 ergo_format_byte("occupancy") 1628 ergo_format_byte_perc("min desired capacity"), 1629 capacity_after_gc, used_after_gc, 1630 minimum_desired_capacity, (double) MinHeapFreeRatio); 1631 expand(expand_bytes); 1632 1633 // No expansion, now see if we want to shrink 1634 } else if (capacity_after_gc > maximum_desired_capacity) { 1635 // Capacity too large, compute shrinking size 1636 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1637 ergo_verbose4(ErgoHeapSizing, 1638 "attempt heap shrinking", 1639 ergo_format_reason("capacity higher than " 1640 "max desired capacity after Full GC") 1641 ergo_format_byte("capacity") 1642 ergo_format_byte("occupancy") 1643 ergo_format_byte_perc("max desired capacity"), 1644 capacity_after_gc, used_after_gc, 1645 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1646 shrink(shrink_bytes); 1647 } 1648 } 1649 1650 1651 HeapWord* 1652 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1653 AllocationContext_t context, 1654 bool* succeeded) { 1655 assert_at_safepoint(true /* should_be_vm_thread */); 1656 1657 *succeeded = true; 1658 // Let's attempt the allocation first. 1659 HeapWord* result = 1660 attempt_allocation_at_safepoint(word_size, 1661 context, 1662 false /* expect_null_mutator_alloc_region */); 1663 if (result != NULL) { 1664 assert(*succeeded, "sanity"); 1665 return result; 1666 } 1667 1668 // In a G1 heap, we're supposed to keep allocation from failing by 1669 // incremental pauses. Therefore, at least for now, we'll favor 1670 // expansion over collection. (This might change in the future if we can 1671 // do something smarter than full collection to satisfy a failed alloc.) 1672 result = expand_and_allocate(word_size, context); 1673 if (result != NULL) { 1674 assert(*succeeded, "sanity"); 1675 return result; 1676 } 1677 1678 // Expansion didn't work, we'll try to do a Full GC. 1679 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1680 false, /* clear_all_soft_refs */ 1681 word_size); 1682 if (!gc_succeeded) { 1683 *succeeded = false; 1684 return NULL; 1685 } 1686 1687 // Retry the allocation 1688 result = attempt_allocation_at_safepoint(word_size, 1689 context, 1690 true /* expect_null_mutator_alloc_region */); 1691 if (result != NULL) { 1692 assert(*succeeded, "sanity"); 1693 return result; 1694 } 1695 1696 // Then, try a Full GC that will collect all soft references. 1697 gc_succeeded = do_collection(false, /* explicit_gc */ 1698 true, /* clear_all_soft_refs */ 1699 word_size); 1700 if (!gc_succeeded) { 1701 *succeeded = false; 1702 return NULL; 1703 } 1704 1705 // Retry the allocation once more 1706 result = attempt_allocation_at_safepoint(word_size, 1707 context, 1708 true /* expect_null_mutator_alloc_region */); 1709 if (result != NULL) { 1710 assert(*succeeded, "sanity"); 1711 return result; 1712 } 1713 1714 assert(!collector_policy()->should_clear_all_soft_refs(), 1715 "Flag should have been handled and cleared prior to this point"); 1716 1717 // What else? We might try synchronous finalization later. If the total 1718 // space available is large enough for the allocation, then a more 1719 // complete compaction phase than we've tried so far might be 1720 // appropriate. 1721 assert(*succeeded, "sanity"); 1722 return NULL; 1723 } 1724 1725 // Attempting to expand the heap sufficiently 1726 // to support an allocation of the given "word_size". If 1727 // successful, perform the allocation and return the address of the 1728 // allocated block, or else "NULL". 1729 1730 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1731 assert_at_safepoint(true /* should_be_vm_thread */); 1732 1733 verify_region_sets_optional(); 1734 1735 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1736 ergo_verbose1(ErgoHeapSizing, 1737 "attempt heap expansion", 1738 ergo_format_reason("allocation request failed") 1739 ergo_format_byte("allocation request"), 1740 word_size * HeapWordSize); 1741 if (expand(expand_bytes)) { 1742 _hrm.verify_optional(); 1743 verify_region_sets_optional(); 1744 return attempt_allocation_at_safepoint(word_size, 1745 context, 1746 false /* expect_null_mutator_alloc_region */); 1747 } 1748 return NULL; 1749 } 1750 1751 bool G1CollectedHeap::expand(size_t expand_bytes) { 1752 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1753 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1754 HeapRegion::GrainBytes); 1755 ergo_verbose2(ErgoHeapSizing, 1756 "expand the heap", 1757 ergo_format_byte("requested expansion amount") 1758 ergo_format_byte("attempted expansion amount"), 1759 expand_bytes, aligned_expand_bytes); 1760 1761 if (is_maximal_no_gc()) { 1762 ergo_verbose0(ErgoHeapSizing, 1763 "did not expand the heap", 1764 ergo_format_reason("heap already fully expanded")); 1765 return false; 1766 } 1767 1768 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1769 assert(regions_to_expand > 0, "Must expand by at least one region"); 1770 1771 uint expanded_by = _hrm.expand_by(regions_to_expand); 1772 1773 if (expanded_by > 0) { 1774 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1775 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1776 g1_policy()->record_new_heap_size(num_regions()); 1777 } else { 1778 ergo_verbose0(ErgoHeapSizing, 1779 "did not expand the heap", 1780 ergo_format_reason("heap expansion operation failed")); 1781 // The expansion of the virtual storage space was unsuccessful. 1782 // Let's see if it was because we ran out of swap. 1783 if (G1ExitOnExpansionFailure && 1784 _hrm.available() >= regions_to_expand) { 1785 // We had head room... 1786 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1787 } 1788 } 1789 return regions_to_expand > 0; 1790 } 1791 1792 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1793 size_t aligned_shrink_bytes = 1794 ReservedSpace::page_align_size_down(shrink_bytes); 1795 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1796 HeapRegion::GrainBytes); 1797 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1798 1799 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1800 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1801 1802 ergo_verbose3(ErgoHeapSizing, 1803 "shrink the heap", 1804 ergo_format_byte("requested shrinking amount") 1805 ergo_format_byte("aligned shrinking amount") 1806 ergo_format_byte("attempted shrinking amount"), 1807 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1808 if (num_regions_removed > 0) { 1809 g1_policy()->record_new_heap_size(num_regions()); 1810 } else { 1811 ergo_verbose0(ErgoHeapSizing, 1812 "did not shrink the heap", 1813 ergo_format_reason("heap shrinking operation failed")); 1814 } 1815 } 1816 1817 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1818 verify_region_sets_optional(); 1819 1820 // We should only reach here at the end of a Full GC which means we 1821 // should not not be holding to any GC alloc regions. The method 1822 // below will make sure of that and do any remaining clean up. 1823 _allocator->abandon_gc_alloc_regions(); 1824 1825 // Instead of tearing down / rebuilding the free lists here, we 1826 // could instead use the remove_all_pending() method on free_list to 1827 // remove only the ones that we need to remove. 1828 tear_down_region_sets(true /* free_list_only */); 1829 shrink_helper(shrink_bytes); 1830 rebuild_region_sets(true /* free_list_only */); 1831 1832 _hrm.verify_optional(); 1833 verify_region_sets_optional(); 1834 } 1835 1836 // Public methods. 1837 1838 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1839 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1840 #endif // _MSC_VER 1841 1842 1843 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1844 SharedHeap(policy_), 1845 _g1_policy(policy_), 1846 _dirty_card_queue_set(false), 1847 _into_cset_dirty_card_queue_set(false), 1848 _is_alive_closure_cm(this), 1849 _is_alive_closure_stw(this), 1850 _ref_processor_cm(NULL), 1851 _ref_processor_stw(NULL), 1852 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1853 _bot_shared(NULL), 1854 _evac_failure_scan_stack(NULL), 1855 _mark_in_progress(false), 1856 _cg1r(NULL), 1857 _g1mm(NULL), 1858 _refine_cte_cl(NULL), 1859 _full_collection(false), 1860 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1861 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1862 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1863 _humongous_is_live(), 1864 _has_humongous_reclaim_candidates(false), 1865 _free_regions_coming(false), 1866 _young_list(new YoungList(this)), 1867 _gc_time_stamp(0), 1868 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1869 _old_plab_stats(OldPLABSize, PLABWeight), 1870 _expand_heap_after_alloc_failure(true), 1871 _surviving_young_words(NULL), 1872 _old_marking_cycles_started(0), 1873 _old_marking_cycles_completed(0), 1874 _concurrent_cycle_started(false), 1875 _heap_summary_sent(false), 1876 _in_cset_fast_test(), 1877 _dirty_cards_region_list(NULL), 1878 _worker_cset_start_region(NULL), 1879 _worker_cset_start_region_time_stamp(NULL), 1880 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1881 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1882 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1883 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1884 1885 _g1h = this; 1886 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1887 vm_exit_during_initialization("Failed necessary allocation."); 1888 } 1889 1890 _allocator = G1Allocator::create_allocator(_g1h); 1891 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1892 1893 int n_queues = MAX2((int)ParallelGCThreads, 1); 1894 _task_queues = new RefToScanQueueSet(n_queues); 1895 1896 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1897 assert(n_rem_sets > 0, "Invariant."); 1898 1899 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1900 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1901 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1902 1903 for (int i = 0; i < n_queues; i++) { 1904 RefToScanQueue* q = new RefToScanQueue(); 1905 q->initialize(); 1906 _task_queues->register_queue(i, q); 1907 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1908 } 1909 clear_cset_start_regions(); 1910 1911 // Initialize the G1EvacuationFailureALot counters and flags. 1912 NOT_PRODUCT(reset_evacuation_should_fail();) 1913 1914 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1915 } 1916 1917 jint G1CollectedHeap::initialize() { 1918 CollectedHeap::pre_initialize(); 1919 os::enable_vtime(); 1920 1921 G1Log::init(); 1922 1923 // Necessary to satisfy locking discipline assertions. 1924 1925 MutexLocker x(Heap_lock); 1926 1927 // We have to initialize the printer before committing the heap, as 1928 // it will be used then. 1929 _hr_printer.set_active(G1PrintHeapRegions); 1930 1931 // While there are no constraints in the GC code that HeapWordSize 1932 // be any particular value, there are multiple other areas in the 1933 // system which believe this to be true (e.g. oop->object_size in some 1934 // cases incorrectly returns the size in wordSize units rather than 1935 // HeapWordSize). 1936 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1937 1938 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1939 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1940 size_t heap_alignment = collector_policy()->heap_alignment(); 1941 1942 // Ensure that the sizes are properly aligned. 1943 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1944 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1945 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1946 1947 _refine_cte_cl = new RefineCardTableEntryClosure(); 1948 1949 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl); 1950 1951 // Reserve the maximum. 1952 1953 // When compressed oops are enabled, the preferred heap base 1954 // is calculated by subtracting the requested size from the 1955 // 32Gb boundary and using the result as the base address for 1956 // heap reservation. If the requested size is not aligned to 1957 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1958 // into the ReservedHeapSpace constructor) then the actual 1959 // base of the reserved heap may end up differing from the 1960 // address that was requested (i.e. the preferred heap base). 1961 // If this happens then we could end up using a non-optimal 1962 // compressed oops mode. 1963 1964 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1965 heap_alignment); 1966 1967 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1968 1969 // Create the gen rem set (and barrier set) for the entire reserved region. 1970 _rem_set = collector_policy()->create_rem_set(reserved_region(), 2); 1971 set_barrier_set(rem_set()->bs()); 1972 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) { 1973 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS"); 1974 return JNI_ENOMEM; 1975 } 1976 1977 // Also create a G1 rem set. 1978 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1979 1980 // Carve out the G1 part of the heap. 1981 1982 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1983 G1RegionToSpaceMapper* heap_storage = 1984 G1RegionToSpaceMapper::create_mapper(g1_rs, 1985 UseLargePages ? os::large_page_size() : os::vm_page_size(), 1986 HeapRegion::GrainBytes, 1987 1, 1988 mtJavaHeap); 1989 heap_storage->set_mapping_changed_listener(&_listener); 1990 1991 // Reserve space for the block offset table. We do not support automatic uncommit 1992 // for the card table at this time. BOT only. 1993 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize)); 1994 G1RegionToSpaceMapper* bot_storage = 1995 G1RegionToSpaceMapper::create_mapper(bot_rs, 1996 os::vm_page_size(), 1997 HeapRegion::GrainBytes, 1998 G1BlockOffsetSharedArray::N_bytes, 1999 mtGC); 2000 2001 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 2002 G1RegionToSpaceMapper* cardtable_storage = 2003 G1RegionToSpaceMapper::create_mapper(cardtable_rs, 2004 os::vm_page_size(), 2005 HeapRegion::GrainBytes, 2006 G1BlockOffsetSharedArray::N_bytes, 2007 mtGC); 2008 2009 // Reserve space for the card counts table. 2010 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize)); 2011 G1RegionToSpaceMapper* card_counts_storage = 2012 G1RegionToSpaceMapper::create_mapper(card_counts_rs, 2013 os::vm_page_size(), 2014 HeapRegion::GrainBytes, 2015 G1BlockOffsetSharedArray::N_bytes, 2016 mtGC); 2017 2018 // Reserve space for prev and next bitmap. 2019 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 2020 2021 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size)); 2022 G1RegionToSpaceMapper* prev_bitmap_storage = 2023 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs, 2024 os::vm_page_size(), 2025 HeapRegion::GrainBytes, 2026 CMBitMap::mark_distance(), 2027 mtGC); 2028 2029 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size)); 2030 G1RegionToSpaceMapper* next_bitmap_storage = 2031 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs, 2032 os::vm_page_size(), 2033 HeapRegion::GrainBytes, 2034 CMBitMap::mark_distance(), 2035 mtGC); 2036 2037 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 2038 g1_barrier_set()->initialize(cardtable_storage); 2039 // Do later initialization work for concurrent refinement. 2040 _cg1r->init(card_counts_storage); 2041 2042 // 6843694 - ensure that the maximum region index can fit 2043 // in the remembered set structures. 2044 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2045 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2046 2047 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2048 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2049 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2050 "too many cards per region"); 2051 2052 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 2053 2054 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 2055 2056 _g1h = this; 2057 2058 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes); 2059 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes); 2060 2061 // Create the ConcurrentMark data structure and thread. 2062 // (Must do this late, so that "max_regions" is defined.) 2063 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 2064 if (_cm == NULL || !_cm->completed_initialization()) { 2065 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2066 return JNI_ENOMEM; 2067 } 2068 _cmThread = _cm->cmThread(); 2069 2070 // Initialize the from_card cache structure of HeapRegionRemSet. 2071 HeapRegionRemSet::init_heap(max_regions()); 2072 2073 // Now expand into the initial heap size. 2074 if (!expand(init_byte_size)) { 2075 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2076 return JNI_ENOMEM; 2077 } 2078 2079 // Perform any initialization actions delegated to the policy. 2080 g1_policy()->init(); 2081 2082 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2083 SATB_Q_FL_lock, 2084 G1SATBProcessCompletedThreshold, 2085 Shared_SATB_Q_lock); 2086 2087 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2088 DirtyCardQ_CBL_mon, 2089 DirtyCardQ_FL_lock, 2090 concurrent_g1_refine()->yellow_zone(), 2091 concurrent_g1_refine()->red_zone(), 2092 Shared_DirtyCardQ_lock); 2093 2094 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2095 DirtyCardQ_CBL_mon, 2096 DirtyCardQ_FL_lock, 2097 -1, // never trigger processing 2098 -1, // no limit on length 2099 Shared_DirtyCardQ_lock, 2100 &JavaThread::dirty_card_queue_set()); 2101 2102 // Initialize the card queue set used to hold cards containing 2103 // references into the collection set. 2104 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code 2105 DirtyCardQ_CBL_mon, 2106 DirtyCardQ_FL_lock, 2107 -1, // never trigger processing 2108 -1, // no limit on length 2109 Shared_DirtyCardQ_lock, 2110 &JavaThread::dirty_card_queue_set()); 2111 2112 // In case we're keeping closure specialization stats, initialize those 2113 // counts and that mechanism. 2114 SpecializationStats::clear(); 2115 2116 // Here we allocate the dummy HeapRegion that is required by the 2117 // G1AllocRegion class. 2118 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2119 2120 // We'll re-use the same region whether the alloc region will 2121 // require BOT updates or not and, if it doesn't, then a non-young 2122 // region will complain that it cannot support allocations without 2123 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2124 dummy_region->set_eden(); 2125 // Make sure it's full. 2126 dummy_region->set_top(dummy_region->end()); 2127 G1AllocRegion::setup(this, dummy_region); 2128 2129 _allocator->init_mutator_alloc_region(); 2130 2131 // Do create of the monitoring and management support so that 2132 // values in the heap have been properly initialized. 2133 _g1mm = new G1MonitoringSupport(this); 2134 2135 G1StringDedup::initialize(); 2136 2137 return JNI_OK; 2138 } 2139 2140 void G1CollectedHeap::stop() { 2141 // Stop all concurrent threads. We do this to make sure these threads 2142 // do not continue to execute and access resources (e.g. gclog_or_tty) 2143 // that are destroyed during shutdown. 2144 _cg1r->stop(); 2145 _cmThread->stop(); 2146 if (G1StringDedup::is_enabled()) { 2147 G1StringDedup::stop(); 2148 } 2149 } 2150 2151 void G1CollectedHeap::clear_humongous_is_live_table() { 2152 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true"); 2153 _humongous_is_live.clear(); 2154 } 2155 2156 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2157 return HeapRegion::max_region_size(); 2158 } 2159 2160 void G1CollectedHeap::ref_processing_init() { 2161 // Reference processing in G1 currently works as follows: 2162 // 2163 // * There are two reference processor instances. One is 2164 // used to record and process discovered references 2165 // during concurrent marking; the other is used to 2166 // record and process references during STW pauses 2167 // (both full and incremental). 2168 // * Both ref processors need to 'span' the entire heap as 2169 // the regions in the collection set may be dotted around. 2170 // 2171 // * For the concurrent marking ref processor: 2172 // * Reference discovery is enabled at initial marking. 2173 // * Reference discovery is disabled and the discovered 2174 // references processed etc during remarking. 2175 // * Reference discovery is MT (see below). 2176 // * Reference discovery requires a barrier (see below). 2177 // * Reference processing may or may not be MT 2178 // (depending on the value of ParallelRefProcEnabled 2179 // and ParallelGCThreads). 2180 // * A full GC disables reference discovery by the CM 2181 // ref processor and abandons any entries on it's 2182 // discovered lists. 2183 // 2184 // * For the STW processor: 2185 // * Non MT discovery is enabled at the start of a full GC. 2186 // * Processing and enqueueing during a full GC is non-MT. 2187 // * During a full GC, references are processed after marking. 2188 // 2189 // * Discovery (may or may not be MT) is enabled at the start 2190 // of an incremental evacuation pause. 2191 // * References are processed near the end of a STW evacuation pause. 2192 // * For both types of GC: 2193 // * Discovery is atomic - i.e. not concurrent. 2194 // * Reference discovery will not need a barrier. 2195 2196 SharedHeap::ref_processing_init(); 2197 MemRegion mr = reserved_region(); 2198 2199 // Concurrent Mark ref processor 2200 _ref_processor_cm = 2201 new ReferenceProcessor(mr, // span 2202 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2203 // mt processing 2204 (int) ParallelGCThreads, 2205 // degree of mt processing 2206 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2207 // mt discovery 2208 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2209 // degree of mt discovery 2210 false, 2211 // Reference discovery is not atomic 2212 &_is_alive_closure_cm); 2213 // is alive closure 2214 // (for efficiency/performance) 2215 2216 // STW ref processor 2217 _ref_processor_stw = 2218 new ReferenceProcessor(mr, // span 2219 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2220 // mt processing 2221 MAX2((int)ParallelGCThreads, 1), 2222 // degree of mt processing 2223 (ParallelGCThreads > 1), 2224 // mt discovery 2225 MAX2((int)ParallelGCThreads, 1), 2226 // degree of mt discovery 2227 true, 2228 // Reference discovery is atomic 2229 &_is_alive_closure_stw); 2230 // is alive closure 2231 // (for efficiency/performance) 2232 } 2233 2234 size_t G1CollectedHeap::capacity() const { 2235 return _hrm.length() * HeapRegion::GrainBytes; 2236 } 2237 2238 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2239 assert(!hr->is_continues_humongous(), "pre-condition"); 2240 hr->reset_gc_time_stamp(); 2241 if (hr->is_starts_humongous()) { 2242 uint first_index = hr->hrm_index() + 1; 2243 uint last_index = hr->last_hc_index(); 2244 for (uint i = first_index; i < last_index; i += 1) { 2245 HeapRegion* chr = region_at(i); 2246 assert(chr->is_continues_humongous(), "sanity"); 2247 chr->reset_gc_time_stamp(); 2248 } 2249 } 2250 } 2251 2252 #ifndef PRODUCT 2253 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2254 private: 2255 unsigned _gc_time_stamp; 2256 bool _failures; 2257 2258 public: 2259 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2260 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2261 2262 virtual bool doHeapRegion(HeapRegion* hr) { 2263 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2264 if (_gc_time_stamp != region_gc_time_stamp) { 2265 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2266 "expected %d", HR_FORMAT_PARAMS(hr), 2267 region_gc_time_stamp, _gc_time_stamp); 2268 _failures = true; 2269 } 2270 return false; 2271 } 2272 2273 bool failures() { return _failures; } 2274 }; 2275 2276 void G1CollectedHeap::check_gc_time_stamps() { 2277 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2278 heap_region_iterate(&cl); 2279 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2280 } 2281 #endif // PRODUCT 2282 2283 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2284 DirtyCardQueue* into_cset_dcq, 2285 bool concurrent, 2286 uint worker_i) { 2287 // Clean cards in the hot card cache 2288 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2289 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2290 2291 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2292 int n_completed_buffers = 0; 2293 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2294 n_completed_buffers++; 2295 } 2296 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2297 dcqs.clear_n_completed_buffers(); 2298 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2299 } 2300 2301 2302 // Computes the sum of the storage used by the various regions. 2303 size_t G1CollectedHeap::used() const { 2304 return _allocator->used(); 2305 } 2306 2307 size_t G1CollectedHeap::used_unlocked() const { 2308 return _allocator->used_unlocked(); 2309 } 2310 2311 class SumUsedClosure: public HeapRegionClosure { 2312 size_t _used; 2313 public: 2314 SumUsedClosure() : _used(0) {} 2315 bool doHeapRegion(HeapRegion* r) { 2316 if (!r->is_continues_humongous()) { 2317 _used += r->used(); 2318 } 2319 return false; 2320 } 2321 size_t result() { return _used; } 2322 }; 2323 2324 size_t G1CollectedHeap::recalculate_used() const { 2325 double recalculate_used_start = os::elapsedTime(); 2326 2327 SumUsedClosure blk; 2328 heap_region_iterate(&blk); 2329 2330 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2331 return blk.result(); 2332 } 2333 2334 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2335 switch (cause) { 2336 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2337 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2338 case GCCause::_g1_humongous_allocation: return true; 2339 default: return false; 2340 } 2341 } 2342 2343 #ifndef PRODUCT 2344 void G1CollectedHeap::allocate_dummy_regions() { 2345 // Let's fill up most of the region 2346 size_t word_size = HeapRegion::GrainWords - 1024; 2347 // And as a result the region we'll allocate will be humongous. 2348 guarantee(is_humongous(word_size), "sanity"); 2349 2350 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2351 // Let's use the existing mechanism for the allocation 2352 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2353 AllocationContext::system()); 2354 if (dummy_obj != NULL) { 2355 MemRegion mr(dummy_obj, word_size); 2356 CollectedHeap::fill_with_object(mr); 2357 } else { 2358 // If we can't allocate once, we probably cannot allocate 2359 // again. Let's get out of the loop. 2360 break; 2361 } 2362 } 2363 } 2364 #endif // !PRODUCT 2365 2366 void G1CollectedHeap::increment_old_marking_cycles_started() { 2367 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2368 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2369 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2370 _old_marking_cycles_started, _old_marking_cycles_completed)); 2371 2372 _old_marking_cycles_started++; 2373 } 2374 2375 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2376 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2377 2378 // We assume that if concurrent == true, then the caller is a 2379 // concurrent thread that was joined the Suspendible Thread 2380 // Set. If there's ever a cheap way to check this, we should add an 2381 // assert here. 2382 2383 // Given that this method is called at the end of a Full GC or of a 2384 // concurrent cycle, and those can be nested (i.e., a Full GC can 2385 // interrupt a concurrent cycle), the number of full collections 2386 // completed should be either one (in the case where there was no 2387 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2388 // behind the number of full collections started. 2389 2390 // This is the case for the inner caller, i.e. a Full GC. 2391 assert(concurrent || 2392 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2393 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2394 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2395 "is inconsistent with _old_marking_cycles_completed = %u", 2396 _old_marking_cycles_started, _old_marking_cycles_completed)); 2397 2398 // This is the case for the outer caller, i.e. the concurrent cycle. 2399 assert(!concurrent || 2400 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2401 err_msg("for outer caller (concurrent cycle): " 2402 "_old_marking_cycles_started = %u " 2403 "is inconsistent with _old_marking_cycles_completed = %u", 2404 _old_marking_cycles_started, _old_marking_cycles_completed)); 2405 2406 _old_marking_cycles_completed += 1; 2407 2408 // We need to clear the "in_progress" flag in the CM thread before 2409 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2410 // is set) so that if a waiter requests another System.gc() it doesn't 2411 // incorrectly see that a marking cycle is still in progress. 2412 if (concurrent) { 2413 _cmThread->clear_in_progress(); 2414 } 2415 2416 // This notify_all() will ensure that a thread that called 2417 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2418 // and it's waiting for a full GC to finish will be woken up. It is 2419 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2420 FullGCCount_lock->notify_all(); 2421 } 2422 2423 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2424 _concurrent_cycle_started = true; 2425 _gc_timer_cm->register_gc_start(start_time); 2426 2427 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2428 trace_heap_before_gc(_gc_tracer_cm); 2429 } 2430 2431 void G1CollectedHeap::register_concurrent_cycle_end() { 2432 if (_concurrent_cycle_started) { 2433 if (_cm->has_aborted()) { 2434 _gc_tracer_cm->report_concurrent_mode_failure(); 2435 } 2436 2437 _gc_timer_cm->register_gc_end(); 2438 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2439 2440 // Clear state variables to prepare for the next concurrent cycle. 2441 _concurrent_cycle_started = false; 2442 _heap_summary_sent = false; 2443 } 2444 } 2445 2446 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2447 if (_concurrent_cycle_started) { 2448 // This function can be called when: 2449 // the cleanup pause is run 2450 // the concurrent cycle is aborted before the cleanup pause. 2451 // the concurrent cycle is aborted after the cleanup pause, 2452 // but before the concurrent cycle end has been registered. 2453 // Make sure that we only send the heap information once. 2454 if (!_heap_summary_sent) { 2455 trace_heap_after_gc(_gc_tracer_cm); 2456 _heap_summary_sent = true; 2457 } 2458 } 2459 } 2460 2461 G1YCType G1CollectedHeap::yc_type() { 2462 bool is_young = g1_policy()->gcs_are_young(); 2463 bool is_initial_mark = g1_policy()->during_initial_mark_pause(); 2464 bool is_during_mark = mark_in_progress(); 2465 2466 if (is_initial_mark) { 2467 return InitialMark; 2468 } else if (is_during_mark) { 2469 return DuringMark; 2470 } else if (is_young) { 2471 return Normal; 2472 } else { 2473 return Mixed; 2474 } 2475 } 2476 2477 void G1CollectedHeap::collect(GCCause::Cause cause) { 2478 assert_heap_not_locked(); 2479 2480 unsigned int gc_count_before; 2481 unsigned int old_marking_count_before; 2482 bool retry_gc; 2483 2484 do { 2485 retry_gc = false; 2486 2487 { 2488 MutexLocker ml(Heap_lock); 2489 2490 // Read the GC count while holding the Heap_lock 2491 gc_count_before = total_collections(); 2492 old_marking_count_before = _old_marking_cycles_started; 2493 } 2494 2495 if (should_do_concurrent_full_gc(cause)) { 2496 // Schedule an initial-mark evacuation pause that will start a 2497 // concurrent cycle. We're setting word_size to 0 which means that 2498 // we are not requesting a post-GC allocation. 2499 VM_G1IncCollectionPause op(gc_count_before, 2500 0, /* word_size */ 2501 true, /* should_initiate_conc_mark */ 2502 g1_policy()->max_pause_time_ms(), 2503 cause); 2504 op.set_allocation_context(AllocationContext::current()); 2505 2506 VMThread::execute(&op); 2507 if (!op.pause_succeeded()) { 2508 if (old_marking_count_before == _old_marking_cycles_started) { 2509 retry_gc = op.should_retry_gc(); 2510 } else { 2511 // A Full GC happened while we were trying to schedule the 2512 // initial-mark GC. No point in starting a new cycle given 2513 // that the whole heap was collected anyway. 2514 } 2515 2516 if (retry_gc) { 2517 if (GC_locker::is_active_and_needs_gc()) { 2518 GC_locker::stall_until_clear(); 2519 } 2520 } 2521 } 2522 } else { 2523 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2524 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2525 2526 // Schedule a standard evacuation pause. We're setting word_size 2527 // to 0 which means that we are not requesting a post-GC allocation. 2528 VM_G1IncCollectionPause op(gc_count_before, 2529 0, /* word_size */ 2530 false, /* should_initiate_conc_mark */ 2531 g1_policy()->max_pause_time_ms(), 2532 cause); 2533 VMThread::execute(&op); 2534 } else { 2535 // Schedule a Full GC. 2536 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause); 2537 VMThread::execute(&op); 2538 } 2539 } 2540 } while (retry_gc); 2541 } 2542 2543 bool G1CollectedHeap::is_in(const void* p) const { 2544 if (_hrm.reserved().contains(p)) { 2545 // Given that we know that p is in the reserved space, 2546 // heap_region_containing_raw() should successfully 2547 // return the containing region. 2548 HeapRegion* hr = heap_region_containing_raw(p); 2549 return hr->is_in(p); 2550 } else { 2551 return false; 2552 } 2553 } 2554 2555 #ifdef ASSERT 2556 bool G1CollectedHeap::is_in_exact(const void* p) const { 2557 bool contains = reserved_region().contains(p); 2558 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2559 if (contains && available) { 2560 return true; 2561 } else { 2562 return false; 2563 } 2564 } 2565 #endif 2566 2567 // Iteration functions. 2568 2569 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2570 2571 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2572 ExtendedOopClosure* _cl; 2573 public: 2574 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2575 bool doHeapRegion(HeapRegion* r) { 2576 if (!r->is_continues_humongous()) { 2577 r->oop_iterate(_cl); 2578 } 2579 return false; 2580 } 2581 }; 2582 2583 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2584 IterateOopClosureRegionClosure blk(cl); 2585 heap_region_iterate(&blk); 2586 } 2587 2588 // Iterates an ObjectClosure over all objects within a HeapRegion. 2589 2590 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2591 ObjectClosure* _cl; 2592 public: 2593 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2594 bool doHeapRegion(HeapRegion* r) { 2595 if (!r->is_continues_humongous()) { 2596 r->object_iterate(_cl); 2597 } 2598 return false; 2599 } 2600 }; 2601 2602 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2603 IterateObjectClosureRegionClosure blk(cl); 2604 heap_region_iterate(&blk); 2605 } 2606 2607 // Calls a SpaceClosure on a HeapRegion. 2608 2609 class SpaceClosureRegionClosure: public HeapRegionClosure { 2610 SpaceClosure* _cl; 2611 public: 2612 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2613 bool doHeapRegion(HeapRegion* r) { 2614 _cl->do_space(r); 2615 return false; 2616 } 2617 }; 2618 2619 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2620 SpaceClosureRegionClosure blk(cl); 2621 heap_region_iterate(&blk); 2622 } 2623 2624 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2625 _hrm.iterate(cl); 2626 } 2627 2628 void 2629 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2630 uint worker_id, 2631 HeapRegionClaimer *hrclaimer) const { 2632 _hrm.par_iterate(cl, worker_id, hrclaimer); 2633 } 2634 2635 // Clear the cached CSet starting regions and (more importantly) 2636 // the time stamps. Called when we reset the GC time stamp. 2637 void G1CollectedHeap::clear_cset_start_regions() { 2638 assert(_worker_cset_start_region != NULL, "sanity"); 2639 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2640 2641 int n_queues = MAX2((int)ParallelGCThreads, 1); 2642 for (int i = 0; i < n_queues; i++) { 2643 _worker_cset_start_region[i] = NULL; 2644 _worker_cset_start_region_time_stamp[i] = 0; 2645 } 2646 } 2647 2648 // Given the id of a worker, obtain or calculate a suitable 2649 // starting region for iterating over the current collection set. 2650 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2651 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2652 2653 HeapRegion* result = NULL; 2654 unsigned gc_time_stamp = get_gc_time_stamp(); 2655 2656 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2657 // Cached starting region for current worker was set 2658 // during the current pause - so it's valid. 2659 // Note: the cached starting heap region may be NULL 2660 // (when the collection set is empty). 2661 result = _worker_cset_start_region[worker_i]; 2662 assert(result == NULL || result->in_collection_set(), "sanity"); 2663 return result; 2664 } 2665 2666 // The cached entry was not valid so let's calculate 2667 // a suitable starting heap region for this worker. 2668 2669 // We want the parallel threads to start their collection 2670 // set iteration at different collection set regions to 2671 // avoid contention. 2672 // If we have: 2673 // n collection set regions 2674 // p threads 2675 // Then thread t will start at region floor ((t * n) / p) 2676 2677 result = g1_policy()->collection_set(); 2678 if (G1CollectedHeap::use_parallel_gc_threads()) { 2679 uint cs_size = g1_policy()->cset_region_length(); 2680 uint active_workers = workers()->active_workers(); 2681 assert(UseDynamicNumberOfGCThreads || 2682 active_workers == workers()->total_workers(), 2683 "Unless dynamic should use total workers"); 2684 2685 uint end_ind = (cs_size * worker_i) / active_workers; 2686 uint start_ind = 0; 2687 2688 if (worker_i > 0 && 2689 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2690 // Previous workers starting region is valid 2691 // so let's iterate from there 2692 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2693 result = _worker_cset_start_region[worker_i - 1]; 2694 } 2695 2696 for (uint i = start_ind; i < end_ind; i++) { 2697 result = result->next_in_collection_set(); 2698 } 2699 } 2700 2701 // Note: the calculated starting heap region may be NULL 2702 // (when the collection set is empty). 2703 assert(result == NULL || result->in_collection_set(), "sanity"); 2704 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2705 "should be updated only once per pause"); 2706 _worker_cset_start_region[worker_i] = result; 2707 OrderAccess::storestore(); 2708 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2709 return result; 2710 } 2711 2712 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2713 HeapRegion* r = g1_policy()->collection_set(); 2714 while (r != NULL) { 2715 HeapRegion* next = r->next_in_collection_set(); 2716 if (cl->doHeapRegion(r)) { 2717 cl->incomplete(); 2718 return; 2719 } 2720 r = next; 2721 } 2722 } 2723 2724 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2725 HeapRegionClosure *cl) { 2726 if (r == NULL) { 2727 // The CSet is empty so there's nothing to do. 2728 return; 2729 } 2730 2731 assert(r->in_collection_set(), 2732 "Start region must be a member of the collection set."); 2733 HeapRegion* cur = r; 2734 while (cur != NULL) { 2735 HeapRegion* next = cur->next_in_collection_set(); 2736 if (cl->doHeapRegion(cur) && false) { 2737 cl->incomplete(); 2738 return; 2739 } 2740 cur = next; 2741 } 2742 cur = g1_policy()->collection_set(); 2743 while (cur != r) { 2744 HeapRegion* next = cur->next_in_collection_set(); 2745 if (cl->doHeapRegion(cur) && false) { 2746 cl->incomplete(); 2747 return; 2748 } 2749 cur = next; 2750 } 2751 } 2752 2753 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2754 HeapRegion* result = _hrm.next_region_in_heap(from); 2755 while (result != NULL && result->is_humongous()) { 2756 result = _hrm.next_region_in_heap(result); 2757 } 2758 return result; 2759 } 2760 2761 Space* G1CollectedHeap::space_containing(const void* addr) const { 2762 return heap_region_containing(addr); 2763 } 2764 2765 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2766 Space* sp = space_containing(addr); 2767 return sp->block_start(addr); 2768 } 2769 2770 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2771 Space* sp = space_containing(addr); 2772 return sp->block_size(addr); 2773 } 2774 2775 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2776 Space* sp = space_containing(addr); 2777 return sp->block_is_obj(addr); 2778 } 2779 2780 bool G1CollectedHeap::supports_tlab_allocation() const { 2781 return true; 2782 } 2783 2784 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2785 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2786 } 2787 2788 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2789 return young_list()->eden_used_bytes(); 2790 } 2791 2792 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2793 // must be smaller than the humongous object limit. 2794 size_t G1CollectedHeap::max_tlab_size() const { 2795 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment); 2796 } 2797 2798 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2799 // Return the remaining space in the cur alloc region, but not less than 2800 // the min TLAB size. 2801 2802 // Also, this value can be at most the humongous object threshold, 2803 // since we can't allow tlabs to grow big enough to accommodate 2804 // humongous objects. 2805 2806 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get(); 2807 size_t max_tlab = max_tlab_size() * wordSize; 2808 if (hr == NULL) { 2809 return max_tlab; 2810 } else { 2811 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab); 2812 } 2813 } 2814 2815 size_t G1CollectedHeap::max_capacity() const { 2816 return _hrm.reserved().byte_size(); 2817 } 2818 2819 jlong G1CollectedHeap::millis_since_last_gc() { 2820 // assert(false, "NYI"); 2821 return 0; 2822 } 2823 2824 void G1CollectedHeap::prepare_for_verify() { 2825 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2826 ensure_parsability(false); 2827 } 2828 g1_rem_set()->prepare_for_verify(); 2829 } 2830 2831 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2832 VerifyOption vo) { 2833 switch (vo) { 2834 case VerifyOption_G1UsePrevMarking: 2835 return hr->obj_allocated_since_prev_marking(obj); 2836 case VerifyOption_G1UseNextMarking: 2837 return hr->obj_allocated_since_next_marking(obj); 2838 case VerifyOption_G1UseMarkWord: 2839 return false; 2840 default: 2841 ShouldNotReachHere(); 2842 } 2843 return false; // keep some compilers happy 2844 } 2845 2846 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2847 switch (vo) { 2848 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2849 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2850 case VerifyOption_G1UseMarkWord: return NULL; 2851 default: ShouldNotReachHere(); 2852 } 2853 return NULL; // keep some compilers happy 2854 } 2855 2856 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2857 switch (vo) { 2858 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2859 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2860 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2861 default: ShouldNotReachHere(); 2862 } 2863 return false; // keep some compilers happy 2864 } 2865 2866 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2867 switch (vo) { 2868 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2869 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2870 case VerifyOption_G1UseMarkWord: return "NONE"; 2871 default: ShouldNotReachHere(); 2872 } 2873 return NULL; // keep some compilers happy 2874 } 2875 2876 class VerifyRootsClosure: public OopClosure { 2877 private: 2878 G1CollectedHeap* _g1h; 2879 VerifyOption _vo; 2880 bool _failures; 2881 public: 2882 // _vo == UsePrevMarking -> use "prev" marking information, 2883 // _vo == UseNextMarking -> use "next" marking information, 2884 // _vo == UseMarkWord -> use mark word from object header. 2885 VerifyRootsClosure(VerifyOption vo) : 2886 _g1h(G1CollectedHeap::heap()), 2887 _vo(vo), 2888 _failures(false) { } 2889 2890 bool failures() { return _failures; } 2891 2892 template <class T> void do_oop_nv(T* p) { 2893 T heap_oop = oopDesc::load_heap_oop(p); 2894 if (!oopDesc::is_null(heap_oop)) { 2895 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2896 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2897 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 2898 "points to dead obj "PTR_FORMAT, p, (void*) obj); 2899 if (_vo == VerifyOption_G1UseMarkWord) { 2900 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 2901 } 2902 obj->print_on(gclog_or_tty); 2903 _failures = true; 2904 } 2905 } 2906 } 2907 2908 void do_oop(oop* p) { do_oop_nv(p); } 2909 void do_oop(narrowOop* p) { do_oop_nv(p); } 2910 }; 2911 2912 class G1VerifyCodeRootOopClosure: public OopClosure { 2913 G1CollectedHeap* _g1h; 2914 OopClosure* _root_cl; 2915 nmethod* _nm; 2916 VerifyOption _vo; 2917 bool _failures; 2918 2919 template <class T> void do_oop_work(T* p) { 2920 // First verify that this root is live 2921 _root_cl->do_oop(p); 2922 2923 if (!G1VerifyHeapRegionCodeRoots) { 2924 // We're not verifying the code roots attached to heap region. 2925 return; 2926 } 2927 2928 // Don't check the code roots during marking verification in a full GC 2929 if (_vo == VerifyOption_G1UseMarkWord) { 2930 return; 2931 } 2932 2933 // Now verify that the current nmethod (which contains p) is 2934 // in the code root list of the heap region containing the 2935 // object referenced by p. 2936 2937 T heap_oop = oopDesc::load_heap_oop(p); 2938 if (!oopDesc::is_null(heap_oop)) { 2939 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2940 2941 // Now fetch the region containing the object 2942 HeapRegion* hr = _g1h->heap_region_containing(obj); 2943 HeapRegionRemSet* hrrs = hr->rem_set(); 2944 // Verify that the strong code root list for this region 2945 // contains the nmethod 2946 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2947 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" " 2948 "from nmethod "PTR_FORMAT" not in strong " 2949 "code roots for region ["PTR_FORMAT","PTR_FORMAT")", 2950 p, _nm, hr->bottom(), hr->end()); 2951 _failures = true; 2952 } 2953 } 2954 } 2955 2956 public: 2957 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2958 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2959 2960 void do_oop(oop* p) { do_oop_work(p); } 2961 void do_oop(narrowOop* p) { do_oop_work(p); } 2962 2963 void set_nmethod(nmethod* nm) { _nm = nm; } 2964 bool failures() { return _failures; } 2965 }; 2966 2967 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2968 G1VerifyCodeRootOopClosure* _oop_cl; 2969 2970 public: 2971 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2972 _oop_cl(oop_cl) {} 2973 2974 void do_code_blob(CodeBlob* cb) { 2975 nmethod* nm = cb->as_nmethod_or_null(); 2976 if (nm != NULL) { 2977 _oop_cl->set_nmethod(nm); 2978 nm->oops_do(_oop_cl); 2979 } 2980 } 2981 }; 2982 2983 class YoungRefCounterClosure : public OopClosure { 2984 G1CollectedHeap* _g1h; 2985 int _count; 2986 public: 2987 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2988 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2989 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2990 2991 int count() { return _count; } 2992 void reset_count() { _count = 0; }; 2993 }; 2994 2995 class VerifyKlassClosure: public KlassClosure { 2996 YoungRefCounterClosure _young_ref_counter_closure; 2997 OopClosure *_oop_closure; 2998 public: 2999 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3000 void do_klass(Klass* k) { 3001 k->oops_do(_oop_closure); 3002 3003 _young_ref_counter_closure.reset_count(); 3004 k->oops_do(&_young_ref_counter_closure); 3005 if (_young_ref_counter_closure.count() > 0) { 3006 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k)); 3007 } 3008 } 3009 }; 3010 3011 class VerifyLivenessOopClosure: public OopClosure { 3012 G1CollectedHeap* _g1h; 3013 VerifyOption _vo; 3014 public: 3015 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3016 _g1h(g1h), _vo(vo) 3017 { } 3018 void do_oop(narrowOop *p) { do_oop_work(p); } 3019 void do_oop( oop *p) { do_oop_work(p); } 3020 3021 template <class T> void do_oop_work(T *p) { 3022 oop obj = oopDesc::load_decode_heap_oop(p); 3023 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3024 "Dead object referenced by a not dead object"); 3025 } 3026 }; 3027 3028 class VerifyObjsInRegionClosure: public ObjectClosure { 3029 private: 3030 G1CollectedHeap* _g1h; 3031 size_t _live_bytes; 3032 HeapRegion *_hr; 3033 VerifyOption _vo; 3034 public: 3035 // _vo == UsePrevMarking -> use "prev" marking information, 3036 // _vo == UseNextMarking -> use "next" marking information, 3037 // _vo == UseMarkWord -> use mark word from object header. 3038 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3039 : _live_bytes(0), _hr(hr), _vo(vo) { 3040 _g1h = G1CollectedHeap::heap(); 3041 } 3042 void do_object(oop o) { 3043 VerifyLivenessOopClosure isLive(_g1h, _vo); 3044 assert(o != NULL, "Huh?"); 3045 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3046 // If the object is alive according to the mark word, 3047 // then verify that the marking information agrees. 3048 // Note we can't verify the contra-positive of the 3049 // above: if the object is dead (according to the mark 3050 // word), it may not be marked, or may have been marked 3051 // but has since became dead, or may have been allocated 3052 // since the last marking. 3053 if (_vo == VerifyOption_G1UseMarkWord) { 3054 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3055 } 3056 3057 o->oop_iterate_no_header(&isLive); 3058 if (!_hr->obj_allocated_since_prev_marking(o)) { 3059 size_t obj_size = o->size(); // Make sure we don't overflow 3060 _live_bytes += (obj_size * HeapWordSize); 3061 } 3062 } 3063 } 3064 size_t live_bytes() { return _live_bytes; } 3065 }; 3066 3067 class PrintObjsInRegionClosure : public ObjectClosure { 3068 HeapRegion *_hr; 3069 G1CollectedHeap *_g1; 3070 public: 3071 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3072 _g1 = G1CollectedHeap::heap(); 3073 }; 3074 3075 void do_object(oop o) { 3076 if (o != NULL) { 3077 HeapWord *start = (HeapWord *) o; 3078 size_t word_sz = o->size(); 3079 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3080 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3081 (void*) o, word_sz, 3082 _g1->isMarkedPrev(o), 3083 _g1->isMarkedNext(o), 3084 _hr->obj_allocated_since_prev_marking(o)); 3085 HeapWord *end = start + word_sz; 3086 HeapWord *cur; 3087 int *val; 3088 for (cur = start; cur < end; cur++) { 3089 val = (int *) cur; 3090 gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val); 3091 } 3092 } 3093 } 3094 }; 3095 3096 class VerifyRegionClosure: public HeapRegionClosure { 3097 private: 3098 bool _par; 3099 VerifyOption _vo; 3100 bool _failures; 3101 public: 3102 // _vo == UsePrevMarking -> use "prev" marking information, 3103 // _vo == UseNextMarking -> use "next" marking information, 3104 // _vo == UseMarkWord -> use mark word from object header. 3105 VerifyRegionClosure(bool par, VerifyOption vo) 3106 : _par(par), 3107 _vo(vo), 3108 _failures(false) {} 3109 3110 bool failures() { 3111 return _failures; 3112 } 3113 3114 bool doHeapRegion(HeapRegion* r) { 3115 if (!r->is_continues_humongous()) { 3116 bool failures = false; 3117 r->verify(_vo, &failures); 3118 if (failures) { 3119 _failures = true; 3120 } else { 3121 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3122 r->object_iterate(¬_dead_yet_cl); 3123 if (_vo != VerifyOption_G1UseNextMarking) { 3124 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3125 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3126 "max_live_bytes "SIZE_FORMAT" " 3127 "< calculated "SIZE_FORMAT, 3128 r->bottom(), r->end(), 3129 r->max_live_bytes(), 3130 not_dead_yet_cl.live_bytes()); 3131 _failures = true; 3132 } 3133 } else { 3134 // When vo == UseNextMarking we cannot currently do a sanity 3135 // check on the live bytes as the calculation has not been 3136 // finalized yet. 3137 } 3138 } 3139 } 3140 return false; // stop the region iteration if we hit a failure 3141 } 3142 }; 3143 3144 // This is the task used for parallel verification of the heap regions 3145 3146 class G1ParVerifyTask: public AbstractGangTask { 3147 private: 3148 G1CollectedHeap* _g1h; 3149 VerifyOption _vo; 3150 bool _failures; 3151 HeapRegionClaimer _hrclaimer; 3152 3153 public: 3154 // _vo == UsePrevMarking -> use "prev" marking information, 3155 // _vo == UseNextMarking -> use "next" marking information, 3156 // _vo == UseMarkWord -> use mark word from object header. 3157 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3158 AbstractGangTask("Parallel verify task"), 3159 _g1h(g1h), 3160 _vo(vo), 3161 _failures(false), 3162 _hrclaimer(g1h->workers()->active_workers()) {} 3163 3164 bool failures() { 3165 return _failures; 3166 } 3167 3168 void work(uint worker_id) { 3169 HandleMark hm; 3170 VerifyRegionClosure blk(true, _vo); 3171 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3172 if (blk.failures()) { 3173 _failures = true; 3174 } 3175 } 3176 }; 3177 3178 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3179 if (SafepointSynchronize::is_at_safepoint()) { 3180 assert(Thread::current()->is_VM_thread(), 3181 "Expected to be executed serially by the VM thread at this point"); 3182 3183 if (!silent) { gclog_or_tty->print("Roots "); } 3184 VerifyRootsClosure rootsCl(vo); 3185 VerifyKlassClosure klassCl(this, &rootsCl); 3186 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3187 3188 // We apply the relevant closures to all the oops in the 3189 // system dictionary, class loader data graph, the string table 3190 // and the nmethods in the code cache. 3191 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3192 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3193 3194 process_all_roots(true, // activate StrongRootsScope 3195 SO_AllCodeCache, // roots scanning options 3196 &rootsCl, 3197 &cldCl, 3198 &blobsCl); 3199 3200 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3201 3202 if (vo != VerifyOption_G1UseMarkWord) { 3203 // If we're verifying during a full GC then the region sets 3204 // will have been torn down at the start of the GC. Therefore 3205 // verifying the region sets will fail. So we only verify 3206 // the region sets when not in a full GC. 3207 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3208 verify_region_sets(); 3209 } 3210 3211 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3212 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3213 3214 G1ParVerifyTask task(this, vo); 3215 assert(UseDynamicNumberOfGCThreads || 3216 workers()->active_workers() == workers()->total_workers(), 3217 "If not dynamic should be using all the workers"); 3218 int n_workers = workers()->active_workers(); 3219 set_par_threads(n_workers); 3220 workers()->run_task(&task); 3221 set_par_threads(0); 3222 if (task.failures()) { 3223 failures = true; 3224 } 3225 3226 } else { 3227 VerifyRegionClosure blk(false, vo); 3228 heap_region_iterate(&blk); 3229 if (blk.failures()) { 3230 failures = true; 3231 } 3232 } 3233 if (!silent) gclog_or_tty->print("RemSet "); 3234 rem_set()->verify(); 3235 3236 if (G1StringDedup::is_enabled()) { 3237 if (!silent) gclog_or_tty->print("StrDedup "); 3238 G1StringDedup::verify(); 3239 } 3240 3241 if (failures) { 3242 gclog_or_tty->print_cr("Heap:"); 3243 // It helps to have the per-region information in the output to 3244 // help us track down what went wrong. This is why we call 3245 // print_extended_on() instead of print_on(). 3246 print_extended_on(gclog_or_tty); 3247 gclog_or_tty->cr(); 3248 #ifndef PRODUCT 3249 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3250 concurrent_mark()->print_reachable("at-verification-failure", 3251 vo, false /* all */); 3252 } 3253 #endif 3254 gclog_or_tty->flush(); 3255 } 3256 guarantee(!failures, "there should not have been any failures"); 3257 } else { 3258 if (!silent) { 3259 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3260 if (G1StringDedup::is_enabled()) { 3261 gclog_or_tty->print(", StrDedup"); 3262 } 3263 gclog_or_tty->print(") "); 3264 } 3265 } 3266 } 3267 3268 void G1CollectedHeap::verify(bool silent) { 3269 verify(silent, VerifyOption_G1UsePrevMarking); 3270 } 3271 3272 double G1CollectedHeap::verify(bool guard, const char* msg) { 3273 double verify_time_ms = 0.0; 3274 3275 if (guard && total_collections() >= VerifyGCStartAt) { 3276 double verify_start = os::elapsedTime(); 3277 HandleMark hm; // Discard invalid handles created during verification 3278 prepare_for_verify(); 3279 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3280 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3281 } 3282 3283 return verify_time_ms; 3284 } 3285 3286 void G1CollectedHeap::verify_before_gc() { 3287 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3288 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3289 } 3290 3291 void G1CollectedHeap::verify_after_gc() { 3292 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3293 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3294 } 3295 3296 class PrintRegionClosure: public HeapRegionClosure { 3297 outputStream* _st; 3298 public: 3299 PrintRegionClosure(outputStream* st) : _st(st) {} 3300 bool doHeapRegion(HeapRegion* r) { 3301 r->print_on(_st); 3302 return false; 3303 } 3304 }; 3305 3306 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3307 const HeapRegion* hr, 3308 const VerifyOption vo) const { 3309 switch (vo) { 3310 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3311 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3312 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3313 default: ShouldNotReachHere(); 3314 } 3315 return false; // keep some compilers happy 3316 } 3317 3318 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3319 const VerifyOption vo) const { 3320 switch (vo) { 3321 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3322 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3323 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3324 default: ShouldNotReachHere(); 3325 } 3326 return false; // keep some compilers happy 3327 } 3328 3329 void G1CollectedHeap::print_on(outputStream* st) const { 3330 st->print(" %-20s", "garbage-first heap"); 3331 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3332 capacity()/K, used_unlocked()/K); 3333 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3334 _hrm.reserved().start(), 3335 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords, 3336 _hrm.reserved().end()); 3337 st->cr(); 3338 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3339 uint young_regions = _young_list->length(); 3340 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3341 (size_t) young_regions * HeapRegion::GrainBytes / K); 3342 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3343 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3344 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3345 st->cr(); 3346 MetaspaceAux::print_on(st); 3347 } 3348 3349 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3350 print_on(st); 3351 3352 // Print the per-region information. 3353 st->cr(); 3354 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3355 "HS=humongous(starts), HC=humongous(continues), " 3356 "CS=collection set, F=free, TS=gc time stamp, " 3357 "PTAMS=previous top-at-mark-start, " 3358 "NTAMS=next top-at-mark-start)"); 3359 PrintRegionClosure blk(st); 3360 heap_region_iterate(&blk); 3361 } 3362 3363 void G1CollectedHeap::print_on_error(outputStream* st) const { 3364 this->CollectedHeap::print_on_error(st); 3365 3366 if (_cm != NULL) { 3367 st->cr(); 3368 _cm->print_on_error(st); 3369 } 3370 } 3371 3372 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3373 if (G1CollectedHeap::use_parallel_gc_threads()) { 3374 workers()->print_worker_threads_on(st); 3375 } 3376 _cmThread->print_on(st); 3377 st->cr(); 3378 _cm->print_worker_threads_on(st); 3379 _cg1r->print_worker_threads_on(st); 3380 if (G1StringDedup::is_enabled()) { 3381 G1StringDedup::print_worker_threads_on(st); 3382 } 3383 } 3384 3385 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3386 if (G1CollectedHeap::use_parallel_gc_threads()) { 3387 workers()->threads_do(tc); 3388 } 3389 tc->do_thread(_cmThread); 3390 _cg1r->threads_do(tc); 3391 if (G1StringDedup::is_enabled()) { 3392 G1StringDedup::threads_do(tc); 3393 } 3394 } 3395 3396 void G1CollectedHeap::print_tracing_info() const { 3397 // We'll overload this to mean "trace GC pause statistics." 3398 if (TraceYoungGenTime || TraceOldGenTime) { 3399 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3400 // to that. 3401 g1_policy()->print_tracing_info(); 3402 } 3403 if (G1SummarizeRSetStats) { 3404 g1_rem_set()->print_summary_info(); 3405 } 3406 if (G1SummarizeConcMark) { 3407 concurrent_mark()->print_summary_info(); 3408 } 3409 g1_policy()->print_yg_surv_rate_info(); 3410 SpecializationStats::print(); 3411 } 3412 3413 #ifndef PRODUCT 3414 // Helpful for debugging RSet issues. 3415 3416 class PrintRSetsClosure : public HeapRegionClosure { 3417 private: 3418 const char* _msg; 3419 size_t _occupied_sum; 3420 3421 public: 3422 bool doHeapRegion(HeapRegion* r) { 3423 HeapRegionRemSet* hrrs = r->rem_set(); 3424 size_t occupied = hrrs->occupied(); 3425 _occupied_sum += occupied; 3426 3427 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3428 HR_FORMAT_PARAMS(r)); 3429 if (occupied == 0) { 3430 gclog_or_tty->print_cr(" RSet is empty"); 3431 } else { 3432 hrrs->print(); 3433 } 3434 gclog_or_tty->print_cr("----------"); 3435 return false; 3436 } 3437 3438 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3439 gclog_or_tty->cr(); 3440 gclog_or_tty->print_cr("========================================"); 3441 gclog_or_tty->print_cr("%s", msg); 3442 gclog_or_tty->cr(); 3443 } 3444 3445 ~PrintRSetsClosure() { 3446 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3447 gclog_or_tty->print_cr("========================================"); 3448 gclog_or_tty->cr(); 3449 } 3450 }; 3451 3452 void G1CollectedHeap::print_cset_rsets() { 3453 PrintRSetsClosure cl("Printing CSet RSets"); 3454 collection_set_iterate(&cl); 3455 } 3456 3457 void G1CollectedHeap::print_all_rsets() { 3458 PrintRSetsClosure cl("Printing All RSets");; 3459 heap_region_iterate(&cl); 3460 } 3461 #endif // PRODUCT 3462 3463 G1CollectedHeap* G1CollectedHeap::heap() { 3464 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3465 "not a garbage-first heap"); 3466 return _g1h; 3467 } 3468 3469 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3470 // always_do_update_barrier = false; 3471 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3472 // Fill TLAB's and such 3473 accumulate_statistics_all_tlabs(); 3474 ensure_parsability(true); 3475 3476 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3477 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3478 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3479 } 3480 } 3481 3482 void G1CollectedHeap::gc_epilogue(bool full) { 3483 3484 if (G1SummarizeRSetStats && 3485 (G1SummarizeRSetStatsPeriod > 0) && 3486 // we are at the end of the GC. Total collections has already been increased. 3487 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3488 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3489 } 3490 3491 // FIXME: what is this about? 3492 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3493 // is set. 3494 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3495 "derived pointer present")); 3496 // always_do_update_barrier = true; 3497 3498 resize_all_tlabs(); 3499 allocation_context_stats().update(full); 3500 3501 // We have just completed a GC. Update the soft reference 3502 // policy with the new heap occupancy 3503 Universe::update_heap_info_at_gc(); 3504 } 3505 3506 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3507 unsigned int gc_count_before, 3508 bool* succeeded, 3509 GCCause::Cause gc_cause) { 3510 assert_heap_not_locked_and_not_at_safepoint(); 3511 g1_policy()->record_stop_world_start(); 3512 VM_G1IncCollectionPause op(gc_count_before, 3513 word_size, 3514 false, /* should_initiate_conc_mark */ 3515 g1_policy()->max_pause_time_ms(), 3516 gc_cause); 3517 3518 op.set_allocation_context(AllocationContext::current()); 3519 VMThread::execute(&op); 3520 3521 HeapWord* result = op.result(); 3522 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3523 assert(result == NULL || ret_succeeded, 3524 "the result should be NULL if the VM did not succeed"); 3525 *succeeded = ret_succeeded; 3526 3527 assert_heap_not_locked(); 3528 return result; 3529 } 3530 3531 void 3532 G1CollectedHeap::doConcurrentMark() { 3533 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3534 if (!_cmThread->in_progress()) { 3535 _cmThread->set_started(); 3536 CGC_lock->notify(); 3537 } 3538 } 3539 3540 size_t G1CollectedHeap::pending_card_num() { 3541 size_t extra_cards = 0; 3542 JavaThread *curr = Threads::first(); 3543 while (curr != NULL) { 3544 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3545 extra_cards += dcq.size(); 3546 curr = curr->next(); 3547 } 3548 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3549 size_t buffer_size = dcqs.buffer_size(); 3550 size_t buffer_num = dcqs.completed_buffers_num(); 3551 3552 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3553 // in bytes - not the number of 'entries'. We need to convert 3554 // into a number of cards. 3555 return (buffer_size * buffer_num + extra_cards) / oopSize; 3556 } 3557 3558 size_t G1CollectedHeap::cards_scanned() { 3559 return g1_rem_set()->cardsScanned(); 3560 } 3561 3562 bool G1CollectedHeap::humongous_region_is_always_live(uint index) { 3563 HeapRegion* region = region_at(index); 3564 assert(region->is_starts_humongous(), "Must start a humongous object"); 3565 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty(); 3566 } 3567 3568 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3569 private: 3570 size_t _total_humongous; 3571 size_t _candidate_humongous; 3572 public: 3573 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) { 3574 } 3575 3576 virtual bool doHeapRegion(HeapRegion* r) { 3577 if (!r->is_starts_humongous()) { 3578 return false; 3579 } 3580 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3581 3582 uint region_idx = r->hrm_index(); 3583 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx); 3584 // Is_candidate already filters out humongous regions with some remembered set. 3585 // This will not lead to humongous object that we mistakenly keep alive because 3586 // during young collection the remembered sets will only be added to. 3587 if (is_candidate) { 3588 g1h->register_humongous_region_with_in_cset_fast_test(region_idx); 3589 _candidate_humongous++; 3590 } 3591 _total_humongous++; 3592 3593 return false; 3594 } 3595 3596 size_t total_humongous() const { return _total_humongous; } 3597 size_t candidate_humongous() const { return _candidate_humongous; } 3598 }; 3599 3600 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() { 3601 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) { 3602 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0); 3603 return; 3604 } 3605 3606 RegisterHumongousWithInCSetFastTestClosure cl; 3607 heap_region_iterate(&cl); 3608 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(), 3609 cl.candidate_humongous()); 3610 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3611 3612 if (_has_humongous_reclaim_candidates) { 3613 clear_humongous_is_live_table(); 3614 } 3615 } 3616 3617 void 3618 G1CollectedHeap::setup_surviving_young_words() { 3619 assert(_surviving_young_words == NULL, "pre-condition"); 3620 uint array_length = g1_policy()->young_cset_region_length(); 3621 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3622 if (_surviving_young_words == NULL) { 3623 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3624 "Not enough space for young surv words summary."); 3625 } 3626 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3627 #ifdef ASSERT 3628 for (uint i = 0; i < array_length; ++i) { 3629 assert( _surviving_young_words[i] == 0, "memset above" ); 3630 } 3631 #endif // !ASSERT 3632 } 3633 3634 void 3635 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3636 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3637 uint array_length = g1_policy()->young_cset_region_length(); 3638 for (uint i = 0; i < array_length; ++i) { 3639 _surviving_young_words[i] += surv_young_words[i]; 3640 } 3641 } 3642 3643 void 3644 G1CollectedHeap::cleanup_surviving_young_words() { 3645 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3646 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3647 _surviving_young_words = NULL; 3648 } 3649 3650 #ifdef ASSERT 3651 class VerifyCSetClosure: public HeapRegionClosure { 3652 public: 3653 bool doHeapRegion(HeapRegion* hr) { 3654 // Here we check that the CSet region's RSet is ready for parallel 3655 // iteration. The fields that we'll verify are only manipulated 3656 // when the region is part of a CSet and is collected. Afterwards, 3657 // we reset these fields when we clear the region's RSet (when the 3658 // region is freed) so they are ready when the region is 3659 // re-allocated. The only exception to this is if there's an 3660 // evacuation failure and instead of freeing the region we leave 3661 // it in the heap. In that case, we reset these fields during 3662 // evacuation failure handling. 3663 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3664 3665 // Here's a good place to add any other checks we'd like to 3666 // perform on CSet regions. 3667 return false; 3668 } 3669 }; 3670 #endif // ASSERT 3671 3672 #if TASKQUEUE_STATS 3673 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3674 st->print_raw_cr("GC Task Stats"); 3675 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3676 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3677 } 3678 3679 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3680 print_taskqueue_stats_hdr(st); 3681 3682 TaskQueueStats totals; 3683 const int n = workers() != NULL ? workers()->total_workers() : 1; 3684 for (int i = 0; i < n; ++i) { 3685 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3686 totals += task_queue(i)->stats; 3687 } 3688 st->print_raw("tot "); totals.print(st); st->cr(); 3689 3690 DEBUG_ONLY(totals.verify()); 3691 } 3692 3693 void G1CollectedHeap::reset_taskqueue_stats() { 3694 const int n = workers() != NULL ? workers()->total_workers() : 1; 3695 for (int i = 0; i < n; ++i) { 3696 task_queue(i)->stats.reset(); 3697 } 3698 } 3699 #endif // TASKQUEUE_STATS 3700 3701 void G1CollectedHeap::log_gc_header() { 3702 if (!G1Log::fine()) { 3703 return; 3704 } 3705 3706 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id()); 3707 3708 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3709 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3710 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3711 3712 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3713 } 3714 3715 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3716 if (!G1Log::fine()) { 3717 return; 3718 } 3719 3720 if (G1Log::finer()) { 3721 if (evacuation_failed()) { 3722 gclog_or_tty->print(" (to-space exhausted)"); 3723 } 3724 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3725 g1_policy()->phase_times()->note_gc_end(); 3726 g1_policy()->phase_times()->print(pause_time_sec); 3727 g1_policy()->print_detailed_heap_transition(); 3728 } else { 3729 if (evacuation_failed()) { 3730 gclog_or_tty->print("--"); 3731 } 3732 g1_policy()->print_heap_transition(); 3733 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3734 } 3735 gclog_or_tty->flush(); 3736 } 3737 3738 bool 3739 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3740 assert_at_safepoint(true /* should_be_vm_thread */); 3741 guarantee(!is_gc_active(), "collection is not reentrant"); 3742 3743 if (GC_locker::check_active_before_gc()) { 3744 return false; 3745 } 3746 3747 _gc_timer_stw->register_gc_start(); 3748 3749 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3750 3751 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3752 ResourceMark rm; 3753 3754 print_heap_before_gc(); 3755 trace_heap_before_gc(_gc_tracer_stw); 3756 3757 verify_region_sets_optional(); 3758 verify_dirty_young_regions(); 3759 3760 // This call will decide whether this pause is an initial-mark 3761 // pause. If it is, during_initial_mark_pause() will return true 3762 // for the duration of this pause. 3763 g1_policy()->decide_on_conc_mark_initiation(); 3764 3765 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3766 assert(!g1_policy()->during_initial_mark_pause() || 3767 g1_policy()->gcs_are_young(), "sanity"); 3768 3769 // We also do not allow mixed GCs during marking. 3770 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3771 3772 // Record whether this pause is an initial mark. When the current 3773 // thread has completed its logging output and it's safe to signal 3774 // the CM thread, the flag's value in the policy has been reset. 3775 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3776 3777 // Inner scope for scope based logging, timers, and stats collection 3778 { 3779 EvacuationInfo evacuation_info; 3780 3781 if (g1_policy()->during_initial_mark_pause()) { 3782 // We are about to start a marking cycle, so we increment the 3783 // full collection counter. 3784 increment_old_marking_cycles_started(); 3785 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3786 } 3787 3788 _gc_tracer_stw->report_yc_type(yc_type()); 3789 3790 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3791 3792 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3793 workers()->active_workers() : 1); 3794 double pause_start_sec = os::elapsedTime(); 3795 g1_policy()->phase_times()->note_gc_start(active_workers); 3796 log_gc_header(); 3797 3798 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3799 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3800 3801 // If the secondary_free_list is not empty, append it to the 3802 // free_list. No need to wait for the cleanup operation to finish; 3803 // the region allocation code will check the secondary_free_list 3804 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3805 // set, skip this step so that the region allocation code has to 3806 // get entries from the secondary_free_list. 3807 if (!G1StressConcRegionFreeing) { 3808 append_secondary_free_list_if_not_empty_with_lock(); 3809 } 3810 3811 assert(check_young_list_well_formed(), "young list should be well formed"); 3812 3813 // Don't dynamically change the number of GC threads this early. A value of 3814 // 0 is used to indicate serial work. When parallel work is done, 3815 // it will be set. 3816 3817 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3818 IsGCActiveMark x; 3819 3820 gc_prologue(false); 3821 increment_total_collections(false /* full gc */); 3822 increment_gc_time_stamp(); 3823 3824 verify_before_gc(); 3825 3826 check_bitmaps("GC Start"); 3827 3828 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3829 3830 // Please see comment in g1CollectedHeap.hpp and 3831 // G1CollectedHeap::ref_processing_init() to see how 3832 // reference processing currently works in G1. 3833 3834 // Enable discovery in the STW reference processor 3835 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 3836 true /*verify_no_refs*/); 3837 3838 { 3839 // We want to temporarily turn off discovery by the 3840 // CM ref processor, if necessary, and turn it back on 3841 // on again later if we do. Using a scoped 3842 // NoRefDiscovery object will do this. 3843 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3844 3845 // Forget the current alloc region (we might even choose it to be part 3846 // of the collection set!). 3847 _allocator->release_mutator_alloc_region(); 3848 3849 // We should call this after we retire the mutator alloc 3850 // region(s) so that all the ALLOC / RETIRE events are generated 3851 // before the start GC event. 3852 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3853 3854 // This timing is only used by the ergonomics to handle our pause target. 3855 // It is unclear why this should not include the full pause. We will 3856 // investigate this in CR 7178365. 3857 // 3858 // Preserving the old comment here if that helps the investigation: 3859 // 3860 // The elapsed time induced by the start time below deliberately elides 3861 // the possible verification above. 3862 double sample_start_time_sec = os::elapsedTime(); 3863 3864 #if YOUNG_LIST_VERBOSE 3865 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3866 _young_list->print(); 3867 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3868 #endif // YOUNG_LIST_VERBOSE 3869 3870 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3871 3872 double scan_wait_start = os::elapsedTime(); 3873 // We have to wait until the CM threads finish scanning the 3874 // root regions as it's the only way to ensure that all the 3875 // objects on them have been correctly scanned before we start 3876 // moving them during the GC. 3877 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3878 double wait_time_ms = 0.0; 3879 if (waited) { 3880 double scan_wait_end = os::elapsedTime(); 3881 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3882 } 3883 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3884 3885 #if YOUNG_LIST_VERBOSE 3886 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3887 _young_list->print(); 3888 #endif // YOUNG_LIST_VERBOSE 3889 3890 if (g1_policy()->during_initial_mark_pause()) { 3891 concurrent_mark()->checkpointRootsInitialPre(); 3892 } 3893 3894 #if YOUNG_LIST_VERBOSE 3895 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3896 _young_list->print(); 3897 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3898 #endif // YOUNG_LIST_VERBOSE 3899 3900 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info); 3901 3902 register_humongous_regions_with_in_cset_fast_test(); 3903 3904 _cm->note_start_of_gc(); 3905 // We should not verify the per-thread SATB buffers given that 3906 // we have not filtered them yet (we'll do so during the 3907 // GC). We also call this after finalize_cset() to 3908 // ensure that the CSet has been finalized. 3909 _cm->verify_no_cset_oops(true /* verify_stacks */, 3910 true /* verify_enqueued_buffers */, 3911 false /* verify_thread_buffers */, 3912 true /* verify_fingers */); 3913 3914 if (_hr_printer.is_active()) { 3915 HeapRegion* hr = g1_policy()->collection_set(); 3916 while (hr != NULL) { 3917 _hr_printer.cset(hr); 3918 hr = hr->next_in_collection_set(); 3919 } 3920 } 3921 3922 #ifdef ASSERT 3923 VerifyCSetClosure cl; 3924 collection_set_iterate(&cl); 3925 #endif // ASSERT 3926 3927 setup_surviving_young_words(); 3928 3929 // Initialize the GC alloc regions. 3930 _allocator->init_gc_alloc_regions(evacuation_info); 3931 3932 // Actually do the work... 3933 evacuate_collection_set(evacuation_info); 3934 3935 // We do this to mainly verify the per-thread SATB buffers 3936 // (which have been filtered by now) since we didn't verify 3937 // them earlier. No point in re-checking the stacks / enqueued 3938 // buffers given that the CSet has not changed since last time 3939 // we checked. 3940 _cm->verify_no_cset_oops(false /* verify_stacks */, 3941 false /* verify_enqueued_buffers */, 3942 true /* verify_thread_buffers */, 3943 true /* verify_fingers */); 3944 3945 free_collection_set(g1_policy()->collection_set(), evacuation_info); 3946 3947 eagerly_reclaim_humongous_regions(); 3948 3949 g1_policy()->clear_collection_set(); 3950 3951 cleanup_surviving_young_words(); 3952 3953 // Start a new incremental collection set for the next pause. 3954 g1_policy()->start_incremental_cset_building(); 3955 3956 clear_cset_fast_test(); 3957 3958 _young_list->reset_sampled_info(); 3959 3960 // Don't check the whole heap at this point as the 3961 // GC alloc regions from this pause have been tagged 3962 // as survivors and moved on to the survivor list. 3963 // Survivor regions will fail the !is_young() check. 3964 assert(check_young_list_empty(false /* check_heap */), 3965 "young list should be empty"); 3966 3967 #if YOUNG_LIST_VERBOSE 3968 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3969 _young_list->print(); 3970 #endif // YOUNG_LIST_VERBOSE 3971 3972 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3973 _young_list->first_survivor_region(), 3974 _young_list->last_survivor_region()); 3975 3976 _young_list->reset_auxilary_lists(); 3977 3978 if (evacuation_failed()) { 3979 _allocator->set_used(recalculate_used()); 3980 uint n_queues = MAX2((int)ParallelGCThreads, 1); 3981 for (uint i = 0; i < n_queues; i++) { 3982 if (_evacuation_failed_info_array[i].has_failed()) { 3983 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3984 } 3985 } 3986 } else { 3987 // The "used" of the the collection set have already been subtracted 3988 // when they were freed. Add in the bytes evacuated. 3989 _allocator->increase_used(g1_policy()->bytes_copied_during_gc()); 3990 } 3991 3992 if (g1_policy()->during_initial_mark_pause()) { 3993 // We have to do this before we notify the CM threads that 3994 // they can start working to make sure that all the 3995 // appropriate initialization is done on the CM object. 3996 concurrent_mark()->checkpointRootsInitialPost(); 3997 set_marking_started(); 3998 // Note that we don't actually trigger the CM thread at 3999 // this point. We do that later when we're sure that 4000 // the current thread has completed its logging output. 4001 } 4002 4003 allocate_dummy_regions(); 4004 4005 #if YOUNG_LIST_VERBOSE 4006 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 4007 _young_list->print(); 4008 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4009 #endif // YOUNG_LIST_VERBOSE 4010 4011 _allocator->init_mutator_alloc_region(); 4012 4013 { 4014 size_t expand_bytes = g1_policy()->expansion_amount(); 4015 if (expand_bytes > 0) { 4016 size_t bytes_before = capacity(); 4017 // No need for an ergo verbose message here, 4018 // expansion_amount() does this when it returns a value > 0. 4019 if (!expand(expand_bytes)) { 4020 // We failed to expand the heap. Cannot do anything about it. 4021 } 4022 } 4023 } 4024 4025 // We redo the verification but now wrt to the new CSet which 4026 // has just got initialized after the previous CSet was freed. 4027 _cm->verify_no_cset_oops(true /* verify_stacks */, 4028 true /* verify_enqueued_buffers */, 4029 true /* verify_thread_buffers */, 4030 true /* verify_fingers */); 4031 _cm->note_end_of_gc(); 4032 4033 // This timing is only used by the ergonomics to handle our pause target. 4034 // It is unclear why this should not include the full pause. We will 4035 // investigate this in CR 7178365. 4036 double sample_end_time_sec = os::elapsedTime(); 4037 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 4038 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info); 4039 4040 MemoryService::track_memory_usage(); 4041 4042 // In prepare_for_verify() below we'll need to scan the deferred 4043 // update buffers to bring the RSets up-to-date if 4044 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 4045 // the update buffers we'll probably need to scan cards on the 4046 // regions we just allocated to (i.e., the GC alloc 4047 // regions). However, during the last GC we called 4048 // set_saved_mark() on all the GC alloc regions, so card 4049 // scanning might skip the [saved_mark_word()...top()] area of 4050 // those regions (i.e., the area we allocated objects into 4051 // during the last GC). But it shouldn't. Given that 4052 // saved_mark_word() is conditional on whether the GC time stamp 4053 // on the region is current or not, by incrementing the GC time 4054 // stamp here we invalidate all the GC time stamps on all the 4055 // regions and saved_mark_word() will simply return top() for 4056 // all the regions. This is a nicer way of ensuring this rather 4057 // than iterating over the regions and fixing them. In fact, the 4058 // GC time stamp increment here also ensures that 4059 // saved_mark_word() will return top() between pauses, i.e., 4060 // during concurrent refinement. So we don't need the 4061 // is_gc_active() check to decided which top to use when 4062 // scanning cards (see CR 7039627). 4063 increment_gc_time_stamp(); 4064 4065 verify_after_gc(); 4066 check_bitmaps("GC End"); 4067 4068 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4069 ref_processor_stw()->verify_no_references_recorded(); 4070 4071 // CM reference discovery will be re-enabled if necessary. 4072 } 4073 4074 // We should do this after we potentially expand the heap so 4075 // that all the COMMIT events are generated before the end GC 4076 // event, and after we retire the GC alloc regions so that all 4077 // RETIRE events are generated before the end GC event. 4078 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4079 4080 #ifdef TRACESPINNING 4081 ParallelTaskTerminator::print_termination_counts(); 4082 #endif 4083 4084 gc_epilogue(false); 4085 } 4086 4087 // Print the remainder of the GC log output. 4088 log_gc_footer(os::elapsedTime() - pause_start_sec); 4089 4090 // It is not yet to safe to tell the concurrent mark to 4091 // start as we have some optional output below. We don't want the 4092 // output from the concurrent mark thread interfering with this 4093 // logging output either. 4094 4095 _hrm.verify_optional(); 4096 verify_region_sets_optional(); 4097 4098 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4099 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4100 4101 print_heap_after_gc(); 4102 trace_heap_after_gc(_gc_tracer_stw); 4103 4104 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4105 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4106 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4107 // before any GC notifications are raised. 4108 g1mm()->update_sizes(); 4109 4110 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4111 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4112 _gc_timer_stw->register_gc_end(); 4113 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4114 } 4115 // It should now be safe to tell the concurrent mark thread to start 4116 // without its logging output interfering with the logging output 4117 // that came from the pause. 4118 4119 if (should_start_conc_mark) { 4120 // CAUTION: after the doConcurrentMark() call below, 4121 // the concurrent marking thread(s) could be running 4122 // concurrently with us. Make sure that anything after 4123 // this point does not assume that we are the only GC thread 4124 // running. Note: of course, the actual marking work will 4125 // not start until the safepoint itself is released in 4126 // SuspendibleThreadSet::desynchronize(). 4127 doConcurrentMark(); 4128 } 4129 4130 return true; 4131 } 4132 4133 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4134 { 4135 size_t gclab_word_size; 4136 switch (purpose) { 4137 case GCAllocForSurvived: 4138 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4139 break; 4140 case GCAllocForTenured: 4141 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4142 break; 4143 default: 4144 assert(false, "unknown GCAllocPurpose"); 4145 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4146 break; 4147 } 4148 4149 // Prevent humongous PLAB sizes for two reasons: 4150 // * PLABs are allocated using a similar paths as oops, but should 4151 // never be in a humongous region 4152 // * Allowing humongous PLABs needlessly churns the region free lists 4153 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4154 } 4155 4156 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4157 _drain_in_progress = false; 4158 set_evac_failure_closure(cl); 4159 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4160 } 4161 4162 void G1CollectedHeap::finalize_for_evac_failure() { 4163 assert(_evac_failure_scan_stack != NULL && 4164 _evac_failure_scan_stack->length() == 0, 4165 "Postcondition"); 4166 assert(!_drain_in_progress, "Postcondition"); 4167 delete _evac_failure_scan_stack; 4168 _evac_failure_scan_stack = NULL; 4169 } 4170 4171 void G1CollectedHeap::remove_self_forwarding_pointers() { 4172 double remove_self_forwards_start = os::elapsedTime(); 4173 4174 if (G1CollectedHeap::use_parallel_gc_threads()) { 4175 set_par_threads(); 4176 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4177 workers()->run_task(&rsfp_task); 4178 set_par_threads(0); 4179 } else { 4180 RemoveSelfForwardPtrHRClosure rsfp(this); 4181 _g1h->collection_set_iterate(&rsfp); 4182 } 4183 4184 // Now restore saved marks, if any. 4185 assert(_objs_with_preserved_marks.size() == 4186 _preserved_marks_of_objs.size(), "Both or none."); 4187 while (!_objs_with_preserved_marks.is_empty()) { 4188 oop obj = _objs_with_preserved_marks.pop(); 4189 markOop m = _preserved_marks_of_objs.pop(); 4190 obj->set_mark(m); 4191 } 4192 _objs_with_preserved_marks.clear(true); 4193 _preserved_marks_of_objs.clear(true); 4194 4195 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4196 } 4197 4198 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4199 _evac_failure_scan_stack->push(obj); 4200 } 4201 4202 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4203 assert(_evac_failure_scan_stack != NULL, "precondition"); 4204 4205 while (_evac_failure_scan_stack->length() > 0) { 4206 oop obj = _evac_failure_scan_stack->pop(); 4207 _evac_failure_closure->set_region(heap_region_containing(obj)); 4208 obj->oop_iterate_backwards(_evac_failure_closure); 4209 } 4210 } 4211 4212 oop 4213 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, 4214 oop old) { 4215 assert(obj_in_cs(old), 4216 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4217 (HeapWord*) old)); 4218 markOop m = old->mark(); 4219 oop forward_ptr = old->forward_to_atomic(old); 4220 if (forward_ptr == NULL) { 4221 // Forward-to-self succeeded. 4222 assert(_par_scan_state != NULL, "par scan state"); 4223 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4224 uint queue_num = _par_scan_state->queue_num(); 4225 4226 _evacuation_failed = true; 4227 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size()); 4228 if (_evac_failure_closure != cl) { 4229 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4230 assert(!_drain_in_progress, 4231 "Should only be true while someone holds the lock."); 4232 // Set the global evac-failure closure to the current thread's. 4233 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4234 set_evac_failure_closure(cl); 4235 // Now do the common part. 4236 handle_evacuation_failure_common(old, m); 4237 // Reset to NULL. 4238 set_evac_failure_closure(NULL); 4239 } else { 4240 // The lock is already held, and this is recursive. 4241 assert(_drain_in_progress, "This should only be the recursive case."); 4242 handle_evacuation_failure_common(old, m); 4243 } 4244 return old; 4245 } else { 4246 // Forward-to-self failed. Either someone else managed to allocate 4247 // space for this object (old != forward_ptr) or they beat us in 4248 // self-forwarding it (old == forward_ptr). 4249 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4250 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4251 "should not be in the CSet", 4252 (HeapWord*) old, (HeapWord*) forward_ptr)); 4253 return forward_ptr; 4254 } 4255 } 4256 4257 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4258 preserve_mark_if_necessary(old, m); 4259 4260 HeapRegion* r = heap_region_containing(old); 4261 if (!r->evacuation_failed()) { 4262 r->set_evacuation_failed(true); 4263 _hr_printer.evac_failure(r); 4264 } 4265 4266 push_on_evac_failure_scan_stack(old); 4267 4268 if (!_drain_in_progress) { 4269 // prevent recursion in copy_to_survivor_space() 4270 _drain_in_progress = true; 4271 drain_evac_failure_scan_stack(); 4272 _drain_in_progress = false; 4273 } 4274 } 4275 4276 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4277 assert(evacuation_failed(), "Oversaving!"); 4278 // We want to call the "for_promotion_failure" version only in the 4279 // case of a promotion failure. 4280 if (m->must_be_preserved_for_promotion_failure(obj)) { 4281 _objs_with_preserved_marks.push(obj); 4282 _preserved_marks_of_objs.push(m); 4283 } 4284 } 4285 4286 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4287 size_t word_size, 4288 AllocationContext_t context) { 4289 if (purpose == GCAllocForSurvived) { 4290 HeapWord* result = survivor_attempt_allocation(word_size, context); 4291 if (result != NULL) { 4292 return result; 4293 } else { 4294 // Let's try to allocate in the old gen in case we can fit the 4295 // object there. 4296 return old_attempt_allocation(word_size, context); 4297 } 4298 } else { 4299 assert(purpose == GCAllocForTenured, "sanity"); 4300 HeapWord* result = old_attempt_allocation(word_size, context); 4301 if (result != NULL) { 4302 return result; 4303 } else { 4304 // Let's try to allocate in the survivors in case we can fit the 4305 // object there. 4306 return survivor_attempt_allocation(word_size, context); 4307 } 4308 } 4309 4310 ShouldNotReachHere(); 4311 // Trying to keep some compilers happy. 4312 return NULL; 4313 } 4314 4315 void G1ParCopyHelper::mark_object(oop obj) { 4316 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet"); 4317 4318 // We know that the object is not moving so it's safe to read its size. 4319 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4320 } 4321 4322 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) { 4323 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4324 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4325 assert(from_obj != to_obj, "should not be self-forwarded"); 4326 4327 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet"); 4328 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet"); 4329 4330 // The object might be in the process of being copied by another 4331 // worker so we cannot trust that its to-space image is 4332 // well-formed. So we have to read its size from its from-space 4333 // image which we know should not be changing. 4334 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4335 } 4336 4337 template <class T> 4338 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4339 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4340 _scanned_klass->record_modified_oops(); 4341 } 4342 } 4343 4344 template <G1Barrier barrier, G1Mark do_mark_object> 4345 template <class T> 4346 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) { 4347 T heap_oop = oopDesc::load_heap_oop(p); 4348 4349 if (oopDesc::is_null(heap_oop)) { 4350 return; 4351 } 4352 4353 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 4354 4355 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4356 4357 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj); 4358 4359 if (state == G1CollectedHeap::InCSet) { 4360 oop forwardee; 4361 if (obj->is_forwarded()) { 4362 forwardee = obj->forwardee(); 4363 } else { 4364 forwardee = _par_scan_state->copy_to_survivor_space(obj); 4365 } 4366 assert(forwardee != NULL, "forwardee should not be NULL"); 4367 oopDesc::encode_store_heap_oop(p, forwardee); 4368 if (do_mark_object != G1MarkNone && forwardee != obj) { 4369 // If the object is self-forwarded we don't need to explicitly 4370 // mark it, the evacuation failure protocol will do so. 4371 mark_forwarded_object(obj, forwardee); 4372 } 4373 4374 if (barrier == G1BarrierKlass) { 4375 do_klass_barrier(p, forwardee); 4376 } 4377 } else { 4378 if (state == G1CollectedHeap::IsHumongous) { 4379 _g1->set_humongous_is_live(obj); 4380 } 4381 // The object is not in collection set. If we're a root scanning 4382 // closure during an initial mark pause then attempt to mark the object. 4383 if (do_mark_object == G1MarkFromRoot) { 4384 mark_object(obj); 4385 } 4386 } 4387 4388 if (barrier == G1BarrierEvac) { 4389 _par_scan_state->update_rs(_from, p, _worker_id); 4390 } 4391 } 4392 4393 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p); 4394 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p); 4395 4396 class G1ParEvacuateFollowersClosure : public VoidClosure { 4397 protected: 4398 G1CollectedHeap* _g1h; 4399 G1ParScanThreadState* _par_scan_state; 4400 RefToScanQueueSet* _queues; 4401 ParallelTaskTerminator* _terminator; 4402 4403 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4404 RefToScanQueueSet* queues() { return _queues; } 4405 ParallelTaskTerminator* terminator() { return _terminator; } 4406 4407 public: 4408 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4409 G1ParScanThreadState* par_scan_state, 4410 RefToScanQueueSet* queues, 4411 ParallelTaskTerminator* terminator) 4412 : _g1h(g1h), _par_scan_state(par_scan_state), 4413 _queues(queues), _terminator(terminator) {} 4414 4415 void do_void(); 4416 4417 private: 4418 inline bool offer_termination(); 4419 }; 4420 4421 bool G1ParEvacuateFollowersClosure::offer_termination() { 4422 G1ParScanThreadState* const pss = par_scan_state(); 4423 pss->start_term_time(); 4424 const bool res = terminator()->offer_termination(); 4425 pss->end_term_time(); 4426 return res; 4427 } 4428 4429 void G1ParEvacuateFollowersClosure::do_void() { 4430 G1ParScanThreadState* const pss = par_scan_state(); 4431 pss->trim_queue(); 4432 do { 4433 pss->steal_and_trim_queue(queues()); 4434 } while (!offer_termination()); 4435 } 4436 4437 class G1KlassScanClosure : public KlassClosure { 4438 G1ParCopyHelper* _closure; 4439 bool _process_only_dirty; 4440 int _count; 4441 public: 4442 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4443 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4444 void do_klass(Klass* klass) { 4445 // If the klass has not been dirtied we know that there's 4446 // no references into the young gen and we can skip it. 4447 if (!_process_only_dirty || klass->has_modified_oops()) { 4448 // Clean the klass since we're going to scavenge all the metadata. 4449 klass->clear_modified_oops(); 4450 4451 // Tell the closure that this klass is the Klass to scavenge 4452 // and is the one to dirty if oops are left pointing into the young gen. 4453 _closure->set_scanned_klass(klass); 4454 4455 klass->oops_do(_closure); 4456 4457 _closure->set_scanned_klass(NULL); 4458 } 4459 _count++; 4460 } 4461 }; 4462 4463 class G1CodeBlobClosure : public CodeBlobClosure { 4464 class HeapRegionGatheringOopClosure : public OopClosure { 4465 G1CollectedHeap* _g1h; 4466 OopClosure* _work; 4467 nmethod* _nm; 4468 4469 template <typename T> 4470 void do_oop_work(T* p) { 4471 _work->do_oop(p); 4472 T oop_or_narrowoop = oopDesc::load_heap_oop(p); 4473 if (!oopDesc::is_null(oop_or_narrowoop)) { 4474 oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop); 4475 HeapRegion* hr = _g1h->heap_region_containing_raw(o); 4476 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"); 4477 hr->add_strong_code_root(_nm); 4478 } 4479 } 4480 4481 public: 4482 HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {} 4483 4484 void do_oop(oop* o) { 4485 do_oop_work(o); 4486 } 4487 4488 void do_oop(narrowOop* o) { 4489 do_oop_work(o); 4490 } 4491 4492 void set_nm(nmethod* nm) { 4493 _nm = nm; 4494 } 4495 }; 4496 4497 HeapRegionGatheringOopClosure _oc; 4498 public: 4499 G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {} 4500 4501 void do_code_blob(CodeBlob* cb) { 4502 nmethod* nm = cb->as_nmethod_or_null(); 4503 if (nm != NULL) { 4504 if (!nm->test_set_oops_do_mark()) { 4505 _oc.set_nm(nm); 4506 nm->oops_do(&_oc); 4507 nm->fix_oop_relocations(); 4508 } 4509 } 4510 } 4511 }; 4512 4513 class G1ParTask : public AbstractGangTask { 4514 protected: 4515 G1CollectedHeap* _g1h; 4516 RefToScanQueueSet *_queues; 4517 ParallelTaskTerminator _terminator; 4518 uint _n_workers; 4519 4520 Mutex _stats_lock; 4521 Mutex* stats_lock() { return &_stats_lock; } 4522 4523 public: 4524 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues) 4525 : AbstractGangTask("G1 collection"), 4526 _g1h(g1h), 4527 _queues(task_queues), 4528 _terminator(0, _queues), 4529 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4530 {} 4531 4532 RefToScanQueueSet* queues() { return _queues; } 4533 4534 RefToScanQueue *work_queue(int i) { 4535 return queues()->queue(i); 4536 } 4537 4538 ParallelTaskTerminator* terminator() { return &_terminator; } 4539 4540 virtual void set_for_termination(int active_workers) { 4541 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4542 // in the young space (_par_seq_tasks) in the G1 heap 4543 // for SequentialSubTasksDone. 4544 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4545 // both of which need setting by set_n_termination(). 4546 _g1h->SharedHeap::set_n_termination(active_workers); 4547 _g1h->set_n_termination(active_workers); 4548 terminator()->reset_for_reuse(active_workers); 4549 _n_workers = active_workers; 4550 } 4551 4552 // Helps out with CLD processing. 4553 // 4554 // During InitialMark we need to: 4555 // 1) Scavenge all CLDs for the young GC. 4556 // 2) Mark all objects directly reachable from strong CLDs. 4557 template <G1Mark do_mark_object> 4558 class G1CLDClosure : public CLDClosure { 4559 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure; 4560 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure; 4561 G1KlassScanClosure _klass_in_cld_closure; 4562 bool _claim; 4563 4564 public: 4565 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure, 4566 bool only_young, bool claim) 4567 : _oop_closure(oop_closure), 4568 _oop_in_klass_closure(oop_closure->g1(), 4569 oop_closure->pss(), 4570 oop_closure->rp()), 4571 _klass_in_cld_closure(&_oop_in_klass_closure, only_young), 4572 _claim(claim) { 4573 4574 } 4575 4576 void do_cld(ClassLoaderData* cld) { 4577 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim); 4578 } 4579 }; 4580 4581 void work(uint worker_id) { 4582 if (worker_id >= _n_workers) return; // no work needed this round 4583 4584 double start_time_ms = os::elapsedTime() * 1000.0; 4585 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 4586 4587 { 4588 ResourceMark rm; 4589 HandleMark hm; 4590 4591 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4592 4593 G1ParScanThreadState pss(_g1h, worker_id, rp); 4594 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4595 4596 pss.set_evac_failure_closure(&evac_failure_cl); 4597 4598 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4599 4600 // Non-IM young GC. 4601 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp); 4602 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl, 4603 only_young, // Only process dirty klasses. 4604 false); // No need to claim CLDs. 4605 // IM young GC. 4606 // Strong roots closures. 4607 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp); 4608 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl, 4609 false, // Process all klasses. 4610 true); // Need to claim CLDs. 4611 // Weak roots closures. 4612 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp); 4613 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl, 4614 false, // Process all klasses. 4615 true); // Need to claim CLDs. 4616 4617 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl); 4618 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl); 4619 // IM Weak code roots are handled later. 4620 4621 OopClosure* strong_root_cl; 4622 OopClosure* weak_root_cl; 4623 CLDClosure* strong_cld_cl; 4624 CLDClosure* weak_cld_cl; 4625 CodeBlobClosure* strong_code_cl; 4626 4627 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4628 // We also need to mark copied objects. 4629 strong_root_cl = &scan_mark_root_cl; 4630 strong_cld_cl = &scan_mark_cld_cl; 4631 strong_code_cl = &scan_mark_code_cl; 4632 if (ClassUnloadingWithConcurrentMark) { 4633 weak_root_cl = &scan_mark_weak_root_cl; 4634 weak_cld_cl = &scan_mark_weak_cld_cl; 4635 } else { 4636 weak_root_cl = &scan_mark_root_cl; 4637 weak_cld_cl = &scan_mark_cld_cl; 4638 } 4639 } else { 4640 strong_root_cl = &scan_only_root_cl; 4641 weak_root_cl = &scan_only_root_cl; 4642 strong_cld_cl = &scan_only_cld_cl; 4643 weak_cld_cl = &scan_only_cld_cl; 4644 strong_code_cl = &scan_only_code_cl; 4645 } 4646 4647 4648 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4649 4650 pss.start_strong_roots(); 4651 _g1h->g1_process_roots(strong_root_cl, 4652 weak_root_cl, 4653 &push_heap_rs_cl, 4654 strong_cld_cl, 4655 weak_cld_cl, 4656 strong_code_cl, 4657 worker_id); 4658 4659 pss.end_strong_roots(); 4660 4661 { 4662 double start = os::elapsedTime(); 4663 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4664 evac.do_void(); 4665 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4666 double term_ms = pss.term_time()*1000.0; 4667 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 4668 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 4669 } 4670 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4671 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4672 4673 if (ParallelGCVerbose) { 4674 MutexLocker x(stats_lock()); 4675 pss.print_termination_stats(worker_id); 4676 } 4677 4678 assert(pss.queue_is_empty(), "should be empty"); 4679 4680 // Close the inner scope so that the ResourceMark and HandleMark 4681 // destructors are executed here and are included as part of the 4682 // "GC Worker Time". 4683 } 4684 4685 double end_time_ms = os::elapsedTime() * 1000.0; 4686 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 4687 } 4688 }; 4689 4690 // *** Common G1 Evacuation Stuff 4691 4692 // This method is run in a GC worker. 4693 4694 void 4695 G1CollectedHeap:: 4696 g1_process_roots(OopClosure* scan_non_heap_roots, 4697 OopClosure* scan_non_heap_weak_roots, 4698 OopsInHeapRegionClosure* scan_rs, 4699 CLDClosure* scan_strong_clds, 4700 CLDClosure* scan_weak_clds, 4701 CodeBlobClosure* scan_strong_code, 4702 uint worker_i) { 4703 4704 // First scan the shared roots. 4705 double ext_roots_start = os::elapsedTime(); 4706 double closure_app_time_sec = 0.0; 4707 4708 bool during_im = _g1h->g1_policy()->during_initial_mark_pause(); 4709 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark; 4710 4711 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 4712 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots); 4713 4714 process_roots(false, // no scoping; this is parallel code 4715 SharedHeap::SO_None, 4716 &buf_scan_non_heap_roots, 4717 &buf_scan_non_heap_weak_roots, 4718 scan_strong_clds, 4719 // Unloading Initial Marks handle the weak CLDs separately. 4720 (trace_metadata ? NULL : scan_weak_clds), 4721 scan_strong_code); 4722 4723 // Now the CM ref_processor roots. 4724 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 4725 // We need to treat the discovered reference lists of the 4726 // concurrent mark ref processor as roots and keep entries 4727 // (which are added by the marking threads) on them live 4728 // until they can be processed at the end of marking. 4729 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 4730 } 4731 4732 if (trace_metadata) { 4733 // Barrier to make sure all workers passed 4734 // the strong CLD and strong nmethods phases. 4735 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads()); 4736 4737 // Now take the complement of the strong CLDs. 4738 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds); 4739 } 4740 4741 // Finish up any enqueued closure apps (attributed as object copy time). 4742 buf_scan_non_heap_roots.done(); 4743 buf_scan_non_heap_weak_roots.done(); 4744 4745 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds() 4746 + buf_scan_non_heap_weak_roots.closure_app_seconds(); 4747 4748 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 4749 4750 double ext_root_time_ms = 4751 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 4752 4753 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 4754 4755 // During conc marking we have to filter the per-thread SATB buffers 4756 // to make sure we remove any oops into the CSet (which will show up 4757 // as implicitly live). 4758 double satb_filtering_ms = 0.0; 4759 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 4760 if (mark_in_progress()) { 4761 double satb_filter_start = os::elapsedTime(); 4762 4763 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 4764 4765 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 4766 } 4767 } 4768 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 4769 4770 // Now scan the complement of the collection set. 4771 G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots); 4772 4773 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i); 4774 4775 _process_strong_tasks->all_tasks_completed(); 4776 } 4777 4778 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4779 private: 4780 BoolObjectClosure* _is_alive; 4781 int _initial_string_table_size; 4782 int _initial_symbol_table_size; 4783 4784 bool _process_strings; 4785 int _strings_processed; 4786 int _strings_removed; 4787 4788 bool _process_symbols; 4789 int _symbols_processed; 4790 int _symbols_removed; 4791 4792 bool _do_in_parallel; 4793 public: 4794 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4795 AbstractGangTask("String/Symbol Unlinking"), 4796 _is_alive(is_alive), 4797 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()), 4798 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4799 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4800 4801 _initial_string_table_size = StringTable::the_table()->table_size(); 4802 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4803 if (process_strings) { 4804 StringTable::clear_parallel_claimed_index(); 4805 } 4806 if (process_symbols) { 4807 SymbolTable::clear_parallel_claimed_index(); 4808 } 4809 } 4810 4811 ~G1StringSymbolTableUnlinkTask() { 4812 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4813 err_msg("claim value %d after unlink less than initial string table size %d", 4814 StringTable::parallel_claimed_index(), _initial_string_table_size)); 4815 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4816 err_msg("claim value %d after unlink less than initial symbol table size %d", 4817 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size)); 4818 4819 if (G1TraceStringSymbolTableScrubbing) { 4820 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4821 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, " 4822 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed", 4823 strings_processed(), strings_removed(), 4824 symbols_processed(), symbols_removed()); 4825 } 4826 } 4827 4828 void work(uint worker_id) { 4829 if (_do_in_parallel) { 4830 int strings_processed = 0; 4831 int strings_removed = 0; 4832 int symbols_processed = 0; 4833 int symbols_removed = 0; 4834 if (_process_strings) { 4835 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4836 Atomic::add(strings_processed, &_strings_processed); 4837 Atomic::add(strings_removed, &_strings_removed); 4838 } 4839 if (_process_symbols) { 4840 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4841 Atomic::add(symbols_processed, &_symbols_processed); 4842 Atomic::add(symbols_removed, &_symbols_removed); 4843 } 4844 } else { 4845 if (_process_strings) { 4846 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed); 4847 } 4848 if (_process_symbols) { 4849 SymbolTable::unlink(&_symbols_processed, &_symbols_removed); 4850 } 4851 } 4852 } 4853 4854 size_t strings_processed() const { return (size_t)_strings_processed; } 4855 size_t strings_removed() const { return (size_t)_strings_removed; } 4856 4857 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4858 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4859 }; 4860 4861 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4862 private: 4863 static Monitor* _lock; 4864 4865 BoolObjectClosure* const _is_alive; 4866 const bool _unloading_occurred; 4867 const uint _num_workers; 4868 4869 // Variables used to claim nmethods. 4870 nmethod* _first_nmethod; 4871 volatile nmethod* _claimed_nmethod; 4872 4873 // The list of nmethods that need to be processed by the second pass. 4874 volatile nmethod* _postponed_list; 4875 volatile uint _num_entered_barrier; 4876 4877 public: 4878 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4879 _is_alive(is_alive), 4880 _unloading_occurred(unloading_occurred), 4881 _num_workers(num_workers), 4882 _first_nmethod(NULL), 4883 _claimed_nmethod(NULL), 4884 _postponed_list(NULL), 4885 _num_entered_barrier(0) 4886 { 4887 nmethod::increase_unloading_clock(); 4888 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first()); 4889 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4890 } 4891 4892 ~G1CodeCacheUnloadingTask() { 4893 CodeCache::verify_clean_inline_caches(); 4894 4895 CodeCache::set_needs_cache_clean(false); 4896 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4897 4898 CodeCache::verify_icholder_relocations(); 4899 } 4900 4901 private: 4902 void add_to_postponed_list(nmethod* nm) { 4903 nmethod* old; 4904 do { 4905 old = (nmethod*)_postponed_list; 4906 nm->set_unloading_next(old); 4907 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4908 } 4909 4910 void clean_nmethod(nmethod* nm) { 4911 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4912 4913 if (postponed) { 4914 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4915 add_to_postponed_list(nm); 4916 } 4917 4918 // Mark that this thread has been cleaned/unloaded. 4919 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4920 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4921 } 4922 4923 void clean_nmethod_postponed(nmethod* nm) { 4924 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4925 } 4926 4927 static const int MaxClaimNmethods = 16; 4928 4929 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4930 nmethod* first; 4931 nmethod* last; 4932 4933 do { 4934 *num_claimed_nmethods = 0; 4935 4936 first = last = (nmethod*)_claimed_nmethod; 4937 4938 if (first != NULL) { 4939 for (int i = 0; i < MaxClaimNmethods; i++) { 4940 last = CodeCache::alive_nmethod(CodeCache::next(last)); 4941 4942 if (last == NULL) { 4943 break; 4944 } 4945 4946 claimed_nmethods[i] = last; 4947 (*num_claimed_nmethods)++; 4948 } 4949 } 4950 4951 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first); 4952 } 4953 4954 nmethod* claim_postponed_nmethod() { 4955 nmethod* claim; 4956 nmethod* next; 4957 4958 do { 4959 claim = (nmethod*)_postponed_list; 4960 if (claim == NULL) { 4961 return NULL; 4962 } 4963 4964 next = claim->unloading_next(); 4965 4966 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4967 4968 return claim; 4969 } 4970 4971 public: 4972 // Mark that we're done with the first pass of nmethod cleaning. 4973 void barrier_mark(uint worker_id) { 4974 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4975 _num_entered_barrier++; 4976 if (_num_entered_barrier == _num_workers) { 4977 ml.notify_all(); 4978 } 4979 } 4980 4981 // See if we have to wait for the other workers to 4982 // finish their first-pass nmethod cleaning work. 4983 void barrier_wait(uint worker_id) { 4984 if (_num_entered_barrier < _num_workers) { 4985 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4986 while (_num_entered_barrier < _num_workers) { 4987 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4988 } 4989 } 4990 } 4991 4992 // Cleaning and unloading of nmethods. Some work has to be postponed 4993 // to the second pass, when we know which nmethods survive. 4994 void work_first_pass(uint worker_id) { 4995 // The first nmethods is claimed by the first worker. 4996 if (worker_id == 0 && _first_nmethod != NULL) { 4997 clean_nmethod(_first_nmethod); 4998 _first_nmethod = NULL; 4999 } 5000 5001 int num_claimed_nmethods; 5002 nmethod* claimed_nmethods[MaxClaimNmethods]; 5003 5004 while (true) { 5005 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 5006 5007 if (num_claimed_nmethods == 0) { 5008 break; 5009 } 5010 5011 for (int i = 0; i < num_claimed_nmethods; i++) { 5012 clean_nmethod(claimed_nmethods[i]); 5013 } 5014 } 5015 } 5016 5017 void work_second_pass(uint worker_id) { 5018 nmethod* nm; 5019 // Take care of postponed nmethods. 5020 while ((nm = claim_postponed_nmethod()) != NULL) { 5021 clean_nmethod_postponed(nm); 5022 } 5023 } 5024 }; 5025 5026 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock"); 5027 5028 class G1KlassCleaningTask : public StackObj { 5029 BoolObjectClosure* _is_alive; 5030 volatile jint _clean_klass_tree_claimed; 5031 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 5032 5033 public: 5034 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 5035 _is_alive(is_alive), 5036 _clean_klass_tree_claimed(0), 5037 _klass_iterator() { 5038 } 5039 5040 private: 5041 bool claim_clean_klass_tree_task() { 5042 if (_clean_klass_tree_claimed) { 5043 return false; 5044 } 5045 5046 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 5047 } 5048 5049 InstanceKlass* claim_next_klass() { 5050 Klass* klass; 5051 do { 5052 klass =_klass_iterator.next_klass(); 5053 } while (klass != NULL && !klass->oop_is_instance()); 5054 5055 return (InstanceKlass*)klass; 5056 } 5057 5058 public: 5059 5060 void clean_klass(InstanceKlass* ik) { 5061 ik->clean_implementors_list(_is_alive); 5062 ik->clean_method_data(_is_alive); 5063 5064 // G1 specific cleanup work that has 5065 // been moved here to be done in parallel. 5066 ik->clean_dependent_nmethods(); 5067 } 5068 5069 void work() { 5070 ResourceMark rm; 5071 5072 // One worker will clean the subklass/sibling klass tree. 5073 if (claim_clean_klass_tree_task()) { 5074 Klass::clean_subklass_tree(_is_alive); 5075 } 5076 5077 // All workers will help cleaning the classes, 5078 InstanceKlass* klass; 5079 while ((klass = claim_next_klass()) != NULL) { 5080 clean_klass(klass); 5081 } 5082 } 5083 }; 5084 5085 // To minimize the remark pause times, the tasks below are done in parallel. 5086 class G1ParallelCleaningTask : public AbstractGangTask { 5087 private: 5088 G1StringSymbolTableUnlinkTask _string_symbol_task; 5089 G1CodeCacheUnloadingTask _code_cache_task; 5090 G1KlassCleaningTask _klass_cleaning_task; 5091 5092 public: 5093 // The constructor is run in the VMThread. 5094 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 5095 AbstractGangTask("Parallel Cleaning"), 5096 _string_symbol_task(is_alive, process_strings, process_symbols), 5097 _code_cache_task(num_workers, is_alive, unloading_occurred), 5098 _klass_cleaning_task(is_alive) { 5099 } 5100 5101 // The parallel work done by all worker threads. 5102 void work(uint worker_id) { 5103 // Do first pass of code cache cleaning. 5104 _code_cache_task.work_first_pass(worker_id); 5105 5106 // Let the threads mark that the first pass is done. 5107 _code_cache_task.barrier_mark(worker_id); 5108 5109 // Clean the Strings and Symbols. 5110 _string_symbol_task.work(worker_id); 5111 5112 // Wait for all workers to finish the first code cache cleaning pass. 5113 _code_cache_task.barrier_wait(worker_id); 5114 5115 // Do the second code cache cleaning work, which realize on 5116 // the liveness information gathered during the first pass. 5117 _code_cache_task.work_second_pass(worker_id); 5118 5119 // Clean all klasses that were not unloaded. 5120 _klass_cleaning_task.work(); 5121 } 5122 }; 5123 5124 5125 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 5126 bool process_strings, 5127 bool process_symbols, 5128 bool class_unloading_occurred) { 5129 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5130 workers()->active_workers() : 1); 5131 5132 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 5133 n_workers, class_unloading_occurred); 5134 if (G1CollectedHeap::use_parallel_gc_threads()) { 5135 set_par_threads(n_workers); 5136 workers()->run_task(&g1_unlink_task); 5137 set_par_threads(0); 5138 } else { 5139 g1_unlink_task.work(0); 5140 } 5141 } 5142 5143 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 5144 bool process_strings, bool process_symbols) { 5145 { 5146 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5147 _g1h->workers()->active_workers() : 1); 5148 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 5149 if (G1CollectedHeap::use_parallel_gc_threads()) { 5150 set_par_threads(n_workers); 5151 workers()->run_task(&g1_unlink_task); 5152 set_par_threads(0); 5153 } else { 5154 g1_unlink_task.work(0); 5155 } 5156 } 5157 5158 if (G1StringDedup::is_enabled()) { 5159 G1StringDedup::unlink(is_alive); 5160 } 5161 } 5162 5163 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 5164 private: 5165 DirtyCardQueueSet* _queue; 5166 public: 5167 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 5168 5169 virtual void work(uint worker_id) { 5170 double start_time = os::elapsedTime(); 5171 5172 RedirtyLoggedCardTableEntryClosure cl; 5173 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) { 5174 _queue->par_apply_closure_to_all_completed_buffers(&cl); 5175 } else { 5176 _queue->apply_closure_to_all_completed_buffers(&cl); 5177 } 5178 5179 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 5180 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0); 5181 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed()); 5182 } 5183 }; 5184 5185 void G1CollectedHeap::redirty_logged_cards() { 5186 double redirty_logged_cards_start = os::elapsedTime(); 5187 5188 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5189 _g1h->workers()->active_workers() : 1); 5190 5191 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 5192 dirty_card_queue_set().reset_for_par_iteration(); 5193 if (use_parallel_gc_threads()) { 5194 set_par_threads(n_workers); 5195 workers()->run_task(&redirty_task); 5196 set_par_threads(0); 5197 } else { 5198 redirty_task.work(0); 5199 } 5200 5201 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5202 dcq.merge_bufferlists(&dirty_card_queue_set()); 5203 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5204 5205 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 5206 } 5207 5208 // Weak Reference Processing support 5209 5210 // An always "is_alive" closure that is used to preserve referents. 5211 // If the object is non-null then it's alive. Used in the preservation 5212 // of referent objects that are pointed to by reference objects 5213 // discovered by the CM ref processor. 5214 class G1AlwaysAliveClosure: public BoolObjectClosure { 5215 G1CollectedHeap* _g1; 5216 public: 5217 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5218 bool do_object_b(oop p) { 5219 if (p != NULL) { 5220 return true; 5221 } 5222 return false; 5223 } 5224 }; 5225 5226 bool G1STWIsAliveClosure::do_object_b(oop p) { 5227 // An object is reachable if it is outside the collection set, 5228 // or is inside and copied. 5229 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5230 } 5231 5232 // Non Copying Keep Alive closure 5233 class G1KeepAliveClosure: public OopClosure { 5234 G1CollectedHeap* _g1; 5235 public: 5236 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5237 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5238 void do_oop(oop* p) { 5239 oop obj = *p; 5240 assert(obj != NULL, "the caller should have filtered out NULL values"); 5241 5242 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj); 5243 if (cset_state == G1CollectedHeap::InNeither) { 5244 return; 5245 } 5246 if (cset_state == G1CollectedHeap::InCSet) { 5247 assert( obj->is_forwarded(), "invariant" ); 5248 *p = obj->forwardee(); 5249 } else { 5250 assert(!obj->is_forwarded(), "invariant" ); 5251 assert(cset_state == G1CollectedHeap::IsHumongous, 5252 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state)); 5253 _g1->set_humongous_is_live(obj); 5254 } 5255 } 5256 }; 5257 5258 // Copying Keep Alive closure - can be called from both 5259 // serial and parallel code as long as different worker 5260 // threads utilize different G1ParScanThreadState instances 5261 // and different queues. 5262 5263 class G1CopyingKeepAliveClosure: public OopClosure { 5264 G1CollectedHeap* _g1h; 5265 OopClosure* _copy_non_heap_obj_cl; 5266 G1ParScanThreadState* _par_scan_state; 5267 5268 public: 5269 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5270 OopClosure* non_heap_obj_cl, 5271 G1ParScanThreadState* pss): 5272 _g1h(g1h), 5273 _copy_non_heap_obj_cl(non_heap_obj_cl), 5274 _par_scan_state(pss) 5275 {} 5276 5277 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5278 virtual void do_oop( oop* p) { do_oop_work(p); } 5279 5280 template <class T> void do_oop_work(T* p) { 5281 oop obj = oopDesc::load_decode_heap_oop(p); 5282 5283 if (_g1h->is_in_cset_or_humongous(obj)) { 5284 // If the referent object has been forwarded (either copied 5285 // to a new location or to itself in the event of an 5286 // evacuation failure) then we need to update the reference 5287 // field and, if both reference and referent are in the G1 5288 // heap, update the RSet for the referent. 5289 // 5290 // If the referent has not been forwarded then we have to keep 5291 // it alive by policy. Therefore we have copy the referent. 5292 // 5293 // If the reference field is in the G1 heap then we can push 5294 // on the PSS queue. When the queue is drained (after each 5295 // phase of reference processing) the object and it's followers 5296 // will be copied, the reference field set to point to the 5297 // new location, and the RSet updated. Otherwise we need to 5298 // use the the non-heap or metadata closures directly to copy 5299 // the referent object and update the pointer, while avoiding 5300 // updating the RSet. 5301 5302 if (_g1h->is_in_g1_reserved(p)) { 5303 _par_scan_state->push_on_queue(p); 5304 } else { 5305 assert(!Metaspace::contains((const void*)p), 5306 err_msg("Unexpectedly found a pointer from metadata: " 5307 PTR_FORMAT, p)); 5308 _copy_non_heap_obj_cl->do_oop(p); 5309 } 5310 } 5311 } 5312 }; 5313 5314 // Serial drain queue closure. Called as the 'complete_gc' 5315 // closure for each discovered list in some of the 5316 // reference processing phases. 5317 5318 class G1STWDrainQueueClosure: public VoidClosure { 5319 protected: 5320 G1CollectedHeap* _g1h; 5321 G1ParScanThreadState* _par_scan_state; 5322 5323 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5324 5325 public: 5326 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5327 _g1h(g1h), 5328 _par_scan_state(pss) 5329 { } 5330 5331 void do_void() { 5332 G1ParScanThreadState* const pss = par_scan_state(); 5333 pss->trim_queue(); 5334 } 5335 }; 5336 5337 // Parallel Reference Processing closures 5338 5339 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5340 // processing during G1 evacuation pauses. 5341 5342 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5343 private: 5344 G1CollectedHeap* _g1h; 5345 RefToScanQueueSet* _queues; 5346 FlexibleWorkGang* _workers; 5347 int _active_workers; 5348 5349 public: 5350 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5351 FlexibleWorkGang* workers, 5352 RefToScanQueueSet *task_queues, 5353 int n_workers) : 5354 _g1h(g1h), 5355 _queues(task_queues), 5356 _workers(workers), 5357 _active_workers(n_workers) 5358 { 5359 assert(n_workers > 0, "shouldn't call this otherwise"); 5360 } 5361 5362 // Executes the given task using concurrent marking worker threads. 5363 virtual void execute(ProcessTask& task); 5364 virtual void execute(EnqueueTask& task); 5365 }; 5366 5367 // Gang task for possibly parallel reference processing 5368 5369 class G1STWRefProcTaskProxy: public AbstractGangTask { 5370 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5371 ProcessTask& _proc_task; 5372 G1CollectedHeap* _g1h; 5373 RefToScanQueueSet *_task_queues; 5374 ParallelTaskTerminator* _terminator; 5375 5376 public: 5377 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5378 G1CollectedHeap* g1h, 5379 RefToScanQueueSet *task_queues, 5380 ParallelTaskTerminator* terminator) : 5381 AbstractGangTask("Process reference objects in parallel"), 5382 _proc_task(proc_task), 5383 _g1h(g1h), 5384 _task_queues(task_queues), 5385 _terminator(terminator) 5386 {} 5387 5388 virtual void work(uint worker_id) { 5389 // The reference processing task executed by a single worker. 5390 ResourceMark rm; 5391 HandleMark hm; 5392 5393 G1STWIsAliveClosure is_alive(_g1h); 5394 5395 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5396 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5397 5398 pss.set_evac_failure_closure(&evac_failure_cl); 5399 5400 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5401 5402 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5403 5404 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5405 5406 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5407 // We also need to mark copied objects. 5408 copy_non_heap_cl = ©_mark_non_heap_cl; 5409 } 5410 5411 // Keep alive closure. 5412 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5413 5414 // Complete GC closure 5415 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5416 5417 // Call the reference processing task's work routine. 5418 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5419 5420 // Note we cannot assert that the refs array is empty here as not all 5421 // of the processing tasks (specifically phase2 - pp2_work) execute 5422 // the complete_gc closure (which ordinarily would drain the queue) so 5423 // the queue may not be empty. 5424 } 5425 }; 5426 5427 // Driver routine for parallel reference processing. 5428 // Creates an instance of the ref processing gang 5429 // task and has the worker threads execute it. 5430 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5431 assert(_workers != NULL, "Need parallel worker threads."); 5432 5433 ParallelTaskTerminator terminator(_active_workers, _queues); 5434 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5435 5436 _g1h->set_par_threads(_active_workers); 5437 _workers->run_task(&proc_task_proxy); 5438 _g1h->set_par_threads(0); 5439 } 5440 5441 // Gang task for parallel reference enqueueing. 5442 5443 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5444 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5445 EnqueueTask& _enq_task; 5446 5447 public: 5448 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5449 AbstractGangTask("Enqueue reference objects in parallel"), 5450 _enq_task(enq_task) 5451 { } 5452 5453 virtual void work(uint worker_id) { 5454 _enq_task.work(worker_id); 5455 } 5456 }; 5457 5458 // Driver routine for parallel reference enqueueing. 5459 // Creates an instance of the ref enqueueing gang 5460 // task and has the worker threads execute it. 5461 5462 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5463 assert(_workers != NULL, "Need parallel worker threads."); 5464 5465 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5466 5467 _g1h->set_par_threads(_active_workers); 5468 _workers->run_task(&enq_task_proxy); 5469 _g1h->set_par_threads(0); 5470 } 5471 5472 // End of weak reference support closures 5473 5474 // Abstract task used to preserve (i.e. copy) any referent objects 5475 // that are in the collection set and are pointed to by reference 5476 // objects discovered by the CM ref processor. 5477 5478 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5479 protected: 5480 G1CollectedHeap* _g1h; 5481 RefToScanQueueSet *_queues; 5482 ParallelTaskTerminator _terminator; 5483 uint _n_workers; 5484 5485 public: 5486 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5487 AbstractGangTask("ParPreserveCMReferents"), 5488 _g1h(g1h), 5489 _queues(task_queues), 5490 _terminator(workers, _queues), 5491 _n_workers(workers) 5492 { } 5493 5494 void work(uint worker_id) { 5495 ResourceMark rm; 5496 HandleMark hm; 5497 5498 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5499 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5500 5501 pss.set_evac_failure_closure(&evac_failure_cl); 5502 5503 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5504 5505 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5506 5507 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5508 5509 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5510 5511 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5512 // We also need to mark copied objects. 5513 copy_non_heap_cl = ©_mark_non_heap_cl; 5514 } 5515 5516 // Is alive closure 5517 G1AlwaysAliveClosure always_alive(_g1h); 5518 5519 // Copying keep alive closure. Applied to referent objects that need 5520 // to be copied. 5521 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5522 5523 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5524 5525 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5526 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5527 5528 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5529 // So this must be true - but assert just in case someone decides to 5530 // change the worker ids. 5531 assert(0 <= worker_id && worker_id < limit, "sanity"); 5532 assert(!rp->discovery_is_atomic(), "check this code"); 5533 5534 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5535 for (uint idx = worker_id; idx < limit; idx += stride) { 5536 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5537 5538 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5539 while (iter.has_next()) { 5540 // Since discovery is not atomic for the CM ref processor, we 5541 // can see some null referent objects. 5542 iter.load_ptrs(DEBUG_ONLY(true)); 5543 oop ref = iter.obj(); 5544 5545 // This will filter nulls. 5546 if (iter.is_referent_alive()) { 5547 iter.make_referent_alive(); 5548 } 5549 iter.move_to_next(); 5550 } 5551 } 5552 5553 // Drain the queue - which may cause stealing 5554 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5555 drain_queue.do_void(); 5556 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5557 assert(pss.queue_is_empty(), "should be"); 5558 } 5559 }; 5560 5561 // Weak Reference processing during an evacuation pause (part 1). 5562 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5563 double ref_proc_start = os::elapsedTime(); 5564 5565 ReferenceProcessor* rp = _ref_processor_stw; 5566 assert(rp->discovery_enabled(), "should have been enabled"); 5567 5568 // Any reference objects, in the collection set, that were 'discovered' 5569 // by the CM ref processor should have already been copied (either by 5570 // applying the external root copy closure to the discovered lists, or 5571 // by following an RSet entry). 5572 // 5573 // But some of the referents, that are in the collection set, that these 5574 // reference objects point to may not have been copied: the STW ref 5575 // processor would have seen that the reference object had already 5576 // been 'discovered' and would have skipped discovering the reference, 5577 // but would not have treated the reference object as a regular oop. 5578 // As a result the copy closure would not have been applied to the 5579 // referent object. 5580 // 5581 // We need to explicitly copy these referent objects - the references 5582 // will be processed at the end of remarking. 5583 // 5584 // We also need to do this copying before we process the reference 5585 // objects discovered by the STW ref processor in case one of these 5586 // referents points to another object which is also referenced by an 5587 // object discovered by the STW ref processor. 5588 5589 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5590 no_of_gc_workers == workers()->active_workers(), 5591 "Need to reset active GC workers"); 5592 5593 set_par_threads(no_of_gc_workers); 5594 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5595 no_of_gc_workers, 5596 _task_queues); 5597 5598 if (G1CollectedHeap::use_parallel_gc_threads()) { 5599 workers()->run_task(&keep_cm_referents); 5600 } else { 5601 keep_cm_referents.work(0); 5602 } 5603 5604 set_par_threads(0); 5605 5606 // Closure to test whether a referent is alive. 5607 G1STWIsAliveClosure is_alive(this); 5608 5609 // Even when parallel reference processing is enabled, the processing 5610 // of JNI refs is serial and performed serially by the current thread 5611 // rather than by a worker. The following PSS will be used for processing 5612 // JNI refs. 5613 5614 // Use only a single queue for this PSS. 5615 G1ParScanThreadState pss(this, 0, NULL); 5616 5617 // We do not embed a reference processor in the copying/scanning 5618 // closures while we're actually processing the discovered 5619 // reference objects. 5620 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5621 5622 pss.set_evac_failure_closure(&evac_failure_cl); 5623 5624 assert(pss.queue_is_empty(), "pre-condition"); 5625 5626 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5627 5628 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5629 5630 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5631 5632 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5633 // We also need to mark copied objects. 5634 copy_non_heap_cl = ©_mark_non_heap_cl; 5635 } 5636 5637 // Keep alive closure. 5638 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss); 5639 5640 // Serial Complete GC closure 5641 G1STWDrainQueueClosure drain_queue(this, &pss); 5642 5643 // Setup the soft refs policy... 5644 rp->setup_policy(false); 5645 5646 ReferenceProcessorStats stats; 5647 if (!rp->processing_is_mt()) { 5648 // Serial reference processing... 5649 stats = rp->process_discovered_references(&is_alive, 5650 &keep_alive, 5651 &drain_queue, 5652 NULL, 5653 _gc_timer_stw, 5654 _gc_tracer_stw->gc_id()); 5655 } else { 5656 // Parallel reference processing 5657 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5658 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5659 5660 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5661 stats = rp->process_discovered_references(&is_alive, 5662 &keep_alive, 5663 &drain_queue, 5664 &par_task_executor, 5665 _gc_timer_stw, 5666 _gc_tracer_stw->gc_id()); 5667 } 5668 5669 _gc_tracer_stw->report_gc_reference_stats(stats); 5670 5671 // We have completed copying any necessary live referent objects. 5672 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5673 5674 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5675 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5676 } 5677 5678 // Weak Reference processing during an evacuation pause (part 2). 5679 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5680 double ref_enq_start = os::elapsedTime(); 5681 5682 ReferenceProcessor* rp = _ref_processor_stw; 5683 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5684 5685 // Now enqueue any remaining on the discovered lists on to 5686 // the pending list. 5687 if (!rp->processing_is_mt()) { 5688 // Serial reference processing... 5689 rp->enqueue_discovered_references(); 5690 } else { 5691 // Parallel reference enqueueing 5692 5693 assert(no_of_gc_workers == workers()->active_workers(), 5694 "Need to reset active workers"); 5695 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5696 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5697 5698 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5699 rp->enqueue_discovered_references(&par_task_executor); 5700 } 5701 5702 rp->verify_no_references_recorded(); 5703 assert(!rp->discovery_enabled(), "should have been disabled"); 5704 5705 // FIXME 5706 // CM's reference processing also cleans up the string and symbol tables. 5707 // Should we do that here also? We could, but it is a serial operation 5708 // and could significantly increase the pause time. 5709 5710 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5711 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5712 } 5713 5714 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) { 5715 _expand_heap_after_alloc_failure = true; 5716 _evacuation_failed = false; 5717 5718 // Should G1EvacuationFailureALot be in effect for this GC? 5719 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5720 5721 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5722 5723 // Disable the hot card cache. 5724 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5725 hot_card_cache->reset_hot_cache_claimed_index(); 5726 hot_card_cache->set_use_cache(false); 5727 5728 uint n_workers; 5729 if (G1CollectedHeap::use_parallel_gc_threads()) { 5730 n_workers = 5731 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5732 workers()->active_workers(), 5733 Threads::number_of_non_daemon_threads()); 5734 assert(UseDynamicNumberOfGCThreads || 5735 n_workers == workers()->total_workers(), 5736 "If not dynamic should be using all the workers"); 5737 workers()->set_active_workers(n_workers); 5738 set_par_threads(n_workers); 5739 } else { 5740 assert(n_par_threads() == 0, 5741 "Should be the original non-parallel value"); 5742 n_workers = 1; 5743 } 5744 5745 G1ParTask g1_par_task(this, _task_queues); 5746 5747 init_for_evac_failure(NULL); 5748 5749 rem_set()->prepare_for_younger_refs_iterate(true); 5750 5751 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5752 double start_par_time_sec = os::elapsedTime(); 5753 double end_par_time_sec; 5754 5755 { 5756 StrongRootsScope srs(this); 5757 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5758 if (g1_policy()->during_initial_mark_pause()) { 5759 ClassLoaderDataGraph::clear_claimed_marks(); 5760 } 5761 5762 if (G1CollectedHeap::use_parallel_gc_threads()) { 5763 // The individual threads will set their evac-failure closures. 5764 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5765 // These tasks use ShareHeap::_process_strong_tasks 5766 assert(UseDynamicNumberOfGCThreads || 5767 workers()->active_workers() == workers()->total_workers(), 5768 "If not dynamic should be using all the workers"); 5769 workers()->run_task(&g1_par_task); 5770 } else { 5771 g1_par_task.set_for_termination(n_workers); 5772 g1_par_task.work(0); 5773 } 5774 end_par_time_sec = os::elapsedTime(); 5775 5776 // Closing the inner scope will execute the destructor 5777 // for the StrongRootsScope object. We record the current 5778 // elapsed time before closing the scope so that time 5779 // taken for the SRS destructor is NOT included in the 5780 // reported parallel time. 5781 } 5782 5783 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5784 g1_policy()->phase_times()->record_par_time(par_time_ms); 5785 5786 double code_root_fixup_time_ms = 5787 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5788 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5789 5790 set_par_threads(0); 5791 5792 // Process any discovered reference objects - we have 5793 // to do this _before_ we retire the GC alloc regions 5794 // as we may have to copy some 'reachable' referent 5795 // objects (and their reachable sub-graphs) that were 5796 // not copied during the pause. 5797 process_discovered_references(n_workers); 5798 5799 // Weak root processing. 5800 { 5801 G1STWIsAliveClosure is_alive(this); 5802 G1KeepAliveClosure keep_alive(this); 5803 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5804 if (G1StringDedup::is_enabled()) { 5805 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive); 5806 } 5807 } 5808 5809 _allocator->release_gc_alloc_regions(n_workers, evacuation_info); 5810 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5811 5812 // Reset and re-enable the hot card cache. 5813 // Note the counts for the cards in the regions in the 5814 // collection set are reset when the collection set is freed. 5815 hot_card_cache->reset_hot_cache(); 5816 hot_card_cache->set_use_cache(true); 5817 5818 purge_code_root_memory(); 5819 5820 finalize_for_evac_failure(); 5821 5822 if (evacuation_failed()) { 5823 remove_self_forwarding_pointers(); 5824 5825 // Reset the G1EvacuationFailureALot counters and flags 5826 // Note: the values are reset only when an actual 5827 // evacuation failure occurs. 5828 NOT_PRODUCT(reset_evacuation_should_fail();) 5829 } 5830 5831 // Enqueue any remaining references remaining on the STW 5832 // reference processor's discovered lists. We need to do 5833 // this after the card table is cleaned (and verified) as 5834 // the act of enqueueing entries on to the pending list 5835 // will log these updates (and dirty their associated 5836 // cards). We need these updates logged to update any 5837 // RSets. 5838 enqueue_discovered_references(n_workers); 5839 5840 redirty_logged_cards(); 5841 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5842 } 5843 5844 void G1CollectedHeap::free_region(HeapRegion* hr, 5845 FreeRegionList* free_list, 5846 bool par, 5847 bool locked) { 5848 assert(!hr->is_free(), "the region should not be free"); 5849 assert(!hr->is_empty(), "the region should not be empty"); 5850 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5851 assert(free_list != NULL, "pre-condition"); 5852 5853 if (G1VerifyBitmaps) { 5854 MemRegion mr(hr->bottom(), hr->end()); 5855 concurrent_mark()->clearRangePrevBitmap(mr); 5856 } 5857 5858 // Clear the card counts for this region. 5859 // Note: we only need to do this if the region is not young 5860 // (since we don't refine cards in young regions). 5861 if (!hr->is_young()) { 5862 _cg1r->hot_card_cache()->reset_card_counts(hr); 5863 } 5864 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5865 free_list->add_ordered(hr); 5866 } 5867 5868 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5869 FreeRegionList* free_list, 5870 bool par) { 5871 assert(hr->is_starts_humongous(), "this is only for starts humongous regions"); 5872 assert(free_list != NULL, "pre-condition"); 5873 5874 size_t hr_capacity = hr->capacity(); 5875 // We need to read this before we make the region non-humongous, 5876 // otherwise the information will be gone. 5877 uint last_index = hr->last_hc_index(); 5878 hr->clear_humongous(); 5879 free_region(hr, free_list, par); 5880 5881 uint i = hr->hrm_index() + 1; 5882 while (i < last_index) { 5883 HeapRegion* curr_hr = region_at(i); 5884 assert(curr_hr->is_continues_humongous(), "invariant"); 5885 curr_hr->clear_humongous(); 5886 free_region(curr_hr, free_list, par); 5887 i += 1; 5888 } 5889 } 5890 5891 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 5892 const HeapRegionSetCount& humongous_regions_removed) { 5893 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 5894 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5895 _old_set.bulk_remove(old_regions_removed); 5896 _humongous_set.bulk_remove(humongous_regions_removed); 5897 } 5898 5899 } 5900 5901 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5902 assert(list != NULL, "list can't be null"); 5903 if (!list->is_empty()) { 5904 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5905 _hrm.insert_list_into_free_list(list); 5906 } 5907 } 5908 5909 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5910 _allocator->decrease_used(bytes); 5911 } 5912 5913 class G1ParCleanupCTTask : public AbstractGangTask { 5914 G1SATBCardTableModRefBS* _ct_bs; 5915 G1CollectedHeap* _g1h; 5916 HeapRegion* volatile _su_head; 5917 public: 5918 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5919 G1CollectedHeap* g1h) : 5920 AbstractGangTask("G1 Par Cleanup CT Task"), 5921 _ct_bs(ct_bs), _g1h(g1h) { } 5922 5923 void work(uint worker_id) { 5924 HeapRegion* r; 5925 while (r = _g1h->pop_dirty_cards_region()) { 5926 clear_cards(r); 5927 } 5928 } 5929 5930 void clear_cards(HeapRegion* r) { 5931 // Cards of the survivors should have already been dirtied. 5932 if (!r->is_survivor()) { 5933 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5934 } 5935 } 5936 }; 5937 5938 #ifndef PRODUCT 5939 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5940 G1CollectedHeap* _g1h; 5941 G1SATBCardTableModRefBS* _ct_bs; 5942 public: 5943 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5944 : _g1h(g1h), _ct_bs(ct_bs) { } 5945 virtual bool doHeapRegion(HeapRegion* r) { 5946 if (r->is_survivor()) { 5947 _g1h->verify_dirty_region(r); 5948 } else { 5949 _g1h->verify_not_dirty_region(r); 5950 } 5951 return false; 5952 } 5953 }; 5954 5955 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5956 // All of the region should be clean. 5957 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5958 MemRegion mr(hr->bottom(), hr->end()); 5959 ct_bs->verify_not_dirty_region(mr); 5960 } 5961 5962 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5963 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5964 // dirty allocated blocks as they allocate them. The thread that 5965 // retires each region and replaces it with a new one will do a 5966 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5967 // not dirty that area (one less thing to have to do while holding 5968 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5969 // is dirty. 5970 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5971 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5972 if (hr->is_young()) { 5973 ct_bs->verify_g1_young_region(mr); 5974 } else { 5975 ct_bs->verify_dirty_region(mr); 5976 } 5977 } 5978 5979 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5980 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5981 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5982 verify_dirty_region(hr); 5983 } 5984 } 5985 5986 void G1CollectedHeap::verify_dirty_young_regions() { 5987 verify_dirty_young_list(_young_list->first_region()); 5988 } 5989 5990 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5991 HeapWord* tams, HeapWord* end) { 5992 guarantee(tams <= end, 5993 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end)); 5994 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5995 if (result < end) { 5996 gclog_or_tty->cr(); 5997 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT, 5998 bitmap_name, result); 5999 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT, 6000 bitmap_name, tams, end); 6001 return false; 6002 } 6003 return true; 6004 } 6005 6006 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 6007 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 6008 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 6009 6010 HeapWord* bottom = hr->bottom(); 6011 HeapWord* ptams = hr->prev_top_at_mark_start(); 6012 HeapWord* ntams = hr->next_top_at_mark_start(); 6013 HeapWord* end = hr->end(); 6014 6015 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 6016 6017 bool res_n = true; 6018 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 6019 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 6020 // if we happen to be in that state. 6021 if (mark_in_progress() || !_cmThread->in_progress()) { 6022 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 6023 } 6024 if (!res_p || !res_n) { 6025 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT, 6026 HR_FORMAT_PARAMS(hr)); 6027 gclog_or_tty->print_cr("#### Caller: %s", caller); 6028 return false; 6029 } 6030 return true; 6031 } 6032 6033 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 6034 if (!G1VerifyBitmaps) return; 6035 6036 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 6037 } 6038 6039 class G1VerifyBitmapClosure : public HeapRegionClosure { 6040 private: 6041 const char* _caller; 6042 G1CollectedHeap* _g1h; 6043 bool _failures; 6044 6045 public: 6046 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 6047 _caller(caller), _g1h(g1h), _failures(false) { } 6048 6049 bool failures() { return _failures; } 6050 6051 virtual bool doHeapRegion(HeapRegion* hr) { 6052 if (hr->is_continues_humongous()) return false; 6053 6054 bool result = _g1h->verify_bitmaps(_caller, hr); 6055 if (!result) { 6056 _failures = true; 6057 } 6058 return false; 6059 } 6060 }; 6061 6062 void G1CollectedHeap::check_bitmaps(const char* caller) { 6063 if (!G1VerifyBitmaps) return; 6064 6065 G1VerifyBitmapClosure cl(caller, this); 6066 heap_region_iterate(&cl); 6067 guarantee(!cl.failures(), "bitmap verification"); 6068 } 6069 #endif // PRODUCT 6070 6071 void G1CollectedHeap::cleanUpCardTable() { 6072 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6073 double start = os::elapsedTime(); 6074 6075 { 6076 // Iterate over the dirty cards region list. 6077 G1ParCleanupCTTask cleanup_task(ct_bs, this); 6078 6079 if (G1CollectedHeap::use_parallel_gc_threads()) { 6080 set_par_threads(); 6081 workers()->run_task(&cleanup_task); 6082 set_par_threads(0); 6083 } else { 6084 while (_dirty_cards_region_list) { 6085 HeapRegion* r = _dirty_cards_region_list; 6086 cleanup_task.clear_cards(r); 6087 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 6088 if (_dirty_cards_region_list == r) { 6089 // The last region. 6090 _dirty_cards_region_list = NULL; 6091 } 6092 r->set_next_dirty_cards_region(NULL); 6093 } 6094 } 6095 #ifndef PRODUCT 6096 if (G1VerifyCTCleanup || VerifyAfterGC) { 6097 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 6098 heap_region_iterate(&cleanup_verifier); 6099 } 6100 #endif 6101 } 6102 6103 double elapsed = os::elapsedTime() - start; 6104 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 6105 } 6106 6107 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) { 6108 size_t pre_used = 0; 6109 FreeRegionList local_free_list("Local List for CSet Freeing"); 6110 6111 double young_time_ms = 0.0; 6112 double non_young_time_ms = 0.0; 6113 6114 // Since the collection set is a superset of the the young list, 6115 // all we need to do to clear the young list is clear its 6116 // head and length, and unlink any young regions in the code below 6117 _young_list->clear(); 6118 6119 G1CollectorPolicy* policy = g1_policy(); 6120 6121 double start_sec = os::elapsedTime(); 6122 bool non_young = true; 6123 6124 HeapRegion* cur = cs_head; 6125 int age_bound = -1; 6126 size_t rs_lengths = 0; 6127 6128 while (cur != NULL) { 6129 assert(!is_on_master_free_list(cur), "sanity"); 6130 if (non_young) { 6131 if (cur->is_young()) { 6132 double end_sec = os::elapsedTime(); 6133 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6134 non_young_time_ms += elapsed_ms; 6135 6136 start_sec = os::elapsedTime(); 6137 non_young = false; 6138 } 6139 } else { 6140 if (!cur->is_young()) { 6141 double end_sec = os::elapsedTime(); 6142 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6143 young_time_ms += elapsed_ms; 6144 6145 start_sec = os::elapsedTime(); 6146 non_young = true; 6147 } 6148 } 6149 6150 rs_lengths += cur->rem_set()->occupied_locked(); 6151 6152 HeapRegion* next = cur->next_in_collection_set(); 6153 assert(cur->in_collection_set(), "bad CS"); 6154 cur->set_next_in_collection_set(NULL); 6155 cur->set_in_collection_set(false); 6156 6157 if (cur->is_young()) { 6158 int index = cur->young_index_in_cset(); 6159 assert(index != -1, "invariant"); 6160 assert((uint) index < policy->young_cset_region_length(), "invariant"); 6161 size_t words_survived = _surviving_young_words[index]; 6162 cur->record_surv_words_in_group(words_survived); 6163 6164 // At this point the we have 'popped' cur from the collection set 6165 // (linked via next_in_collection_set()) but it is still in the 6166 // young list (linked via next_young_region()). Clear the 6167 // _next_young_region field. 6168 cur->set_next_young_region(NULL); 6169 } else { 6170 int index = cur->young_index_in_cset(); 6171 assert(index == -1, "invariant"); 6172 } 6173 6174 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 6175 (!cur->is_young() && cur->young_index_in_cset() == -1), 6176 "invariant" ); 6177 6178 if (!cur->evacuation_failed()) { 6179 MemRegion used_mr = cur->used_region(); 6180 6181 // And the region is empty. 6182 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6183 pre_used += cur->used(); 6184 free_region(cur, &local_free_list, false /* par */, true /* locked */); 6185 } else { 6186 cur->uninstall_surv_rate_group(); 6187 if (cur->is_young()) { 6188 cur->set_young_index_in_cset(-1); 6189 } 6190 cur->set_evacuation_failed(false); 6191 // The region is now considered to be old. 6192 cur->set_old(); 6193 _old_set.add(cur); 6194 evacuation_info.increment_collectionset_used_after(cur->used()); 6195 } 6196 cur = next; 6197 } 6198 6199 evacuation_info.set_regions_freed(local_free_list.length()); 6200 policy->record_max_rs_lengths(rs_lengths); 6201 policy->cset_regions_freed(); 6202 6203 double end_sec = os::elapsedTime(); 6204 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6205 6206 if (non_young) { 6207 non_young_time_ms += elapsed_ms; 6208 } else { 6209 young_time_ms += elapsed_ms; 6210 } 6211 6212 prepend_to_freelist(&local_free_list); 6213 decrement_summary_bytes(pre_used); 6214 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6215 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6216 } 6217 6218 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 6219 private: 6220 FreeRegionList* _free_region_list; 6221 HeapRegionSet* _proxy_set; 6222 HeapRegionSetCount _humongous_regions_removed; 6223 size_t _freed_bytes; 6224 public: 6225 6226 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 6227 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 6228 } 6229 6230 virtual bool doHeapRegion(HeapRegion* r) { 6231 if (!r->is_starts_humongous()) { 6232 return false; 6233 } 6234 6235 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 6236 6237 oop obj = (oop)r->bottom(); 6238 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 6239 6240 // The following checks whether the humongous object is live are sufficient. 6241 // The main additional check (in addition to having a reference from the roots 6242 // or the young gen) is whether the humongous object has a remembered set entry. 6243 // 6244 // A humongous object cannot be live if there is no remembered set for it 6245 // because: 6246 // - there can be no references from within humongous starts regions referencing 6247 // the object because we never allocate other objects into them. 6248 // (I.e. there are no intra-region references that may be missed by the 6249 // remembered set) 6250 // - as soon there is a remembered set entry to the humongous starts region 6251 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 6252 // until the end of a concurrent mark. 6253 // 6254 // It is not required to check whether the object has been found dead by marking 6255 // or not, in fact it would prevent reclamation within a concurrent cycle, as 6256 // all objects allocated during that time are considered live. 6257 // SATB marking is even more conservative than the remembered set. 6258 // So if at this point in the collection there is no remembered set entry, 6259 // nobody has a reference to it. 6260 // At the start of collection we flush all refinement logs, and remembered sets 6261 // are completely up-to-date wrt to references to the humongous object. 6262 // 6263 // Other implementation considerations: 6264 // - never consider object arrays: while they are a valid target, they have not 6265 // been observed to be used as temporary objects. 6266 // - they would also pose considerable effort for cleaning up the the remembered 6267 // sets. 6268 // While this cleanup is not strictly necessary to be done (or done instantly), 6269 // given that their occurrence is very low, this saves us this additional 6270 // complexity. 6271 uint region_idx = r->hrm_index(); 6272 if (g1h->humongous_is_live(region_idx) || 6273 g1h->humongous_region_is_always_live(region_idx)) { 6274 6275 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) { 6276 gclog_or_tty->print_cr("Live humongous %d region %d with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d", 6277 r->is_humongous(), 6278 region_idx, 6279 r->rem_set()->occupied(), 6280 r->rem_set()->strong_code_roots_list_length(), 6281 next_bitmap->isMarked(r->bottom()), 6282 g1h->humongous_is_live(region_idx), 6283 obj->is_objArray() 6284 ); 6285 } 6286 6287 return false; 6288 } 6289 6290 guarantee(!obj->is_objArray(), 6291 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.", 6292 r->bottom())); 6293 6294 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) { 6295 gclog_or_tty->print_cr("Reclaim humongous region %d start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d", 6296 r->is_humongous(), 6297 r->bottom(), 6298 region_idx, 6299 r->region_num(), 6300 r->rem_set()->occupied(), 6301 r->rem_set()->strong_code_roots_list_length(), 6302 next_bitmap->isMarked(r->bottom()), 6303 g1h->humongous_is_live(region_idx), 6304 obj->is_objArray() 6305 ); 6306 } 6307 // Need to clear mark bit of the humongous object if already set. 6308 if (next_bitmap->isMarked(r->bottom())) { 6309 next_bitmap->clear(r->bottom()); 6310 } 6311 _freed_bytes += r->used(); 6312 r->set_containing_set(NULL); 6313 _humongous_regions_removed.increment(1u, r->capacity()); 6314 g1h->free_humongous_region(r, _free_region_list, false); 6315 6316 return false; 6317 } 6318 6319 HeapRegionSetCount& humongous_free_count() { 6320 return _humongous_regions_removed; 6321 } 6322 6323 size_t bytes_freed() const { 6324 return _freed_bytes; 6325 } 6326 6327 size_t humongous_reclaimed() const { 6328 return _humongous_regions_removed.length(); 6329 } 6330 }; 6331 6332 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 6333 assert_at_safepoint(true); 6334 6335 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) { 6336 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 6337 return; 6338 } 6339 6340 double start_time = os::elapsedTime(); 6341 6342 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 6343 6344 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 6345 heap_region_iterate(&cl); 6346 6347 HeapRegionSetCount empty_set; 6348 remove_from_old_sets(empty_set, cl.humongous_free_count()); 6349 6350 G1HRPrinter* hr_printer = _g1h->hr_printer(); 6351 if (hr_printer->is_active()) { 6352 FreeRegionListIterator iter(&local_cleanup_list); 6353 while (iter.more_available()) { 6354 HeapRegion* hr = iter.get_next(); 6355 hr_printer->cleanup(hr); 6356 } 6357 } 6358 6359 prepend_to_freelist(&local_cleanup_list); 6360 decrement_summary_bytes(cl.bytes_freed()); 6361 6362 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 6363 cl.humongous_reclaimed()); 6364 } 6365 6366 // This routine is similar to the above but does not record 6367 // any policy statistics or update free lists; we are abandoning 6368 // the current incremental collection set in preparation of a 6369 // full collection. After the full GC we will start to build up 6370 // the incremental collection set again. 6371 // This is only called when we're doing a full collection 6372 // and is immediately followed by the tearing down of the young list. 6373 6374 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6375 HeapRegion* cur = cs_head; 6376 6377 while (cur != NULL) { 6378 HeapRegion* next = cur->next_in_collection_set(); 6379 assert(cur->in_collection_set(), "bad CS"); 6380 cur->set_next_in_collection_set(NULL); 6381 cur->set_in_collection_set(false); 6382 cur->set_young_index_in_cset(-1); 6383 cur = next; 6384 } 6385 } 6386 6387 void G1CollectedHeap::set_free_regions_coming() { 6388 if (G1ConcRegionFreeingVerbose) { 6389 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6390 "setting free regions coming"); 6391 } 6392 6393 assert(!free_regions_coming(), "pre-condition"); 6394 _free_regions_coming = true; 6395 } 6396 6397 void G1CollectedHeap::reset_free_regions_coming() { 6398 assert(free_regions_coming(), "pre-condition"); 6399 6400 { 6401 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6402 _free_regions_coming = false; 6403 SecondaryFreeList_lock->notify_all(); 6404 } 6405 6406 if (G1ConcRegionFreeingVerbose) { 6407 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6408 "reset free regions coming"); 6409 } 6410 } 6411 6412 void G1CollectedHeap::wait_while_free_regions_coming() { 6413 // Most of the time we won't have to wait, so let's do a quick test 6414 // first before we take the lock. 6415 if (!free_regions_coming()) { 6416 return; 6417 } 6418 6419 if (G1ConcRegionFreeingVerbose) { 6420 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6421 "waiting for free regions"); 6422 } 6423 6424 { 6425 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6426 while (free_regions_coming()) { 6427 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6428 } 6429 } 6430 6431 if (G1ConcRegionFreeingVerbose) { 6432 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6433 "done waiting for free regions"); 6434 } 6435 } 6436 6437 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6438 assert(heap_lock_held_for_gc(), 6439 "the heap lock should already be held by or for this thread"); 6440 _young_list->push_region(hr); 6441 } 6442 6443 class NoYoungRegionsClosure: public HeapRegionClosure { 6444 private: 6445 bool _success; 6446 public: 6447 NoYoungRegionsClosure() : _success(true) { } 6448 bool doHeapRegion(HeapRegion* r) { 6449 if (r->is_young()) { 6450 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6451 r->bottom(), r->end()); 6452 _success = false; 6453 } 6454 return false; 6455 } 6456 bool success() { return _success; } 6457 }; 6458 6459 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6460 bool ret = _young_list->check_list_empty(check_sample); 6461 6462 if (check_heap) { 6463 NoYoungRegionsClosure closure; 6464 heap_region_iterate(&closure); 6465 ret = ret && closure.success(); 6466 } 6467 6468 return ret; 6469 } 6470 6471 class TearDownRegionSetsClosure : public HeapRegionClosure { 6472 private: 6473 HeapRegionSet *_old_set; 6474 6475 public: 6476 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 6477 6478 bool doHeapRegion(HeapRegion* r) { 6479 if (r->is_old()) { 6480 _old_set->remove(r); 6481 } else { 6482 // We ignore free regions, we'll empty the free list afterwards. 6483 // We ignore young regions, we'll empty the young list afterwards. 6484 // We ignore humongous regions, we're not tearing down the 6485 // humongous regions set. 6486 assert(r->is_free() || r->is_young() || r->is_humongous(), 6487 "it cannot be another type"); 6488 } 6489 return false; 6490 } 6491 6492 ~TearDownRegionSetsClosure() { 6493 assert(_old_set->is_empty(), "post-condition"); 6494 } 6495 }; 6496 6497 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6498 assert_at_safepoint(true /* should_be_vm_thread */); 6499 6500 if (!free_list_only) { 6501 TearDownRegionSetsClosure cl(&_old_set); 6502 heap_region_iterate(&cl); 6503 6504 // Note that emptying the _young_list is postponed and instead done as 6505 // the first step when rebuilding the regions sets again. The reason for 6506 // this is that during a full GC string deduplication needs to know if 6507 // a collected region was young or old when the full GC was initiated. 6508 } 6509 _hrm.remove_all_free_regions(); 6510 } 6511 6512 class RebuildRegionSetsClosure : public HeapRegionClosure { 6513 private: 6514 bool _free_list_only; 6515 HeapRegionSet* _old_set; 6516 HeapRegionManager* _hrm; 6517 size_t _total_used; 6518 6519 public: 6520 RebuildRegionSetsClosure(bool free_list_only, 6521 HeapRegionSet* old_set, HeapRegionManager* hrm) : 6522 _free_list_only(free_list_only), 6523 _old_set(old_set), _hrm(hrm), _total_used(0) { 6524 assert(_hrm->num_free_regions() == 0, "pre-condition"); 6525 if (!free_list_only) { 6526 assert(_old_set->is_empty(), "pre-condition"); 6527 } 6528 } 6529 6530 bool doHeapRegion(HeapRegion* r) { 6531 if (r->is_continues_humongous()) { 6532 return false; 6533 } 6534 6535 if (r->is_empty()) { 6536 // Add free regions to the free list 6537 r->set_free(); 6538 r->set_allocation_context(AllocationContext::system()); 6539 _hrm->insert_into_free_list(r); 6540 } else if (!_free_list_only) { 6541 assert(!r->is_young(), "we should not come across young regions"); 6542 6543 if (r->is_humongous()) { 6544 // We ignore humongous regions, we left the humongous set unchanged 6545 } else { 6546 // Objects that were compacted would have ended up on regions 6547 // that were previously old or free. 6548 assert(r->is_free() || r->is_old(), "invariant"); 6549 // We now consider them old, so register as such. 6550 r->set_old(); 6551 _old_set->add(r); 6552 } 6553 _total_used += r->used(); 6554 } 6555 6556 return false; 6557 } 6558 6559 size_t total_used() { 6560 return _total_used; 6561 } 6562 }; 6563 6564 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6565 assert_at_safepoint(true /* should_be_vm_thread */); 6566 6567 if (!free_list_only) { 6568 _young_list->empty_list(); 6569 } 6570 6571 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6572 heap_region_iterate(&cl); 6573 6574 if (!free_list_only) { 6575 _allocator->set_used(cl.total_used()); 6576 } 6577 assert(_allocator->used_unlocked() == recalculate_used(), 6578 err_msg("inconsistent _allocator->used_unlocked(), " 6579 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6580 _allocator->used_unlocked(), recalculate_used())); 6581 } 6582 6583 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6584 _refine_cte_cl->set_concurrent(concurrent); 6585 } 6586 6587 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6588 HeapRegion* hr = heap_region_containing(p); 6589 return hr->is_in(p); 6590 } 6591 6592 // Methods for the mutator alloc region 6593 6594 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6595 bool force) { 6596 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6597 assert(!force || g1_policy()->can_expand_young_list(), 6598 "if force is true we should be able to expand the young list"); 6599 bool young_list_full = g1_policy()->is_young_list_full(); 6600 if (force || !young_list_full) { 6601 HeapRegion* new_alloc_region = new_region(word_size, 6602 false /* is_old */, 6603 false /* do_expand */); 6604 if (new_alloc_region != NULL) { 6605 set_region_short_lived_locked(new_alloc_region); 6606 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6607 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6608 return new_alloc_region; 6609 } 6610 } 6611 return NULL; 6612 } 6613 6614 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6615 size_t allocated_bytes) { 6616 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6617 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6618 6619 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6620 _allocator->increase_used(allocated_bytes); 6621 _hr_printer.retire(alloc_region); 6622 // We update the eden sizes here, when the region is retired, 6623 // instead of when it's allocated, since this is the point that its 6624 // used space has been recored in _summary_bytes_used. 6625 g1mm()->update_eden_size(); 6626 } 6627 6628 void G1CollectedHeap::set_par_threads() { 6629 // Don't change the number of workers. Use the value previously set 6630 // in the workgroup. 6631 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6632 uint n_workers = workers()->active_workers(); 6633 assert(UseDynamicNumberOfGCThreads || 6634 n_workers == workers()->total_workers(), 6635 "Otherwise should be using the total number of workers"); 6636 if (n_workers == 0) { 6637 assert(false, "Should have been set in prior evacuation pause."); 6638 n_workers = ParallelGCThreads; 6639 workers()->set_active_workers(n_workers); 6640 } 6641 set_par_threads(n_workers); 6642 } 6643 6644 // Methods for the GC alloc regions 6645 6646 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6647 uint count, 6648 GCAllocPurpose ap) { 6649 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6650 6651 if (count < g1_policy()->max_regions(ap)) { 6652 bool survivor = (ap == GCAllocForSurvived); 6653 HeapRegion* new_alloc_region = new_region(word_size, 6654 !survivor, 6655 true /* do_expand */); 6656 if (new_alloc_region != NULL) { 6657 // We really only need to do this for old regions given that we 6658 // should never scan survivors. But it doesn't hurt to do it 6659 // for survivors too. 6660 new_alloc_region->record_top_and_timestamp(); 6661 if (survivor) { 6662 new_alloc_region->set_survivor(); 6663 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6664 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6665 } else { 6666 new_alloc_region->set_old(); 6667 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6668 check_bitmaps("Old Region Allocation", new_alloc_region); 6669 } 6670 bool during_im = g1_policy()->during_initial_mark_pause(); 6671 new_alloc_region->note_start_of_copying(during_im); 6672 return new_alloc_region; 6673 } else { 6674 g1_policy()->note_alloc_region_limit_reached(ap); 6675 } 6676 } 6677 return NULL; 6678 } 6679 6680 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6681 size_t allocated_bytes, 6682 GCAllocPurpose ap) { 6683 bool during_im = g1_policy()->during_initial_mark_pause(); 6684 alloc_region->note_end_of_copying(during_im); 6685 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6686 if (ap == GCAllocForSurvived) { 6687 young_list()->add_survivor_region(alloc_region); 6688 } else { 6689 _old_set.add(alloc_region); 6690 } 6691 _hr_printer.retire(alloc_region); 6692 } 6693 6694 // Heap region set verification 6695 6696 class VerifyRegionListsClosure : public HeapRegionClosure { 6697 private: 6698 HeapRegionSet* _old_set; 6699 HeapRegionSet* _humongous_set; 6700 HeapRegionManager* _hrm; 6701 6702 public: 6703 HeapRegionSetCount _old_count; 6704 HeapRegionSetCount _humongous_count; 6705 HeapRegionSetCount _free_count; 6706 6707 VerifyRegionListsClosure(HeapRegionSet* old_set, 6708 HeapRegionSet* humongous_set, 6709 HeapRegionManager* hrm) : 6710 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6711 _old_count(), _humongous_count(), _free_count(){ } 6712 6713 bool doHeapRegion(HeapRegion* hr) { 6714 if (hr->is_continues_humongous()) { 6715 return false; 6716 } 6717 6718 if (hr->is_young()) { 6719 // TODO 6720 } else if (hr->is_starts_humongous()) { 6721 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index())); 6722 _humongous_count.increment(1u, hr->capacity()); 6723 } else if (hr->is_empty()) { 6724 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index())); 6725 _free_count.increment(1u, hr->capacity()); 6726 } else if (hr->is_old()) { 6727 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index())); 6728 _old_count.increment(1u, hr->capacity()); 6729 } else { 6730 ShouldNotReachHere(); 6731 } 6732 return false; 6733 } 6734 6735 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6736 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length())); 6737 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6738 old_set->total_capacity_bytes(), _old_count.capacity())); 6739 6740 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length())); 6741 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6742 humongous_set->total_capacity_bytes(), _humongous_count.capacity())); 6743 6744 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())); 6745 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6746 free_list->total_capacity_bytes(), _free_count.capacity())); 6747 } 6748 }; 6749 6750 void G1CollectedHeap::verify_region_sets() { 6751 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6752 6753 // First, check the explicit lists. 6754 _hrm.verify(); 6755 { 6756 // Given that a concurrent operation might be adding regions to 6757 // the secondary free list we have to take the lock before 6758 // verifying it. 6759 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6760 _secondary_free_list.verify_list(); 6761 } 6762 6763 // If a concurrent region freeing operation is in progress it will 6764 // be difficult to correctly attributed any free regions we come 6765 // across to the correct free list given that they might belong to 6766 // one of several (free_list, secondary_free_list, any local lists, 6767 // etc.). So, if that's the case we will skip the rest of the 6768 // verification operation. Alternatively, waiting for the concurrent 6769 // operation to complete will have a non-trivial effect on the GC's 6770 // operation (no concurrent operation will last longer than the 6771 // interval between two calls to verification) and it might hide 6772 // any issues that we would like to catch during testing. 6773 if (free_regions_coming()) { 6774 return; 6775 } 6776 6777 // Make sure we append the secondary_free_list on the free_list so 6778 // that all free regions we will come across can be safely 6779 // attributed to the free_list. 6780 append_secondary_free_list_if_not_empty_with_lock(); 6781 6782 // Finally, make sure that the region accounting in the lists is 6783 // consistent with what we see in the heap. 6784 6785 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6786 heap_region_iterate(&cl); 6787 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6788 } 6789 6790 // Optimized nmethod scanning 6791 6792 class RegisterNMethodOopClosure: public OopClosure { 6793 G1CollectedHeap* _g1h; 6794 nmethod* _nm; 6795 6796 template <class T> void do_oop_work(T* p) { 6797 T heap_oop = oopDesc::load_heap_oop(p); 6798 if (!oopDesc::is_null(heap_oop)) { 6799 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6800 HeapRegion* hr = _g1h->heap_region_containing(obj); 6801 assert(!hr->is_continues_humongous(), 6802 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6803 " starting at "HR_FORMAT, 6804 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6805 6806 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6807 hr->add_strong_code_root_locked(_nm); 6808 } 6809 } 6810 6811 public: 6812 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6813 _g1h(g1h), _nm(nm) {} 6814 6815 void do_oop(oop* p) { do_oop_work(p); } 6816 void do_oop(narrowOop* p) { do_oop_work(p); } 6817 }; 6818 6819 class UnregisterNMethodOopClosure: public OopClosure { 6820 G1CollectedHeap* _g1h; 6821 nmethod* _nm; 6822 6823 template <class T> void do_oop_work(T* p) { 6824 T heap_oop = oopDesc::load_heap_oop(p); 6825 if (!oopDesc::is_null(heap_oop)) { 6826 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6827 HeapRegion* hr = _g1h->heap_region_containing(obj); 6828 assert(!hr->is_continues_humongous(), 6829 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6830 " starting at "HR_FORMAT, 6831 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6832 6833 hr->remove_strong_code_root(_nm); 6834 } 6835 } 6836 6837 public: 6838 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6839 _g1h(g1h), _nm(nm) {} 6840 6841 void do_oop(oop* p) { do_oop_work(p); } 6842 void do_oop(narrowOop* p) { do_oop_work(p); } 6843 }; 6844 6845 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6846 CollectedHeap::register_nmethod(nm); 6847 6848 guarantee(nm != NULL, "sanity"); 6849 RegisterNMethodOopClosure reg_cl(this, nm); 6850 nm->oops_do(®_cl); 6851 } 6852 6853 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6854 CollectedHeap::unregister_nmethod(nm); 6855 6856 guarantee(nm != NULL, "sanity"); 6857 UnregisterNMethodOopClosure reg_cl(this, nm); 6858 nm->oops_do(®_cl, true); 6859 } 6860 6861 void G1CollectedHeap::purge_code_root_memory() { 6862 double purge_start = os::elapsedTime(); 6863 G1CodeRootSet::purge(); 6864 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6865 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6866 } 6867 6868 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6869 G1CollectedHeap* _g1h; 6870 6871 public: 6872 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6873 _g1h(g1h) {} 6874 6875 void do_code_blob(CodeBlob* cb) { 6876 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6877 if (nm == NULL) { 6878 return; 6879 } 6880 6881 if (ScavengeRootsInCode) { 6882 _g1h->register_nmethod(nm); 6883 } 6884 } 6885 }; 6886 6887 void G1CollectedHeap::rebuild_strong_code_roots() { 6888 RebuildStrongCodeRootClosure blob_cl(this); 6889 CodeCache::blobs_do(&blob_cl); 6890 }