1 /* 2 * Copyright (c) 2002, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/stringTable.hpp" 27 #include "code/codeCache.hpp" 28 #include "gc/parallel/cardTableExtension.hpp" 29 #include "gc/parallel/gcTaskManager.hpp" 30 #include "gc/parallel/parallelScavengeHeap.hpp" 31 #include "gc/parallel/psAdaptiveSizePolicy.hpp" 32 #include "gc/parallel/psMarkSweep.hpp" 33 #include "gc/parallel/psParallelCompact.hpp" 34 #include "gc/parallel/psScavenge.inline.hpp" 35 #include "gc/parallel/psTasks.hpp" 36 #include "gc/shared/collectorPolicy.hpp" 37 #include "gc/shared/gcCause.hpp" 38 #include "gc/shared/gcHeapSummary.hpp" 39 #include "gc/shared/gcLocker.inline.hpp" 40 #include "gc/shared/gcTimer.hpp" 41 #include "gc/shared/gcTrace.hpp" 42 #include "gc/shared/gcTraceTime.hpp" 43 #include "gc/shared/isGCActiveMark.hpp" 44 #include "gc/shared/referencePolicy.hpp" 45 #include "gc/shared/referenceProcessor.hpp" 46 #include "gc/shared/spaceDecorator.hpp" 47 #include "memory/resourceArea.hpp" 48 #include "oops/oop.inline.hpp" 49 #include "runtime/biasedLocking.hpp" 50 #include "runtime/fprofiler.hpp" 51 #include "runtime/handles.inline.hpp" 52 #include "runtime/threadCritical.hpp" 53 #include "runtime/vmThread.hpp" 54 #include "runtime/vm_operations.hpp" 55 #include "services/memoryService.hpp" 56 #include "utilities/stack.inline.hpp" 57 58 HeapWord* PSScavenge::_to_space_top_before_gc = NULL; 59 int PSScavenge::_consecutive_skipped_scavenges = 0; 60 ReferenceProcessor* PSScavenge::_ref_processor = NULL; 61 CardTableExtension* PSScavenge::_card_table = NULL; 62 bool PSScavenge::_survivor_overflow = false; 63 uint PSScavenge::_tenuring_threshold = 0; 64 HeapWord* PSScavenge::_young_generation_boundary = NULL; 65 uintptr_t PSScavenge::_young_generation_boundary_compressed = 0; 66 elapsedTimer PSScavenge::_accumulated_time; 67 STWGCTimer PSScavenge::_gc_timer; 68 ParallelScavengeTracer PSScavenge::_gc_tracer; 69 Stack<markOop, mtGC> PSScavenge::_preserved_mark_stack; 70 Stack<oop, mtGC> PSScavenge::_preserved_oop_stack; 71 CollectorCounters* PSScavenge::_counters = NULL; 72 73 // Define before use 74 class PSIsAliveClosure: public BoolObjectClosure { 75 public: 76 bool do_object_b(oop p) { 77 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded(); 78 } 79 }; 80 81 PSIsAliveClosure PSScavenge::_is_alive_closure; 82 83 class PSKeepAliveClosure: public OopClosure { 84 protected: 85 MutableSpace* _to_space; 86 PSPromotionManager* _promotion_manager; 87 88 public: 89 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) { 90 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 91 _to_space = heap->young_gen()->to_space(); 92 93 assert(_promotion_manager != NULL, "Sanity"); 94 } 95 96 template <class T> void do_oop_work(T* p) { 97 assert (!oopDesc::is_null(*p), "expected non-null ref"); 98 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(), 99 "expected an oop while scanning weak refs"); 100 101 // Weak refs may be visited more than once. 102 if (PSScavenge::should_scavenge(p, _to_space)) { 103 _promotion_manager->copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(p); 104 } 105 } 106 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); } 107 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); } 108 }; 109 110 class PSEvacuateFollowersClosure: public VoidClosure { 111 private: 112 PSPromotionManager* _promotion_manager; 113 public: 114 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {} 115 116 virtual void do_void() { 117 assert(_promotion_manager != NULL, "Sanity"); 118 _promotion_manager->drain_stacks(true); 119 guarantee(_promotion_manager->stacks_empty(), 120 "stacks should be empty at this point"); 121 } 122 }; 123 124 class PSPromotionFailedClosure : public ObjectClosure { 125 virtual void do_object(oop obj) { 126 if (obj->is_forwarded()) { 127 obj->init_mark(); 128 } 129 } 130 }; 131 132 class PSRefProcTaskProxy: public GCTask { 133 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 134 ProcessTask & _rp_task; 135 uint _work_id; 136 public: 137 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id) 138 : _rp_task(rp_task), 139 _work_id(work_id) 140 { } 141 142 private: 143 virtual char* name() { return (char *)"Process referents by policy in parallel"; } 144 virtual void do_it(GCTaskManager* manager, uint which); 145 }; 146 147 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which) 148 { 149 PSPromotionManager* promotion_manager = 150 PSPromotionManager::gc_thread_promotion_manager(which); 151 assert(promotion_manager != NULL, "sanity check"); 152 PSKeepAliveClosure keep_alive(promotion_manager); 153 PSEvacuateFollowersClosure evac_followers(promotion_manager); 154 PSIsAliveClosure is_alive; 155 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers); 156 } 157 158 class PSRefEnqueueTaskProxy: public GCTask { 159 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 160 EnqueueTask& _enq_task; 161 uint _work_id; 162 163 public: 164 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id) 165 : _enq_task(enq_task), 166 _work_id(work_id) 167 { } 168 169 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; } 170 virtual void do_it(GCTaskManager* manager, uint which) 171 { 172 _enq_task.work(_work_id); 173 } 174 }; 175 176 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 177 virtual void execute(ProcessTask& task); 178 virtual void execute(EnqueueTask& task); 179 }; 180 181 void PSRefProcTaskExecutor::execute(ProcessTask& task) 182 { 183 GCTaskQueue* q = GCTaskQueue::create(); 184 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager(); 185 for(uint i=0; i < manager->active_workers(); i++) { 186 q->enqueue(new PSRefProcTaskProxy(task, i)); 187 } 188 ParallelTaskTerminator terminator(manager->active_workers(), 189 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth()); 190 if (task.marks_oops_alive() && manager->active_workers() > 1) { 191 for (uint j = 0; j < manager->active_workers(); j++) { 192 q->enqueue(new StealTask(&terminator)); 193 } 194 } 195 manager->execute_and_wait(q); 196 } 197 198 199 void PSRefProcTaskExecutor::execute(EnqueueTask& task) 200 { 201 GCTaskQueue* q = GCTaskQueue::create(); 202 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager(); 203 for(uint i=0; i < manager->active_workers(); i++) { 204 q->enqueue(new PSRefEnqueueTaskProxy(task, i)); 205 } 206 manager->execute_and_wait(q); 207 } 208 209 // This method contains all heap specific policy for invoking scavenge. 210 // PSScavenge::invoke_no_policy() will do nothing but attempt to 211 // scavenge. It will not clean up after failed promotions, bail out if 212 // we've exceeded policy time limits, or any other special behavior. 213 // All such policy should be placed here. 214 // 215 // Note that this method should only be called from the vm_thread while 216 // at a safepoint! 217 bool PSScavenge::invoke() { 218 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 219 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 220 assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant"); 221 222 ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap(); 223 PSAdaptiveSizePolicy* policy = heap->size_policy(); 224 IsGCActiveMark mark; 225 226 const bool scavenge_done = PSScavenge::invoke_no_policy(); 227 const bool need_full_gc = !scavenge_done || 228 policy->should_full_GC(heap->old_gen()->free_in_bytes()); 229 bool full_gc_done = false; 230 231 if (UsePerfData) { 232 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters(); 233 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped; 234 counters->update_full_follows_scavenge(ffs_val); 235 } 236 237 if (need_full_gc) { 238 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy); 239 CollectorPolicy* cp = heap->collector_policy(); 240 const bool clear_all_softrefs = cp->should_clear_all_soft_refs(); 241 242 if (UseParallelOldGC) { 243 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs); 244 } else { 245 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs); 246 } 247 } 248 249 return full_gc_done; 250 } 251 252 // This method contains no policy. You should probably 253 // be calling invoke() instead. 254 bool PSScavenge::invoke_no_policy() { 255 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); 256 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); 257 258 assert(_preserved_mark_stack.is_empty(), "should be empty"); 259 assert(_preserved_oop_stack.is_empty(), "should be empty"); 260 261 _gc_timer.register_gc_start(); 262 263 TimeStamp scavenge_entry; 264 TimeStamp scavenge_midpoint; 265 TimeStamp scavenge_exit; 266 267 scavenge_entry.update(); 268 269 if (GC_locker::check_active_before_gc()) { 270 return false; 271 } 272 273 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 274 GCCause::Cause gc_cause = heap->gc_cause(); 275 276 // Check for potential problems. 277 if (!should_attempt_scavenge()) { 278 return false; 279 } 280 281 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start()); 282 283 bool promotion_failure_occurred = false; 284 285 PSYoungGen* young_gen = heap->young_gen(); 286 PSOldGen* old_gen = heap->old_gen(); 287 PSAdaptiveSizePolicy* size_policy = heap->size_policy(); 288 289 heap->increment_total_collections(); 290 291 AdaptiveSizePolicyOutput(size_policy, heap->total_collections()); 292 293 if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) { 294 // Gather the feedback data for eden occupancy. 295 young_gen->eden_space()->accumulate_statistics(); 296 } 297 298 if (ZapUnusedHeapArea) { 299 // Save information needed to minimize mangling 300 heap->record_gen_tops_before_GC(); 301 } 302 303 heap->print_heap_before_gc(); 304 heap->trace_heap_before_gc(&_gc_tracer); 305 306 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity"); 307 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity"); 308 309 size_t prev_used = heap->used(); 310 311 // Fill in TLABs 312 heap->accumulate_statistics_all_tlabs(); 313 heap->ensure_parsability(true); // retire TLABs 314 315 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) { 316 HandleMark hm; // Discard invalid handles created during verification 317 Universe::verify(" VerifyBeforeGC:"); 318 } 319 320 { 321 ResourceMark rm; 322 HandleMark hm; 323 324 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 325 GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer.gc_id()); 326 TraceCollectorStats tcs(counters()); 327 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause); 328 329 if (TraceYoungGenTime) accumulated_time()->start(); 330 331 // Let the size policy know we're starting 332 size_policy->minor_collection_begin(); 333 334 // Verify the object start arrays. 335 if (VerifyObjectStartArray && 336 VerifyBeforeGC) { 337 old_gen->verify_object_start_array(); 338 } 339 340 // Verify no unmarked old->young roots 341 if (VerifyRememberedSets) { 342 CardTableExtension::verify_all_young_refs_imprecise(); 343 } 344 345 if (!ScavengeWithObjectsInToSpace) { 346 assert(young_gen->to_space()->is_empty(), 347 "Attempt to scavenge with live objects in to_space"); 348 young_gen->to_space()->clear(SpaceDecorator::Mangle); 349 } else if (ZapUnusedHeapArea) { 350 young_gen->to_space()->mangle_unused_area(); 351 } 352 save_to_space_top_before_gc(); 353 354 COMPILER2_PRESENT(DerivedPointerTable::clear()); 355 356 reference_processor()->enable_discovery(); 357 reference_processor()->setup_policy(false); 358 359 // We track how much was promoted to the next generation for 360 // the AdaptiveSizePolicy. 361 size_t old_gen_used_before = old_gen->used_in_bytes(); 362 363 // For PrintGCDetails 364 size_t young_gen_used_before = young_gen->used_in_bytes(); 365 366 // Reset our survivor overflow. 367 set_survivor_overflow(false); 368 369 // We need to save the old top values before 370 // creating the promotion_manager. We pass the top 371 // values to the card_table, to prevent it from 372 // straying into the promotion labs. 373 HeapWord* old_top = old_gen->object_space()->top(); 374 375 // Release all previously held resources 376 gc_task_manager()->release_all_resources(); 377 378 // Set the number of GC threads to be used in this collection 379 gc_task_manager()->set_active_gang(); 380 gc_task_manager()->task_idle_workers(); 381 // Get the active number of workers here and use that value 382 // throughout the methods. 383 uint active_workers = gc_task_manager()->active_workers(); 384 385 PSPromotionManager::pre_scavenge(); 386 387 // We'll use the promotion manager again later. 388 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager(); 389 { 390 GCTraceTime tm("Scavenge", false, false, &_gc_timer, _gc_tracer.gc_id()); 391 ParallelScavengeHeap::ParStrongRootsScope psrs; 392 393 GCTaskQueue* q = GCTaskQueue::create(); 394 395 if (!old_gen->object_space()->is_empty()) { 396 // There are only old-to-young pointers if there are objects 397 // in the old gen. 398 uint stripe_total = active_workers; 399 for(uint i=0; i < stripe_total; i++) { 400 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total)); 401 } 402 } 403 404 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe)); 405 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles)); 406 // We scan the thread roots in parallel 407 Threads::create_thread_roots_tasks(q); 408 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer)); 409 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler)); 410 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management)); 411 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary)); 412 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data)); 413 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti)); 414 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache)); 415 416 ParallelTaskTerminator terminator( 417 active_workers, 418 (TaskQueueSetSuper*) promotion_manager->stack_array_depth()); 419 if (active_workers > 1) { 420 for (uint j = 0; j < active_workers; j++) { 421 q->enqueue(new StealTask(&terminator)); 422 } 423 } 424 425 gc_task_manager()->execute_and_wait(q); 426 } 427 428 scavenge_midpoint.update(); 429 430 // Process reference objects discovered during scavenge 431 { 432 GCTraceTime tm("References", false, false, &_gc_timer, _gc_tracer.gc_id()); 433 434 reference_processor()->setup_policy(false); // not always_clear 435 reference_processor()->set_active_mt_degree(active_workers); 436 PSKeepAliveClosure keep_alive(promotion_manager); 437 PSEvacuateFollowersClosure evac_followers(promotion_manager); 438 ReferenceProcessorStats stats; 439 if (reference_processor()->processing_is_mt()) { 440 PSRefProcTaskExecutor task_executor; 441 stats = reference_processor()->process_discovered_references( 442 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor, 443 &_gc_timer, _gc_tracer.gc_id()); 444 } else { 445 stats = reference_processor()->process_discovered_references( 446 &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer, _gc_tracer.gc_id()); 447 } 448 449 _gc_tracer.report_gc_reference_stats(stats); 450 451 // Enqueue reference objects discovered during scavenge. 452 if (reference_processor()->processing_is_mt()) { 453 PSRefProcTaskExecutor task_executor; 454 reference_processor()->enqueue_discovered_references(&task_executor); 455 } else { 456 reference_processor()->enqueue_discovered_references(NULL); 457 } 458 } 459 460 { 461 GCTraceTime tm("StringTable", false, false, &_gc_timer, _gc_tracer.gc_id()); 462 // Unlink any dead interned Strings and process the remaining live ones. 463 PSScavengeRootsClosure root_closure(promotion_manager); 464 StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure); 465 } 466 467 // Finally, flush the promotion_manager's labs, and deallocate its stacks. 468 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer); 469 if (promotion_failure_occurred) { 470 clean_up_failed_promotion(); 471 if (PrintGC) { 472 gclog_or_tty->print("--"); 473 } 474 } 475 476 // Let the size policy know we're done. Note that we count promotion 477 // failure cleanup time as part of the collection (otherwise, we're 478 // implicitly saying it's mutator time). 479 size_policy->minor_collection_end(gc_cause); 480 481 if (!promotion_failure_occurred) { 482 // Swap the survivor spaces. 483 young_gen->eden_space()->clear(SpaceDecorator::Mangle); 484 young_gen->from_space()->clear(SpaceDecorator::Mangle); 485 young_gen->swap_spaces(); 486 487 size_t survived = young_gen->from_space()->used_in_bytes(); 488 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before; 489 size_policy->update_averages(_survivor_overflow, survived, promoted); 490 491 // A successful scavenge should restart the GC time limit count which is 492 // for full GC's. 493 size_policy->reset_gc_overhead_limit_count(); 494 if (UseAdaptiveSizePolicy) { 495 // Calculate the new survivor size and tenuring threshold 496 497 if (PrintAdaptiveSizePolicy) { 498 gclog_or_tty->print("AdaptiveSizeStart: "); 499 gclog_or_tty->stamp(); 500 gclog_or_tty->print_cr(" collection: %d ", 501 heap->total_collections()); 502 503 if (Verbose) { 504 gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT 505 " young_gen_capacity: " SIZE_FORMAT, 506 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes()); 507 } 508 } 509 510 511 if (UsePerfData) { 512 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 513 counters->update_old_eden_size( 514 size_policy->calculated_eden_size_in_bytes()); 515 counters->update_old_promo_size( 516 size_policy->calculated_promo_size_in_bytes()); 517 counters->update_old_capacity(old_gen->capacity_in_bytes()); 518 counters->update_young_capacity(young_gen->capacity_in_bytes()); 519 counters->update_survived(survived); 520 counters->update_promoted(promoted); 521 counters->update_survivor_overflowed(_survivor_overflow); 522 } 523 524 size_t max_young_size = young_gen->max_size(); 525 526 // Deciding a free ratio in the young generation is tricky, so if 527 // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating 528 // that the old generation size may have been limited because of them) we 529 // should then limit our young generation size using NewRatio to have it 530 // follow the old generation size. 531 if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) { 532 max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size()); 533 } 534 535 size_t survivor_limit = 536 size_policy->max_survivor_size(max_young_size); 537 _tenuring_threshold = 538 size_policy->compute_survivor_space_size_and_threshold( 539 _survivor_overflow, 540 _tenuring_threshold, 541 survivor_limit); 542 543 if (PrintTenuringDistribution) { 544 gclog_or_tty->cr(); 545 gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u" 546 " (max threshold " UINTX_FORMAT ")", 547 size_policy->calculated_survivor_size_in_bytes(), 548 _tenuring_threshold, MaxTenuringThreshold); 549 } 550 551 if (UsePerfData) { 552 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 553 counters->update_tenuring_threshold(_tenuring_threshold); 554 counters->update_survivor_size_counters(); 555 } 556 557 // Do call at minor collections? 558 // Don't check if the size_policy is ready at this 559 // level. Let the size_policy check that internally. 560 if (UseAdaptiveGenerationSizePolicyAtMinorCollection && 561 (AdaptiveSizePolicy::should_update_eden_stats(gc_cause))) { 562 // Calculate optimal free space amounts 563 assert(young_gen->max_size() > 564 young_gen->from_space()->capacity_in_bytes() + 565 young_gen->to_space()->capacity_in_bytes(), 566 "Sizes of space in young gen are out-of-bounds"); 567 568 size_t young_live = young_gen->used_in_bytes(); 569 size_t eden_live = young_gen->eden_space()->used_in_bytes(); 570 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes(); 571 size_t max_old_gen_size = old_gen->max_gen_size(); 572 size_t max_eden_size = max_young_size - 573 young_gen->from_space()->capacity_in_bytes() - 574 young_gen->to_space()->capacity_in_bytes(); 575 576 // Used for diagnostics 577 size_policy->clear_generation_free_space_flags(); 578 579 size_policy->compute_eden_space_size(young_live, 580 eden_live, 581 cur_eden, 582 max_eden_size, 583 false /* not full gc*/); 584 585 size_policy->check_gc_overhead_limit(young_live, 586 eden_live, 587 max_old_gen_size, 588 max_eden_size, 589 false /* not full gc*/, 590 gc_cause, 591 heap->collector_policy()); 592 593 size_policy->decay_supplemental_growth(false /* not full gc*/); 594 } 595 // Resize the young generation at every collection 596 // even if new sizes have not been calculated. This is 597 // to allow resizes that may have been inhibited by the 598 // relative location of the "to" and "from" spaces. 599 600 // Resizing the old gen at young collections can cause increases 601 // that don't feed back to the generation sizing policy until 602 // a full collection. Don't resize the old gen here. 603 604 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(), 605 size_policy->calculated_survivor_size_in_bytes()); 606 607 if (PrintAdaptiveSizePolicy) { 608 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ", 609 heap->total_collections()); 610 } 611 } 612 613 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can 614 // cause the change of the heap layout. Make sure eden is reshaped if that's the case. 615 // Also update() will case adaptive NUMA chunk resizing. 616 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now"); 617 young_gen->eden_space()->update(); 618 619 heap->gc_policy_counters()->update_counters(); 620 621 heap->resize_all_tlabs(); 622 623 assert(young_gen->to_space()->is_empty(), "to space should be empty now"); 624 } 625 626 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 627 628 NOT_PRODUCT(reference_processor()->verify_no_references_recorded()); 629 630 { 631 GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer, _gc_tracer.gc_id()); 632 633 CodeCache::prune_scavenge_root_nmethods(); 634 } 635 636 // Re-verify object start arrays 637 if (VerifyObjectStartArray && 638 VerifyAfterGC) { 639 old_gen->verify_object_start_array(); 640 } 641 642 // Verify all old -> young cards are now precise 643 if (VerifyRememberedSets) { 644 // Precise verification will give false positives. Until this is fixed, 645 // use imprecise verification. 646 // CardTableExtension::verify_all_young_refs_precise(); 647 CardTableExtension::verify_all_young_refs_imprecise(); 648 } 649 650 if (TraceYoungGenTime) accumulated_time()->stop(); 651 652 if (PrintGC) { 653 if (PrintGCDetails) { 654 // Don't print a GC timestamp here. This is after the GC so 655 // would be confusing. 656 young_gen->print_used_change(young_gen_used_before); 657 } 658 heap->print_heap_change(prev_used); 659 } 660 661 // Track memory usage and detect low memory 662 MemoryService::track_memory_usage(); 663 heap->update_counters(); 664 665 gc_task_manager()->release_idle_workers(); 666 } 667 668 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) { 669 HandleMark hm; // Discard invalid handles created during verification 670 Universe::verify(" VerifyAfterGC:"); 671 } 672 673 heap->print_heap_after_gc(); 674 heap->trace_heap_after_gc(&_gc_tracer); 675 _gc_tracer.report_tenuring_threshold(tenuring_threshold()); 676 677 if (ZapUnusedHeapArea) { 678 young_gen->eden_space()->check_mangled_unused_area_complete(); 679 young_gen->from_space()->check_mangled_unused_area_complete(); 680 young_gen->to_space()->check_mangled_unused_area_complete(); 681 } 682 683 scavenge_exit.update(); 684 685 if (PrintGCTaskTimeStamps) { 686 tty->print_cr("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT, 687 scavenge_entry.ticks(), scavenge_midpoint.ticks(), 688 scavenge_exit.ticks()); 689 gc_task_manager()->print_task_time_stamps(); 690 } 691 692 #ifdef TRACESPINNING 693 ParallelTaskTerminator::print_termination_counts(); 694 #endif 695 696 697 _gc_timer.register_gc_end(); 698 699 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions()); 700 701 return !promotion_failure_occurred; 702 } 703 704 // This method iterates over all objects in the young generation, 705 // unforwarding markOops. It then restores any preserved mark oops, 706 // and clears the _preserved_mark_stack. 707 void PSScavenge::clean_up_failed_promotion() { 708 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 709 PSYoungGen* young_gen = heap->young_gen(); 710 711 { 712 ResourceMark rm; 713 714 // Unforward all pointers in the young gen. 715 PSPromotionFailedClosure unforward_closure; 716 young_gen->object_iterate(&unforward_closure); 717 718 if (PrintGC && Verbose) { 719 gclog_or_tty->print_cr("Restoring " SIZE_FORMAT " marks", _preserved_oop_stack.size()); 720 } 721 722 // Restore any saved marks. 723 while (!_preserved_oop_stack.is_empty()) { 724 oop obj = _preserved_oop_stack.pop(); 725 markOop mark = _preserved_mark_stack.pop(); 726 obj->set_mark(mark); 727 } 728 729 // Clear the preserved mark and oop stack caches. 730 _preserved_mark_stack.clear(true); 731 _preserved_oop_stack.clear(true); 732 } 733 734 // Reset the PromotionFailureALot counters. 735 NOT_PRODUCT(heap->reset_promotion_should_fail();) 736 } 737 738 // This method is called whenever an attempt to promote an object 739 // fails. Some markOops will need preservation, some will not. Note 740 // that the entire eden is traversed after a failed promotion, with 741 // all forwarded headers replaced by the default markOop. This means 742 // it is not necessary to preserve most markOops. 743 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) { 744 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) { 745 // Should use per-worker private stacks here rather than 746 // locking a common pair of stacks. 747 ThreadCritical tc; 748 _preserved_oop_stack.push(obj); 749 _preserved_mark_stack.push(obj_mark); 750 } 751 } 752 753 bool PSScavenge::should_attempt_scavenge() { 754 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 755 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters(); 756 757 if (UsePerfData) { 758 counters->update_scavenge_skipped(not_skipped); 759 } 760 761 PSYoungGen* young_gen = heap->young_gen(); 762 PSOldGen* old_gen = heap->old_gen(); 763 764 if (!ScavengeWithObjectsInToSpace) { 765 // Do not attempt to promote unless to_space is empty 766 if (!young_gen->to_space()->is_empty()) { 767 _consecutive_skipped_scavenges++; 768 if (UsePerfData) { 769 counters->update_scavenge_skipped(to_space_not_empty); 770 } 771 return false; 772 } 773 } 774 775 // Test to see if the scavenge will likely fail. 776 PSAdaptiveSizePolicy* policy = heap->size_policy(); 777 778 // A similar test is done in the policy's should_full_GC(). If this is 779 // changed, decide if that test should also be changed. 780 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes(); 781 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes()); 782 bool result = promotion_estimate < old_gen->free_in_bytes(); 783 784 if (PrintGCDetails && Verbose) { 785 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: "); 786 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT 787 " padded_average_promoted " SIZE_FORMAT 788 " free in old gen " SIZE_FORMAT, 789 (size_t) policy->average_promoted_in_bytes(), 790 (size_t) policy->padded_average_promoted_in_bytes(), 791 old_gen->free_in_bytes()); 792 if (young_gen->used_in_bytes() < 793 (size_t) policy->padded_average_promoted_in_bytes()) { 794 gclog_or_tty->print_cr(" padded_promoted_average is greater" 795 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes()); 796 } 797 } 798 799 if (result) { 800 _consecutive_skipped_scavenges = 0; 801 } else { 802 _consecutive_skipped_scavenges++; 803 if (UsePerfData) { 804 counters->update_scavenge_skipped(promoted_too_large); 805 } 806 } 807 return result; 808 } 809 810 // Used to add tasks 811 GCTaskManager* const PSScavenge::gc_task_manager() { 812 assert(ParallelScavengeHeap::gc_task_manager() != NULL, 813 "shouldn't return NULL"); 814 return ParallelScavengeHeap::gc_task_manager(); 815 } 816 817 void PSScavenge::initialize() { 818 // Arguments must have been parsed 819 820 if (AlwaysTenure || NeverTenure) { 821 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1, 822 "MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold); 823 _tenuring_threshold = MaxTenuringThreshold; 824 } else { 825 // We want to smooth out our startup times for the AdaptiveSizePolicy 826 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold : 827 MaxTenuringThreshold; 828 } 829 830 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); 831 PSYoungGen* young_gen = heap->young_gen(); 832 PSOldGen* old_gen = heap->old_gen(); 833 834 // Set boundary between young_gen and old_gen 835 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(), 836 "old above young"); 837 set_young_generation_boundary(young_gen->eden_space()->bottom()); 838 839 // Initialize ref handling object for scavenging. 840 MemRegion mr = young_gen->reserved(); 841 842 _ref_processor = 843 new ReferenceProcessor(mr, // span 844 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing 845 ParallelGCThreads, // mt processing degree 846 true, // mt discovery 847 ParallelGCThreads, // mt discovery degree 848 true, // atomic_discovery 849 NULL); // header provides liveness info 850 851 // Cache the cardtable 852 _card_table = barrier_set_cast<CardTableExtension>(heap->barrier_set()); 853 854 _counters = new CollectorCounters("PSScavenge", 0); 855 }