1 /*
   2  * Copyright (c) 2002, 2018, 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/gcTaskManager.hpp"
  29 #include "gc/parallel/parallelScavengeHeap.hpp"
  30 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
  31 #include "gc/parallel/psClosure.inline.hpp"
  32 #include "gc/parallel/psMarkSweepProxy.hpp"
  33 #include "gc/parallel/psParallelCompact.inline.hpp"
  34 #include "gc/parallel/psPromotionManager.inline.hpp"
  35 #include "gc/parallel/psScavenge.inline.hpp"
  36 #include "gc/parallel/psTasks.hpp"
  37 #include "gc/shared/collectorPolicy.hpp"
  38 #include "gc/shared/gcCause.hpp"
  39 #include "gc/shared/gcHeapSummary.hpp"
  40 #include "gc/shared/gcId.hpp"
  41 #include "gc/shared/gcLocker.hpp"
  42 #include "gc/shared/gcTimer.hpp"
  43 #include "gc/shared/gcTrace.hpp"
  44 #include "gc/shared/gcTraceTime.inline.hpp"
  45 #include "gc/shared/isGCActiveMark.hpp"
  46 #include "gc/shared/referencePolicy.hpp"
  47 #include "gc/shared/referenceProcessor.hpp"
  48 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
  49 #include "gc/shared/spaceDecorator.hpp"
  50 #include "gc/shared/weakProcessor.hpp"
  51 #include "memory/resourceArea.hpp"
  52 #include "logging/log.hpp"
  53 #include "oops/access.inline.hpp"
  54 #include "oops/compressedOops.inline.hpp"
  55 #include "oops/oop.inline.hpp"
  56 #include "runtime/biasedLocking.hpp"
  57 #include "runtime/handles.inline.hpp"
  58 #include "runtime/threadCritical.hpp"
  59 #include "runtime/vmThread.hpp"
  60 #include "runtime/vmOperations.hpp"
  61 #include "services/memoryService.hpp"
  62 #include "utilities/stack.inline.hpp"
  63 
  64 HeapWord*                     PSScavenge::_to_space_top_before_gc = NULL;
  65 int                           PSScavenge::_consecutive_skipped_scavenges = 0;
  66 SpanSubjectToDiscoveryClosure PSScavenge::_span_based_discoverer;
  67 ReferenceProcessor*           PSScavenge::_ref_processor = NULL;
  68 PSCardTable*                  PSScavenge::_card_table = NULL;
  69 bool                          PSScavenge::_survivor_overflow = false;
  70 uint                          PSScavenge::_tenuring_threshold = 0;
  71 HeapWord*                     PSScavenge::_young_generation_boundary = NULL;
  72 uintptr_t                     PSScavenge::_young_generation_boundary_compressed = 0;
  73 elapsedTimer                  PSScavenge::_accumulated_time;
  74 STWGCTimer                    PSScavenge::_gc_timer;
  75 ParallelScavengeTracer        PSScavenge::_gc_tracer;
  76 CollectorCounters*            PSScavenge::_counters = NULL;
  77 
  78 // Define before use
  79 class PSIsAliveClosure: public BoolObjectClosure {
  80 public:
  81   bool do_object_b(oop p) {
  82     return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
  83   }
  84 };
  85 
  86 PSIsAliveClosure PSScavenge::_is_alive_closure;
  87 
  88 class PSKeepAliveClosure: public OopClosure {
  89 protected:
  90   MutableSpace* _to_space;
  91   PSPromotionManager* _promotion_manager;
  92 
  93 public:
  94   PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
  95     ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
  96     _to_space = heap->young_gen()->to_space();
  97 
  98     assert(_promotion_manager != NULL, "Sanity");
  99   }
 100 
 101   template <class T> void do_oop_work(T* p) {
 102     assert (oopDesc::is_oop(RawAccess<IS_NOT_NULL>::oop_load(p)),
 103             "expected an oop while scanning weak refs");
 104 
 105     // Weak refs may be visited more than once.
 106     if (PSScavenge::should_scavenge(p, _to_space)) {
 107       _promotion_manager->copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(p);
 108     }
 109   }
 110   virtual void do_oop(oop* p)       { PSKeepAliveClosure::do_oop_work(p); }
 111   virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
 112 };
 113 
 114 class PSEvacuateFollowersClosure: public VoidClosure {
 115  private:
 116   PSPromotionManager* _promotion_manager;
 117  public:
 118   PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
 119 
 120   virtual void do_void() {
 121     assert(_promotion_manager != NULL, "Sanity");
 122     _promotion_manager->drain_stacks(true);
 123     guarantee(_promotion_manager->stacks_empty(),
 124               "stacks should be empty at this point");
 125   }
 126 };
 127 
 128 class PSRefProcTaskProxy: public GCTask {
 129   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 130   ProcessTask & _rp_task;
 131   uint          _work_id;
 132 public:
 133   PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
 134     : _rp_task(rp_task),
 135       _work_id(work_id)
 136   { }
 137 
 138 private:
 139   virtual char* name() { return (char *)"Process referents by policy in parallel"; }
 140   virtual void do_it(GCTaskManager* manager, uint which);
 141 };
 142 
 143 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
 144 {
 145   PSPromotionManager* promotion_manager =
 146     PSPromotionManager::gc_thread_promotion_manager(which);
 147   assert(promotion_manager != NULL, "sanity check");
 148   PSKeepAliveClosure keep_alive(promotion_manager);
 149   PSEvacuateFollowersClosure evac_followers(promotion_manager);
 150   PSIsAliveClosure is_alive;
 151   _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
 152 }
 153 
 154 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
 155   virtual void execute(ProcessTask& task, uint ergo_workers);
 156 };
 157 
 158 void PSRefProcTaskExecutor::execute(ProcessTask& task, uint ergo_workers)
 159 {
 160   GCTaskQueue* q = GCTaskQueue::create();
 161   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 162   uint active_workers = manager->active_workers();
 163 
 164   assert(active_workers == ergo_workers,
 165          "Ergonomically chosen workers (%u) must be equal to active workers (%u)",
 166          ergo_workers, active_workers);
 167 
 168   for(uint i=0; i < active_workers; i++) {
 169     q->enqueue(new PSRefProcTaskProxy(task, i));
 170   }
 171   ParallelTaskTerminator terminator(active_workers,
 172                                     (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
 173   if (task.marks_oops_alive() && active_workers > 1) {
 174     for (uint j = 0; j < active_workers; j++) {
 175       q->enqueue(new StealTask(&terminator));
 176     }
 177   }
 178   manager->execute_and_wait(q);
 179 }
 180 
 181 // This method contains all heap specific policy for invoking scavenge.
 182 // PSScavenge::invoke_no_policy() will do nothing but attempt to
 183 // scavenge. It will not clean up after failed promotions, bail out if
 184 // we've exceeded policy time limits, or any other special behavior.
 185 // All such policy should be placed here.
 186 //
 187 // Note that this method should only be called from the vm_thread while
 188 // at a safepoint!
 189 bool PSScavenge::invoke() {
 190   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 191   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 192   assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
 193 
 194   ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap();
 195   PSAdaptiveSizePolicy* policy = heap->size_policy();
 196   IsGCActiveMark mark;
 197 
 198   const bool scavenge_done = PSScavenge::invoke_no_policy();
 199   const bool need_full_gc = !scavenge_done ||
 200     policy->should_full_GC(heap->old_gen()->free_in_bytes());
 201   bool full_gc_done = false;
 202 
 203   if (UsePerfData) {
 204     PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
 205     const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
 206     counters->update_full_follows_scavenge(ffs_val);
 207   }
 208 
 209   if (need_full_gc) {
 210     GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
 211     SoftRefPolicy* srp = heap->soft_ref_policy();
 212     const bool clear_all_softrefs = srp->should_clear_all_soft_refs();
 213 
 214     if (UseParallelOldGC) {
 215       full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
 216     } else {
 217       full_gc_done = PSMarkSweepProxy::invoke_no_policy(clear_all_softrefs);
 218     }
 219   }
 220 
 221   return full_gc_done;
 222 }
 223 
 224 class PSAddThreadRootsTaskClosure : public ThreadClosure {
 225 private:
 226   GCTaskQueue* _q;
 227 
 228 public:
 229   PSAddThreadRootsTaskClosure(GCTaskQueue* q) : _q(q) { }
 230   void do_thread(Thread* t) {
 231     _q->enqueue(new ThreadRootsTask(t));
 232   }
 233 };
 234 
 235 // This method contains no policy. You should probably
 236 // be calling invoke() instead.
 237 bool PSScavenge::invoke_no_policy() {
 238   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 239   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 240 
 241   _gc_timer.register_gc_start();
 242 
 243   TimeStamp scavenge_entry;
 244   TimeStamp scavenge_midpoint;
 245   TimeStamp scavenge_exit;
 246 
 247   scavenge_entry.update();
 248 
 249   if (GCLocker::check_active_before_gc()) {
 250     return false;
 251   }
 252 
 253   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 254   GCCause::Cause gc_cause = heap->gc_cause();
 255 
 256   // Check for potential problems.
 257   if (!should_attempt_scavenge()) {
 258     return false;
 259   }
 260 
 261   GCIdMark gc_id_mark;
 262   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
 263 
 264   bool promotion_failure_occurred = false;
 265 
 266   PSYoungGen* young_gen = heap->young_gen();
 267   PSOldGen* old_gen = heap->old_gen();
 268   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
 269 
 270   heap->increment_total_collections();
 271 
 272   if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
 273     // Gather the feedback data for eden occupancy.
 274     young_gen->eden_space()->accumulate_statistics();
 275   }
 276 
 277   heap->print_heap_before_gc();
 278   heap->trace_heap_before_gc(&_gc_tracer);
 279 
 280   assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
 281   assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
 282 
 283   // Fill in TLABs
 284   heap->ensure_parsability(true);  // retire TLABs
 285 
 286   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 287     HandleMark hm;  // Discard invalid handles created during verification
 288     Universe::verify("Before GC");
 289   }
 290 
 291   {
 292     ResourceMark rm;
 293     HandleMark hm;
 294 
 295     GCTraceCPUTime tcpu;
 296     GCTraceTime(Info, gc) tm("Pause Young", NULL, gc_cause, true);
 297     TraceCollectorStats tcs(counters());
 298     TraceMemoryManagerStats tms(heap->young_gc_manager(), gc_cause);
 299 
 300     if (log_is_enabled(Debug, gc, heap, exit)) {
 301       accumulated_time()->start();
 302     }
 303 
 304     // Let the size policy know we're starting
 305     size_policy->minor_collection_begin();
 306 
 307     // Verify the object start arrays.
 308     if (VerifyObjectStartArray &&
 309         VerifyBeforeGC) {
 310       old_gen->verify_object_start_array();
 311     }
 312 
 313     // Verify no unmarked old->young roots
 314     if (VerifyRememberedSets) {
 315       heap->card_table()->verify_all_young_refs_imprecise();
 316     }
 317 
 318     assert(young_gen->to_space()->is_empty(),
 319            "Attempt to scavenge with live objects in to_space");
 320     young_gen->to_space()->clear(SpaceDecorator::Mangle);
 321 
 322     save_to_space_top_before_gc();
 323 
 324 #if COMPILER2_OR_JVMCI
 325     DerivedPointerTable::clear();
 326 #endif
 327 
 328     reference_processor()->enable_discovery();
 329     reference_processor()->setup_policy(false);
 330 
 331     PreGCValues pre_gc_values(heap);
 332 
 333     // Reset our survivor overflow.
 334     set_survivor_overflow(false);
 335 
 336     // We need to save the old top values before
 337     // creating the promotion_manager. We pass the top
 338     // values to the card_table, to prevent it from
 339     // straying into the promotion labs.
 340     HeapWord* old_top = old_gen->object_space()->top();
 341 
 342     // Release all previously held resources
 343     gc_task_manager()->release_all_resources();
 344 
 345     // Set the number of GC threads to be used in this collection
 346     gc_task_manager()->set_active_gang();
 347     gc_task_manager()->task_idle_workers();
 348     // Get the active number of workers here and use that value
 349     // throughout the methods.
 350     uint active_workers = gc_task_manager()->active_workers();
 351 
 352     PSPromotionManager::pre_scavenge();
 353 
 354     // We'll use the promotion manager again later.
 355     PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
 356     {
 357       GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
 358       ParallelScavengeHeap::ParStrongRootsScope psrs;
 359 
 360       GCTaskQueue* q = GCTaskQueue::create();
 361 
 362       if (!old_gen->object_space()->is_empty()) {
 363         // There are only old-to-young pointers if there are objects
 364         // in the old gen.
 365         uint stripe_total = active_workers;
 366         for(uint i=0; i < stripe_total; i++) {
 367           q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
 368         }
 369       }
 370 
 371       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
 372       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
 373       // We scan the thread roots in parallel
 374       PSAddThreadRootsTaskClosure cl(q);
 375       Threads::java_threads_and_vm_thread_do(&cl);
 376       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
 377       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
 378       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
 379       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
 380       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
 381       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
 382 
 383       ParallelTaskTerminator terminator(
 384         active_workers,
 385                   (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
 386         // If active_workers can exceed 1, add a StrealTask.
 387         // PSPromotionManager::drain_stacks_depth() does not fully drain its
 388         // stacks and expects a StealTask to complete the draining if
 389         // ParallelGCThreads is > 1.
 390         if (gc_task_manager()->workers() > 1) {
 391           for (uint j = 0; j < active_workers; j++) {
 392             q->enqueue(new StealTask(&terminator));
 393           }
 394         }
 395 
 396       gc_task_manager()->execute_and_wait(q);
 397     }
 398 
 399     scavenge_midpoint.update();
 400 
 401     // Process reference objects discovered during scavenge
 402     {
 403       GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
 404 
 405       reference_processor()->setup_policy(false); // not always_clear
 406       reference_processor()->set_active_mt_degree(active_workers);
 407       PSKeepAliveClosure keep_alive(promotion_manager);
 408       PSEvacuateFollowersClosure evac_followers(promotion_manager);
 409       ReferenceProcessorStats stats;
 410       ReferenceProcessorPhaseTimes pt(&_gc_timer, reference_processor()->max_num_queues());
 411       if (reference_processor()->processing_is_mt()) {
 412         PSRefProcTaskExecutor task_executor;
 413         stats = reference_processor()->process_discovered_references(
 414           &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
 415           &pt);
 416       } else {
 417         stats = reference_processor()->process_discovered_references(
 418           &_is_alive_closure, &keep_alive, &evac_followers, NULL, &pt);
 419       }
 420 
 421       _gc_tracer.report_gc_reference_stats(stats);
 422       pt.print_all_references();
 423     }
 424 
 425     assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
 426 
 427     PSScavengeRootsClosure root_closure(promotion_manager);
 428 
 429     {
 430       GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
 431       WeakProcessor::weak_oops_do(&_is_alive_closure, &root_closure);
 432     }
 433 
 434     {
 435       GCTraceTime(Debug, gc, phases) tm("Scrub String Table", &_gc_timer);
 436       // Unlink any dead interned Strings and process the remaining live ones.
 437       StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
 438     }
 439 
 440     // Verify that usage of root_closure didn't copy any objects.
 441     assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
 442 
 443     // Finally, flush the promotion_manager's labs, and deallocate its stacks.
 444     promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
 445     if (promotion_failure_occurred) {
 446       clean_up_failed_promotion();
 447       log_info(gc, promotion)("Promotion failed");
 448     }
 449 
 450     _gc_tracer.report_tenuring_threshold(tenuring_threshold());
 451 
 452     // Let the size policy know we're done.  Note that we count promotion
 453     // failure cleanup time as part of the collection (otherwise, we're
 454     // implicitly saying it's mutator time).
 455     size_policy->minor_collection_end(gc_cause);
 456 
 457     if (!promotion_failure_occurred) {
 458       // Swap the survivor spaces.
 459       young_gen->eden_space()->clear(SpaceDecorator::Mangle);
 460       young_gen->from_space()->clear(SpaceDecorator::Mangle);
 461       young_gen->swap_spaces();
 462 
 463       size_t survived = young_gen->from_space()->used_in_bytes();
 464       size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
 465       size_policy->update_averages(_survivor_overflow, survived, promoted);
 466 
 467       // A successful scavenge should restart the GC time limit count which is
 468       // for full GC's.
 469       size_policy->reset_gc_overhead_limit_count();
 470       if (UseAdaptiveSizePolicy) {
 471         // Calculate the new survivor size and tenuring threshold
 472 
 473         log_debug(gc, ergo)("AdaptiveSizeStart:  collection: %d ", heap->total_collections());
 474         log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
 475                             old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
 476 
 477         if (UsePerfData) {
 478           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 479           counters->update_old_eden_size(
 480             size_policy->calculated_eden_size_in_bytes());
 481           counters->update_old_promo_size(
 482             size_policy->calculated_promo_size_in_bytes());
 483           counters->update_old_capacity(old_gen->capacity_in_bytes());
 484           counters->update_young_capacity(young_gen->capacity_in_bytes());
 485           counters->update_survived(survived);
 486           counters->update_promoted(promoted);
 487           counters->update_survivor_overflowed(_survivor_overflow);
 488         }
 489 
 490         size_t max_young_size = young_gen->max_size();
 491 
 492         // Deciding a free ratio in the young generation is tricky, so if
 493         // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
 494         // that the old generation size may have been limited because of them) we
 495         // should then limit our young generation size using NewRatio to have it
 496         // follow the old generation size.
 497         if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
 498           max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
 499         }
 500 
 501         size_t survivor_limit =
 502           size_policy->max_survivor_size(max_young_size);
 503         _tenuring_threshold =
 504           size_policy->compute_survivor_space_size_and_threshold(
 505                                                            _survivor_overflow,
 506                                                            _tenuring_threshold,
 507                                                            survivor_limit);
 508 
 509        log_debug(gc, age)("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max threshold " UINTX_FORMAT ")",
 510                           size_policy->calculated_survivor_size_in_bytes(),
 511                           _tenuring_threshold, MaxTenuringThreshold);
 512 
 513         if (UsePerfData) {
 514           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 515           counters->update_tenuring_threshold(_tenuring_threshold);
 516           counters->update_survivor_size_counters();
 517         }
 518 
 519         // Do call at minor collections?
 520         // Don't check if the size_policy is ready at this
 521         // level.  Let the size_policy check that internally.
 522         if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
 523             (AdaptiveSizePolicy::should_update_eden_stats(gc_cause))) {
 524           // Calculate optimal free space amounts
 525           assert(young_gen->max_size() >
 526             young_gen->from_space()->capacity_in_bytes() +
 527             young_gen->to_space()->capacity_in_bytes(),
 528             "Sizes of space in young gen are out-of-bounds");
 529 
 530           size_t young_live = young_gen->used_in_bytes();
 531           size_t eden_live = young_gen->eden_space()->used_in_bytes();
 532           size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
 533           size_t max_old_gen_size = old_gen->max_gen_size();
 534           size_t max_eden_size = max_young_size -
 535             young_gen->from_space()->capacity_in_bytes() -
 536             young_gen->to_space()->capacity_in_bytes();
 537 
 538           // Used for diagnostics
 539           size_policy->clear_generation_free_space_flags();
 540 
 541           size_policy->compute_eden_space_size(young_live,
 542                                                eden_live,
 543                                                cur_eden,
 544                                                max_eden_size,
 545                                                false /* not full gc*/);
 546 
 547           size_policy->check_gc_overhead_limit(young_live,
 548                                                eden_live,
 549                                                max_old_gen_size,
 550                                                max_eden_size,
 551                                                false /* not full gc*/,
 552                                                gc_cause,
 553                                                heap->soft_ref_policy());
 554 
 555           size_policy->decay_supplemental_growth(false /* not full gc*/);
 556         }
 557         // Resize the young generation at every collection
 558         // even if new sizes have not been calculated.  This is
 559         // to allow resizes that may have been inhibited by the
 560         // relative location of the "to" and "from" spaces.
 561 
 562         // Resizing the old gen at young collections can cause increases
 563         // that don't feed back to the generation sizing policy until
 564         // a full collection.  Don't resize the old gen here.
 565 
 566         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
 567                         size_policy->calculated_survivor_size_in_bytes());
 568 
 569         log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
 570       }
 571 
 572       // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
 573       // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
 574       // Also update() will case adaptive NUMA chunk resizing.
 575       assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
 576       young_gen->eden_space()->update();
 577 
 578       heap->gc_policy_counters()->update_counters();
 579 
 580       heap->resize_all_tlabs();
 581 
 582       assert(young_gen->to_space()->is_empty(), "to space should be empty now");
 583     }
 584 
 585 #if COMPILER2_OR_JVMCI
 586     DerivedPointerTable::update_pointers();
 587 #endif
 588 
 589     NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
 590 
 591     // Re-verify object start arrays
 592     if (VerifyObjectStartArray &&
 593         VerifyAfterGC) {
 594       old_gen->verify_object_start_array();
 595     }
 596 
 597     // Verify all old -> young cards are now precise
 598     if (VerifyRememberedSets) {
 599       // Precise verification will give false positives. Until this is fixed,
 600       // use imprecise verification.
 601       // heap->card_table()->verify_all_young_refs_precise();
 602       heap->card_table()->verify_all_young_refs_imprecise();
 603     }
 604 
 605     if (log_is_enabled(Debug, gc, heap, exit)) {
 606       accumulated_time()->stop();
 607     }
 608 
 609     young_gen->print_used_change(pre_gc_values.young_gen_used());
 610     old_gen->print_used_change(pre_gc_values.old_gen_used());
 611     MetaspaceUtils::print_metaspace_change(pre_gc_values.metadata_used());
 612 
 613     // Track memory usage and detect low memory
 614     MemoryService::track_memory_usage();
 615     heap->update_counters();
 616 
 617     gc_task_manager()->release_idle_workers();
 618   }
 619 
 620   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 621     HandleMark hm;  // Discard invalid handles created during verification
 622     Universe::verify("After GC");
 623   }
 624 
 625   heap->print_heap_after_gc();
 626   heap->trace_heap_after_gc(&_gc_tracer);
 627 
 628   scavenge_exit.update();
 629 
 630   log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
 631                             scavenge_entry.ticks(), scavenge_midpoint.ticks(),
 632                             scavenge_exit.ticks());
 633   gc_task_manager()->print_task_time_stamps();
 634 
 635 #ifdef TRACESPINNING
 636   ParallelTaskTerminator::print_termination_counts();
 637 #endif
 638 
 639   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
 640 
 641   _gc_timer.register_gc_end();
 642 
 643   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
 644 
 645   return !promotion_failure_occurred;
 646 }
 647 
 648 // This method iterates over all objects in the young generation,
 649 // removing all forwarding references. It then restores any preserved marks.
 650 void PSScavenge::clean_up_failed_promotion() {
 651   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 652   PSYoungGen* young_gen = heap->young_gen();
 653 
 654   RemoveForwardedPointerClosure remove_fwd_ptr_closure;
 655   young_gen->object_iterate(&remove_fwd_ptr_closure);
 656 
 657   PSPromotionManager::restore_preserved_marks();
 658 
 659   // Reset the PromotionFailureALot counters.
 660   NOT_PRODUCT(heap->reset_promotion_should_fail();)
 661 }
 662 
 663 bool PSScavenge::should_attempt_scavenge() {
 664   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 665   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 666 
 667   if (UsePerfData) {
 668     counters->update_scavenge_skipped(not_skipped);
 669   }
 670 
 671   PSYoungGen* young_gen = heap->young_gen();
 672   PSOldGen* old_gen = heap->old_gen();
 673 
 674   // Do not attempt to promote unless to_space is empty
 675   if (!young_gen->to_space()->is_empty()) {
 676     _consecutive_skipped_scavenges++;
 677     if (UsePerfData) {
 678       counters->update_scavenge_skipped(to_space_not_empty);
 679     }
 680     return false;
 681   }
 682 
 683   // Test to see if the scavenge will likely fail.
 684   PSAdaptiveSizePolicy* policy = heap->size_policy();
 685 
 686   // A similar test is done in the policy's should_full_GC().  If this is
 687   // changed, decide if that test should also be changed.
 688   size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
 689   size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
 690   bool result = promotion_estimate < old_gen->free_in_bytes();
 691 
 692   log_trace(ergo)("%s scavenge: average_promoted " SIZE_FORMAT " padded_average_promoted " SIZE_FORMAT " free in old gen " SIZE_FORMAT,
 693                 result ? "Do" : "Skip", (size_t) policy->average_promoted_in_bytes(),
 694                 (size_t) policy->padded_average_promoted_in_bytes(),
 695                 old_gen->free_in_bytes());
 696   if (young_gen->used_in_bytes() < (size_t) policy->padded_average_promoted_in_bytes()) {
 697     log_trace(ergo)(" padded_promoted_average is greater than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
 698   }
 699 
 700   if (result) {
 701     _consecutive_skipped_scavenges = 0;
 702   } else {
 703     _consecutive_skipped_scavenges++;
 704     if (UsePerfData) {
 705       counters->update_scavenge_skipped(promoted_too_large);
 706     }
 707   }
 708   return result;
 709 }
 710 
 711   // Used to add tasks
 712 GCTaskManager* const PSScavenge::gc_task_manager() {
 713   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
 714    "shouldn't return NULL");
 715   return ParallelScavengeHeap::gc_task_manager();
 716 }
 717 
 718 // Adaptive size policy support.  When the young generation/old generation
 719 // boundary moves, _young_generation_boundary must be reset
 720 void PSScavenge::set_young_generation_boundary(HeapWord* v) {
 721   _young_generation_boundary = v;
 722   if (UseCompressedOops) {
 723     _young_generation_boundary_compressed = (uintptr_t)CompressedOops::encode((oop)v);
 724   }
 725 }
 726 
 727 void PSScavenge::initialize() {
 728   // Arguments must have been parsed
 729 
 730   if (AlwaysTenure || NeverTenure) {
 731     assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
 732            "MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold);
 733     _tenuring_threshold = MaxTenuringThreshold;
 734   } else {
 735     // We want to smooth out our startup times for the AdaptiveSizePolicy
 736     _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
 737                                                     MaxTenuringThreshold;
 738   }
 739 
 740   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 741   PSYoungGen* young_gen = heap->young_gen();
 742   PSOldGen* old_gen = heap->old_gen();
 743 
 744   // Set boundary between young_gen and old_gen
 745   assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
 746          "old above young");
 747   set_young_generation_boundary(young_gen->eden_space()->bottom());
 748 
 749   // Initialize ref handling object for scavenging.
 750   _span_based_discoverer.set_span(young_gen->reserved());
 751   _ref_processor =
 752     new ReferenceProcessor(&_span_based_discoverer,
 753                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 754                            ParallelGCThreads,          // mt processing degree
 755                            true,                       // mt discovery
 756                            ParallelGCThreads,          // mt discovery degree
 757                            true,                       // atomic_discovery
 758                            NULL,                       // header provides liveness info
 759                            false);
 760 
 761   // Cache the cardtable
 762   _card_table = heap->card_table();
 763 
 764   _counters = new CollectorCounters("PSScavenge", 0);
 765 }