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/psMarkSweep.hpp"
  32 #include "gc/parallel/psParallelCompact.inline.hpp"
  33 #include "gc/parallel/psScavenge.inline.hpp"
  34 #include "gc/parallel/psTasks.hpp"
  35 #include "gc/shared/collectorPolicy.hpp"
  36 #include "gc/shared/gcCause.hpp"
  37 #include "gc/shared/gcHeapSummary.hpp"
  38 #include "gc/shared/gcId.hpp"
  39 #include "gc/shared/gcLocker.hpp"
  40 #include "gc/shared/gcTimer.hpp"
  41 #include "gc/shared/gcTrace.hpp"
  42 #include "gc/shared/gcTraceTime.inline.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 "gc/shared/weakProcessor.hpp"
  48 #include "memory/resourceArea.hpp"
  49 #include "logging/log.hpp"
  50 #include "oops/access.inline.hpp"
  51 #include "oops/compressedOops.inline.hpp"
  52 #include "oops/oop.inline.hpp"
  53 #include "runtime/biasedLocking.hpp"
  54 #include "runtime/handles.inline.hpp"
  55 #include "runtime/threadCritical.hpp"
  56 #include "runtime/vmThread.hpp"
  57 #include "runtime/vm_operations.hpp"
  58 #include "services/memoryService.hpp"
  59 #include "utilities/stack.inline.hpp"
  60 
  61 HeapWord*                  PSScavenge::_to_space_top_before_gc = NULL;
  62 int                        PSScavenge::_consecutive_skipped_scavenges = 0;
  63 ReferenceProcessor*        PSScavenge::_ref_processor = NULL;
  64 PSCardTable*               PSScavenge::_card_table = NULL;
  65 bool                       PSScavenge::_survivor_overflow = false;
  66 uint                       PSScavenge::_tenuring_threshold = 0;
  67 HeapWord*                  PSScavenge::_young_generation_boundary = NULL;
  68 uintptr_t                  PSScavenge::_young_generation_boundary_compressed = 0;
  69 elapsedTimer               PSScavenge::_accumulated_time;
  70 STWGCTimer                 PSScavenge::_gc_timer;
  71 ParallelScavengeTracer     PSScavenge::_gc_tracer;
  72 CollectorCounters*         PSScavenge::_counters = NULL;
  73 
  74 // Define before use
  75 class PSIsAliveClosure: public BoolObjectClosure {
  76 public:
  77   bool do_object_b(oop p) {
  78     return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
  79   }
  80 };
  81 
  82 PSIsAliveClosure PSScavenge::_is_alive_closure;
  83 
  84 class PSKeepAliveClosure: public OopClosure {
  85 protected:
  86   MutableSpace* _to_space;
  87   PSPromotionManager* _promotion_manager;
  88 
  89 public:
  90   PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
  91     ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
  92     _to_space = heap->young_gen()->to_space();
  93 
  94     assert(_promotion_manager != NULL, "Sanity");
  95   }
  96 
  97   template <class T> void do_oop_work(T* p) {
  98     assert (oopDesc::is_oop(RawAccess<OOP_NOT_NULL>::oop_load(p)),
  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 PSRefProcTaskProxy: public GCTask {
 125   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 126   ProcessTask & _rp_task;
 127   uint          _work_id;
 128 public:
 129   PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
 130     : _rp_task(rp_task),
 131       _work_id(work_id)
 132   { }
 133 
 134 private:
 135   virtual char* name() { return (char *)"Process referents by policy in parallel"; }
 136   virtual void do_it(GCTaskManager* manager, uint which);
 137 };
 138 
 139 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
 140 {
 141   PSPromotionManager* promotion_manager =
 142     PSPromotionManager::gc_thread_promotion_manager(which);
 143   assert(promotion_manager != NULL, "sanity check");
 144   PSKeepAliveClosure keep_alive(promotion_manager);
 145   PSEvacuateFollowersClosure evac_followers(promotion_manager);
 146   PSIsAliveClosure is_alive;
 147   _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
 148 }
 149 
 150 class PSRefEnqueueTaskProxy: public GCTask {
 151   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 152   EnqueueTask& _enq_task;
 153   uint         _work_id;
 154 
 155 public:
 156   PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
 157     : _enq_task(enq_task),
 158       _work_id(work_id)
 159   { }
 160 
 161   virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
 162   virtual void do_it(GCTaskManager* manager, uint which)
 163   {
 164     _enq_task.work(_work_id);
 165   }
 166 };
 167 
 168 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
 169   virtual void execute(ProcessTask& task);
 170   virtual void execute(EnqueueTask& task);
 171 };
 172 
 173 void PSRefProcTaskExecutor::execute(ProcessTask& task)
 174 {
 175   GCTaskQueue* q = GCTaskQueue::create();
 176   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 177   for(uint i=0; i < manager->active_workers(); i++) {
 178     q->enqueue(new PSRefProcTaskProxy(task, i));
 179   }
 180   ParallelTaskTerminator terminator(manager->active_workers(),
 181                  (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
 182   if (task.marks_oops_alive() && manager->active_workers() > 1) {
 183     for (uint j = 0; j < manager->active_workers(); j++) {
 184       q->enqueue(new StealTask(&terminator));
 185     }
 186   }
 187   manager->execute_and_wait(q);
 188 }
 189 
 190 
 191 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
 192 {
 193   GCTaskQueue* q = GCTaskQueue::create();
 194   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 195   for(uint i=0; i < manager->active_workers(); i++) {
 196     q->enqueue(new PSRefEnqueueTaskProxy(task, i));
 197   }
 198   manager->execute_and_wait(q);
 199 }
 200 
 201 // This method contains all heap specific policy for invoking scavenge.
 202 // PSScavenge::invoke_no_policy() will do nothing but attempt to
 203 // scavenge. It will not clean up after failed promotions, bail out if
 204 // we've exceeded policy time limits, or any other special behavior.
 205 // All such policy should be placed here.
 206 //
 207 // Note that this method should only be called from the vm_thread while
 208 // at a safepoint!
 209 bool PSScavenge::invoke() {
 210   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 211   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 212   assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
 213 
 214   ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap();
 215   PSAdaptiveSizePolicy* policy = heap->size_policy();
 216   IsGCActiveMark mark;
 217 
 218   const bool scavenge_done = PSScavenge::invoke_no_policy();
 219   const bool need_full_gc = !scavenge_done ||
 220     policy->should_full_GC(heap->old_gen()->free_in_bytes());
 221   bool full_gc_done = false;
 222 
 223   if (UsePerfData) {
 224     PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
 225     const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
 226     counters->update_full_follows_scavenge(ffs_val);
 227   }
 228 
 229   if (need_full_gc) {
 230     GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
 231     SoftRefPolicy* srp = heap->soft_ref_policy();
 232     const bool clear_all_softrefs = srp->should_clear_all_soft_refs();
 233 
 234     if (UseParallelOldGC) {
 235       full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
 236     } else {
 237       full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
 238     }
 239   }
 240 
 241   return full_gc_done;
 242 }
 243 
 244 // This method contains no policy. You should probably
 245 // be calling invoke() instead.
 246 bool PSScavenge::invoke_no_policy() {
 247   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 248   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 249 
 250   _gc_timer.register_gc_start();
 251 
 252   TimeStamp scavenge_entry;
 253   TimeStamp scavenge_midpoint;
 254   TimeStamp scavenge_exit;
 255 
 256   scavenge_entry.update();
 257 
 258   if (GCLocker::check_active_before_gc()) {
 259     return false;
 260   }
 261 
 262   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 263   GCCause::Cause gc_cause = heap->gc_cause();
 264 
 265   // Check for potential problems.
 266   if (!should_attempt_scavenge()) {
 267     return false;
 268   }
 269 
 270   GCIdMark gc_id_mark;
 271   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
 272 
 273   bool promotion_failure_occurred = false;
 274 
 275   PSYoungGen* young_gen = heap->young_gen();
 276   PSOldGen* old_gen = heap->old_gen();
 277   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
 278 
 279   heap->increment_total_collections();
 280 
 281   if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
 282     // Gather the feedback data for eden occupancy.
 283     young_gen->eden_space()->accumulate_statistics();
 284   }
 285 
 286   heap->print_heap_before_gc();
 287   heap->trace_heap_before_gc(&_gc_tracer);
 288 
 289   assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
 290   assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
 291 
 292   // Fill in TLABs
 293   heap->accumulate_statistics_all_tlabs();
 294   heap->ensure_parsability(true);  // retire TLABs
 295 
 296   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 297     HandleMark hm;  // Discard invalid handles created during verification
 298     Universe::verify("Before GC");
 299   }
 300 
 301   {
 302     ResourceMark rm;
 303     HandleMark hm;
 304 
 305     GCTraceCPUTime tcpu;
 306     GCTraceTime(Info, gc) tm("Pause Young", NULL, gc_cause, true);
 307     TraceCollectorStats tcs(counters());
 308     TraceMemoryManagerStats tms(heap->young_gc_manager(), gc_cause);
 309 
 310     if (log_is_enabled(Debug, gc, heap, exit)) {
 311       accumulated_time()->start();
 312     }
 313 
 314     // Let the size policy know we're starting
 315     size_policy->minor_collection_begin();
 316 
 317     // Verify the object start arrays.
 318     if (VerifyObjectStartArray &&
 319         VerifyBeforeGC) {
 320       old_gen->verify_object_start_array();
 321     }
 322 
 323     // Verify no unmarked old->young roots
 324     if (VerifyRememberedSets) {
 325       heap->card_table()->verify_all_young_refs_imprecise();
 326     }
 327 
 328     assert(young_gen->to_space()->is_empty(),
 329            "Attempt to scavenge with live objects in to_space");
 330     young_gen->to_space()->clear(SpaceDecorator::Mangle);
 331 
 332     save_to_space_top_before_gc();
 333 
 334 #if COMPILER2_OR_JVMCI
 335     DerivedPointerTable::clear();
 336 #endif
 337 
 338     reference_processor()->enable_discovery();
 339     reference_processor()->setup_policy(false);
 340 
 341     PreGCValues pre_gc_values(heap);
 342 
 343     // Reset our survivor overflow.
 344     set_survivor_overflow(false);
 345 
 346     // We need to save the old top values before
 347     // creating the promotion_manager. We pass the top
 348     // values to the card_table, to prevent it from
 349     // straying into the promotion labs.
 350     HeapWord* old_top = old_gen->object_space()->top();
 351 
 352     // Release all previously held resources
 353     gc_task_manager()->release_all_resources();
 354 
 355     // Set the number of GC threads to be used in this collection
 356     gc_task_manager()->set_active_gang();
 357     gc_task_manager()->task_idle_workers();
 358     // Get the active number of workers here and use that value
 359     // throughout the methods.
 360     uint active_workers = gc_task_manager()->active_workers();
 361 
 362     PSPromotionManager::pre_scavenge();
 363 
 364     // We'll use the promotion manager again later.
 365     PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
 366     {
 367       GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
 368       ParallelScavengeHeap::ParStrongRootsScope psrs;
 369 
 370       GCTaskQueue* q = GCTaskQueue::create();
 371 
 372       if (!old_gen->object_space()->is_empty()) {
 373         // There are only old-to-young pointers if there are objects
 374         // in the old gen.
 375         uint stripe_total = active_workers;
 376         for(uint i=0; i < stripe_total; i++) {
 377           q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
 378         }
 379       }
 380 
 381       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
 382       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
 383       // We scan the thread roots in parallel
 384       Threads::create_thread_roots_tasks(q);
 385       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
 386       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
 387       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
 388       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
 389       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
 390       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
 391 
 392       ParallelTaskTerminator terminator(
 393         active_workers,
 394                   (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
 395         // If active_workers can exceed 1, add a StrealTask.
 396         // PSPromotionManager::drain_stacks_depth() does not fully drain its
 397         // stacks and expects a StealTask to complete the draining if
 398         // ParallelGCThreads is > 1.
 399         if (gc_task_manager()->workers() > 1) {
 400           for (uint j = 0; j < active_workers; j++) {
 401             q->enqueue(new StealTask(&terminator));
 402           }
 403         }
 404 
 405       gc_task_manager()->execute_and_wait(q);
 406     }
 407 
 408     scavenge_midpoint.update();
 409 
 410     // Process reference objects discovered during scavenge
 411     {
 412       GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
 413 
 414       reference_processor()->setup_policy(false); // not always_clear
 415       reference_processor()->set_active_mt_degree(active_workers);
 416       PSKeepAliveClosure keep_alive(promotion_manager);
 417       PSEvacuateFollowersClosure evac_followers(promotion_manager);
 418       ReferenceProcessorStats stats;
 419       ReferenceProcessorPhaseTimes pt(&_gc_timer, reference_processor()->num_q());
 420       if (reference_processor()->processing_is_mt()) {
 421         PSRefProcTaskExecutor task_executor;
 422         stats = reference_processor()->process_discovered_references(
 423           &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
 424           &pt);
 425       } else {
 426         stats = reference_processor()->process_discovered_references(
 427           &_is_alive_closure, &keep_alive, &evac_followers, NULL, &pt);
 428       }
 429 
 430       _gc_tracer.report_gc_reference_stats(stats);
 431       pt.print_all_references();
 432 
 433       // Enqueue reference objects discovered during scavenge.
 434       if (reference_processor()->processing_is_mt()) {
 435         PSRefProcTaskExecutor task_executor;
 436         reference_processor()->enqueue_discovered_references(&task_executor, &pt);
 437       } else {
 438         reference_processor()->enqueue_discovered_references(NULL, &pt);
 439       }
 440 
 441       pt.print_enqueue_phase();
 442     }
 443 
 444     assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
 445 
 446     PSScavengeRootsClosure root_closure(promotion_manager);
 447 
 448     {
 449       GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
 450       WeakProcessor::weak_oops_do(&_is_alive_closure, &root_closure);
 451     }
 452 
 453     {
 454       GCTraceTime(Debug, gc, phases) tm("Scrub String Table", &_gc_timer);
 455       // Unlink any dead interned Strings and process the remaining live ones.
 456       StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
 457     }
 458 
 459     // Verify that usage of root_closure didn't copy any objects.
 460     assert(promotion_manager->stacks_empty(),"stacks should be empty at this point");
 461 
 462     // Finally, flush the promotion_manager's labs, and deallocate its stacks.
 463     promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
 464     if (promotion_failure_occurred) {
 465       clean_up_failed_promotion();
 466       log_info(gc, promotion)("Promotion failed");
 467     }
 468 
 469     _gc_tracer.report_tenuring_threshold(tenuring_threshold());
 470 
 471     // Let the size policy know we're done.  Note that we count promotion
 472     // failure cleanup time as part of the collection (otherwise, we're
 473     // implicitly saying it's mutator time).
 474     size_policy->minor_collection_end(gc_cause);
 475 
 476     if (!promotion_failure_occurred) {
 477       // Swap the survivor spaces.
 478       young_gen->eden_space()->clear(SpaceDecorator::Mangle);
 479       young_gen->from_space()->clear(SpaceDecorator::Mangle);
 480       young_gen->swap_spaces();
 481 
 482       size_t survived = young_gen->from_space()->used_in_bytes();
 483       size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
 484       size_policy->update_averages(_survivor_overflow, survived, promoted);
 485 
 486       // A successful scavenge should restart the GC time limit count which is
 487       // for full GC's.
 488       size_policy->reset_gc_overhead_limit_count();
 489       if (UseAdaptiveSizePolicy) {
 490         // Calculate the new survivor size and tenuring threshold
 491 
 492         log_debug(gc, ergo)("AdaptiveSizeStart:  collection: %d ", heap->total_collections());
 493         log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
 494                             old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
 495 
 496         if (UsePerfData) {
 497           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 498           counters->update_old_eden_size(
 499             size_policy->calculated_eden_size_in_bytes());
 500           counters->update_old_promo_size(
 501             size_policy->calculated_promo_size_in_bytes());
 502           counters->update_old_capacity(old_gen->capacity_in_bytes());
 503           counters->update_young_capacity(young_gen->capacity_in_bytes());
 504           counters->update_survived(survived);
 505           counters->update_promoted(promoted);
 506           counters->update_survivor_overflowed(_survivor_overflow);
 507         }
 508 
 509         size_t max_young_size = young_gen->max_size();
 510 
 511         // Deciding a free ratio in the young generation is tricky, so if
 512         // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
 513         // that the old generation size may have been limited because of them) we
 514         // should then limit our young generation size using NewRatio to have it
 515         // follow the old generation size.
 516         if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
 517           max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
 518         }
 519 
 520         size_t survivor_limit =
 521           size_policy->max_survivor_size(max_young_size);
 522         _tenuring_threshold =
 523           size_policy->compute_survivor_space_size_and_threshold(
 524                                                            _survivor_overflow,
 525                                                            _tenuring_threshold,
 526                                                            survivor_limit);
 527 
 528        log_debug(gc, age)("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max threshold " UINTX_FORMAT ")",
 529                           size_policy->calculated_survivor_size_in_bytes(),
 530                           _tenuring_threshold, MaxTenuringThreshold);
 531 
 532         if (UsePerfData) {
 533           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 534           counters->update_tenuring_threshold(_tenuring_threshold);
 535           counters->update_survivor_size_counters();
 536         }
 537 
 538         // Do call at minor collections?
 539         // Don't check if the size_policy is ready at this
 540         // level.  Let the size_policy check that internally.
 541         if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
 542             (AdaptiveSizePolicy::should_update_eden_stats(gc_cause))) {
 543           // Calculate optimal free space amounts
 544           assert(young_gen->max_size() >
 545             young_gen->from_space()->capacity_in_bytes() +
 546             young_gen->to_space()->capacity_in_bytes(),
 547             "Sizes of space in young gen are out-of-bounds");
 548 
 549           size_t young_live = young_gen->used_in_bytes();
 550           size_t eden_live = young_gen->eden_space()->used_in_bytes();
 551           size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
 552           size_t max_old_gen_size = old_gen->max_gen_size();
 553           size_t max_eden_size = max_young_size -
 554             young_gen->from_space()->capacity_in_bytes() -
 555             young_gen->to_space()->capacity_in_bytes();
 556 
 557           // Used for diagnostics
 558           size_policy->clear_generation_free_space_flags();
 559 
 560           size_policy->compute_eden_space_size(young_live,
 561                                                eden_live,
 562                                                cur_eden,
 563                                                max_eden_size,
 564                                                false /* not full gc*/);
 565 
 566           size_policy->check_gc_overhead_limit(young_live,
 567                                                eden_live,
 568                                                max_old_gen_size,
 569                                                max_eden_size,
 570                                                false /* not full gc*/,
 571                                                gc_cause,
 572                                                heap->soft_ref_policy());
 573 
 574           size_policy->decay_supplemental_growth(false /* not full gc*/);
 575         }
 576         // Resize the young generation at every collection
 577         // even if new sizes have not been calculated.  This is
 578         // to allow resizes that may have been inhibited by the
 579         // relative location of the "to" and "from" spaces.
 580 
 581         // Resizing the old gen at young collections can cause increases
 582         // that don't feed back to the generation sizing policy until
 583         // a full collection.  Don't resize the old gen here.
 584 
 585         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
 586                         size_policy->calculated_survivor_size_in_bytes());
 587 
 588         log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
 589       }
 590 
 591       // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
 592       // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
 593       // Also update() will case adaptive NUMA chunk resizing.
 594       assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
 595       young_gen->eden_space()->update();
 596 
 597       heap->gc_policy_counters()->update_counters();
 598 
 599       heap->resize_all_tlabs();
 600 
 601       assert(young_gen->to_space()->is_empty(), "to space should be empty now");
 602     }
 603 
 604 #if COMPILER2_OR_JVMCI
 605     DerivedPointerTable::update_pointers();
 606 #endif
 607 
 608     NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
 609 
 610     // Re-verify object start arrays
 611     if (VerifyObjectStartArray &&
 612         VerifyAfterGC) {
 613       old_gen->verify_object_start_array();
 614     }
 615 
 616     // Verify all old -> young cards are now precise
 617     if (VerifyRememberedSets) {
 618       // Precise verification will give false positives. Until this is fixed,
 619       // use imprecise verification.
 620       // heap->card_table()->verify_all_young_refs_precise();
 621       heap->card_table()->verify_all_young_refs_imprecise();
 622     }
 623 
 624     if (log_is_enabled(Debug, gc, heap, exit)) {
 625       accumulated_time()->stop();
 626     }
 627 
 628     young_gen->print_used_change(pre_gc_values.young_gen_used());
 629     old_gen->print_used_change(pre_gc_values.old_gen_used());
 630     MetaspaceUtils::print_metaspace_change(pre_gc_values.metadata_used());
 631 
 632     // Track memory usage and detect low memory
 633     MemoryService::track_memory_usage();
 634     heap->update_counters();
 635 
 636     gc_task_manager()->release_idle_workers();
 637   }
 638 
 639   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 640     HandleMark hm;  // Discard invalid handles created during verification
 641     Universe::verify("After GC");
 642   }
 643 
 644   heap->print_heap_after_gc();
 645   heap->trace_heap_after_gc(&_gc_tracer);
 646 
 647   scavenge_exit.update();
 648 
 649   log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
 650                             scavenge_entry.ticks(), scavenge_midpoint.ticks(),
 651                             scavenge_exit.ticks());
 652   gc_task_manager()->print_task_time_stamps();
 653 
 654 #ifdef TRACESPINNING
 655   ParallelTaskTerminator::print_termination_counts();
 656 #endif
 657 
 658   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
 659 
 660   _gc_timer.register_gc_end();
 661 
 662   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
 663 
 664   return !promotion_failure_occurred;
 665 }
 666 
 667 // This method iterates over all objects in the young generation,
 668 // removing all forwarding references. It then restores any preserved marks.
 669 void PSScavenge::clean_up_failed_promotion() {
 670   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 671   PSYoungGen* young_gen = heap->young_gen();
 672 
 673   RemoveForwardedPointerClosure remove_fwd_ptr_closure;
 674   young_gen->object_iterate(&remove_fwd_ptr_closure);
 675 
 676   PSPromotionManager::restore_preserved_marks();
 677 
 678   // Reset the PromotionFailureALot counters.
 679   NOT_PRODUCT(heap->reset_promotion_should_fail();)
 680 }
 681 
 682 bool PSScavenge::should_attempt_scavenge() {
 683   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 684   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 685 
 686   if (UsePerfData) {
 687     counters->update_scavenge_skipped(not_skipped);
 688   }
 689 
 690   PSYoungGen* young_gen = heap->young_gen();
 691   PSOldGen* old_gen = heap->old_gen();
 692 
 693   // Do not attempt to promote unless to_space is empty
 694   if (!young_gen->to_space()->is_empty()) {
 695     _consecutive_skipped_scavenges++;
 696     if (UsePerfData) {
 697       counters->update_scavenge_skipped(to_space_not_empty);
 698     }
 699     return false;
 700   }
 701 
 702   // Test to see if the scavenge will likely fail.
 703   PSAdaptiveSizePolicy* policy = heap->size_policy();
 704 
 705   // A similar test is done in the policy's should_full_GC().  If this is
 706   // changed, decide if that test should also be changed.
 707   size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
 708   size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
 709   bool result = promotion_estimate < old_gen->free_in_bytes();
 710 
 711   log_trace(ergo)("%s scavenge: average_promoted " SIZE_FORMAT " padded_average_promoted " SIZE_FORMAT " free in old gen " SIZE_FORMAT,
 712                 result ? "Do" : "Skip", (size_t) policy->average_promoted_in_bytes(),
 713                 (size_t) policy->padded_average_promoted_in_bytes(),
 714                 old_gen->free_in_bytes());
 715   if (young_gen->used_in_bytes() < (size_t) policy->padded_average_promoted_in_bytes()) {
 716     log_trace(ergo)(" padded_promoted_average is greater than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
 717   }
 718 
 719   if (result) {
 720     _consecutive_skipped_scavenges = 0;
 721   } else {
 722     _consecutive_skipped_scavenges++;
 723     if (UsePerfData) {
 724       counters->update_scavenge_skipped(promoted_too_large);
 725     }
 726   }
 727   return result;
 728 }
 729 
 730   // Used to add tasks
 731 GCTaskManager* const PSScavenge::gc_task_manager() {
 732   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
 733    "shouldn't return NULL");
 734   return ParallelScavengeHeap::gc_task_manager();
 735 }
 736 
 737 // Adaptive size policy support.  When the young generation/old generation
 738 // boundary moves, _young_generation_boundary must be reset
 739 void PSScavenge::set_young_generation_boundary(HeapWord* v) {
 740   _young_generation_boundary = v;
 741   if (UseCompressedOops) {
 742     _young_generation_boundary_compressed = (uintptr_t)CompressedOops::encode((oop)v);
 743   }
 744 }
 745 
 746 void PSScavenge::initialize() {
 747   // Arguments must have been parsed
 748 
 749   if (AlwaysTenure || NeverTenure) {
 750     assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
 751            "MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold);
 752     _tenuring_threshold = MaxTenuringThreshold;
 753   } else {
 754     // We want to smooth out our startup times for the AdaptiveSizePolicy
 755     _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
 756                                                     MaxTenuringThreshold;
 757   }
 758 
 759   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 760   PSYoungGen* young_gen = heap->young_gen();
 761   PSOldGen* old_gen = heap->old_gen();
 762 
 763   // Set boundary between young_gen and old_gen
 764   assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
 765          "old above young");
 766   set_young_generation_boundary(young_gen->eden_space()->bottom());
 767 
 768   // Initialize ref handling object for scavenging.
 769   MemRegion mr = young_gen->reserved();
 770 
 771   _ref_processor =
 772     new ReferenceProcessor(mr,                         // span
 773                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 774                            ParallelGCThreads,          // mt processing degree
 775                            true,                       // mt discovery
 776                            ParallelGCThreads,          // mt discovery degree
 777                            true,                       // atomic_discovery
 778                            NULL);                      // header provides liveness info
 779 
 780   // Cache the cardtable
 781   _card_table = heap->card_table();
 782 
 783   _counters = new CollectorCounters("PSScavenge", 0);
 784 }