예제 #1
0
// This method contains no policy. You should probably
// be calling invoke() instead.
bool PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
  assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
  assert(ref_processor() != NULL, "Sanity");

  if (GC_locker::check_active_before_gc()) {
    return false;
  }

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
  GCCause::Cause gc_cause = heap->gc_cause();

  _gc_timer->register_gc_start();
  _gc_tracer->report_gc_start(gc_cause, _gc_timer->gc_start());

  PSAdaptiveSizePolicy* size_policy = heap->size_policy();

  // The scope of casr should end after code that can change
  // CollectorPolicy::_should_clear_all_soft_refs.
  ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy());

  PSYoungGen* young_gen = heap->young_gen();
  PSOldGen* old_gen = heap->old_gen();
  PSPermGen* perm_gen = heap->perm_gen();

  // Increment the invocation count
  heap->increment_total_collections(true /* full */);

  // Save information needed to minimize mangling
  heap->record_gen_tops_before_GC();

  // We need to track unique mark sweep invocations as well.
  _total_invocations++;

  AdaptiveSizePolicyOutput(size_policy, heap->total_collections());

  heap->print_heap_before_gc();
  heap->trace_heap_before_gc(_gc_tracer);

  // Fill in TLABs
  heap->accumulate_statistics_all_tlabs();
  heap->ensure_parsability(true);  // retire TLABs

  if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
    HandleMark hm;  // Discard invalid handles created during verification
    Universe::verify(" VerifyBeforeGC:");
  }

  // Verify object start arrays
  if (VerifyObjectStartArray &&
      VerifyBeforeGC) {
    old_gen->verify_object_start_array();
    perm_gen->verify_object_start_array();
  }

  heap->pre_full_gc_dump(_gc_timer);

  // Filled in below to track the state of the young gen after the collection.
  bool eden_empty;
  bool survivors_empty;
  bool young_gen_empty;

  {
    HandleMark hm;

    TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
    GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
    TraceCollectorStats tcs(counters());
    TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);

    if (TraceGen1Time) accumulated_time()->start();

    // Let the size policy know we're starting
    size_policy->major_collection_begin();

    // When collecting the permanent generation methodOops may be moving,
    // so we either have to flush all bcp data or convert it into bci.
    CodeCache::gc_prologue();
    Threads::gc_prologue();
    BiasedLocking::preserve_marks();

    // Capture heap size before collection for printing.
    size_t prev_used = heap->used();

    // Capture perm gen size before collection for sizing.
    size_t perm_gen_prev_used = perm_gen->used_in_bytes();

    // For PrintGCDetails
    size_t old_gen_prev_used = old_gen->used_in_bytes();
    size_t young_gen_prev_used = young_gen->used_in_bytes();

    allocate_stacks();

    COMPILER2_PRESENT(DerivedPointerTable::clear());

    ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
    ref_processor()->setup_policy(clear_all_softrefs);

    mark_sweep_phase1(clear_all_softrefs);

    mark_sweep_phase2();

    // Don't add any more derived pointers during phase3
    COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
    COMPILER2_PRESENT(DerivedPointerTable::set_active(false));

    mark_sweep_phase3();

    mark_sweep_phase4();

    restore_marks();

    deallocate_stacks();

    if (ZapUnusedHeapArea) {
      // Do a complete mangle (top to end) because the usage for
      // scratch does not maintain a top pointer.
      young_gen->to_space()->mangle_unused_area_complete();
    }

    eden_empty = young_gen->eden_space()->is_empty();
    if (!eden_empty) {
      eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
    }

    // Update heap occupancy information which is used as
    // input to soft ref clearing policy at the next gc.
    Universe::update_heap_info_at_gc();

    survivors_empty = young_gen->from_space()->is_empty() &&
                      young_gen->to_space()->is_empty();
    young_gen_empty = eden_empty && survivors_empty;

    BarrierSet* bs = heap->barrier_set();
    if (bs->is_a(BarrierSet::ModRef)) {
      ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
      MemRegion old_mr = heap->old_gen()->reserved();
      MemRegion perm_mr = heap->perm_gen()->reserved();
      assert(perm_mr.end() <= old_mr.start(), "Generations out of order");

      if (young_gen_empty) {
        modBS->clear(MemRegion(perm_mr.start(), old_mr.end()));
      } else {
        modBS->invalidate(MemRegion(perm_mr.start(), old_mr.end()));
      }
    }

    BiasedLocking::restore_marks();
    Threads::gc_epilogue();
    CodeCache::gc_epilogue();
    JvmtiExport::gc_epilogue();

    COMPILER2_PRESENT(DerivedPointerTable::update_pointers());

    ref_processor()->enqueue_discovered_references(NULL);

    // Update time of last GC
    reset_millis_since_last_gc();

    // Let the size policy know we're done
    size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);

    if (UseAdaptiveSizePolicy) {

      if (PrintAdaptiveSizePolicy) {
        gclog_or_tty->print("AdaptiveSizeStart: ");
        gclog_or_tty->stamp();
        gclog_or_tty->print_cr(" collection: %d ",
                       heap->total_collections());
        if (Verbose) {
          gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
            " perm_gen_capacity: %d ",
            old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
            perm_gen->capacity_in_bytes());
        }
      }

      // Don't check if the size_policy is ready here.  Let
      // the size_policy check that internally.
      if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
          ((gc_cause != GCCause::_java_lang_system_gc) ||
            UseAdaptiveSizePolicyWithSystemGC)) {
        // Calculate optimal free space amounts
        assert(young_gen->max_size() >
          young_gen->from_space()->capacity_in_bytes() +
          young_gen->to_space()->capacity_in_bytes(),
          "Sizes of space in young gen are out-of-bounds");
        size_t max_eden_size = young_gen->max_size() -
          young_gen->from_space()->capacity_in_bytes() -
          young_gen->to_space()->capacity_in_bytes();
        size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
                                 young_gen->eden_space()->used_in_bytes(),
                                 old_gen->used_in_bytes(),
                                 perm_gen->used_in_bytes(),
                                 young_gen->eden_space()->capacity_in_bytes(),
                                 old_gen->max_gen_size(),
                                 max_eden_size,
                                 true /* full gc*/,
                                 gc_cause,
                                 heap->collector_policy());

        heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());

        // Don't resize the young generation at an major collection.  A
        // desired young generation size may have been calculated but
        // resizing the young generation complicates the code because the
        // resizing of the old generation may have moved the boundary
        // between the young generation and the old generation.  Let the
        // young generation resizing happen at the minor collections.
      }
      if (PrintAdaptiveSizePolicy) {
        gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
                       heap->total_collections());
      }
    }

    if (UsePerfData) {
      heap->gc_policy_counters()->update_counters();
      heap->gc_policy_counters()->update_old_capacity(
        old_gen->capacity_in_bytes());
      heap->gc_policy_counters()->update_young_capacity(
        young_gen->capacity_in_bytes());
    }

    heap->resize_all_tlabs();

    // We collected the perm gen, so we'll resize it here.
    perm_gen->compute_new_size(perm_gen_prev_used);

    if (TraceGen1Time) accumulated_time()->stop();

    if (PrintGC) {
      if (PrintGCDetails) {
        // Don't print a GC timestamp here.  This is after the GC so
        // would be confusing.
        young_gen->print_used_change(young_gen_prev_used);
        old_gen->print_used_change(old_gen_prev_used);
      }
      heap->print_heap_change(prev_used);
      // Do perm gen after heap becase prev_used does
      // not include the perm gen (done this way in the other
      // collectors).
      if (PrintGCDetails) {
        perm_gen->print_used_change(perm_gen_prev_used);
      }
    }

    // Track memory usage and detect low memory
    MemoryService::track_memory_usage();
    heap->update_counters();
  }

  if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
    HandleMark hm;  // Discard invalid handles created during verification
    Universe::verify(" VerifyAfterGC:");
  }

  // Re-verify object start arrays
  if (VerifyObjectStartArray &&
      VerifyAfterGC) {
    old_gen->verify_object_start_array();
    perm_gen->verify_object_start_array();
  }

  if (ZapUnusedHeapArea) {
    old_gen->object_space()->check_mangled_unused_area_complete();
    perm_gen->object_space()->check_mangled_unused_area_complete();
  }

  NOT_PRODUCT(ref_processor()->verify_no_references_recorded());

  heap->print_heap_after_gc();
  heap->trace_heap_after_gc(_gc_tracer);

  heap->post_full_gc_dump(_gc_timer);

#ifdef TRACESPINNING
  ParallelTaskTerminator::print_termination_counts();
#endif

  _gc_timer->register_gc_end();

  _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());

  return true;
}
예제 #2
0
// This method contains no policy. You should probably
// be calling invoke() instead.
bool PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
  assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
  assert(ref_processor() != NULL, "Sanity");

  if (GC_locker::check_active_before_gc()) {
    return false;
  }

  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
  GCCause::Cause gc_cause = heap->gc_cause();

  _gc_timer->register_gc_start();
  _gc_tracer->report_gc_start(gc_cause, _gc_timer->gc_start());

  PSAdaptiveSizePolicy* size_policy = heap->size_policy();

  // The scope of casr should end after code that can change
  // CollectorPolicy::_should_clear_all_soft_refs.
  ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy());

  PSYoungGen* young_gen = heap->young_gen();
  PSOldGen* old_gen = heap->old_gen();

  // Increment the invocation count
  heap->increment_total_collections(true /* full */);

  // Save information needed to minimize mangling
  heap->record_gen_tops_before_GC();

  // We need to track unique mark sweep invocations as well.
  _total_invocations++;

  AdaptiveSizePolicyOutput(size_policy, heap->total_collections());

  heap->print_heap_before_gc();
  heap->trace_heap_before_gc(_gc_tracer);

  // Fill in TLABs
  heap->accumulate_statistics_all_tlabs();
  heap->ensure_parsability(true);  // retire TLABs

  if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
    HandleMark hm;  // Discard invalid handles created during verification
    Universe::verify(" VerifyBeforeGC:");
  }

  // Verify object start arrays
  if (VerifyObjectStartArray &&
      VerifyBeforeGC) {
    old_gen->verify_object_start_array();
  }

  heap->pre_full_gc_dump(_gc_timer);

  // Filled in below to track the state of the young gen after the collection.
  bool eden_empty;
  bool survivors_empty;
  bool young_gen_empty;

  {
    HandleMark hm;

    TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
    GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer->gc_id());
    TraceCollectorStats tcs(counters());
    TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);

    if (TraceOldGenTime) accumulated_time()->start();

    // Let the size policy know we're starting
    size_policy->major_collection_begin();

    CodeCache::gc_prologue();
    BiasedLocking::preserve_marks();

    // Capture heap size before collection for printing.
    size_t prev_used = heap->used();

    // Capture metadata size before collection for sizing.
    size_t metadata_prev_used = MetaspaceAux::used_bytes();

    // For PrintGCDetails
    size_t old_gen_prev_used = old_gen->used_in_bytes();
    size_t young_gen_prev_used = young_gen->used_in_bytes();

    allocate_stacks();

    COMPILER2_PRESENT(DerivedPointerTable::clear());

    ref_processor()->enable_discovery();
    ref_processor()->setup_policy(clear_all_softrefs);

    mark_sweep_phase1(clear_all_softrefs);

    mark_sweep_phase2();

    // Don't add any more derived pointers during phase3
    COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
    COMPILER2_PRESENT(DerivedPointerTable::set_active(false));

    mark_sweep_phase3();

    mark_sweep_phase4();

    restore_marks();

    deallocate_stacks();

    if (ZapUnusedHeapArea) {
      // Do a complete mangle (top to end) because the usage for
      // scratch does not maintain a top pointer.
      young_gen->to_space()->mangle_unused_area_complete();
    }

    eden_empty = young_gen->eden_space()->is_empty();
    if (!eden_empty) {
      eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
    }

    // Update heap occupancy information which is used as
    // input to soft ref clearing policy at the next gc.
    Universe::update_heap_info_at_gc();

    survivors_empty = young_gen->from_space()->is_empty() &&
                      young_gen->to_space()->is_empty();
    young_gen_empty = eden_empty && survivors_empty;

    ModRefBarrierSet* modBS = barrier_set_cast<ModRefBarrierSet>(heap->barrier_set());
    MemRegion old_mr = heap->old_gen()->reserved();
    if (young_gen_empty) {
      modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
    } else {
      modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
    }

    // Delete metaspaces for unloaded class loaders and clean up loader_data graph
    ClassLoaderDataGraph::purge();
    MetaspaceAux::verify_metrics();

    BiasedLocking::restore_marks();
    CodeCache::gc_epilogue();
    JvmtiExport::gc_epilogue();

    COMPILER2_PRESENT(DerivedPointerTable::update_pointers());

    ref_processor()->enqueue_discovered_references(NULL);

    // Update time of last GC
    reset_millis_since_last_gc();

    // Let the size policy know we're done
    size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);

    if (UseAdaptiveSizePolicy) {

      if (PrintAdaptiveSizePolicy) {
        gclog_or_tty->print("AdaptiveSizeStart: ");
        gclog_or_tty->stamp();
        gclog_or_tty->print_cr(" collection: %d ",
                       heap->total_collections());
        if (Verbose) {
          gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT
            " young_gen_capacity: " SIZE_FORMAT,
            old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
        }
      }

      // Don't check if the size_policy is ready here.  Let
      // the size_policy check that internally.
      if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
          ((gc_cause != GCCause::_java_lang_system_gc) ||
            UseAdaptiveSizePolicyWithSystemGC)) {
        // Swap the survivor spaces if from_space is empty. The
        // resize_young_gen() called below is normally used after
        // a successful young GC and swapping of survivor spaces;
        // otherwise, it will fail to resize the young gen with
        // the current implementation.
        if (young_gen->from_space()->is_empty()) {
          young_gen->from_space()->clear(SpaceDecorator::Mangle);
          young_gen->swap_spaces();
        }

        // Calculate optimal free space amounts
        assert(young_gen->max_size() >
          young_gen->from_space()->capacity_in_bytes() +
          young_gen->to_space()->capacity_in_bytes(),
          "Sizes of space in young gen are out-of-bounds");

        size_t young_live = young_gen->used_in_bytes();
        size_t eden_live = young_gen->eden_space()->used_in_bytes();
        size_t old_live = old_gen->used_in_bytes();
        size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
        size_t max_old_gen_size = old_gen->max_gen_size();
        size_t max_eden_size = young_gen->max_size() -
          young_gen->from_space()->capacity_in_bytes() -
          young_gen->to_space()->capacity_in_bytes();

        // Used for diagnostics
        size_policy->clear_generation_free_space_flags();

        size_policy->compute_generations_free_space(young_live,
                                                    eden_live,
                                                    old_live,
                                                    cur_eden,
                                                    max_old_gen_size,
                                                    max_eden_size,
                                                    true /* full gc*/);

        size_policy->check_gc_overhead_limit(young_live,
                                             eden_live,
                                             max_old_gen_size,
                                             max_eden_size,
                                             true /* full gc*/,
                                             gc_cause,
                                             heap->collector_policy());

        size_policy->decay_supplemental_growth(true /* full gc*/);

        heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());

        heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
                               size_policy->calculated_survivor_size_in_bytes());
      }
      if (PrintAdaptiveSizePolicy) {
        gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
                       heap->total_collections());
      }
    }

    if (UsePerfData) {
      heap->gc_policy_counters()->update_counters();
      heap->gc_policy_counters()->update_old_capacity(
        old_gen->capacity_in_bytes());
      heap->gc_policy_counters()->update_young_capacity(
        young_gen->capacity_in_bytes());
    }

    heap->resize_all_tlabs();

    // We collected the heap, recalculate the metaspace capacity
    MetaspaceGC::compute_new_size();

    if (TraceOldGenTime) accumulated_time()->stop();

    if (PrintGC) {
      if (PrintGCDetails) {
        // Don't print a GC timestamp here.  This is after the GC so
        // would be confusing.
        young_gen->print_used_change(young_gen_prev_used);
        old_gen->print_used_change(old_gen_prev_used);
      }
      heap->print_heap_change(prev_used);
      if (PrintGCDetails) {
        MetaspaceAux::print_metaspace_change(metadata_prev_used);
      }
    }

    // Track memory usage and detect low memory
    MemoryService::track_memory_usage();
    heap->update_counters();
  }

  if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
    HandleMark hm;  // Discard invalid handles created during verification
    Universe::verify(" VerifyAfterGC:");
  }

  // Re-verify object start arrays
  if (VerifyObjectStartArray &&
      VerifyAfterGC) {
    old_gen->verify_object_start_array();
  }

  if (ZapUnusedHeapArea) {
    old_gen->object_space()->check_mangled_unused_area_complete();
  }

  NOT_PRODUCT(ref_processor()->verify_no_references_recorded());

  heap->print_heap_after_gc();
  heap->trace_heap_after_gc(_gc_tracer);

  heap->post_full_gc_dump(_gc_timer);

#ifdef TRACESPINNING
  ParallelTaskTerminator::print_termination_counts();
#endif

  _gc_timer->register_gc_end();

  _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());

  return true;
}
// This method contains no policy. You should probably
// be calling invoke() instead.
bool PSScavenge::invoke_no_policy() {
  assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
  assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");

  assert(_preserved_mark_stack.is_empty(), "should be empty");
  assert(_preserved_oop_stack.is_empty(), "should be empty");

  _gc_timer.register_gc_start();

  TimeStamp scavenge_entry;
  TimeStamp scavenge_midpoint;
  TimeStamp scavenge_exit;

  scavenge_entry.update();

  if (GC_locker::check_active_before_gc()) {
    return false;
  }

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  GCCause::Cause gc_cause = heap->gc_cause();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

  // Check for potential problems.
  if (!should_attempt_scavenge()) {
    return false;
  }

  _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());

  bool promotion_failure_occurred = false;

  PSYoungGen* young_gen = heap->young_gen();
  PSOldGen* old_gen = heap->old_gen();
  PSAdaptiveSizePolicy* size_policy = heap->size_policy();

  heap->increment_total_collections();

  AdaptiveSizePolicyOutput(size_policy, heap->total_collections());

  if ((gc_cause != GCCause::_java_lang_system_gc) ||
       UseAdaptiveSizePolicyWithSystemGC) {
    // Gather the feedback data for eden occupancy.
    young_gen->eden_space()->accumulate_statistics();
  }

  if (ZapUnusedHeapArea) {
    // Save information needed to minimize mangling
    heap->record_gen_tops_before_GC();
  }

  heap->print_heap_before_gc();
  heap->trace_heap_before_gc(&_gc_tracer);

  assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
  assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");

  size_t prev_used = heap->used();

  // Fill in TLABs
  heap->accumulate_statistics_all_tlabs();
  heap->ensure_parsability(true);  // retire TLABs

  if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
    HandleMark hm;  // Discard invalid handles created during verification
    Universe::verify(" VerifyBeforeGC:");
  }

  {
    ResourceMark rm;
    HandleMark hm;

    gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
    TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
    GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
    TraceCollectorStats tcs(counters());
    TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);

    if (TraceGen0Time) accumulated_time()->start();

    // Let the size policy know we're starting
    size_policy->minor_collection_begin();

    // Verify the object start arrays.
    if (VerifyObjectStartArray &&
        VerifyBeforeGC) {
      old_gen->verify_object_start_array();
    }

    // Verify no unmarked old->young roots
    if (VerifyRememberedSets) {
      CardTableExtension::verify_all_young_refs_imprecise();
    }

    if (!ScavengeWithObjectsInToSpace) {
      assert(young_gen->to_space()->is_empty(),
             "Attempt to scavenge with live objects in to_space");
      young_gen->to_space()->clear(SpaceDecorator::Mangle);
    } else if (ZapUnusedHeapArea) {
      young_gen->to_space()->mangle_unused_area();
    }
    save_to_space_top_before_gc();

    COMPILER2_PRESENT(DerivedPointerTable::clear());

    reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
    reference_processor()->setup_policy(false);

    // We track how much was promoted to the next generation for
    // the AdaptiveSizePolicy.
    size_t old_gen_used_before = old_gen->used_in_bytes();

    // For PrintGCDetails
    size_t young_gen_used_before = young_gen->used_in_bytes();

    // Reset our survivor overflow.
    set_survivor_overflow(false);

    // We need to save the old top values before
    // creating the promotion_manager. We pass the top
    // values to the card_table, to prevent it from
    // straying into the promotion labs.
    HeapWord* old_top = old_gen->object_space()->top();

    // Release all previously held resources
    gc_task_manager()->release_all_resources();

    // Set the number of GC threads to be used in this collection
    gc_task_manager()->set_active_gang();
    gc_task_manager()->task_idle_workers();
    // Get the active number of workers here and use that value
    // throughout the methods.
    uint active_workers = gc_task_manager()->active_workers();
    heap->set_par_threads(active_workers);

    PSPromotionManager::pre_scavenge();

    // We'll use the promotion manager again later.
    PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
    {
      GCTraceTime tm("Scavenge", false, false, &_gc_timer);
      ParallelScavengeHeap::ParStrongRootsScope psrs;

      GCTaskQueue* q = GCTaskQueue::create();

      if (!old_gen->object_space()->is_empty()) {
        // There are only old-to-young pointers if there are objects
        // in the old gen.
        uint stripe_total = active_workers;
        for(uint i=0; i < stripe_total; i++) {
          q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
        }
      }

      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
      // We scan the thread roots in parallel
      Threads::create_thread_roots_tasks(q);
      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
      q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));

      ParallelTaskTerminator terminator(
        active_workers,
                  (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
      if (active_workers > 1) {
        for (uint j = 0; j < active_workers; j++) {
          q->enqueue(new StealTask(&terminator));
        }
      }

      gc_task_manager()->execute_and_wait(q);
    }

    scavenge_midpoint.update();

    // Process reference objects discovered during scavenge
    {
      GCTraceTime tm("References", false, false, &_gc_timer);

      reference_processor()->setup_policy(false); // not always_clear
      reference_processor()->set_active_mt_degree(active_workers);
      PSKeepAliveClosure keep_alive(promotion_manager);
      PSEvacuateFollowersClosure evac_followers(promotion_manager);
      ReferenceProcessorStats stats;
      if (reference_processor()->processing_is_mt()) {
        PSRefProcTaskExecutor task_executor;
        stats = reference_processor()->process_discovered_references(
          &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
          &_gc_timer);
      } else {
        stats = reference_processor()->process_discovered_references(
          &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer);
      }

      _gc_tracer.report_gc_reference_stats(stats);

      // Enqueue reference objects discovered during scavenge.
      if (reference_processor()->processing_is_mt()) {
        PSRefProcTaskExecutor task_executor;
        reference_processor()->enqueue_discovered_references(&task_executor);
      } else {
        reference_processor()->enqueue_discovered_references(NULL);
      }
    }

    {
      GCTraceTime tm("StringTable", false, false, &_gc_timer);
      // Unlink any dead interned Strings and process the remaining live ones.
      PSScavengeRootsClosure root_closure(promotion_manager);
      StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
    }

    // Finally, flush the promotion_manager's labs, and deallocate its stacks.
    promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
    if (promotion_failure_occurred) {
      clean_up_failed_promotion();
      if (PrintGC) {
        gclog_or_tty->print("--");
      }
    }

    // Let the size policy know we're done.  Note that we count promotion
    // failure cleanup time as part of the collection (otherwise, we're
    // implicitly saying it's mutator time).
    size_policy->minor_collection_end(gc_cause);

    if (!promotion_failure_occurred) {
      // Swap the survivor spaces.
      young_gen->eden_space()->clear(SpaceDecorator::Mangle);
      young_gen->from_space()->clear(SpaceDecorator::Mangle);
      young_gen->swap_spaces();

      size_t survived = young_gen->from_space()->used_in_bytes();
      size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
      size_policy->update_averages(_survivor_overflow, survived, promoted);

      // A successful scavenge should restart the GC time limit count which is
      // for full GC's.
      size_policy->reset_gc_overhead_limit_count();
      if (UseAdaptiveSizePolicy) {
        // Calculate the new survivor size and tenuring threshold

        if (PrintAdaptiveSizePolicy) {
          gclog_or_tty->print("AdaptiveSizeStart: ");
          gclog_or_tty->stamp();
          gclog_or_tty->print_cr(" collection: %d ",
                         heap->total_collections());

          if (Verbose) {
            gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
              old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
          }
        }


        if (UsePerfData) {
          PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
          counters->update_old_eden_size(
            size_policy->calculated_eden_size_in_bytes());
          counters->update_old_promo_size(
            size_policy->calculated_promo_size_in_bytes());
          counters->update_old_capacity(old_gen->capacity_in_bytes());
          counters->update_young_capacity(young_gen->capacity_in_bytes());
          counters->update_survived(survived);
          counters->update_promoted(promoted);
          counters->update_survivor_overflowed(_survivor_overflow);
        }

        size_t max_young_size = young_gen->max_size();

        // Deciding a free ratio in the young generation is tricky, so if
        // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
        // that the old generation size may have been limited because of them) we
        // should then limit our young generation size using NewRatio to have it
        // follow the old generation size.
        if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
          max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
        }

        size_t survivor_limit =
          size_policy->max_survivor_size(max_young_size);
        _tenuring_threshold =
          size_policy->compute_survivor_space_size_and_threshold(
                                                           _survivor_overflow,
                                                           _tenuring_threshold,
                                                           survivor_limit);

       if (PrintTenuringDistribution) {
         gclog_or_tty->cr();
         gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max %u)",
                                size_policy->calculated_survivor_size_in_bytes(),
                                _tenuring_threshold, MaxTenuringThreshold);
       }

        if (UsePerfData) {
          PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
          counters->update_tenuring_threshold(_tenuring_threshold);
          counters->update_survivor_size_counters();
        }

        // Do call at minor collections?
        // Don't check if the size_policy is ready at this
        // level.  Let the size_policy check that internally.
        if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
            ((gc_cause != GCCause::_java_lang_system_gc) ||
              UseAdaptiveSizePolicyWithSystemGC)) {

          // Calculate optimial free space amounts
          assert(young_gen->max_size() >
            young_gen->from_space()->capacity_in_bytes() +
            young_gen->to_space()->capacity_in_bytes(),
            "Sizes of space in young gen are out-of-bounds");

          size_t young_live = young_gen->used_in_bytes();
          size_t eden_live = young_gen->eden_space()->used_in_bytes();
          size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
          size_t max_old_gen_size = old_gen->max_gen_size();
          size_t max_eden_size = max_young_size -
            young_gen->from_space()->capacity_in_bytes() -
            young_gen->to_space()->capacity_in_bytes();

          // Used for diagnostics
          size_policy->clear_generation_free_space_flags();

          size_policy->compute_eden_space_size(young_live,
                                               eden_live,
                                               cur_eden,
                                               max_eden_size,
                                               false /* not full gc*/);

          size_policy->check_gc_overhead_limit(young_live,
                                               eden_live,
                                               max_old_gen_size,
                                               max_eden_size,
                                               false /* not full gc*/,
                                               gc_cause,
                                               heap->collector_policy());

          size_policy->decay_supplemental_growth(false /* not full gc*/);
        }
        // Resize the young generation at every collection
        // even if new sizes have not been calculated.  This is
        // to allow resizes that may have been inhibited by the
        // relative location of the "to" and "from" spaces.

        // Resizing the old gen at minor collects can cause increases
        // that don't feed back to the generation sizing policy until
        // a major collection.  Don't resize the old gen here.

        heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
                        size_policy->calculated_survivor_size_in_bytes());

        if (PrintAdaptiveSizePolicy) {
          gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
                         heap->total_collections());
        }
      }

      // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
      // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
      // Also update() will case adaptive NUMA chunk resizing.
      assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
      young_gen->eden_space()->update();

      heap->gc_policy_counters()->update_counters();

      heap->resize_all_tlabs();

      assert(young_gen->to_space()->is_empty(), "to space should be empty now");
    }

    COMPILER2_PRESENT(DerivedPointerTable::update_pointers());

    NOT_PRODUCT(reference_processor()->verify_no_references_recorded());

    {
      GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer);

      CodeCache::prune_scavenge_root_nmethods();
    }

    // Re-verify object start arrays
    if (VerifyObjectStartArray &&
        VerifyAfterGC) {
      old_gen->verify_object_start_array();
    }

    // Verify all old -> young cards are now precise
    if (VerifyRememberedSets) {
      // Precise verification will give false positives. Until this is fixed,
      // use imprecise verification.
      // CardTableExtension::verify_all_young_refs_precise();
      CardTableExtension::verify_all_young_refs_imprecise();
    }

    if (TraceGen0Time) accumulated_time()->stop();

    if (PrintGC) {
      if (PrintGCDetails) {
        // Don't print a GC timestamp here.  This is after the GC so
        // would be confusing.
        young_gen->print_used_change(young_gen_used_before);
      }
      heap->print_heap_change(prev_used);
    }

    // Track memory usage and detect low memory
    MemoryService::track_memory_usage();
    heap->update_counters();

    gc_task_manager()->release_idle_workers();
  }

  if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
    HandleMark hm;  // Discard invalid handles created during verification
    Universe::verify(" VerifyAfterGC:");
  }

  heap->print_heap_after_gc();
  heap->trace_heap_after_gc(&_gc_tracer);
  _gc_tracer.report_tenuring_threshold(tenuring_threshold());

  if (ZapUnusedHeapArea) {
    young_gen->eden_space()->check_mangled_unused_area_complete();
    young_gen->from_space()->check_mangled_unused_area_complete();
    young_gen->to_space()->check_mangled_unused_area_complete();
  }

  scavenge_exit.update();

  if (PrintGCTaskTimeStamps) {
    tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
                  scavenge_entry.ticks(), scavenge_midpoint.ticks(),
                  scavenge_exit.ticks());
    gc_task_manager()->print_task_time_stamps();
  }

#ifdef TRACESPINNING
  ParallelTaskTerminator::print_termination_counts();
#endif


  _gc_timer.register_gc_end();

  _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());

  return !promotion_failure_occurred;
}