C++ ParallelScavengeHeap::total_collections方法代码示例

void PSOldGen::resize(size_t desired_free_space) {
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
  const size_t alignment = heap->min_alignment();

  const size_t size_before = _virtual_space.committed_size();
  size_t new_size = used_in_bytes() + desired_free_space;
  new_size = align_size_up(new_size, alignment);

  assert(_max_gen_size == reserved().byte_size(), "max new size problem?");

  // Adjust according to our min and max
  new_size = MAX2(MIN2(new_size, _max_gen_size), _min_gen_size);

  const size_t current_size = capacity_in_bytes();
  if (new_size == current_size) {
    // No change requested
    return;
  }
  if (new_size > current_size) {
    size_t change_bytes = new_size - current_size;
    expand(change_bytes);
  } else {
    size_t change_bytes = current_size - new_size;
    // shrink doesn't grab this lock, expand does. Is that right?
    MutexLocker x(ExpandHeap_lock);
    shrink(change_bytes);
  }

  if (PrintAdaptiveSizePolicy) {
    gclog_or_tty->print_cr("AdaptiveSizePolicy::old generation size: "
                  "collection: %d "
                  "(" SIZE_FORMAT ") -> (" SIZE_FORMAT ") ",
                  heap->total_collections(),
                  size_before, _virtual_space.committed_size());
  }
}

// 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");

elapsedTimer scavenge_time;

  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;
  }

  bool promotion_failure_occurred = false;

  PSYoungGen* young_gen = heap->young_gen();
  PSOldGen* old_gen = heap->old_gen();
  PSPermGen* perm_gen = heap->perm_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();
  }
  // We need to track unique scavenge invocations as well.
  _total_invocations++;

  if (PrintHeapAtGC) {
    Universe::print_heap_before_gc();
  }

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

  size_t prev_used = heap->used();
  assert(promotion_failed() == false, "Sanity");

  // 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
    gclog_or_tty->print(" VerifyBeforeGC:");
    Universe::verify(true);
  }

  {
    ResourceMark rm;
    HandleMark hm;

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

    if (TraceGen0Time) scavenge_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();
      perm_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();
    } else if (ZapUnusedHeapArea) {
      young_gen->to_space()->mangle_unused_area();
    }
    save_to_space_top_before_gc();
//.........这里部分代码省略.........

// This method contains no policy. You should probably
// be calling invoke() instead.
void 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;
  }

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

  if (PrintHeapAtGC) {
    Universe::print_heap_before_gc();
  }

  // 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
    gclog_or_tty->print(" VerifyBeforeGC:");
    Universe::verify(true);
  }

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

  heap->pre_full_gc_dump();

  // 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;
    const bool is_system_gc = gc_cause == GCCause::_java_lang_system_gc;
    // This is useful for debugging but don't change the output the
    // the customer sees.
    const char* gc_cause_str = "Full GC";
    if (is_system_gc && PrintGCDetails) {
      gc_cause_str = "Full GC (System)";
    }
    gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
    TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
    TraceTime t1(gc_cause_str, PrintGC, !PrintGCDetails, gclog_or_tty);
    TraceCollectorStats tcs(counters());
    TraceMemoryManagerStats tms(true /* Full GC */);

    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();

    NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
    COMPILER2_PRESENT(DerivedPointerTable::clear());

    ref_processor()->enable_discovery();
//.........这里部分代码省略.........

// 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"));
//.........这里部分代码省略.........

void PSPermGen::compute_new_size(size_t used_before_collection) {
  // Update our padded average of objects allocated in perm
  // gen between collections.
  assert(used_before_collection >= _last_used,
                                "negative allocation amount since last GC?");

  const size_t alloc_since_last_gc = used_before_collection - _last_used;
  _avg_size->sample(alloc_since_last_gc);

  const size_t current_live = used_in_bytes();
  // Stash away the current amount live for the next call to this method.
  _last_used = current_live;

  // We have different alignment constraints than the rest of the heap.
  const size_t alignment = MAX2(MinPermHeapExpansion,
                                virtual_space()->alignment());

  // Compute the desired size:
  //  The free space is the newly computed padded average,
  //  so the desired size is what's live + the free space.
  size_t desired_size = current_live + (size_t)_avg_size->padded_average();
  desired_size = align_size_up(desired_size, alignment);

  // ...and no larger or smaller than our max and min allowed.
  desired_size = MAX2(MIN2(desired_size, _max_gen_size), _min_gen_size);
  assert(desired_size <= _max_gen_size, "just checking");

  const size_t size_before = _virtual_space->committed_size();

  if (desired_size == size_before) {
    // no change, we're done
    return;
  }

  {
    // We'll be growing or shrinking the heap:  in either case,
    // we need to hold a lock.
    MutexLocker x(ExpandHeap_lock);
    if (desired_size > size_before) {
      const size_t change_bytes = desired_size - size_before;
      const size_t aligned_change_bytes =
        align_size_up(change_bytes, alignment);
      expand_by(aligned_change_bytes);
    } else {
      // Shrinking
      const size_t change_bytes =
        size_before - desired_size;
      const size_t aligned_change_bytes = align_size_down(change_bytes, alignment);
      shrink(aligned_change_bytes);
    }
  }

  // While this code isn't controlled by AdaptiveSizePolicy, it's
  // convenient to see all resizing decsions under the same flag.
  if (PrintAdaptiveSizePolicy) {
    ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
    assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

    gclog_or_tty->print_cr("AdaptiveSizePolicy::perm generation size: "
                           "collection: %d "
                           "(" SIZE_FORMAT ") -> (" SIZE_FORMAT ") ",
                           heap->total_collections(),
                           size_before, _virtual_space->committed_size());
  }
}

//.........这里部分代码省略.........
    // Don't let eden shrink down to 0 or less.
    eden_end = MAX2(eden_end, eden_start + alignment);
    to_start = MAX2(to_start, eden_end);

    if (PrintAdaptiveSizePolicy && Verbose) {
      gclog_or_tty->print_cr("    [eden_start .. eden_end): "
                    "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
                    eden_start,
                    eden_end,
                    pointer_delta(eden_end, eden_start, sizeof(char)));
      gclog_or_tty->print_cr("    [  to_start ..   to_end): "
                    "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
                    to_start,
                    to_end,
                    pointer_delta(  to_end,   to_start, sizeof(char)));
      gclog_or_tty->print_cr("    [from_start .. from_end): "
                    "[" PTR_FORMAT " .. " PTR_FORMAT ") " SIZE_FORMAT,
                    from_start,
                    from_end,
                    pointer_delta(from_end, from_start, sizeof(char)));
    }
  }


  guarantee((HeapWord*)from_start <= from_space()->bottom(),
            "from start moved to the right");
  guarantee((HeapWord*)from_end >= from_space()->top(),
            "from end moved into live data");
  assert(is_object_aligned((intptr_t)eden_start), "checking alignment");
  assert(is_object_aligned((intptr_t)from_start), "checking alignment");
  assert(is_object_aligned((intptr_t)to_start), "checking alignment");

  MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)eden_end);
  MemRegion toMR  ((HeapWord*)to_start,   (HeapWord*)to_end);
  MemRegion fromMR((HeapWord*)from_start, (HeapWord*)from_end);

  // Let's make sure the call to initialize doesn't reset "top"!
  HeapWord* old_from_top = from_space()->top();

  // For PrintAdaptiveSizePolicy block  below
  size_t old_from = from_space()->capacity_in_bytes();
  size_t old_to   = to_space()->capacity_in_bytes();

  if (ZapUnusedHeapArea) {
    // NUMA is a special case because a numa space is not mangled
    // in order to not prematurely bind its address to memory to
    // the wrong memory (i.e., don't want the GC thread to first
    // touch the memory).  The survivor spaces are not numa
    // spaces and are mangled.
    if (UseNUMA) {
      if (eden_from_to_order) {
        mangle_survivors(from_space(), fromMR, to_space(), toMR);
      } else {
        mangle_survivors(to_space(), toMR, from_space(), fromMR);
      }
    }

    // If not mangling the spaces, do some checking to verify that
    // the spaces are already mangled.
    // The spaces should be correctly mangled at this point so
    // do some checking here. Note that they are not being mangled
    // in the calls to initialize().
    // Must check mangling before the spaces are reshaped.  Otherwise,
    // the bottom or end of one space may have moved into an area
    // covered by another space and a failure of the check may
    // not correctly indicate which space is not properly mangled.
    HeapWord* limit = (HeapWord*) virtual_space()->high();
    eden_space()->check_mangled_unused_area(limit);
    from_space()->check_mangled_unused_area(limit);
      to_space()->check_mangled_unused_area(limit);
  }
  // When an existing space is being initialized, it is not
  // mangled because the space has been previously mangled.
  eden_space()->initialize(edenMR,
                           SpaceDecorator::Clear,
                           SpaceDecorator::DontMangle);
    to_space()->initialize(toMR,
                           SpaceDecorator::Clear,
                           SpaceDecorator::DontMangle);
  from_space()->initialize(fromMR,
                           SpaceDecorator::DontClear,
                           SpaceDecorator::DontMangle);

  assert(from_space()->top() == old_from_top, "from top changed!");

  if (PrintAdaptiveSizePolicy) {
    ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
    assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

    gclog_or_tty->print("AdaptiveSizePolicy::survivor space sizes: "
                  "collection: %d "
                  "(" SIZE_FORMAT ", " SIZE_FORMAT ") -> "
                  "(" SIZE_FORMAT ", " SIZE_FORMAT ") ",
                  heap->total_collections(),
                  old_from, old_to,
                  from_space()->capacity_in_bytes(),
                  to_space()->capacity_in_bytes());
    gclog_or_tty->cr();
  }
}

// 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);
//.........这里部分代码省略.........

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

    if (GC_locker::is_active()) return;

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

    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();

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

    if (PrintHeapAtGC) {
        gclog_or_tty->print_cr(" {Heap before GC invocations=%d:", heap->total_collections());
        Universe::print();
    }

    // Fill in TLABs
    heap->ensure_parseability();

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

    {
        HandleMark hm;
        TraceTime t1("Full GC", PrintGC, true, gclog_or_tty);
        TraceCollectorStats tcs(counters());
        if (TraceGen1Time) accumulated_time()->start();

        // Let the size policy know we're starting
        AdaptiveSizePolicy* size_policy = heap->size_policy();
        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.
        NOT_CORE(CodeCache::gc_prologue());
        Threads::gc_prologue();

        // 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();

        bool marked_for_unloading = false;

        allocate_stacks();

        NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
        COMPILER2_ONLY(DerivedPointerTable::clear());

        ref_processor()->enable_discovery();

        mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);

        mark_sweep_phase2();

        // Don't add any more derived pointers during phase3
        COMPILER2_ONLY(assert(DerivedPointerTable::is_active(), "Sanity"));
        COMPILER2_ONLY(DerivedPointerTable::set_active(false));

        mark_sweep_phase3();

        mark_sweep_phase4();

        restore_marks();

        deallocate_stacks();

        // "free at last gc" is calculated from these.
        Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
        Universe::set_heap_used_at_last_gc(Universe::heap()->used());

        bool all_empty = young_gen->eden_space()->is_empty() &&
                         young_gen->from_space()->is_empty() &&
                         young_gen->to_space()->is_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(old_mr.end() <= perm_mr.start(), "Generations out of order");

            if (all_empty) {
                modBS->clear(MemRegion(old_mr.start(), perm_mr.end()));
            } else {
                modBS->invalidate(MemRegion(old_mr.start(), perm_mr.end()));
//.........这里部分代码省略.........

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

  TimeStamp scavenge_entry;
  TimeStamp scavenge_midpoint;
  TimeStamp scavenge_exit;

  scavenge_entry.update();

  if (GC_locker::is_active()) return;

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

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

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

  heap->increment_total_collections();

  if (PrintHeapAtGC){
    gclog_or_tty->print_cr(" {Heap before GC invocations=%d:", heap->total_collections());
    Universe::print();
  }

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

  size_t prev_used = heap->used();
  assert(promotion_failed() == false, "Sanity");

  // Fill in TLABs
  heap->ensure_parseability();

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

  {
    ResourceMark rm;
    HandleMark hm;

    TraceTime t1("GC", PrintGC, true, gclog_or_tty);
    TraceCollectorStats tcs(counters());
    if (TraceGen0Time) accumulated_time()->start();

    // Let the size policy know we're starting
    size_policy->minor_collection_begin();
    
    // Verify no unmarked old->young roots
    if (VerifyRememberedSets) {
      old_gen->verify_object_start_array();
      perm_gen->verify_object_start_array();
      CardTableExtension::verify_all_young_refs_imprecise();
    }
    
    assert(young_gen->to_space()->is_empty(), "Attempt to scavenge with live objects in to_space");
    young_gen->to_space()->clear();

    NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
    COMPILER2_ONLY(DerivedPointerTable::clear(););

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

    // Reset our survivor overflow.
    set_survivor_overflow(false);
    
    // We need to save the old/perm 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();
    HeapWord* perm_top = perm_gen->object_space()->top();

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

    PSPromotionManager::pre_scavenge();

    // We'll use the promotion manager again later.
    PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
    {
      // TraceTime("Roots");
      
      GCTaskQueue* q = GCTaskQueue::create();
//.........这里部分代码省略.........