g1CollectedHeap.cpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#include "precompiled.hpp"
#include "classfile/classLoaderDataGraph.hpp"
#include "classfile/metadataOnStackMark.hpp"
#include "classfile/stringTable.hpp"
#include "code/codeCache.hpp"
#include "code/icBuffer.hpp"
#include "compiler/oopMap.hpp"
#include "gc/g1/g1Allocator.inline.hpp"
#include "gc/g1/g1Arguments.hpp"
#include "gc/g1/g1BarrierSet.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1CollectionSet.hpp"
#include "gc/g1/g1CollectionSetCandidates.hpp"
#include "gc/g1/g1CollectorState.hpp"
#include "gc/g1/g1ConcurrentRefine.hpp"
#include "gc/g1/g1ConcurrentRefineThread.hpp"
#include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
#include "gc/g1/g1DirtyCardQueue.hpp"
#include "gc/g1/g1EvacStats.inline.hpp"
#include "gc/g1/g1FullCollector.hpp"
#include "gc/g1/g1GCParPhaseTimesTracker.hpp"
#include "gc/g1/g1GCPhaseTimes.hpp"
#include "gc/g1/g1GCPauseType.hpp"
#include "gc/g1/g1HeapSizingPolicy.hpp"
#include "gc/g1/g1HeapTransition.hpp"
#include "gc/g1/g1HeapVerifier.hpp"
#include "gc/g1/g1HotCardCache.hpp"
#include "gc/g1/g1InitLogger.hpp"
#include "gc/g1/g1MemoryPool.hpp"
#include "gc/g1/g1OopClosures.inline.hpp"
#include "gc/g1/g1ParallelCleaning.hpp"
#include "gc/g1/g1ParScanThreadState.inline.hpp"
#include "gc/g1/g1PeriodicGCTask.hpp"
#include "gc/g1/g1Policy.hpp"
#include "gc/g1/g1RedirtyCardsQueue.hpp"
#include "gc/g1/g1RegionToSpaceMapper.hpp"
#include "gc/g1/g1RemSet.hpp"
#include "gc/g1/g1RootClosures.hpp"
#include "gc/g1/g1RootProcessor.hpp"
#include "gc/g1/g1SATBMarkQueueSet.hpp"
#include "gc/g1/g1ThreadLocalData.hpp"
#include "gc/g1/g1Trace.hpp"
#include "gc/g1/g1ServiceThread.hpp"
#include "gc/g1/g1UncommitRegionTask.hpp"
#include "gc/g1/g1VMOperations.hpp"
#include "gc/g1/g1YoungGCPostEvacuateTasks.hpp"
#include "gc/g1/heapRegion.inline.hpp"
#include "gc/g1/heapRegionRemSet.inline.hpp"
#include "gc/g1/heapRegionSet.inline.hpp"
#include "gc/shared/concurrentGCBreakpoints.hpp"
#include "gc/shared/gcBehaviours.hpp"
#include "gc/shared/gcHeapSummary.hpp"
#include "gc/shared/gcId.hpp"
#include "gc/shared/gcLocker.hpp"
#include "gc/shared/gcTimer.hpp"
#include "gc/shared/gcTraceTime.inline.hpp"
#include "gc/shared/generationSpec.hpp"
#include "gc/shared/isGCActiveMark.hpp"
#include "gc/shared/locationPrinter.inline.hpp"
#include "gc/shared/oopStorageParState.hpp"
#include "gc/shared/preservedMarks.inline.hpp"
#include "gc/shared/suspendibleThreadSet.hpp"
#include "gc/shared/referenceProcessor.inline.hpp"
#include "gc/shared/taskTerminator.hpp"
#include "gc/shared/taskqueue.inline.hpp"
#include "gc/shared/tlab_globals.hpp"
#include "gc/shared/weakProcessor.inline.hpp"
#include "gc/shared/workerPolicy.hpp"
#include "logging/log.hpp"
#include "memory/allocation.hpp"
#include "memory/iterator.hpp"
#include "memory/heapInspection.hpp"
#include "memory/metaspaceUtils.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.hpp"
#include "oops/compressedOops.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/init.hpp"
#include "runtime/java.hpp"
#include "runtime/orderAccess.hpp"
#include "runtime/threadSMR.hpp"
#include "runtime/vmThread.hpp"
#include "utilities/align.hpp"
#include "utilities/autoRestore.hpp"
#include "utilities/bitMap.inline.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/stack.inline.hpp"

size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;

// INVARIANTS/NOTES
//
// All allocation activity covered by the G1CollectedHeap interface is
// serialized by acquiring the HeapLock.  This happens in mem_allocate
// and allocate_new_tlab, which are the "entry" points to the
// allocation code from the rest of the JVM.  (Note that this does not
// apply to TLAB allocation, which is not part of this interface: it
// is done by clients of this interface.)

void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
  HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
}

void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
  // The from card cache is not the memory that is actually committed. So we cannot
  // take advantage of the zero_filled parameter.
  reset_from_card_cache(start_idx, num_regions);
}

Tickspan G1CollectedHeap::run_task_timed(AbstractGangTask* task) {
  Ticks start = Ticks::now();
  workers()->run_task(task);
  return Ticks::now() - start;
}

void G1CollectedHeap::run_batch_task(G1BatchedGangTask* cl) {
  uint num_workers = MAX2(1u, MIN2(cl->num_workers_estimate(), workers()->active_workers()));
  cl->set_max_workers(num_workers);
  workers()->run_task(cl, num_workers);
}

HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
                                             MemRegion mr) {
  return new HeapRegion(hrs_index, bot(), mr, &_card_set_config);
}

// Private methods.

HeapRegion* G1CollectedHeap::new_region(size_t word_size,
                                        HeapRegionType type,
                                        bool do_expand,
                                        uint node_index) {
  assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
         "the only time we use this to allocate a humongous region is "
         "when we are allocating a single humongous region");

  HeapRegion* res = _hrm.allocate_free_region(type, node_index);

  if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
    // Currently, only attempts to allocate GC alloc regions set
    // do_expand to true. So, we should only reach here during a
    // safepoint. If this assumption changes we might have to
    // reconsider the use of _expand_heap_after_alloc_failure.
    assert(SafepointSynchronize::is_at_safepoint(), "invariant");

    log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
                              word_size * HeapWordSize);

    assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
           "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
           word_size * HeapWordSize);
    if (expand_single_region(node_index)) {
      // Given that expand_single_region() succeeded in expanding the heap, and we
      // always expand the heap by an amount aligned to the heap
      // region size, the free list should in theory not be empty.
      // In either case allocate_free_region() will check for NULL.
      res = _hrm.allocate_free_region(type, node_index);
    } else {
      _expand_heap_after_alloc_failure = false;
    }
  }
  return res;
}

HeapWord*
G1CollectedHeap::humongous_obj_allocate_initialize_regions(HeapRegion* first_hr,
                                                           uint num_regions,
                                                           size_t word_size) {
  assert(first_hr != NULL, "pre-condition");
  assert(is_humongous(word_size), "word_size should be humongous");
  assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");

  // Index of last region in the series.
  uint first = first_hr->hrm_index();
  uint last = first + num_regions - 1;

  // We need to initialize the region(s) we just discovered. This is
  // a bit tricky given that it can happen concurrently with
  // refinement threads refining cards on these regions and
  // potentially wanting to refine the BOT as they are scanning
  // those cards (this can happen shortly after a cleanup; see CR
  // 6991377). So we have to set up the region(s) carefully and in
  // a specific order.

  // The word size sum of all the regions we will allocate.
  size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
  assert(word_size <= word_size_sum, "sanity");

  // The passed in hr will be the "starts humongous" region. The header
  // of the new object will be placed at the bottom of this region.
  HeapWord* new_obj = first_hr->bottom();
  // This will be the new top of the new object.
  HeapWord* obj_top = new_obj + word_size;

  // First, we need to zero the header of the space that we will be
  // allocating. When we update top further down, some refinement
  // threads might try to scan the region. By zeroing the header we
  // ensure that any thread that will try to scan the region will
  // come across the zero klass word and bail out.
  //
  // NOTE: It would not have been correct to have used
  // CollectedHeap::fill_with_object() and make the space look like
  // an int array. The thread that is doing the allocation will
  // later update the object header to a potentially different array
  // type and, for a very short period of time, the klass and length
  // fields will be inconsistent. This could cause a refinement
  // thread to calculate the object size incorrectly.
  Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);

  // Next, pad out the unused tail of the last region with filler
  // objects, for improved usage accounting.
  // How many words we use for filler objects.
  size_t word_fill_size = word_size_sum - word_size;

  // How many words memory we "waste" which cannot hold a filler object.
  size_t words_not_fillable = 0;

  if (word_fill_size >= min_fill_size()) {
    fill_with_objects(obj_top, word_fill_size);
  } else if (word_fill_size > 0) {
    // We have space to fill, but we cannot fit an object there.
    words_not_fillable = word_fill_size;
    word_fill_size = 0;
  }

  // We will set up the first region as "starts humongous". This
  // will also update the BOT covering all the regions to reflect
  // that there is a single object that starts at the bottom of the
  // first region.
  first_hr->set_starts_humongous(obj_top, word_fill_size);
  _policy->remset_tracker()->update_at_allocate(first_hr);
  // Then, if there are any, we will set up the "continues
  // humongous" regions.
  HeapRegion* hr = NULL;
  for (uint i = first + 1; i <= last; ++i) {
    hr = region_at(i);
    hr->set_continues_humongous(first_hr);
    _policy->remset_tracker()->update_at_allocate(hr);
  }

  // Up to this point no concurrent thread would have been able to
  // do any scanning on any region in this series. All the top
  // fields still point to bottom, so the intersection between
  // [bottom,top] and [card_start,card_end] will be empty. Before we
  // update the top fields, we'll do a storestore to make sure that
  // no thread sees the update to top before the zeroing of the
  // object header and the BOT initialization.
  OrderAccess::storestore();

  // Now, we will update the top fields of the "continues humongous"
  // regions except the last one.
  for (uint i = first; i < last; ++i) {
    hr = region_at(i);
    hr->set_top(hr->end());
  }

  hr = region_at(last);
  // If we cannot fit a filler object, we must set top to the end
  // of the humongous object, otherwise we cannot iterate the heap
  // and the BOT will not be complete.
  hr->set_top(hr->end() - words_not_fillable);

  assert(hr->bottom() < obj_top && obj_top <= hr->end(),
         "obj_top should be in last region");

  _verifier->check_bitmaps("Humongous Region Allocation", first_hr);

  assert(words_not_fillable == 0 ||
         first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
         "Miscalculation in humongous allocation");

  increase_used((word_size_sum - words_not_fillable) * HeapWordSize);

  for (uint i = first; i <= last; ++i) {
    hr = region_at(i);
    _humongous_set.add(hr);
    _hr_printer.alloc(hr);
  }

  return new_obj;
}

size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
  assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
  return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
}

// If could fit into free regions w/o expansion, try.
// Otherwise, if can expand, do so.
// Otherwise, if using ex regions might help, try with ex given back.
HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
  assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);

  _verifier->verify_region_sets_optional();

  uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);

  // Policy: First try to allocate a humongous object in the free list.
  HeapRegion* humongous_start = _hrm.allocate_humongous(obj_regions);
  if (humongous_start == NULL) {
    // Policy: We could not find enough regions for the humongous object in the
    // free list. Look through the heap to find a mix of free and uncommitted regions.
    // If so, expand the heap and allocate the humongous object.
    humongous_start = _hrm.expand_and_allocate_humongous(obj_regions);
    if (humongous_start != NULL) {
      // We managed to find a region by expanding the heap.
      log_debug(gc, ergo, heap)("Heap expansion (humongous allocation request). Allocation request: " SIZE_FORMAT "B",
                                word_size * HeapWordSize);
      policy()->record_new_heap_size(num_regions());
    } else {
      // Policy: Potentially trigger a defragmentation GC.
    }
  }

  HeapWord* result = NULL;
  if (humongous_start != NULL) {
    result = humongous_obj_allocate_initialize_regions(humongous_start, obj_regions, word_size);
    assert(result != NULL, "it should always return a valid result");

    // A successful humongous object allocation changes the used space
    // information of the old generation so we need to recalculate the
    // sizes and update the jstat counters here.
    g1mm()->update_sizes();
  }

  _verifier->verify_region_sets_optional();

  return result;
}

HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
                                             size_t requested_size,
                                             size_t* actual_size) {
  assert_heap_not_locked_and_not_at_safepoint();
  assert(!is_humongous(requested_size), "we do not allow humongous TLABs");

  return attempt_allocation(min_size, requested_size, actual_size);
}

HeapWord*
G1CollectedHeap::mem_allocate(size_t word_size,
                              bool*  gc_overhead_limit_was_exceeded) {
  assert_heap_not_locked_and_not_at_safepoint();

  if (is_humongous(word_size)) {
    return attempt_allocation_humongous(word_size);
  }
  size_t dummy = 0;
  return attempt_allocation(word_size, word_size, &dummy);
}

HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
  ResourceMark rm; // For retrieving the thread names in log messages.

  // Make sure you read the note in attempt_allocation_humongous().

  assert_heap_not_locked_and_not_at_safepoint();
  assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
         "be called for humongous allocation requests");

  // We should only get here after the first-level allocation attempt
  // (attempt_allocation()) failed to allocate.

  // We will loop until a) we manage to successfully perform the
  // allocation or b) we successfully schedule a collection which
  // fails to perform the allocation. b) is the only case when we'll
  // return NULL.
  HeapWord* result = NULL;
  for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
    bool should_try_gc;
    bool preventive_collection_required = false;
    uint gc_count_before;

    {
      MutexLocker x(Heap_lock);

      // Now that we have the lock, we first retry the allocation in case another
      // thread changed the region while we were waiting to acquire the lock.
      size_t actual_size;
      result = _allocator->attempt_allocation(word_size, word_size, &actual_size);
      if (result != NULL) {
        return result;
      }

      preventive_collection_required = policy()->preventive_collection_required(1);
      if (!preventive_collection_required) {
        // We've already attempted a lock-free allocation above, so we don't want to
        // do it again. Let's jump straight to replacing the active region.
        result = _allocator->attempt_allocation_using_new_region(word_size);
        if (result != NULL) {
          return result;
        }

        // If the GCLocker is active and we are bound for a GC, try expanding young gen.
        // This is different to when only GCLocker::needs_gc() is set: try to avoid
        // waiting because the GCLocker is active to not wait too long.
        if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
          // No need for an ergo message here, can_expand_young_list() does this when
          // it returns true.
          result = _allocator->attempt_allocation_force(word_size);
          if (result != NULL) {
            return result;
          }
        }
      }

      // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
      // the GCLocker initiated GC has been performed and then retry. This includes
      // the case when the GC Locker is not active but has not been performed.
      should_try_gc = !GCLocker::needs_gc();
      // Read the GC count while still holding the Heap_lock.
      gc_count_before = total_collections();
    }

    if (should_try_gc) {
      GCCause::Cause gc_cause = preventive_collection_required ? GCCause::_g1_preventive_collection
                                                              : GCCause::_g1_inc_collection_pause;
      bool succeeded;
      result = do_collection_pause(word_size, gc_count_before, &succeeded, gc_cause);
      if (result != NULL) {
        assert(succeeded, "only way to get back a non-NULL result");
        log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
                             Thread::current()->name(), p2i(result));
        return result;
      }

      if (succeeded) {
        // We successfully scheduled a collection which failed to allocate. No
        // point in trying to allocate further. We'll just return NULL.
        log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
                             SIZE_FORMAT " words", Thread::current()->name(), word_size);
        return NULL;
      }
      log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
                           Thread::current()->name(), word_size);
    } else {
      // Failed to schedule a collection.
      if (gclocker_retry_count > GCLockerRetryAllocationCount) {
        log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
                               SIZE_FORMAT " words", Thread::current()->name(), word_size);
        return NULL;
      }
      log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
      // The GCLocker is either active or the GCLocker initiated
      // GC has not yet been performed. Stall until it is and
      // then retry the allocation.
      GCLocker::stall_until_clear();
      gclocker_retry_count += 1;
    }

    // We can reach here if we were unsuccessful in scheduling a
    // collection (because another thread beat us to it) or if we were
    // stalled due to the GC locker. In either can we should retry the
    // allocation attempt in case another thread successfully
    // performed a collection and reclaimed enough space. We do the
    // first attempt (without holding the Heap_lock) here and the
    // follow-on attempt will be at the start of the next loop
    // iteration (after taking the Heap_lock).
    size_t dummy = 0;
    result = _allocator->attempt_allocation(word_size, word_size, &dummy);
    if (result != NULL) {
      return result;
    }

    // Give a warning if we seem to be looping forever.
    if ((QueuedAllocationWarningCount > 0) &&
        (try_count % QueuedAllocationWarningCount == 0)) {
      log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
                             Thread::current()->name(), try_count, word_size);
    }
  }

  ShouldNotReachHere();
  return NULL;
}

void G1CollectedHeap::begin_archive_alloc_range(bool open) {
  assert_at_safepoint_on_vm_thread();
  if (_archive_allocator == NULL) {
    _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
  }
}

bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
  // Allocations in archive regions cannot be of a size that would be considered
  // humongous even for a minimum-sized region, because G1 region sizes/boundaries
  // may be different at archive-restore time.
  return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
}

HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
  assert_at_safepoint_on_vm_thread();
  assert(_archive_allocator != NULL, "_archive_allocator not initialized");
  if (is_archive_alloc_too_large(word_size)) {
    return NULL;
  }
  return _archive_allocator->archive_mem_allocate(word_size);
}

void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
                                              size_t end_alignment_in_bytes) {
  assert_at_safepoint_on_vm_thread();
  assert(_archive_allocator != NULL, "_archive_allocator not initialized");

  // Call complete_archive to do the real work, filling in the MemRegion
  // array with the archive regions.
  _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
  delete _archive_allocator;
  _archive_allocator = NULL;
}

bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
  assert(ranges != NULL, "MemRegion array NULL");
  assert(count != 0, "No MemRegions provided");
  MemRegion reserved = _hrm.reserved();
  for (size_t i = 0; i < count; i++) {
    if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
      return false;
    }
  }
  return true;
}

bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
                                            size_t count,
                                            bool open) {
  assert(!is_init_completed(), "Expect to be called at JVM init time");
  assert(ranges != NULL, "MemRegion array NULL");
  assert(count != 0, "No MemRegions provided");
  MutexLocker x(Heap_lock);

  MemRegion reserved = _hrm.reserved();
  HeapWord* prev_last_addr = NULL;
  HeapRegion* prev_last_region = NULL;

  // Temporarily disable pretouching of heap pages. This interface is used
  // when mmap'ing archived heap data in, so pre-touching is wasted.
  FlagSetting fs(AlwaysPreTouch, false);

  // For each specified MemRegion range, allocate the corresponding G1
  // regions and mark them as archive regions. We expect the ranges
  // in ascending starting address order, without overlap.
  for (size_t i = 0; i < count; i++) {
    MemRegion curr_range = ranges[i];
    HeapWord* start_address = curr_range.start();
    size_t word_size = curr_range.word_size();
    HeapWord* last_address = curr_range.last();
    size_t commits = 0;

    guarantee(reserved.contains(start_address) && reserved.contains(last_address),
              "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
              p2i(start_address), p2i(last_address));
    guarantee(start_address > prev_last_addr,
              "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
              p2i(start_address), p2i(prev_last_addr));
    prev_last_addr = last_address;

    // Check for ranges that start in the same G1 region in which the previous
    // range ended, and adjust the start address so we don't try to allocate
    // the same region again. If the current range is entirely within that
    // region, skip it, just adjusting the recorded top.
    HeapRegion* start_region = _hrm.addr_to_region(start_address);
    if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
      start_address = start_region->end();
      if (start_address > last_address) {
        increase_used(word_size * HeapWordSize);
        start_region->set_top(last_address + 1);
        continue;
      }
      start_region->set_top(start_address);
      curr_range = MemRegion(start_address, last_address + 1);
      start_region = _hrm.addr_to_region(start_address);
    }

    // Perform the actual region allocation, exiting if it fails.
    // Then note how much new space we have allocated.
    if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
      return false;
    }
    increase_used(word_size * HeapWordSize);
    if (commits != 0) {
      log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
                                HeapRegion::GrainWords * HeapWordSize * commits);

    }

    // Mark each G1 region touched by the range as archive, add it to
    // the old set, and set top.
    HeapRegion* curr_region = _hrm.addr_to_region(start_address);
    HeapRegion* last_region = _hrm.addr_to_region(last_address);
    prev_last_region = last_region;

    while (curr_region != NULL) {
      assert(curr_region->is_empty() && !curr_region->is_pinned(),
             "Region already in use (index %u)", curr_region->hrm_index());
      if (open) {
        curr_region->set_open_archive();
      } else {
        curr_region->set_closed_archive();
      }
      _hr_printer.alloc(curr_region);
      _archive_set.add(curr_region);
      HeapWord* top;
      HeapRegion* next_region;
      if (curr_region != last_region) {
        top = curr_region->end();
        next_region = _hrm.next_region_in_heap(curr_region);
      } else {
        top = last_address + 1;
        next_region = NULL;
      }
      curr_region->set_top(top);
      curr_region = next_region;
    }
  }
  return true;
}

void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
  assert(!is_init_completed(), "Expect to be called at JVM init time");
  assert(ranges != NULL, "MemRegion array NULL");
  assert(count != 0, "No MemRegions provided");
  MemRegion reserved = _hrm.reserved();
  HeapWord *prev_last_addr = NULL;
  HeapRegion* prev_last_region = NULL;

  // For each MemRegion, create filler objects, if needed, in the G1 regions
  // that contain the address range. The address range actually within the
  // MemRegion will not be modified. That is assumed to have been initialized
  // elsewhere, probably via an mmap of archived heap data.
  MutexLocker x(Heap_lock);
  for (size_t i = 0; i < count; i++) {
    HeapWord* start_address = ranges[i].start();
    HeapWord* last_address = ranges[i].last();

    assert(reserved.contains(start_address) && reserved.contains(last_address),
           "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
           p2i(start_address), p2i(last_address));
    assert(start_address > prev_last_addr,
           "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
           p2i(start_address), p2i(prev_last_addr));

    HeapRegion* start_region = _hrm.addr_to_region(start_address);
    HeapRegion* last_region = _hrm.addr_to_region(last_address);
    HeapWord* bottom_address = start_region->bottom();

    // Check for a range beginning in the same region in which the
    // previous one ended.
    if (start_region == prev_last_region) {
      bottom_address = prev_last_addr + 1;
    }

    // Verify that the regions were all marked as archive regions by
    // alloc_archive_regions.
    HeapRegion* curr_region = start_region;
    while (curr_region != NULL) {
      guarantee(curr_region->is_archive(),
                "Expected archive region at index %u", curr_region->hrm_index());
      if (curr_region != last_region) {
        curr_region = _hrm.next_region_in_heap(curr_region);
      } else {
        curr_region = NULL;
      }
    }

    prev_last_addr = last_address;
    prev_last_region = last_region;

    // Fill the memory below the allocated range with dummy object(s),
    // if the region bottom does not match the range start, or if the previous
    // range ended within the same G1 region, and there is a gap.
    assert(start_address >= bottom_address, "bottom address should not be greater than start address");
    if (start_address > bottom_address) {
      size_t fill_size = pointer_delta(start_address, bottom_address);
      G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
      increase_used(fill_size * HeapWordSize);
    }
  }
}

inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
                                                     size_t desired_word_size,
                                                     size_t* actual_word_size) {
  assert_heap_not_locked_and_not_at_safepoint();
  assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
         "be called for humongous allocation requests");

  HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);

  if (result == NULL) {
    *actual_word_size = desired_word_size;
    result = attempt_allocation_slow(desired_word_size);
  }

  assert_heap_not_locked();
  if (result != NULL) {
    assert(*actual_word_size != 0, "Actual size must have been set here");
    dirty_young_block(result, *actual_word_size);
  } else {
    *actual_word_size = 0;
  }

  return result;
}

void G1CollectedHeap::populate_archive_regions_bot_part(MemRegion* ranges, size_t count) {
  assert(!is_init_completed(), "Expect to be called at JVM init time");
  assert(ranges != NULL, "MemRegion array NULL");
  assert(count != 0, "No MemRegions provided");

  HeapWord* st = ranges[0].start();
  HeapWord* last = ranges[count-1].last();
  HeapRegion* hr_st = _hrm.addr_to_region(st);
  HeapRegion* hr_last = _hrm.addr_to_region(last);

  HeapRegion* hr_curr = hr_st;
  while (hr_curr != NULL) {
    hr_curr->update_bot();
    if (hr_curr != hr_last) {
      hr_curr = _hrm.next_region_in_heap(hr_curr);
    } else {
      hr_curr = NULL;
    }
  }
}

void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
  assert(!is_init_completed(), "Expect to be called at JVM init time");
  assert(ranges != NULL, "MemRegion array NULL");
  assert(count != 0, "No MemRegions provided");
  MemRegion reserved = _hrm.reserved();
  HeapWord* prev_last_addr = NULL;
  HeapRegion* prev_last_region = NULL;
  size_t size_used = 0;
  uint shrink_count = 0;

  // For each Memregion, free the G1 regions that constitute it, and
  // notify mark-sweep that the range is no longer to be considered 'archive.'
  MutexLocker x(Heap_lock);
  for (size_t i = 0; i < count; i++) {
    HeapWord* start_address = ranges[i].start();
    HeapWord* last_address = ranges[i].last();

    assert(reserved.contains(start_address) && reserved.contains(last_address),
           "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
           p2i(start_address), p2i(last_address));
    assert(start_address > prev_last_addr,
           "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
           p2i(start_address), p2i(prev_last_addr));
    size_used += ranges[i].byte_size();
    prev_last_addr = last_address;

    HeapRegion* start_region = _hrm.addr_to_region(start_address);
    HeapRegion* last_region = _hrm.addr_to_region(last_address);

    // Check for ranges that start in the same G1 region in which the previous
    // range ended, and adjust the start address so we don't try to free
    // the same region again. If the current range is entirely within that
    // region, skip it.
    if (start_region == prev_last_region) {
      start_address = start_region->end();
      if (start_address > last_address) {
        continue;
      }
      start_region = _hrm.addr_to_region(start_address);
    }
    prev_last_region = last_region;

    // After verifying that each region was marked as an archive region by
    // alloc_archive_regions, set it free and empty and uncommit it.
    HeapRegion* curr_region = start_region;
    while (curr_region != NULL) {
      guarantee(curr_region->is_archive(),
                "Expected archive region at index %u", curr_region->hrm_index());
      uint curr_index = curr_region->hrm_index();
      _archive_set.remove(curr_region);
      curr_region->set_free();
      curr_region->set_top(curr_region->bottom());
      if (curr_region != last_region) {
        curr_region = _hrm.next_region_in_heap(curr_region);
      } else {
        curr_region = NULL;
      }

      _hrm.shrink_at(curr_index, 1);
      shrink_count++;
    }
  }

  if (shrink_count != 0) {
    log_debug(gc, ergo, heap)("Attempt heap shrinking (archive regions). Total size: " SIZE_FORMAT "B",
                              HeapRegion::GrainWords * HeapWordSize * shrink_count);
    // Explicit uncommit.
    uncommit_regions(shrink_count);
  }
  decrease_used(size_used);
}

HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
  ResourceMark rm; // For retrieving the thread names in log messages.

  // The structure of this method has a lot of similarities to
  // attempt_allocation_slow(). The reason these two were not merged
  // into a single one is that such a method would require several "if
  // allocation is not humongous do this, otherwise do that"
  // conditional paths which would obscure its flow. In fact, an early
  // version of this code did use a unified method which was harder to
  // follow and, as a result, it had subtle bugs that were hard to
  // track down. So keeping these two methods separate allows each to
  // be more readable. It will be good to keep these two in sync as
  // much as possible.

  assert_heap_not_locked_and_not_at_safepoint();
  assert(is_humongous(word_size), "attempt_allocation_humongous() "
         "should only be called for humongous allocations");

  // Humongous objects can exhaust the heap quickly, so we should check if we
  // need to start a marking cycle at each humongous object allocation. We do
  // the check before we do the actual allocation. The reason for doing it
  // before the allocation is that we avoid having to keep track of the newly
  // allocated memory while we do a GC.
  if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
                                        word_size)) {
    collect(GCCause::_g1_humongous_allocation);
  }

  // We will loop until a) we manage to successfully perform the
  // allocation or b) we successfully schedule a collection which
  // fails to perform the allocation. b) is the only case when we'll
  // return NULL.
  HeapWord* result = NULL;
  for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
    bool should_try_gc;
    bool preventive_collection_required = false;
    uint gc_count_before;


    {
      MutexLocker x(Heap_lock);

      size_t size_in_regions = humongous_obj_size_in_regions(word_size);
      preventive_collection_required = policy()->preventive_collection_required((uint)size_in_regions);
      if (!preventive_collection_required) {
        // Given that humongous objects are not allocated in young
        // regions, we'll first try to do the allocation without doing a
        // collection hoping that there's enough space in the heap.
        result = humongous_obj_allocate(word_size);
        if (result != NULL) {
          policy()->old_gen_alloc_tracker()->
            add_allocated_humongous_bytes_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
          return result;
        }
      }

      // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
      // the GCLocker initiated GC has been performed and then retry. This includes
      // the case when the GC Locker is not active but has not been performed.
      should_try_gc = !GCLocker::needs_gc();
      // Read the GC count while still holding the Heap_lock.
      gc_count_before = total_collections();
    }

    if (should_try_gc) {
      GCCause::Cause gc_cause = preventive_collection_required ? GCCause::_g1_preventive_collection
                                                              : GCCause::_g1_humongous_allocation;
      bool succeeded;
      result = do_collection_pause(word_size, gc_count_before, &succeeded, gc_cause);
      if (result != NULL) {
        assert(succeeded, "only way to get back a non-NULL result");
        log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
                             Thread::current()->name(), p2i(result));
        size_t size_in_regions = humongous_obj_size_in_regions(word_size);
        policy()->old_gen_alloc_tracker()->
          record_collection_pause_humongous_allocation(size_in_regions * HeapRegion::GrainBytes);
        return result;
      }

      if (succeeded) {
        // We successfully scheduled a collection which failed to allocate. No
        // point in trying to allocate further. We'll just return NULL.
        log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
                             SIZE_FORMAT " words", Thread::current()->name(), word_size);
        return NULL;
      }
      log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
                           Thread::current()->name(), word_size);
    } else {
      // Failed to schedule a collection.
      if (gclocker_retry_count > GCLockerRetryAllocationCount) {
        log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
                               SIZE_FORMAT " words", Thread::current()->name(), word_size);
        return NULL;
      }
      log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
      // The GCLocker is either active or the GCLocker initiated
      // GC has not yet been performed. Stall until it is and
      // then retry the allocation.
      GCLocker::stall_until_clear();
      gclocker_retry_count += 1;
    }


    // We can reach here if we were unsuccessful in scheduling a
    // collection (because another thread beat us to it) or if we were
    // stalled due to the GC locker. In either can we should retry the
    // allocation attempt in case another thread successfully
    // performed a collection and reclaimed enough space.
    // Humongous object allocation always needs a lock, so we wait for the retry
    // in the next iteration of the loop, unlike for the regular iteration case.
    // Give a warning if we seem to be looping forever.

    if ((QueuedAllocationWarningCount > 0) &&
        (try_count % QueuedAllocationWarningCount == 0)) {
      log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
                             Thread::current()->name(), try_count, word_size);
    }
  }

  ShouldNotReachHere();
  return NULL;
}

HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
                                                           bool expect_null_mutator_alloc_region) {
  assert_at_safepoint_on_vm_thread();
  assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
         "the current alloc region was unexpectedly found to be non-NULL");

  if (!is_humongous(word_size)) {
    return _allocator->attempt_allocation_locked(word_size);
  } else {
    HeapWord* result = humongous_obj_allocate(word_size);
    if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
      collector_state()->set_initiate_conc_mark_if_possible(true);
    }
    return result;
  }

  ShouldNotReachHere();
}

class PostCompactionPrinterClosure: public HeapRegionClosure {
private:
  G1HRPrinter* _hr_printer;
public:
  bool do_heap_region(HeapRegion* hr) {
    assert(!hr->is_young(), "not expecting to find young regions");
    _hr_printer->post_compaction(hr);
    return false;
  }

  PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
    : _hr_printer(hr_printer) { }
};

void G1CollectedHeap::print_hrm_post_compaction() {
  if (_hr_printer.is_active()) {
    PostCompactionPrinterClosure cl(hr_printer());
    heap_region_iterate(&cl);
  }
}

void G1CollectedHeap::abort_concurrent_cycle() {
  // If we start the compaction before the CM threads finish
  // scanning the root regions we might trip them over as we'll
  // be moving objects / updating references. So let's wait until
  // they are done. By telling them to abort, they should complete
  // early.
  _cm->root_regions()->abort();
  _cm->root_regions()->wait_until_scan_finished();

  // Disable discovery and empty the discovered lists
  // for the CM ref processor.
  _ref_processor_cm->disable_discovery();
  _ref_processor_cm->abandon_partial_discovery();
  _ref_processor_cm->verify_no_references_recorded();

  // Abandon current iterations of concurrent marking and concurrent
  // refinement, if any are in progress.
  concurrent_mark()->concurrent_cycle_abort();
}

void G1CollectedHeap::prepare_heap_for_full_collection() {
  // Make sure we'll choose a new allocation region afterwards.
  _allocator->release_mutator_alloc_regions();
  _allocator->abandon_gc_alloc_regions();

  // We may have added regions to the current incremental collection
  // set between the last GC or pause and now. We need to clear the
  // incremental collection set and then start rebuilding it afresh
  // after this full GC.
  abandon_collection_set(collection_set());

  _hrm.remove_all_free_regions();
}

void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
  assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
  assert_used_and_recalculate_used_equal(this);
  _verifier->verify_region_sets_optional();
  _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
  _verifier->check_bitmaps("Full GC Start");
}

void G1CollectedHeap::prepare_heap_for_mutators() {
  // Delete metaspaces for unloaded class loaders and clean up loader_data graph
  ClassLoaderDataGraph::purge(/*at_safepoint*/true);
  DEBUG_ONLY(MetaspaceUtils::verify();)

  // Prepare heap for normal collections.
  assert(num_free_regions() == 0, "we should not have added any free regions");
  rebuild_region_sets(false /* free_list_only */);
  abort_refinement();
  resize_heap_if_necessary();
  uncommit_regions_if_necessary();

  // Rebuild the strong code root lists for each region
  rebuild_strong_code_roots();

  // Purge code root memory
  purge_code_root_memory();

  // Start a new incremental collection set for the next pause
  start_new_collection_set();

  _allocator->init_mutator_alloc_regions();

  // Post collection state updates.
  MetaspaceGC::compute_new_size();
}

void G1CollectedHeap::abort_refinement() {
  if (_hot_card_cache->use_cache()) {
    _hot_card_cache->reset_hot_cache();
  }

  // Discard all remembered set updates and reset refinement statistics.
  G1BarrierSet::dirty_card_queue_set().abandon_logs();
  assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
         "DCQS should be empty");
  concurrent_refine()->get_and_reset_refinement_stats();
}

void G1CollectedHeap::verify_after_full_collection() {
  _hrm.verify_optional();
  _verifier->verify_region_sets_optional();
  _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);

  // This call implicitly verifies that the next bitmap is clear after Full GC.
  _verifier->check_bitmaps("Full GC End");

  // At this point there should be no regions in the
  // entire heap tagged as young.
  assert(check_young_list_empty(), "young list should be empty at this point");

  // Note: since we've just done a full GC, concurrent
  // marking is no longer active. Therefore we need not
  // re-enable reference discovery for the CM ref processor.
  // That will be done at the start of the next marking cycle.
  // We also know that the STW processor should no longer
  // discover any new references.
  assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
  assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
  _ref_processor_stw->verify_no_references_recorded();
  _ref_processor_cm->verify_no_references_recorded();
}

void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
  // Post collection logging.
  // We should do this after we potentially resize the heap so
  // that all the COMMIT / UNCOMMIT events are generated before
  // the compaction events.
  print_hrm_post_compaction();
  heap_transition->print();
  print_heap_after_gc();
  print_heap_regions();
}

bool G1CollectedHeap::do_full_collection(bool explicit_gc,
                                         bool clear_all_soft_refs,
                                         bool do_maximum_compaction) {
  assert_at_safepoint_on_vm_thread();

  if (GCLocker::check_active_before_gc()) {
    // Full GC was not completed.
    return false;
  }

  const bool do_clear_all_soft_refs = clear_all_soft_refs ||
      soft_ref_policy()->should_clear_all_soft_refs();

  G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs, do_maximum_compaction);
  GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);

  collector.prepare_collection();
  collector.collect();
  collector.complete_collection();

  // Full collection was successfully completed.
  return true;
}

void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
  // Currently, there is no facility in the do_full_collection(bool) API to notify
  // the caller that the collection did not succeed (e.g., because it was locked
  // out by the GC locker). So, right now, we'll ignore the return value.
  // When clear_all_soft_refs is set we want to do a maximum compaction
  // not leaving any dead wood.
  bool do_maximum_compaction = clear_all_soft_refs;
  bool dummy = do_full_collection(true,                /* explicit_gc */
                                  clear_all_soft_refs,
                                  do_maximum_compaction);
}

bool G1CollectedHeap::upgrade_to_full_collection() {
  GCCauseSetter compaction(this, GCCause::_g1_compaction_pause);
  log_info(gc, ergo)("Attempting full compaction clearing soft references");
  bool success = do_full_collection(false /* explicit gc */,
                                    true  /* clear_all_soft_refs */,
                                    false /* do_maximum_compaction */);
  // do_full_collection only fails if blocked by GC locker and that can't
  // be the case here since we only call this when already completed one gc.
  assert(success, "invariant");
  return success;
}

void G1CollectedHeap::resize_heap_if_necessary() {
  assert_at_safepoint_on_vm_thread();

  bool should_expand;
  size_t resize_amount = _heap_sizing_policy->full_collection_resize_amount(should_expand);

  if (resize_amount == 0) {
    return;
  } else if (should_expand) {
    expand(resize_amount, _workers);
  } else {
    shrink(resize_amount);
  }
}

HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
                                                            bool do_gc,
                                                            bool maximum_compaction,
                                                            bool expect_null_mutator_alloc_region,
                                                            bool* gc_succeeded) {
  *gc_succeeded = true;
  // Let's attempt the allocation first.
  HeapWord* result =
    attempt_allocation_at_safepoint(word_size,
                                    expect_null_mutator_alloc_region);
  if (result != NULL) {
    return result;
  }

  // In a G1 heap, we're supposed to keep allocation from failing by
  // incremental pauses.  Therefore, at least for now, we'll favor
  // expansion over collection.  (This might change in the future if we can
  // do something smarter than full collection to satisfy a failed alloc.)
  result = expand_and_allocate(word_size);
  if (result != NULL) {
    return result;
  }

  if (do_gc) {
    GCCauseSetter compaction(this, GCCause::_g1_compaction_pause);
    // Expansion didn't work, we'll try to do a Full GC.
    // If maximum_compaction is set we clear all soft references and don't
    // allow any dead wood to be left on the heap.
    if (maximum_compaction) {
      log_info(gc, ergo)("Attempting maximum full compaction clearing soft references");
    } else {
      log_info(gc, ergo)("Attempting full compaction");
    }
    *gc_succeeded = do_full_collection(false, /* explicit_gc */
                                       maximum_compaction /* clear_all_soft_refs */ ,
                                       maximum_compaction /* do_maximum_compaction */);
  }

  return NULL;
}

HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
                                                     bool* succeeded) {
  assert_at_safepoint_on_vm_thread();

  // Attempts to allocate followed by Full GC.
  HeapWord* result =
    satisfy_failed_allocation_helper(word_size,
                                     true,  /* do_gc */
                                     false, /* maximum_collection */
                                     false, /* expect_null_mutator_alloc_region */
                                     succeeded);

  if (result != NULL || !*succeeded) {
    return result;
  }

  // Attempts to allocate followed by Full GC that will collect all soft references.
  result = satisfy_failed_allocation_helper(word_size,
                                            true, /* do_gc */
                                            true, /* maximum_collection */
                                            true, /* expect_null_mutator_alloc_region */
                                            succeeded);

  if (result != NULL || !*succeeded) {
    return result;
  }

  // Attempts to allocate, no GC
  result = satisfy_failed_allocation_helper(word_size,
                                            false, /* do_gc */
                                            false, /* maximum_collection */
                                            true,  /* expect_null_mutator_alloc_region */
                                            succeeded);

  if (result != NULL) {
    return result;
  }

  assert(!soft_ref_policy()->should_clear_all_soft_refs(),
         "Flag should have been handled and cleared prior to this point");

  // What else?  We might try synchronous finalization later.  If the total
  // space available is large enough for the allocation, then a more
  // complete compaction phase than we've tried so far might be
  // appropriate.
  return NULL;
}

// Attempting to expand the heap sufficiently
// to support an allocation of the given "word_size".  If
// successful, perform the allocation and return the address of the
// allocated block, or else "NULL".

HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
  assert_at_safepoint_on_vm_thread();

  _verifier->verify_region_sets_optional();

  size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
  log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
                            word_size * HeapWordSize);


  if (expand(expand_bytes, _workers)) {
    _hrm.verify_optional();
    _verifier->verify_region_sets_optional();
    return attempt_allocation_at_safepoint(word_size,
                                           false /* expect_null_mutator_alloc_region */);
  }
  return NULL;
}

bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
  size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
  aligned_expand_bytes = align_up(aligned_expand_bytes,
                                       HeapRegion::GrainBytes);

  log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
                            expand_bytes, aligned_expand_bytes);

  if (is_maximal_no_gc()) {
    log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
    return false;
  }

  double expand_heap_start_time_sec = os::elapsedTime();
  uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
  assert(regions_to_expand > 0, "Must expand by at least one region");

  uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
  if (expand_time_ms != NULL) {
    *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
  }

  if (expanded_by > 0) {
    size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
    assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
    policy()->record_new_heap_size(num_regions());
  } else {
    log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");

    // The expansion of the virtual storage space was unsuccessful.
    // Let's see if it was because we ran out of swap.
    if (G1ExitOnExpansionFailure &&
        _hrm.available() >= regions_to_expand) {
      // We had head room...
      vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
    }
  }
  return regions_to_expand > 0;
}

bool G1CollectedHeap::expand_single_region(uint node_index) {
  uint expanded_by = _hrm.expand_on_preferred_node(node_index);

  if (expanded_by == 0) {
    assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm.available());
    log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
    return false;
  }

  policy()->record_new_heap_size(num_regions());
  return true;
}

void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
  size_t aligned_shrink_bytes =
    ReservedSpace::page_align_size_down(shrink_bytes);
  aligned_shrink_bytes = align_down(aligned_shrink_bytes,
                                         HeapRegion::GrainBytes);
  uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);

  uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
  size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;

  log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B",
                            shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
  if (num_regions_removed > 0) {
    log_debug(gc, heap)("Uncommittable regions after shrink: %u", num_regions_removed);
    policy()->record_new_heap_size(num_regions());
  } else {
    log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
  }
}

void G1CollectedHeap::shrink(size_t shrink_bytes) {
  _verifier->verify_region_sets_optional();

  // We should only reach here at the end of a Full GC or during Remark which
  // means we should not not be holding to any GC alloc regions. The method
  // below will make sure of that and do any remaining clean up.
  _allocator->abandon_gc_alloc_regions();

  // Instead of tearing down / rebuilding the free lists here, we
  // could instead use the remove_all_pending() method on free_list to
  // remove only the ones that we need to remove.
  _hrm.remove_all_free_regions();
  shrink_helper(shrink_bytes);
  rebuild_region_sets(true /* free_list_only */);

  _hrm.verify_optional();
  _verifier->verify_region_sets_optional();
}

class OldRegionSetChecker : public HeapRegionSetChecker {
public:
  void check_mt_safety() {
    // Master Old Set MT safety protocol:
    // (a) If we're at a safepoint, operations on the master old set
    // should be invoked:
    // - by the VM thread (which will serialize them), or
    // - by the GC workers while holding the FreeList_lock, if we're
    //   at a safepoint for an evacuation pause (this lock is taken
    //   anyway when an GC alloc region is retired so that a new one
    //   is allocated from the free list), or
    // - by the GC workers while holding the OldSets_lock, if we're at a
    //   safepoint for a cleanup pause.
    // (b) If we're not at a safepoint, operations on the master old set
    // should be invoked while holding the Heap_lock.

    if (SafepointSynchronize::is_at_safepoint()) {
      guarantee(Thread::current()->is_VM_thread() ||
                FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
                "master old set MT safety protocol at a safepoint");
    } else {
      guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
    }
  }
  bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
  const char* get_description() { return "Old Regions"; }
};

class ArchiveRegionSetChecker : public HeapRegionSetChecker {
public:
  void check_mt_safety() {
    guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
              "May only change archive regions during initialization or safepoint.");
  }
  bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
  const char* get_description() { return "Archive Regions"; }
};

class HumongousRegionSetChecker : public HeapRegionSetChecker {
public:
  void check_mt_safety() {
    // Humongous Set MT safety protocol:
    // (a) If we're at a safepoint, operations on the master humongous
    // set should be invoked by either the VM thread (which will
    // serialize them) or by the GC workers while holding the
    // OldSets_lock.
    // (b) If we're not at a safepoint, operations on the master
    // humongous set should be invoked while holding the Heap_lock.

    if (SafepointSynchronize::is_at_safepoint()) {
      guarantee(Thread::current()->is_VM_thread() ||
                OldSets_lock->owned_by_self(),
                "master humongous set MT safety protocol at a safepoint");
    } else {
      guarantee(Heap_lock->owned_by_self(),
                "master humongous set MT safety protocol outside a safepoint");
    }
  }
  bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
  const char* get_description() { return "Humongous Regions"; }
};

G1CollectedHeap::G1CollectedHeap() :
  CollectedHeap(),
  _service_thread(NULL),
  _periodic_gc_task(NULL),
  _free_card_set_memory_task(NULL),
  _workers(NULL),
  _card_table(NULL),
  _collection_pause_end(Ticks::now()),
  _soft_ref_policy(),
  _old_set("Old Region Set", new OldRegionSetChecker()),
  _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
  _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
  _bot(NULL),
  _listener(),
  _numa(G1NUMA::create()),
  _hrm(),
  _allocator(NULL),
  _verifier(NULL),
  _summary_bytes_used(0),
  _bytes_used_during_gc(0),
  _archive_allocator(NULL),
  _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
  _old_evac_stats("Old", OldPLABSize, PLABWeight),
  _expand_heap_after_alloc_failure(true),
  _g1mm(NULL),
  _humongous_reclaim_candidates(),
  _num_humongous_objects(0),
  _num_humongous_reclaim_candidates(0),
  _hr_printer(),
  _collector_state(),
  _old_marking_cycles_started(0),
  _old_marking_cycles_completed(0),
  _eden(),
  _survivor(),
  _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
  _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
  _policy(new G1Policy(_gc_timer_stw)),
  _heap_sizing_policy(NULL),
  _collection_set(this, _policy),
  _hot_card_cache(NULL),
  _rem_set(NULL),
  _card_set_config(),
  _cm(NULL),
  _cm_thread(NULL),
  _cr(NULL),
  _task_queues(NULL),
  _num_regions_failed_evacuation(0),
  _regions_failed_evacuation(mtGC),
  _evacuation_failed_info_array(NULL),
  _preserved_marks_set(true /* in_c_heap */),
#ifndef PRODUCT
  _evacuation_failure_alot_for_current_gc(false),
  _evacuation_failure_alot_gc_number(0),
  _evacuation_failure_alot_count(0),
#endif
  _ref_processor_stw(NULL),
  _is_alive_closure_stw(this),
  _is_subject_to_discovery_stw(this),
  _ref_processor_cm(NULL),
  _is_alive_closure_cm(this),
  _is_subject_to_discovery_cm(this),
  _region_attr() {

  _verifier = new G1HeapVerifier(this);

  _allocator = new G1Allocator(this);

  _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());

  _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);

  // Override the default _filler_array_max_size so that no humongous filler
  // objects are created.
  _filler_array_max_size = _humongous_object_threshold_in_words;

  uint n_queues = ParallelGCThreads;
  _task_queues = new G1ScannerTasksQueueSet(n_queues);

  _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);

  for (uint i = 0; i < n_queues; i++) {
    G1ScannerTasksQueue* q = new G1ScannerTasksQueue();
    q->initialize();
    _task_queues->register_queue(i, q);
    ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
  }

  // Initialize the G1EvacuationFailureALot counters and flags.
  NOT_PRODUCT(reset_evacuation_should_fail();)
  _gc_tracer_stw->initialize();

  guarantee(_task_queues != NULL, "task_queues allocation failure.");
}

G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
                                                                 size_t size,
                                                                 size_t translation_factor) {
  size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
  // Allocate a new reserved space, preferring to use large pages.
  ReservedSpace rs(size, preferred_page_size);
  size_t page_size = rs.page_size();
  G1RegionToSpaceMapper* result  =
    G1RegionToSpaceMapper::create_mapper(rs,
                                         size,
                                         page_size,
                                         HeapRegion::GrainBytes,
                                         translation_factor,
                                         mtGC);

  os::trace_page_sizes_for_requested_size(description,
                                          size,
                                          page_size,
                                          preferred_page_size,
                                          rs.base(),
                                          rs.size());

  return result;
}

jint G1CollectedHeap::initialize_concurrent_refinement() {
  jint ecode = JNI_OK;
  _cr = G1ConcurrentRefine::create(&ecode);
  return ecode;
}

jint G1CollectedHeap::initialize_service_thread() {
  _service_thread = new G1ServiceThread();
  if (_service_thread->osthread() == NULL) {
    vm_shutdown_during_initialization("Could not create G1ServiceThread");
    return JNI_ENOMEM;
  }
  return JNI_OK;
}

jint G1CollectedHeap::initialize() {

  // Necessary to satisfy locking discipline assertions.

  MutexLocker x(Heap_lock);

  // While there are no constraints in the GC code that HeapWordSize
  // be any particular value, there are multiple other areas in the
  // system which believe this to be true (e.g. oop->object_size in some
  // cases incorrectly returns the size in wordSize units rather than
  // HeapWordSize).
  guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");

  size_t init_byte_size = InitialHeapSize;
  size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();

  // Ensure that the sizes are properly aligned.
  Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
  Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
  Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");

  // Reserve the maximum.

  // When compressed oops are enabled, the preferred heap base
  // is calculated by subtracting the requested size from the
  // 32Gb boundary and using the result as the base address for
  // heap reservation. If the requested size is not aligned to
  // HeapRegion::GrainBytes (i.e. the alignment that is passed
  // into the ReservedHeapSpace constructor) then the actual
  // base of the reserved heap may end up differing from the
  // address that was requested (i.e. the preferred heap base).
  // If this happens then we could end up using a non-optimal
  // compressed oops mode.

  ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
                                                     HeapAlignment);

  initialize_reserved_region(heap_rs);

  // Create the barrier set for the entire reserved region.
  G1CardTable* ct = new G1CardTable(heap_rs.region());
  ct->initialize();
  G1BarrierSet* bs = new G1BarrierSet(ct);
  bs->initialize();
  assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
  BarrierSet::set_barrier_set(bs);
  _card_table = ct;

  {
    G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
    satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
    satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
  }

  // Create the hot card cache.
  _hot_card_cache = new G1HotCardCache(this);

  // Create space mappers.
  size_t page_size = heap_rs.page_size();
  G1RegionToSpaceMapper* heap_storage =
    G1RegionToSpaceMapper::create_mapper(heap_rs,
                                         heap_rs.size(),
                                         page_size,
                                         HeapRegion::GrainBytes,
                                         1,
                                         mtJavaHeap);
  if(heap_storage == NULL) {
    vm_shutdown_during_initialization("Could not initialize G1 heap");
    return JNI_ERR;
  }

  os::trace_page_sizes("Heap",
                       MinHeapSize,
                       reserved_byte_size,
                       page_size,
                       heap_rs.base(),
                       heap_rs.size());
  heap_storage->set_mapping_changed_listener(&_listener);

  // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
  G1RegionToSpaceMapper* bot_storage =
    create_aux_memory_mapper("Block Offset Table",
                             G1BlockOffsetTable::compute_size(heap_rs.size() / HeapWordSize),
                             G1BlockOffsetTable::heap_map_factor());

  G1RegionToSpaceMapper* cardtable_storage =
    create_aux_memory_mapper("Card Table",
                             G1CardTable::compute_size(heap_rs.size() / HeapWordSize),
                             G1CardTable::heap_map_factor());

  G1RegionToSpaceMapper* card_counts_storage =
    create_aux_memory_mapper("Card Counts Table",
                             G1CardCounts::compute_size(heap_rs.size() / HeapWordSize),
                             G1CardCounts::heap_map_factor());

  size_t bitmap_size = G1CMBitMap::compute_size(heap_rs.size());
  G1RegionToSpaceMapper* prev_bitmap_storage =
    create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
  G1RegionToSpaceMapper* next_bitmap_storage =
    create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());

  _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
  _card_table->initialize(cardtable_storage);

  // Do later initialization work for concurrent refinement.
  _hot_card_cache->initialize(card_counts_storage);

  // 6843694 - ensure that the maximum region index can fit
  // in the remembered set structures.
  const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
  guarantee((max_reserved_regions() - 1) <= max_region_idx, "too many regions");

  // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
  // start within the first card.
  guarantee(heap_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
  G1FromCardCache::initialize(max_reserved_regions());
  // Also create a G1 rem set.
  _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
  _rem_set->initialize(max_reserved_regions());

  size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
  guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
  guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
            "too many cards per region");

  FreeRegionList::set_unrealistically_long_length(max_regions() + 1);

  _bot = new G1BlockOffsetTable(reserved(), bot_storage);

  {
    size_t granularity = HeapRegion::GrainBytes;

    _region_attr.initialize(reserved(), granularity);
    _humongous_reclaim_candidates.initialize(reserved(), granularity);
  }

  _workers = new WorkGang("GC Thread", ParallelGCThreads,
                          true /* are_GC_task_threads */,
                          false /* are_ConcurrentGC_threads */);
  if (_workers == NULL) {
    return JNI_ENOMEM;
  }
  _workers->initialize_workers();

  _numa->set_region_info(HeapRegion::GrainBytes, page_size);

  // Create the G1ConcurrentMark data structure and thread.
  // (Must do this late, so that "max_[reserved_]regions" is defined.)
  _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
  _cm_thread = _cm->cm_thread();

  // Now expand into the initial heap size.
  if (!expand(init_byte_size, _workers)) {
    vm_shutdown_during_initialization("Failed to allocate initial heap.");
    return JNI_ENOMEM;
  }

  // Perform any initialization actions delegated to the policy.
  policy()->init(this, &_collection_set);

  jint ecode = initialize_concurrent_refinement();
  if (ecode != JNI_OK) {
    return ecode;
  }

  ecode = initialize_service_thread();
  if (ecode != JNI_OK) {
    return ecode;
  }

  // Initialize and schedule sampling task on service thread.
  _rem_set->initialize_sampling_task(service_thread());

  // Create and schedule the periodic gc task on the service thread.
  _periodic_gc_task = new G1PeriodicGCTask("Periodic GC Task");
  _service_thread->register_task(_periodic_gc_task);

  _free_card_set_memory_task = new G1CardSetFreeMemoryTask("Card Set Free Memory Task");
  _service_thread->register_task(_free_card_set_memory_task);

  {
    G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
    dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
    dcqs.set_max_cards(concurrent_refine()->red_zone());
  }

  // Here we allocate the dummy HeapRegion that is required by the
  // G1AllocRegion class.
  HeapRegion* dummy_region = _hrm.get_dummy_region();

  // We'll re-use the same region whether the alloc region will
  // require BOT updates or not and, if it doesn't, then a non-young
  // region will complain that it cannot support allocations without
  // BOT updates. So we'll tag the dummy region as eden to avoid that.
  dummy_region->set_eden();
  // Make sure it's full.
  dummy_region->set_top(dummy_region->end());
  G1AllocRegion::setup(this, dummy_region);

  _allocator->init_mutator_alloc_regions();

  // Do create of the monitoring and management support so that
  // values in the heap have been properly initialized.
  _g1mm = new G1MonitoringSupport(this);

  _preserved_marks_set.init(ParallelGCThreads);

  _collection_set.initialize(max_reserved_regions());

  _regions_failed_evacuation.resize(max_regions());

  G1InitLogger::print();

  return JNI_OK;
}

void G1CollectedHeap::stop() {
  // Stop all concurrent threads. We do this to make sure these threads
  // do not continue to execute and access resources (e.g. logging)
  // that are destroyed during shutdown.
  _cr->stop();
  _service_thread->stop();
  _cm_thread->stop();
}

void G1CollectedHeap::safepoint_synchronize_begin() {
  SuspendibleThreadSet::synchronize();
}

void G1CollectedHeap::safepoint_synchronize_end() {
  SuspendibleThreadSet::desynchronize();
}

void G1CollectedHeap::post_initialize() {
  CollectedHeap::post_initialize();
  ref_processing_init();
}

void G1CollectedHeap::ref_processing_init() {
  // Reference processing in G1 currently works as follows:
  //
  // * There are two reference processor instances. One is
  //   used to record and process discovered references
  //   during concurrent marking; the other is used to
  //   record and process references during STW pauses
  //   (both full and incremental).
  // * Both ref processors need to 'span' the entire heap as
  //   the regions in the collection set may be dotted around.
  //
  // * For the concurrent marking ref processor:
  //   * Reference discovery is enabled at concurrent start.
  //   * Reference discovery is disabled and the discovered
  //     references processed etc during remarking.
  //   * Reference discovery is MT (see below).
  //   * Reference discovery requires a barrier (see below).
  //   * Reference processing may or may not be MT
  //     (depending on the value of ParallelRefProcEnabled
  //     and ParallelGCThreads).
  //   * A full GC disables reference discovery by the CM
  //     ref processor and abandons any entries on it's
  //     discovered lists.
  //
  // * For the STW processor:
  //   * Non MT discovery is enabled at the start of a full GC.
  //   * Processing and enqueueing during a full GC is non-MT.
  //   * During a full GC, references are processed after marking.
  //
  //   * Discovery (may or may not be MT) is enabled at the start
  //     of an incremental evacuation pause.
  //   * References are processed near the end of a STW evacuation pause.
  //   * For both types of GC:
  //     * Discovery is atomic - i.e. not concurrent.
  //     * Reference discovery will not need a barrier.

  // Concurrent Mark ref processor
  _ref_processor_cm =
    new ReferenceProcessor(&_is_subject_to_discovery_cm,
                           ParallelGCThreads,                              // degree of mt processing
                           (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
                           MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
                           false,                                          // Reference discovery is not atomic
                           &_is_alive_closure_cm);                         // is alive closure

  // STW ref processor
  _ref_processor_stw =
    new ReferenceProcessor(&_is_subject_to_discovery_stw,
                           ParallelGCThreads,                    // degree of mt processing
                           (ParallelGCThreads > 1),              // mt discovery
                           ParallelGCThreads,                    // degree of mt discovery
                           true,                                 // Reference discovery is atomic
                           &_is_alive_closure_stw);              // is alive closure
}

SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
  return &_soft_ref_policy;
}

size_t G1CollectedHeap::capacity() const {
  return _hrm.length() * HeapRegion::GrainBytes;
}

size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
  return _hrm.total_free_bytes();
}

void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
  _hot_card_cache->drain(cl, worker_id);
}

// Computes the sum of the storage used by the various regions.
size_t G1CollectedHeap::used() const {
  size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
  if (_archive_allocator != NULL) {
    result += _archive_allocator->used();
  }
  return result;
}

size_t G1CollectedHeap::used_unlocked() const {
  return _summary_bytes_used;
}

class SumUsedClosure: public HeapRegionClosure {
  size_t _used;
public:
  SumUsedClosure() : _used(0) {}
  bool do_heap_region(HeapRegion* r) {
    _used += r->used();
    return false;
  }
  size_t result() { return _used; }
};

size_t G1CollectedHeap::recalculate_used() const {
  SumUsedClosure blk;
  heap_region_iterate(&blk);
  return blk.result();
}

bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
  switch (cause) {
    case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
    case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
    case GCCause::_wb_conc_mark:                        return true;
    default :                                           return false;
  }
}

bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
  switch (cause) {
    case GCCause::_g1_humongous_allocation: return true;
    case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
    case GCCause::_wb_breakpoint:           return true;
    default:                                return is_user_requested_concurrent_full_gc(cause);
  }
}

#ifndef PRODUCT
void G1CollectedHeap::allocate_dummy_regions() {
  // Let's fill up most of the region
  size_t word_size = HeapRegion::GrainWords - 1024;
  // And as a result the region we'll allocate will be humongous.
  guarantee(is_humongous(word_size), "sanity");

  // _filler_array_max_size is set to humongous object threshold
  // but temporarily change it to use CollectedHeap::fill_with_object().
  AutoModifyRestore<size_t> temporarily(_filler_array_max_size, word_size);

  for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
    // Let's use the existing mechanism for the allocation
    HeapWord* dummy_obj = humongous_obj_allocate(word_size);
    if (dummy_obj != NULL) {
      MemRegion mr(dummy_obj, word_size);
      CollectedHeap::fill_with_object(mr);
    } else {
      // If we can't allocate once, we probably cannot allocate
      // again. Let's get out of the loop.
      break;
    }
  }
}
#endif // !PRODUCT

void G1CollectedHeap::increment_old_marking_cycles_started() {
  assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
         _old_marking_cycles_started == _old_marking_cycles_completed + 1,
         "Wrong marking cycle count (started: %d, completed: %d)",
         _old_marking_cycles_started, _old_marking_cycles_completed);

  _old_marking_cycles_started++;
}

void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent,
                                                             bool whole_heap_examined) {
  MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);

  // We assume that if concurrent == true, then the caller is a
  // concurrent thread that was joined the Suspendible Thread
  // Set. If there's ever a cheap way to check this, we should add an
  // assert here.

  // Given that this method is called at the end of a Full GC or of a
  // concurrent cycle, and those can be nested (i.e., a Full GC can
  // interrupt a concurrent cycle), the number of full collections
  // completed should be either one (in the case where there was no
  // nesting) or two (when a Full GC interrupted a concurrent cycle)
  // behind the number of full collections started.

  // This is the case for the inner caller, i.e. a Full GC.
  assert(concurrent ||
         (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
         (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
         "for inner caller (Full GC): _old_marking_cycles_started = %u "
         "is inconsistent with _old_marking_cycles_completed = %u",
         _old_marking_cycles_started, _old_marking_cycles_completed);

  // This is the case for the outer caller, i.e. the concurrent cycle.
  assert(!concurrent ||
         (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
         "for outer caller (concurrent cycle): "
         "_old_marking_cycles_started = %u "
         "is inconsistent with _old_marking_cycles_completed = %u",
         _old_marking_cycles_started, _old_marking_cycles_completed);

  _old_marking_cycles_completed += 1;
  if (whole_heap_examined) {
    // Signal that we have completed a visit to all live objects.
    record_whole_heap_examined_timestamp();
  }

  // We need to clear the "in_progress" flag in the CM thread before
  // we wake up any waiters (especially when ExplicitInvokesConcurrent
  // is set) so that if a waiter requests another System.gc() it doesn't
  // incorrectly see that a marking cycle is still in progress.
  if (concurrent) {
    _cm_thread->set_idle();
  }

  // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
  // for a full GC to finish that their wait is over.
  ml.notify_all();
}

void G1CollectedHeap::collect(GCCause::Cause cause) {
  try_collect(cause);
}

// Return true if (x < y) with allowance for wraparound.
static bool gc_counter_less_than(uint x, uint y) {
  return (x - y) > (UINT_MAX/2);
}

// LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
// Macro so msg printing is format-checked.
#define LOG_COLLECT_CONCURRENTLY(cause, ...)                            \
  do {                                                                  \
    LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt;                   \
    if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) {                     \
      ResourceMark rm; /* For thread name. */                           \
      LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
      LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
                                       Thread::current()->name(),       \
                                       GCCause::to_string(cause));      \
      LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__);                    \
    }                                                                   \
  } while (0)

#define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
  LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))

bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
                                               uint gc_counter,
                                               uint old_marking_started_before) {
  assert_heap_not_locked();
  assert(should_do_concurrent_full_gc(cause),
         "Non-concurrent cause %s", GCCause::to_string(cause));

  for (uint i = 1; true; ++i) {
    // Try to schedule concurrent start evacuation pause that will
    // start a concurrent cycle.
    LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
    VM_G1TryInitiateConcMark op(gc_counter,
                                cause,
                                policy()->max_pause_time_ms());
    VMThread::execute(&op);

    // Request is trivially finished.
    if (cause == GCCause::_g1_periodic_collection) {
      LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
      return op.gc_succeeded();
    }

    // If VMOp skipped initiating concurrent marking cycle because
    // we're terminating, then we're done.
    if (op.terminating()) {
      LOG_COLLECT_CONCURRENTLY(cause, "skipped: terminating");
      return false;
    }

    // Lock to get consistent set of values.
    uint old_marking_started_after;
    uint old_marking_completed_after;
    {
      MutexLocker ml(Heap_lock);
      // Update gc_counter for retrying VMOp if needed. Captured here to be
      // consistent with the values we use below for termination tests.  If
      // a retry is needed after a possible wait, and another collection
      // occurs in the meantime, it will cause our retry to be skipped and
      // we'll recheck for termination with updated conditions from that
      // more recent collection.  That's what we want, rather than having
      // our retry possibly perform an unnecessary collection.
      gc_counter = total_collections();
      old_marking_started_after = _old_marking_cycles_started;
      old_marking_completed_after = _old_marking_cycles_completed;
    }

    if (cause == GCCause::_wb_breakpoint) {
      if (op.gc_succeeded()) {
        LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
        return true;
      }
      // When _wb_breakpoint there can't be another cycle or deferred.
      assert(!op.cycle_already_in_progress(), "invariant");
      assert(!op.whitebox_attached(), "invariant");
      // Concurrent cycle attempt might have been cancelled by some other
      // collection, so retry.  Unlike other cases below, we want to retry
      // even if cancelled by a STW full collection, because we really want
      // to start a concurrent cycle.
      if (old_marking_started_before != old_marking_started_after) {
        LOG_COLLECT_CONCURRENTLY(cause, "ignoring STW full GC");
        old_marking_started_before = old_marking_started_after;
      }
    } else if (!GCCause::is_user_requested_gc(cause)) {
      // For an "automatic" (not user-requested) collection, we just need to
      // ensure that progress is made.
      //
      // Request is finished if any of
      // (1) the VMOp successfully performed a GC,
      // (2) a concurrent cycle was already in progress,
      // (3) whitebox is controlling concurrent cycles,
      // (4) a new cycle was started (by this thread or some other), or
      // (5) a Full GC was performed.
      // Cases (4) and (5) are detected together by a change to
      // _old_marking_cycles_started.
      //
      // Note that (1) does not imply (4).  If we're still in the mixed
      // phase of an earlier concurrent collection, the request to make the
      // collection a concurrent start won't be honored.  If we don't check for
      // both conditions we'll spin doing back-to-back collections.
      if (op.gc_succeeded() ||
          op.cycle_already_in_progress() ||
          op.whitebox_attached() ||
          (old_marking_started_before != old_marking_started_after)) {
        LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
        return true;
      }
    } else {                    // User-requested GC.
      // For a user-requested collection, we want to ensure that a complete
      // full collection has been performed before returning, but without
      // waiting for more than needed.

      // For user-requested GCs (unlike non-UR), a successful VMOp implies a
      // new cycle was started.  That's good, because it's not clear what we
      // should do otherwise.  Trying again just does back to back GCs.
      // Can't wait for someone else to start a cycle.  And returning fails
      // to meet the goal of ensuring a full collection was performed.
      assert(!op.gc_succeeded() ||
             (old_marking_started_before != old_marking_started_after),
             "invariant: succeeded %s, started before %u, started after %u",
             BOOL_TO_STR(op.gc_succeeded()),
             old_marking_started_before, old_marking_started_after);

      // Request is finished if a full collection (concurrent or stw)
      // was started after this request and has completed, e.g.
      // started_before < completed_after.
      if (gc_counter_less_than(old_marking_started_before,
                               old_marking_completed_after)) {
        LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
        return true;
      }

      if (old_marking_started_after != old_marking_completed_after) {
        // If there is an in-progress cycle (possibly started by us), then
        // wait for that cycle to complete, e.g.
        // while completed_now < started_after.
        LOG_COLLECT_CONCURRENTLY(cause, "wait");
        MonitorLocker ml(G1OldGCCount_lock);
        while (gc_counter_less_than(_old_marking_cycles_completed,
                                    old_marking_started_after)) {
          ml.wait();
        }
        // Request is finished if the collection we just waited for was
        // started after this request.
        if (old_marking_started_before != old_marking_started_after) {
          LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
          return true;
        }
      }

      // If VMOp was successful then it started a new cycle that the above
      // wait &etc should have recognized as finishing this request.  This
      // differs from a non-user-request, where gc_succeeded does not imply
      // a new cycle was started.
      assert(!op.gc_succeeded(), "invariant");

      if (op.cycle_already_in_progress()) {
        // If VMOp failed because a cycle was already in progress, it
        // is now complete.  But it didn't finish this user-requested
        // GC, so try again.
        LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
        continue;
      } else if (op.whitebox_attached()) {
        // If WhiteBox wants control, wait for notification of a state
        // change in the controller, then try again.  Don't wait for
        // release of control, since collections may complete while in
        // control.  Note: This won't recognize a STW full collection
        // while waiting; we can't wait on multiple monitors.
        LOG_COLLECT_CONCURRENTLY(cause, "whitebox control stall");
        MonitorLocker ml(ConcurrentGCBreakpoints::monitor());
        if (ConcurrentGCBreakpoints::is_controlled()) {
          ml.wait();
        }
        continue;
      }
    }

    // Collection failed and should be retried.
    assert(op.transient_failure(), "invariant");

    if (GCLocker::is_active_and_needs_gc()) {
      // If GCLocker is active, wait until clear before retrying.
      LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
      GCLocker::stall_until_clear();
    }

    LOG_COLLECT_CONCURRENTLY(cause, "retry");
  }
}

bool G1CollectedHeap::try_collect(GCCause::Cause cause) {
  assert_heap_not_locked();

  // Lock to get consistent set of values.
  uint gc_count_before;
  uint full_gc_count_before;
  uint old_marking_started_before;
  {
    MutexLocker ml(Heap_lock);
    gc_count_before = total_collections();
    full_gc_count_before = total_full_collections();
    old_marking_started_before = _old_marking_cycles_started;
  }

  if (should_do_concurrent_full_gc(cause)) {
    return try_collect_concurrently(cause,
                                    gc_count_before,
                                    old_marking_started_before);
  } else if (GCLocker::should_discard(cause, gc_count_before)) {
    // Indicate failure to be consistent with VMOp failure due to
    // another collection slipping in after our gc_count but before
    // our request is processed.
    return false;
  } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
             DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {

    // Schedule a standard evacuation pause. We're setting word_size
    // to 0 which means that we are not requesting a post-GC allocation.
    VM_G1CollectForAllocation op(0,     /* word_size */
                                 gc_count_before,
                                 cause,
                                 policy()->max_pause_time_ms());
    VMThread::execute(&op);
    return op.gc_succeeded();
  } else {
    // Schedule a Full GC.
    VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
    VMThread::execute(&op);
    return op.gc_succeeded();
  }
}

bool G1CollectedHeap::is_in(const void* p) const {
  return is_in_reserved(p) && _hrm.is_available(addr_to_region((HeapWord*)p));
}

// Iteration functions.

// Iterates an ObjectClosure over all objects within a HeapRegion.

class IterateObjectClosureRegionClosure: public HeapRegionClosure {
  ObjectClosure* _cl;
public:
  IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
  bool do_heap_region(HeapRegion* r) {
    if (!r->is_continues_humongous()) {
      r->object_iterate(_cl);
    }
    return false;
  }
};

void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
  IterateObjectClosureRegionClosure blk(cl);
  heap_region_iterate(&blk);
}

class G1ParallelObjectIterator : public ParallelObjectIterator {
private:
  G1CollectedHeap*  _heap;
  HeapRegionClaimer _claimer;

public:
  G1ParallelObjectIterator(uint thread_num) :
      _heap(G1CollectedHeap::heap()),
      _claimer(thread_num == 0 ? G1CollectedHeap::heap()->workers()->active_workers() : thread_num) {}

  virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
    _heap->object_iterate_parallel(cl, worker_id, &_claimer);
  }
};

ParallelObjectIterator* G1CollectedHeap::parallel_object_iterator(uint thread_num) {
  return new G1ParallelObjectIterator(thread_num);
}

void G1CollectedHeap::object_iterate_parallel(ObjectClosure* cl, uint worker_id, HeapRegionClaimer* claimer) {
  IterateObjectClosureRegionClosure blk(cl);
  heap_region_par_iterate_from_worker_offset(&blk, claimer, worker_id);
}

void G1CollectedHeap::keep_alive(oop obj) {
  G1BarrierSet::enqueue(obj);
}

void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
  _hrm.iterate(cl);
}

void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
                                                                 HeapRegionClaimer *hrclaimer,
                                                                 uint worker_id) const {
  _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
}

void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
                                                         HeapRegionClaimer *hrclaimer) const {
  _hrm.par_iterate(cl, hrclaimer, 0);
}

void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
  _collection_set.iterate(cl);
}

void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
  _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers());
}

void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
  _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
}

HeapWord* G1CollectedHeap::block_start(const void* addr) const {
  HeapRegion* hr = heap_region_containing(addr);
  return hr->block_start(addr);
}

bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
  HeapRegion* hr = heap_region_containing(addr);
  return hr->block_is_obj(addr);
}

size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
  return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
}

size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
  return _eden.length() * HeapRegion::GrainBytes;
}

// For G1 TLABs should not contain humongous objects, so the maximum TLAB size
// must be equal to the humongous object limit.
size_t G1CollectedHeap::max_tlab_size() const {
  return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
}

size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
  return _allocator->unsafe_max_tlab_alloc();
}

size_t G1CollectedHeap::max_capacity() const {
  return max_regions() * HeapRegion::GrainBytes;
}

void G1CollectedHeap::prepare_for_verify() {
  _verifier->prepare_for_verify();
}

void G1CollectedHeap::verify(VerifyOption vo) {
  _verifier->verify(vo);
}

bool G1CollectedHeap::supports_concurrent_gc_breakpoints() const {
  return true;
}

bool G1CollectedHeap::is_archived_object(oop object) const {
  return object != NULL && heap_region_containing(object)->is_archive();
}

class PrintRegionClosure: public HeapRegionClosure {
  outputStream* _st;
public:
  PrintRegionClosure(outputStream* st) : _st(st) {}
  bool do_heap_region(HeapRegion* r) {
    r->print_on(_st);
    return false;
  }
};

bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
                                       const HeapRegion* hr,
                                       const VerifyOption vo) const {
  switch (vo) {
  case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
  case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
  case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
  default:                            ShouldNotReachHere();
  }
  return false; // keep some compilers happy
}

bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
                                       const VerifyOption vo) const {
  switch (vo) {
  case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
  case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
  case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
  default:                            ShouldNotReachHere();
  }
  return false; // keep some compilers happy
}

void G1CollectedHeap::print_heap_regions() const {
  LogTarget(Trace, gc, heap, region) lt;
  if (lt.is_enabled()) {
    LogStream ls(lt);
    print_regions_on(&ls);
  }
}

void G1CollectedHeap::print_on(outputStream* st) const {
  size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
  st->print(" %-20s", "garbage-first heap");
  st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
            capacity()/K, heap_used/K);
  st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
            p2i(_hrm.reserved().start()),
            p2i(_hrm.reserved().end()));
  st->cr();
  st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
  uint young_regions = young_regions_count();
  st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
            (size_t) young_regions * HeapRegion::GrainBytes / K);
  uint survivor_regions = survivor_regions_count();
  st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
            (size_t) survivor_regions * HeapRegion::GrainBytes / K);
  st->cr();
  if (_numa->is_enabled()) {
    uint num_nodes = _numa->num_active_nodes();
    st->print("  remaining free region(s) on each NUMA node: ");
    const int* node_ids = _numa->node_ids();
    for (uint node_index = 0; node_index < num_nodes; node_index++) {
      uint num_free_regions = _hrm.num_free_regions(node_index);
      st->print("%d=%u ", node_ids[node_index], num_free_regions);
    }
    st->cr();
  }
  MetaspaceUtils::print_on(st);
}

void G1CollectedHeap::print_regions_on(outputStream* st) const {
  st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
               "HS=humongous(starts), HC=humongous(continues), "
               "CS=collection set, F=free, "
               "OA=open archive, CA=closed archive, "
               "TAMS=top-at-mark-start (previous, next)");
  PrintRegionClosure blk(st);
  heap_region_iterate(&blk);
}

void G1CollectedHeap::print_extended_on(outputStream* st) const {
  print_on(st);

  // Print the per-region information.
  st->cr();
  print_regions_on(st);
}

void G1CollectedHeap::print_on_error(outputStream* st) const {
  this->CollectedHeap::print_on_error(st);

  if (_cm != NULL) {
    st->cr();
    _cm->print_on_error(st);
  }
}

void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
  workers()->threads_do(tc);
  tc->do_thread(_cm_thread);
  _cm->threads_do(tc);
  _cr->threads_do(tc);
  tc->do_thread(_service_thread);
}

void G1CollectedHeap::print_tracing_info() const {
  rem_set()->print_summary_info();
  concurrent_mark()->print_summary_info();
}

#ifndef PRODUCT
// Helpful for debugging RSet issues.

class PrintRSetsClosure : public HeapRegionClosure {
private:
  const char* _msg;
  size_t _occupied_sum;

public:
  bool do_heap_region(HeapRegion* r) {
    HeapRegionRemSet* hrrs = r->rem_set();
    size_t occupied = hrrs->occupied();
    _occupied_sum += occupied;

    tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
    if (occupied == 0) {
      tty->print_cr("  RSet is empty");
    } else {
      hrrs->print();
    }
    tty->print_cr("----------");
    return false;
  }

  PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
    tty->cr();
    tty->print_cr("========================================");
    tty->print_cr("%s", msg);
    tty->cr();
  }

  ~PrintRSetsClosure() {
    tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
    tty->print_cr("========================================");
    tty->cr();
  }
};

void G1CollectedHeap::print_cset_rsets() {
  PrintRSetsClosure cl("Printing CSet RSets");
  collection_set_iterate_all(&cl);
}

void G1CollectedHeap::print_all_rsets() {
  PrintRSetsClosure cl("Printing All RSets");;
  heap_region_iterate(&cl);
}
#endif // PRODUCT

bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
  return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
}

G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {

  size_t eden_used_bytes = _eden.used_bytes();
  size_t survivor_used_bytes = _survivor.used_bytes();
  size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();

  size_t eden_capacity_bytes =
    (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;

  VirtualSpaceSummary heap_summary = create_heap_space_summary();
  return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
                       eden_capacity_bytes, survivor_used_bytes, num_regions());
}

G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
  return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
                       stats->unused(), stats->used(), stats->region_end_waste(),
                       stats->regions_filled(), stats->direct_allocated(),
                       stats->failure_used(), stats->failure_waste());
}

void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
  const G1HeapSummary& heap_summary = create_g1_heap_summary();
  gc_tracer->report_gc_heap_summary(when, heap_summary);

  const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
  gc_tracer->report_metaspace_summary(when, metaspace_summary);
}

void G1CollectedHeap::gc_prologue(bool full) {
  assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");

  // This summary needs to be printed before incrementing total collections.
  rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());

  // Update common counters.
  increment_total_collections(full /* full gc */);
  if (full || collector_state()->in_concurrent_start_gc()) {
    increment_old_marking_cycles_started();
  }

  // Fill TLAB's and such
  {
    Ticks start = Ticks::now();
    ensure_parsability(true);
    Tickspan dt = Ticks::now() - start;
    phase_times()->record_prepare_tlab_time_ms(dt.seconds() * MILLIUNITS);
  }

  if (!full) {
    // Flush dirty card queues to qset, so later phases don't need to account
    // for partially filled per-thread queues and such.  Not needed for full
    // collections, which ignore those logs.
    Ticks start = Ticks::now();
    G1BarrierSet::dirty_card_queue_set().concatenate_logs();
    Tickspan dt = Ticks::now() - start;
    phase_times()->record_concatenate_dirty_card_logs_time_ms(dt.seconds() * MILLIUNITS);
  }
}

void G1CollectedHeap::gc_epilogue(bool full) {
  // Update common counters.
  if (full) {
    // Update the number of full collections that have been completed.
    increment_old_marking_cycles_completed(false /* concurrent */, true /* liveness_completed */);
  }

  // We are at the end of the GC. Total collections has already been increased.
  rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);

#if COMPILER2_OR_JVMCI
  assert(DerivedPointerTable::is_empty(), "derived pointer present");
#endif

  double start = os::elapsedTime();
  resize_all_tlabs();
  phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);

  MemoryService::track_memory_usage();
  // We have just completed a GC. Update the soft reference
  // policy with the new heap occupancy
  Universe::heap()->update_capacity_and_used_at_gc();

  // Print NUMA statistics.
  _numa->print_statistics();

  _collection_pause_end = Ticks::now();

  _free_card_set_memory_task->notify_new_stats(&_young_gen_card_set_stats,
                                               &_collection_set_candidates_card_set_stats);
}

uint G1CollectedHeap::uncommit_regions(uint region_limit) {
  return _hrm.uncommit_inactive_regions(region_limit);
}

bool G1CollectedHeap::has_uncommittable_regions() {
  return _hrm.has_inactive_regions();
}

void G1CollectedHeap::uncommit_regions_if_necessary() {
  if (has_uncommittable_regions()) {
    G1UncommitRegionTask::enqueue();
  }
}

void G1CollectedHeap::verify_numa_regions(const char* desc) {
  LogTarget(Trace, gc, heap, verify) lt;

  if (lt.is_enabled()) {
    LogStream ls(lt);
    // Iterate all heap regions to print matching between preferred numa id and actual numa id.
    G1NodeIndexCheckClosure cl(desc, _numa, &ls);
    heap_region_iterate(&cl);
  }
}

HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
                                               uint gc_count_before,
                                               bool* succeeded,
                                               GCCause::Cause gc_cause) {
  assert_heap_not_locked_and_not_at_safepoint();
  VM_G1CollectForAllocation op(word_size,
                               gc_count_before,
                               gc_cause,
                               policy()->max_pause_time_ms());
  VMThread::execute(&op);

  HeapWord* result = op.result();
  bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
  assert(result == NULL || ret_succeeded,
         "the result should be NULL if the VM did not succeed");
  *succeeded = ret_succeeded;

  assert_heap_not_locked();
  return result;
}

void G1CollectedHeap::start_concurrent_cycle(bool concurrent_operation_is_full_mark) {
  assert(!_cm_thread->in_progress(), "Can not start concurrent operation while in progress");

  MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
  if (concurrent_operation_is_full_mark) {
    _cm->post_concurrent_mark_start();
    _cm_thread->start_full_mark();
  } else {
    _cm->post_concurrent_undo_start();
    _cm_thread->start_undo_mark();
  }
  CGC_lock->notify();
}

bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
  // We don't nominate objects with many remembered set entries, on
  // the assumption that such objects are likely still live.
  HeapRegionRemSet* rem_set = r->rem_set();

  return G1EagerReclaimHumongousObjectsWithStaleRefs ?
         rem_set->occupancy_less_or_equal_than(G1EagerReclaimRemSetThreshold) :
         G1EagerReclaimHumongousObjects && rem_set->is_empty();
}

#ifndef PRODUCT
void G1CollectedHeap::verify_region_attr_remset_update() {
  class VerifyRegionAttrRemSet : public HeapRegionClosure {
  public:
    virtual bool do_heap_region(HeapRegion* r) {
      G1CollectedHeap* g1h = G1CollectedHeap::heap();
      bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
      assert(r->rem_set()->is_tracked() == needs_remset_update,
             "Region %u remset tracking status (%s) different to region attribute (%s)",
             r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
      return false;
    }
  } cl;
  heap_region_iterate(&cl);
}
#endif

class VerifyRegionRemSetClosure : public HeapRegionClosure {
  public:
    bool do_heap_region(HeapRegion* hr) {
      if (!hr->is_archive() && !hr->is_continues_humongous()) {
        hr->verify_rem_set();
      }
      return false;
    }
};

uint G1CollectedHeap::num_task_queues() const {
  return _task_queues->size();
}

#if TASKQUEUE_STATS
void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
  st->print_raw_cr("GC Task Stats");
  st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
  st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
}

void G1CollectedHeap::print_taskqueue_stats() const {
  if (!log_is_enabled(Trace, gc, task, stats)) {
    return;
  }
  Log(gc, task, stats) log;
  ResourceMark rm;
  LogStream ls(log.trace());
  outputStream* st = &ls;

  print_taskqueue_stats_hdr(st);

  TaskQueueStats totals;
  const uint n = num_task_queues();
  for (uint i = 0; i < n; ++i) {
    st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
    totals += task_queue(i)->stats;
  }
  st->print_raw("tot "); totals.print(st); st->cr();

  DEBUG_ONLY(totals.verify());
}

void G1CollectedHeap::reset_taskqueue_stats() {
  const uint n = num_task_queues();
  for (uint i = 0; i < n; ++i) {
    task_queue(i)->stats.reset();
  }
}
#endif // TASKQUEUE_STATS

void G1CollectedHeap::wait_for_root_region_scanning() {
  double scan_wait_start = os::elapsedTime();
  // We have to wait until the CM threads finish scanning the
  // root regions as it's the only way to ensure that all the
  // objects on them have been correctly scanned before we start
  // moving them during the GC.
  bool waited = _cm->root_regions()->wait_until_scan_finished();
  double wait_time_ms = 0.0;
  if (waited) {
    double scan_wait_end = os::elapsedTime();
    wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
  }
  phase_times()->record_root_region_scan_wait_time(wait_time_ms);
}

class G1PrintCollectionSetClosure : public HeapRegionClosure {
private:
  G1HRPrinter* _hr_printer;
public:
  G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }

  virtual bool do_heap_region(HeapRegion* r) {
    _hr_printer->cset(r);
    return false;
  }
};

void G1CollectedHeap::start_new_collection_set() {
  double start = os::elapsedTime();

  collection_set()->start_incremental_building();

  clear_region_attr();

  guarantee(_eden.length() == 0, "eden should have been cleared");
  policy()->transfer_survivors_to_cset(survivor());

  // We redo the verification but now wrt to the new CSet which
  // has just got initialized after the previous CSet was freed.
  _cm->verify_no_collection_set_oops();

  phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
}

void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {

  _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
  evacuation_info.set_collectionset_regions(collection_set()->region_length() +
                                            collection_set()->optional_region_length());

  _cm->verify_no_collection_set_oops();

  if (_hr_printer.is_active()) {
    G1PrintCollectionSetClosure cl(&_hr_printer);
    _collection_set.iterate(&cl);
    _collection_set.iterate_optional(&cl);
  }
}

G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
  if (collector_state()->in_concurrent_start_gc()) {
    return G1HeapVerifier::G1VerifyConcurrentStart;
  } else if (collector_state()->in_young_only_phase()) {
    return G1HeapVerifier::G1VerifyYoungNormal;
  } else {
    return G1HeapVerifier::G1VerifyMixed;
  }
}

void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
  if (VerifyRememberedSets) {
    log_info(gc, verify)("[Verifying RemSets before GC]");
    VerifyRegionRemSetClosure v_cl;
    heap_region_iterate(&v_cl);
  }
  _verifier->verify_before_gc(type);
  _verifier->check_bitmaps("GC Start");
  verify_numa_regions("GC Start");
}

void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
  if (evacuation_failed()) {
    type = (G1HeapVerifier::G1VerifyType)(type | G1HeapVerifier::G1VerifyYoungEvacFail);
  }
  if (VerifyRememberedSets) {
    log_info(gc, verify)("[Verifying RemSets after GC]");
    VerifyRegionRemSetClosure v_cl;
    heap_region_iterate(&v_cl);
  }
  _verifier->verify_after_gc(type);
  _verifier->check_bitmaps("GC End");
  verify_numa_regions("GC End");
}

void G1CollectedHeap::expand_heap_after_young_collection(){
  size_t expand_bytes = _heap_sizing_policy->young_collection_expansion_amount();
  if (expand_bytes > 0) {
    // No need for an ergo logging here,
    // expansion_amount() does this when it returns a value > 0.
    double expand_ms = 0.0;
    if (!expand(expand_bytes, _workers, &expand_ms)) {
      // We failed to expand the heap. Cannot do anything about it.
    }
    phase_times()->record_expand_heap_time(expand_ms);
  }
}

bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
  assert_at_safepoint_on_vm_thread();
  guarantee(!is_gc_active(), "collection is not reentrant");

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

  do_collection_pause_at_safepoint_helper(target_pause_time_ms);
  return true;
}

void G1CollectedHeap::gc_tracer_report_gc_start() {
  _gc_timer_stw->register_gc_start();
  _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
}

void G1CollectedHeap::gc_tracer_report_gc_end(bool concurrent_operation_is_full_mark,
                                              G1EvacuationInfo& evacuation_info) {
  _gc_tracer_stw->report_evacuation_info(&evacuation_info);
  _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());

  _gc_timer_stw->register_gc_end();
  _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(),
  _gc_timer_stw->time_partitions());
}

// GCTraceTime wrapper that constructs the message according to GC pause type and
// GC cause.
class G1YoungGCTraceTime {
  G1GCPauseType _pause_type;

  static const uint MaxYoungGCNameLength = 128;
  char _young_gc_name_data[MaxYoungGCNameLength];

  GCTraceTime(Info, gc) _tt;

  char* update_young_gc_name() {
    snprintf(_young_gc_name_data,
             MaxYoungGCNameLength,
             "Pause Young (%s)%s",
             G1GCPauseTypeHelper::to_string(_pause_type),
             G1CollectedHeap::heap()->evacuation_failed() ? " (Evacuation Failure)" : "");
    return _young_gc_name_data;
  }

public:

  G1YoungGCTraceTime(GCCause::Cause cause) :
    // Take snapshot of current pause type at start as it may be modified during gc.
    // The strings for all Concurrent Start pauses are the same, so the parameter
    // does not matter here.
    _pause_type(G1CollectedHeap::heap()->collector_state()->young_gc_pause_type(false /* concurrent_operation_is_full_mark */)),
    _tt(update_young_gc_name(), NULL, cause, true) {
  }

  ~G1YoungGCTraceTime() {
    update_young_gc_name();
  }
};

void G1CollectedHeap::do_collection_pause_at_safepoint_helper(double target_pause_time_ms) {
  GCIdMark gc_id_mark;

  SvcGCMarker sgcm(SvcGCMarker::MINOR);
  ResourceMark rm;

  policy()->note_gc_start();

  gc_tracer_report_gc_start();

  wait_for_root_region_scanning();

  print_heap_before_gc();
  print_heap_regions();
  trace_heap_before_gc(_gc_tracer_stw);

  _verifier->verify_region_sets_optional();
  _verifier->verify_dirty_young_regions();

  // We should not be doing concurrent start unless the concurrent mark thread is running
  if (!_cm_thread->should_terminate()) {
    // This call will decide whether this pause is a concurrent start
    // pause. If it is, in_concurrent_start_gc() will return true
    // for the duration of this pause.
    policy()->decide_on_conc_mark_initiation();
  }

  // We do not allow concurrent start to be piggy-backed on a mixed GC.
  assert(!collector_state()->in_concurrent_start_gc() ||
         collector_state()->in_young_only_phase(), "sanity");
  // We also do not allow mixed GCs during marking.
  assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");

  // Record whether this pause may need to trigger a concurrent operation. Later,
  // when we signal the G1ConcurrentMarkThread, the collector state has already
  // been reset for the next pause.
  bool should_start_concurrent_mark_operation = collector_state()->in_concurrent_start_gc();
  bool concurrent_operation_is_full_mark = false;

  // Inner scope for scope based logging, timers, and stats collection
  {
    G1EvacuationInfo evacuation_info;

    GCTraceCPUTime tcpu;

    G1YoungGCTraceTime tm(gc_cause());

    uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
                                                            workers()->active_workers(),
                                                            Threads::number_of_non_daemon_threads());
    active_workers = workers()->update_active_workers(active_workers);
    log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
    G1MonitoringScope ms(g1mm(),
                         false /* full_gc */,
                         collector_state()->in_mixed_phase() /* all_memory_pools_affected */);

    G1HeapTransition heap_transition(this);

    {
      IsGCActiveMark x;
      gc_prologue(false);

      G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
      verify_before_young_collection(verify_type);
      {
        // The elapsed time induced by the start time below deliberately elides
        // the possible verification above.
        double sample_start_time_sec = os::elapsedTime();

        // Please see comment in g1CollectedHeap.hpp and
        // G1CollectedHeap::ref_processing_init() to see how
        // reference processing currently works in G1.
        _ref_processor_stw->enable_discovery();

        // We want to temporarily turn off discovery by the
        // CM ref processor, if necessary, and turn it back on
        // on again later if we do. Using a scoped
        // NoRefDiscovery object will do this.
        NoRefDiscovery no_cm_discovery(_ref_processor_cm);

        policy()->record_collection_pause_start(sample_start_time_sec);

        // Forget the current allocation region (we might even choose it to be part
        // of the collection set!).
        _allocator->release_mutator_alloc_regions();

        calculate_collection_set(evacuation_info, target_pause_time_ms);

        G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
        G1ParScanThreadStateSet per_thread_states(this,
                                                  &rdcqs,
                                                  workers()->active_workers(),
                                                  collection_set()->young_region_length(),
                                                  collection_set()->optional_region_length());
        pre_evacuate_collection_set(evacuation_info, &per_thread_states);

        bool may_do_optional_evacuation = _collection_set.optional_region_length() != 0;
        // Actually do the work...
        evacuate_initial_collection_set(&per_thread_states, may_do_optional_evacuation);

        if (may_do_optional_evacuation) {
          evacuate_optional_collection_set(&per_thread_states);
        }
        post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);

        start_new_collection_set();

        _survivor_evac_stats.adjust_desired_plab_sz();
        _old_evac_stats.adjust_desired_plab_sz();

        allocate_dummy_regions();

        _allocator->init_mutator_alloc_regions();

        expand_heap_after_young_collection();

        // Refine the type of a concurrent mark operation now that we did the
        // evacuation, eventually aborting it.
        concurrent_operation_is_full_mark = policy()->concurrent_operation_is_full_mark("Revise IHOP");

        // Need to report the collection pause now since record_collection_pause_end()
        // modifies it to the next state.
        _gc_tracer_stw->report_young_gc_pause(collector_state()->young_gc_pause_type(concurrent_operation_is_full_mark));

        double sample_end_time_sec = os::elapsedTime();
        double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
        policy()->record_collection_pause_end(pause_time_ms, concurrent_operation_is_full_mark);
      }

      verify_after_young_collection(verify_type);

      gc_epilogue(false);
    }

    policy()->print_phases();
    heap_transition.print();

    _hrm.verify_optional();
    _verifier->verify_region_sets_optional();

    TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
    TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());

    print_heap_after_gc();
    print_heap_regions();
    trace_heap_after_gc(_gc_tracer_stw);

    gc_tracer_report_gc_end(concurrent_operation_is_full_mark, evacuation_info);
  }
  // It should now be safe to tell the concurrent mark thread to start
  // without its logging output interfering with the logging output
  // that came from the pause.

  if (should_start_concurrent_mark_operation) {
    // CAUTION: after the start_concurrent_cycle() call below, the concurrent marking
    // thread(s) could be running concurrently with us. Make sure that anything
    // after this point does not assume that we are the only GC thread running.
    // Note: of course, the actual marking work will not start until the safepoint
    // itself is released in SuspendibleThreadSet::desynchronize().
    start_concurrent_cycle(concurrent_operation_is_full_mark);
    ConcurrentGCBreakpoints::notify_idle_to_active();
  }
}

void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
  _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
  _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
}

bool G1ParEvacuateFollowersClosure::offer_termination() {
  EventGCPhaseParallel event;
  G1ParScanThreadState* const pss = par_scan_state();
  start_term_time();
  const bool res = (terminator() == nullptr) ? true : terminator()->offer_termination();
  end_term_time();
  event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
  return res;
}

void G1ParEvacuateFollowersClosure::do_void() {
  EventGCPhaseParallel event;
  G1ParScanThreadState* const pss = par_scan_state();
  pss->trim_queue();
  event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
  do {
    EventGCPhaseParallel event;
    pss->steal_and_trim_queue(queues());
    event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
  } while (!offer_termination());
}

void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
                                        bool class_unloading_occurred) {
  uint num_workers = workers()->active_workers();
  G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred);
  workers()->run_task(&unlink_task);
}

// Weak Reference Processing support

bool G1STWIsAliveClosure::do_object_b(oop p) {
  // An object is reachable if it is outside the collection set,
  // or is inside and copied.
  return !_g1h->is_in_cset(p) || p->is_forwarded();
}

bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
  assert(obj != NULL, "must not be NULL");
  assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
  // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
  // may falsely indicate that this is not the case here: however the collection set only
  // contains old regions when concurrent mark is not running.
  return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
}

// Non Copying Keep Alive closure
class G1KeepAliveClosure: public OopClosure {
  G1CollectedHeap*_g1h;
public:
  G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
  void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
  void do_oop(oop* p) {
    oop obj = *p;
    assert(obj != NULL, "the caller should have filtered out NULL values");

    const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
    if (!region_attr.is_in_cset_or_humongous()) {
      return;
    }
    if (region_attr.is_in_cset()) {
      assert( obj->is_forwarded(), "invariant" );
      *p = obj->forwardee();
    } else {
      assert(!obj->is_forwarded(), "invariant" );
      assert(region_attr.is_humongous(),
             "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
     _g1h->set_humongous_is_live(obj);
    }
  }
};

// Copying Keep Alive closure - can be called from both
// serial and parallel code as long as different worker
// threads utilize different G1ParScanThreadState instances
// and different queues.

class G1CopyingKeepAliveClosure: public OopClosure {
  G1CollectedHeap*         _g1h;
  G1ParScanThreadState*    _par_scan_state;

public:
  G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
                            G1ParScanThreadState* pss):
    _g1h(g1h),
    _par_scan_state(pss)
  {}

  virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  virtual void do_oop(      oop* p) { do_oop_work(p); }

  template <class T> void do_oop_work(T* p) {
    oop obj = RawAccess<>::oop_load(p);

    if (_g1h->is_in_cset_or_humongous(obj)) {
      // If the referent object has been forwarded (either copied
      // to a new location or to itself in the event of an
      // evacuation failure) then we need to update the reference
      // field and, if both reference and referent are in the G1
      // heap, update the RSet for the referent.
      //
      // If the referent has not been forwarded then we have to keep
      // it alive by policy. Therefore we have copy the referent.
      //
      // When the queue is drained (after each phase of reference processing)
      // the object and it's followers will be copied, the reference field set
      // to point to the new location, and the RSet updated.
      _par_scan_state->push_on_queue(ScannerTask(p));
    }
  }
};

// Serial drain queue closure. Called as the 'complete_gc'
// closure for each discovered list in some of the
// reference processing phases.

class G1STWDrainQueueClosure: public VoidClosure {
protected:
  G1CollectedHeap* _g1h;
  G1ParScanThreadState* _par_scan_state;

  G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }

public:
  G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
    _g1h(g1h),
    _par_scan_state(pss)
  { }

  void do_void() {
    G1ParScanThreadState* const pss = par_scan_state();
    pss->trim_queue();
  }
};

class G1STWRefProcProxyTask : public RefProcProxyTask {
  G1CollectedHeap& _g1h;
  G1ParScanThreadStateSet& _pss;
  TaskTerminator _terminator;
  G1ScannerTasksQueueSet& _task_queues;

public:
  G1STWRefProcProxyTask(uint max_workers, G1CollectedHeap& g1h, G1ParScanThreadStateSet& pss, G1ScannerTasksQueueSet& task_queues)
    : RefProcProxyTask("G1STWRefProcProxyTask", max_workers),
      _g1h(g1h),
      _pss(pss),
      _terminator(max_workers, &task_queues),
      _task_queues(task_queues) {}

  void work(uint worker_id) override {
    assert(worker_id < _max_workers, "sanity");
    uint index = (_tm == RefProcThreadModel::Single) ? 0 : worker_id;
    _pss.state_for_worker(index)->set_ref_discoverer(nullptr);
    G1STWIsAliveClosure is_alive(&_g1h);
    G1CopyingKeepAliveClosure keep_alive(&_g1h, _pss.state_for_worker(index));
    G1ParEvacuateFollowersClosure complete_gc(&_g1h, _pss.state_for_worker(index), &_task_queues, _tm == RefProcThreadModel::Single ? nullptr : &_terminator, G1GCPhaseTimes::ObjCopy);
    _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &complete_gc);
  }

  void prepare_run_task_hook() override {
    _terminator.reset_for_reuse(_queue_count);
  }
};

// End of weak reference support closures

void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
  double ref_proc_start = os::elapsedTime();

  ReferenceProcessor* rp = _ref_processor_stw;
  assert(rp->discovery_enabled(), "should have been enabled");

  // Use only a single queue for this PSS.
  G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
  pss->set_ref_discoverer(NULL);
  assert(pss->queue_is_empty(), "pre-condition");

  // Setup the soft refs policy...
  rp->setup_policy(false);

  ReferenceProcessorPhaseTimes& pt = *phase_times()->ref_phase_times();

  ReferenceProcessorStats stats;
  uint no_of_gc_workers = workers()->active_workers();

  // Parallel reference processing
  assert(no_of_gc_workers <= rp->max_num_queues(),
         "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
         no_of_gc_workers,  rp->max_num_queues());

  rp->set_active_mt_degree(no_of_gc_workers);
  G1STWRefProcProxyTask task(rp->max_num_queues(), *this, *per_thread_states, *_task_queues);
  stats = rp->process_discovered_references(task, pt);

  _gc_tracer_stw->report_gc_reference_stats(stats);

  // We have completed copying any necessary live referent objects.
  assert(pss->queue_is_empty(), "both queue and overflow should be empty");

  make_pending_list_reachable();

  assert(!rp->discovery_enabled(), "Postcondition");
  rp->verify_no_references_recorded();

  double ref_proc_time = os::elapsedTime() - ref_proc_start;
  phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
}

void G1CollectedHeap::make_pending_list_reachable() {
  if (collector_state()->in_concurrent_start_gc()) {
    oop pll_head = Universe::reference_pending_list();
    if (pll_head != NULL) {
      // Any valid worker id is fine here as we are in the VM thread and single-threaded.
      _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
    }
  }
}

static bool do_humongous_object_logging() {
  return log_is_enabled(Debug, gc, humongous);
}

bool G1CollectedHeap::should_do_eager_reclaim() const {
  // As eager reclaim logging also gives information about humongous objects in
  // the heap in general, always do the eager reclaim pass even without known
  // candidates.
  return (G1EagerReclaimHumongousObjects &&
          (has_humongous_reclaim_candidates() || do_humongous_object_logging()));
}

bool G1CollectedHeap::should_sample_collection_set_candidates() const {
  G1CollectionSetCandidates* candidates = G1CollectedHeap::heap()->collection_set()->candidates();
  return candidates != NULL && candidates->num_remaining() > 0;
}

void G1CollectedHeap::set_collection_set_candidates_stats(G1CardSetMemoryStats& stats) {
  _collection_set_candidates_card_set_stats = stats;
}

class G1PrepareEvacuationTask : public AbstractGangTask {
  class G1PrepareRegionsClosure : public HeapRegionClosure {
    G1CollectedHeap* _g1h;
    G1PrepareEvacuationTask* _parent_task;
    uint _worker_humongous_total;
    uint _worker_humongous_candidates;

    G1CardSetMemoryStats _card_set_stats;

    void sample_card_set_size(HeapRegion* hr) {
      // Sample card set sizes for young gen and humongous before GC: this makes
      // the policy to give back memory to the OS keep the most recent amount of
      // memory for these regions.
      if (hr->is_young() || hr->is_starts_humongous()) {
        _card_set_stats.add(hr->rem_set()->card_set_memory_stats());
      }
    }

    bool humongous_region_is_candidate(HeapRegion* region) const {
      assert(region->is_starts_humongous(), "Must start a humongous object");

      oop obj = cast_to_oop(region->bottom());

      // Dead objects cannot be eager reclaim candidates. Due to class
      // unloading it is unsafe to query their classes so we return early.
      if (_g1h->is_obj_dead(obj, region)) {
        return false;
      }

      // If we do not have a complete remembered set for the region, then we can
      // not be sure that we have all references to it.
      if (!region->rem_set()->is_complete()) {
        return false;
      }
      // Candidate selection must satisfy the following constraints
      // while concurrent marking is in progress:
      //
      // * In order to maintain SATB invariants, an object must not be
      // reclaimed if it was allocated before the start of marking and
      // has not had its references scanned.  Such an object must have
      // its references (including type metadata) scanned to ensure no
      // live objects are missed by the marking process.  Objects
      // allocated after the start of concurrent marking don't need to
      // be scanned.
      //
      // * An object must not be reclaimed if it is on the concurrent
      // mark stack.  Objects allocated after the start of concurrent
      // marking are never pushed on the mark stack.
      //
      // Nominating only objects allocated after the start of concurrent
      // marking is sufficient to meet both constraints.  This may miss
      // some objects that satisfy the constraints, but the marking data
      // structures don't support efficiently performing the needed
      // additional tests or scrubbing of the mark stack.
      //
      // However, we presently only nominate is_typeArray() objects.
      // A humongous object containing references induces remembered
      // set entries on other regions.  In order to reclaim such an
      // object, those remembered sets would need to be cleaned up.
      //
      // We also treat is_typeArray() objects specially, allowing them
      // to be reclaimed even if allocated before the start of
      // concurrent mark.  For this we rely on mark stack insertion to
      // exclude is_typeArray() objects, preventing reclaiming an object
      // that is in the mark stack.  We also rely on the metadata for
      // such objects to be built-in and so ensured to be kept live.
      // Frequent allocation and drop of large binary blobs is an
      // important use case for eager reclaim, and this special handling
      // may reduce needed headroom.

      return obj->is_typeArray() &&
             _g1h->is_potential_eager_reclaim_candidate(region);
    }

  public:
    G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) :
      _g1h(g1h),
      _parent_task(parent_task),
      _worker_humongous_total(0),
      _worker_humongous_candidates(0) { }

    ~G1PrepareRegionsClosure() {
      _parent_task->add_humongous_candidates(_worker_humongous_candidates);
      _parent_task->add_humongous_total(_worker_humongous_total);
    }

    virtual bool do_heap_region(HeapRegion* hr) {
      // First prepare the region for scanning
      _g1h->rem_set()->prepare_region_for_scan(hr);

      sample_card_set_size(hr);

      // Now check if region is a humongous candidate
      if (!hr->is_starts_humongous()) {
        _g1h->register_region_with_region_attr(hr);
        return false;
      }

      uint index = hr->hrm_index();
      if (humongous_region_is_candidate(hr)) {
        _g1h->set_humongous_reclaim_candidate(index, true);
        _g1h->register_humongous_region_with_region_attr(index);
        _worker_humongous_candidates++;
        // We will later handle the remembered sets of these regions.
      } else {
        _g1h->set_humongous_reclaim_candidate(index, false);
        _g1h->register_region_with_region_attr(hr);
      }
      log_debug(gc, humongous)("Humongous region %u (object size " SIZE_FORMAT " @ " PTR_FORMAT ") remset " SIZE_FORMAT " code roots " SIZE_FORMAT " marked %d reclaim candidate %d type array %d",
                               index,
                               (size_t)cast_to_oop(hr->bottom())->size() * HeapWordSize,
                               p2i(hr->bottom()),
                               hr->rem_set()->occupied(),
                               hr->rem_set()->strong_code_roots_list_length(),
                               _g1h->concurrent_mark()->next_mark_bitmap()->is_marked(hr->bottom()),
                               _g1h->is_humongous_reclaim_candidate(index),
                               cast_to_oop(hr->bottom())->is_typeArray()
                              );
      _worker_humongous_total++;

      return false;
    }

    G1CardSetMemoryStats card_set_stats() const {
      return _card_set_stats;
    }
  };

  G1CollectedHeap* _g1h;
  HeapRegionClaimer _claimer;
  volatile uint _humongous_total;
  volatile uint _humongous_candidates;

  G1CardSetMemoryStats _all_card_set_stats;

public:
  G1PrepareEvacuationTask(G1CollectedHeap* g1h) :
    AbstractGangTask("Prepare Evacuation"),
    _g1h(g1h),
    _claimer(_g1h->workers()->active_workers()),
    _humongous_total(0),
    _humongous_candidates(0) { }

  void work(uint worker_id) {
    G1PrepareRegionsClosure cl(_g1h, this);
    _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id);

    MutexLocker x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
    _all_card_set_stats.add(cl.card_set_stats());
  }

  void add_humongous_candidates(uint candidates) {
    Atomic::add(&_humongous_candidates, candidates);
  }

  void add_humongous_total(uint total) {
    Atomic::add(&_humongous_total, total);
  }

  uint humongous_candidates() {
    return _humongous_candidates;
  }

  uint humongous_total() {
    return _humongous_total;
  }

  G1CardSetMemoryStats all_card_set_stats() const {
    return _all_card_set_stats;
  }
};

void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
  _bytes_used_during_gc = 0;

  _expand_heap_after_alloc_failure = true;
  Atomic::store(&_num_regions_failed_evacuation, 0u);

  _regions_failed_evacuation.clear();

  // Disable the hot card cache.
  _hot_card_cache->reset_hot_cache_claimed_index();
  _hot_card_cache->set_use_cache(false);

  // Initialize the GC alloc regions.
  _allocator->init_gc_alloc_regions(evacuation_info);

  {
    Ticks start = Ticks::now();
    rem_set()->prepare_for_scan_heap_roots();
    phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
  }

  {
    G1PrepareEvacuationTask g1_prep_task(this);
    Tickspan task_time = run_task_timed(&g1_prep_task);

    _young_gen_card_set_stats = g1_prep_task.all_card_set_stats();

    phase_times()->record_register_regions(task_time.seconds() * 1000.0);
    _num_humongous_objects = g1_prep_task.humongous_total();
    _num_humongous_reclaim_candidates = g1_prep_task.humongous_candidates();
  }

  assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
  _preserved_marks_set.assert_empty();

#if COMPILER2_OR_JVMCI
  DerivedPointerTable::clear();
#endif

  // Concurrent start needs claim bits to keep track of the marked-through CLDs.
  if (collector_state()->in_concurrent_start_gc()) {
    concurrent_mark()->pre_concurrent_start(gc_cause());

    double start_clear_claimed_marks = os::elapsedTime();

    ClassLoaderDataGraph::clear_claimed_marks();

    double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
    phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
  }

  // Should G1EvacuationFailureALot be in effect for this GC?
  NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
}

class G1EvacuateRegionsBaseTask : public AbstractGangTask {
protected:
  G1CollectedHeap* _g1h;
  G1ParScanThreadStateSet* _per_thread_states;
  G1ScannerTasksQueueSet* _task_queues;
  TaskTerminator _terminator;
  uint _num_workers;

  void evacuate_live_objects(G1ParScanThreadState* pss,
                             uint worker_id,
                             G1GCPhaseTimes::GCParPhases objcopy_phase,
                             G1GCPhaseTimes::GCParPhases termination_phase) {
    G1GCPhaseTimes* p = _g1h->phase_times();

    Ticks start = Ticks::now();
    G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, &_terminator, objcopy_phase);
    cl.do_void();

    assert(pss->queue_is_empty(), "should be empty");

    Tickspan evac_time = (Ticks::now() - start);
    p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());

    if (termination_phase == G1GCPhaseTimes::Termination) {
      p->record_time_secs(termination_phase, worker_id, cl.term_time());
      p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
    } else {
      p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
      p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
    }
    assert(pss->trim_ticks().value() == 0,
           "Unexpected partial trimming during evacuation value " JLONG_FORMAT,
           pss->trim_ticks().value());
  }

  virtual void start_work(uint worker_id) { }

  virtual void end_work(uint worker_id) { }

  virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;

  virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;

public:
  G1EvacuateRegionsBaseTask(const char* name,
                            G1ParScanThreadStateSet* per_thread_states,
                            G1ScannerTasksQueueSet* task_queues,
                            uint num_workers) :
    AbstractGangTask(name),
    _g1h(G1CollectedHeap::heap()),
    _per_thread_states(per_thread_states),
    _task_queues(task_queues),
    _terminator(num_workers, _task_queues),
    _num_workers(num_workers)
  { }

  void work(uint worker_id) {
    start_work(worker_id);

    {
      ResourceMark rm;

      G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
      pss->set_ref_discoverer(_g1h->ref_processor_stw());

      scan_roots(pss, worker_id);
      evacuate_live_objects(pss, worker_id);
    }

    end_work(worker_id);
  }
};

class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
  G1RootProcessor* _root_processor;
  bool _has_optional_evacuation_work;

  void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
    _root_processor->evacuate_roots(pss, worker_id);
    _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy, _has_optional_evacuation_work);
    _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
  }

  void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
    G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
  }

  void start_work(uint worker_id) {
    _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
  }

  void end_work(uint worker_id) {
    _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
  }

public:
  G1EvacuateRegionsTask(G1CollectedHeap* g1h,
                        G1ParScanThreadStateSet* per_thread_states,
                        G1ScannerTasksQueueSet* task_queues,
                        G1RootProcessor* root_processor,
                        uint num_workers,
                        bool has_optional_evacuation_work) :
    G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
    _root_processor(root_processor),
    _has_optional_evacuation_work(has_optional_evacuation_work)
  { }
};

void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states,
                                                      bool has_optional_evacuation_work) {
  G1GCPhaseTimes* p = phase_times();

  {
    Ticks start = Ticks::now();
    rem_set()->merge_heap_roots(true /* initial_evacuation */);
    p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
  }

  Tickspan task_time;
  const uint num_workers = workers()->active_workers();

  Ticks start_processing = Ticks::now();
  {
    G1RootProcessor root_processor(this, num_workers);
    G1EvacuateRegionsTask g1_par_task(this,
                                      per_thread_states,
                                      _task_queues,
                                      &root_processor,
                                      num_workers,
                                      has_optional_evacuation_work);
    task_time = run_task_timed(&g1_par_task);
    // Closing the inner scope will execute the destructor for the G1RootProcessor object.
    // To extract its code root fixup time we measure total time of this scope and
    // subtract from the time the WorkGang task took.
  }
  Tickspan total_processing = Ticks::now() - start_processing;

  p->record_initial_evac_time(task_time.seconds() * 1000.0);
  p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);

  rem_set()->complete_evac_phase(has_optional_evacuation_work);
}

class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {

  void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
    _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy, true /* remember_already_scanned_cards */);
    _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
  }

  void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
    G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
  }

public:
  G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
                                G1ScannerTasksQueueSet* queues,
                                uint num_workers) :
    G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
  }
};

void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
  class G1MarkScope : public MarkScope { };

  Tickspan task_time;

  Ticks start_processing = Ticks::now();
  {
    G1MarkScope code_mark_scope;
    G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
    task_time = run_task_timed(&task);
    // See comment in evacuate_collection_set() for the reason of the scope.
  }
  Tickspan total_processing = Ticks::now() - start_processing;

  G1GCPhaseTimes* p = phase_times();
  p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
}

void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
  const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;

  while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {

    double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
    double time_left_ms = MaxGCPauseMillis - time_used_ms;

    if (time_left_ms < 0 ||
        !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
      log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
                                _collection_set.optional_region_length(), time_left_ms);
      break;
    }

    {
      Ticks start = Ticks::now();
      rem_set()->merge_heap_roots(false /* initial_evacuation */);
      phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
    }

    {
      Ticks start = Ticks::now();
      evacuate_next_optional_regions(per_thread_states);
      phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
    }

    rem_set()->complete_evac_phase(true /* has_more_than_one_evacuation_phase */);
  }

  _collection_set.abandon_optional_collection_set(per_thread_states);
}

void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
                                                   G1RedirtyCardsQueueSet* rdcqs,
                                                   G1ParScanThreadStateSet* per_thread_states) {
  G1GCPhaseTimes* p = phase_times();

  // Process any discovered reference objects - we have
  // to do this _before_ we retire the GC alloc regions
  // as we may have to copy some 'reachable' referent
  // objects (and their reachable sub-graphs) that were
  // not copied during the pause.
  process_discovered_references(per_thread_states);

  G1STWIsAliveClosure is_alive(this);
  G1KeepAliveClosure keep_alive(this);

  WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times());

  _allocator->release_gc_alloc_regions(evacuation_info);

  post_evacuate_cleanup_1(per_thread_states, rdcqs);

  post_evacuate_cleanup_2(&_preserved_marks_set, rdcqs, &evacuation_info, per_thread_states->surviving_young_words());

  assert_used_and_recalculate_used_equal(this);

  rebuild_free_region_list();

  record_obj_copy_mem_stats();

  evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
  evacuation_info.set_bytes_used(_bytes_used_during_gc);

  policy()->print_age_table();
  rem_set()->print_coarsen_stats();
}

void G1CollectedHeap::record_obj_copy_mem_stats() {
  policy()->old_gen_alloc_tracker()->
    add_allocated_bytes_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);

  _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
                                               create_g1_evac_summary(&_old_evac_stats));
}

void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) {
  assert(!hr->is_free(), "the region should not be free");
  assert(!hr->is_empty(), "the region should not be empty");
  assert(_hrm.is_available(hr->hrm_index()), "region should be committed");

  if (G1VerifyBitmaps) {
    MemRegion mr(hr->bottom(), hr->end());
    concurrent_mark()->clear_range_in_prev_bitmap(mr);
  }

  // Clear the card counts for this region.
  // Note: we only need to do this if the region is not young
  // (since we don't refine cards in young regions).
  if (!hr->is_young()) {
    _hot_card_cache->reset_card_counts(hr);
  }

  // Reset region metadata to allow reuse.
  hr->hr_clear(true /* clear_space */);
  _policy->remset_tracker()->update_at_free(hr);

  if (free_list != NULL) {
    free_list->add_ordered(hr);
  }
}

void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
                                            FreeRegionList* free_list) {
  assert(hr->is_humongous(), "this is only for humongous regions");
  hr->clear_humongous();
  free_region(hr, free_list);
}

void G1CollectedHeap::remove_from_old_gen_sets(const uint old_regions_removed,
                                               const uint archive_regions_removed,
                                               const uint humongous_regions_removed) {
  if (old_regions_removed > 0 || archive_regions_removed > 0 || humongous_regions_removed > 0) {
    MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
    _old_set.bulk_remove(old_regions_removed);
    _archive_set.bulk_remove(archive_regions_removed);
    _humongous_set.bulk_remove(humongous_regions_removed);
  }

}

void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
  assert(list != NULL, "list can't be null");
  if (!list->is_empty()) {
    MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
    _hrm.insert_list_into_free_list(list);
  }
}

void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
  decrease_used(bytes);
}

void G1CollectedHeap::post_evacuate_cleanup_1(G1ParScanThreadStateSet* per_thread_states,
                                              G1RedirtyCardsQueueSet* rdcqs) {
  Ticks start = Ticks::now();
  {
    G1PostEvacuateCollectionSetCleanupTask1 cl(per_thread_states, rdcqs);
    run_batch_task(&cl);
  }
  phase_times()->record_post_evacuate_cleanup_task_1_time((Ticks::now() - start).seconds() * 1000.0);
}

void G1CollectedHeap::post_evacuate_cleanup_2(PreservedMarksSet* preserved_marks,
                                              G1RedirtyCardsQueueSet* rdcqs,
                                              G1EvacuationInfo* evacuation_info,
                                              const size_t* surviving_young_words) {
  Ticks start = Ticks::now();
  {
    G1PostEvacuateCollectionSetCleanupTask2 cl(preserved_marks, rdcqs, evacuation_info, surviving_young_words);
    run_batch_task(&cl);
  }
  phase_times()->record_post_evacuate_cleanup_task_2_time((Ticks::now() - start).seconds() * 1000.0);
}

void G1CollectedHeap::clear_eden() {
  _eden.clear();
}

void G1CollectedHeap::clear_collection_set() {
  collection_set()->clear();
}

void G1CollectedHeap::rebuild_free_region_list() {
  Ticks start = Ticks::now();
  _hrm.rebuild_free_list(workers());
  phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - start).seconds() * 1000.0);
}

class G1AbandonCollectionSetClosure : public HeapRegionClosure {
public:
  virtual bool do_heap_region(HeapRegion* r) {
    assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
    G1CollectedHeap::heap()->clear_region_attr(r);
    r->clear_young_index_in_cset();
    return false;
  }
};

void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
  G1AbandonCollectionSetClosure cl;
  collection_set_iterate_all(&cl);

  collection_set->clear();
  collection_set->stop_incremental_building();
}

bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
  return _allocator->is_retained_old_region(hr);
}

void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
  _eden.add(hr);
  _policy->set_region_eden(hr);
}

#ifdef ASSERT

class NoYoungRegionsClosure: public HeapRegionClosure {
private:
  bool _success;
public:
  NoYoungRegionsClosure() : _success(true) { }
  bool do_heap_region(HeapRegion* r) {
    if (r->is_young()) {
      log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
                            p2i(r->bottom()), p2i(r->end()));
      _success = false;
    }
    return false;
  }
  bool success() { return _success; }
};

bool G1CollectedHeap::check_young_list_empty() {
  bool ret = (young_regions_count() == 0);

  NoYoungRegionsClosure closure;
  heap_region_iterate(&closure);
  ret = ret && closure.success();

  return ret;
}

#endif // ASSERT

// Remove the given HeapRegion from the appropriate region set.
void G1CollectedHeap::prepare_region_for_full_compaction(HeapRegion* hr) {
   if (hr->is_archive()) {
    _archive_set.remove(hr);
  } else if (hr->is_humongous()) {
    _humongous_set.remove(hr);
  } else if (hr->is_old()) {
    _old_set.remove(hr);
  } else if (hr->is_young()) {
    // Note that emptying the eden and survivor lists is postponed and instead
    // done as the first step when rebuilding the regions sets again. The reason
    // for this is that during a full GC string deduplication needs to know if
    // a collected region was young or old when the full GC was initiated.
    hr->uninstall_surv_rate_group();
  } else {
    // We ignore free regions, we'll empty the free list afterwards.
    assert(hr->is_free(), "it cannot be another type");
  }
}

void G1CollectedHeap::increase_used(size_t bytes) {
  _summary_bytes_used += bytes;
}

void G1CollectedHeap::decrease_used(size_t bytes) {
  assert(_summary_bytes_used >= bytes,
         "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
         _summary_bytes_used, bytes);
  _summary_bytes_used -= bytes;
}

void G1CollectedHeap::set_used(size_t bytes) {
  _summary_bytes_used = bytes;
}

class RebuildRegionSetsClosure : public HeapRegionClosure {
private:
  bool _free_list_only;

  HeapRegionSet* _old_set;
  HeapRegionSet* _archive_set;
  HeapRegionSet* _humongous_set;

  HeapRegionManager* _hrm;

  size_t _total_used;

public:
  RebuildRegionSetsClosure(bool free_list_only,
                           HeapRegionSet* old_set,
                           HeapRegionSet* archive_set,
                           HeapRegionSet* humongous_set,
                           HeapRegionManager* hrm) :
    _free_list_only(free_list_only), _old_set(old_set), _archive_set(archive_set),
    _humongous_set(humongous_set), _hrm(hrm), _total_used(0) {
    assert(_hrm->num_free_regions() == 0, "pre-condition");
    if (!free_list_only) {
      assert(_old_set->is_empty(), "pre-condition");
      assert(_archive_set->is_empty(), "pre-condition");
      assert(_humongous_set->is_empty(), "pre-condition");
    }
  }

  bool do_heap_region(HeapRegion* r) {
    if (r->is_empty()) {
      assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
      // Add free regions to the free list
      r->set_free();
      _hrm->insert_into_free_list(r);
    } else if (!_free_list_only) {
      assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");

      if (r->is_humongous()) {
        _humongous_set->add(r);
      } else if (r->is_archive()) {
        _archive_set->add(r);
      } else {
        assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
        // We now move all (non-humongous, non-old, non-archive) regions to old gen,
        // and register them as such.
        r->move_to_old();
        _old_set->add(r);
      }
      _total_used += r->used();
    }

    return false;
  }

  size_t total_used() {
    return _total_used;
  }
};

void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
  assert_at_safepoint_on_vm_thread();

  if (!free_list_only) {
    _eden.clear();
    _survivor.clear();
  }

  RebuildRegionSetsClosure cl(free_list_only,
                              &_old_set, &_archive_set, &_humongous_set,
                              &_hrm);
  heap_region_iterate(&cl);

  if (!free_list_only) {
    set_used(cl.total_used());
    if (_archive_allocator != NULL) {
      _archive_allocator->clear_used();
    }
  }
  assert_used_and_recalculate_used_equal(this);
}

// Methods for the mutator alloc region

HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
                                                      bool force,
                                                      uint node_index) {
  assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
  bool should_allocate = policy()->should_allocate_mutator_region();
  if (force || should_allocate) {
    HeapRegion* new_alloc_region = new_region(word_size,
                                              HeapRegionType::Eden,
                                              false /* do_expand */,
                                              node_index);
    if (new_alloc_region != NULL) {
      set_region_short_lived_locked(new_alloc_region);
      _hr_printer.alloc(new_alloc_region, !should_allocate);
      _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
      _policy->remset_tracker()->update_at_allocate(new_alloc_region);
      return new_alloc_region;
    }
  }
  return NULL;
}

void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
                                                  size_t allocated_bytes) {
  assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
  assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");

  collection_set()->add_eden_region(alloc_region);
  increase_used(allocated_bytes);
  _eden.add_used_bytes(allocated_bytes);
  _hr_printer.retire(alloc_region);

  // We update the eden sizes here, when the region is retired,
  // instead of when it's allocated, since this is the point that its
  // used space has been recorded in _summary_bytes_used.
  g1mm()->update_eden_size();
}

// Methods for the GC alloc regions

bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
  if (dest.is_old()) {
    return true;
  } else {
    return survivor_regions_count() < policy()->max_survivor_regions();
  }
}

HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
  assert(FreeList_lock->owned_by_self(), "pre-condition");

  if (!has_more_regions(dest)) {
    return NULL;
  }

  HeapRegionType type;
  if (dest.is_young()) {
    type = HeapRegionType::Survivor;
  } else {
    type = HeapRegionType::Old;
  }

  HeapRegion* new_alloc_region = new_region(word_size,
                                            type,
                                            true /* do_expand */,
                                            node_index);

  if (new_alloc_region != NULL) {
    if (type.is_survivor()) {
      new_alloc_region->set_survivor();
      _survivor.add(new_alloc_region);
      _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
    } else {
      new_alloc_region->set_old();
      _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
    }
    _policy->remset_tracker()->update_at_allocate(new_alloc_region);
    register_region_with_region_attr(new_alloc_region);
    _hr_printer.alloc(new_alloc_region);
    return new_alloc_region;
  }
  return NULL;
}

void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
                                             size_t allocated_bytes,
                                             G1HeapRegionAttr dest) {
  _bytes_used_during_gc += allocated_bytes;
  if (dest.is_old()) {
    old_set_add(alloc_region);
  } else {
    assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
    _survivor.add_used_bytes(allocated_bytes);
  }

  bool const during_im = collector_state()->in_concurrent_start_gc();
  if (during_im && allocated_bytes > 0) {
    _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
  }
  _hr_printer.retire(alloc_region);
}

HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
  bool expanded = false;
  uint index = _hrm.find_highest_free(&expanded);

  if (index != G1_NO_HRM_INDEX) {
    if (expanded) {
      log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
                                HeapRegion::GrainWords * HeapWordSize);
    }
    return _hrm.allocate_free_regions_starting_at(index, 1);
  }
  return NULL;
}

// Optimized nmethod scanning

class RegisterNMethodOopClosure: public OopClosure {
  G1CollectedHeap* _g1h;
  nmethod* _nm;

  template <class T> void do_oop_work(T* p) {
    T heap_oop = RawAccess<>::oop_load(p);
    if (!CompressedOops::is_null(heap_oop)) {
      oop obj = CompressedOops::decode_not_null(heap_oop);
      HeapRegion* hr = _g1h->heap_region_containing(obj);
      assert(!hr->is_continues_humongous(),
             "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
             " starting at " HR_FORMAT,
             p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));

      // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
      hr->add_strong_code_root_locked(_nm);
    }
  }

public:
  RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
    _g1h(g1h), _nm(nm) {}

  void do_oop(oop* p)       { do_oop_work(p); }
  void do_oop(narrowOop* p) { do_oop_work(p); }
};

class UnregisterNMethodOopClosure: public OopClosure {
  G1CollectedHeap* _g1h;
  nmethod* _nm;

  template <class T> void do_oop_work(T* p) {
    T heap_oop = RawAccess<>::oop_load(p);
    if (!CompressedOops::is_null(heap_oop)) {
      oop obj = CompressedOops::decode_not_null(heap_oop);
      HeapRegion* hr = _g1h->heap_region_containing(obj);
      assert(!hr->is_continues_humongous(),
             "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
             " starting at " HR_FORMAT,
             p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));

      hr->remove_strong_code_root(_nm);
    }
  }

public:
  UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
    _g1h(g1h), _nm(nm) {}

  void do_oop(oop* p)       { do_oop_work(p); }
  void do_oop(narrowOop* p) { do_oop_work(p); }
};

void G1CollectedHeap::register_nmethod(nmethod* nm) {
  guarantee(nm != NULL, "sanity");
  RegisterNMethodOopClosure reg_cl(this, nm);
  nm->oops_do(&reg_cl);
}

void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
  guarantee(nm != NULL, "sanity");
  UnregisterNMethodOopClosure reg_cl(this, nm);
  nm->oops_do(&reg_cl, true);
}

void G1CollectedHeap::update_used_after_gc() {
  if (evacuation_failed()) {
    // Reset the G1EvacuationFailureALot counters and flags
    NOT_PRODUCT(reset_evacuation_should_fail();)

    set_used(recalculate_used());

    if (_archive_allocator != NULL) {
      _archive_allocator->clear_used();
    }
    for (uint i = 0; i < ParallelGCThreads; i++) {
      if (_evacuation_failed_info_array[i].has_failed()) {
        _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
      }
    }
  } else {
    // The "used" of the the collection set have already been subtracted
    // when they were freed.  Add in the bytes used.
    increase_used(_bytes_used_during_gc);
  }
}

void G1CollectedHeap::reset_hot_card_cache() {
  _hot_card_cache->reset_hot_cache();
  _hot_card_cache->set_use_cache(true);
}

void G1CollectedHeap::purge_code_root_memory() {
  G1CodeRootSet::purge();
}

class RebuildStrongCodeRootClosure: public CodeBlobClosure {
  G1CollectedHeap* _g1h;

public:
  RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
    _g1h(g1h) {}

  void do_code_blob(CodeBlob* cb) {
    nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
    if (nm == NULL) {
      return;
    }

    _g1h->register_nmethod(nm);
  }
};

void G1CollectedHeap::rebuild_strong_code_roots() {
  RebuildStrongCodeRootClosure blob_cl(this);
  CodeCache::blobs_do(&blob_cl);
}

void G1CollectedHeap::initialize_serviceability() {
  _g1mm->initialize_serviceability();
}

MemoryUsage G1CollectedHeap::memory_usage() {
  return _g1mm->memory_usage();
}

GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
  return _g1mm->memory_managers();
}

GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
  return _g1mm->memory_pools();
}