/*
 * Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * 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.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "gc/g1/g1Allocator.inline.hpp"
#include "gc/g1/g1AllocRegion.inline.hpp"
#include "gc/g1/g1EvacStats.inline.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1CollectorPolicy.hpp"
#include "gc/g1/g1MarkSweep.hpp"
#include "gc/g1/vm_operations_g1.hpp"
#include "gc/g1/heapRegion.inline.hpp"
#include "gc/g1/heapRegionSet.inline.hpp"
#include "gc/shared/gcLocker.hpp"
#include "runtime/vmThread.hpp"

G1DefaultAllocator::G1DefaultAllocator(G1CollectedHeap* heap) :
  G1Allocator(heap),
  _survivor_is_full(false),
  _old_is_full(false),
  _retained_old_gc_alloc_region(NULL),
  _survivor_gc_alloc_region(heap->alloc_buffer_stats(InCSetState::Young)),
  _old_gc_alloc_region(heap->alloc_buffer_stats(InCSetState::Old)) {
}

void G1DefaultAllocator::init_mutator_alloc_region() {
  assert(_mutator_alloc_region.get() == NULL, "pre-condition");
  _mutator_alloc_region.init();
}

void G1DefaultAllocator::release_mutator_alloc_region() {
  _mutator_alloc_region.release();
  assert(_mutator_alloc_region.get() == NULL, "post-condition");
}

void G1Allocator::reuse_retained_old_region(EvacuationInfo& evacuation_info,
                                            OldGCAllocRegion* old,
                                            HeapRegion** retained_old) {
  HeapRegion* retained_region = *retained_old;
  *retained_old = NULL;
  assert(retained_region == NULL || !retained_region->is_archive(),
         "Archive region should not be alloc region (index %u)", retained_region->hrm_index());

  // We will discard the current GC alloc region if:
  // a) it's in the collection set (it can happen!),
  // b) it's already full (no point in using it),
  // c) it's empty (this means that it was emptied during
  // a cleanup and it should be on the free list now), or
  // d) it's humongous (this means that it was emptied
  // during a cleanup and was added to the free list, but
  // has been subsequently used to allocate a humongous
  // object that may be less than the region size).
  if (retained_region != NULL &&
      !retained_region->in_collection_set() &&
      !(retained_region->top() == retained_region->end()) &&
      !retained_region->is_empty() &&
      !retained_region->is_humongous()) {
    retained_region->record_timestamp();
    // The retained region was added to the old region set when it was
    // retired. We have to remove it now, since we don't allow regions
    // we allocate to in the region sets. We'll re-add it later, when
    // it's retired again.
    _g1h->old_set_remove(retained_region);
    bool during_im = _g1h->collector_state()->during_initial_mark_pause();
    retained_region->note_start_of_copying(during_im);
    old->set(retained_region);
    _g1h->hr_printer()->reuse(retained_region);
    evacuation_info.set_alloc_regions_used_before(retained_region->used());
  }
}

void G1DefaultAllocator::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
  assert_at_safepoint(true /* should_be_vm_thread */);

  _survivor_is_full = false;
  _old_is_full = false;

  _survivor_gc_alloc_region.init();
  _old_gc_alloc_region.init();
  reuse_retained_old_region(evacuation_info,
                            &_old_gc_alloc_region,
                            &_retained_old_gc_alloc_region);
}

void G1DefaultAllocator::release_gc_alloc_regions(EvacuationInfo& evacuation_info) {
  AllocationContext_t context = AllocationContext::current();
  evacuation_info.set_allocation_regions(survivor_gc_alloc_region(context)->count() +
                                         old_gc_alloc_region(context)->count());
  survivor_gc_alloc_region(context)->release();
  // If we have an old GC alloc region to release, we'll save it in
  // _retained_old_gc_alloc_region. If we don't
  // _retained_old_gc_alloc_region will become NULL. This is what we
  // want either way so no reason to check explicitly for either
  // condition.
  _retained_old_gc_alloc_region = old_gc_alloc_region(context)->release();
  if (_retained_old_gc_alloc_region != NULL) {
    _retained_old_gc_alloc_region->record_retained_region();
  }
}

void G1DefaultAllocator::abandon_gc_alloc_regions() {
  assert(survivor_gc_alloc_region(AllocationContext::current())->get() == NULL, "pre-condition");
  assert(old_gc_alloc_region(AllocationContext::current())->get() == NULL, "pre-condition");
  _retained_old_gc_alloc_region = NULL;
}

bool G1DefaultAllocator::survivor_is_full(AllocationContext_t context) const {
  return _survivor_is_full;
}

bool G1DefaultAllocator::old_is_full(AllocationContext_t context) const {
  return _old_is_full;
}

void G1DefaultAllocator::set_survivor_full(AllocationContext_t context) {
  _survivor_is_full = true;
}

void G1DefaultAllocator::set_old_full(AllocationContext_t context) {
  _old_is_full = true;
}

G1PLAB::G1PLAB(size_t gclab_word_size) :
  PLAB(gclab_word_size), _retired(true) { }

size_t G1Allocator::unsafe_max_tlab_alloc(AllocationContext_t context) {
  // Return the remaining space in the cur alloc region, but not less than
  // the min TLAB size.

  // Also, this value can be at most the humongous object threshold,
  // since we can't allow tlabs to grow big enough to accommodate
  // humongous objects.

  HeapRegion* hr = mutator_alloc_region(context)->get();
  size_t max_tlab = _g1h->max_tlab_size() * wordSize;
  if (hr == NULL) {
    return max_tlab;
  } else {
    return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
  }
}

inline bool G1Allocator::is_humongous(size_t word_size) {
  return G1CollectedHeap::is_humongous(word_size);
}

HeapWord* G1Allocator::attempt_allocation_slow(size_t word_size,
                                               AllocationContext_t context,
                                               uint* gc_count_before_ret,
                                               uint* gclocker_retry_count_ret) {
  // 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 (int try_count = 1; /* we'll return */; try_count += 1) {
    bool should_try_gc;
    uint gc_count_before;

    {
      MutexLockerEx x(Heap_lock);
      result = attempt_allocation_locked(word_size, context);
      if (result != NULL) {
        return result;
      }

      if (GCLocker::is_active_and_needs_gc()) {
        if (_g1h->g1_policy()->can_expand_young_list()) {
          // No need for an ergo verbose message here,
          // can_expand_young_list() does this when it returns true.
          result = attempt_allocation_force(word_size, context);
          if (result != NULL) {
            return result;
          }
        }
        should_try_gc = false;
      } else {
        // The GCLocker may not be active but the GCLocker initiated
        // GC may not yet have been performed (GCLocker::needs_gc()
        // returns true). In this case we do not try this GC and
        // wait until the GCLocker initiated GC is performed, and
        // then retry the allocation.
        if (GCLocker::needs_gc()) {
          should_try_gc = false;
        } else {
          // Read the GC count while still holding the Heap_lock.
          gc_count_before = _g1h->total_collections();
          should_try_gc = true;
        }
      }
    }

    if (should_try_gc) {
      bool succeeded;
      result = _g1h->do_collection_pause(word_size, gc_count_before, &succeeded,
                                         GCCause::_g1_inc_collection_pause);
      if (result != NULL) {
        assert(succeeded, "only way to get back a non-NULL result");
        return result;
      }

      if (succeeded) {
        // If we get here we successfully scheduled a collection which
        // failed to allocate. No point in trying to allocate
        // further. We'll just return NULL.
        MutexLockerEx x(Heap_lock);
        *gc_count_before_ret = _g1h->total_collections();
        return NULL;
      }
    } else {
      if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
        MutexLockerEx x(Heap_lock);
        *gc_count_before_ret = _g1h->total_collections();
        return NULL;
      }
      // 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_ret) += 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).
    result = attempt_allocation(word_size, context);
    if (result != NULL) {
      return result;
    }

    // Give a warning if we seem to be looping forever.
    if ((QueuedAllocationWarningCount > 0) &&
        (try_count % QueuedAllocationWarningCount == 0)) {
      warning("G1CollectedHeap::attempt_allocation_slow() "
              "retries %d times", try_count);
    }
  }

  ShouldNotReachHere();
  return NULL;
}

HeapWord* G1Allocator::humongous_obj_allocate_initialize_regions(uint first,
                                                                 uint num_regions,
                                                                 size_t word_size,
                                                                 AllocationContext_t context) {
  assert(first != G1_NO_HRM_INDEX, "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 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");

  // This will be the "starts humongous" region.
  HeapRegion* first_hr = _g1h->region_at(first);
  // The header of the new object will be placed at the bottom of
  // the first 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);

  // 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 >= _g1h->min_fill_size()) {
    _g1h->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);
  first_hr->set_allocation_context(context);
  // 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 = _g1h->region_at(i);
    hr->set_continues_humongous(first_hr);
    hr->set_allocation_context(context);
  }

  // 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 = _g1h->region_at(i);
    hr->set_top(hr->end());
  }

  hr = _g1h->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");

  _g1h->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");

  _g1h->increase_used((word_size_sum - words_not_fillable) * HeapWordSize);

  for (uint i = first; i <= last; ++i) {
    hr = _g1h->region_at(i);
    _g1h->_humongous_set.add(hr);
    _g1h->hr_printer()->alloc(hr);
  }

  return new_obj;
}

size_t G1Allocator::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_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
}

HeapWord* G1Allocator::attempt_allocation_at_safepoint(size_t word_size,
                                                       AllocationContext_t context,
                                                       bool expect_null_mutator_alloc_region) {
  assert_at_safepoint(true /* should_be_vm_thread */);
  assert(!has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
         "the current alloc region was unexpectedly found to be non-NULL");

  if (!is_humongous(word_size)) {
    return attempt_allocation_locked(word_size, context);
  } else {
    HeapWord* result = humongous_obj_allocate(word_size, context);
    if (result != NULL && _g1h->g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
      _g1h->collector_state()->set_initiate_conc_mark_if_possible(true);
    }
    return result;
  }

  ShouldNotReachHere();
}

// 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* G1Allocator::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
  assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);

  _g1h->verifier()->verify_region_sets_optional();

  uint first = G1_NO_HRM_INDEX;
  uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);

  if (obj_regions == 1) {
    // Only one region to allocate, try to use a fast path by directly allocating
    // from the free lists. Do not try to expand here, we will potentially do that
    // later.
    HeapRegion* hr = _g1h->new_region(word_size, true /* is_old */, false /* do_expand */);
    if (hr != NULL) {
      first = hr->hrm_index();
    }
  } else {
    // We can't allocate humongous regions spanning more than one region while
    // cleanupComplete() is running, since some of the regions we find to be
    // empty might not yet be added to the free list. It is not straightforward
    // to know in which list they are on so that we can remove them. We only
    // need to do this if we need to allocate more than one region to satisfy the
    // current humongous allocation request. If we are only allocating one region
    // we use the one-region region allocation code (see above), that already
    // potentially waits for regions from the secondary free list.
    _g1h->wait_while_free_regions_coming();
    _g1h->append_secondary_free_list_if_not_empty_with_lock();

    // Policy: Try only empty regions (i.e. already committed first). Maybe we
    // are lucky enough to find some.
    first = _g1h->_hrm.find_contiguous_only_empty(obj_regions);
    if (first != G1_NO_HRM_INDEX) {
      _g1h->_hrm.allocate_free_regions_starting_at(first, obj_regions);
    }
  }

  if (first == G1_NO_HRM_INDEX) {
    // 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, try expansion.
    first = _g1h->_hrm.find_contiguous_empty_or_unavailable(obj_regions);
    if (first != G1_NO_HRM_INDEX) {
      // We found something. Make sure these regions are committed, i.e. expand
      // the heap. Alternatively we could do a defragmentation GC.
      log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
                                    word_size * HeapWordSize);


      _g1h->_hrm.expand_at(first, obj_regions);
      _g1h->g1_policy()->record_new_heap_size(_g1h->num_regions());

#ifdef ASSERT
      for (uint i = first; i < first + obj_regions; ++i) {
        HeapRegion* hr = _g1h->region_at(i);
        assert(hr->is_free(), "sanity");
        assert(hr->is_empty(), "sanity");
        assert(_g1h->is_on_master_free_list(hr), "sanity");
      }
#endif
      _g1h->_hrm.allocate_free_regions_starting_at(first, obj_regions);
    } else {
      // Policy: Potentially trigger a defragmentation GC.
    }
  }

  HeapWord* result = NULL;
  if (first != G1_NO_HRM_INDEX) {
    result = humongous_obj_allocate_initialize_regions(first, obj_regions,
                                                       word_size, context);
    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.
    _g1h->g1mm()->update_sizes();
  }

  _g1h->verifier()->verify_region_sets_optional();

  return result;
}


HeapWord* G1Allocator::attempt_allocation_humongous(size_t word_size,
                                                    uint* gc_count_before_ret,
                                                    uint* gclocker_retry_count_ret) {
  // 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 (_g1h->g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
                                           word_size)) {
    _g1h->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 (int try_count = 1; /* we'll return */; try_count += 1) {
    bool should_try_gc;
    uint gc_count_before;

    {
      MutexLockerEx x(Heap_lock);

      // 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, AllocationContext::current());
      if (result != NULL) {
        size_t size_in_regions = humongous_obj_size_in_regions(word_size);
        _g1h->g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
        return result;
      }

      if (GCLocker::is_active_and_needs_gc()) {
        should_try_gc = false;
      } else {
         // The GCLocker may not be active but the GCLocker initiated
        // GC may not yet have been performed (GCLocker::needs_gc()
        // returns true). In this case we do not try this GC and
        // wait until the GCLocker initiated GC is performed, and
        // then retry the allocation.
        if (GCLocker::needs_gc()) {
          should_try_gc = false;
        } else {
          // Read the GC count while still holding the Heap_lock.
          gc_count_before = _g1h->total_collections();
          should_try_gc = true;
        }
      }
    }

    if (should_try_gc) {
      // If we failed to allocate the humongous object, we should try to
      // do a collection pause (if we're allowed) in case it reclaims
      // enough space for the allocation to succeed after the pause.

      bool succeeded;
      result = _g1h->do_collection_pause(word_size, gc_count_before, &succeeded,
                                   GCCause::_g1_humongous_allocation);
      if (result != NULL) {
        assert(succeeded, "only way to get back a non-NULL result");
        return result;
      }

      if (succeeded) {
        // If we get here we successfully scheduled a collection which
        // failed to allocate. No point in trying to allocate
        // further. We'll just return NULL.
        MutexLockerEx x(Heap_lock);
        *gc_count_before_ret = _g1h->total_collections();
        return NULL;
      }
    } else {
      if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
        MutexLockerEx x(Heap_lock);
        *gc_count_before_ret = _g1h->total_collections();
        return NULL;
      }
      // 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_ret) += 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.  Give a
    // warning if we seem to be looping forever.

    if ((QueuedAllocationWarningCount > 0) &&
        (try_count % QueuedAllocationWarningCount == 0)) {
      warning("G1CollectedHeap::attempt_allocation_humongous() "
              "retries %d times", try_count);
    }
  }

  ShouldNotReachHere();
  return NULL;
}


HeapWord* G1Allocator::mem_allocate(size_t word_size,
                                    bool*  gc_overhead_limit_was_exceeded) {
  assert_heap_not_locked_and_not_at_safepoint();

  // Loop until the allocation is satisfied, or unsatisfied after GC.
  for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
    uint gc_count_before;

    HeapWord* result = NULL;
    if (!is_humongous(word_size)) {
      result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
    } else {
      result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
    }
    if (result != NULL) {
      return result;
    }

    // Create the garbage collection operation...
    VM_G1CollectForAllocation op(gc_count_before, word_size);
    op.set_allocation_context(AllocationContext::current());

    // ...and get the VM thread to execute it.
    VMThread::execute(&op);

    if (op.prologue_succeeded() && op.pause_succeeded()) {
      // If the operation was successful we'll return the result even
      // if it is NULL. If the allocation attempt failed immediately
      // after a Full GC, it's unlikely we'll be able to allocate now.
      HeapWord* result = op.result();
      if (result != NULL && !is_humongous(word_size)) {
        // Allocations that take place on VM operations do not do any
        // card dirtying and we have to do it here. We only have to do
        // this for non-humongous allocations, though.
        _g1h->dirty_young_block(result, word_size);
      }
      return result;
    } else {
      if (gclocker_retry_count > GCLockerRetryAllocationCount) {
        return NULL;
      }
      assert(op.result() == NULL,
             "the result should be NULL if the VM op did not succeed");
    }

    // Give a warning if we seem to be looping forever.
    if ((QueuedAllocationWarningCount > 0) &&
        (try_count % QueuedAllocationWarningCount == 0)) {
      warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
    }
  }

  ShouldNotReachHere();
  return NULL;
}

#ifndef PRODUCT
void G1Allocator::allocate_dummy_regions(size_t word_size) {
  // And as a result the region we'll allocate will be humongous.
  guarantee(is_humongous(word_size), "sanity");

  for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
    // Let's use the existing mechanism for the allocation
    HeapWord* dummy_obj = humongous_obj_allocate(word_size,
                                                 AllocationContext::system());
    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

inline HeapWord* G1Allocator::attempt_allocation(size_t word_size,
                                                 uint* gc_count_before_ret,
                                                 uint* gclocker_retry_count_ret) {
  assert_heap_not_locked_and_not_at_safepoint();
  assert(!is_humongous(word_size), "attempt_allocation() should not "
         "be called for humongous allocation requests");

  AllocationContext_t context = AllocationContext::current();
  HeapWord* result = attempt_allocation(word_size, context);

  if (result == NULL) {
    result = attempt_allocation_slow(word_size,
                                     context,
                                     gc_count_before_ret,
                                     gclocker_retry_count_ret);
  }
  assert_heap_not_locked();
  if (result != NULL) {
    _g1h->dirty_young_block(result, word_size);
  }
  return result;
}

HeapWord* G1Allocator::allocate_new_tlab(size_t word_size) {
  assert_heap_not_locked_and_not_at_safepoint();
  assert(!is_humongous(word_size), "we do not allow humongous TLABs");

  uint dummy_gc_count_before;
  uint dummy_gclocker_retry_count = 0;
  return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
}

HeapWord* G1Allocator::par_allocate_during_gc(InCSetState dest,
                                              size_t word_size,
                                              AllocationContext_t context) {
  size_t temp = 0;
  HeapWord* result = par_allocate_during_gc(dest, word_size, word_size, &temp, context);
  assert(result == NULL || temp == word_size,
         "Requested " SIZE_FORMAT " words, but got " SIZE_FORMAT " at " PTR_FORMAT,
         word_size, temp, p2i(result));
  return result;
}

HeapWord* G1Allocator::par_allocate_during_gc(InCSetState dest,
                                              size_t min_word_size,
                                              size_t desired_word_size,
                                              size_t* actual_word_size,
                                              AllocationContext_t context) {
  switch (dest.value()) {
    case InCSetState::Young:
      return survivor_attempt_allocation(min_word_size, desired_word_size, actual_word_size, context);
    case InCSetState::Old:
      return old_attempt_allocation(min_word_size, desired_word_size, actual_word_size, context);
    default:
      ShouldNotReachHere();
      return NULL; // Keep some compilers happy
  }
}

HeapWord* G1Allocator::survivor_attempt_allocation(size_t min_word_size,
                                                   size_t desired_word_size,
                                                   size_t* actual_word_size,
                                                   AllocationContext_t context) {
  assert(!is_humongous(desired_word_size),
         "we should not be seeing humongous-size allocations in this path");

  HeapWord* result = survivor_gc_alloc_region(context)->attempt_allocation(min_word_size,
                                                                           desired_word_size,
                                                                           actual_word_size,
                                                                           false /* bot_updates */);
  if (result == NULL && !survivor_is_full(context)) {
    MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
    result = survivor_gc_alloc_region(context)->attempt_allocation_locked(min_word_size,
                                                                          desired_word_size,
                                                                          actual_word_size,
                                                                          false /* bot_updates */);
    if (result == NULL) {
      set_survivor_full(context);
    }
  }
  if (result != NULL) {
    _g1h->dirty_young_block(result, *actual_word_size);
  }
  return result;
}

HeapWord* G1Allocator::old_attempt_allocation(size_t min_word_size,
                                              size_t desired_word_size,
                                              size_t* actual_word_size,
                                              AllocationContext_t context) {
  assert(!is_humongous(desired_word_size),
         "we should not be seeing humongous-size allocations in this path");

  HeapWord* result = old_gc_alloc_region(context)->attempt_allocation(min_word_size,
                                                                      desired_word_size,
                                                                      actual_word_size,
                                                                      true /* bot_updates */);
  if (result == NULL && !old_is_full(context)) {
    MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
    result = old_gc_alloc_region(context)->attempt_allocation_locked(min_word_size,
                                                                     desired_word_size,
                                                                     actual_word_size,
                                                                     true /* bot_updates */);
    if (result == NULL) {
      set_old_full(context);
    }
  }
  return result;
}

G1PLABAllocator::G1PLABAllocator(G1Allocator* allocator) :
  _g1h(G1CollectedHeap::heap()),
  _allocator(allocator),
  _survivor_alignment_bytes(calc_survivor_alignment_bytes()) {
  for (size_t i = 0; i < ARRAY_SIZE(_direct_allocated); i++) {
    _direct_allocated[i] = 0;
  }
}

bool G1PLABAllocator::may_throw_away_buffer(size_t const allocation_word_sz, size_t const buffer_size) const {
  return (allocation_word_sz * 100 < buffer_size * ParallelGCBufferWastePct);
}

HeapWord* G1PLABAllocator::allocate_direct_or_new_plab(InCSetState dest,
                                                       size_t word_sz,
                                                       AllocationContext_t context,
                                                       bool* plab_refill_failed) {
  size_t plab_word_size = G1CollectedHeap::heap()->desired_plab_sz(dest);
  size_t required_in_plab = PLAB::size_required_for_allocation(word_sz);

  // Only get a new PLAB if the allocation fits and it would not waste more than
  // ParallelGCBufferWastePct in the existing buffer.
  if ((required_in_plab <= plab_word_size) &&
    may_throw_away_buffer(required_in_plab, plab_word_size)) {

    G1PLAB* alloc_buf = alloc_buffer(dest, context);
    alloc_buf->retire();

    size_t actual_plab_size = 0;
    HeapWord* buf = _allocator->par_allocate_during_gc(dest,
                                                       required_in_plab,
                                                       plab_word_size,
                                                       &actual_plab_size,
                                                       context);

    assert(buf == NULL || ((actual_plab_size >= required_in_plab) && (actual_plab_size <= plab_word_size)),
           "Requested at minimum " SIZE_FORMAT ", desired " SIZE_FORMAT " words, but got " SIZE_FORMAT " at " PTR_FORMAT,
           required_in_plab, plab_word_size, actual_plab_size, p2i(buf));

    if (buf != NULL) {
      alloc_buf->set_buf(buf, actual_plab_size);

      HeapWord* const obj = alloc_buf->allocate(word_sz);
      assert(obj != NULL, "PLAB should have been big enough, tried to allocate "
                          SIZE_FORMAT " requiring " SIZE_FORMAT " PLAB size " SIZE_FORMAT,
                          word_sz, required_in_plab, plab_word_size);
      return obj;
    }
    // Otherwise.
    *plab_refill_failed = true;
  }
  // Try direct allocation.
  HeapWord* result = _allocator->par_allocate_during_gc(dest, word_sz, context);
  if (result != NULL) {
    _direct_allocated[dest.value()] += word_sz;
  }
  return result;
}

void G1PLABAllocator::undo_allocation(InCSetState dest, HeapWord* obj, size_t word_sz, AllocationContext_t context) {
  alloc_buffer(dest, context)->undo_allocation(obj, word_sz);
}

G1DefaultPLABAllocator::G1DefaultPLABAllocator(G1Allocator* allocator) :
  G1PLABAllocator(allocator),
  _surviving_alloc_buffer(_g1h->desired_plab_sz(InCSetState::Young)),
  _tenured_alloc_buffer(_g1h->desired_plab_sz(InCSetState::Old)) {
  for (uint state = 0; state < InCSetState::Num; state++) {
    _alloc_buffers[state] = NULL;
  }
  _alloc_buffers[InCSetState::Young] = &_surviving_alloc_buffer;
  _alloc_buffers[InCSetState::Old]  = &_tenured_alloc_buffer;
}

void G1DefaultPLABAllocator::flush_and_retire_stats() {
  for (uint state = 0; state < InCSetState::Num; state++) {
    G1PLAB* const buf = _alloc_buffers[state];
    if (buf != NULL) {
      G1EvacStats* stats = _g1h->alloc_buffer_stats(state);
      buf->flush_and_retire_stats(stats);
      stats->add_direct_allocated(_direct_allocated[state]);
      _direct_allocated[state] = 0;
    }
  }
}

void G1DefaultPLABAllocator::waste(size_t& wasted, size_t& undo_wasted) {
  wasted = 0;
  undo_wasted = 0;
  for (uint state = 0; state < InCSetState::Num; state++) {
    G1PLAB * const buf = _alloc_buffers[state];
    if (buf != NULL) {
      wasted += buf->waste();
      undo_wasted += buf->undo_waste();
    }
  }
}

G1ArchiveAllocator* G1ArchiveAllocator::create_allocator(G1CollectedHeap* g1h) {
  // Create the archive allocator, and also enable archive object checking
  // in mark-sweep, since we will be creating archive regions.
  G1ArchiveAllocator* result =  new G1ArchiveAllocator(g1h);
  G1MarkSweep::enable_archive_object_check();
  return result;
}

bool G1ArchiveAllocator::alloc_new_region() {
  // Allocate the highest free region in the reserved heap,
  // and add it to our list of allocated regions. It is marked
  // archive and added to the old set.
  HeapRegion* hr = _g1h->alloc_highest_free_region();
  if (hr == NULL) {
    return false;
  }
  assert(hr->is_empty(), "expected empty region (index %u)", hr->hrm_index());
  hr->set_archive();
  _g1h->old_set_add(hr);
  _g1h->hr_printer()->alloc(hr);
  _allocated_regions.append(hr);
  _allocation_region = hr;

  // Set up _bottom and _max to begin allocating in the lowest
  // min_region_size'd chunk of the allocated G1 region.
  _bottom = hr->bottom();
  _max = _bottom + HeapRegion::min_region_size_in_words();

  // Tell mark-sweep that objects in this region are not to be marked.
  G1MarkSweep::set_range_archive(MemRegion(_bottom, HeapRegion::GrainWords), true);

  // Since we've modified the old set, call update_sizes.
  _g1h->g1mm()->update_sizes();
  return true;
}

HeapWord* G1ArchiveAllocator::archive_mem_allocate(size_t word_size) {
  assert(word_size != 0, "size must not be zero");
  if (_allocation_region == NULL) {
    if (!alloc_new_region()) {
      return NULL;
    }
  }
  HeapWord* old_top = _allocation_region->top();
  assert(_bottom >= _allocation_region->bottom(),
         "inconsistent allocation state: " PTR_FORMAT " < " PTR_FORMAT,
         p2i(_bottom), p2i(_allocation_region->bottom()));
  assert(_max <= _allocation_region->end(),
         "inconsistent allocation state: " PTR_FORMAT " > " PTR_FORMAT,
         p2i(_max), p2i(_allocation_region->end()));
  assert(_bottom <= old_top && old_top <= _max,
         "inconsistent allocation state: expected "
         PTR_FORMAT " <= " PTR_FORMAT " <= " PTR_FORMAT,
         p2i(_bottom), p2i(old_top), p2i(_max));

  // Allocate the next word_size words in the current allocation chunk.
  // If allocation would cross the _max boundary, insert a filler and begin
  // at the base of the next min_region_size'd chunk. Also advance to the next
  // chunk if we don't yet cross the boundary, but the remainder would be too
  // small to fill.
  HeapWord* new_top = old_top + word_size;
  size_t remainder = pointer_delta(_max, new_top);
  if ((new_top > _max) ||
      ((new_top < _max) && (remainder < CollectedHeap::min_fill_size()))) {
    if (old_top != _max) {
      size_t fill_size = pointer_delta(_max, old_top);
      CollectedHeap::fill_with_object(old_top, fill_size);
      _summary_bytes_used += fill_size * HeapWordSize;
    }
    _allocation_region->set_top(_max);
    old_top = _bottom = _max;

    // Check if we've just used up the last min_region_size'd chunk
    // in the current region, and if so, allocate a new one.
    if (_bottom != _allocation_region->end()) {
      _max = _bottom + HeapRegion::min_region_size_in_words();
    } else {
      if (!alloc_new_region()) {
        return NULL;
      }
      old_top = _allocation_region->bottom();
    }
  }
  _allocation_region->set_top(old_top + word_size);
  _summary_bytes_used += word_size * HeapWordSize;

  return old_top;
}

void G1ArchiveAllocator::complete_archive(GrowableArray<MemRegion>* ranges,
                                          size_t end_alignment_in_bytes) {
  assert((end_alignment_in_bytes >> LogHeapWordSize) < HeapRegion::min_region_size_in_words(),
         "alignment " SIZE_FORMAT " too large", end_alignment_in_bytes);
  assert(is_size_aligned(end_alignment_in_bytes, HeapWordSize),
         "alignment " SIZE_FORMAT " is not HeapWord (%u) aligned", end_alignment_in_bytes, HeapWordSize);

  // If we've allocated nothing, simply return.
  if (_allocation_region == NULL) {
    return;
  }

  // If an end alignment was requested, insert filler objects.
  if (end_alignment_in_bytes != 0) {
    HeapWord* currtop = _allocation_region->top();
    HeapWord* newtop = (HeapWord*)align_pointer_up(currtop, end_alignment_in_bytes);
    size_t fill_size = pointer_delta(newtop, currtop);
    if (fill_size != 0) {
      if (fill_size < CollectedHeap::min_fill_size()) {
        // If the required fill is smaller than we can represent,
        // bump up to the next aligned address. We know we won't exceed the current
        // region boundary because the max supported alignment is smaller than the min
        // region size, and because the allocation code never leaves space smaller than
        // the min_fill_size at the top of the current allocation region.
        newtop = (HeapWord*)align_pointer_up(currtop + CollectedHeap::min_fill_size(),
                                             end_alignment_in_bytes);
        fill_size = pointer_delta(newtop, currtop);
      }
      HeapWord* fill = archive_mem_allocate(fill_size);
      CollectedHeap::fill_with_objects(fill, fill_size);
    }
  }

  // Loop through the allocated regions, and create MemRegions summarizing
  // the allocated address range, combining contiguous ranges. Add the
  // MemRegions to the GrowableArray provided by the caller.
  int index = _allocated_regions.length() - 1;
  assert(_allocated_regions.at(index) == _allocation_region,
         "expected region %u at end of array, found %u",
         _allocation_region->hrm_index(), _allocated_regions.at(index)->hrm_index());
  HeapWord* base_address = _allocation_region->bottom();
  HeapWord* top = base_address;

  while (index >= 0) {
    HeapRegion* next = _allocated_regions.at(index);
    HeapWord* new_base = next->bottom();
    HeapWord* new_top = next->top();
    if (new_base != top) {
      ranges->append(MemRegion(base_address, pointer_delta(top, base_address)));
      base_address = new_base;
    }
    top = new_top;
    index = index - 1;
  }

  assert(top != base_address, "zero-sized range, address " PTR_FORMAT, p2i(base_address));
  ranges->append(MemRegion(base_address, pointer_delta(top, base_address)));
  _allocated_regions.clear();
  _allocation_region = NULL;
};