view src/share/vm/gc/g1/g1Allocator.hpp @ 8865:a8c6a4d765bb

8003237: G1: Reduce unnecessary (and failing) allocation attempts when handling an evacuation failure Summary: Remember for every generation whether the memory for that generation has already been exhausted. If so, do not try to get a new region for these generations. Further, if the last generation is full, early exit from copy_to_survivor_space. Reviewed-by: jmasa, brutisso
author tschatzl
date Wed, 19 Aug 2015 13:47:40 +0200
parents 9a8a76230f5d
children a3fbc02ec341
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 * Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
 * 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 if you need additional information or have any
 * questions.


#include "gc/g1/g1AllocRegion.hpp"
#include "gc/g1/g1AllocationContext.hpp"
#include "gc/g1/g1InCSetState.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/plab.hpp"

class EvacuationInfo;

// Interface to keep track of which regions G1 is currently allocating into. Provides
// some accessors (e.g. allocating into them, or getting their occupancy).
// Also keeps track of retained regions across GCs.
class G1Allocator : public CHeapObj<mtGC> {
  friend class VMStructs;
  bool _survivor_is_full;
  bool _old_is_full;
  G1CollectedHeap* _g1h;

  virtual MutatorAllocRegion* mutator_alloc_region(AllocationContext_t context) = 0;

  virtual bool survivor_is_full(AllocationContext_t context) const;
  virtual bool old_is_full(AllocationContext_t context) const;

  virtual void set_survivor_full(AllocationContext_t context);
  virtual void set_old_full(AllocationContext_t context);

  // Accessors to the allocation regions.
  virtual SurvivorGCAllocRegion* survivor_gc_alloc_region(AllocationContext_t context) = 0;
  virtual OldGCAllocRegion* old_gc_alloc_region(AllocationContext_t context) = 0;

  // Allocation attempt during GC for a survivor object / PLAB.
  inline HeapWord* survivor_attempt_allocation(size_t word_size,
                                               AllocationContext_t context);
  // Allocation attempt during GC for an old object / PLAB.
  inline HeapWord* old_attempt_allocation(size_t word_size,
                                          AllocationContext_t context);
  G1Allocator(G1CollectedHeap* heap) : _g1h(heap), _survivor_is_full(false), _old_is_full(false) { }
  virtual ~G1Allocator() { }

  static G1Allocator* create_allocator(G1CollectedHeap* g1h);

#ifdef ASSERT
  // Do we currently have an active mutator region to allocate into?
  bool has_mutator_alloc_region(AllocationContext_t context) { return mutator_alloc_region(context)->get() != NULL; }
  virtual void init_mutator_alloc_region() = 0;
  virtual void release_mutator_alloc_region() = 0;

  virtual void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
  virtual void release_gc_alloc_regions(EvacuationInfo& evacuation_info) = 0;
  virtual void abandon_gc_alloc_regions() = 0;

  // Management of retained regions.

  virtual bool is_retained_old_region(HeapRegion* hr) = 0;
  void reuse_retained_old_region(EvacuationInfo& evacuation_info,
                                 OldGCAllocRegion* old,
                                 HeapRegion** retained);

  // Allocate blocks of memory during mutator time.

  inline HeapWord* attempt_allocation(size_t word_size, AllocationContext_t context);
  inline HeapWord* attempt_allocation_locked(size_t word_size, AllocationContext_t context);
  inline HeapWord* attempt_allocation_force(size_t word_size, AllocationContext_t context);

  size_t unsafe_max_tlab_alloc(AllocationContext_t context);

  // Allocate blocks of memory during garbage collection. Will ensure an
  // allocation region, either by picking one or expanding the
  // heap, and then allocate a block of the given size. The block
  // may not be a humongous - it must fit into a single heap region.
  HeapWord* par_allocate_during_gc(InCSetState dest,
                                   size_t word_size,
                                   AllocationContext_t context);

  virtual size_t used_in_alloc_regions() = 0;

// The default allocation region manager for G1. Provides a single mutator, survivor
// and old generation allocation region.
// Can retain the (single) old generation allocation region across GCs.
class G1DefaultAllocator : public G1Allocator {
  // Alloc region used to satisfy mutator allocation requests.
  MutatorAllocRegion _mutator_alloc_region;

  // Alloc region used to satisfy allocation requests by the GC for
  // survivor objects.
  SurvivorGCAllocRegion _survivor_gc_alloc_region;

  // Alloc region used to satisfy allocation requests by the GC for
  // old objects.
  OldGCAllocRegion _old_gc_alloc_region;

  HeapRegion* _retained_old_gc_alloc_region;
  G1DefaultAllocator(G1CollectedHeap* heap) : G1Allocator(heap), _retained_old_gc_alloc_region(NULL) { }

  virtual void init_mutator_alloc_region();
  virtual void release_mutator_alloc_region();

  virtual void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
  virtual void release_gc_alloc_regions(EvacuationInfo& evacuation_info);
  virtual void abandon_gc_alloc_regions();

  virtual bool is_retained_old_region(HeapRegion* hr) {
    return _retained_old_gc_alloc_region == hr;

  virtual MutatorAllocRegion* mutator_alloc_region(AllocationContext_t context) {
    return &_mutator_alloc_region;

  virtual SurvivorGCAllocRegion* survivor_gc_alloc_region(AllocationContext_t context) {
    return &_survivor_gc_alloc_region;

  virtual OldGCAllocRegion* old_gc_alloc_region(AllocationContext_t context) {
    return &_old_gc_alloc_region;

  virtual size_t used_in_alloc_regions() {
    assert(Heap_lock->owner() != NULL,
           "Should be owned on this thread's behalf.");
    size_t result = 0;

    // Read only once in case it is set to NULL concurrently
    HeapRegion* hr = mutator_alloc_region(AllocationContext::current())->get();
    if (hr != NULL) {
      result += hr->used();
    return result;

class G1PLAB: public PLAB {
  bool _retired;

  G1PLAB(size_t gclab_word_size);
  virtual ~G1PLAB() {
    guarantee(_retired, "Allocation buffer has not been retired");

  virtual void set_buf(HeapWord* buf) {
    _retired = false;

  virtual void retire() {
    if (_retired) {
    _retired = true;

  virtual void flush_and_retire_stats(PLABStats* stats) {
    _retired = true;

// Manages the PLABs used during garbage collection. Interface for allocation from PLABs.
// Needs to handle multiple contexts, extra alignment in any "survivor" area and some
// statistics.
class G1PLABAllocator : public CHeapObj<mtGC> {
  friend class G1ParScanThreadState;
  G1CollectedHeap* _g1h;
  G1Allocator* _allocator;

  // The survivor alignment in effect in bytes.
  // == 0 : don't align survivors
  // != 0 : align survivors to that alignment
  // These values were chosen to favor the non-alignment case since some
  // architectures have a special compare against zero instructions.
  const uint _survivor_alignment_bytes;

  virtual void retire_alloc_buffers() = 0;
  virtual G1PLAB* alloc_buffer(InCSetState dest, AllocationContext_t context) = 0;

  // Calculate the survivor space object alignment in bytes. Returns that or 0 if
  // there are no restrictions on survivor alignment.
  static uint calc_survivor_alignment_bytes() {
    assert(SurvivorAlignmentInBytes >= ObjectAlignmentInBytes, "sanity");
    if (SurvivorAlignmentInBytes == ObjectAlignmentInBytes) {
      // No need to align objects in the survivors differently, return 0
      // which means "survivor alignment is not used".
      return 0;
    } else {
      assert(SurvivorAlignmentInBytes > 0, "sanity");
      return SurvivorAlignmentInBytes;

  HeapWord* allocate_new_plab(InCSetState dest,
                              size_t word_sz,
                              AllocationContext_t context);

  G1PLABAllocator(G1Allocator* allocator);
  virtual ~G1PLABAllocator() { }

  static G1PLABAllocator* create_allocator(G1Allocator* allocator);

  virtual void waste(size_t& wasted, size_t& undo_wasted) = 0;

  // Allocate word_sz words in dest, either directly into the regions or by
  // allocating a new PLAB. Returns the address of the allocated memory, NULL if
  // not successful. Plab_refill_failed indicates whether an attempt to refill the
  // PLAB failed or not.
  HeapWord* allocate_direct_or_new_plab(InCSetState dest,
                                        size_t word_sz,
                                        AllocationContext_t context,
                                        bool* plab_refill_failed);

  // Allocate word_sz words in the PLAB of dest.  Returns the address of the
  // allocated memory, NULL if not successful.
  HeapWord* plab_allocate(InCSetState dest,
                          size_t word_sz,
                          AllocationContext_t context) {
    G1PLAB* buffer = alloc_buffer(dest, context);
    if (_survivor_alignment_bytes == 0 || !dest.is_young()) {
      return buffer->allocate(word_sz);
    } else {
      return buffer->allocate_aligned(word_sz, _survivor_alignment_bytes);

  HeapWord* allocate(InCSetState dest,
                     size_t word_sz,
                     AllocationContext_t context,
                     bool* refill_failed) {
    HeapWord* const obj = plab_allocate(dest, word_sz, context);
    if (obj != NULL) {
      return obj;
    return allocate_direct_or_new_plab(dest, word_sz, context, refill_failed);

  void undo_allocation(InCSetState dest, HeapWord* obj, size_t word_sz, AllocationContext_t context);

// The default PLAB allocator for G1. Keeps the current (single) PLAB for survivor
// and old generation allocation.
class G1DefaultPLABAllocator : public G1PLABAllocator {
  G1PLAB  _surviving_alloc_buffer;
  G1PLAB  _tenured_alloc_buffer;
  G1PLAB* _alloc_buffers[InCSetState::Num];

  G1DefaultPLABAllocator(G1Allocator* _allocator);

  virtual G1PLAB* alloc_buffer(InCSetState dest, AllocationContext_t context) {
           err_msg("Allocation buffer index out-of-bounds: " CSETSTATE_FORMAT, dest.value()));
    assert(_alloc_buffers[dest.value()] != NULL,
           err_msg("Allocation buffer is NULL: " CSETSTATE_FORMAT, dest.value()));
    return _alloc_buffers[dest.value()];

  virtual void retire_alloc_buffers();

  virtual void waste(size_t& wasted, size_t& undo_wasted);

// G1ArchiveAllocator is used to allocate memory in archive
// regions. Such regions are not modifiable by GC, being neither
// scavenged nor compacted, or even marked in the object header.
// They can contain no pointers to non-archive heap regions,
class G1ArchiveAllocator : public CHeapObj<mtGC> {

  G1CollectedHeap* _g1h;

  // The current allocation region
  HeapRegion* _allocation_region;

  // Regions allocated for the current archive range.
  GrowableArray<HeapRegion*> _allocated_regions;

  // The number of bytes used in the current range.
  size_t _summary_bytes_used;

  // Current allocation window within the current region.
  HeapWord* _bottom;
  HeapWord* _top;
  HeapWord* _max;

  // Allocate a new region for this archive allocator.
  // Allocation is from the top of the reserved heap downward.
  bool alloc_new_region();

  G1ArchiveAllocator(G1CollectedHeap* g1h) :
    _allocated_regions((ResourceObj::set_allocation_type((address) &_allocated_regions,
                        2), true /* C_Heap */),
    _max(NULL) { }

  virtual ~G1ArchiveAllocator() {
    assert(_allocation_region == NULL, "_allocation_region not NULL");

  static G1ArchiveAllocator* create_allocator(G1CollectedHeap* g1h);

  // Allocate memory for an individual object.
  HeapWord* archive_mem_allocate(size_t word_size);

  // Return the memory ranges used in the current archive, after
  // aligning to the requested alignment.
  void complete_archive(GrowableArray<MemRegion>* ranges,
                        size_t end_alignment_in_bytes);

  // The number of bytes allocated by this allocator.
  size_t used() {
    return _summary_bytes_used;

  // Clear the count of bytes allocated in prior G1 regions. This
  // must be done when recalculate_use is used to reset the counter
  // for the generic allocator, since it counts bytes in all G1
  // regions, including those still associated with this allocator.
  void clear_used() {
    _summary_bytes_used = 0;