g1Allocator.hpp

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#ifndef SHARE_GC_G1_G1ALLOCATOR_HPP
#define SHARE_GC_G1_G1ALLOCATOR_HPP

#include "gc/g1/g1AllocRegion.hpp"
#include "gc/g1/g1HeapRegionAttr.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/plab.hpp"

class G1EvacuationInfo;
class G1NUMA;

// 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;

private:
  G1CollectedHeap* _g1h;
  G1NUMA* _numa;

  bool _survivor_is_full;
  bool _old_is_full;

  // The number of MutatorAllocRegions used, one per memory node.
  size_t _num_alloc_regions;

  // Alloc region used to satisfy mutator allocation requests.
  MutatorAllocRegion* _mutator_alloc_regions;

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

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

  HeapRegion* _retained_old_gc_alloc_region;

  bool survivor_is_full() const;
  bool old_is_full() const;

  void set_survivor_full();
  void set_old_full();

  void reuse_retained_old_region(G1EvacuationInfo& evacuation_info,
                                 OldGCAllocRegion* old,
                                 HeapRegion** retained);

  // Accessors to the allocation regions.
  inline MutatorAllocRegion* mutator_alloc_region(uint node_index);
  inline SurvivorGCAllocRegion* survivor_gc_alloc_region(uint node_index);
  inline OldGCAllocRegion* old_gc_alloc_region();

  // Allocation attempt during GC for a survivor object / PLAB.
  HeapWord* survivor_attempt_allocation(size_t min_word_size,
                                        size_t desired_word_size,
                                        size_t* actual_word_size,
                                        uint node_index);

  // Allocation attempt during GC for an old object / PLAB.
  HeapWord* old_attempt_allocation(size_t min_word_size,
                                   size_t desired_word_size,
                                   size_t* actual_word_size);

  // Node index of current thread.
  inline uint current_node_index() const;

public:
  G1Allocator(G1CollectedHeap* heap);
  ~G1Allocator();

  uint num_nodes() { return (uint)_num_alloc_regions; }

#ifdef ASSERT
  // Do we currently have an active mutator region to allocate into?
  bool has_mutator_alloc_region();
#endif

  void init_mutator_alloc_regions();
  void release_mutator_alloc_regions();

  void init_gc_alloc_regions(G1EvacuationInfo& evacuation_info);
  void release_gc_alloc_regions(G1EvacuationInfo& evacuation_info);
  void abandon_gc_alloc_regions();
  bool is_retained_old_region(HeapRegion* hr);

  // Allocate blocks of memory during mutator time.

  // Attempt allocation in the current alloc region.
  inline HeapWord* attempt_allocation(size_t min_word_size,
                                      size_t desired_word_size,
                                      size_t* actual_word_size);

  // Attempt allocation, retiring the current region and allocating a new one. It is
  // assumed that attempt_allocation() has been tried and failed already first.
  inline HeapWord* attempt_allocation_using_new_region(size_t word_size);

  // This is to be called when holding an appropriate lock. It first tries in the
  // current allocation region, and then attempts an allocation using a new region.
  inline HeapWord* attempt_allocation_locked(size_t word_size);

  inline HeapWord* attempt_allocation_force(size_t word_size);

  size_t unsafe_max_tlab_alloc();
  size_t used_in_alloc_regions();

  // 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(G1HeapRegionAttr dest,
                                   size_t word_size,
                                   uint node_index);

  HeapWord* par_allocate_during_gc(G1HeapRegionAttr dest,
                                   size_t min_word_size,
                                   size_t desired_word_size,
                                   size_t* actual_word_size,
                                   uint node_index);
};

// 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;
private:
  typedef G1HeapRegionAttr::region_type_t region_type_t;

  G1CollectedHeap* _g1h;
  G1Allocator* _allocator;

  PLAB** _alloc_buffers[G1HeapRegionAttr::Num];

  // Number of words allocated directly (not counting PLAB allocation).
  size_t _direct_allocated[G1HeapRegionAttr::Num];

  void flush_and_retire_stats();
  inline PLAB* alloc_buffer(G1HeapRegionAttr dest, uint node_index) const;
  inline PLAB* alloc_buffer(region_type_t dest, uint node_index) const;

  // Returns the number of allocation buffers for the given dest.
  // There is only 1 buffer for Old while Young may have multiple buffers depending on
  // active NUMA nodes.
  inline uint alloc_buffers_length(region_type_t dest) const;

  bool may_throw_away_buffer(size_t const allocation_word_sz, size_t const buffer_size) const;
public:
  G1PLABAllocator(G1Allocator* allocator);
  ~G1PLABAllocator();

  size_t waste() const;
  size_t undo_waste() const;

  // 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(G1HeapRegionAttr dest,
                                        size_t word_sz,
                                        bool* plab_refill_failed,
                                        uint node_index);

  // Allocate word_sz words in the PLAB of dest.  Returns the address of the
  // allocated memory, NULL if not successful.
  inline HeapWord* plab_allocate(G1HeapRegionAttr dest,
                                 size_t word_sz,
                                 uint node_index);

  inline HeapWord* allocate(G1HeapRegionAttr dest,
                            size_t word_sz,
                            bool* refill_failed,
                            uint node_index);

  void undo_allocation(G1HeapRegionAttr dest, HeapWord* obj, size_t word_sz, uint node_index);
};

// G1ArchiveAllocator is used to allocate memory in archive
// regions. Such regions are not scavenged nor compacted by GC.
// There are two types of archive regions, which are
// differ in the kind of references allowed for the contained objects:
//
// - 'Closed' archive region contain no references outside of other
//   closed archive regions. The region is immutable by GC. GC does
//   not mark object header in 'closed' archive region.
// - An 'open' archive region allow references to any other regions,
//   including closed archive, open archive and other java heap regions.
//   GC can adjust pointers and mark object header in 'open' archive region.
class G1ArchiveAllocator : public CHeapObj<mtGC> {
protected:
  bool _open; // Indicate if the region is 'open' archive.
  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();

public:
  G1ArchiveAllocator(G1CollectedHeap* g1h, bool open) :
    _open(open),
    _g1h(g1h),
    _allocation_region(NULL),
    _allocated_regions((ResourceObj::set_allocation_type((address) &_allocated_regions,
                                                         ResourceObj::C_HEAP),
                        2), mtGC),
    _summary_bytes_used(0),
    _bottom(NULL),
    _top(NULL),
    _max(NULL) { }

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

  static G1ArchiveAllocator* create_allocator(G1CollectedHeap* g1h, bool open);

  // 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;
  }
};

#endif // SHARE_GC_G1_G1ALLOCATOR_HPP