jdk/src/hotspot/share/gc/parallel/mutableSpace.hpp

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#ifndef SHARE_GC_PARALLEL_MUTABLESPACE_HPP
#define SHARE_GC_PARALLEL_MUTABLESPACE_HPP

#include "memory/allocation.hpp"
#include "memory/iterator.hpp"
#include "memory/memRegion.hpp"
#include "runtime/atomic.hpp"
#include "utilities/copy.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/macros.hpp"

class WorkerThreads;

// A MutableSpace supports the concept of allocation. This includes the
// concepts that a space may be only partially full, and the query methods
// that go with such an assumption.
//
// MutableSpace is also responsible for minimizing the
// page allocation time by having the memory pretouched (with
// AlwaysPretouch) and for optimizing page placement on NUMA systems
// by make the underlying region interleaved (with UseNUMA).
//
// Invariant: bottom() <= top() <= end()
// top() and end() are exclusive.

class MutableSpace: public CHeapObj<mtGC> {
  friend class VMStructs;

  // The last region which page had been setup to be interleaved.
  MemRegion _last_setup_region;
  size_t _page_size;
  HeapWord* _bottom;
  Atomic<HeapWord*> _top;
  Atomic<HeapWord*> _end;

  void numa_setup_pages(MemRegion mr, bool clear_space);

  void set_last_setup_region(MemRegion mr) { _last_setup_region = mr;   }
  MemRegion last_setup_region() const      { return _last_setup_region; }

protected:
  size_t page_size() const                 { return _page_size;         }

  Atomic<HeapWord*>* top_addr()            { return &_top;              }

public:
  virtual ~MutableSpace() = default;
  MutableSpace(size_t page_size);

  // Accessors
  HeapWord* bottom() const                 { return _bottom; }
  HeapWord* top() const                    { return _top.load_relaxed(); }
  HeapWord* end() const                    { return _end.load_relaxed(); }

  void set_bottom(HeapWord* value)         { _bottom = value; }
  virtual void set_top(HeapWord* value)    { _top.store_relaxed(value); }
  void set_end(HeapWord* value)            { _end.store_relaxed(value); }

  MemRegion region() const { return MemRegion(bottom(), end()); }

  size_t capacity_in_bytes() const { return capacity_in_words() * HeapWordSize; }
  size_t capacity_in_words() const { return pointer_delta(end(), bottom()); }

  // Returns a subregion containing all objects in this space.
  MemRegion used_region() { return MemRegion(bottom(), top()); }

  static const bool SetupPages = true;
  static const bool DontSetupPages = false;

  // Initialization
  virtual void initialize(MemRegion mr,
                          bool clear_space,
                          bool mangle_space,
                          bool setup_pages = SetupPages,
                          WorkerThreads* pretouch_workers = nullptr);

  virtual void clear(bool mangle_space);
  virtual void update() { }
  virtual void accumulate_statistics() { }

  virtual void mangle_unused_area() PRODUCT_RETURN;
  virtual void mangle_region(MemRegion mr) PRODUCT_RETURN;

  virtual void ensure_parsability() { }

  // Boolean queries.
  bool is_empty() const              { return used_in_words() == 0; }
  bool not_empty() const             { return used_in_words() > 0; }
  bool contains(const void* p) const { return _bottom <= p && p < end(); }

  // Size computations.  Sizes are in bytes.
  size_t used_in_bytes() const                { return used_in_words() * HeapWordSize; }
  size_t free_in_bytes() const                { return free_in_words() * HeapWordSize; }

  // Size computations.  Sizes are in heapwords.
  virtual size_t used_in_words() const         { return pointer_delta(top(), bottom()); }
  virtual size_t free_in_words() const         { return pointer_delta(end(),    top()); }
  virtual size_t tlab_capacity() const         { return capacity_in_bytes();            }
  virtual size_t tlab_used() const             { return used_in_bytes();                }
  virtual size_t unsafe_max_tlab_alloc() const { return free_in_bytes();                }

  // Allocation (return null if full)
  virtual HeapWord* cas_allocate(size_t word_size);
  // Optional deallocation. Used in NUMA-allocator.
  bool cas_deallocate(HeapWord *obj, size_t size);

  // Iteration.
  void oop_iterate(OopIterateClosure* cl);
  void object_iterate(ObjectClosure* cl);

  // Debugging
  virtual void print() const;
  virtual void print_on(outputStream* st, const char* prefix) const;
  virtual void print_short() const;
  virtual void print_short_on(outputStream* st) const;
  virtual void verify();
};

#endif // SHARE_GC_PARALLEL_MUTABLESPACE_HPP