src/hotspot/share/gc/g1/g1RegionPinCache.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * 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).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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#ifndef SHARE_GC_G1_G1REGIONPINCACHE_HPP
#define SHARE_GC_G1_G1REGIONPINCACHE_HPP

#include "gc/g1/g1HeapRegion.hpp"
#include "memory/allocation.hpp"
#include "utilities/globalDefinitions.hpp"

// Holds (caches) the pending pinned object count adjustment for the region
// _region_idx on a per thread basis.
// Keeping such a cache avoids the expensive atomic operations when updating the
// pin count for the very common case that the application pins and unpins the
// same object without any interleaving by a garbage collection or pinning/unpinning
// to an object in another region.
class G1RegionPinCache : public StackObj {
  uint _region_idx;
  size_t _count;

  void flush_and_set(uint new_region_idx, size_t new_count);

public:
  G1RegionPinCache() : _region_idx(G1_NO_HRM_INDEX), _count(0) { }

#ifdef ASSERT
  size_t count() const { return _count; }
#endif

  void inc_count(uint region_idx);
  void dec_count(uint region_idx);

  void flush();
};

#endif /* SHARE_GC_G1_G1REGIONPINCACHE_HPP */