src/hotspot/share/memory/metaspace/blockFreelist.hpp

/*
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 * 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.
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#ifndef SHARE_MEMORY_METASPACE_BLOCKFREELIST_HPP
#define SHARE_MEMORY_METASPACE_BLOCKFREELIST_HPP

#include "memory/allocation.hpp"
#include "memory/binaryTreeDictionary.hpp"
#include "memory/freeList.hpp"
#include "memory/metaspace/smallBlocks.hpp"
#include "memory/metaspace/metablock.hpp"
#include "utilities/globalDefinitions.hpp"

namespace metaspace {

typedef BinaryTreeDictionary<Metablock, FreeList<Metablock> > BlockTreeDictionary;

// Used to manage the free list of Metablocks (a block corresponds
// to the allocation of a quantum of metadata).
class BlockFreelist : public CHeapObj<mtClass> {

  BlockTreeDictionary* const _dictionary;
  SmallBlocks* _small_blocks;

  // Only allocate and split from freelist if the size of the allocation
  // is at least 1/4th the size of the available block.
  const static int WasteMultiplier = 4;

  // Accessors
  BlockTreeDictionary* dictionary() const { return _dictionary; }
  SmallBlocks* small_blocks() {
    if (_small_blocks == NULL) {
      _small_blocks = new SmallBlocks();
    }
    return _small_blocks;
  }

 public:

  BlockFreelist();
  ~BlockFreelist();

  // Get and return a block to the free list
  MetaWord* get_block(size_t word_size);
  void return_block(MetaWord* p, size_t word_size);

  // Returns the total size, in words, of all blocks kept in this structure.
  size_t total_size() const  {
    size_t result = dictionary()->total_size();
    if (_small_blocks != NULL) {
      result = result + _small_blocks->total_size();
    }
    return result;
  }

  // Returns the number of all blocks kept in this structure.
  uintx num_blocks() const {
    uintx result = dictionary()->total_free_blocks();
    if (_small_blocks != NULL) {
      result = result + _small_blocks->total_num_blocks();
    }
    return result;
  }

  static size_t min_dictionary_size()   { return TreeChunk<Metablock, FreeList<Metablock> >::min_size(); }
  void print_on(outputStream* st) const;
};

} // namespace metaspace

#endif /* SHARE_MEMORY_METASPACE_BLOCKFREELIST_HPP */