metablock.cpp

/*
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#include "precompiled.hpp"
#include "memory/allocation.hpp"
#include "memory/metablock.hpp"
#include "utilities/copy.hpp"
#include "utilities/debug.hpp"

// Blocks of space for metadata are allocated out of Metachunks.
//
// Metachunk are allocated out of MetadataVirtualspaces and once
// allocated there is no explicit link between a Metachunk and
// the MetadataVirtualspaces from which it was allocated.
//
// Each SpaceManager maintains a
// list of the chunks it is using and the current chunk.  The current
// chunk is the chunk from which allocations are done.  Space freed in
// a chunk is placed on the free list of blocks (BlockFreelist) and
// reused from there.
//
// Future modification
//
// The Metachunk can conceivable be replaced by the Chunk in
// allocation.hpp.  Note that the latter Chunk is the space for
// allocation (allocations from the chunk are out of the space in
// the Chunk after the header for the Chunk) where as Metachunks
// point to space in a VirtualSpace.  To replace Metachunks with
// Chunks, change Chunks so that they can be allocated out of a VirtualSpace.
size_t Metablock::_min_block_byte_size = sizeof(Metablock);

#ifdef ASSERT
size_t Metablock::_overhead =
  Chunk::aligned_overhead_size(sizeof(Metablock)) / BytesPerWord;
#else
size_t Metablock::_overhead = 0;
#endif

// New blocks returned by the Metaspace are zero initialized.
// We should fix the constructors to not assume this instead.
Metablock* Metablock::initialize(MetaWord* p, size_t word_size) {
  if (p == NULL) {
    return NULL;
  }

  Metablock* result = (Metablock*) p;
#ifdef ASSERT
  // Add just to catch missing initializations
  Copy::fill_to_words((HeapWord*) result, word_size, 0xf1f1f1f1);
  result->set_word_size(word_size);
#endif
  return result;
}