metaspaceSettings.hpp

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#ifndef SHARE_MEMORY_METASPACE_METASPACESETTINGS_HPP
#define SHARE_MEMORY_METASPACE_METASPACESETTINGS_HPP

#include "memory/allocation.hpp"
#include "memory/metaspace/chunklevel.hpp"
#include "utilities/globalDefinitions.hpp"

namespace metaspace {

class Settings : public AllStatic {

  // Granularity, in bytes, metaspace is committed with.
  static size_t _commit_granule_bytes;

  // Granularity, in words, metaspace is committed with.
  static size_t _commit_granule_words;

  // The default size of a VirtualSpaceNode, unless created with an explicitly specified size.
  //  Must be a multiple of the root chunk size.
  // Increasing this value decreases the number of mappings used for metadata,
  //  at the cost of increased virtual size used for Metaspace (or, at least,
  //  coarser growth steps). Matters mostly for 32bit platforms due to limited
  //  address space.
  // The default of two root chunks has been chosen on a whim but seems to work out okay
  //  (coming to a mapping size of 8m per node).
  static const size_t _virtual_space_node_default_word_size = chunklevel::MAX_CHUNK_WORD_SIZE * 2;

  // Alignment of the base address of a virtual space node
  static const size_t _virtual_space_node_reserve_alignment_words = chunklevel::MAX_CHUNK_WORD_SIZE;

  // When allocating from a chunk, if the remaining area in the chunk is too small to hold
  // the requested size, we attempt to double the chunk size in place...
  static const bool _enlarge_chunks_in_place = true;

  // Whether or not chunks handed out to an arena start out fully committed;
  // if true, this deactivates committing-on-demand (regardless of whether
  // we uncommit free chunks).
  static bool _new_chunks_are_fully_committed;

  // If true, chunks equal or larger than a commit granule are uncommitted
  // after being returned to the freelist.
  static bool _uncommit_free_chunks;

  // If true, metablock allocations are guarded and periodically checked.
  DEBUG_ONLY(static bool _use_allocation_guard;)

  // This enables or disables premature deallocation of metaspace allocated blocks. Using
  //  Metaspace::deallocate(), blocks can be returned prematurely (before the associated
  //  Arena dies, e.g. after class unloading) and can be reused by the arena.
  //  If disabled, those blocks will not be reused until the Arena dies.
  // Note that premature deallocation is rare under normal circumstances.
  // By default deallocation handling is enabled.
  DEBUG_ONLY(static bool _handle_deallocations;)

public:

  static size_t commit_granule_bytes()                        { return _commit_granule_bytes; }
  static size_t commit_granule_words()                        { return _commit_granule_words; }
  static bool new_chunks_are_fully_committed()                { return _new_chunks_are_fully_committed; }
  static size_t virtual_space_node_default_word_size()        { return _virtual_space_node_default_word_size; }
  static size_t virtual_space_node_reserve_alignment_words()  { return _virtual_space_node_reserve_alignment_words; }
  static bool enlarge_chunks_in_place()                       { return _enlarge_chunks_in_place; }
  static bool uncommit_free_chunks()                          { return _uncommit_free_chunks; }
  static bool use_allocation_guard()                          { return DEBUG_ONLY(_use_allocation_guard) NOT_DEBUG(false); }
  static bool handle_deallocations()                          { return DEBUG_ONLY(_handle_deallocations) NOT_DEBUG(true); }

  static void ergo_initialize();

  static void print_on(outputStream* st);

};

} // namespace metaspace

#endif // SHARE_MEMORY_METASPACE_METASPACESETTINGS_HPP