jdk-24/hotspot/src/share/vm/memory/metaspace.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * published by the Free Software Foundation.
 *
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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).
 *
 * 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_VM_MEMORY_METASPACE_HPP
#define SHARE_VM_MEMORY_METASPACE_HPP

#include "memory/allocation.hpp"
#include "memory/memRegion.hpp"
#include "runtime/virtualspace.hpp"
#include "utilities/exceptions.hpp"

// Metaspace
//
// Metaspaces are Arenas for the VM's metadata.
// They are allocated one per class loader object, and one for the null
// bootstrap class loader
// Eventually for bootstrap loader we'll have a read-only section and read-write
// to write for DumpSharedSpaces and read for UseSharedSpaces
//
//    block X ---+       +-------------------+
//               |       |  Virtualspace     |
//               |       |                   |
//               |       |                   |
//               |       |-------------------|
//               |       || Chunk            |
//               |       ||                  |
//               |       ||----------        |
//               +------>||| block 0 |       |
//                       ||----------        |
//                       ||| block 1 |       |
//                       ||----------        |
//                       ||                  |
//                       |-------------------|
//                       |                   |
//                       |                   |
//                       +-------------------+
//

class ClassLoaderData;
class MetaWord;
class Mutex;
class outputStream;
class FreeChunk;
template <class Chunk_t> class FreeList;
template <class Chunk_t> class BinaryTreeDictionary;
class SpaceManager;

// Metaspaces each have a  SpaceManager and allocations
// are done by the SpaceManager.  Allocations are done
// out of the current Metachunk.  When the current Metachunk
// is exhausted, the SpaceManager gets a new one from
// the current VirtualSpace.  When the VirtualSpace is exhausted
// the SpaceManager gets a new one.  The SpaceManager
// also manages freelists of available Chunks.
//
// Currently the space manager maintains the list of
// virtual spaces and the list of chunks in use.  Its
// allocate() method returns a block for use as a
// quantum of metadata.

class VirtualSpaceList;

class Metaspace : public CHeapObj<mtClass> {
  friend class VMStructs;
  friend class SpaceManager;
  friend class VM_CollectForMetadataAllocation;
  friend class MetaspaceGC;
  friend class MetaspaceAux;

 public:
  enum MetadataType {ClassType, NonClassType};

 private:
  void initialize(Mutex* lock, size_t initial_size = 0);

  static size_t _first_chunk_word_size;

  SpaceManager* _vsm;
  SpaceManager* vsm() const { return _vsm; }

  SpaceManager* _class_vsm;
  SpaceManager* class_vsm() const { return _class_vsm; }

  MetaWord* allocate(size_t word_size, MetadataType mdtype);

  // Virtual Space lists for both classes and other metadata
  static VirtualSpaceList* _space_list;
  static VirtualSpaceList* _class_space_list;

  static VirtualSpaceList* space_list()       { return _space_list; }
  static VirtualSpaceList* class_space_list() { return _class_space_list; }

 public:

  Metaspace(Mutex* lock, size_t initial_size);
  Metaspace(Mutex* lock);
  ~Metaspace();

  // Initialize globals for Metaspace
  static void global_initialize();
  static void initialize_class_space(ReservedSpace rs);

  static size_t first_chunk_word_size() { return _first_chunk_word_size; }

  char*  bottom() const;
  size_t used_words(MetadataType mdtype) const;
  size_t free_words(MetadataType mdtype) const;
  size_t capacity_words(MetadataType mdtype) const;
  size_t waste_words(MetadataType mdtype) const;

  static MetaWord* allocate(ClassLoaderData* loader_data, size_t size,
                            bool read_only, MetadataType mdtype, TRAPS);
  void deallocate(MetaWord* ptr, size_t byte_size, bool is_class);

  MetaWord* expand_and_allocate(size_t size,
                                MetadataType mdtype);

#ifndef PRODUCT
  bool contains(const void *ptr) const;
  bool contains_class(const void *ptr) const;
#endif

  void dump(outputStream* const out) const;

  void print_on(outputStream* st) const;
  // Debugging support
  void verify();
};

class MetaspaceAux : AllStatic {

  // Statistics for class space and data space in metaspace.
  static size_t used_in_bytes(Metaspace::MetadataType mdtype);
  static size_t free_in_bytes(Metaspace::MetadataType mdtype);
  static size_t capacity_in_bytes(Metaspace::MetadataType mdtype);
  static size_t reserved_in_bytes(Metaspace::MetadataType mdtype);

  static size_t free_chunks_total(Metaspace::MetadataType mdtype);
  static size_t free_chunks_total_in_bytes(Metaspace::MetadataType mdtype);

 public:
  // Total of space allocated to metadata in all Metaspaces
  static size_t used_in_bytes() {
    return used_in_bytes(Metaspace::ClassType) +
           used_in_bytes(Metaspace::NonClassType);
  }

  // Total of available space in all Metaspaces
  // Total of capacity allocated to all Metaspaces.  This includes
  // space in Metachunks not yet allocated and in the Metachunk
  // freelist.
  static size_t capacity_in_bytes() {
    return capacity_in_bytes(Metaspace::ClassType) +
           capacity_in_bytes(Metaspace::NonClassType);
  }

  // Total space reserved in all Metaspaces
  static size_t reserved_in_bytes() {
    return reserved_in_bytes(Metaspace::ClassType) +
           reserved_in_bytes(Metaspace::NonClassType);
  }

  static size_t min_chunk_size();

  // Print change in used metadata.
  static void print_metaspace_change(size_t prev_metadata_used);
  static void print_on(outputStream * out);
  static void print_on(outputStream * out, Metaspace::MetadataType mdtype);

  static void print_waste(outputStream* out);
  static void dump(outputStream* out);
};

// Metaspace are deallocated when their class loader are GC'ed.
// This class implements a policy for inducing GC's to recover
// Metaspaces.

class MetaspaceGC : AllStatic {

  // The current high-water-mark for inducing a GC.  When
  // the capacity of all space in the virtual lists reaches this value,
  // a GC is induced and the value is increased.  This should be changed
  // to the space actually used for allocations to avoid affects of
  // fragmentation losses to partially used chunks.  Size is in words.
  static size_t _capacity_until_GC;

  // After a GC is done any allocation that fails should try to expand
  // the capacity of the Metaspaces.  This flag is set during attempts
  // to allocate in the VMGCOperation that does the GC.
  static bool _expand_after_GC;

  // For a CMS collection, signal that a concurrent collection should
  // be started.
  static bool _should_concurrent_collect;

  static uint _shrink_factor;

  static void set_capacity_until_GC(size_t v) { _capacity_until_GC = v; }

  static size_t shrink_factor() { return _shrink_factor; }
  void set_shrink_factor(uint v) { _shrink_factor = v; }

 public:

  static size_t capacity_until_GC() { return _capacity_until_GC; }
  static size_t capacity_until_GC_in_bytes() { return _capacity_until_GC * BytesPerWord; }
  static void inc_capacity_until_GC(size_t v) { _capacity_until_GC += v; }
  static void dec_capacity_until_GC(size_t v) {
    _capacity_until_GC = _capacity_until_GC > v ? _capacity_until_GC - v : 0;
  }
  static bool expand_after_GC()           { return _expand_after_GC; }
  static void set_expand_after_GC(bool v) { _expand_after_GC = v; }

  static bool should_concurrent_collect() { return _should_concurrent_collect; }
  static void set_should_concurrent_collect(bool v) {
    _should_concurrent_collect = v;
  }

  // The amount to increase the high-water-mark (_capacity_until_GC)
  static size_t delta_capacity_until_GC(size_t word_size);

  // It is expected that this will be called when the current capacity
  // has been used and a GC should be considered.
  static bool should_expand(VirtualSpaceList* vsl, size_t word_size);

  // Calculate the new high-water mark at which to induce
  // a GC.
  static void compute_new_size();
};

#endif // SHARE_VM_MEMORY_METASPACE_HPP