view src/share/vm/memory/generationSpec.hpp @ 1716:be3f9c242c9d

6948538: CMS: BOT walkers can fall into object allocation and initialization cracks Summary: GC workers now recognize an intermediate transient state of blocks which are allocated but have not yet completed initialization. blk_start() calls do not attempt to determine the size of a block in the transient state, rather waiting for the block to become initialized so that it is safe to query its size. Audited and ensured the order of initialization of object fields (klass, free bit and size) to respect block state transition protocol. Also included some new assertion checking code enabled in debug mode. Reviewed-by: chrisphi, johnc, poonam
author ysr
date Mon, 16 Aug 2010 15:58:42 -0700
parents c18cbe5936b8
children f95d63e2154a
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/*
 * Copyright (c) 2001, 2004, Oracle and/or its affiliates. All rights reserved.
 * 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.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

// The specification of a generation.  This class also encapsulates
// some generation-specific behavior.  This is done here rather than as a
// virtual function of Generation because these methods are needed in
// initialization of the Generations.
class GenerationSpec : public CHeapObj {
  friend class VMStructs;
private:
  Generation::Name _name;
  size_t           _init_size;
  size_t           _max_size;

public:
  GenerationSpec(Generation::Name name, size_t init_size, size_t max_size) {
    _name = name;
    _init_size = init_size;
    _max_size = max_size;
  }

  Generation* init(ReservedSpace rs, int level, GenRemSet* remset);

  // Accessors
  Generation::Name name()        const { return _name; }
  size_t init_size()             const { return _init_size; }
  void set_init_size(size_t size)      { _init_size = size; }
  size_t max_size()              const { return _max_size; }
  void set_max_size(size_t size)       { _max_size = size; }

  // Alignment
  void align(size_t alignment) {
    set_init_size(align_size_up(init_size(), alignment));
    set_max_size(align_size_up(max_size(), alignment));
  }

  // Return the number of regions contained in the generation which
  // might need to be independently covered by a remembered set.
  virtual int n_covered_regions() const { return 1; }
};

typedef GenerationSpec* GenerationSpecPtr;

// The specification of a permanent generation. This class is very
// similar to GenerationSpec in use. Due to PermGen's not being a
// true Generation, we cannot combine the spec classes either.
class PermanentGenerationSpec : public CHeapObj {
  friend class VMStructs;
private:
  PermGen::Name    _name;
  size_t           _init_size;
  size_t           _max_size;
  size_t           _read_only_size;
  size_t           _read_write_size;
  size_t           _misc_data_size;
  size_t           _misc_code_size;
  bool             _enable_shared_spaces;

  enum {
    _n_spaces = 2
  };

public:
  PermanentGenerationSpec(PermGen::Name name, size_t init_size,
                          size_t max_size, size_t read_only_size,
                          size_t read_write_size, size_t misc_data_size,
                          size_t misc_code_size);

  PermGen* init(ReservedSpace rs, size_t init_size, GenRemSet* remset);

  void disable_sharing() {
    _enable_shared_spaces = false;
    _read_only_size = 0;
    _read_write_size = 0;
    _misc_data_size = 0;
    _misc_code_size = 0;
  }

  // Accessors
  PermGen::Name name()           const { return _name; }
  size_t init_size()             const { return _init_size; }
  void set_init_size(size_t size)      { _init_size = size; }

  // Max size for user DOES NOT include shared spaces.
  // Max size for space allocation DOES include shared spaces.
  size_t max_size() const {
    return _max_size + _read_only_size + _read_write_size;
  }

  // Need one covered region for the main space, and one for the shared
  // spaces (together).
  int n_covered_regions() const { return 2; }

  void align(size_t alignment);

  size_t read_only_size() const { return _read_only_size; }
  size_t read_write_size() const { return _read_write_size; }
  size_t misc_data_size() const { return _misc_data_size; }
  size_t misc_code_size() const { return _misc_code_size; }
  bool enable_shared_spaces()    const { return _enable_shared_spaces; }
};