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1 /*
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2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 *
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23 */
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24 #ifndef SHARE_VM_MEMORY_METACHUNK_HPP
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25 #define SHARE_VM_MEMORY_METACHUNK_HPP
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26
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27 #include "memory/allocation.hpp"
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28 #include "utilities/debug.hpp"
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29 #include "utilities/globalDefinitions.hpp"
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30
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31 class VirtualSpaceNode;
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32
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33 // Super class of Metablock and Metachunk to allow them to
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34 // be put on the FreeList and in the BinaryTreeDictionary.
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35 template <class T>
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36 class Metabase VALUE_OBJ_CLASS_SPEC {
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37 size_t _word_size;
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38 T* _next;
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39 T* _prev;
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40
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41 protected:
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42 Metabase(size_t word_size) : _word_size(word_size), _next(NULL), _prev(NULL) {}
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43
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44 public:
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45 T* next() const { return _next; }
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46 T* prev() const { return _prev; }
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47 void set_next(T* v) { _next = v; assert(v != this, "Boom");}
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48 void set_prev(T* v) { _prev = v; assert(v != this, "Boom");}
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49 void clear_next() { set_next(NULL); }
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50 void clear_prev() { set_prev(NULL); }
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51
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52 size_t size() const volatile { return _word_size; }
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53 void set_size(size_t v) { _word_size = v; }
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54
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55 void link_next(T* ptr) { set_next(ptr); }
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56 void link_prev(T* ptr) { set_prev(ptr); }
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57 void link_after(T* ptr) {
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58 link_next(ptr);
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59 if (ptr != NULL) ptr->link_prev((T*)this);
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60 }
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61
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62 uintptr_t* end() const { return ((uintptr_t*) this) + size(); }
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63
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64 bool cantCoalesce() const { return false; }
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65
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66 // Debug support
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67 #ifdef ASSERT
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68 void* prev_addr() const { return (void*)&_prev; }
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69 void* next_addr() const { return (void*)&_next; }
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70 void* size_addr() const { return (void*)&_word_size; }
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71 #endif
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72 bool verify_chunk_in_free_list(T* tc) const { return true; }
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73 bool verify_par_locked() { return true; }
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74
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75 void assert_is_mangled() const {/* Don't check "\*/}
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76
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77 bool is_free() { return true; }
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78 };
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79
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80 // Metachunk - Quantum of allocation from a Virtualspace
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81 // Metachunks are reused (when freed are put on a global freelist) and
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82 // have no permanent association to a SpaceManager.
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83
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84 // +--------------+ <- end --+ --+
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85 // | | | |
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86 // | | | free |
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87 // | | | |
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88 // | | | | size | capacity
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89 // | | | |
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90 // | | <- top -- + |
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91 // | | | |
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92 // | | | used |
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93 // | | | |
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94 // | | | |
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95 // +--------------+ <- bottom --+ --+
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96
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97 class Metachunk : public Metabase<Metachunk> {
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98 friend class TestMetachunk;
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99 // The VirtualSpaceNode containing this chunk.
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100 VirtualSpaceNode* _container;
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101
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102 // Current allocation top.
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103 MetaWord* _top;
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104
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105 DEBUG_ONLY(bool _is_tagged_free;)
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106
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107 MetaWord* initial_top() const { return (MetaWord*)this + overhead(); }
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108 MetaWord* top() const { return _top; }
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109
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110 public:
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111 // Metachunks are allocated out of a MetadataVirtualSpace and
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112 // and use some of its space to describe itself (plus alignment
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113 // considerations). Metadata is allocated in the rest of the chunk.
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114 // This size is the overhead of maintaining the Metachunk within
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115 // the space.
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116
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117 // Alignment of each allocation in the chunks.
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118 static size_t object_alignment();
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119
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120 // Size of the Metachunk header, including alignment.
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121 static size_t overhead();
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122
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123 Metachunk(size_t word_size , VirtualSpaceNode* container);
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124
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125 MetaWord* allocate(size_t word_size);
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126
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127 VirtualSpaceNode* container() const { return _container; }
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128
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129 MetaWord* bottom() const { return (MetaWord*) this; }
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130
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131 // Reset top to bottom so chunk can be reused.
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132 void reset_empty() { _top = initial_top(); clear_next(); clear_prev(); }
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133 bool is_empty() { return _top == initial_top(); }
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134
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135 // used (has been allocated)
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136 // free (available for future allocations)
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137 size_t word_size() const { return size(); }
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138 size_t used_word_size() const;
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139 size_t free_word_size() const;
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140
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141 #ifdef ASSERT
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142 void mangle();
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143 bool is_tagged_free() { return _is_tagged_free; }
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144 void set_is_tagged_free(bool v) { _is_tagged_free = v; }
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145 #endif
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146
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147 void print_on(outputStream* st) const;
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148 void verify();
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149 };
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150
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151 // Metablock is the unit of allocation from a Chunk.
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152 //
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153 // A Metablock may be reused by its SpaceManager but are never moved between
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154 // SpaceManagers. There is no explicit link to the Metachunk
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155 // from which it was allocated. Metablock may be deallocated and
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156 // put on a freelist but the space is never freed, rather
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157 // the Metachunk it is a part of will be deallocated when it's
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158 // associated class loader is collected.
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159
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160 class Metablock : public Metabase<Metablock> {
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161 friend class VMStructs;
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162 public:
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163 Metablock(size_t word_size) : Metabase<Metablock>(word_size) {}
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164 };
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165
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166 #endif // SHARE_VM_MEMORY_METACHUNK_HPP
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