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1 /* |
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2 * Copyright 2000-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
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20 * CA 95054 USA or visit www.sun.com if you need additional information or |
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21 * have any questions. |
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22 * |
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23 */ |
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24 |
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25 // The CollectedHeap type requires subtypes to implement a method |
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26 // "block_start". For some subtypes, notably generational |
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27 // systems using card-table-based write barriers, the efficiency of this |
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28 // operation may be important. Implementations of the "BlockOffsetArray" |
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29 // class may be useful in providing such efficient implementations. |
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30 // |
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31 // BlockOffsetTable (abstract) |
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32 // - BlockOffsetArray (abstract) |
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33 // - BlockOffsetArrayNonContigSpace |
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34 // - BlockOffsetArrayContigSpace |
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35 // |
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36 |
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37 class ContiguousSpace; |
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38 class SerializeOopClosure; |
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39 |
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40 ////////////////////////////////////////////////////////////////////////// |
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41 // The BlockOffsetTable "interface" |
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42 ////////////////////////////////////////////////////////////////////////// |
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43 class BlockOffsetTable VALUE_OBJ_CLASS_SPEC { |
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44 friend class VMStructs; |
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45 protected: |
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46 // These members describe the region covered by the table. |
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47 |
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48 // The space this table is covering. |
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49 HeapWord* _bottom; // == reserved.start |
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50 HeapWord* _end; // End of currently allocated region. |
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51 |
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52 public: |
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53 // Initialize the table to cover the given space. |
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54 // The contents of the initial table are undefined. |
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55 BlockOffsetTable(HeapWord* bottom, HeapWord* end): |
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56 _bottom(bottom), _end(end) { |
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57 assert(_bottom <= _end, "arguments out of order"); |
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58 } |
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59 |
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60 // Note that the committed size of the covered space may have changed, |
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61 // so the table size might also wish to change. |
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62 virtual void resize(size_t new_word_size) = 0; |
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63 |
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64 virtual void set_bottom(HeapWord* new_bottom) { |
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65 assert(new_bottom <= _end, "new_bottom > _end"); |
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66 _bottom = new_bottom; |
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67 resize(pointer_delta(_end, _bottom)); |
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68 } |
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69 |
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70 // Requires "addr" to be contained by a block, and returns the address of |
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71 // the start of that block. |
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72 virtual HeapWord* block_start_unsafe(const void* addr) const = 0; |
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73 |
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74 // Returns the address of the start of the block containing "addr", or |
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75 // else "null" if it is covered by no block. |
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76 HeapWord* block_start(const void* addr) const; |
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77 }; |
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78 |
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79 ////////////////////////////////////////////////////////////////////////// |
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80 // One implementation of "BlockOffsetTable," the BlockOffsetArray, |
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81 // divides the covered region into "N"-word subregions (where |
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82 // "N" = 2^"LogN". An array with an entry for each such subregion |
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83 // indicates how far back one must go to find the start of the |
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84 // chunk that includes the first word of the subregion. |
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85 // |
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86 // Each BlockOffsetArray is owned by a Space. However, the actual array |
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87 // may be shared by several BlockOffsetArrays; this is useful |
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88 // when a single resizable area (such as a generation) is divided up into |
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89 // several spaces in which contiguous allocation takes place. (Consider, |
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90 // for example, the garbage-first generation.) |
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91 |
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92 // Here is the shared array type. |
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93 ////////////////////////////////////////////////////////////////////////// |
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94 // BlockOffsetSharedArray |
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95 ////////////////////////////////////////////////////////////////////////// |
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96 class BlockOffsetSharedArray: public CHeapObj { |
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97 friend class BlockOffsetArray; |
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98 friend class BlockOffsetArrayNonContigSpace; |
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99 friend class BlockOffsetArrayContigSpace; |
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100 friend class VMStructs; |
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101 |
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102 private: |
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103 enum SomePrivateConstants { |
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104 LogN = 9, |
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105 LogN_words = LogN - LogHeapWordSize, |
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106 N_bytes = 1 << LogN, |
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107 N_words = 1 << LogN_words |
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108 }; |
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109 |
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110 // The reserved region covered by the shared array. |
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111 MemRegion _reserved; |
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112 |
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113 // End of the current committed region. |
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114 HeapWord* _end; |
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115 |
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116 // Array for keeping offsets for retrieving object start fast given an |
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117 // address. |
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118 VirtualSpace _vs; |
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119 u_char* _offset_array; // byte array keeping backwards offsets |
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120 |
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121 protected: |
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122 // Bounds checking accessors: |
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123 // For performance these have to devolve to array accesses in product builds. |
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124 u_char offset_array(size_t index) const { |
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125 assert(index < _vs.committed_size(), "index out of range"); |
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126 return _offset_array[index]; |
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127 } |
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128 void set_offset_array(size_t index, u_char offset) { |
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129 assert(index < _vs.committed_size(), "index out of range"); |
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130 _offset_array[index] = offset; |
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131 } |
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132 void set_offset_array(size_t index, HeapWord* high, HeapWord* low) { |
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133 assert(index < _vs.committed_size(), "index out of range"); |
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134 assert(high >= low, "addresses out of order"); |
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135 assert(pointer_delta(high, low) <= N_words, "offset too large"); |
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136 _offset_array[index] = (u_char)pointer_delta(high, low); |
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137 } |
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138 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) { |
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139 assert(index_for(right - 1) < _vs.committed_size(), |
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140 "right address out of range"); |
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141 assert(left < right, "Heap addresses out of order"); |
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142 size_t num_cards = pointer_delta(right, left) >> LogN_words; |
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143 memset(&_offset_array[index_for(left)], offset, num_cards); |
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144 } |
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145 |
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146 void set_offset_array(size_t left, size_t right, u_char offset) { |
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147 assert(right < _vs.committed_size(), "right address out of range"); |
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148 assert(left <= right, "indexes out of order"); |
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149 size_t num_cards = right - left + 1; |
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150 memset(&_offset_array[left], offset, num_cards); |
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151 } |
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152 |
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153 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { |
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154 assert(index < _vs.committed_size(), "index out of range"); |
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155 assert(high >= low, "addresses out of order"); |
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156 assert(pointer_delta(high, low) <= N_words, "offset too large"); |
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157 assert(_offset_array[index] == pointer_delta(high, low), |
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158 "Wrong offset"); |
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159 } |
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160 |
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161 bool is_card_boundary(HeapWord* p) const; |
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162 |
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163 // Return the number of slots needed for an offset array |
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164 // that covers mem_region_words words. |
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165 // We always add an extra slot because if an object |
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166 // ends on a card boundary we put a 0 in the next |
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167 // offset array slot, so we want that slot always |
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168 // to be reserved. |
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169 |
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170 size_t compute_size(size_t mem_region_words) { |
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171 size_t number_of_slots = (mem_region_words / N_words) + 1; |
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172 return ReservedSpace::allocation_align_size_up(number_of_slots); |
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173 } |
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174 |
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175 public: |
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176 // Initialize the table to cover from "base" to (at least) |
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177 // "base + init_word_size". In the future, the table may be expanded |
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178 // (see "resize" below) up to the size of "_reserved" (which must be at |
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179 // least "init_word_size".) The contents of the initial table are |
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180 // undefined; it is the responsibility of the constituent |
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181 // BlockOffsetTable(s) to initialize cards. |
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182 BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); |
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183 |
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184 // Notes a change in the committed size of the region covered by the |
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185 // table. The "new_word_size" may not be larger than the size of the |
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186 // reserved region this table covers. |
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187 void resize(size_t new_word_size); |
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188 |
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189 void set_bottom(HeapWord* new_bottom); |
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190 |
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191 // Updates all the BlockOffsetArray's sharing this shared array to |
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192 // reflect the current "top"'s of their spaces. |
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193 void update_offset_arrays(); // Not yet implemented! |
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194 |
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195 // Return the appropriate index into "_offset_array" for "p". |
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196 size_t index_for(const void* p) const; |
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197 |
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198 // Return the address indicating the start of the region corresponding to |
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199 // "index" in "_offset_array". |
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200 HeapWord* address_for_index(size_t index) const; |
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201 |
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202 // Shared space support |
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203 void serialize(SerializeOopClosure* soc, HeapWord* start, HeapWord* end); |
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204 }; |
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205 |
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206 ////////////////////////////////////////////////////////////////////////// |
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207 // The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray. |
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208 ////////////////////////////////////////////////////////////////////////// |
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209 class BlockOffsetArray: public BlockOffsetTable { |
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210 friend class VMStructs; |
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211 protected: |
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212 // The following enums are used by do_block_internal() below |
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213 enum Action { |
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214 Action_single, // BOT records a single block (see single_block()) |
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215 Action_mark, // BOT marks the start of a block (see mark_block()) |
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216 Action_check // Check that BOT records block correctly |
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217 // (see verify_single_block()). |
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218 }; |
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219 |
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220 enum SomePrivateConstants { |
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221 N_words = BlockOffsetSharedArray::N_words, |
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222 LogN = BlockOffsetSharedArray::LogN, |
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223 // entries "e" of at least N_words mean "go back by Base^(e-N_words)." |
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224 // All entries are less than "N_words + N_powers". |
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225 LogBase = 4, |
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226 Base = (1 << LogBase), |
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227 N_powers = 14 |
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228 }; |
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229 |
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230 static size_t power_to_cards_back(uint i) { |
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231 return 1 << (LogBase * i); |
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232 } |
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233 static size_t power_to_words_back(uint i) { |
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234 return power_to_cards_back(i) * N_words; |
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235 } |
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236 static size_t entry_to_cards_back(u_char entry) { |
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237 assert(entry >= N_words, "Precondition"); |
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238 return power_to_cards_back(entry - N_words); |
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239 } |
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240 static size_t entry_to_words_back(u_char entry) { |
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241 assert(entry >= N_words, "Precondition"); |
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242 return power_to_words_back(entry - N_words); |
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243 } |
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244 |
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245 // The shared array, which is shared with other BlockOffsetArray's |
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246 // corresponding to different spaces within a generation or span of |
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247 // memory. |
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248 BlockOffsetSharedArray* _array; |
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249 |
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250 // The space that owns this subregion. |
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251 Space* _sp; |
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252 |
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253 // If true, array entries are initialized to 0; otherwise, they are |
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254 // initialized to point backwards to the beginning of the covered region. |
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255 bool _init_to_zero; |
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256 |
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257 // Sets the entries |
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258 // corresponding to the cards starting at "start" and ending at "end" |
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259 // to point back to the card before "start": the interval [start, end) |
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260 // is right-open. |
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261 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end); |
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262 // Same as above, except that the args here are a card _index_ interval |
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263 // that is closed: [start_index, end_index] |
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264 void set_remainder_to_point_to_start_incl(size_t start, size_t end); |
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265 |
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266 // A helper function for BOT adjustment/verification work |
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267 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action); |
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268 |
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269 public: |
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270 // The space may not have its bottom and top set yet, which is why the |
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271 // region is passed as a parameter. If "init_to_zero" is true, the |
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272 // elements of the array are initialized to zero. Otherwise, they are |
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273 // initialized to point backwards to the beginning. |
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274 BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr, |
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275 bool init_to_zero); |
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276 |
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277 // Note: this ought to be part of the constructor, but that would require |
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278 // "this" to be passed as a parameter to a member constructor for |
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279 // the containing concrete subtype of Space. |
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280 // This would be legal C++, but MS VC++ doesn't allow it. |
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281 void set_space(Space* sp) { _sp = sp; } |
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282 |
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283 // Resets the covered region to the given "mr". |
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284 void set_region(MemRegion mr) { |
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285 _bottom = mr.start(); |
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286 _end = mr.end(); |
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287 } |
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288 |
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289 // Note that the committed size of the covered space may have changed, |
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290 // so the table size might also wish to change. |
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291 virtual void resize(size_t new_word_size) { |
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292 HeapWord* new_end = _bottom + new_word_size; |
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293 if (_end < new_end && !init_to_zero()) { |
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294 // verify that the old and new boundaries are also card boundaries |
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295 assert(_array->is_card_boundary(_end), |
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296 "_end not a card boundary"); |
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297 assert(_array->is_card_boundary(new_end), |
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298 "new _end would not be a card boundary"); |
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299 // set all the newly added cards |
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300 _array->set_offset_array(_end, new_end, N_words); |
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301 } |
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302 _end = new_end; // update _end |
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303 } |
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304 |
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305 // Adjust the BOT to show that it has a single block in the |
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306 // range [blk_start, blk_start + size). All necessary BOT |
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307 // cards are adjusted, but _unallocated_block isn't. |
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308 void single_block(HeapWord* blk_start, HeapWord* blk_end); |
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309 void single_block(HeapWord* blk, size_t size) { |
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310 single_block(blk, blk + size); |
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311 } |
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312 |
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313 // When the alloc_block() call returns, the block offset table should |
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314 // have enough information such that any subsequent block_start() call |
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315 // with an argument equal to an address that is within the range |
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316 // [blk_start, blk_end) would return the value blk_start, provided |
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317 // there have been no calls in between that reset this information |
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318 // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call |
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319 // for an appropriate range covering the said interval). |
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320 // These methods expect to be called with [blk_start, blk_end) |
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321 // representing a block of memory in the heap. |
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322 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); |
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323 void alloc_block(HeapWord* blk, size_t size) { |
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324 alloc_block(blk, blk + size); |
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325 } |
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326 |
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327 // If true, initialize array slots with no allocated blocks to zero. |
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328 // Otherwise, make them point back to the front. |
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329 bool init_to_zero() { return _init_to_zero; } |
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330 |
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331 // Debugging |
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332 // Return the index of the last entry in the "active" region. |
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333 virtual size_t last_active_index() const = 0; |
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334 // Verify the block offset table |
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335 void verify() const; |
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336 void check_all_cards(size_t left_card, size_t right_card) const; |
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337 }; |
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338 |
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339 //////////////////////////////////////////////////////////////////////////// |
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340 // A subtype of BlockOffsetArray that takes advantage of the fact |
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341 // that its underlying space is a NonContiguousSpace, so that some |
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342 // specialized interfaces can be made available for spaces that |
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343 // manipulate the table. |
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344 //////////////////////////////////////////////////////////////////////////// |
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345 class BlockOffsetArrayNonContigSpace: public BlockOffsetArray { |
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346 friend class VMStructs; |
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347 private: |
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348 // The portion [_unallocated_block, _sp.end()) of the space that |
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349 // is a single block known not to contain any objects. |
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350 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. |
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351 HeapWord* _unallocated_block; |
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352 |
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353 public: |
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354 BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr): |
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355 BlockOffsetArray(array, mr, false), |
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356 _unallocated_block(_bottom) { } |
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357 |
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358 // accessor |
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359 HeapWord* unallocated_block() const { |
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360 assert(BlockOffsetArrayUseUnallocatedBlock, |
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361 "_unallocated_block is not being maintained"); |
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362 return _unallocated_block; |
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363 } |
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364 |
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365 void set_unallocated_block(HeapWord* block) { |
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366 assert(BlockOffsetArrayUseUnallocatedBlock, |
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367 "_unallocated_block is not being maintained"); |
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368 assert(block >= _bottom && block <= _end, "out of range"); |
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369 _unallocated_block = block; |
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370 } |
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371 |
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372 // These methods expect to be called with [blk_start, blk_end) |
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373 // representing a block of memory in the heap. |
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374 void alloc_block(HeapWord* blk_start, HeapWord* blk_end); |
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375 void alloc_block(HeapWord* blk, size_t size) { |
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376 alloc_block(blk, blk + size); |
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377 } |
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378 |
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379 // The following methods are useful and optimized for a |
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380 // non-contiguous space. |
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381 |
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382 // Given a block [blk_start, blk_start + full_blk_size), and |
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383 // a left_blk_size < full_blk_size, adjust the BOT to show two |
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384 // blocks [blk_start, blk_start + left_blk_size) and |
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385 // [blk_start + left_blk_size, blk_start + full_blk_size). |
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386 // It is assumed (and verified in the non-product VM) that the |
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387 // BOT was correct for the original block. |
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388 void split_block(HeapWord* blk_start, size_t full_blk_size, |
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389 size_t left_blk_size); |
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390 |
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391 // Adjust BOT to show that it has a block in the range |
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392 // [blk_start, blk_start + size). Only the first card |
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393 // of BOT is touched. It is assumed (and verified in the |
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394 // non-product VM) that the remaining cards of the block |
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395 // are correct. |
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396 void mark_block(HeapWord* blk_start, HeapWord* blk_end); |
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397 void mark_block(HeapWord* blk, size_t size) { |
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398 mark_block(blk, blk + size); |
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399 } |
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400 |
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401 // Adjust _unallocated_block to indicate that a particular |
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402 // block has been newly allocated or freed. It is assumed (and |
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403 // verified in the non-product VM) that the BOT is correct for |
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404 // the given block. |
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405 void allocated(HeapWord* blk_start, HeapWord* blk_end) { |
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406 // Verify that the BOT shows [blk, blk + blk_size) to be one block. |
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407 verify_single_block(blk_start, blk_end); |
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408 if (BlockOffsetArrayUseUnallocatedBlock) { |
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409 _unallocated_block = MAX2(_unallocated_block, blk_end); |
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410 } |
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411 } |
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412 |
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413 void allocated(HeapWord* blk, size_t size) { |
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414 allocated(blk, blk + size); |
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415 } |
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416 |
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417 void freed(HeapWord* blk_start, HeapWord* blk_end); |
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418 void freed(HeapWord* blk, size_t size) { |
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419 freed(blk, blk + size); |
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420 } |
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421 |
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422 HeapWord* block_start_unsafe(const void* addr) const; |
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423 |
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424 // Requires "addr" to be the start of a card and returns the |
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425 // start of the block that contains the given address. |
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426 HeapWord* block_start_careful(const void* addr) const; |
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427 |
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428 |
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429 // Verification & debugging: ensure that the offset table reflects |
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430 // the fact that the block [blk_start, blk_end) or [blk, blk + size) |
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431 // is a single block of storage. NOTE: can't const this because of |
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432 // call to non-const do_block_internal() below. |
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433 void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) |
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434 PRODUCT_RETURN; |
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435 void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN; |
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436 |
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437 // Verify that the given block is before _unallocated_block |
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438 void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end) |
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439 const PRODUCT_RETURN; |
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440 void verify_not_unallocated(HeapWord* blk, size_t size) |
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441 const PRODUCT_RETURN; |
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442 |
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443 // Debugging support |
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444 virtual size_t last_active_index() const; |
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445 }; |
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446 |
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447 //////////////////////////////////////////////////////////////////////////// |
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448 // A subtype of BlockOffsetArray that takes advantage of the fact |
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449 // that its underlying space is a ContiguousSpace, so that its "active" |
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450 // region can be more efficiently tracked (than for a non-contiguous space). |
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451 //////////////////////////////////////////////////////////////////////////// |
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452 class BlockOffsetArrayContigSpace: public BlockOffsetArray { |
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453 friend class VMStructs; |
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454 private: |
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455 // allocation boundary at which offset array must be updated |
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456 HeapWord* _next_offset_threshold; |
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457 size_t _next_offset_index; // index corresponding to that boundary |
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458 |
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459 // Work function when allocation start crosses threshold. |
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460 void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end); |
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461 |
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462 public: |
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463 BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr): |
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464 BlockOffsetArray(array, mr, true) { |
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465 _next_offset_threshold = NULL; |
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466 _next_offset_index = 0; |
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467 } |
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468 |
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469 void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); } |
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470 |
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471 // Initialize the threshold for an empty heap. |
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472 HeapWord* initialize_threshold(); |
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473 // Zero out the entry for _bottom (offset will be zero) |
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474 void zero_bottom_entry(); |
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475 |
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476 // Return the next threshold, the point at which the table should be |
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477 // updated. |
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478 HeapWord* threshold() const { return _next_offset_threshold; } |
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479 |
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480 // In general, these methods expect to be called with |
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481 // [blk_start, blk_end) representing a block of memory in the heap. |
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482 // In this implementation, however, we are OK even if blk_start and/or |
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483 // blk_end are NULL because NULL is represented as 0, and thus |
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484 // never exceeds the "_next_offset_threshold". |
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485 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { |
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486 if (blk_end > _next_offset_threshold) { |
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487 alloc_block_work(blk_start, blk_end); |
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488 } |
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489 } |
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490 void alloc_block(HeapWord* blk, size_t size) { |
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491 alloc_block(blk, blk + size); |
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492 } |
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493 |
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494 HeapWord* block_start_unsafe(const void* addr) const; |
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495 |
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496 void serialize(SerializeOopClosure* soc); |
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497 |
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498 // Debugging support |
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499 virtual size_t last_active_index() const; |
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500 }; |