annotate src/share/vm/memory/blockOffsetTable.hpp @ 1972:f95d63e2154a

6989984: Use standard include model for Hospot Summary: Replaced MakeDeps and the includeDB files with more standardized solutions. Reviewed-by: coleenp, kvn, kamg
author stefank
date Tue, 23 Nov 2010 13:22:55 -0800
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1 /*
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2 * Copyright (c) 2000, 2010, 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
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25 #ifndef SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP
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26 #define SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP
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27
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28 #include "memory/memRegion.hpp"
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29 #include "runtime/virtualspace.hpp"
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30 #include "utilities/globalDefinitions.hpp"
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31
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32 // The CollectedHeap type requires subtypes to implement a method
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33 // "block_start". For some subtypes, notably generational
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34 // systems using card-table-based write barriers, the efficiency of this
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35 // operation may be important. Implementations of the "BlockOffsetArray"
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36 // class may be useful in providing such efficient implementations.
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37 //
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38 // BlockOffsetTable (abstract)
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39 // - BlockOffsetArray (abstract)
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40 // - BlockOffsetArrayNonContigSpace
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41 // - BlockOffsetArrayContigSpace
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42 //
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43
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44 class ContiguousSpace;
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45 class SerializeOopClosure;
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46
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47 //////////////////////////////////////////////////////////////////////////
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48 // The BlockOffsetTable "interface"
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49 //////////////////////////////////////////////////////////////////////////
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50 class BlockOffsetTable VALUE_OBJ_CLASS_SPEC {
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51 friend class VMStructs;
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52 protected:
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53 // These members describe the region covered by the table.
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54
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55 // The space this table is covering.
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56 HeapWord* _bottom; // == reserved.start
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57 HeapWord* _end; // End of currently allocated region.
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58
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59 public:
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60 // Initialize the table to cover the given space.
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61 // The contents of the initial table are undefined.
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62 BlockOffsetTable(HeapWord* bottom, HeapWord* end):
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63 _bottom(bottom), _end(end) {
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64 assert(_bottom <= _end, "arguments out of order");
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65 }
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66
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67 // Note that the committed size of the covered space may have changed,
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68 // so the table size might also wish to change.
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69 virtual void resize(size_t new_word_size) = 0;
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70
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71 virtual void set_bottom(HeapWord* new_bottom) {
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72 assert(new_bottom <= _end, "new_bottom > _end");
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73 _bottom = new_bottom;
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74 resize(pointer_delta(_end, _bottom));
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75 }
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76
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77 // Requires "addr" to be contained by a block, and returns the address of
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78 // the start of that block.
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79 virtual HeapWord* block_start_unsafe(const void* addr) const = 0;
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80
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81 // Returns the address of the start of the block containing "addr", or
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82 // else "null" if it is covered by no block.
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83 HeapWord* block_start(const void* addr) const;
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84 };
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85
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86 //////////////////////////////////////////////////////////////////////////
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87 // One implementation of "BlockOffsetTable," the BlockOffsetArray,
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88 // divides the covered region into "N"-word subregions (where
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89 // "N" = 2^"LogN". An array with an entry for each such subregion
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90 // indicates how far back one must go to find the start of the
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91 // chunk that includes the first word of the subregion.
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92 //
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93 // Each BlockOffsetArray is owned by a Space. However, the actual array
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94 // may be shared by several BlockOffsetArrays; this is useful
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95 // when a single resizable area (such as a generation) is divided up into
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96 // several spaces in which contiguous allocation takes place. (Consider,
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97 // for example, the garbage-first generation.)
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98
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99 // Here is the shared array type.
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100 //////////////////////////////////////////////////////////////////////////
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101 // BlockOffsetSharedArray
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102 //////////////////////////////////////////////////////////////////////////
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103 class BlockOffsetSharedArray: public CHeapObj {
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104 friend class BlockOffsetArray;
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105 friend class BlockOffsetArrayNonContigSpace;
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106 friend class BlockOffsetArrayContigSpace;
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107 friend class VMStructs;
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108
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109 private:
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110 enum SomePrivateConstants {
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111 LogN = 9,
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112 LogN_words = LogN - LogHeapWordSize,
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113 N_bytes = 1 << LogN,
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114 N_words = 1 << LogN_words
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115 };
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116
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117 bool _init_to_zero;
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118
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119 // The reserved region covered by the shared array.
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120 MemRegion _reserved;
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121
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122 // End of the current committed region.
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123 HeapWord* _end;
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124
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125 // Array for keeping offsets for retrieving object start fast given an
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126 // address.
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127 VirtualSpace _vs;
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128 u_char* _offset_array; // byte array keeping backwards offsets
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129
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130 protected:
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131 // Bounds checking accessors:
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132 // For performance these have to devolve to array accesses in product builds.
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133 u_char offset_array(size_t index) const {
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134 assert(index < _vs.committed_size(), "index out of range");
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135 return _offset_array[index];
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136 }
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137 // An assertion-checking helper method for the set_offset_array() methods below.
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138 void check_reducing_assertion(bool reducing);
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139
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140 void set_offset_array(size_t index, u_char offset, bool reducing = false) {
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141 check_reducing_assertion(reducing);
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142 assert(index < _vs.committed_size(), "index out of range");
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143 assert(!reducing || _offset_array[index] >= offset, "Not reducing");
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144 _offset_array[index] = offset;
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145 }
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146
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147 void set_offset_array(size_t index, HeapWord* high, HeapWord* low, bool reducing = false) {
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148 check_reducing_assertion(reducing);
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149 assert(index < _vs.committed_size(), "index out of range");
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150 assert(high >= low, "addresses out of order");
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151 assert(pointer_delta(high, low) <= N_words, "offset too large");
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152 assert(!reducing || _offset_array[index] >= (u_char)pointer_delta(high, low),
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153 "Not reducing");
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154 _offset_array[index] = (u_char)pointer_delta(high, low);
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155 }
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156
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157 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset, bool reducing = false) {
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158 check_reducing_assertion(reducing);
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159 assert(index_for(right - 1) < _vs.committed_size(),
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160 "right address out of range");
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161 assert(left < right, "Heap addresses out of order");
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162 size_t num_cards = pointer_delta(right, left) >> LogN_words;
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163
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164 // Below, we may use an explicit loop instead of memset()
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165 // because on certain platforms memset() can give concurrent
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166 // readers "out-of-thin-air," phantom zeros; see 6948537.
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167 if (UseMemSetInBOT) {
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168 memset(&_offset_array[index_for(left)], offset, num_cards);
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169 } else {
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170 size_t i = index_for(left);
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171 const size_t end = i + num_cards;
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172 for (; i < end; i++) {
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173 // Elided until CR 6977974 is fixed properly.
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174 // assert(!reducing || _offset_array[i] >= offset, "Not reducing");
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175 _offset_array[i] = offset;
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176 }
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177 }
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178 }
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179
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180 void set_offset_array(size_t left, size_t right, u_char offset, bool reducing = false) {
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181 check_reducing_assertion(reducing);
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182 assert(right < _vs.committed_size(), "right address out of range");
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183 assert(left <= right, "indexes out of order");
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184 size_t num_cards = right - left + 1;
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185
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186 // Below, we may use an explicit loop instead of memset
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187 // because on certain platforms memset() can give concurrent
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188 // readers "out-of-thin-air," phantom zeros; see 6948537.
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189 if (UseMemSetInBOT) {
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190 memset(&_offset_array[left], offset, num_cards);
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191 } else {
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192 size_t i = left;
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193 const size_t end = i + num_cards;
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194 for (; i < end; i++) {
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195 // Elided until CR 6977974 is fixed properly.
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196 // assert(!reducing || _offset_array[i] >= offset, "Not reducing");
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197 _offset_array[i] = offset;
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198 }
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199 }
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200 }
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201
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202 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
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203 assert(index < _vs.committed_size(), "index out of range");
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204 assert(high >= low, "addresses out of order");
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205 assert(pointer_delta(high, low) <= N_words, "offset too large");
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206 assert(_offset_array[index] == pointer_delta(high, low),
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207 "Wrong offset");
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208 }
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209
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210 bool is_card_boundary(HeapWord* p) const;
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211
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212 // Return the number of slots needed for an offset array
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213 // that covers mem_region_words words.
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214 // We always add an extra slot because if an object
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215 // ends on a card boundary we put a 0 in the next
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216 // offset array slot, so we want that slot always
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217 // to be reserved.
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218
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219 size_t compute_size(size_t mem_region_words) {
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220 size_t number_of_slots = (mem_region_words / N_words) + 1;
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221 return ReservedSpace::allocation_align_size_up(number_of_slots);
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222 }
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223
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224 public:
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225 // Initialize the table to cover from "base" to (at least)
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226 // "base + init_word_size". In the future, the table may be expanded
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227 // (see "resize" below) up to the size of "_reserved" (which must be at
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228 // least "init_word_size".) The contents of the initial table are
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229 // undefined; it is the responsibility of the constituent
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230 // BlockOffsetTable(s) to initialize cards.
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231 BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size);
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232
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233 // Notes a change in the committed size of the region covered by the
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234 // table. The "new_word_size" may not be larger than the size of the
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235 // reserved region this table covers.
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236 void resize(size_t new_word_size);
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237
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238 void set_bottom(HeapWord* new_bottom);
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239
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240 // Whether entries should be initialized to zero. Used currently only for
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241 // error checking.
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242 void set_init_to_zero(bool val) { _init_to_zero = val; }
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243 bool init_to_zero() { return _init_to_zero; }
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244
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245 // Updates all the BlockOffsetArray's sharing this shared array to
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246 // reflect the current "top"'s of their spaces.
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247 void update_offset_arrays(); // Not yet implemented!
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248
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249 // Return the appropriate index into "_offset_array" for "p".
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250 size_t index_for(const void* p) const;
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251
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252 // Return the address indicating the start of the region corresponding to
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253 // "index" in "_offset_array".
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254 HeapWord* address_for_index(size_t index) const;
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255
301
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256 // Return the address "p" incremented by the size of
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257 // a region. This method does not align the address
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258 // returned to the start of a region. It is a simple
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259 // primitive.
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260 HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; }
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261
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262 // Shared space support
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263 void serialize(SerializeOopClosure* soc, HeapWord* start, HeapWord* end);
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264 };
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265
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266 //////////////////////////////////////////////////////////////////////////
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267 // The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray.
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268 //////////////////////////////////////////////////////////////////////////
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269 class BlockOffsetArray: public BlockOffsetTable {
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270 friend class VMStructs;
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271 friend class G1BlockOffsetArray; // temp. until we restructure and cleanup
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272 protected:
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273 // The following enums are used by do_block_internal() below
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274 enum Action {
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275 Action_single, // BOT records a single block (see single_block())
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276 Action_mark, // BOT marks the start of a block (see mark_block())
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277 Action_check // Check that BOT records block correctly
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278 // (see verify_single_block()).
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279 };
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280
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281 enum SomePrivateConstants {
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282 N_words = BlockOffsetSharedArray::N_words,
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283 LogN = BlockOffsetSharedArray::LogN,
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284 // entries "e" of at least N_words mean "go back by Base^(e-N_words)."
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285 // All entries are less than "N_words + N_powers".
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286 LogBase = 4,
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287 Base = (1 << LogBase),
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288 N_powers = 14
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289 };
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290
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291 static size_t power_to_cards_back(uint i) {
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292 return (size_t)(1 << (LogBase * i));
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293 }
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294 static size_t power_to_words_back(uint i) {
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295 return power_to_cards_back(i) * N_words;
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296 }
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297 static size_t entry_to_cards_back(u_char entry) {
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298 assert(entry >= N_words, "Precondition");
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299 return power_to_cards_back(entry - N_words);
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300 }
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301 static size_t entry_to_words_back(u_char entry) {
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302 assert(entry >= N_words, "Precondition");
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303 return power_to_words_back(entry - N_words);
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304 }
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305
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306 // The shared array, which is shared with other BlockOffsetArray's
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307 // corresponding to different spaces within a generation or span of
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308 // memory.
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309 BlockOffsetSharedArray* _array;
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310
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311 // The space that owns this subregion.
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312 Space* _sp;
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313
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314 // If true, array entries are initialized to 0; otherwise, they are
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315 // initialized to point backwards to the beginning of the covered region.
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316 bool _init_to_zero;
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317
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318 // An assertion-checking helper method for the set_remainder*() methods below.
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319 void check_reducing_assertion(bool reducing) { _array->check_reducing_assertion(reducing); }
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320
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321 // Sets the entries
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322 // corresponding to the cards starting at "start" and ending at "end"
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323 // to point back to the card before "start": the interval [start, end)
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324 // is right-open. The last parameter, reducing, indicates whether the
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325 // updates to individual entries always reduce the entry from a higher
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326 // to a lower value. (For example this would hold true during a temporal
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327 // regime during which only block splits were updating the BOT.
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328 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing = false);
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329 // Same as above, except that the args here are a card _index_ interval
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330 // that is closed: [start_index, end_index]
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331 void set_remainder_to_point_to_start_incl(size_t start, size_t end, bool reducing = false);
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332
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333 // A helper function for BOT adjustment/verification work
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334 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing = false);
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335
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336 public:
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337 // The space may not have its bottom and top set yet, which is why the
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338 // region is passed as a parameter. If "init_to_zero" is true, the
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339 // elements of the array are initialized to zero. Otherwise, they are
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340 // initialized to point backwards to the beginning.
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341 BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr,
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342 bool init_to_zero_);
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343
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344 // Note: this ought to be part of the constructor, but that would require
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345 // "this" to be passed as a parameter to a member constructor for
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346 // the containing concrete subtype of Space.
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347 // This would be legal C++, but MS VC++ doesn't allow it.
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348 void set_space(Space* sp) { _sp = sp; }
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349
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350 // Resets the covered region to the given "mr".
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351 void set_region(MemRegion mr) {
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352 _bottom = mr.start();
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353 _end = mr.end();
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354 }
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355
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356 // Note that the committed size of the covered space may have changed,
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357 // so the table size might also wish to change.
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358 virtual void resize(size_t new_word_size) {
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359 HeapWord* new_end = _bottom + new_word_size;
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360 if (_end < new_end && !init_to_zero()) {
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361 // verify that the old and new boundaries are also card boundaries
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362 assert(_array->is_card_boundary(_end),
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363 "_end not a card boundary");
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364 assert(_array->is_card_boundary(new_end),
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365 "new _end would not be a card boundary");
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366 // set all the newly added cards
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367 _array->set_offset_array(_end, new_end, N_words);
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368 }
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369 _end = new_end; // update _end
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370 }
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371
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372 // Adjust the BOT to show that it has a single block in the
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373 // range [blk_start, blk_start + size). All necessary BOT
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374 // cards are adjusted, but _unallocated_block isn't.
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375 void single_block(HeapWord* blk_start, HeapWord* blk_end);
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376 void single_block(HeapWord* blk, size_t size) {
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377 single_block(blk, blk + size);
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378 }
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379
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380 // When the alloc_block() call returns, the block offset table should
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381 // have enough information such that any subsequent block_start() call
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382 // with an argument equal to an address that is within the range
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383 // [blk_start, blk_end) would return the value blk_start, provided
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384 // there have been no calls in between that reset this information
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385 // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call
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386 // for an appropriate range covering the said interval).
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387 // These methods expect to be called with [blk_start, blk_end)
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388 // representing a block of memory in the heap.
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389 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
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390 void alloc_block(HeapWord* blk, size_t size) {
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391 alloc_block(blk, blk + size);
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392 }
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393
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394 // If true, initialize array slots with no allocated blocks to zero.
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395 // Otherwise, make them point back to the front.
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396 bool init_to_zero() { return _init_to_zero; }
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397 // Corresponding setter
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398 void set_init_to_zero(bool val) {
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399 _init_to_zero = val;
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400 assert(_array != NULL, "_array should be non-NULL");
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401 _array->set_init_to_zero(val);
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402 }
0
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403
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404 // Debugging
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405 // Return the index of the last entry in the "active" region.
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406 virtual size_t last_active_index() const = 0;
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407 // Verify the block offset table
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408 void verify() const;
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409 void check_all_cards(size_t left_card, size_t right_card) const;
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410 };
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411
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412 ////////////////////////////////////////////////////////////////////////////
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413 // A subtype of BlockOffsetArray that takes advantage of the fact
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414 // that its underlying space is a NonContiguousSpace, so that some
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415 // specialized interfaces can be made available for spaces that
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416 // manipulate the table.
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417 ////////////////////////////////////////////////////////////////////////////
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418 class BlockOffsetArrayNonContigSpace: public BlockOffsetArray {
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419 friend class VMStructs;
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420 private:
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421 // The portion [_unallocated_block, _sp.end()) of the space that
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422 // is a single block known not to contain any objects.
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423 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
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424 HeapWord* _unallocated_block;
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425
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426 public:
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427 BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
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428 BlockOffsetArray(array, mr, false),
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429 _unallocated_block(_bottom) { }
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430
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431 // accessor
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432 HeapWord* unallocated_block() const {
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433 assert(BlockOffsetArrayUseUnallocatedBlock,
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434 "_unallocated_block is not being maintained");
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435 return _unallocated_block;
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436 }
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437
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438 void set_unallocated_block(HeapWord* block) {
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439 assert(BlockOffsetArrayUseUnallocatedBlock,
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440 "_unallocated_block is not being maintained");
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441 assert(block >= _bottom && block <= _end, "out of range");
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442 _unallocated_block = block;
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443 }
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444
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445 // These methods expect to be called with [blk_start, blk_end)
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446 // representing a block of memory in the heap.
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447 void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
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448 void alloc_block(HeapWord* blk, size_t size) {
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449 alloc_block(blk, blk + size);
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450 }
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451
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452 // The following methods are useful and optimized for a
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453 // non-contiguous space.
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454
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455 // Given a block [blk_start, blk_start + full_blk_size), and
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456 // a left_blk_size < full_blk_size, adjust the BOT to show two
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457 // blocks [blk_start, blk_start + left_blk_size) and
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458 // [blk_start + left_blk_size, blk_start + full_blk_size).
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459 // It is assumed (and verified in the non-product VM) that the
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460 // BOT was correct for the original block.
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461 void split_block(HeapWord* blk_start, size_t full_blk_size,
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462 size_t left_blk_size);
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463
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464 // Adjust BOT to show that it has a block in the range
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465 // [blk_start, blk_start + size). Only the first card
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466 // of BOT is touched. It is assumed (and verified in the
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467 // non-product VM) that the remaining cards of the block
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468 // are correct.
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469 void mark_block(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false);
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470 void mark_block(HeapWord* blk, size_t size, bool reducing = false) {
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471 mark_block(blk, blk + size, reducing);
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472 }
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473
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474 // Adjust _unallocated_block to indicate that a particular
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475 // block has been newly allocated or freed. It is assumed (and
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476 // verified in the non-product VM) that the BOT is correct for
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477 // the given block.
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478 void allocated(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false) {
0
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479 // Verify that the BOT shows [blk, blk + blk_size) to be one block.
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480 verify_single_block(blk_start, blk_end);
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481 if (BlockOffsetArrayUseUnallocatedBlock) {
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482 _unallocated_block = MAX2(_unallocated_block, blk_end);
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483 }
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484 }
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485
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486 void allocated(HeapWord* blk, size_t size, bool reducing = false) {
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487 allocated(blk, blk + size, reducing);
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488 }
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489
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490 void freed(HeapWord* blk_start, HeapWord* blk_end);
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491 void freed(HeapWord* blk, size_t size);
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492
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493 HeapWord* block_start_unsafe(const void* addr) const;
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494
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495 // Requires "addr" to be the start of a card and returns the
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496 // start of the block that contains the given address.
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497 HeapWord* block_start_careful(const void* addr) const;
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498
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499 // Verification & debugging: ensure that the offset table reflects
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500 // the fact that the block [blk_start, blk_end) or [blk, blk + size)
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501 // is a single block of storage. NOTE: can't const this because of
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502 // call to non-const do_block_internal() below.
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503 void verify_single_block(HeapWord* blk_start, HeapWord* blk_end)
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504 PRODUCT_RETURN;
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505 void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN;
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506
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507 // Verify that the given block is before _unallocated_block
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508 void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end)
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509 const PRODUCT_RETURN;
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510 void verify_not_unallocated(HeapWord* blk, size_t size)
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511 const PRODUCT_RETURN;
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512
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513 // Debugging support
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514 virtual size_t last_active_index() const;
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515 };
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516
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517 ////////////////////////////////////////////////////////////////////////////
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518 // A subtype of BlockOffsetArray that takes advantage of the fact
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519 // that its underlying space is a ContiguousSpace, so that its "active"
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520 // region can be more efficiently tracked (than for a non-contiguous space).
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521 ////////////////////////////////////////////////////////////////////////////
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522 class BlockOffsetArrayContigSpace: public BlockOffsetArray {
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523 friend class VMStructs;
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524 private:
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525 // allocation boundary at which offset array must be updated
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526 HeapWord* _next_offset_threshold;
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527 size_t _next_offset_index; // index corresponding to that boundary
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528
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529 // Work function when allocation start crosses threshold.
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530 void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end);
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531
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532 public:
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533 BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
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534 BlockOffsetArray(array, mr, true) {
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535 _next_offset_threshold = NULL;
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536 _next_offset_index = 0;
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537 }
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538
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539 void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); }
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540
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541 // Initialize the threshold for an empty heap.
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542 HeapWord* initialize_threshold();
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543 // Zero out the entry for _bottom (offset will be zero)
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544 void zero_bottom_entry();
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545
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546 // Return the next threshold, the point at which the table should be
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547 // updated.
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548 HeapWord* threshold() const { return _next_offset_threshold; }
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549
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550 // In general, these methods expect to be called with
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551 // [blk_start, blk_end) representing a block of memory in the heap.
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552 // In this implementation, however, we are OK even if blk_start and/or
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553 // blk_end are NULL because NULL is represented as 0, and thus
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554 // never exceeds the "_next_offset_threshold".
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555 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
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556 if (blk_end > _next_offset_threshold) {
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557 alloc_block_work(blk_start, blk_end);
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558 }
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559 }
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560 void alloc_block(HeapWord* blk, size_t size) {
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561 alloc_block(blk, blk + size);
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562 }
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563
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564 HeapWord* block_start_unsafe(const void* addr) const;
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565
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566 void serialize(SerializeOopClosure* soc);
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567
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568 // Debugging support
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569 virtual size_t last_active_index() const;
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570 };
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571
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572 #endif // SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP