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1 /*
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2 * Copyright 2001-2006 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 // Forward decl.
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26
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27 class PLABStats;
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28
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29 // A per-thread allocation buffer used during GC.
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30 class ParGCAllocBuffer: public CHeapObj {
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31 protected:
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32 char head[32];
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33 size_t _word_sz; // in HeapWord units
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34 HeapWord* _bottom;
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35 HeapWord* _top;
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36 HeapWord* _end; // last allocatable address + 1
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37 HeapWord* _hard_end; // _end + AlignmentReserve
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38 bool _retained; // whether we hold a _retained_filler
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39 MemRegion _retained_filler;
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40 // In support of ergonomic sizing of PLAB's
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41 size_t _allocated; // in HeapWord units
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42 size_t _wasted; // in HeapWord units
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43 char tail[32];
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44 static const size_t FillerHeaderSize;
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45 static const size_t AlignmentReserve;
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46
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47 public:
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48 // Initializes the buffer to be empty, but with the given "word_sz".
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49 // Must get initialized with "set_buf" for an allocation to succeed.
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50 ParGCAllocBuffer(size_t word_sz);
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51
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52 static const size_t min_size() {
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53 return ThreadLocalAllocBuffer::min_size();
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54 }
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55
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56 static const size_t max_size() {
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57 return ThreadLocalAllocBuffer::max_size();
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58 }
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59
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60 // If an allocation of the given "word_sz" can be satisfied within the
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61 // buffer, do the allocation, returning a pointer to the start of the
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62 // allocated block. If the allocation request cannot be satisfied,
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63 // return NULL.
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64 HeapWord* allocate(size_t word_sz) {
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65 HeapWord* res = _top;
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66 HeapWord* new_top = _top + word_sz;
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67 if (new_top <= _end) {
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68 _top = new_top;
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69 return res;
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70 } else {
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71 return NULL;
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72 }
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73 }
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74
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75 // Undo the last allocation in the buffer, which is required to be of the
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76 // "obj" of the given "word_sz".
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77 void undo_allocation(HeapWord* obj, size_t word_sz) {
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78 assert(_top - word_sz >= _bottom
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79 && _top - word_sz == obj,
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80 "Bad undo_allocation");
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81 _top = _top - word_sz;
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82 }
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83
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84 // The total (word) size of the buffer, including both allocated and
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85 // unallocted space.
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86 size_t word_sz() { return _word_sz; }
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87
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88 // Should only be done if we are about to reset with a new buffer of the
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89 // given size.
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90 void set_word_size(size_t new_word_sz) {
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91 assert(new_word_sz > AlignmentReserve, "Too small");
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92 _word_sz = new_word_sz;
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93 }
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94
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95 // The number of words of unallocated space remaining in the buffer.
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96 size_t words_remaining() {
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97 assert(_end >= _top, "Negative buffer");
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98 return pointer_delta(_end, _top, HeapWordSize);
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99 }
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100
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101 bool contains(void* addr) {
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102 return (void*)_bottom <= addr && addr < (void*)_hard_end;
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103 }
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104
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105 // Sets the space of the buffer to be [buf, space+word_sz()).
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106 void set_buf(HeapWord* buf) {
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107 _bottom = buf;
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108 _top = _bottom;
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109 _hard_end = _bottom + word_sz();
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110 _end = _hard_end - AlignmentReserve;
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111 assert(_end >= _top, "Negative buffer");
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112 // In support of ergonomic sizing
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113 _allocated += word_sz();
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114 }
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115
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116 // Flush the stats supporting ergonomic sizing of PLAB's
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117 void flush_stats(PLABStats* stats);
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118 void flush_stats_and_retire(PLABStats* stats, bool retain) {
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119 // We flush the stats first in order to get a reading of
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120 // unused space in the last buffer.
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121 if (ResizePLAB) {
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122 flush_stats(stats);
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123 }
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124 // Retire the last allocation buffer.
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125 retire(true, retain);
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126 }
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127
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128 // Force future allocations to fail and queries for contains()
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129 // to return false
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130 void invalidate() {
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131 assert(!_retained, "Shouldn't retain an invalidated buffer.");
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132 _end = _hard_end;
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133 _wasted += pointer_delta(_end, _top); // unused space
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134 _top = _end; // force future allocations to fail
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135 _bottom = _end; // force future contains() queries to return false
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136 }
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137
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138 // Fills in the unallocated portion of the buffer with a garbage object.
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139 // If "end_of_gc" is TRUE, is after the last use in the GC. IF "retain"
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140 // is true, attempt to re-use the unused portion in the next GC.
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141 void retire(bool end_of_gc, bool retain);
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142
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143 void print() PRODUCT_RETURN;
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144 };
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145
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146 // PLAB stats book-keeping
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147 class PLABStats VALUE_OBJ_CLASS_SPEC {
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148 size_t _allocated; // total allocated
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149 size_t _wasted; // of which wasted (internal fragmentation)
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150 size_t _unused; // Unused in last buffer
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151 size_t _used; // derived = allocated - wasted - unused
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152 size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized
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153 AdaptiveWeightedAverage
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154 _filter; // integrator with decay
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155
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156 public:
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157 PLABStats(size_t desired_plab_sz_, unsigned wt) :
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158 _allocated(0),
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159 _wasted(0),
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160 _unused(0),
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161 _used(0),
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162 _desired_plab_sz(desired_plab_sz_),
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163 _filter(wt)
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164 {
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165 size_t min_sz = min_size();
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166 size_t max_sz = max_size();
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167 size_t aligned_min_sz = align_object_size(min_sz);
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168 size_t aligned_max_sz = align_object_size(max_sz);
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169 assert(min_sz <= aligned_min_sz && max_sz >= aligned_max_sz &&
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170 min_sz <= max_sz,
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171 "PLAB clipping computation in adjust_desired_plab_sz()"
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172 " may be incorrect");
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173 }
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174
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175 static const size_t min_size() {
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176 return ParGCAllocBuffer::min_size();
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177 }
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178
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179 static const size_t max_size() {
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180 return ParGCAllocBuffer::max_size();
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181 }
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182
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183 size_t desired_plab_sz() {
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184 return _desired_plab_sz;
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185 }
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186
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187 void adjust_desired_plab_sz(); // filter computation, latches output to
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188 // _desired_plab_sz, clears sensor accumulators
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189
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190 void add_allocated(size_t v) {
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191 Atomic::add_ptr(v, &_allocated);
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192 }
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193
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194 void add_unused(size_t v) {
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195 Atomic::add_ptr(v, &_unused);
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196 }
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197
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198 void add_wasted(size_t v) {
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199 Atomic::add_ptr(v, &_wasted);
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200 }
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201 };
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202
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203 class ParGCAllocBufferWithBOT: public ParGCAllocBuffer {
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204 BlockOffsetArrayContigSpace _bt;
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205 BlockOffsetSharedArray* _bsa;
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206 HeapWord* _true_end; // end of the whole ParGCAllocBuffer
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207
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208 static const size_t ChunkSizeInWords;
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209 static const size_t ChunkSizeInBytes;
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210 HeapWord* allocate_slow(size_t word_sz);
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211
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212 void fill_region_with_block(MemRegion mr, bool contig);
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213
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214 public:
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215 ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa);
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216
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217 HeapWord* allocate(size_t word_sz) {
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218 HeapWord* res = ParGCAllocBuffer::allocate(word_sz);
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219 if (res != NULL) {
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220 _bt.alloc_block(res, word_sz);
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221 } else {
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222 res = allocate_slow(word_sz);
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223 }
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224 return res;
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225 }
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226
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227 void undo_allocation(HeapWord* obj, size_t word_sz);
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228
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229 void set_buf(HeapWord* buf_start) {
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230 ParGCAllocBuffer::set_buf(buf_start);
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231 _true_end = _hard_end;
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232 _bt.set_region(MemRegion(buf_start, word_sz()));
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233 _bt.initialize_threshold();
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234 }
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235
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236 void retire(bool end_of_gc, bool retain);
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237
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238 MemRegion range() {
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239 return MemRegion(_top, _true_end);
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240 }
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241 };
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