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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 class CompactibleFreeListSpace;
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26
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27 // A class for maintaining a free list of FreeChunk's. The FreeList
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28 // maintains a the structure of the list (head, tail, etc.) plus
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29 // statistics for allocations from the list. The links between items
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30 // are not part of FreeList. The statistics are
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31 // used to make decisions about coalescing FreeChunk's when they
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32 // are swept during collection.
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33 //
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34 // See the corresponding .cpp file for a description of the specifics
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35 // for that implementation.
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36
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37 class Mutex;
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38
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39 class FreeList VALUE_OBJ_CLASS_SPEC {
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40 friend class CompactibleFreeListSpace;
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41 FreeChunk* _head; // List of free chunks
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42 FreeChunk* _tail; // Tail of list of free chunks
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43 size_t _size; // Size in Heap words of each chunks
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44 ssize_t _count; // Number of entries in list
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45 size_t _hint; // next larger size list with a positive surplus
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46
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47 AllocationStats _allocation_stats; // statistics for smart allocation
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48
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49 #ifdef ASSERT
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50 Mutex* _protecting_lock;
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51 #endif
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52
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53 // Asserts false if the protecting lock (if any) is not held.
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54 void assert_proper_lock_protection_work() const PRODUCT_RETURN;
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55 void assert_proper_lock_protection() const {
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56 #ifdef ASSERT
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57 if (_protecting_lock != NULL)
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58 assert_proper_lock_protection_work();
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59 #endif
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60 }
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61
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62 // Initialize the allocation statistics.
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63 protected:
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64 void init_statistics();
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65 void set_count(ssize_t v) { _count = v;}
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66 void increment_count() { _count++; }
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67 void decrement_count() {
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68 _count--;
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69 assert(_count >= 0, "Count should not be negative"); }
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70
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71 public:
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72 // Constructor
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73 // Construct a list without any entries.
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74 FreeList();
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75 // Construct a list with "fc" as the first (and lone) entry in the list.
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76 FreeList(FreeChunk* fc);
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77 // Construct a list which will have a FreeChunk at address "addr" and
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78 // of size "size" as the first (and lone) entry in the list.
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79 FreeList(HeapWord* addr, size_t size);
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80
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81 // Reset the head, tail, hint, and count of a free list.
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82 void reset(size_t hint);
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83
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84 // Declare the current free list to be protected by the given lock.
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85 #ifdef ASSERT
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86 void set_protecting_lock(Mutex* protecting_lock) {
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87 _protecting_lock = protecting_lock;
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88 }
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89 #endif
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90
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91 // Accessors.
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92 FreeChunk* head() const {
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93 assert_proper_lock_protection();
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94 return _head;
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95 }
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96 void set_head(FreeChunk* v) {
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97 assert_proper_lock_protection();
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98 _head = v;
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99 assert(!_head || _head->size() == _size, "bad chunk size");
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100 }
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101 // Set the head of the list and set the prev field of non-null
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102 // values to NULL.
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103 void link_head(FreeChunk* v) {
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104 assert_proper_lock_protection();
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105 set_head(v);
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106 // If this method is not used (just set the head instead),
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107 // this check can be avoided.
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108 if (v != NULL) {
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109 v->linkPrev(NULL);
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110 }
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111 }
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112
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113 FreeChunk* tail() const {
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114 assert_proper_lock_protection();
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115 return _tail;
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116 }
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117 void set_tail(FreeChunk* v) {
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118 assert_proper_lock_protection();
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119 _tail = v;
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120 assert(!_tail || _tail->size() == _size, "bad chunk size");
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121 }
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122 // Set the tail of the list and set the next field of non-null
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123 // values to NULL.
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124 void link_tail(FreeChunk* v) {
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125 assert_proper_lock_protection();
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126 set_tail(v);
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127 if (v != NULL) {
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128 v->clearNext();
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129 }
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130 }
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131
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132 // No locking checks in read-accessors: lock-free reads (only) are benign.
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133 // Readers are expected to have the lock if they are doing work that
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134 // requires atomicity guarantees in sections of code.
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135 size_t size() const {
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136 return _size;
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137 }
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138 void set_size(size_t v) {
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139 assert_proper_lock_protection();
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140 _size = v;
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141 }
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142 ssize_t count() const {
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143 return _count;
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144 }
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145 size_t hint() const {
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146 return _hint;
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147 }
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148 void set_hint(size_t v) {
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149 assert_proper_lock_protection();
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150 assert(v == 0 || _size < v, "Bad hint"); _hint = v;
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151 }
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152
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153 // Accessors for statistics
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154 AllocationStats* allocation_stats() {
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155 assert_proper_lock_protection();
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156 return &_allocation_stats;
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157 }
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158
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159 ssize_t desired() const {
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160 return _allocation_stats.desired();
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161 }
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162 void compute_desired(float inter_sweep_current,
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163 float inter_sweep_estimate) {
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164 assert_proper_lock_protection();
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165 _allocation_stats.compute_desired(_count,
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166 inter_sweep_current,
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167 inter_sweep_estimate);
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168 }
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169 ssize_t coalDesired() const {
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170 return _allocation_stats.coalDesired();
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171 }
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172 void set_coalDesired(ssize_t v) {
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173 assert_proper_lock_protection();
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174 _allocation_stats.set_coalDesired(v);
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175 }
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176
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177 ssize_t surplus() const {
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178 return _allocation_stats.surplus();
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179 }
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180 void set_surplus(ssize_t v) {
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181 assert_proper_lock_protection();
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182 _allocation_stats.set_surplus(v);
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183 }
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184 void increment_surplus() {
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185 assert_proper_lock_protection();
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186 _allocation_stats.increment_surplus();
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187 }
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188 void decrement_surplus() {
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189 assert_proper_lock_protection();
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190 _allocation_stats.decrement_surplus();
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191 }
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192
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193 ssize_t bfrSurp() const {
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194 return _allocation_stats.bfrSurp();
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195 }
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196 void set_bfrSurp(ssize_t v) {
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197 assert_proper_lock_protection();
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198 _allocation_stats.set_bfrSurp(v);
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199 }
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200 ssize_t prevSweep() const {
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201 return _allocation_stats.prevSweep();
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202 }
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203 void set_prevSweep(ssize_t v) {
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204 assert_proper_lock_protection();
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205 _allocation_stats.set_prevSweep(v);
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206 }
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207 ssize_t beforeSweep() const {
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208 return _allocation_stats.beforeSweep();
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209 }
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210 void set_beforeSweep(ssize_t v) {
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211 assert_proper_lock_protection();
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212 _allocation_stats.set_beforeSweep(v);
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213 }
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214
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215 ssize_t coalBirths() const {
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216 return _allocation_stats.coalBirths();
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217 }
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218 void set_coalBirths(ssize_t v) {
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219 assert_proper_lock_protection();
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220 _allocation_stats.set_coalBirths(v);
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221 }
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222 void increment_coalBirths() {
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223 assert_proper_lock_protection();
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224 _allocation_stats.increment_coalBirths();
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225 }
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226
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227 ssize_t coalDeaths() const {
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228 return _allocation_stats.coalDeaths();
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229 }
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230 void set_coalDeaths(ssize_t v) {
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231 assert_proper_lock_protection();
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232 _allocation_stats.set_coalDeaths(v);
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233 }
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234 void increment_coalDeaths() {
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235 assert_proper_lock_protection();
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236 _allocation_stats.increment_coalDeaths();
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237 }
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238
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239 ssize_t splitBirths() const {
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240 return _allocation_stats.splitBirths();
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241 }
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242 void set_splitBirths(ssize_t v) {
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243 assert_proper_lock_protection();
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244 _allocation_stats.set_splitBirths(v);
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245 }
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246 void increment_splitBirths() {
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247 assert_proper_lock_protection();
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248 _allocation_stats.increment_splitBirths();
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249 }
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250
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251 ssize_t splitDeaths() const {
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252 return _allocation_stats.splitDeaths();
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253 }
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254 void set_splitDeaths(ssize_t v) {
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255 assert_proper_lock_protection();
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256 _allocation_stats.set_splitDeaths(v);
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257 }
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258 void increment_splitDeaths() {
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259 assert_proper_lock_protection();
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260 _allocation_stats.increment_splitDeaths();
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261 }
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262
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263 NOT_PRODUCT(
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264 // For debugging. The "_returnedBytes" in all the lists are summed
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265 // and compared with the total number of bytes swept during a
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266 // collection.
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267 size_t returnedBytes() const { return _allocation_stats.returnedBytes(); }
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268 void set_returnedBytes(size_t v) { _allocation_stats.set_returnedBytes(v); }
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269 void increment_returnedBytes_by(size_t v) {
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270 _allocation_stats.set_returnedBytes(_allocation_stats.returnedBytes() + v);
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271 }
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272 )
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273
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274 // Unlink head of list and return it. Returns NULL if
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275 // the list is empty.
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276 FreeChunk* getChunkAtHead();
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277
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278 // Remove the first "n" or "count", whichever is smaller, chunks from the
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279 // list, setting "fl", which is required to be empty, to point to them.
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280 void getFirstNChunksFromList(size_t n, FreeList* fl);
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281
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282 // Unlink this chunk from it's free list
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283 void removeChunk(FreeChunk* fc);
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284
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285 // Add this chunk to this free list.
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286 void returnChunkAtHead(FreeChunk* fc);
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287 void returnChunkAtTail(FreeChunk* fc);
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288
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289 // Similar to returnChunk* but also records some diagnostic
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290 // information.
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291 void returnChunkAtHead(FreeChunk* fc, bool record_return);
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292 void returnChunkAtTail(FreeChunk* fc, bool record_return);
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293
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294 // Prepend "fl" (whose size is required to be the same as that of "this")
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295 // to the front of "this" list.
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296 void prepend(FreeList* fl);
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297
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298 // Verify that the chunk is in the list.
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299 // found. Return NULL if "fc" is not found.
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300 bool verifyChunkInFreeLists(FreeChunk* fc) const;
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301 };
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