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1 /*
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2 * Copyright 2002-2007 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 // This class keeps statistical information and computes the
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26 // optimal free space for both the young and old generation
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27 // based on current application characteristics (based on gc cost
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28 // and application footprint).
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29 //
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30 // It also computes an optimal tenuring threshold between the young
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31 // and old generations, so as to equalize the cost of collections
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32 // of those generations, as well as optimial survivor space sizes
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33 // for the young generation.
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34 //
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35 // While this class is specifically intended for a generational system
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36 // consisting of a young gen (containing an Eden and two semi-spaces)
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37 // and a tenured gen, as well as a perm gen for reflective data, it
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38 // makes NO references to specific generations.
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39 //
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40 // 05/02/2003 Update
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41 // The 1.5 policy makes use of data gathered for the costs of GC on
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42 // specific generations. That data does reference specific
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43 // generation. Also diagnostics specific to generations have
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44 // been added.
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45
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46 // Forward decls
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47 class elapsedTimer;
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48
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49 class PSAdaptiveSizePolicy : public AdaptiveSizePolicy {
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50 friend class PSGCAdaptivePolicyCounters;
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51 private:
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52 // These values are used to record decisions made during the
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53 // policy. For example, if the young generation was decreased
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54 // to decrease the GC cost of minor collections the value
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55 // decrease_young_gen_for_throughput_true is used.
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56
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57 // Last calculated sizes, in bytes, and aligned
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58 // NEEDS_CLEANUP should use sizes.hpp, but it works in ints, not size_t's
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59
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60 // Time statistics
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61 AdaptivePaddedAverage* _avg_major_pause;
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62
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63 // Footprint statistics
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64 AdaptiveWeightedAverage* _avg_base_footprint;
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65
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66 // Statistical data gathered for GC
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67 GCStats _gc_stats;
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68
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69 size_t _survivor_size_limit; // Limit in bytes of survivor size
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70 const double _collection_cost_margin_fraction;
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71
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72 // Variable for estimating the major and minor pause times.
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73 // These variables represent linear least-squares fits of
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74 // the data.
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75 // major pause time vs. old gen size
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76 LinearLeastSquareFit* _major_pause_old_estimator;
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77 // major pause time vs. young gen size
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78 LinearLeastSquareFit* _major_pause_young_estimator;
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79
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80
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81 // These record the most recent collection times. They
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82 // are available as an alternative to using the averages
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83 // for making ergonomic decisions.
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84 double _latest_major_mutator_interval_seconds;
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85
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86 const size_t _intra_generation_alignment; // alignment for eden, survivors
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87
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88 const double _gc_minor_pause_goal_sec; // goal for maximum minor gc pause
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89
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90 // The amount of live data in the heap at the last full GC, used
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91 // as a baseline to help us determine when we need to perform the
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92 // next full GC.
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93 size_t _live_at_last_full_gc;
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94
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95 // decrease/increase the old generation for minor pause time
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96 int _change_old_gen_for_min_pauses;
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97
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98 // increase/decrease the young generation for major pause time
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99 int _change_young_gen_for_maj_pauses;
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100
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101
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102 // Flag indicating that the adaptive policy is ready to use
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103 bool _old_gen_policy_is_ready;
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104
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105 // Changing the generation sizing depends on the data that is
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106 // gathered about the effects of changes on the pause times and
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107 // throughput. These variable count the number of data points
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108 // gathered. The policy may use these counters as a threshhold
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109 // for reliable data.
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110 julong _young_gen_change_for_major_pause_count;
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111
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112 // To facilitate faster growth at start up, supplement the normal
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113 // growth percentage for the young gen eden and the
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114 // old gen space for promotion with these value which decay
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115 // with increasing collections.
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116 uint _young_gen_size_increment_supplement;
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117 uint _old_gen_size_increment_supplement;
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118
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119 // The number of bytes absorbed from eden into the old gen by moving the
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120 // boundary over live data.
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121 size_t _bytes_absorbed_from_eden;
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122
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123 private:
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124
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125 // Accessors
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126 AdaptivePaddedAverage* avg_major_pause() const { return _avg_major_pause; }
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127 double gc_minor_pause_goal_sec() const { return _gc_minor_pause_goal_sec; }
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128
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129 // Change the young generation size to achieve a minor GC pause time goal
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130 void adjust_for_minor_pause_time(bool is_full_gc,
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131 size_t* desired_promo_size_ptr,
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132 size_t* desired_eden_size_ptr);
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133 // Change the generation sizes to achieve a GC pause time goal
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134 // Returned sizes are not necessarily aligned.
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135 void adjust_for_pause_time(bool is_full_gc,
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136 size_t* desired_promo_size_ptr,
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137 size_t* desired_eden_size_ptr);
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138 // Change the generation sizes to achieve an application throughput goal
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139 // Returned sizes are not necessarily aligned.
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140 void adjust_for_throughput(bool is_full_gc,
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141 size_t* desired_promo_size_ptr,
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142 size_t* desired_eden_size_ptr);
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143 // Change the generation sizes to achieve minimum footprint
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144 // Returned sizes are not aligned.
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145 size_t adjust_promo_for_footprint(size_t desired_promo_size,
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146 size_t desired_total);
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147 size_t adjust_eden_for_footprint(size_t desired_promo_size,
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148 size_t desired_total);
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149
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150 // Size in bytes for an increment or decrement of eden.
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151 virtual size_t eden_increment(size_t cur_eden, uint percent_change);
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152 virtual size_t eden_decrement(size_t cur_eden);
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153 size_t eden_decrement_aligned_down(size_t cur_eden);
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154 size_t eden_increment_with_supplement_aligned_up(size_t cur_eden);
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155
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156 // Size in bytes for an increment or decrement of the promotion area
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157 virtual size_t promo_increment(size_t cur_promo, uint percent_change);
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158 virtual size_t promo_decrement(size_t cur_promo);
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159 size_t promo_decrement_aligned_down(size_t cur_promo);
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160 size_t promo_increment_with_supplement_aligned_up(size_t cur_promo);
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161
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162 // Decay the supplemental growth additive.
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163 void decay_supplemental_growth(bool is_full_gc);
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164
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165 // Returns a change that has been scaled down. Result
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166 // is not aligned. (If useful, move to some shared
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167 // location.)
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168 size_t scale_down(size_t change, double part, double total);
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169
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170 protected:
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171 // Time accessors
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172
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173 // Footprint accessors
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174 size_t live_space() const {
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175 return (size_t)(avg_base_footprint()->average() +
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176 avg_young_live()->average() +
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177 avg_old_live()->average());
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178 }
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179 size_t free_space() const {
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180 return _eden_size + _promo_size;
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181 }
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182
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183 void set_promo_size(size_t new_size) {
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184 _promo_size = new_size;
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185 }
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186 void set_survivor_size(size_t new_size) {
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187 _survivor_size = new_size;
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188 }
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189
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190 // Update estimators
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191 void update_minor_pause_old_estimator(double minor_pause_in_ms);
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192
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193 virtual GCPolicyKind kind() const { return _gc_ps_adaptive_size_policy; }
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194
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195 public:
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196 // Use by ASPSYoungGen and ASPSOldGen to limit boundary moving.
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197 size_t eden_increment_aligned_up(size_t cur_eden);
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198 size_t eden_increment_aligned_down(size_t cur_eden);
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199 size_t promo_increment_aligned_up(size_t cur_promo);
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200 size_t promo_increment_aligned_down(size_t cur_promo);
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201
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202 virtual size_t eden_increment(size_t cur_eden);
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203 virtual size_t promo_increment(size_t cur_promo);
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204
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205 // Accessors for use by performance counters
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206 AdaptivePaddedNoZeroDevAverage* avg_promoted() const {
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207 return _gc_stats.avg_promoted();
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208 }
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209 AdaptiveWeightedAverage* avg_base_footprint() const {
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210 return _avg_base_footprint;
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211 }
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212
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213 // Input arguments are initial free space sizes for young and old
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214 // generations, the initial survivor space size, the
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215 // alignment values and the pause & throughput goals.
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216 //
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217 // NEEDS_CLEANUP this is a singleton object
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218 PSAdaptiveSizePolicy(size_t init_eden_size,
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219 size_t init_promo_size,
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220 size_t init_survivor_size,
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221 size_t intra_generation_alignment,
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222 double gc_pause_goal_sec,
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223 double gc_minor_pause_goal_sec,
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224 uint gc_time_ratio);
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225
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226 // Methods indicating events of interest to the adaptive size policy,
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227 // called by GC algorithms. It is the responsibility of users of this
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228 // policy to call these methods at the correct times!
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229 void major_collection_begin();
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230 void major_collection_end(size_t amount_live, GCCause::Cause gc_cause);
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231
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232 //
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233 void tenured_allocation(size_t size) {
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234 _avg_pretenured->sample(size);
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235 }
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236
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237 // Accessors
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238 // NEEDS_CLEANUP should use sizes.hpp
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239
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240 size_t calculated_old_free_size_in_bytes() const {
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241 return (size_t)(_promo_size + avg_promoted()->padded_average());
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242 }
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243
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244 size_t average_old_live_in_bytes() const {
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245 return (size_t) avg_old_live()->average();
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246 }
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247
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248 size_t average_promoted_in_bytes() const {
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249 return (size_t)avg_promoted()->average();
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250 }
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251
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252 size_t padded_average_promoted_in_bytes() const {
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253 return (size_t)avg_promoted()->padded_average();
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254 }
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255
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256 int change_young_gen_for_maj_pauses() {
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257 return _change_young_gen_for_maj_pauses;
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258 }
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259 void set_change_young_gen_for_maj_pauses(int v) {
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260 _change_young_gen_for_maj_pauses = v;
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261 }
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262
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263 int change_old_gen_for_min_pauses() {
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264 return _change_old_gen_for_min_pauses;
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265 }
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266 void set_change_old_gen_for_min_pauses(int v) {
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267 _change_old_gen_for_min_pauses = v;
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268 }
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269
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270 // Return true if the old generation size was changed
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271 // to try to reach a pause time goal.
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272 bool old_gen_changed_for_pauses() {
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273 bool result = _change_old_gen_for_maj_pauses != 0 ||
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274 _change_old_gen_for_min_pauses != 0;
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275 return result;
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276 }
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277
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278 // Return true if the young generation size was changed
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279 // to try to reach a pause time goal.
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280 bool young_gen_changed_for_pauses() {
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281 bool result = _change_young_gen_for_min_pauses != 0 ||
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282 _change_young_gen_for_maj_pauses != 0;
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283 return result;
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284 }
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285 // end flags for pause goal
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286
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287 // Return true if the old generation size was changed
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288 // to try to reach a throughput goal.
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289 bool old_gen_changed_for_throughput() {
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290 bool result = _change_old_gen_for_throughput != 0;
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291 return result;
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292 }
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293
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294 // Return true if the young generation size was changed
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295 // to try to reach a throughput goal.
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296 bool young_gen_changed_for_throughput() {
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297 bool result = _change_young_gen_for_throughput != 0;
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298 return result;
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299 }
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300
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301 int decrease_for_footprint() { return _decrease_for_footprint; }
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302
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303
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304 // Accessors for estimators. The slope of the linear fit is
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305 // currently all that is used for making decisions.
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306
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307 LinearLeastSquareFit* major_pause_old_estimator() {
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308 return _major_pause_old_estimator;
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309 }
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310
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311 LinearLeastSquareFit* major_pause_young_estimator() {
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312 return _major_pause_young_estimator;
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313 }
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314
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315
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316 virtual void clear_generation_free_space_flags();
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317
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318 float major_pause_old_slope() { return _major_pause_old_estimator->slope(); }
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319 float major_pause_young_slope() {
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320 return _major_pause_young_estimator->slope();
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321 }
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322 float major_collection_slope() { return _major_collection_estimator->slope();}
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323
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324 bool old_gen_policy_is_ready() { return _old_gen_policy_is_ready; }
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325
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326 // Given the amount of live data in the heap, should we
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327 // perform a Full GC?
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328 bool should_full_GC(size_t live_in_old_gen);
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329
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330 // Calculates optimial free space sizes for both the old and young
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331 // generations. Stores results in _eden_size and _promo_size.
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332 // Takes current used space in all generations as input, as well
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333 // as an indication if a full gc has just been performed, for use
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334 // in deciding if an OOM error should be thrown.
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335 void compute_generation_free_space(size_t young_live,
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336 size_t eden_live,
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337 size_t old_live,
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338 size_t perm_live,
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339 size_t cur_eden, // current eden in bytes
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340 size_t max_old_gen_size,
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341 size_t max_eden_size,
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342 bool is_full_gc,
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343 GCCause::Cause gc_cause);
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344
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345 // Calculates new survivor space size; returns a new tenuring threshold
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346 // value. Stores new survivor size in _survivor_size.
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347 int compute_survivor_space_size_and_threshold(bool is_survivor_overflow,
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348 int tenuring_threshold,
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349 size_t survivor_limit);
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350
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351 // Return the maximum size of a survivor space if the young generation were of
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352 // size gen_size.
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353 size_t max_survivor_size(size_t gen_size) {
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354 // Never allow the target survivor size to grow more than MinSurvivorRatio
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355 // of the young generation size. We cannot grow into a two semi-space
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356 // system, with Eden zero sized. Even if the survivor space grows, from()
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357 // might grow by moving the bottom boundary "down" -- so from space will
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358 // remain almost full anyway (top() will be near end(), but there will be a
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359 // large filler object at the bottom).
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360 const size_t sz = gen_size / MinSurvivorRatio;
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361 const size_t alignment = _intra_generation_alignment;
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362 return sz > alignment ? align_size_down(sz, alignment) : alignment;
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363 }
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364
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365 size_t live_at_last_full_gc() {
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366 return _live_at_last_full_gc;
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367 }
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368
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369 size_t bytes_absorbed_from_eden() const { return _bytes_absorbed_from_eden; }
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370 void reset_bytes_absorbed_from_eden() { _bytes_absorbed_from_eden = 0; }
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371
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372 void set_bytes_absorbed_from_eden(size_t val) {
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373 _bytes_absorbed_from_eden = val;
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374 }
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375
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376 // Update averages that are always used (even
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377 // if adaptive sizing is turned off).
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378 void update_averages(bool is_survivor_overflow,
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379 size_t survived,
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380 size_t promoted);
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381
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382 // Printing support
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383 virtual bool print_adaptive_size_policy_on(outputStream* st) const;
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384 };
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