1 /* |
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2 * Copyright (c) 2001, 2019, 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_GC_CMS_ALLOCATIONSTATS_HPP |
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26 #define SHARE_GC_CMS_ALLOCATIONSTATS_HPP |
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27 |
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28 #include "gc/shared/gcUtil.hpp" |
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29 #include "logging/log.hpp" |
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30 #include "runtime/globals.hpp" |
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31 #include "utilities/globalDefinitions.hpp" |
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32 #include "utilities/macros.hpp" |
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33 |
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34 class AllocationStats { |
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35 // A duration threshold (in ms) used to filter |
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36 // possibly unreliable samples. |
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37 static float _threshold; |
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38 |
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39 // We measure the demand between the end of the previous sweep and |
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40 // beginning of this sweep: |
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41 // Count(end_last_sweep) - Count(start_this_sweep) |
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42 // + split_births(between) - split_deaths(between) |
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43 // The above number divided by the time since the end of the |
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44 // previous sweep gives us a time rate of demand for blocks |
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45 // of this size. We compute a padded average of this rate as |
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46 // our current estimate for the time rate of demand for blocks |
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47 // of this size. Similarly, we keep a padded average for the time |
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48 // between sweeps. Our current estimate for demand for blocks of |
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49 // this size is then simply computed as the product of these two |
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50 // estimates. |
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51 AdaptivePaddedAverage _demand_rate_estimate; |
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52 |
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53 ssize_t _desired; // Demand estimate computed as described above |
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54 ssize_t _coal_desired; // desired +/- small-percent for tuning coalescing |
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55 |
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56 ssize_t _surplus; // count - (desired +/- small-percent), |
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57 // used to tune splitting in best fit |
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58 ssize_t _bfr_surp; // surplus at start of current sweep |
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59 ssize_t _prev_sweep; // count from end of previous sweep |
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60 ssize_t _before_sweep; // count from before current sweep |
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61 ssize_t _coal_births; // additional chunks from coalescing |
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62 ssize_t _coal_deaths; // loss from coalescing |
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63 ssize_t _split_births; // additional chunks from splitting |
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64 ssize_t _split_deaths; // loss from splitting |
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65 size_t _returned_bytes; // number of bytes returned to list. |
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66 public: |
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67 void initialize(bool split_birth = false); |
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68 |
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69 AllocationStats() { |
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70 initialize(); |
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71 } |
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72 |
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73 // The rate estimate is in blocks per second. |
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74 void compute_desired(size_t count, |
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75 float inter_sweep_current, |
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76 float inter_sweep_estimate, |
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77 float intra_sweep_estimate) { |
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78 // If the latest inter-sweep time is below our granularity |
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79 // of measurement, we may call in here with |
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80 // inter_sweep_current == 0. However, even for suitably small |
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81 // but non-zero inter-sweep durations, we may not trust the accuracy |
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82 // of accumulated data, since it has not been "integrated" |
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83 // (read "low-pass-filtered") long enough, and would be |
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84 // vulnerable to noisy glitches. In such cases, we |
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85 // ignore the current sample and use currently available |
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86 // historical estimates. |
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87 assert(prev_sweep() + split_births() + coal_births() // "Total Production Stock" |
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88 >= split_deaths() + coal_deaths() + (ssize_t)count, // "Current stock + depletion" |
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89 "Conservation Principle"); |
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90 if (inter_sweep_current > _threshold) { |
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91 ssize_t demand = prev_sweep() - (ssize_t)count + split_births() + coal_births() |
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92 - split_deaths() - coal_deaths(); |
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93 assert(demand >= 0, |
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94 "Demand (" SSIZE_FORMAT ") should be non-negative for " |
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95 PTR_FORMAT " (size=" SIZE_FORMAT ")", |
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96 demand, p2i(this), count); |
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97 // Defensive: adjust for imprecision in event counting |
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98 if (demand < 0) { |
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99 demand = 0; |
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100 } |
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101 float old_rate = _demand_rate_estimate.padded_average(); |
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102 float rate = ((float)demand)/inter_sweep_current; |
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103 _demand_rate_estimate.sample(rate); |
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104 float new_rate = _demand_rate_estimate.padded_average(); |
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105 ssize_t old_desired = _desired; |
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106 float delta_ise = (CMSExtrapolateSweep ? intra_sweep_estimate : 0.0); |
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107 _desired = (ssize_t)(new_rate * (inter_sweep_estimate + delta_ise)); |
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108 log_trace(gc, freelist)("demand: " SSIZE_FORMAT ", old_rate: %f, current_rate: %f, " |
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109 "new_rate: %f, old_desired: " SSIZE_FORMAT ", new_desired: " SSIZE_FORMAT, |
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110 demand, old_rate, rate, new_rate, old_desired, _desired); |
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111 } |
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112 } |
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113 |
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114 ssize_t desired() const { return _desired; } |
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115 void set_desired(ssize_t v) { _desired = v; } |
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116 |
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117 ssize_t coal_desired() const { return _coal_desired; } |
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118 void set_coal_desired(ssize_t v) { _coal_desired = v; } |
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119 |
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120 ssize_t surplus() const { return _surplus; } |
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121 void set_surplus(ssize_t v) { _surplus = v; } |
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122 void increment_surplus() { _surplus++; } |
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123 void decrement_surplus() { _surplus--; } |
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124 |
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125 ssize_t bfr_surp() const { return _bfr_surp; } |
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126 void set_bfr_surp(ssize_t v) { _bfr_surp = v; } |
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127 ssize_t prev_sweep() const { return _prev_sweep; } |
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128 void set_prev_sweep(ssize_t v) { _prev_sweep = v; } |
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129 ssize_t before_sweep() const { return _before_sweep; } |
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130 void set_before_sweep(ssize_t v) { _before_sweep = v; } |
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131 |
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132 ssize_t coal_births() const { return _coal_births; } |
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133 void set_coal_births(ssize_t v) { _coal_births = v; } |
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134 void increment_coal_births() { _coal_births++; } |
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135 |
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136 ssize_t coal_deaths() const { return _coal_deaths; } |
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137 void set_coal_deaths(ssize_t v) { _coal_deaths = v; } |
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138 void increment_coal_deaths() { _coal_deaths++; } |
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139 |
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140 ssize_t split_births() const { return _split_births; } |
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141 void set_split_births(ssize_t v) { _split_births = v; } |
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142 void increment_split_births() { _split_births++; } |
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143 |
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144 ssize_t split_deaths() const { return _split_deaths; } |
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145 void set_split_deaths(ssize_t v) { _split_deaths = v; } |
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146 void increment_split_deaths() { _split_deaths++; } |
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147 |
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148 NOT_PRODUCT( |
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149 size_t returned_bytes() const { return _returned_bytes; } |
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150 void set_returned_bytes(size_t v) { _returned_bytes = v; } |
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151 ) |
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152 }; |
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153 |
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154 #endif // SHARE_GC_CMS_ALLOCATIONSTATS_HPP |
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