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17764
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1 /*
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2 * Copyright (c) 2014, 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 #include "precompiled.hpp"
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26 #include "classfile/javaClasses.hpp"
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27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
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28 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
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29 #include "gc_implementation/g1/g1StringDedup.hpp"
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30 #include "gc_implementation/g1/g1StringDedupQueue.hpp"
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31 #include "gc_implementation/g1/g1StringDedupStat.hpp"
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32 #include "gc_implementation/g1/g1StringDedupTable.hpp"
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33 #include "gc_implementation/g1/g1StringDedupThread.hpp"
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34
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35 bool G1StringDedup::_enabled = false;
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36
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37 void G1StringDedup::initialize() {
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38 assert(UseG1GC, "String deduplication only available with G1");
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39 if (UseStringDeduplication) {
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40 _enabled = true;
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41 G1StringDedupQueue::create();
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42 G1StringDedupTable::create();
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43 G1StringDedupThread::create();
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44 }
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45 }
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46
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47 bool G1StringDedup::is_candidate_from_mark(oop obj) {
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48 if (java_lang_String::is_instance(obj)) {
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49 bool from_young = G1CollectedHeap::heap()->heap_region_containing_raw(obj)->is_young();
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50 if (from_young && obj->age() < StringDeduplicationAgeThreshold) {
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51 // Candidate found. String is being evacuated from young to old but has not
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52 // reached the deduplication age threshold, i.e. has not previously been a
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53 // candidate during its life in the young generation.
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54 return true;
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55 }
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56 }
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57
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58 // Not a candidate
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59 return false;
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60 }
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61
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62 void G1StringDedup::enqueue_from_mark(oop java_string) {
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63 assert(is_enabled(), "String deduplication not enabled");
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64 if (is_candidate_from_mark(java_string)) {
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65 G1StringDedupQueue::push(0 /* worker_id */, java_string);
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66 }
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67 }
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68
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69 bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) {
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70 if (from_young && java_lang_String::is_instance(obj)) {
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71 if (to_young && obj->age() == StringDeduplicationAgeThreshold) {
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72 // Candidate found. String is being evacuated from young to young and just
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73 // reached the deduplication age threshold.
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74 return true;
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75 }
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76 if (!to_young && obj->age() < StringDeduplicationAgeThreshold) {
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77 // Candidate found. String is being evacuated from young to old but has not
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78 // reached the deduplication age threshold, i.e. has not previously been a
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79 // candidate during its life in the young generation.
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80 return true;
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81 }
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82 }
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83
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84 // Not a candidate
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85 return false;
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86 }
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87
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88 void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) {
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89 assert(is_enabled(), "String deduplication not enabled");
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90 if (is_candidate_from_evacuation(from_young, to_young, java_string)) {
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91 G1StringDedupQueue::push(worker_id, java_string);
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92 }
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93 }
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94
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95 void G1StringDedup::deduplicate(oop java_string) {
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96 assert(is_enabled(), "String deduplication not enabled");
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97 G1StringDedupStat dummy; // Statistics from this path is never used
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98 G1StringDedupTable::deduplicate(java_string, dummy);
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99 }
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100
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101 void G1StringDedup::oops_do(OopClosure* keep_alive) {
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102 assert(is_enabled(), "String deduplication not enabled");
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103 unlink_or_oops_do(NULL, keep_alive);
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104 }
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105
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106 void G1StringDedup::unlink(BoolObjectClosure* is_alive) {
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107 assert(is_enabled(), "String deduplication not enabled");
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108 // Don't allow a potential resize or rehash during unlink, as the unlink
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109 // operation itself might remove enough entries to invalidate such a decision.
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110 unlink_or_oops_do(is_alive, NULL, false /* allow_resize_and_rehash */);
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111 }
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112
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113 //
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114 // Task for parallel unlink_or_oops_do() operation on the deduplication queue
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115 // and table.
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116 //
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117 class G1StringDedupUnlinkOrOopsDoTask : public AbstractGangTask {
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118 private:
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119 G1StringDedupUnlinkOrOopsDoClosure _cl;
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120
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121 public:
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122 G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,
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123 OopClosure* keep_alive,
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124 bool allow_resize_and_rehash) :
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125 AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"),
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126 _cl(is_alive, keep_alive, allow_resize_and_rehash) {
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127 }
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128
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129 virtual void work(uint worker_id) {
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130 double queue_fixup_start = os::elapsedTime();
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131 G1StringDedupQueue::unlink_or_oops_do(&_cl);
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132
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133 double table_fixup_start = os::elapsedTime();
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134 G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id);
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135
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136 double queue_fixup_time_ms = (table_fixup_start - queue_fixup_start) * 1000.0;
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137 double table_fixup_time_ms = (os::elapsedTime() - table_fixup_start) * 1000.0;
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138 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
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139 g1p->phase_times()->record_string_dedup_queue_fixup_worker_time(worker_id, queue_fixup_time_ms);
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140 g1p->phase_times()->record_string_dedup_table_fixup_worker_time(worker_id, table_fixup_time_ms);
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141 }
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142 };
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143
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144 void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* keep_alive, bool allow_resize_and_rehash) {
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145 assert(is_enabled(), "String deduplication not enabled");
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146 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
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147 g1p->phase_times()->note_string_dedup_fixup_start();
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148 double fixup_start = os::elapsedTime();
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149
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150 G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash);
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151 if (G1CollectedHeap::use_parallel_gc_threads()) {
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152 G1CollectedHeap* g1h = G1CollectedHeap::heap();
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153 g1h->set_par_threads();
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154 g1h->workers()->run_task(&task);
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155 g1h->set_par_threads(0);
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156 } else {
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157 task.work(0);
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158 }
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159
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160 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
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161 g1p->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
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162 g1p->phase_times()->note_string_dedup_fixup_end();
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163 }
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164
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165 void G1StringDedup::threads_do(ThreadClosure* tc) {
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166 assert(is_enabled(), "String deduplication not enabled");
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167 tc->do_thread(G1StringDedupThread::thread());
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168 }
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169
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170 void G1StringDedup::print_worker_threads_on(outputStream* st) {
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171 assert(is_enabled(), "String deduplication not enabled");
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172 G1StringDedupThread::thread()->print_on(st);
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173 st->cr();
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174 }
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175
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176 void G1StringDedup::verify() {
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177 assert(is_enabled(), "String deduplication not enabled");
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178 G1StringDedupQueue::verify();
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179 G1StringDedupTable::verify();
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180 }
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181
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182 G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,
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183 OopClosure* keep_alive,
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184 bool allow_resize_and_rehash) :
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185 _is_alive(is_alive),
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186 _keep_alive(keep_alive),
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187 _resized_table(NULL),
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188 _rehashed_table(NULL),
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189 _next_queue(0),
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190 _next_bucket(0) {
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191 if (allow_resize_and_rehash) {
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192 // If both resize and rehash is needed, only do resize. Rehash of
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193 // the table will eventually happen if the situation persists.
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194 _resized_table = G1StringDedupTable::prepare_resize();
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195 if (!is_resizing()) {
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196 _rehashed_table = G1StringDedupTable::prepare_rehash();
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197 }
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198 }
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199 }
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200
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201 G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() {
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202 assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash");
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203 if (is_resizing()) {
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204 G1StringDedupTable::finish_resize(_resized_table);
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205 } else if (is_rehashing()) {
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206 G1StringDedupTable::finish_rehash(_rehashed_table);
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207 }
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208 }
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