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 #include "precompiled.hpp" |
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26 #include "classfile/stringTable.hpp" |
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27 #include "gc/cms/cmsHeap.inline.hpp" |
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28 #include "gc/cms/compactibleFreeListSpace.hpp" |
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29 #include "gc/cms/concurrentMarkSweepGeneration.hpp" |
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30 #include "gc/cms/parNewGeneration.inline.hpp" |
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31 #include "gc/cms/parOopClosures.inline.hpp" |
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32 #include "gc/serial/defNewGeneration.inline.hpp" |
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33 #include "gc/shared/adaptiveSizePolicy.hpp" |
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34 #include "gc/shared/ageTable.inline.hpp" |
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35 #include "gc/shared/copyFailedInfo.hpp" |
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36 #include "gc/shared/gcHeapSummary.hpp" |
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37 #include "gc/shared/gcTimer.hpp" |
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38 #include "gc/shared/gcTrace.hpp" |
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39 #include "gc/shared/gcTraceTime.inline.hpp" |
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40 #include "gc/shared/genOopClosures.inline.hpp" |
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41 #include "gc/shared/generation.hpp" |
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42 #include "gc/shared/plab.inline.hpp" |
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43 #include "gc/shared/preservedMarks.inline.hpp" |
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44 #include "gc/shared/referencePolicy.hpp" |
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45 #include "gc/shared/referenceProcessorPhaseTimes.hpp" |
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46 #include "gc/shared/space.hpp" |
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47 #include "gc/shared/spaceDecorator.inline.hpp" |
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48 #include "gc/shared/strongRootsScope.hpp" |
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49 #include "gc/shared/taskqueue.inline.hpp" |
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50 #include "gc/shared/weakProcessor.hpp" |
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51 #include "gc/shared/workgroup.hpp" |
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52 #include "gc/shared/workerPolicy.hpp" |
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53 #include "logging/log.hpp" |
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54 #include "logging/logStream.hpp" |
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55 #include "memory/iterator.inline.hpp" |
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56 #include "memory/resourceArea.hpp" |
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57 #include "oops/access.inline.hpp" |
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58 #include "oops/compressedOops.inline.hpp" |
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59 #include "oops/objArrayOop.hpp" |
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60 #include "oops/oop.inline.hpp" |
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61 #include "runtime/atomic.hpp" |
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62 #include "runtime/handles.inline.hpp" |
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63 #include "runtime/java.hpp" |
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64 #include "runtime/thread.inline.hpp" |
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65 #include "utilities/copy.hpp" |
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66 #include "utilities/globalDefinitions.hpp" |
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67 #include "utilities/stack.inline.hpp" |
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68 |
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69 ParScanThreadState::ParScanThreadState(Space* to_space_, |
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70 ParNewGeneration* young_gen_, |
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71 Generation* old_gen_, |
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72 int thread_num_, |
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73 ObjToScanQueueSet* work_queue_set_, |
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74 Stack<oop, mtGC>* overflow_stacks_, |
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75 PreservedMarks* preserved_marks_, |
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76 size_t desired_plab_sz_, |
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77 TaskTerminator& term_) : |
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78 _work_queue(work_queue_set_->queue(thread_num_)), |
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79 _overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL), |
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80 _preserved_marks(preserved_marks_), |
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81 _to_space_alloc_buffer(desired_plab_sz_), |
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82 _to_space_closure(young_gen_, this), |
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83 _old_gen_closure(young_gen_, this), |
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84 _to_space_root_closure(young_gen_, this), |
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85 _older_gen_closure(young_gen_, this), |
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86 _old_gen_root_closure(young_gen_, this), |
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87 _evacuate_followers(this, &_to_space_closure, &_old_gen_closure, |
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88 &_to_space_root_closure, young_gen_, &_old_gen_root_closure, |
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89 work_queue_set_, term_.terminator()), |
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90 _is_alive_closure(young_gen_), |
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91 _scan_weak_ref_closure(young_gen_, this), |
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92 _keep_alive_closure(&_scan_weak_ref_closure), |
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93 _to_space(to_space_), |
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94 _young_gen(young_gen_), |
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95 _old_gen(old_gen_), |
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96 _young_old_boundary(NULL), |
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97 _thread_num(thread_num_), |
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98 _ageTable(false), // false ==> not the global age table, no perf data. |
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99 _to_space_full(false), |
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100 _strong_roots_time(0.0), |
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101 _term_time(0.0) |
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102 { |
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103 #if TASKQUEUE_STATS |
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104 _term_attempts = 0; |
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105 _overflow_refills = 0; |
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106 _overflow_refill_objs = 0; |
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107 #endif // TASKQUEUE_STATS |
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108 |
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109 _survivor_chunk_array = (ChunkArray*) old_gen()->get_data_recorder(thread_num()); |
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110 _start = os::elapsedTime(); |
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111 _old_gen_closure.set_generation(old_gen_); |
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112 _old_gen_root_closure.set_generation(old_gen_); |
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113 } |
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114 |
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115 void ParScanThreadState::record_survivor_plab(HeapWord* plab_start, |
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116 size_t plab_word_size) { |
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117 ChunkArray* sca = survivor_chunk_array(); |
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118 if (sca != NULL) { |
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119 // A non-null SCA implies that we want the PLAB data recorded. |
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120 sca->record_sample(plab_start, plab_word_size); |
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121 } |
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122 } |
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123 |
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124 bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const { |
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125 return new_obj->is_objArray() && |
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126 arrayOop(new_obj)->length() > ParGCArrayScanChunk && |
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127 new_obj != old_obj; |
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128 } |
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129 |
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130 void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) { |
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131 assert(old->is_objArray(), "must be obj array"); |
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132 assert(old->is_forwarded(), "must be forwarded"); |
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133 assert(CMSHeap::heap()->is_in_reserved(old), "must be in heap."); |
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134 assert(!old_gen()->is_in(old), "must be in young generation."); |
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135 |
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136 objArrayOop obj = objArrayOop(old->forwardee()); |
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137 // Process ParGCArrayScanChunk elements now |
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138 // and push the remainder back onto queue |
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139 int start = arrayOop(old)->length(); |
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140 int end = obj->length(); |
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141 int remainder = end - start; |
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142 assert(start <= end, "just checking"); |
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143 if (remainder > 2 * ParGCArrayScanChunk) { |
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144 // Test above combines last partial chunk with a full chunk |
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145 end = start + ParGCArrayScanChunk; |
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146 arrayOop(old)->set_length(end); |
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147 // Push remainder. |
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148 bool ok = work_queue()->push(old); |
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149 assert(ok, "just popped, push must be okay"); |
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150 } else { |
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151 // Restore length so that it can be used if there |
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152 // is a promotion failure and forwarding pointers |
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153 // must be removed. |
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154 arrayOop(old)->set_length(end); |
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155 } |
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156 |
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157 // process our set of indices (include header in first chunk) |
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158 // should make sure end is even (aligned to HeapWord in case of compressed oops) |
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159 if ((HeapWord *)obj < young_old_boundary()) { |
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160 // object is in to_space |
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161 obj->oop_iterate_range(&_to_space_closure, start, end); |
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162 } else { |
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163 // object is in old generation |
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164 obj->oop_iterate_range(&_old_gen_closure, start, end); |
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165 } |
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166 } |
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167 |
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168 void ParScanThreadState::trim_queues(int max_size) { |
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169 ObjToScanQueue* queue = work_queue(); |
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170 do { |
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171 while (queue->size() > (juint)max_size) { |
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172 oop obj_to_scan; |
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173 if (queue->pop_local(obj_to_scan)) { |
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174 if ((HeapWord *)obj_to_scan < young_old_boundary()) { |
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175 if (obj_to_scan->is_objArray() && |
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176 obj_to_scan->is_forwarded() && |
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177 obj_to_scan->forwardee() != obj_to_scan) { |
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178 scan_partial_array_and_push_remainder(obj_to_scan); |
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179 } else { |
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180 // object is in to_space |
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181 obj_to_scan->oop_iterate(&_to_space_closure); |
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182 } |
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183 } else { |
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184 // object is in old generation |
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185 obj_to_scan->oop_iterate(&_old_gen_closure); |
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186 } |
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187 } |
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188 } |
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189 // For the case of compressed oops, we have a private, non-shared |
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190 // overflow stack, so we eagerly drain it so as to more evenly |
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191 // distribute load early. Note: this may be good to do in |
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192 // general rather than delay for the final stealing phase. |
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193 // If applicable, we'll transfer a set of objects over to our |
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194 // work queue, allowing them to be stolen and draining our |
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195 // private overflow stack. |
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196 } while (ParGCTrimOverflow && young_gen()->take_from_overflow_list(this)); |
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197 } |
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198 |
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199 bool ParScanThreadState::take_from_overflow_stack() { |
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200 assert(ParGCUseLocalOverflow, "Else should not call"); |
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201 assert(young_gen()->overflow_list() == NULL, "Error"); |
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202 ObjToScanQueue* queue = work_queue(); |
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203 Stack<oop, mtGC>* const of_stack = overflow_stack(); |
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204 const size_t num_overflow_elems = of_stack->size(); |
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205 const size_t space_available = queue->max_elems() - queue->size(); |
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206 const size_t num_take_elems = MIN3(space_available / 4, |
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207 (size_t)ParGCDesiredObjsFromOverflowList, |
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208 num_overflow_elems); |
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209 // Transfer the most recent num_take_elems from the overflow |
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210 // stack to our work queue. |
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211 for (size_t i = 0; i != num_take_elems; i++) { |
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212 oop cur = of_stack->pop(); |
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213 oop obj_to_push = cur->forwardee(); |
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214 assert(CMSHeap::heap()->is_in_reserved(cur), "Should be in heap"); |
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215 assert(!old_gen()->is_in_reserved(cur), "Should be in young gen"); |
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216 assert(CMSHeap::heap()->is_in_reserved(obj_to_push), "Should be in heap"); |
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217 if (should_be_partially_scanned(obj_to_push, cur)) { |
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218 assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned"); |
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219 obj_to_push = cur; |
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220 } |
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221 bool ok = queue->push(obj_to_push); |
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222 assert(ok, "Should have succeeded"); |
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223 } |
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224 assert(young_gen()->overflow_list() == NULL, "Error"); |
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225 return num_take_elems > 0; // was something transferred? |
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226 } |
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227 |
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228 void ParScanThreadState::push_on_overflow_stack(oop p) { |
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229 assert(ParGCUseLocalOverflow, "Else should not call"); |
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230 overflow_stack()->push(p); |
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231 assert(young_gen()->overflow_list() == NULL, "Error"); |
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232 } |
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233 |
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234 HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz) { |
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235 // If the object is small enough, try to reallocate the buffer. |
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236 HeapWord* obj = NULL; |
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237 if (!_to_space_full) { |
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238 PLAB* const plab = to_space_alloc_buffer(); |
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239 Space* const sp = to_space(); |
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240 if (word_sz * 100 < ParallelGCBufferWastePct * plab->word_sz()) { |
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241 // Is small enough; abandon this buffer and start a new one. |
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242 plab->retire(); |
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243 // The minimum size has to be twice SurvivorAlignmentInBytes to |
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244 // allow for padding used in the alignment of 1 word. A padding |
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245 // of 1 is too small for a filler word so the padding size will |
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246 // be increased by SurvivorAlignmentInBytes. |
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247 size_t min_usable_size = 2 * static_cast<size_t>(SurvivorAlignmentInBytes >> LogHeapWordSize); |
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248 size_t buf_size = MAX2(plab->word_sz(), min_usable_size); |
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249 HeapWord* buf_space = sp->par_allocate(buf_size); |
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250 if (buf_space == NULL) { |
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251 const size_t min_bytes = MAX2(PLAB::min_size(), min_usable_size) << LogHeapWordSize; |
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252 size_t free_bytes = sp->free(); |
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253 while(buf_space == NULL && free_bytes >= min_bytes) { |
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254 buf_size = free_bytes >> LogHeapWordSize; |
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255 assert(buf_size == (size_t)align_object_size(buf_size), "Invariant"); |
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256 buf_space = sp->par_allocate(buf_size); |
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257 free_bytes = sp->free(); |
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258 } |
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259 } |
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260 if (buf_space != NULL) { |
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261 plab->set_buf(buf_space, buf_size); |
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262 record_survivor_plab(buf_space, buf_size); |
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263 obj = plab->allocate_aligned(word_sz, SurvivorAlignmentInBytes); |
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264 // Note that we cannot compare buf_size < word_sz below |
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265 // because of AlignmentReserve (see PLAB::allocate()). |
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266 assert(obj != NULL || plab->words_remaining() < word_sz, |
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267 "Else should have been able to allocate requested object size " |
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268 SIZE_FORMAT ", PLAB size " SIZE_FORMAT ", SurvivorAlignmentInBytes " |
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269 SIZE_FORMAT ", words_remaining " SIZE_FORMAT, |
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270 word_sz, buf_size, SurvivorAlignmentInBytes, plab->words_remaining()); |
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271 // It's conceivable that we may be able to use the |
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272 // buffer we just grabbed for subsequent small requests |
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273 // even if not for this one. |
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274 } else { |
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275 // We're used up. |
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276 _to_space_full = true; |
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277 } |
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278 } else { |
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279 // Too large; allocate the object individually. |
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280 obj = sp->par_allocate(word_sz); |
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281 } |
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282 } |
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283 return obj; |
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284 } |
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285 |
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286 void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj, size_t word_sz) { |
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287 to_space_alloc_buffer()->undo_allocation(obj, word_sz); |
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288 } |
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289 |
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290 void ParScanThreadState::print_promotion_failure_size() { |
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291 if (_promotion_failed_info.has_failed()) { |
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292 log_trace(gc, promotion)(" (%d: promotion failure size = " SIZE_FORMAT ") ", |
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293 _thread_num, _promotion_failed_info.first_size()); |
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294 } |
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295 } |
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296 |
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297 class ParScanThreadStateSet: StackObj { |
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298 public: |
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299 // Initializes states for the specified number of threads; |
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300 ParScanThreadStateSet(int num_threads, |
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301 Space& to_space, |
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302 ParNewGeneration& young_gen, |
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303 Generation& old_gen, |
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304 ObjToScanQueueSet& queue_set, |
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305 Stack<oop, mtGC>* overflow_stacks_, |
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306 PreservedMarksSet& preserved_marks_set, |
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307 size_t desired_plab_sz, |
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308 TaskTerminator& term); |
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309 |
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310 ~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); } |
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311 |
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312 inline ParScanThreadState& thread_state(int i); |
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313 |
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314 void trace_promotion_failed(const YoungGCTracer* gc_tracer); |
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315 void reset(uint active_workers, bool promotion_failed); |
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316 void flush(); |
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317 |
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318 #if TASKQUEUE_STATS |
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319 static void |
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320 print_termination_stats_hdr(outputStream* const st); |
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321 void print_termination_stats(); |
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322 static void |
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323 print_taskqueue_stats_hdr(outputStream* const st); |
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324 void print_taskqueue_stats(); |
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325 void reset_stats(); |
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326 #endif // TASKQUEUE_STATS |
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327 |
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328 private: |
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329 TaskTerminator& _term; |
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330 ParNewGeneration& _young_gen; |
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331 Generation& _old_gen; |
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332 ParScanThreadState* _per_thread_states; |
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333 const int _num_threads; |
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334 public: |
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335 bool is_valid(int id) const { return id < _num_threads; } |
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336 ParallelTaskTerminator* terminator() { return _term.terminator(); } |
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337 }; |
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338 |
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339 ParScanThreadStateSet::ParScanThreadStateSet(int num_threads, |
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340 Space& to_space, |
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341 ParNewGeneration& young_gen, |
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342 Generation& old_gen, |
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343 ObjToScanQueueSet& queue_set, |
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344 Stack<oop, mtGC>* overflow_stacks, |
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345 PreservedMarksSet& preserved_marks_set, |
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346 size_t desired_plab_sz, |
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347 TaskTerminator& term) |
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348 : _term(term), |
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349 _young_gen(young_gen), |
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350 _old_gen(old_gen), |
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351 _per_thread_states(NEW_RESOURCE_ARRAY(ParScanThreadState, num_threads)), |
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352 _num_threads(num_threads) |
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353 { |
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354 assert(num_threads > 0, "sanity check!"); |
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355 assert(ParGCUseLocalOverflow == (overflow_stacks != NULL), |
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356 "overflow_stack allocation mismatch"); |
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357 // Initialize states. |
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358 for (int i = 0; i < num_threads; ++i) { |
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359 new(_per_thread_states + i) |
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360 ParScanThreadState(&to_space, &young_gen, &old_gen, i, &queue_set, |
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361 overflow_stacks, preserved_marks_set.get(i), |
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362 desired_plab_sz, term); |
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363 } |
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364 } |
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365 |
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366 inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i) { |
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367 assert(i >= 0 && i < _num_threads, "sanity check!"); |
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368 return _per_thread_states[i]; |
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369 } |
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370 |
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371 void ParScanThreadStateSet::trace_promotion_failed(const YoungGCTracer* gc_tracer) { |
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372 for (int i = 0; i < _num_threads; ++i) { |
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373 if (thread_state(i).promotion_failed()) { |
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374 gc_tracer->report_promotion_failed(thread_state(i).promotion_failed_info()); |
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375 thread_state(i).promotion_failed_info().reset(); |
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376 } |
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377 } |
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378 } |
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379 |
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380 void ParScanThreadStateSet::reset(uint active_threads, bool promotion_failed) { |
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381 _term.terminator()->reset_for_reuse(active_threads); |
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382 if (promotion_failed) { |
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383 for (int i = 0; i < _num_threads; ++i) { |
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384 thread_state(i).print_promotion_failure_size(); |
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385 } |
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386 } |
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387 } |
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388 |
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389 #if TASKQUEUE_STATS |
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390 void ParScanThreadState::reset_stats() { |
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391 taskqueue_stats().reset(); |
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392 _term_attempts = 0; |
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393 _overflow_refills = 0; |
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394 _overflow_refill_objs = 0; |
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395 } |
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396 |
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397 void ParScanThreadStateSet::reset_stats() { |
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398 for (int i = 0; i < _num_threads; ++i) { |
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399 thread_state(i).reset_stats(); |
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400 } |
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401 } |
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402 |
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403 void ParScanThreadStateSet::print_termination_stats_hdr(outputStream* const st) { |
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404 st->print_raw_cr("GC Termination Stats"); |
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405 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"); |
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406 st->print_raw_cr("thr ms ms % ms % attempts"); |
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407 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"); |
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408 } |
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409 |
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410 void ParScanThreadStateSet::print_termination_stats() { |
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411 Log(gc, task, stats) log; |
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412 if (!log.is_debug()) { |
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413 return; |
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414 } |
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415 |
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416 ResourceMark rm; |
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417 LogStream ls(log.debug()); |
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418 outputStream* st = &ls; |
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419 |
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420 print_termination_stats_hdr(st); |
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421 |
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422 for (int i = 0; i < _num_threads; ++i) { |
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423 const ParScanThreadState & pss = thread_state(i); |
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424 const double elapsed_ms = pss.elapsed_time() * 1000.0; |
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425 const double s_roots_ms = pss.strong_roots_time() * 1000.0; |
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426 const double term_ms = pss.term_time() * 1000.0; |
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427 st->print_cr("%3d %9.2f %9.2f %6.2f %9.2f %6.2f " SIZE_FORMAT_W(8), |
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428 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, |
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429 term_ms, term_ms * 100 / elapsed_ms, pss.term_attempts()); |
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430 } |
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431 } |
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432 |
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433 // Print stats related to work queue activity. |
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434 void ParScanThreadStateSet::print_taskqueue_stats_hdr(outputStream* const st) { |
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435 st->print_raw_cr("GC Task Stats"); |
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436 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); |
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437 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); |
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438 } |
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439 |
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440 void ParScanThreadStateSet::print_taskqueue_stats() { |
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441 if (!log_is_enabled(Trace, gc, task, stats)) { |
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442 return; |
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443 } |
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444 Log(gc, task, stats) log; |
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445 ResourceMark rm; |
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446 LogStream ls(log.trace()); |
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447 outputStream* st = &ls; |
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448 print_taskqueue_stats_hdr(st); |
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449 |
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450 TaskQueueStats totals; |
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451 for (int i = 0; i < _num_threads; ++i) { |
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452 const ParScanThreadState & pss = thread_state(i); |
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453 const TaskQueueStats & stats = pss.taskqueue_stats(); |
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454 st->print("%3d ", i); stats.print(st); st->cr(); |
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455 totals += stats; |
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456 |
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457 if (pss.overflow_refills() > 0) { |
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458 st->print_cr(" " SIZE_FORMAT_W(10) " overflow refills " |
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459 SIZE_FORMAT_W(10) " overflow objects", |
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460 pss.overflow_refills(), pss.overflow_refill_objs()); |
|
461 } |
|
462 } |
|
463 st->print("tot "); totals.print(st); st->cr(); |
|
464 |
|
465 DEBUG_ONLY(totals.verify()); |
|
466 } |
|
467 #endif // TASKQUEUE_STATS |
|
468 |
|
469 void ParScanThreadStateSet::flush() { |
|
470 // Work in this loop should be kept as lightweight as |
|
471 // possible since this might otherwise become a bottleneck |
|
472 // to scaling. Should we add heavy-weight work into this |
|
473 // loop, consider parallelizing the loop into the worker threads. |
|
474 for (int i = 0; i < _num_threads; ++i) { |
|
475 ParScanThreadState& par_scan_state = thread_state(i); |
|
476 |
|
477 // Flush stats related to To-space PLAB activity and |
|
478 // retire the last buffer. |
|
479 par_scan_state.to_space_alloc_buffer()->flush_and_retire_stats(_young_gen.plab_stats()); |
|
480 |
|
481 // Every thread has its own age table. We need to merge |
|
482 // them all into one. |
|
483 AgeTable *local_table = par_scan_state.age_table(); |
|
484 _young_gen.age_table()->merge(local_table); |
|
485 |
|
486 // Inform old gen that we're done. |
|
487 _old_gen.par_promote_alloc_done(i); |
|
488 } |
|
489 |
|
490 if (UseConcMarkSweepGC) { |
|
491 // We need to call this even when ResizeOldPLAB is disabled |
|
492 // so as to avoid breaking some asserts. While we may be able |
|
493 // to avoid this by reorganizing the code a bit, I am loathe |
|
494 // to do that unless we find cases where ergo leads to bad |
|
495 // performance. |
|
496 CompactibleFreeListSpaceLAB::compute_desired_plab_size(); |
|
497 } |
|
498 } |
|
499 |
|
500 ParScanClosure::ParScanClosure(ParNewGeneration* g, |
|
501 ParScanThreadState* par_scan_state) : |
|
502 OopsInClassLoaderDataOrGenClosure(g), _par_scan_state(par_scan_state), _g(g) { |
|
503 _boundary = _g->reserved().end(); |
|
504 } |
|
505 |
|
506 void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, true); } |
|
507 void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); } |
|
508 |
|
509 void ParRootScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, true); } |
|
510 void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); } |
|
511 |
|
512 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g, |
|
513 ParScanThreadState* par_scan_state) |
|
514 : ScanWeakRefClosure(g), _par_scan_state(par_scan_state) |
|
515 {} |
|
516 |
|
517 #ifdef WIN32 |
|
518 #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */ |
|
519 #endif |
|
520 |
|
521 ParEvacuateFollowersClosure::ParEvacuateFollowersClosure( |
|
522 ParScanThreadState* par_scan_state_, |
|
523 ParScanWithoutBarrierClosure* to_space_closure_, |
|
524 ParScanWithBarrierClosure* old_gen_closure_, |
|
525 ParRootScanWithoutBarrierClosure* to_space_root_closure_, |
|
526 ParNewGeneration* par_gen_, |
|
527 ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_, |
|
528 ObjToScanQueueSet* task_queues_, |
|
529 ParallelTaskTerminator* terminator_) : |
|
530 |
|
531 _par_scan_state(par_scan_state_), |
|
532 _to_space_closure(to_space_closure_), |
|
533 _to_space_root_closure(to_space_root_closure_), |
|
534 _old_gen_closure(old_gen_closure_), |
|
535 _old_gen_root_closure(old_gen_root_closure_), |
|
536 _par_gen(par_gen_), |
|
537 _task_queues(task_queues_), |
|
538 _terminator(terminator_) |
|
539 {} |
|
540 |
|
541 void ParEvacuateFollowersClosure::do_void() { |
|
542 ObjToScanQueue* work_q = par_scan_state()->work_queue(); |
|
543 |
|
544 while (true) { |
|
545 // Scan to-space and old-gen objs until we run out of both. |
|
546 oop obj_to_scan; |
|
547 par_scan_state()->trim_queues(0); |
|
548 |
|
549 // We have no local work, attempt to steal from other threads. |
|
550 |
|
551 // Attempt to steal work from promoted. |
|
552 if (task_queues()->steal(par_scan_state()->thread_num(), |
|
553 obj_to_scan)) { |
|
554 bool res = work_q->push(obj_to_scan); |
|
555 assert(res, "Empty queue should have room for a push."); |
|
556 |
|
557 // If successful, goto Start. |
|
558 continue; |
|
559 |
|
560 // Try global overflow list. |
|
561 } else if (par_gen()->take_from_overflow_list(par_scan_state())) { |
|
562 continue; |
|
563 } |
|
564 |
|
565 // Otherwise, offer termination. |
|
566 par_scan_state()->start_term_time(); |
|
567 if (terminator()->offer_termination()) break; |
|
568 par_scan_state()->end_term_time(); |
|
569 } |
|
570 assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0, |
|
571 "Broken overflow list?"); |
|
572 // Finish the last termination pause. |
|
573 par_scan_state()->end_term_time(); |
|
574 } |
|
575 |
|
576 ParNewGenTask::ParNewGenTask(ParNewGeneration* young_gen, |
|
577 Generation* old_gen, |
|
578 HeapWord* young_old_boundary, |
|
579 ParScanThreadStateSet* state_set, |
|
580 StrongRootsScope* strong_roots_scope) : |
|
581 AbstractGangTask("ParNewGeneration collection"), |
|
582 _young_gen(young_gen), _old_gen(old_gen), |
|
583 _young_old_boundary(young_old_boundary), |
|
584 _state_set(state_set), |
|
585 _strong_roots_scope(strong_roots_scope) |
|
586 {} |
|
587 |
|
588 void ParNewGenTask::work(uint worker_id) { |
|
589 CMSHeap* heap = CMSHeap::heap(); |
|
590 // Since this is being done in a separate thread, need new resource |
|
591 // and handle marks. |
|
592 ResourceMark rm; |
|
593 HandleMark hm; |
|
594 |
|
595 ParScanThreadState& par_scan_state = _state_set->thread_state(worker_id); |
|
596 assert(_state_set->is_valid(worker_id), "Should not have been called"); |
|
597 |
|
598 par_scan_state.set_young_old_boundary(_young_old_boundary); |
|
599 |
|
600 CLDScanClosure cld_scan_closure(&par_scan_state.to_space_root_closure(), |
|
601 heap->rem_set()->cld_rem_set()->accumulate_modified_oops()); |
|
602 |
|
603 par_scan_state.start_strong_roots(); |
|
604 heap->young_process_roots(_strong_roots_scope, |
|
605 &par_scan_state.to_space_root_closure(), |
|
606 &par_scan_state.older_gen_closure(), |
|
607 &cld_scan_closure); |
|
608 |
|
609 par_scan_state.end_strong_roots(); |
|
610 |
|
611 // "evacuate followers". |
|
612 par_scan_state.evacuate_followers_closure().do_void(); |
|
613 |
|
614 // This will collapse this worker's promoted object list that's |
|
615 // created during the main ParNew parallel phase of ParNew. This has |
|
616 // to be called after all workers have finished promoting objects |
|
617 // and scanning promoted objects. It should be safe calling it from |
|
618 // here, given that we can only reach here after all thread have |
|
619 // offered termination, i.e., after there is no more work to be |
|
620 // done. It will also disable promotion tracking for the rest of |
|
621 // this GC as it's not necessary to be on during reference processing. |
|
622 _old_gen->par_oop_since_save_marks_iterate_done((int) worker_id); |
|
623 } |
|
624 |
|
625 ParNewGeneration::ParNewGeneration(ReservedSpace rs, |
|
626 size_t initial_byte_size, |
|
627 size_t min_byte_size, |
|
628 size_t max_byte_size) |
|
629 : DefNewGeneration(rs, initial_byte_size, min_byte_size, max_byte_size, "CMS young collection pauses"), |
|
630 _plab_stats("Young", YoungPLABSize, PLABWeight), |
|
631 _overflow_list(NULL), |
|
632 _is_alive_closure(this) |
|
633 { |
|
634 NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;) |
|
635 NOT_PRODUCT(_num_par_pushes = 0;) |
|
636 _task_queues = new ObjToScanQueueSet(ParallelGCThreads); |
|
637 guarantee(_task_queues != NULL, "task_queues allocation failure."); |
|
638 |
|
639 for (uint i = 0; i < ParallelGCThreads; i++) { |
|
640 ObjToScanQueue *q = new ObjToScanQueue(); |
|
641 guarantee(q != NULL, "work_queue Allocation failure."); |
|
642 _task_queues->register_queue(i, q); |
|
643 } |
|
644 |
|
645 for (uint i = 0; i < ParallelGCThreads; i++) { |
|
646 _task_queues->queue(i)->initialize(); |
|
647 } |
|
648 |
|
649 _overflow_stacks = NULL; |
|
650 if (ParGCUseLocalOverflow) { |
|
651 // typedef to workaround NEW_C_HEAP_ARRAY macro, which can not deal with ',' |
|
652 typedef Stack<oop, mtGC> GCOopStack; |
|
653 |
|
654 _overflow_stacks = NEW_C_HEAP_ARRAY(GCOopStack, ParallelGCThreads, mtGC); |
|
655 for (size_t i = 0; i < ParallelGCThreads; ++i) { |
|
656 new (_overflow_stacks + i) Stack<oop, mtGC>(); |
|
657 } |
|
658 } |
|
659 |
|
660 if (UsePerfData) { |
|
661 EXCEPTION_MARK; |
|
662 ResourceMark rm; |
|
663 |
|
664 const char* cname = |
|
665 PerfDataManager::counter_name(_gen_counters->name_space(), "threads"); |
|
666 PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None, |
|
667 ParallelGCThreads, CHECK); |
|
668 } |
|
669 } |
|
670 |
|
671 // ParNewGeneration:: |
|
672 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) : |
|
673 DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {} |
|
674 |
|
675 template <class T> |
|
676 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) { |
|
677 #ifdef ASSERT |
|
678 { |
|
679 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p); |
|
680 // We never expect to see a null reference being processed |
|
681 // as a weak reference. |
|
682 assert(oopDesc::is_oop(obj), "expected an oop while scanning weak refs"); |
|
683 } |
|
684 #endif // ASSERT |
|
685 |
|
686 Devirtualizer::do_oop_no_verify(_par_cl, p); |
|
687 |
|
688 if (CMSHeap::heap()->is_in_reserved(p)) { |
|
689 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);; |
|
690 _rs->write_ref_field_gc_par(p, obj); |
|
691 } |
|
692 } |
|
693 |
|
694 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p) { ParKeepAliveClosure::do_oop_work(p); } |
|
695 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); } |
|
696 |
|
697 // ParNewGeneration:: |
|
698 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) : |
|
699 DefNewGeneration::KeepAliveClosure(cl) {} |
|
700 |
|
701 template <class T> |
|
702 void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) { |
|
703 #ifdef ASSERT |
|
704 { |
|
705 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p); |
|
706 // We never expect to see a null reference being processed |
|
707 // as a weak reference. |
|
708 assert(oopDesc::is_oop(obj), "expected an oop while scanning weak refs"); |
|
709 } |
|
710 #endif // ASSERT |
|
711 |
|
712 Devirtualizer::do_oop_no_verify(_cl, p); |
|
713 |
|
714 if (CMSHeap::heap()->is_in_reserved(p)) { |
|
715 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p); |
|
716 _rs->write_ref_field_gc_par(p, obj); |
|
717 } |
|
718 } |
|
719 |
|
720 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p) { KeepAliveClosure::do_oop_work(p); } |
|
721 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); } |
|
722 |
|
723 template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) { |
|
724 T heap_oop = RawAccess<>::oop_load(p); |
|
725 if (!CompressedOops::is_null(heap_oop)) { |
|
726 oop obj = CompressedOops::decode_not_null(heap_oop); |
|
727 if ((HeapWord*)obj < _boundary) { |
|
728 assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?"); |
|
729 oop new_obj = obj->is_forwarded() |
|
730 ? obj->forwardee() |
|
731 : _g->DefNewGeneration::copy_to_survivor_space(obj); |
|
732 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj); |
|
733 } |
|
734 if (_gc_barrier) { |
|
735 // If p points to a younger generation, mark the card. |
|
736 if ((HeapWord*)obj < _gen_boundary) { |
|
737 _rs->write_ref_field_gc_par(p, obj); |
|
738 } |
|
739 } |
|
740 } |
|
741 } |
|
742 |
|
743 void ScanClosureWithParBarrier::do_oop(oop* p) { ScanClosureWithParBarrier::do_oop_work(p); } |
|
744 void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); } |
|
745 |
|
746 class ParNewRefProcTaskProxy: public AbstractGangTask { |
|
747 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; |
|
748 public: |
|
749 ParNewRefProcTaskProxy(ProcessTask& task, |
|
750 ParNewGeneration& young_gen, |
|
751 Generation& old_gen, |
|
752 HeapWord* young_old_boundary, |
|
753 ParScanThreadStateSet& state_set); |
|
754 |
|
755 private: |
|
756 virtual void work(uint worker_id); |
|
757 private: |
|
758 ParNewGeneration& _young_gen; |
|
759 ProcessTask& _task; |
|
760 Generation& _old_gen; |
|
761 HeapWord* _young_old_boundary; |
|
762 ParScanThreadStateSet& _state_set; |
|
763 }; |
|
764 |
|
765 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy(ProcessTask& task, |
|
766 ParNewGeneration& young_gen, |
|
767 Generation& old_gen, |
|
768 HeapWord* young_old_boundary, |
|
769 ParScanThreadStateSet& state_set) |
|
770 : AbstractGangTask("ParNewGeneration parallel reference processing"), |
|
771 _young_gen(young_gen), |
|
772 _task(task), |
|
773 _old_gen(old_gen), |
|
774 _young_old_boundary(young_old_boundary), |
|
775 _state_set(state_set) |
|
776 { } |
|
777 |
|
778 void ParNewRefProcTaskProxy::work(uint worker_id) { |
|
779 ResourceMark rm; |
|
780 HandleMark hm; |
|
781 ParScanThreadState& par_scan_state = _state_set.thread_state(worker_id); |
|
782 par_scan_state.set_young_old_boundary(_young_old_boundary); |
|
783 _task.work(worker_id, par_scan_state.is_alive_closure(), |
|
784 par_scan_state.keep_alive_closure(), |
|
785 par_scan_state.evacuate_followers_closure()); |
|
786 } |
|
787 |
|
788 void ParNewRefProcTaskExecutor::execute(ProcessTask& task, uint ergo_workers) { |
|
789 CMSHeap* gch = CMSHeap::heap(); |
|
790 WorkGang* workers = gch->workers(); |
|
791 assert(workers != NULL, "Need parallel worker threads."); |
|
792 assert(workers->active_workers() == ergo_workers, |
|
793 "Ergonomically chosen workers (%u) must be equal to active workers (%u)", |
|
794 ergo_workers, workers->active_workers()); |
|
795 _state_set.reset(workers->active_workers(), _young_gen.promotion_failed()); |
|
796 ParNewRefProcTaskProxy rp_task(task, _young_gen, _old_gen, |
|
797 _young_gen.reserved().end(), _state_set); |
|
798 workers->run_task(&rp_task, workers->active_workers()); |
|
799 _state_set.reset(0 /* bad value in debug if not reset */, |
|
800 _young_gen.promotion_failed()); |
|
801 } |
|
802 |
|
803 void ParNewRefProcTaskExecutor::set_single_threaded_mode() { |
|
804 _state_set.flush(); |
|
805 CMSHeap* heap = CMSHeap::heap(); |
|
806 heap->save_marks(); |
|
807 } |
|
808 |
|
809 ScanClosureWithParBarrier:: |
|
810 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) : |
|
811 OopsInClassLoaderDataOrGenClosure(g), _g(g), _boundary(g->reserved().end()), _gc_barrier(gc_barrier) |
|
812 { } |
|
813 |
|
814 template <typename OopClosureType1, typename OopClosureType2> |
|
815 EvacuateFollowersClosureGeneral<OopClosureType1, OopClosureType2>:: |
|
816 EvacuateFollowersClosureGeneral(CMSHeap* heap, |
|
817 OopClosureType1* cur, |
|
818 OopClosureType2* older) : |
|
819 _heap(heap), |
|
820 _scan_cur_or_nonheap(cur), _scan_older(older) |
|
821 { } |
|
822 |
|
823 template <typename OopClosureType1, typename OopClosureType2> |
|
824 void EvacuateFollowersClosureGeneral<OopClosureType1, OopClosureType2>::do_void() { |
|
825 do { |
|
826 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, |
|
827 _scan_older); |
|
828 } while (!_heap->no_allocs_since_save_marks()); |
|
829 } |
|
830 |
|
831 // A Generation that does parallel young-gen collection. |
|
832 |
|
833 void ParNewGeneration::handle_promotion_failed(CMSHeap* gch, ParScanThreadStateSet& thread_state_set) { |
|
834 assert(_promo_failure_scan_stack.is_empty(), "post condition"); |
|
835 _promo_failure_scan_stack.clear(true); // Clear cached segments. |
|
836 |
|
837 remove_forwarding_pointers(); |
|
838 log_info(gc, promotion)("Promotion failed"); |
|
839 // All the spaces are in play for mark-sweep. |
|
840 swap_spaces(); // Make life simpler for CMS || rescan; see 6483690. |
|
841 from()->set_next_compaction_space(to()); |
|
842 gch->set_incremental_collection_failed(); |
|
843 // Inform the next generation that a promotion failure occurred. |
|
844 _old_gen->promotion_failure_occurred(); |
|
845 |
|
846 // Trace promotion failure in the parallel GC threads |
|
847 thread_state_set.trace_promotion_failed(gc_tracer()); |
|
848 // Single threaded code may have reported promotion failure to the global state |
|
849 if (_promotion_failed_info.has_failed()) { |
|
850 _gc_tracer.report_promotion_failed(_promotion_failed_info); |
|
851 } |
|
852 // Reset the PromotionFailureALot counters. |
|
853 NOT_PRODUCT(gch->reset_promotion_should_fail();) |
|
854 } |
|
855 |
|
856 void ParNewGeneration::collect(bool full, |
|
857 bool clear_all_soft_refs, |
|
858 size_t size, |
|
859 bool is_tlab) { |
|
860 assert(full || size > 0, "otherwise we don't want to collect"); |
|
861 |
|
862 CMSHeap* gch = CMSHeap::heap(); |
|
863 |
|
864 _gc_timer->register_gc_start(); |
|
865 |
|
866 AdaptiveSizePolicy* size_policy = gch->size_policy(); |
|
867 WorkGang* workers = gch->workers(); |
|
868 assert(workers != NULL, "Need workgang for parallel work"); |
|
869 uint active_workers = |
|
870 WorkerPolicy::calc_active_workers(workers->total_workers(), |
|
871 workers->active_workers(), |
|
872 Threads::number_of_non_daemon_threads()); |
|
873 active_workers = workers->update_active_workers(active_workers); |
|
874 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers->total_workers()); |
|
875 |
|
876 _old_gen = gch->old_gen(); |
|
877 |
|
878 // If the next generation is too full to accommodate worst-case promotion |
|
879 // from this generation, pass on collection; let the next generation |
|
880 // do it. |
|
881 if (!collection_attempt_is_safe()) { |
|
882 gch->set_incremental_collection_failed(); // slight lie, in that we did not even attempt one |
|
883 return; |
|
884 } |
|
885 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); |
|
886 |
|
887 _gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); |
|
888 gch->trace_heap_before_gc(gc_tracer()); |
|
889 |
|
890 init_assuming_no_promotion_failure(); |
|
891 |
|
892 GCTraceTime(Trace, gc, phases) t1("ParNew", NULL, gch->gc_cause()); |
|
893 |
|
894 age_table()->clear(); |
|
895 to()->clear(SpaceDecorator::Mangle); |
|
896 |
|
897 gch->save_marks(); |
|
898 |
|
899 // Set the correct parallelism (number of queues) in the reference processor |
|
900 ref_processor()->set_active_mt_degree(active_workers); |
|
901 |
|
902 // Need to initialize the preserved marks before the ThreadStateSet c'tor. |
|
903 _preserved_marks_set.init(active_workers); |
|
904 |
|
905 // Always set the terminator for the active number of workers |
|
906 // because only those workers go through the termination protocol. |
|
907 TaskTerminator _term(active_workers, task_queues()); |
|
908 ParScanThreadStateSet thread_state_set(active_workers, |
|
909 *to(), *this, *_old_gen, *task_queues(), |
|
910 _overflow_stacks, _preserved_marks_set, |
|
911 desired_plab_sz(), _term); |
|
912 |
|
913 thread_state_set.reset(active_workers, promotion_failed()); |
|
914 |
|
915 { |
|
916 StrongRootsScope srs(active_workers); |
|
917 |
|
918 ParNewGenTask tsk(this, _old_gen, reserved().end(), &thread_state_set, &srs); |
|
919 gch->rem_set()->prepare_for_younger_refs_iterate(true); |
|
920 // It turns out that even when we're using 1 thread, doing the work in a |
|
921 // separate thread causes wide variance in run times. We can't help this |
|
922 // in the multi-threaded case, but we special-case n=1 here to get |
|
923 // repeatable measurements of the 1-thread overhead of the parallel code. |
|
924 // Might multiple workers ever be used? If yes, initialization |
|
925 // has been done such that the single threaded path should not be used. |
|
926 if (workers->total_workers() > 1) { |
|
927 workers->run_task(&tsk); |
|
928 } else { |
|
929 tsk.work(0); |
|
930 } |
|
931 } |
|
932 |
|
933 thread_state_set.reset(0 /* Bad value in debug if not reset */, |
|
934 promotion_failed()); |
|
935 |
|
936 // Trace and reset failed promotion info. |
|
937 if (promotion_failed()) { |
|
938 thread_state_set.trace_promotion_failed(gc_tracer()); |
|
939 } |
|
940 |
|
941 // Process (weak) reference objects found during scavenge. |
|
942 ReferenceProcessor* rp = ref_processor(); |
|
943 IsAliveClosure is_alive(this); |
|
944 ScanWeakRefClosure scan_weak_ref(this); |
|
945 KeepAliveClosure keep_alive(&scan_weak_ref); |
|
946 ScanClosure scan_without_gc_barrier(this, false); |
|
947 ScanClosureWithParBarrier scan_with_gc_barrier(this, true); |
|
948 set_promo_failure_scan_stack_closure(&scan_without_gc_barrier); |
|
949 EvacuateFollowersClosureGeneral<ScanClosure, ScanClosureWithParBarrier> evacuate_followers( |
|
950 gch, &scan_without_gc_barrier, &scan_with_gc_barrier); |
|
951 rp->setup_policy(clear_all_soft_refs); |
|
952 // Can the mt_degree be set later (at run_task() time would be best)? |
|
953 rp->set_active_mt_degree(active_workers); |
|
954 ReferenceProcessorStats stats; |
|
955 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues()); |
|
956 if (rp->processing_is_mt()) { |
|
957 ParNewRefProcTaskExecutor task_executor(*this, *_old_gen, thread_state_set); |
|
958 stats = rp->process_discovered_references(&is_alive, &keep_alive, |
|
959 &evacuate_followers, &task_executor, |
|
960 &pt); |
|
961 } else { |
|
962 thread_state_set.flush(); |
|
963 gch->save_marks(); |
|
964 stats = rp->process_discovered_references(&is_alive, &keep_alive, |
|
965 &evacuate_followers, NULL, |
|
966 &pt); |
|
967 } |
|
968 _gc_tracer.report_gc_reference_stats(stats); |
|
969 _gc_tracer.report_tenuring_threshold(tenuring_threshold()); |
|
970 pt.print_all_references(); |
|
971 |
|
972 assert(gch->no_allocs_since_save_marks(), "evacuation should be done at this point"); |
|
973 |
|
974 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); |
|
975 |
|
976 // Verify that the usage of keep_alive only forwarded |
|
977 // the oops and did not find anything new to copy. |
|
978 assert(gch->no_allocs_since_save_marks(), "unexpectedly copied objects"); |
|
979 |
|
980 if (!promotion_failed()) { |
|
981 // Swap the survivor spaces. |
|
982 eden()->clear(SpaceDecorator::Mangle); |
|
983 from()->clear(SpaceDecorator::Mangle); |
|
984 if (ZapUnusedHeapArea) { |
|
985 // This is now done here because of the piece-meal mangling which |
|
986 // can check for valid mangling at intermediate points in the |
|
987 // collection(s). When a young collection fails to collect |
|
988 // sufficient space resizing of the young generation can occur |
|
989 // and redistribute the spaces in the young generation. Mangle |
|
990 // here so that unzapped regions don't get distributed to |
|
991 // other spaces. |
|
992 to()->mangle_unused_area(); |
|
993 } |
|
994 swap_spaces(); |
|
995 |
|
996 // A successful scavenge should restart the GC time limit count which is |
|
997 // for full GC's. |
|
998 size_policy->reset_gc_overhead_limit_count(); |
|
999 |
|
1000 assert(to()->is_empty(), "to space should be empty now"); |
|
1001 |
|
1002 adjust_desired_tenuring_threshold(); |
|
1003 } else { |
|
1004 handle_promotion_failed(gch, thread_state_set); |
|
1005 } |
|
1006 _preserved_marks_set.reclaim(); |
|
1007 // set new iteration safe limit for the survivor spaces |
|
1008 from()->set_concurrent_iteration_safe_limit(from()->top()); |
|
1009 to()->set_concurrent_iteration_safe_limit(to()->top()); |
|
1010 |
|
1011 plab_stats()->adjust_desired_plab_sz(); |
|
1012 |
|
1013 TASKQUEUE_STATS_ONLY(thread_state_set.print_termination_stats()); |
|
1014 TASKQUEUE_STATS_ONLY(thread_state_set.print_taskqueue_stats()); |
|
1015 |
|
1016 // We need to use a monotonically non-decreasing time in ms |
|
1017 // or we will see time-warp warnings and os::javaTimeMillis() |
|
1018 // does not guarantee monotonicity. |
|
1019 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; |
|
1020 update_time_of_last_gc(now); |
|
1021 |
|
1022 rp->set_enqueuing_is_done(true); |
|
1023 rp->verify_no_references_recorded(); |
|
1024 |
|
1025 gch->trace_heap_after_gc(gc_tracer()); |
|
1026 |
|
1027 _gc_timer->register_gc_end(); |
|
1028 |
|
1029 _gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); |
|
1030 } |
|
1031 |
|
1032 size_t ParNewGeneration::desired_plab_sz() { |
|
1033 return _plab_stats.desired_plab_sz(CMSHeap::heap()->workers()->active_workers()); |
|
1034 } |
|
1035 |
|
1036 static int sum; |
|
1037 void ParNewGeneration::waste_some_time() { |
|
1038 for (int i = 0; i < 100; i++) { |
|
1039 sum += i; |
|
1040 } |
|
1041 } |
|
1042 |
|
1043 static const oop ClaimedForwardPtr = cast_to_oop<intptr_t>(0x4); |
|
1044 |
|
1045 // Because of concurrency, there are times where an object for which |
|
1046 // "is_forwarded()" is true contains an "interim" forwarding pointer |
|
1047 // value. Such a value will soon be overwritten with a real value. |
|
1048 // This method requires "obj" to have a forwarding pointer, and waits, if |
|
1049 // necessary for a real one to be inserted, and returns it. |
|
1050 |
|
1051 oop ParNewGeneration::real_forwardee(oop obj) { |
|
1052 oop forward_ptr = obj->forwardee(); |
|
1053 if (forward_ptr != ClaimedForwardPtr) { |
|
1054 return forward_ptr; |
|
1055 } else { |
|
1056 return real_forwardee_slow(obj); |
|
1057 } |
|
1058 } |
|
1059 |
|
1060 oop ParNewGeneration::real_forwardee_slow(oop obj) { |
|
1061 // Spin-read if it is claimed but not yet written by another thread. |
|
1062 oop forward_ptr = obj->forwardee(); |
|
1063 while (forward_ptr == ClaimedForwardPtr) { |
|
1064 waste_some_time(); |
|
1065 assert(obj->is_forwarded(), "precondition"); |
|
1066 forward_ptr = obj->forwardee(); |
|
1067 } |
|
1068 return forward_ptr; |
|
1069 } |
|
1070 |
|
1071 // Multiple GC threads may try to promote an object. If the object |
|
1072 // is successfully promoted, a forwarding pointer will be installed in |
|
1073 // the object in the young generation. This method claims the right |
|
1074 // to install the forwarding pointer before it copies the object, |
|
1075 // thus avoiding the need to undo the copy as in |
|
1076 // copy_to_survivor_space_avoiding_with_undo. |
|
1077 |
|
1078 oop ParNewGeneration::copy_to_survivor_space(ParScanThreadState* par_scan_state, |
|
1079 oop old, |
|
1080 size_t sz, |
|
1081 markWord m) { |
|
1082 // In the sequential version, this assert also says that the object is |
|
1083 // not forwarded. That might not be the case here. It is the case that |
|
1084 // the caller observed it to be not forwarded at some time in the past. |
|
1085 assert(is_in_reserved(old), "shouldn't be scavenging this oop"); |
|
1086 |
|
1087 // The sequential code read "old->age()" below. That doesn't work here, |
|
1088 // since the age is in the mark word, and that might be overwritten with |
|
1089 // a forwarding pointer by a parallel thread. So we must save the mark |
|
1090 // word in a local and then analyze it. |
|
1091 oopDesc dummyOld; |
|
1092 dummyOld.set_mark_raw(m); |
|
1093 assert(!dummyOld.is_forwarded(), |
|
1094 "should not be called with forwarding pointer mark word."); |
|
1095 |
|
1096 oop new_obj = NULL; |
|
1097 oop forward_ptr; |
|
1098 |
|
1099 // Try allocating obj in to-space (unless too old) |
|
1100 if (dummyOld.age() < tenuring_threshold()) { |
|
1101 new_obj = (oop)par_scan_state->alloc_in_to_space(sz); |
|
1102 } |
|
1103 |
|
1104 if (new_obj == NULL) { |
|
1105 // Either to-space is full or we decided to promote try allocating obj tenured |
|
1106 |
|
1107 // Attempt to install a null forwarding pointer (atomically), |
|
1108 // to claim the right to install the real forwarding pointer. |
|
1109 forward_ptr = old->forward_to_atomic(ClaimedForwardPtr, m); |
|
1110 if (forward_ptr != NULL) { |
|
1111 // someone else beat us to it. |
|
1112 return real_forwardee(old); |
|
1113 } |
|
1114 |
|
1115 if (!_promotion_failed) { |
|
1116 new_obj = _old_gen->par_promote(par_scan_state->thread_num(), |
|
1117 old, m, sz); |
|
1118 } |
|
1119 |
|
1120 if (new_obj == NULL) { |
|
1121 // promotion failed, forward to self |
|
1122 _promotion_failed = true; |
|
1123 new_obj = old; |
|
1124 |
|
1125 par_scan_state->preserved_marks()->push_if_necessary(old, m); |
|
1126 par_scan_state->register_promotion_failure(sz); |
|
1127 } |
|
1128 |
|
1129 old->forward_to(new_obj); |
|
1130 forward_ptr = NULL; |
|
1131 } else { |
|
1132 // Is in to-space; do copying ourselves. |
|
1133 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); |
|
1134 assert(CMSHeap::heap()->is_in_reserved(new_obj), "illegal forwarding pointer value."); |
|
1135 forward_ptr = old->forward_to_atomic(new_obj, m); |
|
1136 // Restore the mark word copied above. |
|
1137 new_obj->set_mark_raw(m); |
|
1138 // Increment age if obj still in new generation |
|
1139 new_obj->incr_age(); |
|
1140 par_scan_state->age_table()->add(new_obj, sz); |
|
1141 } |
|
1142 assert(new_obj != NULL, "just checking"); |
|
1143 |
|
1144 // This code must come after the CAS test, or it will print incorrect |
|
1145 // information. |
|
1146 log_develop_trace(gc, scavenge)("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}", |
|
1147 is_in_reserved(new_obj) ? "copying" : "tenuring", |
|
1148 new_obj->klass()->internal_name(), p2i(old), p2i(new_obj), new_obj->size()); |
|
1149 |
|
1150 if (forward_ptr == NULL) { |
|
1151 oop obj_to_push = new_obj; |
|
1152 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { |
|
1153 // Length field used as index of next element to be scanned. |
|
1154 // Real length can be obtained from real_forwardee() |
|
1155 arrayOop(old)->set_length(0); |
|
1156 obj_to_push = old; |
|
1157 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, |
|
1158 "push forwarded object"); |
|
1159 } |
|
1160 // Push it on one of the queues of to-be-scanned objects. |
|
1161 bool simulate_overflow = false; |
|
1162 NOT_PRODUCT( |
|
1163 if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) { |
|
1164 // simulate a stack overflow |
|
1165 simulate_overflow = true; |
|
1166 } |
|
1167 ) |
|
1168 if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) { |
|
1169 // Add stats for overflow pushes. |
|
1170 log_develop_trace(gc)("Queue Overflow"); |
|
1171 push_on_overflow_list(old, par_scan_state); |
|
1172 TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0)); |
|
1173 } |
|
1174 |
|
1175 return new_obj; |
|
1176 } |
|
1177 |
|
1178 // Oops. Someone beat us to it. Undo the allocation. Where did we |
|
1179 // allocate it? |
|
1180 if (is_in_reserved(new_obj)) { |
|
1181 // Must be in to_space. |
|
1182 assert(to()->is_in_reserved(new_obj), "Checking"); |
|
1183 if (forward_ptr == ClaimedForwardPtr) { |
|
1184 // Wait to get the real forwarding pointer value. |
|
1185 forward_ptr = real_forwardee(old); |
|
1186 } |
|
1187 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); |
|
1188 } |
|
1189 |
|
1190 return forward_ptr; |
|
1191 } |
|
1192 |
|
1193 #ifndef PRODUCT |
|
1194 // It's OK to call this multi-threaded; the worst thing |
|
1195 // that can happen is that we'll get a bunch of closely |
|
1196 // spaced simulated overflows, but that's OK, in fact |
|
1197 // probably good as it would exercise the overflow code |
|
1198 // under contention. |
|
1199 bool ParNewGeneration::should_simulate_overflow() { |
|
1200 if (_overflow_counter-- <= 0) { // just being defensive |
|
1201 _overflow_counter = ParGCWorkQueueOverflowInterval; |
|
1202 return true; |
|
1203 } else { |
|
1204 return false; |
|
1205 } |
|
1206 } |
|
1207 #endif |
|
1208 |
|
1209 // In case we are using compressed oops, we need to be careful. |
|
1210 // If the object being pushed is an object array, then its length |
|
1211 // field keeps track of the "grey boundary" at which the next |
|
1212 // incremental scan will be done (see ParGCArrayScanChunk). |
|
1213 // When using compressed oops, this length field is kept in the |
|
1214 // lower 32 bits of the erstwhile klass word and cannot be used |
|
1215 // for the overflow chaining pointer (OCP below). As such the OCP |
|
1216 // would itself need to be compressed into the top 32-bits in this |
|
1217 // case. Unfortunately, see below, in the event that we have a |
|
1218 // promotion failure, the node to be pushed on the list can be |
|
1219 // outside of the Java heap, so the heap-based pointer compression |
|
1220 // would not work (we would have potential aliasing between C-heap |
|
1221 // and Java-heap pointers). For this reason, when using compressed |
|
1222 // oops, we simply use a worker-thread-local, non-shared overflow |
|
1223 // list in the form of a growable array, with a slightly different |
|
1224 // overflow stack draining strategy. If/when we start using fat |
|
1225 // stacks here, we can go back to using (fat) pointer chains |
|
1226 // (although some performance comparisons would be useful since |
|
1227 // single global lists have their own performance disadvantages |
|
1228 // as we were made painfully aware not long ago, see 6786503). |
|
1229 #define BUSY (cast_to_oop<intptr_t>(0x1aff1aff)) |
|
1230 void ParNewGeneration::push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state) { |
|
1231 assert(is_in_reserved(from_space_obj), "Should be from this generation"); |
|
1232 if (ParGCUseLocalOverflow) { |
|
1233 // In the case of compressed oops, we use a private, not-shared |
|
1234 // overflow stack. |
|
1235 par_scan_state->push_on_overflow_stack(from_space_obj); |
|
1236 } else { |
|
1237 assert(!UseCompressedOops, "Error"); |
|
1238 // if the object has been forwarded to itself, then we cannot |
|
1239 // use the klass pointer for the linked list. Instead we have |
|
1240 // to allocate an oopDesc in the C-Heap and use that for the linked list. |
|
1241 // XXX This is horribly inefficient when a promotion failure occurs |
|
1242 // and should be fixed. XXX FIX ME !!! |
|
1243 #ifndef PRODUCT |
|
1244 Atomic::inc(&_num_par_pushes); |
|
1245 assert(_num_par_pushes > 0, "Tautology"); |
|
1246 #endif |
|
1247 if (from_space_obj->forwardee() == from_space_obj) { |
|
1248 oopDesc* listhead = NEW_C_HEAP_OBJ(oopDesc, mtGC); |
|
1249 listhead->forward_to(from_space_obj); |
|
1250 from_space_obj = listhead; |
|
1251 } |
|
1252 oop observed_overflow_list = _overflow_list; |
|
1253 oop cur_overflow_list; |
|
1254 do { |
|
1255 cur_overflow_list = observed_overflow_list; |
|
1256 if (cur_overflow_list != BUSY) { |
|
1257 from_space_obj->set_klass_to_list_ptr(cur_overflow_list); |
|
1258 } else { |
|
1259 from_space_obj->set_klass_to_list_ptr(NULL); |
|
1260 } |
|
1261 observed_overflow_list = |
|
1262 Atomic::cmpxchg((oopDesc*)from_space_obj, &_overflow_list, (oopDesc*)cur_overflow_list); |
|
1263 } while (cur_overflow_list != observed_overflow_list); |
|
1264 } |
|
1265 } |
|
1266 |
|
1267 bool ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) { |
|
1268 bool res; |
|
1269 |
|
1270 if (ParGCUseLocalOverflow) { |
|
1271 res = par_scan_state->take_from_overflow_stack(); |
|
1272 } else { |
|
1273 assert(!UseCompressedOops, "Error"); |
|
1274 res = take_from_overflow_list_work(par_scan_state); |
|
1275 } |
|
1276 return res; |
|
1277 } |
|
1278 |
|
1279 |
|
1280 // *NOTE*: The overflow list manipulation code here and |
|
1281 // in CMSCollector:: are very similar in shape, |
|
1282 // except that in the CMS case we thread the objects |
|
1283 // directly into the list via their mark word, and do |
|
1284 // not need to deal with special cases below related |
|
1285 // to chunking of object arrays and promotion failure |
|
1286 // handling. |
|
1287 // CR 6797058 has been filed to attempt consolidation of |
|
1288 // the common code. |
|
1289 // Because of the common code, if you make any changes in |
|
1290 // the code below, please check the CMS version to see if |
|
1291 // similar changes might be needed. |
|
1292 // See CMSCollector::par_take_from_overflow_list() for |
|
1293 // more extensive documentation comments. |
|
1294 bool ParNewGeneration::take_from_overflow_list_work(ParScanThreadState* par_scan_state) { |
|
1295 ObjToScanQueue* work_q = par_scan_state->work_queue(); |
|
1296 // How many to take? |
|
1297 size_t objsFromOverflow = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
|
1298 (size_t)ParGCDesiredObjsFromOverflowList); |
|
1299 |
|
1300 assert(!UseCompressedOops, "Error"); |
|
1301 assert(par_scan_state->overflow_stack() == NULL, "Error"); |
|
1302 if (_overflow_list == NULL) return false; |
|
1303 |
|
1304 // Otherwise, there was something there; try claiming the list. |
|
1305 oop prefix = cast_to_oop(Atomic::xchg((oopDesc*)BUSY, &_overflow_list)); |
|
1306 // Trim off a prefix of at most objsFromOverflow items |
|
1307 size_t spin_count = ParallelGCThreads; |
|
1308 size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100); |
|
1309 for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) { |
|
1310 // someone grabbed it before we did ... |
|
1311 // ... we spin/block for a short while... |
|
1312 os::naked_sleep(sleep_time_millis); |
|
1313 if (_overflow_list == NULL) { |
|
1314 // nothing left to take |
|
1315 return false; |
|
1316 } else if (_overflow_list != BUSY) { |
|
1317 // try and grab the prefix |
|
1318 prefix = cast_to_oop(Atomic::xchg((oopDesc*)BUSY, &_overflow_list)); |
|
1319 } |
|
1320 } |
|
1321 if (prefix == NULL || prefix == BUSY) { |
|
1322 // Nothing to take or waited long enough |
|
1323 if (prefix == NULL) { |
|
1324 // Write back the NULL in case we overwrote it with BUSY above |
|
1325 // and it is still the same value. |
|
1326 (void) Atomic::cmpxchg((oopDesc*)NULL, &_overflow_list, (oopDesc*)BUSY); |
|
1327 } |
|
1328 return false; |
|
1329 } |
|
1330 assert(prefix != NULL && prefix != BUSY, "Error"); |
|
1331 oop cur = prefix; |
|
1332 for (size_t i = 1; i < objsFromOverflow; ++i) { |
|
1333 oop next = cur->list_ptr_from_klass(); |
|
1334 if (next == NULL) break; |
|
1335 cur = next; |
|
1336 } |
|
1337 assert(cur != NULL, "Loop postcondition"); |
|
1338 |
|
1339 // Reattach remaining (suffix) to overflow list |
|
1340 oop suffix = cur->list_ptr_from_klass(); |
|
1341 if (suffix == NULL) { |
|
1342 // Write back the NULL in lieu of the BUSY we wrote |
|
1343 // above and it is still the same value. |
|
1344 if (_overflow_list == BUSY) { |
|
1345 (void) Atomic::cmpxchg((oopDesc*)NULL, &_overflow_list, (oopDesc*)BUSY); |
|
1346 } |
|
1347 } else { |
|
1348 assert(suffix != BUSY, "Error"); |
|
1349 // suffix will be put back on global list |
|
1350 cur->set_klass_to_list_ptr(NULL); // break off suffix |
|
1351 // It's possible that the list is still in the empty(busy) state |
|
1352 // we left it in a short while ago; in that case we may be |
|
1353 // able to place back the suffix. |
|
1354 oop observed_overflow_list = _overflow_list; |
|
1355 oop cur_overflow_list = observed_overflow_list; |
|
1356 bool attached = false; |
|
1357 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { |
|
1358 observed_overflow_list = |
|
1359 Atomic::cmpxchg((oopDesc*)suffix, &_overflow_list, (oopDesc*)cur_overflow_list); |
|
1360 if (cur_overflow_list == observed_overflow_list) { |
|
1361 attached = true; |
|
1362 break; |
|
1363 } else cur_overflow_list = observed_overflow_list; |
|
1364 } |
|
1365 if (!attached) { |
|
1366 // Too bad, someone else got in in between; we'll need to do a splice. |
|
1367 // Find the last item of suffix list |
|
1368 oop last = suffix; |
|
1369 while (true) { |
|
1370 oop next = last->list_ptr_from_klass(); |
|
1371 if (next == NULL) break; |
|
1372 last = next; |
|
1373 } |
|
1374 // Atomically prepend suffix to current overflow list |
|
1375 observed_overflow_list = _overflow_list; |
|
1376 do { |
|
1377 cur_overflow_list = observed_overflow_list; |
|
1378 if (cur_overflow_list != BUSY) { |
|
1379 // Do the splice ... |
|
1380 last->set_klass_to_list_ptr(cur_overflow_list); |
|
1381 } else { // cur_overflow_list == BUSY |
|
1382 last->set_klass_to_list_ptr(NULL); |
|
1383 } |
|
1384 observed_overflow_list = |
|
1385 Atomic::cmpxchg((oopDesc*)suffix, &_overflow_list, (oopDesc*)cur_overflow_list); |
|
1386 } while (cur_overflow_list != observed_overflow_list); |
|
1387 } |
|
1388 } |
|
1389 |
|
1390 // Push objects on prefix list onto this thread's work queue |
|
1391 assert(prefix != NULL && prefix != BUSY, "program logic"); |
|
1392 cur = prefix; |
|
1393 ssize_t n = 0; |
|
1394 while (cur != NULL) { |
|
1395 oop obj_to_push = cur->forwardee(); |
|
1396 oop next = cur->list_ptr_from_klass(); |
|
1397 cur->set_klass(obj_to_push->klass()); |
|
1398 // This may be an array object that is self-forwarded. In that case, the list pointer |
|
1399 // space, cur, is not in the Java heap, but rather in the C-heap and should be freed. |
|
1400 if (!is_in_reserved(cur)) { |
|
1401 // This can become a scaling bottleneck when there is work queue overflow coincident |
|
1402 // with promotion failure. |
|
1403 oopDesc* f = cur; |
|
1404 FREE_C_HEAP_OBJ(f); |
|
1405 } else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) { |
|
1406 assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned"); |
|
1407 obj_to_push = cur; |
|
1408 } |
|
1409 bool ok = work_q->push(obj_to_push); |
|
1410 assert(ok, "Should have succeeded"); |
|
1411 cur = next; |
|
1412 n++; |
|
1413 } |
|
1414 TASKQUEUE_STATS_ONLY(par_scan_state->note_overflow_refill(n)); |
|
1415 #ifndef PRODUCT |
|
1416 assert(_num_par_pushes >= n, "Too many pops?"); |
|
1417 Atomic::sub(n, &_num_par_pushes); |
|
1418 #endif |
|
1419 return true; |
|
1420 } |
|
1421 #undef BUSY |
|
1422 |
|
1423 void ParNewGeneration::ref_processor_init() { |
|
1424 if (_ref_processor == NULL) { |
|
1425 // Allocate and initialize a reference processor |
|
1426 _span_based_discoverer.set_span(_reserved); |
|
1427 _ref_processor = |
|
1428 new ReferenceProcessor(&_span_based_discoverer, // span |
|
1429 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing |
|
1430 ParallelGCThreads, // mt processing degree |
|
1431 refs_discovery_is_mt(), // mt discovery |
|
1432 ParallelGCThreads, // mt discovery degree |
|
1433 refs_discovery_is_atomic(), // atomic_discovery |
|
1434 NULL, // is_alive_non_header |
|
1435 false); // disable adjusting number of processing threads |
|
1436 } |
|
1437 } |
|
1438 |
|
1439 const char* ParNewGeneration::name() const { |
|
1440 return "par new generation"; |
|
1441 } |
|
1442 |
|
1443 void ParNewGeneration::restore_preserved_marks() { |
|
1444 SharedRestorePreservedMarksTaskExecutor task_executor(CMSHeap::heap()->workers()); |
|
1445 _preserved_marks_set.restore(&task_executor); |
|
1446 } |
|