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1 /*
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2 * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 class ChunkArray;
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26 class ParScanWithoutBarrierClosure;
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27 class ParScanWithBarrierClosure;
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28 class ParRootScanWithoutBarrierClosure;
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29 class ParRootScanWithBarrierTwoGensClosure;
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30 class ParEvacuateFollowersClosure;
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31
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32 // It would be better if these types could be kept local to the .cpp file,
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33 // but they must be here to allow ParScanClosure::do_oop_work to be defined
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34 // in genOopClosures.inline.hpp.
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35
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36
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37 typedef OopTaskQueue ObjToScanQueue;
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38 typedef OopTaskQueueSet ObjToScanQueueSet;
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39
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40 // Enable this to get push/pop/steal stats.
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41 const int PAR_STATS_ENABLED = 0;
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42
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43 class ParKeepAliveClosure: public DefNewGeneration::KeepAliveClosure {
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44 ParScanWeakRefClosure* _par_cl;
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45 public:
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46 ParKeepAliveClosure(ParScanWeakRefClosure* cl);
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47 void do_oop(oop* p);
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48 };
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49
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50 // The state needed by thread performing parallel young-gen collection.
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51 class ParScanThreadState {
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52 friend class ParScanThreadStateSet;
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53 ObjToScanQueue *_work_queue;
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54
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55 ParGCAllocBuffer _to_space_alloc_buffer;
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56
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57 ParScanWithoutBarrierClosure _to_space_closure; // scan_without_gc_barrier
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58 ParScanWithBarrierClosure _old_gen_closure; // scan_with_gc_barrier
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59 ParRootScanWithoutBarrierClosure _to_space_root_closure; // scan_root_without_gc_barrier
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60 // One of these two will be passed to process_strong_roots, which will
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61 // set its generation. The first is for two-gen configs where the
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62 // old gen collects the perm gen; the second is for arbitrary configs.
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63 // The second isn't used right now (it used to be used for the train, an
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64 // incremental collector) but the declaration has been left as a reminder.
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65 ParRootScanWithBarrierTwoGensClosure _older_gen_closure;
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66 // This closure will always be bound to the old gen; it will be used
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67 // in evacuate_followers.
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68 ParRootScanWithBarrierTwoGensClosure _old_gen_root_closure; // scan_old_root_with_gc_barrier
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69 ParEvacuateFollowersClosure _evacuate_followers;
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70 DefNewGeneration::IsAliveClosure _is_alive_closure;
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71 ParScanWeakRefClosure _scan_weak_ref_closure;
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72 ParKeepAliveClosure _keep_alive_closure;
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73
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74
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75 Space* _to_space;
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76 Space* to_space() { return _to_space; }
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77
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78 Generation* _old_gen;
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79 Generation* old_gen() { return _old_gen; }
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80
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81 HeapWord *_young_old_boundary;
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82
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83 int _hash_seed;
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84 int _thread_num;
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85 ageTable _ageTable;
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86
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87 bool _to_space_full;
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88
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89 int _pushes, _pops, _steals, _steal_attempts, _term_attempts;
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90 int _overflow_pushes, _overflow_refills, _overflow_refill_objs;
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91
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92 // Timing numbers.
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93 double _start;
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94 double _start_strong_roots;
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95 double _strong_roots_time;
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96 double _start_term;
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97 double _term_time;
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98
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99 // Helper for trim_queues. Scans subset of an array and makes
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100 // remainder available for work stealing.
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101 void scan_partial_array_and_push_remainder(oop obj);
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102
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103 // In support of CMS' parallel rescan of survivor space.
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104 ChunkArray* _survivor_chunk_array;
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105 ChunkArray* survivor_chunk_array() { return _survivor_chunk_array; }
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106
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107 void record_survivor_plab(HeapWord* plab_start, size_t plab_word_size);
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108
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109 ParScanThreadState(Space* to_space_, ParNewGeneration* gen_,
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110 Generation* old_gen_, int thread_num_,
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111 ObjToScanQueueSet* work_queue_set_, size_t desired_plab_sz_,
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112 ParallelTaskTerminator& term_);
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113
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114 public:
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115 ageTable* age_table() {return &_ageTable;}
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116
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117 ObjToScanQueue* work_queue() { return _work_queue; }
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118
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119 ParGCAllocBuffer* to_space_alloc_buffer() {
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120 return &_to_space_alloc_buffer;
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121 }
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122
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123 ParEvacuateFollowersClosure& evacuate_followers_closure() { return _evacuate_followers; }
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124 DefNewGeneration::IsAliveClosure& is_alive_closure() { return _is_alive_closure; }
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125 ParScanWeakRefClosure& scan_weak_ref_closure() { return _scan_weak_ref_closure; }
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126 ParKeepAliveClosure& keep_alive_closure() { return _keep_alive_closure; }
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127 ParScanClosure& older_gen_closure() { return _older_gen_closure; }
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128 ParRootScanWithoutBarrierClosure& to_space_root_closure() { return _to_space_root_closure; };
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129
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130 // Decrease queue size below "max_size".
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131 void trim_queues(int max_size);
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132
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133 // Is new_obj a candidate for scan_partial_array_and_push_remainder method.
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134 inline bool should_be_partially_scanned(oop new_obj, oop old_obj) const;
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135
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136 int* hash_seed() { return &_hash_seed; }
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137 int thread_num() { return _thread_num; }
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138
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139 // Allocate a to-space block of size "sz", or else return NULL.
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140 HeapWord* alloc_in_to_space_slow(size_t word_sz);
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141
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142 HeapWord* alloc_in_to_space(size_t word_sz) {
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143 HeapWord* obj = to_space_alloc_buffer()->allocate(word_sz);
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144 if (obj != NULL) return obj;
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145 else return alloc_in_to_space_slow(word_sz);
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146 }
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147
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148 HeapWord* young_old_boundary() { return _young_old_boundary; }
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149
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150 void set_young_old_boundary(HeapWord *boundary) {
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151 _young_old_boundary = boundary;
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152 }
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153
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154 // Undo the most recent allocation ("obj", of "word_sz").
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155 void undo_alloc_in_to_space(HeapWord* obj, size_t word_sz);
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156
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157 int pushes() { return _pushes; }
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158 int pops() { return _pops; }
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159 int steals() { return _steals; }
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160 int steal_attempts() { return _steal_attempts; }
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161 int term_attempts() { return _term_attempts; }
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162 int overflow_pushes() { return _overflow_pushes; }
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163 int overflow_refills() { return _overflow_refills; }
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164 int overflow_refill_objs() { return _overflow_refill_objs; }
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165
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166 void note_push() { if (PAR_STATS_ENABLED) _pushes++; }
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167 void note_pop() { if (PAR_STATS_ENABLED) _pops++; }
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168 void note_steal() { if (PAR_STATS_ENABLED) _steals++; }
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169 void note_steal_attempt() { if (PAR_STATS_ENABLED) _steal_attempts++; }
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170 void note_term_attempt() { if (PAR_STATS_ENABLED) _term_attempts++; }
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171 void note_overflow_push() { if (PAR_STATS_ENABLED) _overflow_pushes++; }
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172 void note_overflow_refill(int objs) {
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173 if (PAR_STATS_ENABLED) {
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174 _overflow_refills++;
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175 _overflow_refill_objs += objs;
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176 }
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177 }
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178
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179 void start_strong_roots() {
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180 _start_strong_roots = os::elapsedTime();
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181 }
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182 void end_strong_roots() {
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183 _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
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184 }
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185 double strong_roots_time() { return _strong_roots_time; }
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186 void start_term_time() {
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187 note_term_attempt();
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188 _start_term = os::elapsedTime();
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189 }
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190 void end_term_time() {
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191 _term_time += (os::elapsedTime() - _start_term);
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192 }
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193 double term_time() { return _term_time; }
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194
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195 double elapsed() {
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196 return os::elapsedTime() - _start;
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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 class ParNewGenTask: public AbstractGangTask {
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202 ParNewGeneration* _gen;
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203 Generation* _next_gen;
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204 HeapWord* _young_old_boundary;
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205 class ParScanThreadStateSet* _state_set;
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206
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207 public:
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208 ParNewGenTask(ParNewGeneration* gen,
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209 Generation* next_gen,
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210 HeapWord* young_old_boundary,
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211 ParScanThreadStateSet* state_set);
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212
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213 HeapWord* young_old_boundary() { return _young_old_boundary; }
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214
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215 void work(int i);
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216 };
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217
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218 class KeepAliveClosure: public DefNewGeneration::KeepAliveClosure {
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219 public:
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220 KeepAliveClosure(ScanWeakRefClosure* cl);
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221 void do_oop(oop* p);
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222 };
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223
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224 class EvacuateFollowersClosureGeneral: public VoidClosure {
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225 GenCollectedHeap* _gch;
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226 int _level;
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227 OopsInGenClosure* _scan_cur_or_nonheap;
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228 OopsInGenClosure* _scan_older;
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229 public:
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230 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,
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231 OopsInGenClosure* cur,
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232 OopsInGenClosure* older);
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233 void do_void();
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234 };
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235
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236 // Closure for scanning ParNewGeneration.
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237 // Same as ScanClosure, except does parallel GC barrier.
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238 class ScanClosureWithParBarrier: public ScanClosure {
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239 public:
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240 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier);
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241 void do_oop(oop* p);
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242 };
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243
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244 // Implements AbstractRefProcTaskExecutor for ParNew.
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245 class ParNewRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
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246 public:
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247
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248 ParNewRefProcTaskExecutor(ParNewGeneration& generation,
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249 ParScanThreadStateSet& state_set)
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250 : _generation(generation), _state_set(state_set)
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251 { }
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252
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253 // Executes a task using worker threads.
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254 virtual void execute(ProcessTask& task);
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255 virtual void execute(EnqueueTask& task);
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256 // Switch to single threaded mode.
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257 virtual void set_single_threaded_mode();
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258 private:
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259 ParNewGeneration& _generation;
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260 ParScanThreadStateSet& _state_set;
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261 };
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262
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263
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264 // A Generation that does parallel young-gen collection.
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265
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266 class ParNewGeneration: public DefNewGeneration {
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267 friend class ParNewGenTask;
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268 friend class ParNewRefProcTask;
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269 friend class ParNewRefProcTaskExecutor;
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270 friend class ParScanThreadStateSet;
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271
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272 // XXX use a global constant instead of 64!
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273 struct ObjToScanQueuePadded {
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274 ObjToScanQueue work_queue;
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275 char pad[64 - sizeof(ObjToScanQueue)]; // prevent false sharing
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276 };
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277
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278 // The per-thread work queues, available here for stealing.
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279 ObjToScanQueueSet* _task_queues;
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280
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281 // Desired size of survivor space plab's
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282 PLABStats _plab_stats;
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283
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284 // A list of from-space images of to-be-scanned objects, threaded through
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285 // klass-pointers (klass information already copied to the forwarded
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286 // image.) Manipulated with CAS.
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287 oop _overflow_list;
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288
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289 // If true, older generation does not support promotion undo, so avoid.
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290 static bool _avoid_promotion_undo;
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291
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292 // This closure is used by the reference processor to filter out
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293 // references to live referent.
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294 DefNewGeneration::IsAliveClosure _is_alive_closure;
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295
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296 static oop real_forwardee_slow(oop obj);
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297 static void waste_some_time();
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298
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299 // Preserve the mark of "obj", if necessary, in preparation for its mark
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300 // word being overwritten with a self-forwarding-pointer.
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301 void preserve_mark_if_necessary(oop obj, markOop m);
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302
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303 protected:
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304
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305 bool _survivor_overflow;
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306
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307 bool avoid_promotion_undo() { return _avoid_promotion_undo; }
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308 void set_avoid_promotion_undo(bool v) { _avoid_promotion_undo = v; }
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309
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310 bool survivor_overflow() { return _survivor_overflow; }
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311 void set_survivor_overflow(bool v) { _survivor_overflow = v; }
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312
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313 // Adjust the tenuring threshold. See the implementation for
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314 // the details of the policy.
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315 virtual void adjust_desired_tenuring_threshold();
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316
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317 public:
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318 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level);
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319
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320 ~ParNewGeneration() {
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321 for (uint i = 0; i < ParallelGCThreads; i++)
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322 delete _task_queues->queue(i);
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323
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324 delete _task_queues;
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325 }
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326
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327 virtual void ref_processor_init();
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328 virtual Generation::Name kind() { return Generation::ParNew; }
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329 virtual const char* name() const;
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330 virtual const char* short_name() const { return "ParNew"; }
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331
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332 // override
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333 virtual bool refs_discovery_is_mt() const {
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334 assert(UseParNewGC, "ParNewGeneration only when UseParNewGC");
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335 return ParallelGCThreads > 1;
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336 }
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337
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338 // Make the collection virtual.
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339 virtual void collect(bool full,
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340 bool clear_all_soft_refs,
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341 size_t size,
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342 bool is_tlab);
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343
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344 // This needs to be visible to the closure function.
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345 // "obj" is the object to be copied, "m" is a recent value of its mark
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346 // that must not contain a forwarding pointer (though one might be
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347 // inserted in "obj"s mark word by a parallel thread).
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348 inline oop copy_to_survivor_space(ParScanThreadState* par_scan_state,
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349 oop obj, size_t obj_sz, markOop m) {
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350 if (_avoid_promotion_undo) {
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351 return copy_to_survivor_space_avoiding_promotion_undo(par_scan_state,
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352 obj, obj_sz, m);
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353 }
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354
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355 return copy_to_survivor_space_with_undo(par_scan_state, obj, obj_sz, m);
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356 }
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357
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358 oop copy_to_survivor_space_avoiding_promotion_undo(ParScanThreadState* par_scan_state,
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359 oop obj, size_t obj_sz, markOop m);
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360
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361 oop copy_to_survivor_space_with_undo(ParScanThreadState* par_scan_state,
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362 oop obj, size_t obj_sz, markOop m);
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363
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364 // Push the given (from-space) object on the global overflow list.
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365 void push_on_overflow_list(oop from_space_obj);
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366
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367 // If the global overflow list is non-empty, move some tasks from it
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368 // onto "work_q" (which must be empty). No more than 1/4 of the
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369 // max_elems of "work_q" are moved.
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370 bool take_from_overflow_list(ParScanThreadState* par_scan_state);
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371
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372 // The task queues to be used by parallel GC threads.
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373 ObjToScanQueueSet* task_queues() {
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374 return _task_queues;
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375 }
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376
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377 PLABStats* plab_stats() {
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378 return &_plab_stats;
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379 }
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380
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381 size_t desired_plab_sz() {
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382 return _plab_stats.desired_plab_sz();
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383 }
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384
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385 static oop real_forwardee(oop obj);
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386
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387 DEBUG_ONLY(static bool is_legal_forward_ptr(oop p);)
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388 };
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