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1 /* |
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2 * Copyright (c) 2013, 2017, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. |
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8 * |
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9 * This code is distributed in the hope that it will be useful, but WITHOUT |
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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12 * version 2 for more details (a copy is included in the LICENSE file that |
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13 * accompanied this code). |
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14 * |
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15 * You should have received a copy of the GNU General Public License version |
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16 * 2 along with this work; if not, write to the Free Software Foundation, |
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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18 * |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
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22 * |
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23 */ |
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24 |
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25 #ifndef SHARE_VM_GC_G1_G1HOTCARDCACHE_HPP |
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26 #define SHARE_VM_GC_G1_G1HOTCARDCACHE_HPP |
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27 |
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28 #include "gc/g1/g1CardCounts.hpp" |
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29 #include "gc/g1/g1_globals.hpp" |
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30 #include "memory/allocation.hpp" |
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31 #include "runtime/safepoint.hpp" |
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32 #include "runtime/thread.hpp" |
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33 #include "utilities/globalDefinitions.hpp" |
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34 |
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35 class CardTableEntryClosure; |
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36 class DirtyCardQueue; |
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37 class G1CollectedHeap; |
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38 class HeapRegion; |
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39 |
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40 // An evicting cache of cards that have been logged by the G1 post |
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41 // write barrier. Placing a card in the cache delays the refinement |
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42 // of the card until the card is evicted, or the cache is drained |
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43 // during the next evacuation pause. |
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44 // |
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45 // The first thing the G1 post write barrier does is to check whether |
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46 // the card containing the updated pointer is already dirty and, if |
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47 // so, skips the remaining code in the barrier. |
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48 // |
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49 // Delaying the refinement of a card will make the card fail the |
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50 // first is_dirty check in the write barrier, skipping the remainder |
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51 // of the write barrier. |
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52 // |
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53 // This can significantly reduce the overhead of the write barrier |
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54 // code, increasing throughput. |
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55 |
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56 class G1HotCardCache: public CHeapObj<mtGC> { |
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57 |
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58 G1CollectedHeap* _g1h; |
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59 |
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60 bool _use_cache; |
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61 |
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62 G1CardCounts _card_counts; |
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63 |
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64 |
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65 // The card cache table |
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66 jbyte** _hot_cache; |
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67 |
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68 size_t _hot_cache_size; |
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69 |
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70 size_t _hot_cache_par_chunk_size; |
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71 |
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72 // Avoids false sharing when concurrently updating _hot_cache_idx or |
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73 // _hot_cache_par_claimed_idx. These are never updated at the same time |
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74 // thus it's not necessary to separate them as well |
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75 char _pad_before[DEFAULT_CACHE_LINE_SIZE]; |
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76 |
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77 volatile size_t _hot_cache_idx; |
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78 |
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79 volatile size_t _hot_cache_par_claimed_idx; |
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80 |
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81 char _pad_after[DEFAULT_CACHE_LINE_SIZE]; |
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82 |
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83 // The number of cached cards a thread claims when flushing the cache |
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84 static const int ClaimChunkSize = 32; |
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85 |
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86 public: |
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87 static bool default_use_cache() { |
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88 return (G1ConcRSLogCacheSize > 0); |
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89 } |
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90 |
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91 G1HotCardCache(G1CollectedHeap* g1h); |
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92 ~G1HotCardCache(); |
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93 |
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94 void initialize(G1RegionToSpaceMapper* card_counts_storage); |
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95 |
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96 bool use_cache() { return _use_cache; } |
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97 |
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98 void set_use_cache(bool b) { |
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99 _use_cache = (b ? default_use_cache() : false); |
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100 } |
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101 |
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102 // Returns the card to be refined or NULL. |
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103 // |
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104 // Increments the count for given the card. if the card is not 'hot', |
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105 // it is returned for immediate refining. Otherwise the card is |
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106 // added to the hot card cache. |
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107 // If there is enough room in the hot card cache for the card we're |
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108 // adding, NULL is returned and no further action in needed. |
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109 // If we evict a card from the cache to make room for the new card, |
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110 // the evicted card is then returned for refinement. |
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111 jbyte* insert(jbyte* card_ptr); |
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112 |
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113 // Refine the cards that have delayed as a result of |
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114 // being in the cache. |
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115 void drain(CardTableEntryClosure* cl, uint worker_i); |
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116 |
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117 // Set up for parallel processing of the cards in the hot cache |
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118 void reset_hot_cache_claimed_index() { |
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119 _hot_cache_par_claimed_idx = 0; |
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120 } |
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121 |
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122 // Resets the hot card cache and discards the entries. |
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123 void reset_hot_cache() { |
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124 assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint"); |
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125 assert(Thread::current()->is_VM_thread(), "Current thread should be the VMthread"); |
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126 if (default_use_cache()) { |
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127 reset_hot_cache_internal(); |
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128 } |
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129 } |
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130 |
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131 // Zeros the values in the card counts table for entire committed heap |
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132 void reset_card_counts(); |
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133 |
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134 // Zeros the values in the card counts table for the given region |
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135 void reset_card_counts(HeapRegion* hr); |
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136 |
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137 private: |
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138 void reset_hot_cache_internal() { |
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139 assert(_hot_cache != NULL, "Logic"); |
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140 _hot_cache_idx = 0; |
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141 for (size_t i = 0; i < _hot_cache_size; i++) { |
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142 _hot_cache[i] = NULL; |
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143 } |
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144 } |
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145 }; |
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146 |
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147 #endif // SHARE_VM_GC_G1_G1HOTCARDCACHE_HPP |