1 /* |
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2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. |
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8 * |
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9 * This code is distributed in the hope that it will be useful, but WITHOUT |
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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12 * version 2 for more details (a copy is included in the LICENSE file that |
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13 * accompanied this code). |
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14 * |
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15 * You should have received a copy of the GNU General Public License version |
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16 * 2 along with this work; if not, write to the Free Software Foundation, |
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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18 * |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
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22 * |
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23 */ |
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24 |
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25 #ifndef SHARE_GC_CMS_CONCURRENTMARKSWEEPTHREAD_HPP |
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26 #define SHARE_GC_CMS_CONCURRENTMARKSWEEPTHREAD_HPP |
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27 |
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28 #include "gc/cms/concurrentMarkSweepGeneration.hpp" |
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29 #include "gc/shared/concurrentGCThread.hpp" |
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30 #include "runtime/thread.hpp" |
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31 |
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32 class ConcurrentMarkSweepGeneration; |
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33 class CMSCollector; |
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34 |
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35 // The Concurrent Mark Sweep GC Thread |
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36 class ConcurrentMarkSweepThread: public ConcurrentGCThread { |
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37 friend class VMStructs; |
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38 friend class ConcurrentMarkSweepGeneration; // XXX should remove friendship |
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39 friend class CMSCollector; |
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40 |
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41 private: |
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42 static ConcurrentMarkSweepThread* _cmst; |
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43 static CMSCollector* _collector; |
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44 |
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45 enum CMS_flag_type { |
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46 CMS_nil = NoBits, |
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47 CMS_cms_wants_token = nth_bit(0), |
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48 CMS_cms_has_token = nth_bit(1), |
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49 CMS_vm_wants_token = nth_bit(2), |
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50 CMS_vm_has_token = nth_bit(3) |
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51 }; |
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52 |
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53 static int _CMS_flag; |
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54 |
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55 static bool CMS_flag_is_set(int b) { return (_CMS_flag & b) != 0; } |
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56 static bool set_CMS_flag(int b) { return (_CMS_flag |= b) != 0; } |
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57 static bool clear_CMS_flag(int b) { return (_CMS_flag &= ~b) != 0; } |
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58 void sleepBeforeNextCycle(); |
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59 |
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60 // CMS thread should yield for a young gen collection and direct allocations |
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61 static char _pad_1[64 - sizeof(jint)]; // prevent cache-line sharing |
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62 static volatile jint _pending_yields; |
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63 static char _pad_2[64 - sizeof(jint)]; // prevent cache-line sharing |
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64 |
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65 // debugging |
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66 void verify_ok_to_terminate() const PRODUCT_RETURN; |
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67 |
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68 void run_service(); |
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69 void stop_service(); |
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70 |
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71 public: |
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72 // Constructor |
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73 ConcurrentMarkSweepThread(CMSCollector* collector); |
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74 |
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75 static void threads_do(ThreadClosure* tc); |
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76 |
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77 // Printing |
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78 static void print_all_on(outputStream* st); |
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79 static void print_all() { print_all_on(tty); } |
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80 |
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81 // Returns the CMS Thread |
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82 static ConcurrentMarkSweepThread* cmst() { return _cmst; } |
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83 static CMSCollector* collector() { return _collector; } |
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84 |
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85 // Create and start the CMS Thread, or stop it on shutdown |
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86 static ConcurrentMarkSweepThread* start(CMSCollector* collector); |
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87 |
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88 // Synchronization using CMS token |
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89 static void synchronize(bool is_cms_thread); |
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90 static void desynchronize(bool is_cms_thread); |
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91 static bool vm_thread_has_cms_token() { |
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92 return CMS_flag_is_set(CMS_vm_has_token); |
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93 } |
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94 static bool cms_thread_has_cms_token() { |
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95 return CMS_flag_is_set(CMS_cms_has_token); |
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96 } |
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97 static bool vm_thread_wants_cms_token() { |
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98 return CMS_flag_is_set(CMS_vm_wants_token); |
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99 } |
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100 static bool cms_thread_wants_cms_token() { |
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101 return CMS_flag_is_set(CMS_cms_wants_token); |
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102 } |
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103 |
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104 // Wait on CMS lock until the next synchronous GC |
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105 // or given timeout, whichever is earlier. A timeout value |
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106 // of 0 indicates that there is no upper bound on the wait time. |
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107 // A concurrent full gc request terminates the wait. |
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108 void wait_on_cms_lock(long t_millis); |
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109 |
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110 // Wait on CMS lock until the next synchronous GC |
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111 // or given timeout, whichever is earlier. A timeout value |
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112 // of 0 indicates that there is no upper bound on the wait time. |
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113 // A concurrent full gc request terminates the wait. |
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114 void wait_on_cms_lock_for_scavenge(long t_millis); |
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115 |
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116 // The CMS thread will yield during the work portion of its cycle |
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117 // only when requested to. |
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118 // A synchronous request is used for young gen collections and |
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119 // for direct allocations. The requesting thread increments |
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120 // _pending_yields at the beginning of an operation, and decrements |
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121 // _pending_yields when that operation is completed. |
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122 // In turn, the CMS thread yields when _pending_yields is positive, |
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123 // and continues to yield until the value reverts to 0. |
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124 |
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125 static void increment_pending_yields() { |
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126 Atomic::inc(&_pending_yields); |
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127 assert(_pending_yields >= 0, "can't be negative"); |
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128 } |
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129 static void decrement_pending_yields() { |
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130 Atomic::dec(&_pending_yields); |
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131 assert(_pending_yields >= 0, "can't be negative"); |
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132 } |
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133 static bool should_yield() { return _pending_yields > 0; } |
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134 }; |
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135 |
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136 // For scoped increment/decrement of (synchronous) yield requests |
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137 class CMSSynchronousYieldRequest: public StackObj { |
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138 public: |
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139 CMSSynchronousYieldRequest() { |
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140 ConcurrentMarkSweepThread::increment_pending_yields(); |
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141 } |
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142 ~CMSSynchronousYieldRequest() { |
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143 ConcurrentMarkSweepThread::decrement_pending_yields(); |
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144 } |
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145 }; |
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146 |
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147 // Used to emit a warning in case of unexpectedly excessive |
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148 // looping (in "apparently endless loops") in CMS code. |
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149 class CMSLoopCountWarn: public StackObj { |
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150 private: |
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151 const char* _src; |
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152 const char* _msg; |
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153 const intx _threshold; |
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154 intx _ticks; |
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155 |
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156 public: |
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157 inline CMSLoopCountWarn(const char* src, const char* msg, |
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158 const intx threshold) : |
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159 _src(src), _msg(msg), _threshold(threshold), _ticks(0) { } |
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160 |
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161 inline void tick() { |
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162 _ticks++; |
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163 if (CMSLoopWarn && _ticks % _threshold == 0) { |
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164 log_warning(gc)("%s has looped " INTX_FORMAT " times %s", _src, _ticks, _msg); |
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165 } |
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166 } |
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167 }; |
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168 |
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169 #endif // SHARE_GC_CMS_CONCURRENTMARKSWEEPTHREAD_HPP |
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