0
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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 # include "incls/_precompiled.incl"
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26 # include "incls/_concurrentMarkSweepGeneration.cpp.incl"
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27
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28 // statics
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29 CMSCollector* ConcurrentMarkSweepGeneration::_collector = NULL;
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30 bool CMSCollector::_full_gc_requested = false;
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31
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32 //////////////////////////////////////////////////////////////////
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33 // In support of CMS/VM thread synchronization
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34 //////////////////////////////////////////////////////////////////
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35 // We split use of the CGC_lock into 2 "levels".
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36 // The low-level locking is of the usual CGC_lock monitor. We introduce
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37 // a higher level "token" (hereafter "CMS token") built on top of the
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38 // low level monitor (hereafter "CGC lock").
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39 // The token-passing protocol gives priority to the VM thread. The
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40 // CMS-lock doesn't provide any fairness guarantees, but clients
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41 // should ensure that it is only held for very short, bounded
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42 // durations.
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43 //
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44 // When either of the CMS thread or the VM thread is involved in
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45 // collection operations during which it does not want the other
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46 // thread to interfere, it obtains the CMS token.
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47 //
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48 // If either thread tries to get the token while the other has
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49 // it, that thread waits. However, if the VM thread and CMS thread
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50 // both want the token, then the VM thread gets priority while the
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51 // CMS thread waits. This ensures, for instance, that the "concurrent"
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52 // phases of the CMS thread's work do not block out the VM thread
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53 // for long periods of time as the CMS thread continues to hog
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54 // the token. (See bug 4616232).
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55 //
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56 // The baton-passing functions are, however, controlled by the
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57 // flags _foregroundGCShouldWait and _foregroundGCIsActive,
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58 // and here the low-level CMS lock, not the high level token,
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59 // ensures mutual exclusion.
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60 //
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61 // Two important conditions that we have to satisfy:
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62 // 1. if a thread does a low-level wait on the CMS lock, then it
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63 // relinquishes the CMS token if it were holding that token
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64 // when it acquired the low-level CMS lock.
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65 // 2. any low-level notifications on the low-level lock
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66 // should only be sent when a thread has relinquished the token.
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67 //
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68 // In the absence of either property, we'd have potential deadlock.
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69 //
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70 // We protect each of the CMS (concurrent and sequential) phases
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71 // with the CMS _token_, not the CMS _lock_.
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72 //
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73 // The only code protected by CMS lock is the token acquisition code
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74 // itself, see ConcurrentMarkSweepThread::[de]synchronize(), and the
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75 // baton-passing code.
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76 //
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77 // Unfortunately, i couldn't come up with a good abstraction to factor and
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78 // hide the naked CGC_lock manipulation in the baton-passing code
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79 // further below. That's something we should try to do. Also, the proof
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80 // of correctness of this 2-level locking scheme is far from obvious,
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81 // and potentially quite slippery. We have an uneasy supsicion, for instance,
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82 // that there may be a theoretical possibility of delay/starvation in the
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83 // low-level lock/wait/notify scheme used for the baton-passing because of
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84 // potential intereference with the priority scheme embodied in the
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85 // CMS-token-passing protocol. See related comments at a CGC_lock->wait()
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86 // invocation further below and marked with "XXX 20011219YSR".
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87 // Indeed, as we note elsewhere, this may become yet more slippery
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88 // in the presence of multiple CMS and/or multiple VM threads. XXX
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89
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90 class CMSTokenSync: public StackObj {
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91 private:
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92 bool _is_cms_thread;
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93 public:
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94 CMSTokenSync(bool is_cms_thread):
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95 _is_cms_thread(is_cms_thread) {
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96 assert(is_cms_thread == Thread::current()->is_ConcurrentGC_thread(),
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97 "Incorrect argument to constructor");
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98 ConcurrentMarkSweepThread::synchronize(_is_cms_thread);
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99 }
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100
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101 ~CMSTokenSync() {
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102 assert(_is_cms_thread ?
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103 ConcurrentMarkSweepThread::cms_thread_has_cms_token() :
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104 ConcurrentMarkSweepThread::vm_thread_has_cms_token(),
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105 "Incorrect state");
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106 ConcurrentMarkSweepThread::desynchronize(_is_cms_thread);
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107 }
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108 };
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109
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110 // Convenience class that does a CMSTokenSync, and then acquires
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111 // upto three locks.
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112 class CMSTokenSyncWithLocks: public CMSTokenSync {
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113 private:
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114 // Note: locks are acquired in textual declaration order
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115 // and released in the opposite order
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116 MutexLockerEx _locker1, _locker2, _locker3;
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117 public:
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118 CMSTokenSyncWithLocks(bool is_cms_thread, Mutex* mutex1,
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119 Mutex* mutex2 = NULL, Mutex* mutex3 = NULL):
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120 CMSTokenSync(is_cms_thread),
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121 _locker1(mutex1, Mutex::_no_safepoint_check_flag),
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122 _locker2(mutex2, Mutex::_no_safepoint_check_flag),
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123 _locker3(mutex3, Mutex::_no_safepoint_check_flag)
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124 { }
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125 };
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126
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127
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128 // Wrapper class to temporarily disable icms during a foreground cms collection.
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129 class ICMSDisabler: public StackObj {
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130 public:
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131 // The ctor disables icms and wakes up the thread so it notices the change;
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132 // the dtor re-enables icms. Note that the CMSCollector methods will check
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133 // CMSIncrementalMode.
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134 ICMSDisabler() { CMSCollector::disable_icms(); CMSCollector::start_icms(); }
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135 ~ICMSDisabler() { CMSCollector::enable_icms(); }
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136 };
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137
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138 //////////////////////////////////////////////////////////////////
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139 // Concurrent Mark-Sweep Generation /////////////////////////////
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140 //////////////////////////////////////////////////////////////////
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141
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142 NOT_PRODUCT(CompactibleFreeListSpace* debug_cms_space;)
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143
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144 // This struct contains per-thread things necessary to support parallel
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145 // young-gen collection.
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146 class CMSParGCThreadState: public CHeapObj {
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147 public:
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148 CFLS_LAB lab;
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149 PromotionInfo promo;
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150
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151 // Constructor.
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152 CMSParGCThreadState(CompactibleFreeListSpace* cfls) : lab(cfls) {
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153 promo.setSpace(cfls);
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154 }
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155 };
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156
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157 ConcurrentMarkSweepGeneration::ConcurrentMarkSweepGeneration(
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158 ReservedSpace rs, size_t initial_byte_size, int level,
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159 CardTableRS* ct, bool use_adaptive_freelists,
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160 FreeBlockDictionary::DictionaryChoice dictionaryChoice) :
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161 CardGeneration(rs, initial_byte_size, level, ct),
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162 _dilatation_factor(((double)MinChunkSize)/((double)(oopDesc::header_size()))),
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163 _debug_collection_type(Concurrent_collection_type)
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164 {
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165 HeapWord* bottom = (HeapWord*) _virtual_space.low();
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166 HeapWord* end = (HeapWord*) _virtual_space.high();
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167
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168 _direct_allocated_words = 0;
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169 NOT_PRODUCT(
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170 _numObjectsPromoted = 0;
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171 _numWordsPromoted = 0;
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172 _numObjectsAllocated = 0;
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173 _numWordsAllocated = 0;
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174 )
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175
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176 _cmsSpace = new CompactibleFreeListSpace(_bts, MemRegion(bottom, end),
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177 use_adaptive_freelists,
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178 dictionaryChoice);
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179 NOT_PRODUCT(debug_cms_space = _cmsSpace;)
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180 if (_cmsSpace == NULL) {
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181 vm_exit_during_initialization(
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182 "CompactibleFreeListSpace allocation failure");
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183 }
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184 _cmsSpace->_gen = this;
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185
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186 _gc_stats = new CMSGCStats();
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187
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188 // Verify the assumption that FreeChunk::_prev and OopDesc::_klass
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189 // offsets match. The ability to tell free chunks from objects
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190 // depends on this property.
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191 debug_only(
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192 FreeChunk* junk = NULL;
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193 assert(junk->prev_addr() == (void*)(oop(junk)->klass_addr()),
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194 "Offset of FreeChunk::_prev within FreeChunk must match"
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195 " that of OopDesc::_klass within OopDesc");
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196 )
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197 if (ParallelGCThreads > 0) {
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198 typedef CMSParGCThreadState* CMSParGCThreadStatePtr;
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199 _par_gc_thread_states =
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200 NEW_C_HEAP_ARRAY(CMSParGCThreadStatePtr, ParallelGCThreads);
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201 if (_par_gc_thread_states == NULL) {
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202 vm_exit_during_initialization("Could not allocate par gc structs");
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203 }
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204 for (uint i = 0; i < ParallelGCThreads; i++) {
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205 _par_gc_thread_states[i] = new CMSParGCThreadState(cmsSpace());
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206 if (_par_gc_thread_states[i] == NULL) {
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207 vm_exit_during_initialization("Could not allocate par gc structs");
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208 }
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209 }
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210 } else {
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211 _par_gc_thread_states = NULL;
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212 }
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213 _incremental_collection_failed = false;
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214 // The "dilatation_factor" is the expansion that can occur on
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215 // account of the fact that the minimum object size in the CMS
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216 // generation may be larger than that in, say, a contiguous young
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217 // generation.
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218 // Ideally, in the calculation below, we'd compute the dilatation
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219 // factor as: MinChunkSize/(promoting_gen's min object size)
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220 // Since we do not have such a general query interface for the
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221 // promoting generation, we'll instead just use the mimimum
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222 // object size (which today is a header's worth of space);
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223 // note that all arithmetic is in units of HeapWords.
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224 assert(MinChunkSize >= oopDesc::header_size(), "just checking");
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225 assert(_dilatation_factor >= 1.0, "from previous assert");
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226 }
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227
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228 void ConcurrentMarkSweepGeneration::ref_processor_init() {
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229 assert(collector() != NULL, "no collector");
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230 collector()->ref_processor_init();
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231 }
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232
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233 void CMSCollector::ref_processor_init() {
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234 if (_ref_processor == NULL) {
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235 // Allocate and initialize a reference processor
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236 _ref_processor = ReferenceProcessor::create_ref_processor(
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237 _span, // span
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238 _cmsGen->refs_discovery_is_atomic(), // atomic_discovery
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239 _cmsGen->refs_discovery_is_mt(), // mt_discovery
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240 &_is_alive_closure,
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241 ParallelGCThreads,
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242 ParallelRefProcEnabled);
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243 // Initialize the _ref_processor field of CMSGen
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244 _cmsGen->set_ref_processor(_ref_processor);
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245
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246 // Allocate a dummy ref processor for perm gen.
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247 ReferenceProcessor* rp2 = new ReferenceProcessor();
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248 if (rp2 == NULL) {
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249 vm_exit_during_initialization("Could not allocate ReferenceProcessor object");
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250 }
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251 _permGen->set_ref_processor(rp2);
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252 }
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253 }
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254
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255 CMSAdaptiveSizePolicy* CMSCollector::size_policy() {
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256 GenCollectedHeap* gch = GenCollectedHeap::heap();
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257 assert(gch->kind() == CollectedHeap::GenCollectedHeap,
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258 "Wrong type of heap");
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259 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*)
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260 gch->gen_policy()->size_policy();
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261 assert(sp->is_gc_cms_adaptive_size_policy(),
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262 "Wrong type of size policy");
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263 return sp;
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264 }
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265
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266 CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() {
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267 CMSGCAdaptivePolicyCounters* results =
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268 (CMSGCAdaptivePolicyCounters*) collector_policy()->counters();
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269 assert(
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270 results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind,
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271 "Wrong gc policy counter kind");
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272 return results;
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273 }
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274
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275
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276 void ConcurrentMarkSweepGeneration::initialize_performance_counters() {
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277
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278 const char* gen_name = "old";
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279
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280 // Generation Counters - generation 1, 1 subspace
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281 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space);
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282
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283 _space_counters = new GSpaceCounters(gen_name, 0,
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284 _virtual_space.reserved_size(),
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285 this, _gen_counters);
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286 }
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287
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288 CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha):
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289 _cms_gen(cms_gen)
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290 {
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291 assert(alpha <= 100, "bad value");
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292 _saved_alpha = alpha;
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293
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294 // Initialize the alphas to the bootstrap value of 100.
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295 _gc0_alpha = _cms_alpha = 100;
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296
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297 _cms_begin_time.update();
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298 _cms_end_time.update();
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299
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300 _gc0_duration = 0.0;
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301 _gc0_period = 0.0;
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302 _gc0_promoted = 0;
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303
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304 _cms_duration = 0.0;
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305 _cms_period = 0.0;
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306 _cms_allocated = 0;
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307
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308 _cms_used_at_gc0_begin = 0;
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309 _cms_used_at_gc0_end = 0;
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310 _allow_duty_cycle_reduction = false;
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311 _valid_bits = 0;
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312 _icms_duty_cycle = CMSIncrementalDutyCycle;
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313 }
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314
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315 // If promotion failure handling is on use
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316 // the padded average size of the promotion for each
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317 // young generation collection.
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318 double CMSStats::time_until_cms_gen_full() const {
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319 size_t cms_free = _cms_gen->cmsSpace()->free();
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320 GenCollectedHeap* gch = GenCollectedHeap::heap();
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321 size_t expected_promotion = gch->get_gen(0)->capacity();
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322 if (HandlePromotionFailure) {
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323 expected_promotion = MIN2(
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324 (size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average(),
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325 expected_promotion);
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326 }
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327 if (cms_free > expected_promotion) {
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328 // Start a cms collection if there isn't enough space to promote
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329 // for the next minor collection. Use the padded average as
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330 // a safety factor.
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331 cms_free -= expected_promotion;
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332
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333 // Adjust by the safety factor.
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334 double cms_free_dbl = (double)cms_free;
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335 cms_free_dbl = cms_free_dbl * (100.0 - CMSIncrementalSafetyFactor) / 100.0;
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336
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337 if (PrintGCDetails && Verbose) {
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338 gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free "
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339 SIZE_FORMAT " expected_promotion " SIZE_FORMAT,
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340 cms_free, expected_promotion);
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341 gclog_or_tty->print_cr(" cms_free_dbl %f cms_consumption_rate %f",
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342 cms_free_dbl, cms_consumption_rate() + 1.0);
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343 }
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344 // Add 1 in case the consumption rate goes to zero.
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345 return cms_free_dbl / (cms_consumption_rate() + 1.0);
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346 }
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347 return 0.0;
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348 }
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349
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350 // Compare the duration of the cms collection to the
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351 // time remaining before the cms generation is empty.
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352 // Note that the time from the start of the cms collection
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353 // to the start of the cms sweep (less than the total
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354 // duration of the cms collection) can be used. This
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355 // has been tried and some applications experienced
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356 // promotion failures early in execution. This was
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357 // possibly because the averages were not accurate
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358 // enough at the beginning.
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359 double CMSStats::time_until_cms_start() const {
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360 // We add "gc0_period" to the "work" calculation
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361 // below because this query is done (mostly) at the
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362 // end of a scavenge, so we need to conservatively
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363 // account for that much possible delay
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364 // in the query so as to avoid concurrent mode failures
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365 // due to starting the collection just a wee bit too
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366 // late.
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367 double work = cms_duration() + gc0_period();
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368 double deadline = time_until_cms_gen_full();
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369 if (work > deadline) {
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370 if (Verbose && PrintGCDetails) {
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371 gclog_or_tty->print(
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372 " CMSCollector: collect because of anticipated promotion "
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373 "before full %3.7f + %3.7f > %3.7f ", cms_duration(),
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374 gc0_period(), time_until_cms_gen_full());
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375 }
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376 return 0.0;
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377 }
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378 return work - deadline;
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379 }
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380
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381 // Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the
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382 // amount of change to prevent wild oscillation.
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383 unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle,
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384 unsigned int new_duty_cycle) {
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385 assert(old_duty_cycle <= 100, "bad input value");
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386 assert(new_duty_cycle <= 100, "bad input value");
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387
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388 // Note: use subtraction with caution since it may underflow (values are
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389 // unsigned). Addition is safe since we're in the range 0-100.
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390 unsigned int damped_duty_cycle = new_duty_cycle;
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391 if (new_duty_cycle < old_duty_cycle) {
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392 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U);
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393 if (new_duty_cycle + largest_delta < old_duty_cycle) {
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394 damped_duty_cycle = old_duty_cycle - largest_delta;
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395 }
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396 } else if (new_duty_cycle > old_duty_cycle) {
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397 const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U);
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398 if (new_duty_cycle > old_duty_cycle + largest_delta) {
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399 damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U);
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400 }
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401 }
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402 assert(damped_duty_cycle <= 100, "invalid duty cycle computed");
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403
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404 if (CMSTraceIncrementalPacing) {
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405 gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ",
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406 old_duty_cycle, new_duty_cycle, damped_duty_cycle);
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407 }
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408 return damped_duty_cycle;
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409 }
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410
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411 unsigned int CMSStats::icms_update_duty_cycle_impl() {
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412 assert(CMSIncrementalPacing && valid(),
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413 "should be handled in icms_update_duty_cycle()");
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414
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415 double cms_time_so_far = cms_timer().seconds();
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416 double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M;
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417 double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far);
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418
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419 // Avoid division by 0.
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420 double time_until_full = MAX2(time_until_cms_gen_full(), 0.01);
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421 double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full;
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422
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423 unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U);
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424 if (new_duty_cycle > _icms_duty_cycle) {
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425 // Avoid very small duty cycles (1 or 2); 0 is allowed.
|
|
426 if (new_duty_cycle > 2) {
|
|
427 _icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle,
|
|
428 new_duty_cycle);
|
|
429 }
|
|
430 } else if (_allow_duty_cycle_reduction) {
|
|
431 // The duty cycle is reduced only once per cms cycle (see record_cms_end()).
|
|
432 new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle);
|
|
433 // Respect the minimum duty cycle.
|
|
434 unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin;
|
|
435 _icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle);
|
|
436 }
|
|
437
|
|
438 if (PrintGCDetails || CMSTraceIncrementalPacing) {
|
|
439 gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle);
|
|
440 }
|
|
441
|
|
442 _allow_duty_cycle_reduction = false;
|
|
443 return _icms_duty_cycle;
|
|
444 }
|
|
445
|
|
446 #ifndef PRODUCT
|
|
447 void CMSStats::print_on(outputStream *st) const {
|
|
448 st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha);
|
|
449 st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT,
|
|
450 gc0_duration(), gc0_period(), gc0_promoted());
|
|
451 st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT,
|
|
452 cms_duration(), cms_duration_per_mb(),
|
|
453 cms_period(), cms_allocated());
|
|
454 st->print(",cms_since_beg=%g,cms_since_end=%g",
|
|
455 cms_time_since_begin(), cms_time_since_end());
|
|
456 st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT,
|
|
457 _cms_used_at_gc0_begin, _cms_used_at_gc0_end);
|
|
458 if (CMSIncrementalMode) {
|
|
459 st->print(",dc=%d", icms_duty_cycle());
|
|
460 }
|
|
461
|
|
462 if (valid()) {
|
|
463 st->print(",promo_rate=%g,cms_alloc_rate=%g",
|
|
464 promotion_rate(), cms_allocation_rate());
|
|
465 st->print(",cms_consumption_rate=%g,time_until_full=%g",
|
|
466 cms_consumption_rate(), time_until_cms_gen_full());
|
|
467 }
|
|
468 st->print(" ");
|
|
469 }
|
|
470 #endif // #ifndef PRODUCT
|
|
471
|
|
472 CMSCollector::CollectorState CMSCollector::_collectorState =
|
|
473 CMSCollector::Idling;
|
|
474 bool CMSCollector::_foregroundGCIsActive = false;
|
|
475 bool CMSCollector::_foregroundGCShouldWait = false;
|
|
476
|
|
477 CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
|
|
478 ConcurrentMarkSweepGeneration* permGen,
|
|
479 CardTableRS* ct,
|
|
480 ConcurrentMarkSweepPolicy* cp):
|
|
481 _cmsGen(cmsGen),
|
|
482 _permGen(permGen),
|
|
483 _ct(ct),
|
|
484 _ref_processor(NULL), // will be set later
|
|
485 _conc_workers(NULL), // may be set later
|
|
486 _abort_preclean(false),
|
|
487 _start_sampling(false),
|
|
488 _between_prologue_and_epilogue(false),
|
|
489 _markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"),
|
|
490 _perm_gen_verify_bit_map(0, -1 /* no mutex */, "No_lock"),
|
|
491 _modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize),
|
|
492 -1 /* lock-free */, "No_lock" /* dummy */),
|
|
493 _modUnionClosure(&_modUnionTable),
|
|
494 _modUnionClosurePar(&_modUnionTable),
|
|
495 _is_alive_closure(&_markBitMap),
|
|
496 _restart_addr(NULL),
|
|
497 _overflow_list(NULL),
|
|
498 _preserved_oop_stack(NULL),
|
|
499 _preserved_mark_stack(NULL),
|
|
500 _stats(cmsGen),
|
|
501 _eden_chunk_array(NULL), // may be set in ctor body
|
|
502 _eden_chunk_capacity(0), // -- ditto --
|
|
503 _eden_chunk_index(0), // -- ditto --
|
|
504 _survivor_plab_array(NULL), // -- ditto --
|
|
505 _survivor_chunk_array(NULL), // -- ditto --
|
|
506 _survivor_chunk_capacity(0), // -- ditto --
|
|
507 _survivor_chunk_index(0), // -- ditto --
|
|
508 _ser_pmc_preclean_ovflw(0),
|
|
509 _ser_pmc_remark_ovflw(0),
|
|
510 _par_pmc_remark_ovflw(0),
|
|
511 _ser_kac_ovflw(0),
|
|
512 _par_kac_ovflw(0),
|
|
513 #ifndef PRODUCT
|
|
514 _num_par_pushes(0),
|
|
515 #endif
|
|
516 _collection_count_start(0),
|
|
517 _verifying(false),
|
|
518 _icms_start_limit(NULL),
|
|
519 _icms_stop_limit(NULL),
|
|
520 _verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"),
|
|
521 _completed_initialization(false),
|
|
522 _collector_policy(cp),
|
|
523 _unload_classes(false),
|
|
524 _unloaded_classes_last_cycle(false),
|
|
525 _sweep_estimate(CMS_SweepWeight, CMS_SweepPadding)
|
|
526 {
|
|
527 if (ExplicitGCInvokesConcurrentAndUnloadsClasses) {
|
|
528 ExplicitGCInvokesConcurrent = true;
|
|
529 }
|
|
530 // Now expand the span and allocate the collection support structures
|
|
531 // (MUT, marking bit map etc.) to cover both generations subject to
|
|
532 // collection.
|
|
533
|
|
534 // First check that _permGen is adjacent to _cmsGen and above it.
|
|
535 assert( _cmsGen->reserved().word_size() > 0
|
|
536 && _permGen->reserved().word_size() > 0,
|
|
537 "generations should not be of zero size");
|
|
538 assert(_cmsGen->reserved().intersection(_permGen->reserved()).is_empty(),
|
|
539 "_cmsGen and _permGen should not overlap");
|
|
540 assert(_cmsGen->reserved().end() == _permGen->reserved().start(),
|
|
541 "_cmsGen->end() different from _permGen->start()");
|
|
542
|
|
543 // For use by dirty card to oop closures.
|
|
544 _cmsGen->cmsSpace()->set_collector(this);
|
|
545 _permGen->cmsSpace()->set_collector(this);
|
|
546
|
|
547 // Adjust my span to cover old (cms) gen and perm gen
|
|
548 _span = _cmsGen->reserved()._union(_permGen->reserved());
|
|
549 // Initialize the span of is_alive_closure
|
|
550 _is_alive_closure.set_span(_span);
|
|
551
|
|
552 // Allocate MUT and marking bit map
|
|
553 {
|
|
554 MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag);
|
|
555 if (!_markBitMap.allocate(_span)) {
|
|
556 warning("Failed to allocate CMS Bit Map");
|
|
557 return;
|
|
558 }
|
|
559 assert(_markBitMap.covers(_span), "_markBitMap inconsistency?");
|
|
560 }
|
|
561 {
|
|
562 _modUnionTable.allocate(_span);
|
|
563 assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?");
|
|
564 }
|
|
565
|
|
566 if (!_markStack.allocate(CMSMarkStackSize)) {
|
|
567 warning("Failed to allocate CMS Marking Stack");
|
|
568 return;
|
|
569 }
|
|
570 if (!_revisitStack.allocate(CMSRevisitStackSize)) {
|
|
571 warning("Failed to allocate CMS Revisit Stack");
|
|
572 return;
|
|
573 }
|
|
574
|
|
575 // Support for multi-threaded concurrent phases
|
|
576 if (ParallelGCThreads > 0 && CMSConcurrentMTEnabled) {
|
|
577 if (FLAG_IS_DEFAULT(ParallelCMSThreads)) {
|
|
578 // just for now
|
|
579 FLAG_SET_DEFAULT(ParallelCMSThreads, (ParallelGCThreads + 3)/4);
|
|
580 }
|
|
581 if (ParallelCMSThreads > 1) {
|
|
582 _conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads",
|
|
583 ParallelCMSThreads, true);
|
|
584 if (_conc_workers == NULL) {
|
|
585 warning("GC/CMS: _conc_workers allocation failure: "
|
|
586 "forcing -CMSConcurrentMTEnabled");
|
|
587 CMSConcurrentMTEnabled = false;
|
|
588 }
|
|
589 } else {
|
|
590 CMSConcurrentMTEnabled = false;
|
|
591 }
|
|
592 }
|
|
593 if (!CMSConcurrentMTEnabled) {
|
|
594 ParallelCMSThreads = 0;
|
|
595 } else {
|
|
596 // Turn off CMSCleanOnEnter optimization temporarily for
|
|
597 // the MT case where it's not fixed yet; see 6178663.
|
|
598 CMSCleanOnEnter = false;
|
|
599 }
|
|
600 assert((_conc_workers != NULL) == (ParallelCMSThreads > 1),
|
|
601 "Inconsistency");
|
|
602
|
|
603 // Parallel task queues; these are shared for the
|
|
604 // concurrent and stop-world phases of CMS, but
|
|
605 // are not shared with parallel scavenge (ParNew).
|
|
606 {
|
|
607 uint i;
|
|
608 uint num_queues = (uint) MAX2(ParallelGCThreads, ParallelCMSThreads);
|
|
609
|
|
610 if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled
|
|
611 || ParallelRefProcEnabled)
|
|
612 && num_queues > 0) {
|
|
613 _task_queues = new OopTaskQueueSet(num_queues);
|
|
614 if (_task_queues == NULL) {
|
|
615 warning("task_queues allocation failure.");
|
|
616 return;
|
|
617 }
|
|
618 _hash_seed = NEW_C_HEAP_ARRAY(int, num_queues);
|
|
619 if (_hash_seed == NULL) {
|
|
620 warning("_hash_seed array allocation failure");
|
|
621 return;
|
|
622 }
|
|
623
|
|
624 // XXX use a global constant instead of 64!
|
|
625 typedef struct OopTaskQueuePadded {
|
|
626 OopTaskQueue work_queue;
|
|
627 char pad[64 - sizeof(OopTaskQueue)]; // prevent false sharing
|
|
628 } OopTaskQueuePadded;
|
|
629
|
|
630 for (i = 0; i < num_queues; i++) {
|
|
631 OopTaskQueuePadded *q_padded = new OopTaskQueuePadded();
|
|
632 if (q_padded == NULL) {
|
|
633 warning("work_queue allocation failure.");
|
|
634 return;
|
|
635 }
|
|
636 _task_queues->register_queue(i, &q_padded->work_queue);
|
|
637 }
|
|
638 for (i = 0; i < num_queues; i++) {
|
|
639 _task_queues->queue(i)->initialize();
|
|
640 _hash_seed[i] = 17; // copied from ParNew
|
|
641 }
|
|
642 }
|
|
643 }
|
|
644
|
|
645 // "initiatingOccupancy" is the occupancy ratio at which we trigger
|
|
646 // a new collection cycle. Unless explicitly specified via
|
|
647 // CMSTriggerRatio, it is calculated by:
|
|
648 // Let "f" be MinHeapFreeRatio in
|
|
649 //
|
|
650 // intiatingOccupancy = 100-f +
|
|
651 // f * (CMSTriggerRatio/100)
|
|
652 // That is, if we assume the heap is at its desired maximum occupancy at the
|
|
653 // end of a collection, we let CMSTriggerRatio of the (purported) free
|
|
654 // space be allocated before initiating a new collection cycle.
|
|
655 if (CMSInitiatingOccupancyFraction > 0) {
|
|
656 _initiatingOccupancy = (double)CMSInitiatingOccupancyFraction / 100.0;
|
|
657 } else {
|
|
658 _initiatingOccupancy = ((100 - MinHeapFreeRatio) +
|
|
659 (double)(CMSTriggerRatio *
|
|
660 MinHeapFreeRatio) / 100.0)
|
|
661 / 100.0;
|
|
662 }
|
|
663 // Clip CMSBootstrapOccupancy between 0 and 100.
|
|
664 _bootstrap_occupancy = ((double)MIN2((intx)100, MAX2((intx)0, CMSBootstrapOccupancy)))
|
|
665 /(double)100;
|
|
666
|
|
667 _full_gcs_since_conc_gc = 0;
|
|
668
|
|
669 // Now tell CMS generations the identity of their collector
|
|
670 ConcurrentMarkSweepGeneration::set_collector(this);
|
|
671
|
|
672 // Create & start a CMS thread for this CMS collector
|
|
673 _cmsThread = ConcurrentMarkSweepThread::start(this);
|
|
674 assert(cmsThread() != NULL, "CMS Thread should have been created");
|
|
675 assert(cmsThread()->collector() == this,
|
|
676 "CMS Thread should refer to this gen");
|
|
677 assert(CGC_lock != NULL, "Where's the CGC_lock?");
|
|
678
|
|
679 // Support for parallelizing young gen rescan
|
|
680 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
681 _young_gen = gch->prev_gen(_cmsGen);
|
|
682 if (gch->supports_inline_contig_alloc()) {
|
|
683 _top_addr = gch->top_addr();
|
|
684 _end_addr = gch->end_addr();
|
|
685 assert(_young_gen != NULL, "no _young_gen");
|
|
686 _eden_chunk_index = 0;
|
|
687 _eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain;
|
|
688 _eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity);
|
|
689 if (_eden_chunk_array == NULL) {
|
|
690 _eden_chunk_capacity = 0;
|
|
691 warning("GC/CMS: _eden_chunk_array allocation failure");
|
|
692 }
|
|
693 }
|
|
694 assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error");
|
|
695
|
|
696 // Support for parallelizing survivor space rescan
|
|
697 if (CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) {
|
|
698 size_t max_plab_samples = MaxNewSize/((SurvivorRatio+2)*MinTLABSize);
|
|
699 _survivor_plab_array = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads);
|
|
700 _survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples);
|
|
701 _cursor = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads);
|
|
702 if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL
|
|
703 || _cursor == NULL) {
|
|
704 warning("Failed to allocate survivor plab/chunk array");
|
|
705 if (_survivor_plab_array != NULL) {
|
|
706 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array);
|
|
707 _survivor_plab_array = NULL;
|
|
708 }
|
|
709 if (_survivor_chunk_array != NULL) {
|
|
710 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array);
|
|
711 _survivor_chunk_array = NULL;
|
|
712 }
|
|
713 if (_cursor != NULL) {
|
|
714 FREE_C_HEAP_ARRAY(size_t, _cursor);
|
|
715 _cursor = NULL;
|
|
716 }
|
|
717 } else {
|
|
718 _survivor_chunk_capacity = 2*max_plab_samples;
|
|
719 for (uint i = 0; i < ParallelGCThreads; i++) {
|
|
720 HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples);
|
|
721 if (vec == NULL) {
|
|
722 warning("Failed to allocate survivor plab array");
|
|
723 for (int j = i; j > 0; j--) {
|
|
724 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array());
|
|
725 }
|
|
726 FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array);
|
|
727 FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array);
|
|
728 _survivor_plab_array = NULL;
|
|
729 _survivor_chunk_array = NULL;
|
|
730 _survivor_chunk_capacity = 0;
|
|
731 break;
|
|
732 } else {
|
|
733 ChunkArray* cur =
|
|
734 ::new (&_survivor_plab_array[i]) ChunkArray(vec,
|
|
735 max_plab_samples);
|
|
736 assert(cur->end() == 0, "Should be 0");
|
|
737 assert(cur->array() == vec, "Should be vec");
|
|
738 assert(cur->capacity() == max_plab_samples, "Error");
|
|
739 }
|
|
740 }
|
|
741 }
|
|
742 }
|
|
743 assert( ( _survivor_plab_array != NULL
|
|
744 && _survivor_chunk_array != NULL)
|
|
745 || ( _survivor_chunk_capacity == 0
|
|
746 && _survivor_chunk_index == 0),
|
|
747 "Error");
|
|
748
|
|
749 // Choose what strong roots should be scanned depending on verification options
|
|
750 // and perm gen collection mode.
|
|
751 if (!CMSClassUnloadingEnabled) {
|
|
752 // If class unloading is disabled we want to include all classes into the root set.
|
|
753 add_root_scanning_option(SharedHeap::SO_AllClasses);
|
|
754 } else {
|
|
755 add_root_scanning_option(SharedHeap::SO_SystemClasses);
|
|
756 }
|
|
757
|
|
758 NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;)
|
|
759 _gc_counters = new CollectorCounters("CMS", 1);
|
|
760 _completed_initialization = true;
|
|
761 _sweep_timer.start(); // start of time
|
|
762 }
|
|
763
|
|
764 const char* ConcurrentMarkSweepGeneration::name() const {
|
|
765 return "concurrent mark-sweep generation";
|
|
766 }
|
|
767 void ConcurrentMarkSweepGeneration::update_counters() {
|
|
768 if (UsePerfData) {
|
|
769 _space_counters->update_all();
|
|
770 _gen_counters->update_all();
|
|
771 }
|
|
772 }
|
|
773
|
|
774 // this is an optimized version of update_counters(). it takes the
|
|
775 // used value as a parameter rather than computing it.
|
|
776 //
|
|
777 void ConcurrentMarkSweepGeneration::update_counters(size_t used) {
|
|
778 if (UsePerfData) {
|
|
779 _space_counters->update_used(used);
|
|
780 _space_counters->update_capacity();
|
|
781 _gen_counters->update_all();
|
|
782 }
|
|
783 }
|
|
784
|
|
785 void ConcurrentMarkSweepGeneration::print() const {
|
|
786 Generation::print();
|
|
787 cmsSpace()->print();
|
|
788 }
|
|
789
|
|
790 #ifndef PRODUCT
|
|
791 void ConcurrentMarkSweepGeneration::print_statistics() {
|
|
792 cmsSpace()->printFLCensus(0);
|
|
793 }
|
|
794 #endif
|
|
795
|
|
796 void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) {
|
|
797 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
798 if (PrintGCDetails) {
|
|
799 if (Verbose) {
|
|
800 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]",
|
|
801 level(), short_name(), s, used(), capacity());
|
|
802 } else {
|
|
803 gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]",
|
|
804 level(), short_name(), s, used() / K, capacity() / K);
|
|
805 }
|
|
806 }
|
|
807 if (Verbose) {
|
|
808 gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")",
|
|
809 gch->used(), gch->capacity());
|
|
810 } else {
|
|
811 gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)",
|
|
812 gch->used() / K, gch->capacity() / K);
|
|
813 }
|
|
814 }
|
|
815
|
|
816 size_t
|
|
817 ConcurrentMarkSweepGeneration::contiguous_available() const {
|
|
818 // dld proposes an improvement in precision here. If the committed
|
|
819 // part of the space ends in a free block we should add that to
|
|
820 // uncommitted size in the calculation below. Will make this
|
|
821 // change later, staying with the approximation below for the
|
|
822 // time being. -- ysr.
|
|
823 return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc());
|
|
824 }
|
|
825
|
|
826 size_t
|
|
827 ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const {
|
|
828 return _cmsSpace->max_alloc_in_words() * HeapWordSize;
|
|
829 }
|
|
830
|
|
831 size_t ConcurrentMarkSweepGeneration::max_available() const {
|
|
832 return free() + _virtual_space.uncommitted_size();
|
|
833 }
|
|
834
|
|
835 bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe(
|
|
836 size_t max_promotion_in_bytes,
|
|
837 bool younger_handles_promotion_failure) const {
|
|
838
|
|
839 // This is the most conservative test. Full promotion is
|
|
840 // guaranteed if this is used. The multiplicative factor is to
|
|
841 // account for the worst case "dilatation".
|
|
842 double adjusted_max_promo_bytes = _dilatation_factor * max_promotion_in_bytes;
|
|
843 if (adjusted_max_promo_bytes > (double)max_uintx) { // larger than size_t
|
|
844 adjusted_max_promo_bytes = (double)max_uintx;
|
|
845 }
|
|
846 bool result = (max_contiguous_available() >= (size_t)adjusted_max_promo_bytes);
|
|
847
|
|
848 if (younger_handles_promotion_failure && !result) {
|
|
849 // Full promotion is not guaranteed because fragmentation
|
|
850 // of the cms generation can prevent the full promotion.
|
|
851 result = (max_available() >= (size_t)adjusted_max_promo_bytes);
|
|
852
|
|
853 if (!result) {
|
|
854 // With promotion failure handling the test for the ability
|
|
855 // to support the promotion does not have to be guaranteed.
|
|
856 // Use an average of the amount promoted.
|
|
857 result = max_available() >= (size_t)
|
|
858 gc_stats()->avg_promoted()->padded_average();
|
|
859 if (PrintGC && Verbose && result) {
|
|
860 gclog_or_tty->print_cr(
|
|
861 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe"
|
|
862 " max_available: " SIZE_FORMAT
|
|
863 " avg_promoted: " SIZE_FORMAT,
|
|
864 max_available(), (size_t)
|
|
865 gc_stats()->avg_promoted()->padded_average());
|
|
866 }
|
|
867 } else {
|
|
868 if (PrintGC && Verbose) {
|
|
869 gclog_or_tty->print_cr(
|
|
870 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe"
|
|
871 " max_available: " SIZE_FORMAT
|
|
872 " adj_max_promo_bytes: " SIZE_FORMAT,
|
|
873 max_available(), (size_t)adjusted_max_promo_bytes);
|
|
874 }
|
|
875 }
|
|
876 } else {
|
|
877 if (PrintGC && Verbose) {
|
|
878 gclog_or_tty->print_cr(
|
|
879 "\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe"
|
|
880 " contiguous_available: " SIZE_FORMAT
|
|
881 " adj_max_promo_bytes: " SIZE_FORMAT,
|
|
882 max_contiguous_available(), (size_t)adjusted_max_promo_bytes);
|
|
883 }
|
|
884 }
|
|
885 return result;
|
|
886 }
|
|
887
|
|
888 CompactibleSpace*
|
|
889 ConcurrentMarkSweepGeneration::first_compaction_space() const {
|
|
890 return _cmsSpace;
|
|
891 }
|
|
892
|
|
893 void ConcurrentMarkSweepGeneration::reset_after_compaction() {
|
|
894 // Clear the promotion information. These pointers can be adjusted
|
|
895 // along with all the other pointers into the heap but
|
|
896 // compaction is expected to be a rare event with
|
|
897 // a heap using cms so don't do it without seeing the need.
|
|
898 if (ParallelGCThreads > 0) {
|
|
899 for (uint i = 0; i < ParallelGCThreads; i++) {
|
|
900 _par_gc_thread_states[i]->promo.reset();
|
|
901 }
|
|
902 }
|
|
903 }
|
|
904
|
|
905 void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) {
|
|
906 blk->do_space(_cmsSpace);
|
|
907 }
|
|
908
|
|
909 void ConcurrentMarkSweepGeneration::compute_new_size() {
|
|
910 assert_locked_or_safepoint(Heap_lock);
|
|
911
|
|
912 // If incremental collection failed, we just want to expand
|
|
913 // to the limit.
|
|
914 if (incremental_collection_failed()) {
|
|
915 clear_incremental_collection_failed();
|
|
916 grow_to_reserved();
|
|
917 return;
|
|
918 }
|
|
919
|
|
920 size_t expand_bytes = 0;
|
|
921 double free_percentage = ((double) free()) / capacity();
|
|
922 double desired_free_percentage = (double) MinHeapFreeRatio / 100;
|
|
923 double maximum_free_percentage = (double) MaxHeapFreeRatio / 100;
|
|
924
|
|
925 // compute expansion delta needed for reaching desired free percentage
|
|
926 if (free_percentage < desired_free_percentage) {
|
|
927 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage));
|
|
928 assert(desired_capacity >= capacity(), "invalid expansion size");
|
|
929 expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes);
|
|
930 }
|
|
931 if (expand_bytes > 0) {
|
|
932 if (PrintGCDetails && Verbose) {
|
|
933 size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage));
|
|
934 gclog_or_tty->print_cr("\nFrom compute_new_size: ");
|
|
935 gclog_or_tty->print_cr(" Free fraction %f", free_percentage);
|
|
936 gclog_or_tty->print_cr(" Desired free fraction %f",
|
|
937 desired_free_percentage);
|
|
938 gclog_or_tty->print_cr(" Maximum free fraction %f",
|
|
939 maximum_free_percentage);
|
|
940 gclog_or_tty->print_cr(" Capactiy "SIZE_FORMAT, capacity()/1000);
|
|
941 gclog_or_tty->print_cr(" Desired capacity "SIZE_FORMAT,
|
|
942 desired_capacity/1000);
|
|
943 int prev_level = level() - 1;
|
|
944 if (prev_level >= 0) {
|
|
945 size_t prev_size = 0;
|
|
946 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
947 Generation* prev_gen = gch->_gens[prev_level];
|
|
948 prev_size = prev_gen->capacity();
|
|
949 gclog_or_tty->print_cr(" Younger gen size "SIZE_FORMAT,
|
|
950 prev_size/1000);
|
|
951 }
|
|
952 gclog_or_tty->print_cr(" unsafe_max_alloc_nogc "SIZE_FORMAT,
|
|
953 unsafe_max_alloc_nogc()/1000);
|
|
954 gclog_or_tty->print_cr(" contiguous available "SIZE_FORMAT,
|
|
955 contiguous_available()/1000);
|
|
956 gclog_or_tty->print_cr(" Expand by "SIZE_FORMAT" (bytes)",
|
|
957 expand_bytes);
|
|
958 }
|
|
959 // safe if expansion fails
|
|
960 expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio);
|
|
961 if (PrintGCDetails && Verbose) {
|
|
962 gclog_or_tty->print_cr(" Expanded free fraction %f",
|
|
963 ((double) free()) / capacity());
|
|
964 }
|
|
965 }
|
|
966 }
|
|
967
|
|
968 Mutex* ConcurrentMarkSweepGeneration::freelistLock() const {
|
|
969 return cmsSpace()->freelistLock();
|
|
970 }
|
|
971
|
|
972 HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size,
|
|
973 bool tlab) {
|
|
974 CMSSynchronousYieldRequest yr;
|
|
975 MutexLockerEx x(freelistLock(),
|
|
976 Mutex::_no_safepoint_check_flag);
|
|
977 return have_lock_and_allocate(size, tlab);
|
|
978 }
|
|
979
|
|
980 HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size,
|
|
981 bool tlab) {
|
|
982 assert_lock_strong(freelistLock());
|
|
983 size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size);
|
|
984 HeapWord* res = cmsSpace()->allocate(adjustedSize);
|
|
985 // Allocate the object live (grey) if the background collector has
|
|
986 // started marking. This is necessary because the marker may
|
|
987 // have passed this address and consequently this object will
|
|
988 // not otherwise be greyed and would be incorrectly swept up.
|
|
989 // Note that if this object contains references, the writing
|
|
990 // of those references will dirty the card containing this object
|
|
991 // allowing the object to be blackened (and its references scanned)
|
|
992 // either during a preclean phase or at the final checkpoint.
|
|
993 if (res != NULL) {
|
|
994 collector()->direct_allocated(res, adjustedSize);
|
|
995 _direct_allocated_words += adjustedSize;
|
|
996 // allocation counters
|
|
997 NOT_PRODUCT(
|
|
998 _numObjectsAllocated++;
|
|
999 _numWordsAllocated += (int)adjustedSize;
|
|
1000 )
|
|
1001 }
|
|
1002 return res;
|
|
1003 }
|
|
1004
|
|
1005 // In the case of direct allocation by mutators in a generation that
|
|
1006 // is being concurrently collected, the object must be allocated
|
|
1007 // live (grey) if the background collector has started marking.
|
|
1008 // This is necessary because the marker may
|
|
1009 // have passed this address and consequently this object will
|
|
1010 // not otherwise be greyed and would be incorrectly swept up.
|
|
1011 // Note that if this object contains references, the writing
|
|
1012 // of those references will dirty the card containing this object
|
|
1013 // allowing the object to be blackened (and its references scanned)
|
|
1014 // either during a preclean phase or at the final checkpoint.
|
|
1015 void CMSCollector::direct_allocated(HeapWord* start, size_t size) {
|
|
1016 assert(_markBitMap.covers(start, size), "Out of bounds");
|
|
1017 if (_collectorState >= Marking) {
|
|
1018 MutexLockerEx y(_markBitMap.lock(),
|
|
1019 Mutex::_no_safepoint_check_flag);
|
|
1020 // [see comments preceding SweepClosure::do_blk() below for details]
|
|
1021 // 1. need to mark the object as live so it isn't collected
|
|
1022 // 2. need to mark the 2nd bit to indicate the object may be uninitialized
|
|
1023 // 3. need to mark the end of the object so sweeper can skip over it
|
|
1024 // if it's uninitialized when the sweeper reaches it.
|
|
1025 _markBitMap.mark(start); // object is live
|
|
1026 _markBitMap.mark(start + 1); // object is potentially uninitialized?
|
|
1027 _markBitMap.mark(start + size - 1);
|
|
1028 // mark end of object
|
|
1029 }
|
|
1030 // check that oop looks uninitialized
|
|
1031 assert(oop(start)->klass() == NULL, "_klass should be NULL");
|
|
1032 }
|
|
1033
|
|
1034 void CMSCollector::promoted(bool par, HeapWord* start,
|
|
1035 bool is_obj_array, size_t obj_size) {
|
|
1036 assert(_markBitMap.covers(start), "Out of bounds");
|
|
1037 // See comment in direct_allocated() about when objects should
|
|
1038 // be allocated live.
|
|
1039 if (_collectorState >= Marking) {
|
|
1040 // we already hold the marking bit map lock, taken in
|
|
1041 // the prologue
|
|
1042 if (par) {
|
|
1043 _markBitMap.par_mark(start);
|
|
1044 } else {
|
|
1045 _markBitMap.mark(start);
|
|
1046 }
|
|
1047 // We don't need to mark the object as uninitialized (as
|
|
1048 // in direct_allocated above) because this is being done with the
|
|
1049 // world stopped and the object will be initialized by the
|
|
1050 // time the sweeper gets to look at it.
|
|
1051 assert(SafepointSynchronize::is_at_safepoint(),
|
|
1052 "expect promotion only at safepoints");
|
|
1053
|
|
1054 if (_collectorState < Sweeping) {
|
|
1055 // Mark the appropriate cards in the modUnionTable, so that
|
|
1056 // this object gets scanned before the sweep. If this is
|
|
1057 // not done, CMS generation references in the object might
|
|
1058 // not get marked.
|
|
1059 // For the case of arrays, which are otherwise precisely
|
|
1060 // marked, we need to dirty the entire array, not just its head.
|
|
1061 if (is_obj_array) {
|
|
1062 // The [par_]mark_range() method expects mr.end() below to
|
|
1063 // be aligned to the granularity of a bit's representation
|
|
1064 // in the heap. In the case of the MUT below, that's a
|
|
1065 // card size.
|
|
1066 MemRegion mr(start,
|
|
1067 (HeapWord*)round_to((intptr_t)(start + obj_size),
|
|
1068 CardTableModRefBS::card_size /* bytes */));
|
|
1069 if (par) {
|
|
1070 _modUnionTable.par_mark_range(mr);
|
|
1071 } else {
|
|
1072 _modUnionTable.mark_range(mr);
|
|
1073 }
|
|
1074 } else { // not an obj array; we can just mark the head
|
|
1075 if (par) {
|
|
1076 _modUnionTable.par_mark(start);
|
|
1077 } else {
|
|
1078 _modUnionTable.mark(start);
|
|
1079 }
|
|
1080 }
|
|
1081 }
|
|
1082 }
|
|
1083 }
|
|
1084
|
|
1085 static inline size_t percent_of_space(Space* space, HeapWord* addr)
|
|
1086 {
|
|
1087 size_t delta = pointer_delta(addr, space->bottom());
|
|
1088 return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize));
|
|
1089 }
|
|
1090
|
|
1091 void CMSCollector::icms_update_allocation_limits()
|
|
1092 {
|
|
1093 Generation* gen0 = GenCollectedHeap::heap()->get_gen(0);
|
|
1094 EdenSpace* eden = gen0->as_DefNewGeneration()->eden();
|
|
1095
|
|
1096 const unsigned int duty_cycle = stats().icms_update_duty_cycle();
|
|
1097 if (CMSTraceIncrementalPacing) {
|
|
1098 stats().print();
|
|
1099 }
|
|
1100
|
|
1101 assert(duty_cycle <= 100, "invalid duty cycle");
|
|
1102 if (duty_cycle != 0) {
|
|
1103 // The duty_cycle is a percentage between 0 and 100; convert to words and
|
|
1104 // then compute the offset from the endpoints of the space.
|
|
1105 size_t free_words = eden->free() / HeapWordSize;
|
|
1106 double free_words_dbl = (double)free_words;
|
|
1107 size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0);
|
|
1108 size_t offset_words = (free_words - duty_cycle_words) / 2;
|
|
1109
|
|
1110 _icms_start_limit = eden->top() + offset_words;
|
|
1111 _icms_stop_limit = eden->end() - offset_words;
|
|
1112
|
|
1113 // The limits may be adjusted (shifted to the right) by
|
|
1114 // CMSIncrementalOffset, to allow the application more mutator time after a
|
|
1115 // young gen gc (when all mutators were stopped) and before CMS starts and
|
|
1116 // takes away one or more cpus.
|
|
1117 if (CMSIncrementalOffset != 0) {
|
|
1118 double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0;
|
|
1119 size_t adjustment = (size_t)adjustment_dbl;
|
|
1120 HeapWord* tmp_stop = _icms_stop_limit + adjustment;
|
|
1121 if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) {
|
|
1122 _icms_start_limit += adjustment;
|
|
1123 _icms_stop_limit = tmp_stop;
|
|
1124 }
|
|
1125 }
|
|
1126 }
|
|
1127 if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) {
|
|
1128 _icms_start_limit = _icms_stop_limit = eden->end();
|
|
1129 }
|
|
1130
|
|
1131 // Install the new start limit.
|
|
1132 eden->set_soft_end(_icms_start_limit);
|
|
1133
|
|
1134 if (CMSTraceIncrementalMode) {
|
|
1135 gclog_or_tty->print(" icms alloc limits: "
|
|
1136 PTR_FORMAT "," PTR_FORMAT
|
|
1137 " (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ",
|
|
1138 _icms_start_limit, _icms_stop_limit,
|
|
1139 percent_of_space(eden, _icms_start_limit),
|
|
1140 percent_of_space(eden, _icms_stop_limit));
|
|
1141 if (Verbose) {
|
|
1142 gclog_or_tty->print("eden: ");
|
|
1143 eden->print_on(gclog_or_tty);
|
|
1144 }
|
|
1145 }
|
|
1146 }
|
|
1147
|
|
1148 // Any changes here should try to maintain the invariant
|
|
1149 // that if this method is called with _icms_start_limit
|
|
1150 // and _icms_stop_limit both NULL, then it should return NULL
|
|
1151 // and not notify the icms thread.
|
|
1152 HeapWord*
|
|
1153 CMSCollector::allocation_limit_reached(Space* space, HeapWord* top,
|
|
1154 size_t word_size)
|
|
1155 {
|
|
1156 // A start_limit equal to end() means the duty cycle is 0, so treat that as a
|
|
1157 // nop.
|
|
1158 if (CMSIncrementalMode && _icms_start_limit != space->end()) {
|
|
1159 if (top <= _icms_start_limit) {
|
|
1160 if (CMSTraceIncrementalMode) {
|
|
1161 space->print_on(gclog_or_tty);
|
|
1162 gclog_or_tty->stamp();
|
|
1163 gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT
|
|
1164 ", new limit=" PTR_FORMAT
|
|
1165 " (" SIZE_FORMAT "%%)",
|
|
1166 top, _icms_stop_limit,
|
|
1167 percent_of_space(space, _icms_stop_limit));
|
|
1168 }
|
|
1169 ConcurrentMarkSweepThread::start_icms();
|
|
1170 assert(top < _icms_stop_limit, "Tautology");
|
|
1171 if (word_size < pointer_delta(_icms_stop_limit, top)) {
|
|
1172 return _icms_stop_limit;
|
|
1173 }
|
|
1174
|
|
1175 // The allocation will cross both the _start and _stop limits, so do the
|
|
1176 // stop notification also and return end().
|
|
1177 if (CMSTraceIncrementalMode) {
|
|
1178 space->print_on(gclog_or_tty);
|
|
1179 gclog_or_tty->stamp();
|
|
1180 gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT
|
|
1181 ", new limit=" PTR_FORMAT
|
|
1182 " (" SIZE_FORMAT "%%)",
|
|
1183 top, space->end(),
|
|
1184 percent_of_space(space, space->end()));
|
|
1185 }
|
|
1186 ConcurrentMarkSweepThread::stop_icms();
|
|
1187 return space->end();
|
|
1188 }
|
|
1189
|
|
1190 if (top <= _icms_stop_limit) {
|
|
1191 if (CMSTraceIncrementalMode) {
|
|
1192 space->print_on(gclog_or_tty);
|
|
1193 gclog_or_tty->stamp();
|
|
1194 gclog_or_tty->print_cr(" stop limit top=" PTR_FORMAT
|
|
1195 ", new limit=" PTR_FORMAT
|
|
1196 " (" SIZE_FORMAT "%%)",
|
|
1197 top, space->end(),
|
|
1198 percent_of_space(space, space->end()));
|
|
1199 }
|
|
1200 ConcurrentMarkSweepThread::stop_icms();
|
|
1201 return space->end();
|
|
1202 }
|
|
1203
|
|
1204 if (CMSTraceIncrementalMode) {
|
|
1205 space->print_on(gclog_or_tty);
|
|
1206 gclog_or_tty->stamp();
|
|
1207 gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT
|
|
1208 ", new limit=" PTR_FORMAT,
|
|
1209 top, NULL);
|
|
1210 }
|
|
1211 }
|
|
1212
|
|
1213 return NULL;
|
|
1214 }
|
|
1215
|
|
1216 oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size, oop* ref) {
|
|
1217 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
|
|
1218 // allocate, copy and if necessary update promoinfo --
|
|
1219 // delegate to underlying space.
|
|
1220 assert_lock_strong(freelistLock());
|
|
1221
|
|
1222 #ifndef PRODUCT
|
|
1223 if (Universe::heap()->promotion_should_fail()) {
|
|
1224 return NULL;
|
|
1225 }
|
|
1226 #endif // #ifndef PRODUCT
|
|
1227
|
|
1228 oop res = _cmsSpace->promote(obj, obj_size, ref);
|
|
1229 if (res == NULL) {
|
|
1230 // expand and retry
|
|
1231 size_t s = _cmsSpace->expansionSpaceRequired(obj_size); // HeapWords
|
|
1232 expand(s*HeapWordSize, MinHeapDeltaBytes,
|
|
1233 CMSExpansionCause::_satisfy_promotion);
|
|
1234 // Since there's currently no next generation, we don't try to promote
|
|
1235 // into a more senior generation.
|
|
1236 assert(next_gen() == NULL, "assumption, based upon which no attempt "
|
|
1237 "is made to pass on a possibly failing "
|
|
1238 "promotion to next generation");
|
|
1239 res = _cmsSpace->promote(obj, obj_size, ref);
|
|
1240 }
|
|
1241 if (res != NULL) {
|
|
1242 // See comment in allocate() about when objects should
|
|
1243 // be allocated live.
|
|
1244 assert(obj->is_oop(), "Will dereference klass pointer below");
|
|
1245 collector()->promoted(false, // Not parallel
|
|
1246 (HeapWord*)res, obj->is_objArray(), obj_size);
|
|
1247 // promotion counters
|
|
1248 NOT_PRODUCT(
|
|
1249 _numObjectsPromoted++;
|
|
1250 _numWordsPromoted +=
|
|
1251 (int)(CompactibleFreeListSpace::adjustObjectSize(obj->size()));
|
|
1252 )
|
|
1253 }
|
|
1254 return res;
|
|
1255 }
|
|
1256
|
|
1257
|
|
1258 HeapWord*
|
|
1259 ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space,
|
|
1260 HeapWord* top,
|
|
1261 size_t word_sz)
|
|
1262 {
|
|
1263 return collector()->allocation_limit_reached(space, top, word_sz);
|
|
1264 }
|
|
1265
|
|
1266 // Things to support parallel young-gen collection.
|
|
1267 oop
|
|
1268 ConcurrentMarkSweepGeneration::par_promote(int thread_num,
|
|
1269 oop old, markOop m,
|
|
1270 size_t word_sz) {
|
|
1271 #ifndef PRODUCT
|
|
1272 if (Universe::heap()->promotion_should_fail()) {
|
|
1273 return NULL;
|
|
1274 }
|
|
1275 #endif // #ifndef PRODUCT
|
|
1276
|
|
1277 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num];
|
|
1278 PromotionInfo* promoInfo = &ps->promo;
|
|
1279 // if we are tracking promotions, then first ensure space for
|
|
1280 // promotion (including spooling space for saving header if necessary).
|
|
1281 // then allocate and copy, then track promoted info if needed.
|
|
1282 // When tracking (see PromotionInfo::track()), the mark word may
|
|
1283 // be displaced and in this case restoration of the mark word
|
|
1284 // occurs in the (oop_since_save_marks_)iterate phase.
|
|
1285 if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) {
|
|
1286 // Out of space for allocating spooling buffers;
|
|
1287 // try expanding and allocating spooling buffers.
|
|
1288 if (!expand_and_ensure_spooling_space(promoInfo)) {
|
|
1289 return NULL;
|
|
1290 }
|
|
1291 }
|
|
1292 assert(promoInfo->has_spooling_space(), "Control point invariant");
|
|
1293 HeapWord* obj_ptr = ps->lab.alloc(word_sz);
|
|
1294 if (obj_ptr == NULL) {
|
|
1295 obj_ptr = expand_and_par_lab_allocate(ps, word_sz);
|
|
1296 if (obj_ptr == NULL) {
|
|
1297 return NULL;
|
|
1298 }
|
|
1299 }
|
|
1300 oop obj = oop(obj_ptr);
|
|
1301 assert(obj->klass() == NULL, "Object should be uninitialized here.");
|
|
1302 // Otherwise, copy the object. Here we must be careful to insert the
|
|
1303 // klass pointer last, since this marks the block as an allocated object.
|
|
1304 HeapWord* old_ptr = (HeapWord*)old;
|
|
1305 if (word_sz > (size_t)oopDesc::header_size()) {
|
|
1306 Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(),
|
|
1307 obj_ptr + oopDesc::header_size(),
|
|
1308 word_sz - oopDesc::header_size());
|
|
1309 }
|
|
1310 // Restore the mark word copied above.
|
|
1311 obj->set_mark(m);
|
|
1312 // Now we can track the promoted object, if necessary. We take care
|
|
1313 // To delay the transition from uninitialized to full object
|
|
1314 // (i.e., insertion of klass pointer) until after, so that it
|
|
1315 // atomically becomes a promoted object.
|
|
1316 if (promoInfo->tracking()) {
|
|
1317 promoInfo->track((PromotedObject*)obj, old->klass());
|
|
1318 }
|
|
1319 // Finally, install the klass pointer.
|
|
1320 obj->set_klass(old->klass());
|
|
1321
|
|
1322 assert(old->is_oop(), "Will dereference klass ptr below");
|
|
1323 collector()->promoted(true, // parallel
|
|
1324 obj_ptr, old->is_objArray(), word_sz);
|
|
1325
|
|
1326 NOT_PRODUCT(
|
|
1327 Atomic::inc(&_numObjectsPromoted);
|
|
1328 Atomic::add((jint)CompactibleFreeListSpace::adjustObjectSize(obj->size()),
|
|
1329 &_numWordsPromoted);
|
|
1330 )
|
|
1331
|
|
1332 return obj;
|
|
1333 }
|
|
1334
|
|
1335 void
|
|
1336 ConcurrentMarkSweepGeneration::
|
|
1337 par_promote_alloc_undo(int thread_num,
|
|
1338 HeapWord* obj, size_t word_sz) {
|
|
1339 // CMS does not support promotion undo.
|
|
1340 ShouldNotReachHere();
|
|
1341 }
|
|
1342
|
|
1343 void
|
|
1344 ConcurrentMarkSweepGeneration::
|
|
1345 par_promote_alloc_done(int thread_num) {
|
|
1346 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num];
|
|
1347 ps->lab.retire();
|
|
1348 #if CFLS_LAB_REFILL_STATS
|
|
1349 if (thread_num == 0) {
|
|
1350 _cmsSpace->print_par_alloc_stats();
|
|
1351 }
|
|
1352 #endif
|
|
1353 }
|
|
1354
|
|
1355 void
|
|
1356 ConcurrentMarkSweepGeneration::
|
|
1357 par_oop_since_save_marks_iterate_done(int thread_num) {
|
|
1358 CMSParGCThreadState* ps = _par_gc_thread_states[thread_num];
|
|
1359 ParScanWithoutBarrierClosure* dummy_cl = NULL;
|
|
1360 ps->promo.promoted_oops_iterate_nv(dummy_cl);
|
|
1361 }
|
|
1362
|
|
1363 // XXXPERM
|
|
1364 bool ConcurrentMarkSweepGeneration::should_collect(bool full,
|
|
1365 size_t size,
|
|
1366 bool tlab)
|
|
1367 {
|
|
1368 // We allow a STW collection only if a full
|
|
1369 // collection was requested.
|
|
1370 return full || should_allocate(size, tlab); // FIX ME !!!
|
|
1371 // This and promotion failure handling are connected at the
|
|
1372 // hip and should be fixed by untying them.
|
|
1373 }
|
|
1374
|
|
1375 bool CMSCollector::shouldConcurrentCollect() {
|
|
1376 if (_full_gc_requested) {
|
|
1377 assert(ExplicitGCInvokesConcurrent, "Unexpected state");
|
|
1378 if (Verbose && PrintGCDetails) {
|
|
1379 gclog_or_tty->print_cr("CMSCollector: collect because of explicit "
|
|
1380 " gc request");
|
|
1381 }
|
|
1382 return true;
|
|
1383 }
|
|
1384
|
|
1385 // For debugging purposes, change the type of collection.
|
|
1386 // If the rotation is not on the concurrent collection
|
|
1387 // type, don't start a concurrent collection.
|
|
1388 NOT_PRODUCT(
|
|
1389 if (RotateCMSCollectionTypes &&
|
|
1390 (_cmsGen->debug_collection_type() !=
|
|
1391 ConcurrentMarkSweepGeneration::Concurrent_collection_type)) {
|
|
1392 assert(_cmsGen->debug_collection_type() !=
|
|
1393 ConcurrentMarkSweepGeneration::Unknown_collection_type,
|
|
1394 "Bad cms collection type");
|
|
1395 return false;
|
|
1396 }
|
|
1397 )
|
|
1398
|
|
1399 FreelistLocker x(this);
|
|
1400 // ------------------------------------------------------------------
|
|
1401 // Print out lots of information which affects the initiation of
|
|
1402 // a collection.
|
|
1403 if (PrintCMSInitiationStatistics && stats().valid()) {
|
|
1404 gclog_or_tty->print("CMSCollector shouldConcurrentCollect: ");
|
|
1405 gclog_or_tty->stamp();
|
|
1406 gclog_or_tty->print_cr("");
|
|
1407 stats().print_on(gclog_or_tty);
|
|
1408 gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f",
|
|
1409 stats().time_until_cms_gen_full());
|
|
1410 gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free());
|
|
1411 gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT,
|
|
1412 _cmsGen->contiguous_available());
|
|
1413 gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate());
|
|
1414 gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate());
|
|
1415 gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy());
|
|
1416 gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", initiatingOccupancy());
|
|
1417 }
|
|
1418 // ------------------------------------------------------------------
|
|
1419
|
|
1420 // If the estimated time to complete a cms collection (cms_duration())
|
|
1421 // is less than the estimated time remaining until the cms generation
|
|
1422 // is full, start a collection.
|
|
1423 if (!UseCMSInitiatingOccupancyOnly) {
|
|
1424 if (stats().valid()) {
|
|
1425 if (stats().time_until_cms_start() == 0.0) {
|
|
1426 return true;
|
|
1427 }
|
|
1428 } else {
|
|
1429 // We want to conservatively collect somewhat early in order
|
|
1430 // to try and "bootstrap" our CMS/promotion statistics;
|
|
1431 // this branch will not fire after the first successful CMS
|
|
1432 // collection because the stats should then be valid.
|
|
1433 if (_cmsGen->occupancy() >= _bootstrap_occupancy) {
|
|
1434 if (Verbose && PrintGCDetails) {
|
|
1435 gclog_or_tty->print_cr(
|
|
1436 " CMSCollector: collect for bootstrapping statistics:"
|
|
1437 " occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(),
|
|
1438 _bootstrap_occupancy);
|
|
1439 }
|
|
1440 return true;
|
|
1441 }
|
|
1442 }
|
|
1443 }
|
|
1444
|
|
1445 // Otherwise, we start a collection cycle if either the perm gen or
|
|
1446 // old gen want a collection cycle started. Each may use
|
|
1447 // an appropriate criterion for making this decision.
|
|
1448 // XXX We need to make sure that the gen expansion
|
|
1449 // criterion dovetails well with this.
|
|
1450 if (_cmsGen->shouldConcurrentCollect(initiatingOccupancy())) {
|
|
1451 if (Verbose && PrintGCDetails) {
|
|
1452 gclog_or_tty->print_cr("CMS old gen initiated");
|
|
1453 }
|
|
1454 return true;
|
|
1455 }
|
|
1456
|
|
1457 if (cms_should_unload_classes() &&
|
|
1458 _permGen->shouldConcurrentCollect(initiatingOccupancy())) {
|
|
1459 if (Verbose && PrintGCDetails) {
|
|
1460 gclog_or_tty->print_cr("CMS perm gen initiated");
|
|
1461 }
|
|
1462 return true;
|
|
1463 }
|
|
1464
|
|
1465 return false;
|
|
1466 }
|
|
1467
|
|
1468 // Clear _expansion_cause fields of constituent generations
|
|
1469 void CMSCollector::clear_expansion_cause() {
|
|
1470 _cmsGen->clear_expansion_cause();
|
|
1471 _permGen->clear_expansion_cause();
|
|
1472 }
|
|
1473
|
|
1474 bool ConcurrentMarkSweepGeneration::shouldConcurrentCollect(
|
|
1475 double initiatingOccupancy) {
|
|
1476 // We should be conservative in starting a collection cycle. To
|
|
1477 // start too eagerly runs the risk of collecting too often in the
|
|
1478 // extreme. To collect too rarely falls back on full collections,
|
|
1479 // which works, even if not optimum in terms of concurrent work.
|
|
1480 // As a work around for too eagerly collecting, use the flag
|
|
1481 // UseCMSInitiatingOccupancyOnly. This also has the advantage of
|
|
1482 // giving the user an easily understandable way of controlling the
|
|
1483 // collections.
|
|
1484 // We want to start a new collection cycle if any of the following
|
|
1485 // conditions hold:
|
|
1486 // . our current occupancy exceeds the initiating occupancy, or
|
|
1487 // . we recently needed to expand and have not since that expansion,
|
|
1488 // collected, or
|
|
1489 // . we are not using adaptive free lists and linear allocation is
|
|
1490 // going to fail, or
|
|
1491 // . (for old gen) incremental collection has already failed or
|
|
1492 // may soon fail in the near future as we may not be able to absorb
|
|
1493 // promotions.
|
|
1494 assert_lock_strong(freelistLock());
|
|
1495
|
|
1496 if (occupancy() > initiatingOccupancy) {
|
|
1497 if (PrintGCDetails && Verbose) {
|
|
1498 gclog_or_tty->print(" %s: collect because of occupancy %f / %f ",
|
|
1499 short_name(), occupancy(), initiatingOccupancy);
|
|
1500 }
|
|
1501 return true;
|
|
1502 }
|
|
1503 if (UseCMSInitiatingOccupancyOnly) {
|
|
1504 return false;
|
|
1505 }
|
|
1506 if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) {
|
|
1507 if (PrintGCDetails && Verbose) {
|
|
1508 gclog_or_tty->print(" %s: collect because expanded for allocation ",
|
|
1509 short_name());
|
|
1510 }
|
|
1511 return true;
|
|
1512 }
|
|
1513 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
1514 assert(gch->collector_policy()->is_two_generation_policy(),
|
|
1515 "You may want to check the correctness of the following");
|
|
1516 if (gch->incremental_collection_will_fail()) {
|
|
1517 if (PrintGCDetails && Verbose) {
|
|
1518 gclog_or_tty->print(" %s: collect because incremental collection will fail ",
|
|
1519 short_name());
|
|
1520 }
|
|
1521 return true;
|
|
1522 }
|
|
1523 if (!_cmsSpace->adaptive_freelists() &&
|
|
1524 _cmsSpace->linearAllocationWouldFail()) {
|
|
1525 if (PrintGCDetails && Verbose) {
|
|
1526 gclog_or_tty->print(" %s: collect because of linAB ",
|
|
1527 short_name());
|
|
1528 }
|
|
1529 return true;
|
|
1530 }
|
|
1531 return false;
|
|
1532 }
|
|
1533
|
|
1534 void ConcurrentMarkSweepGeneration::collect(bool full,
|
|
1535 bool clear_all_soft_refs,
|
|
1536 size_t size,
|
|
1537 bool tlab)
|
|
1538 {
|
|
1539 collector()->collect(full, clear_all_soft_refs, size, tlab);
|
|
1540 }
|
|
1541
|
|
1542 void CMSCollector::collect(bool full,
|
|
1543 bool clear_all_soft_refs,
|
|
1544 size_t size,
|
|
1545 bool tlab)
|
|
1546 {
|
|
1547 if (!UseCMSCollectionPassing && _collectorState > Idling) {
|
|
1548 // For debugging purposes skip the collection if the state
|
|
1549 // is not currently idle
|
|
1550 if (TraceCMSState) {
|
|
1551 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d",
|
|
1552 Thread::current(), full, _collectorState);
|
|
1553 }
|
|
1554 return;
|
|
1555 }
|
|
1556
|
|
1557 // The following "if" branch is present for defensive reasons.
|
|
1558 // In the current uses of this interface, it can be replaced with:
|
|
1559 // assert(!GC_locker.is_active(), "Can't be called otherwise");
|
|
1560 // But I am not placing that assert here to allow future
|
|
1561 // generality in invoking this interface.
|
|
1562 if (GC_locker::is_active()) {
|
|
1563 // A consistency test for GC_locker
|
|
1564 assert(GC_locker::needs_gc(), "Should have been set already");
|
|
1565 // Skip this foreground collection, instead
|
|
1566 // expanding the heap if necessary.
|
|
1567 // Need the free list locks for the call to free() in compute_new_size()
|
|
1568 compute_new_size();
|
|
1569 return;
|
|
1570 }
|
|
1571 acquire_control_and_collect(full, clear_all_soft_refs);
|
|
1572 _full_gcs_since_conc_gc++;
|
|
1573
|
|
1574 }
|
|
1575
|
|
1576 void CMSCollector::request_full_gc(unsigned int full_gc_count) {
|
|
1577 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
1578 unsigned int gc_count = gch->total_full_collections();
|
|
1579 if (gc_count == full_gc_count) {
|
|
1580 MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag);
|
|
1581 _full_gc_requested = true;
|
|
1582 CGC_lock->notify(); // nudge CMS thread
|
|
1583 }
|
|
1584 }
|
|
1585
|
|
1586
|
|
1587 // The foreground and background collectors need to coordinate in order
|
|
1588 // to make sure that they do not mutually interfere with CMS collections.
|
|
1589 // When a background collection is active,
|
|
1590 // the foreground collector may need to take over (preempt) and
|
|
1591 // synchronously complete an ongoing collection. Depending on the
|
|
1592 // frequency of the background collections and the heap usage
|
|
1593 // of the application, this preemption can be seldom or frequent.
|
|
1594 // There are only certain
|
|
1595 // points in the background collection that the "collection-baton"
|
|
1596 // can be passed to the foreground collector.
|
|
1597 //
|
|
1598 // The foreground collector will wait for the baton before
|
|
1599 // starting any part of the collection. The foreground collector
|
|
1600 // will only wait at one location.
|
|
1601 //
|
|
1602 // The background collector will yield the baton before starting a new
|
|
1603 // phase of the collection (e.g., before initial marking, marking from roots,
|
|
1604 // precleaning, final re-mark, sweep etc.) This is normally done at the head
|
|
1605 // of the loop which switches the phases. The background collector does some
|
|
1606 // of the phases (initial mark, final re-mark) with the world stopped.
|
|
1607 // Because of locking involved in stopping the world,
|
|
1608 // the foreground collector should not block waiting for the background
|
|
1609 // collector when it is doing a stop-the-world phase. The background
|
|
1610 // collector will yield the baton at an additional point just before
|
|
1611 // it enters a stop-the-world phase. Once the world is stopped, the
|
|
1612 // background collector checks the phase of the collection. If the
|
|
1613 // phase has not changed, it proceeds with the collection. If the
|
|
1614 // phase has changed, it skips that phase of the collection. See
|
|
1615 // the comments on the use of the Heap_lock in collect_in_background().
|
|
1616 //
|
|
1617 // Variable used in baton passing.
|
|
1618 // _foregroundGCIsActive - Set to true by the foreground collector when
|
|
1619 // it wants the baton. The foreground clears it when it has finished
|
|
1620 // the collection.
|
|
1621 // _foregroundGCShouldWait - Set to true by the background collector
|
|
1622 // when it is running. The foreground collector waits while
|
|
1623 // _foregroundGCShouldWait is true.
|
|
1624 // CGC_lock - monitor used to protect access to the above variables
|
|
1625 // and to notify the foreground and background collectors.
|
|
1626 // _collectorState - current state of the CMS collection.
|
|
1627 //
|
|
1628 // The foreground collector
|
|
1629 // acquires the CGC_lock
|
|
1630 // sets _foregroundGCIsActive
|
|
1631 // waits on the CGC_lock for _foregroundGCShouldWait to be false
|
|
1632 // various locks acquired in preparation for the collection
|
|
1633 // are released so as not to block the background collector
|
|
1634 // that is in the midst of a collection
|
|
1635 // proceeds with the collection
|
|
1636 // clears _foregroundGCIsActive
|
|
1637 // returns
|
|
1638 //
|
|
1639 // The background collector in a loop iterating on the phases of the
|
|
1640 // collection
|
|
1641 // acquires the CGC_lock
|
|
1642 // sets _foregroundGCShouldWait
|
|
1643 // if _foregroundGCIsActive is set
|
|
1644 // clears _foregroundGCShouldWait, notifies _CGC_lock
|
|
1645 // waits on _CGC_lock for _foregroundGCIsActive to become false
|
|
1646 // and exits the loop.
|
|
1647 // otherwise
|
|
1648 // proceed with that phase of the collection
|
|
1649 // if the phase is a stop-the-world phase,
|
|
1650 // yield the baton once more just before enqueueing
|
|
1651 // the stop-world CMS operation (executed by the VM thread).
|
|
1652 // returns after all phases of the collection are done
|
|
1653 //
|
|
1654
|
|
1655 void CMSCollector::acquire_control_and_collect(bool full,
|
|
1656 bool clear_all_soft_refs) {
|
|
1657 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
|
|
1658 assert(!Thread::current()->is_ConcurrentGC_thread(),
|
|
1659 "shouldn't try to acquire control from self!");
|
|
1660
|
|
1661 // Start the protocol for acquiring control of the
|
|
1662 // collection from the background collector (aka CMS thread).
|
|
1663 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(),
|
|
1664 "VM thread should have CMS token");
|
|
1665 // Remember the possibly interrupted state of an ongoing
|
|
1666 // concurrent collection
|
|
1667 CollectorState first_state = _collectorState;
|
|
1668
|
|
1669 // Signal to a possibly ongoing concurrent collection that
|
|
1670 // we want to do a foreground collection.
|
|
1671 _foregroundGCIsActive = true;
|
|
1672
|
|
1673 // Disable incremental mode during a foreground collection.
|
|
1674 ICMSDisabler icms_disabler;
|
|
1675
|
|
1676 // release locks and wait for a notify from the background collector
|
|
1677 // releasing the locks in only necessary for phases which
|
|
1678 // do yields to improve the granularity of the collection.
|
|
1679 assert_lock_strong(bitMapLock());
|
|
1680 // We need to lock the Free list lock for the space that we are
|
|
1681 // currently collecting.
|
|
1682 assert(haveFreelistLocks(), "Must be holding free list locks");
|
|
1683 bitMapLock()->unlock();
|
|
1684 releaseFreelistLocks();
|
|
1685 {
|
|
1686 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
|
|
1687 if (_foregroundGCShouldWait) {
|
|
1688 // We are going to be waiting for action for the CMS thread;
|
|
1689 // it had better not be gone (for instance at shutdown)!
|
|
1690 assert(ConcurrentMarkSweepThread::cmst() != NULL,
|
|
1691 "CMS thread must be running");
|
|
1692 // Wait here until the background collector gives us the go-ahead
|
|
1693 ConcurrentMarkSweepThread::clear_CMS_flag(
|
|
1694 ConcurrentMarkSweepThread::CMS_vm_has_token); // release token
|
|
1695 // Get a possibly blocked CMS thread going:
|
|
1696 // Note that we set _foregroundGCIsActive true above,
|
|
1697 // without protection of the CGC_lock.
|
|
1698 CGC_lock->notify();
|
|
1699 assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(),
|
|
1700 "Possible deadlock");
|
|
1701 while (_foregroundGCShouldWait) {
|
|
1702 // wait for notification
|
|
1703 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
|
|
1704 // Possibility of delay/starvation here, since CMS token does
|
|
1705 // not know to give priority to VM thread? Actually, i think
|
|
1706 // there wouldn't be any delay/starvation, but the proof of
|
|
1707 // that "fact" (?) appears non-trivial. XXX 20011219YSR
|
|
1708 }
|
|
1709 ConcurrentMarkSweepThread::set_CMS_flag(
|
|
1710 ConcurrentMarkSweepThread::CMS_vm_has_token);
|
|
1711 }
|
|
1712 }
|
|
1713 // The CMS_token is already held. Get back the other locks.
|
|
1714 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(),
|
|
1715 "VM thread should have CMS token");
|
|
1716 getFreelistLocks();
|
|
1717 bitMapLock()->lock_without_safepoint_check();
|
|
1718 if (TraceCMSState) {
|
|
1719 gclog_or_tty->print_cr("CMS foreground collector has asked for control "
|
|
1720 INTPTR_FORMAT " with first state %d", Thread::current(), first_state);
|
|
1721 gclog_or_tty->print_cr(" gets control with state %d", _collectorState);
|
|
1722 }
|
|
1723
|
|
1724 // Check if we need to do a compaction, or if not, whether
|
|
1725 // we need to start the mark-sweep from scratch.
|
|
1726 bool should_compact = false;
|
|
1727 bool should_start_over = false;
|
|
1728 decide_foreground_collection_type(clear_all_soft_refs,
|
|
1729 &should_compact, &should_start_over);
|
|
1730
|
|
1731 NOT_PRODUCT(
|
|
1732 if (RotateCMSCollectionTypes) {
|
|
1733 if (_cmsGen->debug_collection_type() ==
|
|
1734 ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) {
|
|
1735 should_compact = true;
|
|
1736 } else if (_cmsGen->debug_collection_type() ==
|
|
1737 ConcurrentMarkSweepGeneration::MS_foreground_collection_type) {
|
|
1738 should_compact = false;
|
|
1739 }
|
|
1740 }
|
|
1741 )
|
|
1742
|
|
1743 if (PrintGCDetails && first_state > Idling) {
|
|
1744 GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause();
|
|
1745 if (GCCause::is_user_requested_gc(cause) ||
|
|
1746 GCCause::is_serviceability_requested_gc(cause)) {
|
|
1747 gclog_or_tty->print(" (concurrent mode interrupted)");
|
|
1748 } else {
|
|
1749 gclog_or_tty->print(" (concurrent mode failure)");
|
|
1750 }
|
|
1751 }
|
|
1752
|
|
1753 if (should_compact) {
|
|
1754 // If the collection is being acquired from the background
|
|
1755 // collector, there may be references on the discovered
|
|
1756 // references lists that have NULL referents (being those
|
|
1757 // that were concurrently cleared by a mutator) or
|
|
1758 // that are no longer active (having been enqueued concurrently
|
|
1759 // by the mutator).
|
|
1760 // Scrub the list of those references because Mark-Sweep-Compact
|
|
1761 // code assumes referents are not NULL and that all discovered
|
|
1762 // Reference objects are active.
|
|
1763 ref_processor()->clean_up_discovered_references();
|
|
1764
|
|
1765 do_compaction_work(clear_all_soft_refs);
|
|
1766
|
|
1767 // Has the GC time limit been exceeded?
|
|
1768 check_gc_time_limit();
|
|
1769
|
|
1770 } else {
|
|
1771 do_mark_sweep_work(clear_all_soft_refs, first_state,
|
|
1772 should_start_over);
|
|
1773 }
|
|
1774 // Reset the expansion cause, now that we just completed
|
|
1775 // a collection cycle.
|
|
1776 clear_expansion_cause();
|
|
1777 _foregroundGCIsActive = false;
|
|
1778 return;
|
|
1779 }
|
|
1780
|
|
1781 void CMSCollector::check_gc_time_limit() {
|
|
1782
|
|
1783 // Ignore explicit GC's. Exiting here does not set the flag and
|
|
1784 // does not reset the count. Updating of the averages for system
|
|
1785 // GC's is still controlled by UseAdaptiveSizePolicyWithSystemGC.
|
|
1786 GCCause::Cause gc_cause = GenCollectedHeap::heap()->gc_cause();
|
|
1787 if (GCCause::is_user_requested_gc(gc_cause) ||
|
|
1788 GCCause::is_serviceability_requested_gc(gc_cause)) {
|
|
1789 return;
|
|
1790 }
|
|
1791
|
|
1792 // Calculate the fraction of the CMS generation was freed during
|
|
1793 // the last collection.
|
|
1794 // Only consider the STW compacting cost for now.
|
|
1795 //
|
|
1796 // Note that the gc time limit test only works for the collections
|
|
1797 // of the young gen + tenured gen and not for collections of the
|
|
1798 // permanent gen. That is because the calculation of the space
|
|
1799 // freed by the collection is the free space in the young gen +
|
|
1800 // tenured gen.
|
|
1801
|
|
1802 double fraction_free =
|
|
1803 ((double)_cmsGen->free())/((double)_cmsGen->max_capacity());
|
|
1804 if ((100.0 * size_policy()->compacting_gc_cost()) >
|
|
1805 ((double) GCTimeLimit) &&
|
|
1806 ((fraction_free * 100) < GCHeapFreeLimit)) {
|
|
1807 size_policy()->inc_gc_time_limit_count();
|
|
1808 if (UseGCOverheadLimit &&
|
|
1809 (size_policy()->gc_time_limit_count() >
|
|
1810 AdaptiveSizePolicyGCTimeLimitThreshold)) {
|
|
1811 size_policy()->set_gc_time_limit_exceeded(true);
|
|
1812 // Avoid consecutive OOM due to the gc time limit by resetting
|
|
1813 // the counter.
|
|
1814 size_policy()->reset_gc_time_limit_count();
|
|
1815 if (PrintGCDetails) {
|
|
1816 gclog_or_tty->print_cr(" GC is exceeding overhead limit "
|
|
1817 "of %d%%", GCTimeLimit);
|
|
1818 }
|
|
1819 } else {
|
|
1820 if (PrintGCDetails) {
|
|
1821 gclog_or_tty->print_cr(" GC would exceed overhead limit "
|
|
1822 "of %d%%", GCTimeLimit);
|
|
1823 }
|
|
1824 }
|
|
1825 } else {
|
|
1826 size_policy()->reset_gc_time_limit_count();
|
|
1827 }
|
|
1828 }
|
|
1829
|
|
1830 // Resize the perm generation and the tenured generation
|
|
1831 // after obtaining the free list locks for the
|
|
1832 // two generations.
|
|
1833 void CMSCollector::compute_new_size() {
|
|
1834 assert_locked_or_safepoint(Heap_lock);
|
|
1835 FreelistLocker z(this);
|
|
1836 _permGen->compute_new_size();
|
|
1837 _cmsGen->compute_new_size();
|
|
1838 }
|
|
1839
|
|
1840 // A work method used by foreground collection to determine
|
|
1841 // what type of collection (compacting or not, continuing or fresh)
|
|
1842 // it should do.
|
|
1843 // NOTE: the intent is to make UseCMSCompactAtFullCollection
|
|
1844 // and CMSCompactWhenClearAllSoftRefs the default in the future
|
|
1845 // and do away with the flags after a suitable period.
|
|
1846 void CMSCollector::decide_foreground_collection_type(
|
|
1847 bool clear_all_soft_refs, bool* should_compact,
|
|
1848 bool* should_start_over) {
|
|
1849 // Normally, we'll compact only if the UseCMSCompactAtFullCollection
|
|
1850 // flag is set, and we have either requested a System.gc() or
|
|
1851 // the number of full gc's since the last concurrent cycle
|
|
1852 // has exceeded the threshold set by CMSFullGCsBeforeCompaction,
|
|
1853 // or if an incremental collection has failed
|
|
1854 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
1855 assert(gch->collector_policy()->is_two_generation_policy(),
|
|
1856 "You may want to check the correctness of the following");
|
|
1857 // Inform cms gen if this was due to partial collection failing.
|
|
1858 // The CMS gen may use this fact to determine its expansion policy.
|
|
1859 if (gch->incremental_collection_will_fail()) {
|
|
1860 assert(!_cmsGen->incremental_collection_failed(),
|
|
1861 "Should have been noticed, reacted to and cleared");
|
|
1862 _cmsGen->set_incremental_collection_failed();
|
|
1863 }
|
|
1864 *should_compact =
|
|
1865 UseCMSCompactAtFullCollection &&
|
|
1866 ((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) ||
|
|
1867 GCCause::is_user_requested_gc(gch->gc_cause()) ||
|
|
1868 gch->incremental_collection_will_fail());
|
|
1869 *should_start_over = false;
|
|
1870 if (clear_all_soft_refs && !*should_compact) {
|
|
1871 // We are about to do a last ditch collection attempt
|
|
1872 // so it would normally make sense to do a compaction
|
|
1873 // to reclaim as much space as possible.
|
|
1874 if (CMSCompactWhenClearAllSoftRefs) {
|
|
1875 // Default: The rationale is that in this case either
|
|
1876 // we are past the final marking phase, in which case
|
|
1877 // we'd have to start over, or so little has been done
|
|
1878 // that there's little point in saving that work. Compaction
|
|
1879 // appears to be the sensible choice in either case.
|
|
1880 *should_compact = true;
|
|
1881 } else {
|
|
1882 // We have been asked to clear all soft refs, but not to
|
|
1883 // compact. Make sure that we aren't past the final checkpoint
|
|
1884 // phase, for that is where we process soft refs. If we are already
|
|
1885 // past that phase, we'll need to redo the refs discovery phase and
|
|
1886 // if necessary clear soft refs that weren't previously
|
|
1887 // cleared. We do so by remembering the phase in which
|
|
1888 // we came in, and if we are past the refs processing
|
|
1889 // phase, we'll choose to just redo the mark-sweep
|
|
1890 // collection from scratch.
|
|
1891 if (_collectorState > FinalMarking) {
|
|
1892 // We are past the refs processing phase;
|
|
1893 // start over and do a fresh synchronous CMS cycle
|
|
1894 _collectorState = Resetting; // skip to reset to start new cycle
|
|
1895 reset(false /* == !asynch */);
|
|
1896 *should_start_over = true;
|
|
1897 } // else we can continue a possibly ongoing current cycle
|
|
1898 }
|
|
1899 }
|
|
1900 }
|
|
1901
|
|
1902 // A work method used by the foreground collector to do
|
|
1903 // a mark-sweep-compact.
|
|
1904 void CMSCollector::do_compaction_work(bool clear_all_soft_refs) {
|
|
1905 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
1906 TraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, gclog_or_tty);
|
|
1907 if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) {
|
|
1908 gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d "
|
|
1909 "collections passed to foreground collector", _full_gcs_since_conc_gc);
|
|
1910 }
|
|
1911
|
|
1912 // Sample collection interval time and reset for collection pause.
|
|
1913 if (UseAdaptiveSizePolicy) {
|
|
1914 size_policy()->msc_collection_begin();
|
|
1915 }
|
|
1916
|
|
1917 // Temporarily widen the span of the weak reference processing to
|
|
1918 // the entire heap.
|
|
1919 MemRegion new_span(GenCollectedHeap::heap()->reserved_region());
|
|
1920 ReferenceProcessorSpanMutator x(ref_processor(), new_span);
|
|
1921
|
|
1922 // Temporarily, clear the "is_alive_non_header" field of the
|
|
1923 // reference processor.
|
|
1924 ReferenceProcessorIsAliveMutator y(ref_processor(), NULL);
|
|
1925
|
|
1926 // Temporarily make reference _processing_ single threaded (non-MT).
|
|
1927 ReferenceProcessorMTProcMutator z(ref_processor(), false);
|
|
1928
|
|
1929 // Temporarily make refs discovery atomic
|
|
1930 ReferenceProcessorAtomicMutator w(ref_processor(), true);
|
|
1931
|
|
1932 ref_processor()->set_enqueuing_is_done(false);
|
|
1933 ref_processor()->enable_discovery();
|
|
1934 // If an asynchronous collection finishes, the _modUnionTable is
|
|
1935 // all clear. If we are assuming the collection from an asynchronous
|
|
1936 // collection, clear the _modUnionTable.
|
|
1937 assert(_collectorState != Idling || _modUnionTable.isAllClear(),
|
|
1938 "_modUnionTable should be clear if the baton was not passed");
|
|
1939 _modUnionTable.clear_all();
|
|
1940
|
|
1941 // We must adjust the allocation statistics being maintained
|
|
1942 // in the free list space. We do so by reading and clearing
|
|
1943 // the sweep timer and updating the block flux rate estimates below.
|
|
1944 assert(_sweep_timer.is_active(), "We should never see the timer inactive");
|
|
1945 _sweep_timer.stop();
|
|
1946 // Note that we do not use this sample to update the _sweep_estimate.
|
|
1947 _cmsGen->cmsSpace()->beginSweepFLCensus((float)(_sweep_timer.seconds()),
|
|
1948 _sweep_estimate.padded_average());
|
|
1949
|
|
1950 GenMarkSweep::invoke_at_safepoint(_cmsGen->level(),
|
|
1951 ref_processor(), clear_all_soft_refs);
|
|
1952 #ifdef ASSERT
|
|
1953 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace();
|
|
1954 size_t free_size = cms_space->free();
|
|
1955 assert(free_size ==
|
|
1956 pointer_delta(cms_space->end(), cms_space->compaction_top())
|
|
1957 * HeapWordSize,
|
|
1958 "All the free space should be compacted into one chunk at top");
|
|
1959 assert(cms_space->dictionary()->totalChunkSize(
|
|
1960 debug_only(cms_space->freelistLock())) == 0 ||
|
|
1961 cms_space->totalSizeInIndexedFreeLists() == 0,
|
|
1962 "All the free space should be in a single chunk");
|
|
1963 size_t num = cms_space->totalCount();
|
|
1964 assert((free_size == 0 && num == 0) ||
|
|
1965 (free_size > 0 && (num == 1 || num == 2)),
|
|
1966 "There should be at most 2 free chunks after compaction");
|
|
1967 #endif // ASSERT
|
|
1968 _collectorState = Resetting;
|
|
1969 assert(_restart_addr == NULL,
|
|
1970 "Should have been NULL'd before baton was passed");
|
|
1971 reset(false /* == !asynch */);
|
|
1972 _cmsGen->reset_after_compaction();
|
|
1973
|
|
1974 if (verifying() && !cms_should_unload_classes()) {
|
|
1975 perm_gen_verify_bit_map()->clear_all();
|
|
1976 }
|
|
1977
|
|
1978 // Clear any data recorded in the PLAB chunk arrays.
|
|
1979 if (_survivor_plab_array != NULL) {
|
|
1980 reset_survivor_plab_arrays();
|
|
1981 }
|
|
1982
|
|
1983 // Adjust the per-size allocation stats for the next epoch.
|
|
1984 _cmsGen->cmsSpace()->endSweepFLCensus(sweepCount() /* fake */);
|
|
1985 // Restart the "sweep timer" for next epoch.
|
|
1986 _sweep_timer.reset();
|
|
1987 _sweep_timer.start();
|
|
1988
|
|
1989 // Sample collection pause time and reset for collection interval.
|
|
1990 if (UseAdaptiveSizePolicy) {
|
|
1991 size_policy()->msc_collection_end(gch->gc_cause());
|
|
1992 }
|
|
1993
|
|
1994 // For a mark-sweep-compact, compute_new_size() will be called
|
|
1995 // in the heap's do_collection() method.
|
|
1996 }
|
|
1997
|
|
1998 // A work method used by the foreground collector to do
|
|
1999 // a mark-sweep, after taking over from a possibly on-going
|
|
2000 // concurrent mark-sweep collection.
|
|
2001 void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs,
|
|
2002 CollectorState first_state, bool should_start_over) {
|
|
2003 if (PrintGC && Verbose) {
|
|
2004 gclog_or_tty->print_cr("Pass concurrent collection to foreground "
|
|
2005 "collector with count %d",
|
|
2006 _full_gcs_since_conc_gc);
|
|
2007 }
|
|
2008 switch (_collectorState) {
|
|
2009 case Idling:
|
|
2010 if (first_state == Idling || should_start_over) {
|
|
2011 // The background GC was not active, or should
|
|
2012 // restarted from scratch; start the cycle.
|
|
2013 _collectorState = InitialMarking;
|
|
2014 }
|
|
2015 // If first_state was not Idling, then a background GC
|
|
2016 // was in progress and has now finished. No need to do it
|
|
2017 // again. Leave the state as Idling.
|
|
2018 break;
|
|
2019 case Precleaning:
|
|
2020 // In the foreground case don't do the precleaning since
|
|
2021 // it is not done concurrently and there is extra work
|
|
2022 // required.
|
|
2023 _collectorState = FinalMarking;
|
|
2024 }
|
|
2025 if (PrintGCDetails &&
|
|
2026 (_collectorState > Idling ||
|
|
2027 !GCCause::is_user_requested_gc(GenCollectedHeap::heap()->gc_cause()))) {
|
|
2028 gclog_or_tty->print(" (concurrent mode failure)");
|
|
2029 }
|
|
2030 collect_in_foreground(clear_all_soft_refs);
|
|
2031
|
|
2032 // For a mark-sweep, compute_new_size() will be called
|
|
2033 // in the heap's do_collection() method.
|
|
2034 }
|
|
2035
|
|
2036
|
|
2037 void CMSCollector::getFreelistLocks() const {
|
|
2038 // Get locks for all free lists in all generations that this
|
|
2039 // collector is responsible for
|
|
2040 _cmsGen->freelistLock()->lock_without_safepoint_check();
|
|
2041 _permGen->freelistLock()->lock_without_safepoint_check();
|
|
2042 }
|
|
2043
|
|
2044 void CMSCollector::releaseFreelistLocks() const {
|
|
2045 // Release locks for all free lists in all generations that this
|
|
2046 // collector is responsible for
|
|
2047 _cmsGen->freelistLock()->unlock();
|
|
2048 _permGen->freelistLock()->unlock();
|
|
2049 }
|
|
2050
|
|
2051 bool CMSCollector::haveFreelistLocks() const {
|
|
2052 // Check locks for all free lists in all generations that this
|
|
2053 // collector is responsible for
|
|
2054 assert_lock_strong(_cmsGen->freelistLock());
|
|
2055 assert_lock_strong(_permGen->freelistLock());
|
|
2056 PRODUCT_ONLY(ShouldNotReachHere());
|
|
2057 return true;
|
|
2058 }
|
|
2059
|
|
2060 // A utility class that is used by the CMS collector to
|
|
2061 // temporarily "release" the foreground collector from its
|
|
2062 // usual obligation to wait for the background collector to
|
|
2063 // complete an ongoing phase before proceeding.
|
|
2064 class ReleaseForegroundGC: public StackObj {
|
|
2065 private:
|
|
2066 CMSCollector* _c;
|
|
2067 public:
|
|
2068 ReleaseForegroundGC(CMSCollector* c) : _c(c) {
|
|
2069 assert(_c->_foregroundGCShouldWait, "Else should not need to call");
|
|
2070 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
|
|
2071 // allow a potentially blocked foreground collector to proceed
|
|
2072 _c->_foregroundGCShouldWait = false;
|
|
2073 if (_c->_foregroundGCIsActive) {
|
|
2074 CGC_lock->notify();
|
|
2075 }
|
|
2076 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
2077 "Possible deadlock");
|
|
2078 }
|
|
2079
|
|
2080 ~ReleaseForegroundGC() {
|
|
2081 assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?");
|
|
2082 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
|
|
2083 _c->_foregroundGCShouldWait = true;
|
|
2084 }
|
|
2085 };
|
|
2086
|
|
2087 // There are separate collect_in_background and collect_in_foreground because of
|
|
2088 // the different locking requirements of the background collector and the
|
|
2089 // foreground collector. There was originally an attempt to share
|
|
2090 // one "collect" method between the background collector and the foreground
|
|
2091 // collector but the if-then-else required made it cleaner to have
|
|
2092 // separate methods.
|
|
2093 void CMSCollector::collect_in_background(bool clear_all_soft_refs) {
|
|
2094 assert(Thread::current()->is_ConcurrentGC_thread(),
|
|
2095 "A CMS asynchronous collection is only allowed on a CMS thread.");
|
|
2096
|
|
2097 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
2098 {
|
|
2099 bool safepoint_check = Mutex::_no_safepoint_check_flag;
|
|
2100 MutexLockerEx hl(Heap_lock, safepoint_check);
|
|
2101 MutexLockerEx x(CGC_lock, safepoint_check);
|
|
2102 if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) {
|
|
2103 // The foreground collector is active or we're
|
|
2104 // not using asynchronous collections. Skip this
|
|
2105 // background collection.
|
|
2106 assert(!_foregroundGCShouldWait, "Should be clear");
|
|
2107 return;
|
|
2108 } else {
|
|
2109 assert(_collectorState == Idling, "Should be idling before start.");
|
|
2110 _collectorState = InitialMarking;
|
|
2111 // Reset the expansion cause, now that we are about to begin
|
|
2112 // a new cycle.
|
|
2113 clear_expansion_cause();
|
|
2114 }
|
|
2115 _unloaded_classes_last_cycle = cms_should_unload_classes(); // ... from last cycle
|
|
2116 // This controls class unloading in response to an explicit gc request.
|
|
2117 // If ExplicitGCInvokesConcurrentAndUnloadsClasses is set, then
|
|
2118 // we will unload classes even if CMSClassUnloadingEnabled is not set.
|
|
2119 // See CR 6541037 and related CRs.
|
|
2120 _unload_classes = _full_gc_requested // ... for this cycle
|
|
2121 && ExplicitGCInvokesConcurrentAndUnloadsClasses;
|
|
2122 _full_gc_requested = false; // acks all outstanding full gc requests
|
|
2123 // Signal that we are about to start a collection
|
|
2124 gch->increment_total_full_collections(); // ... starting a collection cycle
|
|
2125 _collection_count_start = gch->total_full_collections();
|
|
2126 }
|
|
2127
|
|
2128 // Used for PrintGC
|
|
2129 size_t prev_used;
|
|
2130 if (PrintGC && Verbose) {
|
|
2131 prev_used = _cmsGen->used(); // XXXPERM
|
|
2132 }
|
|
2133
|
|
2134 // The change of the collection state is normally done at this level;
|
|
2135 // the exceptions are phases that are executed while the world is
|
|
2136 // stopped. For those phases the change of state is done while the
|
|
2137 // world is stopped. For baton passing purposes this allows the
|
|
2138 // background collector to finish the phase and change state atomically.
|
|
2139 // The foreground collector cannot wait on a phase that is done
|
|
2140 // while the world is stopped because the foreground collector already
|
|
2141 // has the world stopped and would deadlock.
|
|
2142 while (_collectorState != Idling) {
|
|
2143 if (TraceCMSState) {
|
|
2144 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d",
|
|
2145 Thread::current(), _collectorState);
|
|
2146 }
|
|
2147 // The foreground collector
|
|
2148 // holds the Heap_lock throughout its collection.
|
|
2149 // holds the CMS token (but not the lock)
|
|
2150 // except while it is waiting for the background collector to yield.
|
|
2151 //
|
|
2152 // The foreground collector should be blocked (not for long)
|
|
2153 // if the background collector is about to start a phase
|
|
2154 // executed with world stopped. If the background
|
|
2155 // collector has already started such a phase, the
|
|
2156 // foreground collector is blocked waiting for the
|
|
2157 // Heap_lock. The stop-world phases (InitialMarking and FinalMarking)
|
|
2158 // are executed in the VM thread.
|
|
2159 //
|
|
2160 // The locking order is
|
|
2161 // PendingListLock (PLL) -- if applicable (FinalMarking)
|
|
2162 // Heap_lock (both this & PLL locked in VM_CMS_Operation::prologue())
|
|
2163 // CMS token (claimed in
|
|
2164 // stop_world_and_do() -->
|
|
2165 // safepoint_synchronize() -->
|
|
2166 // CMSThread::synchronize())
|
|
2167
|
|
2168 {
|
|
2169 // Check if the FG collector wants us to yield.
|
|
2170 CMSTokenSync x(true); // is cms thread
|
|
2171 if (waitForForegroundGC()) {
|
|
2172 // We yielded to a foreground GC, nothing more to be
|
|
2173 // done this round.
|
|
2174 assert(_foregroundGCShouldWait == false, "We set it to false in "
|
|
2175 "waitForForegroundGC()");
|
|
2176 if (TraceCMSState) {
|
|
2177 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT
|
|
2178 " exiting collection CMS state %d",
|
|
2179 Thread::current(), _collectorState);
|
|
2180 }
|
|
2181 return;
|
|
2182 } else {
|
|
2183 // The background collector can run but check to see if the
|
|
2184 // foreground collector has done a collection while the
|
|
2185 // background collector was waiting to get the CGC_lock
|
|
2186 // above. If yes, break so that _foregroundGCShouldWait
|
|
2187 // is cleared before returning.
|
|
2188 if (_collectorState == Idling) {
|
|
2189 break;
|
|
2190 }
|
|
2191 }
|
|
2192 }
|
|
2193
|
|
2194 assert(_foregroundGCShouldWait, "Foreground collector, if active, "
|
|
2195 "should be waiting");
|
|
2196
|
|
2197 switch (_collectorState) {
|
|
2198 case InitialMarking:
|
|
2199 {
|
|
2200 ReleaseForegroundGC x(this);
|
|
2201 stats().record_cms_begin();
|
|
2202
|
|
2203 VM_CMS_Initial_Mark initial_mark_op(this);
|
|
2204 VMThread::execute(&initial_mark_op);
|
|
2205 }
|
|
2206 // The collector state may be any legal state at this point
|
|
2207 // since the background collector may have yielded to the
|
|
2208 // foreground collector.
|
|
2209 break;
|
|
2210 case Marking:
|
|
2211 // initial marking in checkpointRootsInitialWork has been completed
|
|
2212 if (markFromRoots(true)) { // we were successful
|
|
2213 assert(_collectorState == Precleaning, "Collector state should "
|
|
2214 "have changed");
|
|
2215 } else {
|
|
2216 assert(_foregroundGCIsActive, "Internal state inconsistency");
|
|
2217 }
|
|
2218 break;
|
|
2219 case Precleaning:
|
|
2220 if (UseAdaptiveSizePolicy) {
|
|
2221 size_policy()->concurrent_precleaning_begin();
|
|
2222 }
|
|
2223 // marking from roots in markFromRoots has been completed
|
|
2224 preclean();
|
|
2225 if (UseAdaptiveSizePolicy) {
|
|
2226 size_policy()->concurrent_precleaning_end();
|
|
2227 }
|
|
2228 assert(_collectorState == AbortablePreclean ||
|
|
2229 _collectorState == FinalMarking,
|
|
2230 "Collector state should have changed");
|
|
2231 break;
|
|
2232 case AbortablePreclean:
|
|
2233 if (UseAdaptiveSizePolicy) {
|
|
2234 size_policy()->concurrent_phases_resume();
|
|
2235 }
|
|
2236 abortable_preclean();
|
|
2237 if (UseAdaptiveSizePolicy) {
|
|
2238 size_policy()->concurrent_precleaning_end();
|
|
2239 }
|
|
2240 assert(_collectorState == FinalMarking, "Collector state should "
|
|
2241 "have changed");
|
|
2242 break;
|
|
2243 case FinalMarking:
|
|
2244 {
|
|
2245 ReleaseForegroundGC x(this);
|
|
2246
|
|
2247 VM_CMS_Final_Remark final_remark_op(this);
|
|
2248 VMThread::execute(&final_remark_op);
|
|
2249 }
|
|
2250 assert(_foregroundGCShouldWait, "block post-condition");
|
|
2251 break;
|
|
2252 case Sweeping:
|
|
2253 if (UseAdaptiveSizePolicy) {
|
|
2254 size_policy()->concurrent_sweeping_begin();
|
|
2255 }
|
|
2256 // final marking in checkpointRootsFinal has been completed
|
|
2257 sweep(true);
|
|
2258 assert(_collectorState == Resizing, "Collector state change "
|
|
2259 "to Resizing must be done under the free_list_lock");
|
|
2260 _full_gcs_since_conc_gc = 0;
|
|
2261
|
|
2262 // Stop the timers for adaptive size policy for the concurrent phases
|
|
2263 if (UseAdaptiveSizePolicy) {
|
|
2264 size_policy()->concurrent_sweeping_end();
|
|
2265 size_policy()->concurrent_phases_end(gch->gc_cause(),
|
|
2266 gch->prev_gen(_cmsGen)->capacity(),
|
|
2267 _cmsGen->free());
|
|
2268 }
|
|
2269
|
|
2270 case Resizing: {
|
|
2271 // Sweeping has been completed...
|
|
2272 // At this point the background collection has completed.
|
|
2273 // Don't move the call to compute_new_size() down
|
|
2274 // into code that might be executed if the background
|
|
2275 // collection was preempted.
|
|
2276 {
|
|
2277 ReleaseForegroundGC x(this); // unblock FG collection
|
|
2278 MutexLockerEx y(Heap_lock, Mutex::_no_safepoint_check_flag);
|
|
2279 CMSTokenSync z(true); // not strictly needed.
|
|
2280 if (_collectorState == Resizing) {
|
|
2281 compute_new_size();
|
|
2282 _collectorState = Resetting;
|
|
2283 } else {
|
|
2284 assert(_collectorState == Idling, "The state should only change"
|
|
2285 " because the foreground collector has finished the collection");
|
|
2286 }
|
|
2287 }
|
|
2288 break;
|
|
2289 }
|
|
2290 case Resetting:
|
|
2291 // CMS heap resizing has been completed
|
|
2292 reset(true);
|
|
2293 assert(_collectorState == Idling, "Collector state should "
|
|
2294 "have changed");
|
|
2295 stats().record_cms_end();
|
|
2296 // Don't move the concurrent_phases_end() and compute_new_size()
|
|
2297 // calls to here because a preempted background collection
|
|
2298 // has it's state set to "Resetting".
|
|
2299 break;
|
|
2300 case Idling:
|
|
2301 default:
|
|
2302 ShouldNotReachHere();
|
|
2303 break;
|
|
2304 }
|
|
2305 if (TraceCMSState) {
|
|
2306 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d",
|
|
2307 Thread::current(), _collectorState);
|
|
2308 }
|
|
2309 assert(_foregroundGCShouldWait, "block post-condition");
|
|
2310 }
|
|
2311
|
|
2312 // Should this be in gc_epilogue?
|
|
2313 collector_policy()->counters()->update_counters();
|
|
2314
|
|
2315 {
|
|
2316 // Clear _foregroundGCShouldWait and, in the event that the
|
|
2317 // foreground collector is waiting, notify it, before
|
|
2318 // returning.
|
|
2319 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
|
|
2320 _foregroundGCShouldWait = false;
|
|
2321 if (_foregroundGCIsActive) {
|
|
2322 CGC_lock->notify();
|
|
2323 }
|
|
2324 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
2325 "Possible deadlock");
|
|
2326 }
|
|
2327 if (TraceCMSState) {
|
|
2328 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT
|
|
2329 " exiting collection CMS state %d",
|
|
2330 Thread::current(), _collectorState);
|
|
2331 }
|
|
2332 if (PrintGC && Verbose) {
|
|
2333 _cmsGen->print_heap_change(prev_used);
|
|
2334 }
|
|
2335 }
|
|
2336
|
|
2337 void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) {
|
|
2338 assert(_foregroundGCIsActive && !_foregroundGCShouldWait,
|
|
2339 "Foreground collector should be waiting, not executing");
|
|
2340 assert(Thread::current()->is_VM_thread(), "A foreground collection"
|
|
2341 "may only be done by the VM Thread with the world stopped");
|
|
2342 assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(),
|
|
2343 "VM thread should have CMS token");
|
|
2344
|
|
2345 NOT_PRODUCT(TraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose,
|
|
2346 true, gclog_or_tty);)
|
|
2347 if (UseAdaptiveSizePolicy) {
|
|
2348 size_policy()->ms_collection_begin();
|
|
2349 }
|
|
2350 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
|
|
2351
|
|
2352 HandleMark hm; // Discard invalid handles created during verification
|
|
2353
|
|
2354 if (VerifyBeforeGC &&
|
|
2355 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
|
|
2356 Universe::verify(true);
|
|
2357 }
|
|
2358
|
|
2359 bool init_mark_was_synchronous = false; // until proven otherwise
|
|
2360 while (_collectorState != Idling) {
|
|
2361 if (TraceCMSState) {
|
|
2362 gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d",
|
|
2363 Thread::current(), _collectorState);
|
|
2364 }
|
|
2365 switch (_collectorState) {
|
|
2366 case InitialMarking:
|
|
2367 init_mark_was_synchronous = true; // fact to be exploited in re-mark
|
|
2368 checkpointRootsInitial(false);
|
|
2369 assert(_collectorState == Marking, "Collector state should have changed"
|
|
2370 " within checkpointRootsInitial()");
|
|
2371 break;
|
|
2372 case Marking:
|
|
2373 // initial marking in checkpointRootsInitialWork has been completed
|
|
2374 if (VerifyDuringGC &&
|
|
2375 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
|
|
2376 gclog_or_tty->print("Verify before initial mark: ");
|
|
2377 Universe::verify(true);
|
|
2378 }
|
|
2379 {
|
|
2380 bool res = markFromRoots(false);
|
|
2381 assert(res && _collectorState == FinalMarking, "Collector state should "
|
|
2382 "have changed");
|
|
2383 break;
|
|
2384 }
|
|
2385 case FinalMarking:
|
|
2386 if (VerifyDuringGC &&
|
|
2387 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
|
|
2388 gclog_or_tty->print("Verify before re-mark: ");
|
|
2389 Universe::verify(true);
|
|
2390 }
|
|
2391 checkpointRootsFinal(false, clear_all_soft_refs,
|
|
2392 init_mark_was_synchronous);
|
|
2393 assert(_collectorState == Sweeping, "Collector state should not "
|
|
2394 "have changed within checkpointRootsFinal()");
|
|
2395 break;
|
|
2396 case Sweeping:
|
|
2397 // final marking in checkpointRootsFinal has been completed
|
|
2398 if (VerifyDuringGC &&
|
|
2399 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
|
|
2400 gclog_or_tty->print("Verify before sweep: ");
|
|
2401 Universe::verify(true);
|
|
2402 }
|
|
2403 sweep(false);
|
|
2404 assert(_collectorState == Resizing, "Incorrect state");
|
|
2405 break;
|
|
2406 case Resizing: {
|
|
2407 // Sweeping has been completed; the actual resize in this case
|
|
2408 // is done separately; nothing to be done in this state.
|
|
2409 _collectorState = Resetting;
|
|
2410 break;
|
|
2411 }
|
|
2412 case Resetting:
|
|
2413 // The heap has been resized.
|
|
2414 if (VerifyDuringGC &&
|
|
2415 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
|
|
2416 gclog_or_tty->print("Verify before reset: ");
|
|
2417 Universe::verify(true);
|
|
2418 }
|
|
2419 reset(false);
|
|
2420 assert(_collectorState == Idling, "Collector state should "
|
|
2421 "have changed");
|
|
2422 break;
|
|
2423 case Precleaning:
|
|
2424 case AbortablePreclean:
|
|
2425 // Elide the preclean phase
|
|
2426 _collectorState = FinalMarking;
|
|
2427 break;
|
|
2428 default:
|
|
2429 ShouldNotReachHere();
|
|
2430 }
|
|
2431 if (TraceCMSState) {
|
|
2432 gclog_or_tty->print_cr(" Thread " INTPTR_FORMAT " done - next CMS state %d",
|
|
2433 Thread::current(), _collectorState);
|
|
2434 }
|
|
2435 }
|
|
2436
|
|
2437 if (UseAdaptiveSizePolicy) {
|
|
2438 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
2439 size_policy()->ms_collection_end(gch->gc_cause());
|
|
2440 }
|
|
2441
|
|
2442 if (VerifyAfterGC &&
|
|
2443 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
|
|
2444 Universe::verify(true);
|
|
2445 }
|
|
2446 if (TraceCMSState) {
|
|
2447 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT
|
|
2448 " exiting collection CMS state %d",
|
|
2449 Thread::current(), _collectorState);
|
|
2450 }
|
|
2451 }
|
|
2452
|
|
2453 bool CMSCollector::waitForForegroundGC() {
|
|
2454 bool res = false;
|
|
2455 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
2456 "CMS thread should have CMS token");
|
|
2457 // Block the foreground collector until the
|
|
2458 // background collectors decides whether to
|
|
2459 // yield.
|
|
2460 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
|
|
2461 _foregroundGCShouldWait = true;
|
|
2462 if (_foregroundGCIsActive) {
|
|
2463 // The background collector yields to the
|
|
2464 // foreground collector and returns a value
|
|
2465 // indicating that it has yielded. The foreground
|
|
2466 // collector can proceed.
|
|
2467 res = true;
|
|
2468 _foregroundGCShouldWait = false;
|
|
2469 ConcurrentMarkSweepThread::clear_CMS_flag(
|
|
2470 ConcurrentMarkSweepThread::CMS_cms_has_token);
|
|
2471 ConcurrentMarkSweepThread::set_CMS_flag(
|
|
2472 ConcurrentMarkSweepThread::CMS_cms_wants_token);
|
|
2473 // Get a possibly blocked foreground thread going
|
|
2474 CGC_lock->notify();
|
|
2475 if (TraceCMSState) {
|
|
2476 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d",
|
|
2477 Thread::current(), _collectorState);
|
|
2478 }
|
|
2479 while (_foregroundGCIsActive) {
|
|
2480 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
|
|
2481 }
|
|
2482 ConcurrentMarkSweepThread::set_CMS_flag(
|
|
2483 ConcurrentMarkSweepThread::CMS_cms_has_token);
|
|
2484 ConcurrentMarkSweepThread::clear_CMS_flag(
|
|
2485 ConcurrentMarkSweepThread::CMS_cms_wants_token);
|
|
2486 }
|
|
2487 if (TraceCMSState) {
|
|
2488 gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d",
|
|
2489 Thread::current(), _collectorState);
|
|
2490 }
|
|
2491 return res;
|
|
2492 }
|
|
2493
|
|
2494 // Because of the need to lock the free lists and other structures in
|
|
2495 // the collector, common to all the generations that the collector is
|
|
2496 // collecting, we need the gc_prologues of individual CMS generations
|
|
2497 // delegate to their collector. It may have been simpler had the
|
|
2498 // current infrastructure allowed one to call a prologue on a
|
|
2499 // collector. In the absence of that we have the generation's
|
|
2500 // prologue delegate to the collector, which delegates back
|
|
2501 // some "local" work to a worker method in the individual generations
|
|
2502 // that it's responsible for collecting, while itself doing any
|
|
2503 // work common to all generations it's responsible for. A similar
|
|
2504 // comment applies to the gc_epilogue()'s.
|
|
2505 // The role of the varaible _between_prologue_and_epilogue is to
|
|
2506 // enforce the invocation protocol.
|
|
2507 void CMSCollector::gc_prologue(bool full) {
|
|
2508 // Call gc_prologue_work() for each CMSGen and PermGen that
|
|
2509 // we are responsible for.
|
|
2510
|
|
2511 // The following locking discipline assumes that we are only called
|
|
2512 // when the world is stopped.
|
|
2513 assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption");
|
|
2514
|
|
2515 // The CMSCollector prologue must call the gc_prologues for the
|
|
2516 // "generations" (including PermGen if any) that it's responsible
|
|
2517 // for.
|
|
2518
|
|
2519 assert( Thread::current()->is_VM_thread()
|
|
2520 || ( CMSScavengeBeforeRemark
|
|
2521 && Thread::current()->is_ConcurrentGC_thread()),
|
|
2522 "Incorrect thread type for prologue execution");
|
|
2523
|
|
2524 if (_between_prologue_and_epilogue) {
|
|
2525 // We have already been invoked; this is a gc_prologue delegation
|
|
2526 // from yet another CMS generation that we are responsible for, just
|
|
2527 // ignore it since all relevant work has already been done.
|
|
2528 return;
|
|
2529 }
|
|
2530
|
|
2531 // set a bit saying prologue has been called; cleared in epilogue
|
|
2532 _between_prologue_and_epilogue = true;
|
|
2533 // Claim locks for common data structures, then call gc_prologue_work()
|
|
2534 // for each CMSGen and PermGen that we are responsible for.
|
|
2535
|
|
2536 getFreelistLocks(); // gets free list locks on constituent spaces
|
|
2537 bitMapLock()->lock_without_safepoint_check();
|
|
2538
|
|
2539 // Should call gc_prologue_work() for all cms gens we are responsible for
|
|
2540 bool registerClosure = _collectorState >= Marking
|
|
2541 && _collectorState < Sweeping;
|
|
2542 ModUnionClosure* muc = ParallelGCThreads > 0 ? &_modUnionClosurePar
|
|
2543 : &_modUnionClosure;
|
|
2544 _cmsGen->gc_prologue_work(full, registerClosure, muc);
|
|
2545 _permGen->gc_prologue_work(full, registerClosure, muc);
|
|
2546
|
|
2547 if (!full) {
|
|
2548 stats().record_gc0_begin();
|
|
2549 }
|
|
2550 }
|
|
2551
|
|
2552 void ConcurrentMarkSweepGeneration::gc_prologue(bool full) {
|
|
2553 // Delegate to CMScollector which knows how to coordinate between
|
|
2554 // this and any other CMS generations that it is responsible for
|
|
2555 // collecting.
|
|
2556 collector()->gc_prologue(full);
|
|
2557 }
|
|
2558
|
|
2559 // This is a "private" interface for use by this generation's CMSCollector.
|
|
2560 // Not to be called directly by any other entity (for instance,
|
|
2561 // GenCollectedHeap, which calls the "public" gc_prologue method above).
|
|
2562 void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full,
|
|
2563 bool registerClosure, ModUnionClosure* modUnionClosure) {
|
|
2564 assert(!incremental_collection_failed(), "Shouldn't be set yet");
|
|
2565 assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL,
|
|
2566 "Should be NULL");
|
|
2567 if (registerClosure) {
|
|
2568 cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure);
|
|
2569 }
|
|
2570 cmsSpace()->gc_prologue();
|
|
2571 // Clear stat counters
|
|
2572 NOT_PRODUCT(
|
|
2573 assert(_numObjectsPromoted == 0, "check");
|
|
2574 assert(_numWordsPromoted == 0, "check");
|
|
2575 if (Verbose && PrintGC) {
|
|
2576 gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, "
|
|
2577 SIZE_FORMAT" bytes concurrently",
|
|
2578 _numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord));
|
|
2579 }
|
|
2580 _numObjectsAllocated = 0;
|
|
2581 _numWordsAllocated = 0;
|
|
2582 )
|
|
2583 }
|
|
2584
|
|
2585 void CMSCollector::gc_epilogue(bool full) {
|
|
2586 // The following locking discipline assumes that we are only called
|
|
2587 // when the world is stopped.
|
|
2588 assert(SafepointSynchronize::is_at_safepoint(),
|
|
2589 "world is stopped assumption");
|
|
2590
|
|
2591 // Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks
|
|
2592 // if linear allocation blocks need to be appropriately marked to allow the
|
|
2593 // the blocks to be parsable. We also check here whether we need to nudge the
|
|
2594 // CMS collector thread to start a new cycle (if it's not already active).
|
|
2595 assert( Thread::current()->is_VM_thread()
|
|
2596 || ( CMSScavengeBeforeRemark
|
|
2597 && Thread::current()->is_ConcurrentGC_thread()),
|
|
2598 "Incorrect thread type for epilogue execution");
|
|
2599
|
|
2600 if (!_between_prologue_and_epilogue) {
|
|
2601 // We have already been invoked; this is a gc_epilogue delegation
|
|
2602 // from yet another CMS generation that we are responsible for, just
|
|
2603 // ignore it since all relevant work has already been done.
|
|
2604 return;
|
|
2605 }
|
|
2606 assert(haveFreelistLocks(), "must have freelist locks");
|
|
2607 assert_lock_strong(bitMapLock());
|
|
2608
|
|
2609 _cmsGen->gc_epilogue_work(full);
|
|
2610 _permGen->gc_epilogue_work(full);
|
|
2611
|
|
2612 if (_collectorState == AbortablePreclean || _collectorState == Precleaning) {
|
|
2613 // in case sampling was not already enabled, enable it
|
|
2614 _start_sampling = true;
|
|
2615 }
|
|
2616 // reset _eden_chunk_array so sampling starts afresh
|
|
2617 _eden_chunk_index = 0;
|
|
2618
|
|
2619 size_t cms_used = _cmsGen->cmsSpace()->used();
|
|
2620 size_t perm_used = _permGen->cmsSpace()->used();
|
|
2621
|
|
2622 // update performance counters - this uses a special version of
|
|
2623 // update_counters() that allows the utilization to be passed as a
|
|
2624 // parameter, avoiding multiple calls to used().
|
|
2625 //
|
|
2626 _cmsGen->update_counters(cms_used);
|
|
2627 _permGen->update_counters(perm_used);
|
|
2628
|
|
2629 if (CMSIncrementalMode) {
|
|
2630 icms_update_allocation_limits();
|
|
2631 }
|
|
2632
|
|
2633 bitMapLock()->unlock();
|
|
2634 releaseFreelistLocks();
|
|
2635
|
|
2636 _between_prologue_and_epilogue = false; // ready for next cycle
|
|
2637 }
|
|
2638
|
|
2639 void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) {
|
|
2640 collector()->gc_epilogue(full);
|
|
2641
|
|
2642 // Also reset promotion tracking in par gc thread states.
|
|
2643 if (ParallelGCThreads > 0) {
|
|
2644 for (uint i = 0; i < ParallelGCThreads; i++) {
|
|
2645 _par_gc_thread_states[i]->promo.stopTrackingPromotions();
|
|
2646 }
|
|
2647 }
|
|
2648 }
|
|
2649
|
|
2650 void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) {
|
|
2651 assert(!incremental_collection_failed(), "Should have been cleared");
|
|
2652 cmsSpace()->setPreconsumptionDirtyCardClosure(NULL);
|
|
2653 cmsSpace()->gc_epilogue();
|
|
2654 // Print stat counters
|
|
2655 NOT_PRODUCT(
|
|
2656 assert(_numObjectsAllocated == 0, "check");
|
|
2657 assert(_numWordsAllocated == 0, "check");
|
|
2658 if (Verbose && PrintGC) {
|
|
2659 gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, "
|
|
2660 SIZE_FORMAT" bytes",
|
|
2661 _numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord));
|
|
2662 }
|
|
2663 _numObjectsPromoted = 0;
|
|
2664 _numWordsPromoted = 0;
|
|
2665 )
|
|
2666
|
|
2667 if (PrintGC && Verbose) {
|
|
2668 // Call down the chain in contiguous_available needs the freelistLock
|
|
2669 // so print this out before releasing the freeListLock.
|
|
2670 gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ",
|
|
2671 contiguous_available());
|
|
2672 }
|
|
2673 }
|
|
2674
|
|
2675 #ifndef PRODUCT
|
|
2676 bool CMSCollector::have_cms_token() {
|
|
2677 Thread* thr = Thread::current();
|
|
2678 if (thr->is_VM_thread()) {
|
|
2679 return ConcurrentMarkSweepThread::vm_thread_has_cms_token();
|
|
2680 } else if (thr->is_ConcurrentGC_thread()) {
|
|
2681 return ConcurrentMarkSweepThread::cms_thread_has_cms_token();
|
|
2682 } else if (thr->is_GC_task_thread()) {
|
|
2683 return ConcurrentMarkSweepThread::vm_thread_has_cms_token() &&
|
|
2684 ParGCRareEvent_lock->owned_by_self();
|
|
2685 }
|
|
2686 return false;
|
|
2687 }
|
|
2688 #endif
|
|
2689
|
|
2690 // Check reachability of the given heap address in CMS generation,
|
|
2691 // treating all other generations as roots.
|
|
2692 bool CMSCollector::is_cms_reachable(HeapWord* addr) {
|
|
2693 // We could "guarantee" below, rather than assert, but i'll
|
|
2694 // leave these as "asserts" so that an adventurous debugger
|
|
2695 // could try this in the product build provided some subset of
|
|
2696 // the conditions were met, provided they were intersted in the
|
|
2697 // results and knew that the computation below wouldn't interfere
|
|
2698 // with other concurrent computations mutating the structures
|
|
2699 // being read or written.
|
|
2700 assert(SafepointSynchronize::is_at_safepoint(),
|
|
2701 "Else mutations in object graph will make answer suspect");
|
|
2702 assert(have_cms_token(), "Should hold cms token");
|
|
2703 assert(haveFreelistLocks(), "must hold free list locks");
|
|
2704 assert_lock_strong(bitMapLock());
|
|
2705
|
|
2706 // Clear the marking bit map array before starting, but, just
|
|
2707 // for kicks, first report if the given address is already marked
|
|
2708 gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr,
|
|
2709 _markBitMap.isMarked(addr) ? "" : " not");
|
|
2710
|
|
2711 if (verify_after_remark()) {
|
|
2712 MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag);
|
|
2713 bool result = verification_mark_bm()->isMarked(addr);
|
|
2714 gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr,
|
|
2715 result ? "IS" : "is NOT");
|
|
2716 return result;
|
|
2717 } else {
|
|
2718 gclog_or_tty->print_cr("Could not compute result");
|
|
2719 return false;
|
|
2720 }
|
|
2721 }
|
|
2722
|
|
2723 ////////////////////////////////////////////////////////
|
|
2724 // CMS Verification Support
|
|
2725 ////////////////////////////////////////////////////////
|
|
2726 // Following the remark phase, the following invariant
|
|
2727 // should hold -- each object in the CMS heap which is
|
|
2728 // marked in markBitMap() should be marked in the verification_mark_bm().
|
|
2729
|
|
2730 class VerifyMarkedClosure: public BitMapClosure {
|
|
2731 CMSBitMap* _marks;
|
|
2732 bool _failed;
|
|
2733
|
|
2734 public:
|
|
2735 VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {}
|
|
2736
|
|
2737 void do_bit(size_t offset) {
|
|
2738 HeapWord* addr = _marks->offsetToHeapWord(offset);
|
|
2739 if (!_marks->isMarked(addr)) {
|
|
2740 oop(addr)->print();
|
|
2741 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr);
|
|
2742 _failed = true;
|
|
2743 }
|
|
2744 }
|
|
2745
|
|
2746 bool failed() { return _failed; }
|
|
2747 };
|
|
2748
|
|
2749 bool CMSCollector::verify_after_remark() {
|
|
2750 gclog_or_tty->print(" [Verifying CMS Marking... ");
|
|
2751 MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag);
|
|
2752 static bool init = false;
|
|
2753
|
|
2754 assert(SafepointSynchronize::is_at_safepoint(),
|
|
2755 "Else mutations in object graph will make answer suspect");
|
|
2756 assert(have_cms_token(),
|
|
2757 "Else there may be mutual interference in use of "
|
|
2758 " verification data structures");
|
|
2759 assert(_collectorState > Marking && _collectorState <= Sweeping,
|
|
2760 "Else marking info checked here may be obsolete");
|
|
2761 assert(haveFreelistLocks(), "must hold free list locks");
|
|
2762 assert_lock_strong(bitMapLock());
|
|
2763
|
|
2764
|
|
2765 // Allocate marking bit map if not already allocated
|
|
2766 if (!init) { // first time
|
|
2767 if (!verification_mark_bm()->allocate(_span)) {
|
|
2768 return false;
|
|
2769 }
|
|
2770 init = true;
|
|
2771 }
|
|
2772
|
|
2773 assert(verification_mark_stack()->isEmpty(), "Should be empty");
|
|
2774
|
|
2775 // Turn off refs discovery -- so we will be tracing through refs.
|
|
2776 // This is as intended, because by this time
|
|
2777 // GC must already have cleared any refs that need to be cleared,
|
|
2778 // and traced those that need to be marked; moreover,
|
|
2779 // the marking done here is not going to intefere in any
|
|
2780 // way with the marking information used by GC.
|
|
2781 NoRefDiscovery no_discovery(ref_processor());
|
|
2782
|
|
2783 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;)
|
|
2784
|
|
2785 // Clear any marks from a previous round
|
|
2786 verification_mark_bm()->clear_all();
|
|
2787 assert(verification_mark_stack()->isEmpty(), "markStack should be empty");
|
|
2788 assert(overflow_list_is_empty(), "overflow list should be empty");
|
|
2789
|
|
2790 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
2791 gch->ensure_parsability(false); // fill TLABs, but no need to retire them
|
|
2792 // Update the saved marks which may affect the root scans.
|
|
2793 gch->save_marks();
|
|
2794
|
|
2795 if (CMSRemarkVerifyVariant == 1) {
|
|
2796 // In this first variant of verification, we complete
|
|
2797 // all marking, then check if the new marks-verctor is
|
|
2798 // a subset of the CMS marks-vector.
|
|
2799 verify_after_remark_work_1();
|
|
2800 } else if (CMSRemarkVerifyVariant == 2) {
|
|
2801 // In this second variant of verification, we flag an error
|
|
2802 // (i.e. an object reachable in the new marks-vector not reachable
|
|
2803 // in the CMS marks-vector) immediately, also indicating the
|
|
2804 // identify of an object (A) that references the unmarked object (B) --
|
|
2805 // presumably, a mutation to A failed to be picked up by preclean/remark?
|
|
2806 verify_after_remark_work_2();
|
|
2807 } else {
|
|
2808 warning("Unrecognized value %d for CMSRemarkVerifyVariant",
|
|
2809 CMSRemarkVerifyVariant);
|
|
2810 }
|
|
2811 gclog_or_tty->print(" done] ");
|
|
2812 return true;
|
|
2813 }
|
|
2814
|
|
2815 void CMSCollector::verify_after_remark_work_1() {
|
|
2816 ResourceMark rm;
|
|
2817 HandleMark hm;
|
|
2818 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
2819
|
|
2820 // Mark from roots one level into CMS
|
|
2821 MarkRefsIntoClosure notOlder(_span, verification_mark_bm(), true /* nmethods */);
|
|
2822 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel.
|
|
2823
|
|
2824 gch->gen_process_strong_roots(_cmsGen->level(),
|
|
2825 true, // younger gens are roots
|
|
2826 true, // collecting perm gen
|
|
2827 SharedHeap::ScanningOption(roots_scanning_options()),
|
|
2828 NULL, ¬Older);
|
|
2829
|
|
2830 // Now mark from the roots
|
|
2831 assert(_revisitStack.isEmpty(), "Should be empty");
|
|
2832 MarkFromRootsClosure markFromRootsClosure(this, _span,
|
|
2833 verification_mark_bm(), verification_mark_stack(), &_revisitStack,
|
|
2834 false /* don't yield */, true /* verifying */);
|
|
2835 assert(_restart_addr == NULL, "Expected pre-condition");
|
|
2836 verification_mark_bm()->iterate(&markFromRootsClosure);
|
|
2837 while (_restart_addr != NULL) {
|
|
2838 // Deal with stack overflow: by restarting at the indicated
|
|
2839 // address.
|
|
2840 HeapWord* ra = _restart_addr;
|
|
2841 markFromRootsClosure.reset(ra);
|
|
2842 _restart_addr = NULL;
|
|
2843 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end());
|
|
2844 }
|
|
2845 assert(verification_mark_stack()->isEmpty(), "Should have been drained");
|
|
2846 verify_work_stacks_empty();
|
|
2847 // Should reset the revisit stack above, since no class tree
|
|
2848 // surgery is forthcoming.
|
|
2849 _revisitStack.reset(); // throwing away all contents
|
|
2850
|
|
2851 // Marking completed -- now verify that each bit marked in
|
|
2852 // verification_mark_bm() is also marked in markBitMap(); flag all
|
|
2853 // errors by printing corresponding objects.
|
|
2854 VerifyMarkedClosure vcl(markBitMap());
|
|
2855 verification_mark_bm()->iterate(&vcl);
|
|
2856 if (vcl.failed()) {
|
|
2857 gclog_or_tty->print("Verification failed");
|
|
2858 Universe::heap()->print();
|
|
2859 fatal(" ... aborting");
|
|
2860 }
|
|
2861 }
|
|
2862
|
|
2863 void CMSCollector::verify_after_remark_work_2() {
|
|
2864 ResourceMark rm;
|
|
2865 HandleMark hm;
|
|
2866 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
2867
|
|
2868 // Mark from roots one level into CMS
|
|
2869 MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(),
|
|
2870 markBitMap(), true /* nmethods */);
|
|
2871 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel.
|
|
2872 gch->gen_process_strong_roots(_cmsGen->level(),
|
|
2873 true, // younger gens are roots
|
|
2874 true, // collecting perm gen
|
|
2875 SharedHeap::ScanningOption(roots_scanning_options()),
|
|
2876 NULL, ¬Older);
|
|
2877
|
|
2878 // Now mark from the roots
|
|
2879 assert(_revisitStack.isEmpty(), "Should be empty");
|
|
2880 MarkFromRootsVerifyClosure markFromRootsClosure(this, _span,
|
|
2881 verification_mark_bm(), markBitMap(), verification_mark_stack());
|
|
2882 assert(_restart_addr == NULL, "Expected pre-condition");
|
|
2883 verification_mark_bm()->iterate(&markFromRootsClosure);
|
|
2884 while (_restart_addr != NULL) {
|
|
2885 // Deal with stack overflow: by restarting at the indicated
|
|
2886 // address.
|
|
2887 HeapWord* ra = _restart_addr;
|
|
2888 markFromRootsClosure.reset(ra);
|
|
2889 _restart_addr = NULL;
|
|
2890 verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end());
|
|
2891 }
|
|
2892 assert(verification_mark_stack()->isEmpty(), "Should have been drained");
|
|
2893 verify_work_stacks_empty();
|
|
2894 // Should reset the revisit stack above, since no class tree
|
|
2895 // surgery is forthcoming.
|
|
2896 _revisitStack.reset(); // throwing away all contents
|
|
2897
|
|
2898 // Marking completed -- now verify that each bit marked in
|
|
2899 // verification_mark_bm() is also marked in markBitMap(); flag all
|
|
2900 // errors by printing corresponding objects.
|
|
2901 VerifyMarkedClosure vcl(markBitMap());
|
|
2902 verification_mark_bm()->iterate(&vcl);
|
|
2903 assert(!vcl.failed(), "Else verification above should not have succeeded");
|
|
2904 }
|
|
2905
|
|
2906 void ConcurrentMarkSweepGeneration::save_marks() {
|
|
2907 // delegate to CMS space
|
|
2908 cmsSpace()->save_marks();
|
|
2909 for (uint i = 0; i < ParallelGCThreads; i++) {
|
|
2910 _par_gc_thread_states[i]->promo.startTrackingPromotions();
|
|
2911 }
|
|
2912 }
|
|
2913
|
|
2914 bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() {
|
|
2915 return cmsSpace()->no_allocs_since_save_marks();
|
|
2916 }
|
|
2917
|
|
2918 #define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
|
|
2919 \
|
|
2920 void ConcurrentMarkSweepGeneration:: \
|
|
2921 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
|
|
2922 cl->set_generation(this); \
|
|
2923 cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl); \
|
|
2924 cl->reset_generation(); \
|
|
2925 save_marks(); \
|
|
2926 }
|
|
2927
|
|
2928 ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN)
|
|
2929
|
|
2930 void
|
|
2931 ConcurrentMarkSweepGeneration::object_iterate_since_last_GC(ObjectClosure* blk)
|
|
2932 {
|
|
2933 // Not currently implemented; need to do the following. -- ysr.
|
|
2934 // dld -- I think that is used for some sort of allocation profiler. So it
|
|
2935 // really means the objects allocated by the mutator since the last
|
|
2936 // GC. We could potentially implement this cheaply by recording only
|
|
2937 // the direct allocations in a side data structure.
|
|
2938 //
|
|
2939 // I think we probably ought not to be required to support these
|
|
2940 // iterations at any arbitrary point; I think there ought to be some
|
|
2941 // call to enable/disable allocation profiling in a generation/space,
|
|
2942 // and the iterator ought to return the objects allocated in the
|
|
2943 // gen/space since the enable call, or the last iterator call (which
|
|
2944 // will probably be at a GC.) That way, for gens like CM&S that would
|
|
2945 // require some extra data structure to support this, we only pay the
|
|
2946 // cost when it's in use...
|
|
2947 cmsSpace()->object_iterate_since_last_GC(blk);
|
|
2948 }
|
|
2949
|
|
2950 void
|
|
2951 ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
|
|
2952 cl->set_generation(this);
|
|
2953 younger_refs_in_space_iterate(_cmsSpace, cl);
|
|
2954 cl->reset_generation();
|
|
2955 }
|
|
2956
|
|
2957 void
|
|
2958 ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, OopClosure* cl) {
|
|
2959 if (freelistLock()->owned_by_self()) {
|
|
2960 Generation::oop_iterate(mr, cl);
|
|
2961 } else {
|
|
2962 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
|
|
2963 Generation::oop_iterate(mr, cl);
|
|
2964 }
|
|
2965 }
|
|
2966
|
|
2967 void
|
|
2968 ConcurrentMarkSweepGeneration::oop_iterate(OopClosure* cl) {
|
|
2969 if (freelistLock()->owned_by_self()) {
|
|
2970 Generation::oop_iterate(cl);
|
|
2971 } else {
|
|
2972 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
|
|
2973 Generation::oop_iterate(cl);
|
|
2974 }
|
|
2975 }
|
|
2976
|
|
2977 void
|
|
2978 ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) {
|
|
2979 if (freelistLock()->owned_by_self()) {
|
|
2980 Generation::object_iterate(cl);
|
|
2981 } else {
|
|
2982 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
|
|
2983 Generation::object_iterate(cl);
|
|
2984 }
|
|
2985 }
|
|
2986
|
|
2987 void
|
|
2988 ConcurrentMarkSweepGeneration::pre_adjust_pointers() {
|
|
2989 }
|
|
2990
|
|
2991 void
|
|
2992 ConcurrentMarkSweepGeneration::post_compact() {
|
|
2993 }
|
|
2994
|
|
2995 void
|
|
2996 ConcurrentMarkSweepGeneration::prepare_for_verify() {
|
|
2997 // Fix the linear allocation blocks to look like free blocks.
|
|
2998
|
|
2999 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those
|
|
3000 // are not called when the heap is verified during universe initialization and
|
|
3001 // at vm shutdown.
|
|
3002 if (freelistLock()->owned_by_self()) {
|
|
3003 cmsSpace()->prepare_for_verify();
|
|
3004 } else {
|
|
3005 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag);
|
|
3006 cmsSpace()->prepare_for_verify();
|
|
3007 }
|
|
3008 }
|
|
3009
|
|
3010 void
|
|
3011 ConcurrentMarkSweepGeneration::verify(bool allow_dirty /* ignored */) {
|
|
3012 // Locks are normally acquired/released in gc_prologue/gc_epilogue, but those
|
|
3013 // are not called when the heap is verified during universe initialization and
|
|
3014 // at vm shutdown.
|
|
3015 if (freelistLock()->owned_by_self()) {
|
|
3016 cmsSpace()->verify(false /* ignored */);
|
|
3017 } else {
|
|
3018 MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag);
|
|
3019 cmsSpace()->verify(false /* ignored */);
|
|
3020 }
|
|
3021 }
|
|
3022
|
|
3023 void CMSCollector::verify(bool allow_dirty /* ignored */) {
|
|
3024 _cmsGen->verify(allow_dirty);
|
|
3025 _permGen->verify(allow_dirty);
|
|
3026 }
|
|
3027
|
|
3028 #ifndef PRODUCT
|
|
3029 bool CMSCollector::overflow_list_is_empty() const {
|
|
3030 assert(_num_par_pushes >= 0, "Inconsistency");
|
|
3031 if (_overflow_list == NULL) {
|
|
3032 assert(_num_par_pushes == 0, "Inconsistency");
|
|
3033 }
|
|
3034 return _overflow_list == NULL;
|
|
3035 }
|
|
3036
|
|
3037 // The methods verify_work_stacks_empty() and verify_overflow_empty()
|
|
3038 // merely consolidate assertion checks that appear to occur together frequently.
|
|
3039 void CMSCollector::verify_work_stacks_empty() const {
|
|
3040 assert(_markStack.isEmpty(), "Marking stack should be empty");
|
|
3041 assert(overflow_list_is_empty(), "Overflow list should be empty");
|
|
3042 }
|
|
3043
|
|
3044 void CMSCollector::verify_overflow_empty() const {
|
|
3045 assert(overflow_list_is_empty(), "Overflow list should be empty");
|
|
3046 assert(no_preserved_marks(), "No preserved marks");
|
|
3047 }
|
|
3048 #endif // PRODUCT
|
|
3049
|
|
3050 void CMSCollector::setup_cms_unloading_and_verification_state() {
|
|
3051 const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC
|
|
3052 || VerifyBeforeExit;
|
|
3053 const int rso = SharedHeap::SO_Symbols | SharedHeap::SO_Strings
|
|
3054 | SharedHeap::SO_CodeCache;
|
|
3055
|
|
3056 if (cms_should_unload_classes()) { // Should unload classes this cycle
|
|
3057 remove_root_scanning_option(rso); // Shrink the root set appropriately
|
|
3058 set_verifying(should_verify); // Set verification state for this cycle
|
|
3059 return; // Nothing else needs to be done at this time
|
|
3060 }
|
|
3061
|
|
3062 // Not unloading classes this cycle
|
|
3063 assert(!cms_should_unload_classes(), "Inconsitency!");
|
|
3064 if ((!verifying() || cms_unloaded_classes_last_cycle()) && should_verify) {
|
|
3065 // We were not verifying, or we _were_ unloading classes in the last cycle,
|
|
3066 // AND some verification options are enabled this cycle; in this case,
|
|
3067 // we must make sure that the deadness map is allocated if not already so,
|
|
3068 // and cleared (if already allocated previously --
|
|
3069 // CMSBitMap::sizeInBits() is used to determine if it's allocated).
|
|
3070 if (perm_gen_verify_bit_map()->sizeInBits() == 0) {
|
|
3071 if (!perm_gen_verify_bit_map()->allocate(_permGen->reserved())) {
|
|
3072 warning("Failed to allocate permanent generation verification CMS Bit Map;\n"
|
|
3073 "permanent generation verification disabled");
|
|
3074 return; // Note that we leave verification disabled, so we'll retry this
|
|
3075 // allocation next cycle. We _could_ remember this failure
|
|
3076 // and skip further attempts and permanently disable verification
|
|
3077 // attempts if that is considered more desirable.
|
|
3078 }
|
|
3079 assert(perm_gen_verify_bit_map()->covers(_permGen->reserved()),
|
|
3080 "_perm_gen_ver_bit_map inconsistency?");
|
|
3081 } else {
|
|
3082 perm_gen_verify_bit_map()->clear_all();
|
|
3083 }
|
|
3084 // Include symbols, strings and code cache elements to prevent their resurrection.
|
|
3085 add_root_scanning_option(rso);
|
|
3086 set_verifying(true);
|
|
3087 } else if (verifying() && !should_verify) {
|
|
3088 // We were verifying, but some verification flags got disabled.
|
|
3089 set_verifying(false);
|
|
3090 // Exclude symbols, strings and code cache elements from root scanning to
|
|
3091 // reduce IM and RM pauses.
|
|
3092 remove_root_scanning_option(rso);
|
|
3093 }
|
|
3094 }
|
|
3095
|
|
3096
|
|
3097 #ifndef PRODUCT
|
|
3098 HeapWord* CMSCollector::block_start(const void* p) const {
|
|
3099 const HeapWord* addr = (HeapWord*)p;
|
|
3100 if (_span.contains(p)) {
|
|
3101 if (_cmsGen->cmsSpace()->is_in_reserved(addr)) {
|
|
3102 return _cmsGen->cmsSpace()->block_start(p);
|
|
3103 } else {
|
|
3104 assert(_permGen->cmsSpace()->is_in_reserved(addr),
|
|
3105 "Inconsistent _span?");
|
|
3106 return _permGen->cmsSpace()->block_start(p);
|
|
3107 }
|
|
3108 }
|
|
3109 return NULL;
|
|
3110 }
|
|
3111 #endif
|
|
3112
|
|
3113 HeapWord*
|
|
3114 ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size,
|
|
3115 bool tlab,
|
|
3116 bool parallel) {
|
|
3117 assert(!tlab, "Can't deal with TLAB allocation");
|
|
3118 MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
|
|
3119 expand(word_size*HeapWordSize, MinHeapDeltaBytes,
|
|
3120 CMSExpansionCause::_satisfy_allocation);
|
|
3121 if (GCExpandToAllocateDelayMillis > 0) {
|
|
3122 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false);
|
|
3123 }
|
|
3124 size_t adj_word_sz = CompactibleFreeListSpace::adjustObjectSize(word_size);
|
|
3125 if (parallel) {
|
|
3126 return cmsSpace()->par_allocate(adj_word_sz);
|
|
3127 } else {
|
|
3128 return cmsSpace()->allocate(adj_word_sz);
|
|
3129 }
|
|
3130 }
|
|
3131
|
|
3132 // YSR: All of this generation expansion/shrinking stuff is an exact copy of
|
|
3133 // OneContigSpaceCardGeneration, which makes me wonder if we should move this
|
|
3134 // to CardGeneration and share it...
|
|
3135 void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes,
|
|
3136 CMSExpansionCause::Cause cause)
|
|
3137 {
|
|
3138 assert_locked_or_safepoint(Heap_lock);
|
|
3139
|
|
3140 size_t aligned_bytes = ReservedSpace::page_align_size_up(bytes);
|
|
3141 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
|
|
3142 bool success = false;
|
|
3143 if (aligned_expand_bytes > aligned_bytes) {
|
|
3144 success = grow_by(aligned_expand_bytes);
|
|
3145 }
|
|
3146 if (!success) {
|
|
3147 success = grow_by(aligned_bytes);
|
|
3148 }
|
|
3149 if (!success) {
|
|
3150 size_t remaining_bytes = _virtual_space.uncommitted_size();
|
|
3151 if (remaining_bytes > 0) {
|
|
3152 success = grow_by(remaining_bytes);
|
|
3153 }
|
|
3154 }
|
|
3155 if (GC_locker::is_active()) {
|
|
3156 if (PrintGC && Verbose) {
|
|
3157 gclog_or_tty->print_cr("Garbage collection disabled, expanded heap instead");
|
|
3158 }
|
|
3159 }
|
|
3160 // remember why we expanded; this information is used
|
|
3161 // by shouldConcurrentCollect() when making decisions on whether to start
|
|
3162 // a new CMS cycle.
|
|
3163 if (success) {
|
|
3164 set_expansion_cause(cause);
|
|
3165 if (PrintGCDetails && Verbose) {
|
|
3166 gclog_or_tty->print_cr("Expanded CMS gen for %s",
|
|
3167 CMSExpansionCause::to_string(cause));
|
|
3168 }
|
|
3169 }
|
|
3170 }
|
|
3171
|
|
3172 HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) {
|
|
3173 HeapWord* res = NULL;
|
|
3174 MutexLocker x(ParGCRareEvent_lock);
|
|
3175 while (true) {
|
|
3176 // Expansion by some other thread might make alloc OK now:
|
|
3177 res = ps->lab.alloc(word_sz);
|
|
3178 if (res != NULL) return res;
|
|
3179 // If there's not enough expansion space available, give up.
|
|
3180 if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) {
|
|
3181 return NULL;
|
|
3182 }
|
|
3183 // Otherwise, we try expansion.
|
|
3184 expand(word_sz*HeapWordSize, MinHeapDeltaBytes,
|
|
3185 CMSExpansionCause::_allocate_par_lab);
|
|
3186 // Now go around the loop and try alloc again;
|
|
3187 // A competing par_promote might beat us to the expansion space,
|
|
3188 // so we may go around the loop again if promotion fails agaion.
|
|
3189 if (GCExpandToAllocateDelayMillis > 0) {
|
|
3190 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false);
|
|
3191 }
|
|
3192 }
|
|
3193 }
|
|
3194
|
|
3195
|
|
3196 bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space(
|
|
3197 PromotionInfo* promo) {
|
|
3198 MutexLocker x(ParGCRareEvent_lock);
|
|
3199 size_t refill_size_bytes = promo->refillSize() * HeapWordSize;
|
|
3200 while (true) {
|
|
3201 // Expansion by some other thread might make alloc OK now:
|
|
3202 if (promo->ensure_spooling_space()) {
|
|
3203 assert(promo->has_spooling_space(),
|
|
3204 "Post-condition of successful ensure_spooling_space()");
|
|
3205 return true;
|
|
3206 }
|
|
3207 // If there's not enough expansion space available, give up.
|
|
3208 if (_virtual_space.uncommitted_size() < refill_size_bytes) {
|
|
3209 return false;
|
|
3210 }
|
|
3211 // Otherwise, we try expansion.
|
|
3212 expand(refill_size_bytes, MinHeapDeltaBytes,
|
|
3213 CMSExpansionCause::_allocate_par_spooling_space);
|
|
3214 // Now go around the loop and try alloc again;
|
|
3215 // A competing allocation might beat us to the expansion space,
|
|
3216 // so we may go around the loop again if allocation fails again.
|
|
3217 if (GCExpandToAllocateDelayMillis > 0) {
|
|
3218 os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false);
|
|
3219 }
|
|
3220 }
|
|
3221 }
|
|
3222
|
|
3223
|
|
3224
|
|
3225 void ConcurrentMarkSweepGeneration::shrink(size_t bytes) {
|
|
3226 assert_locked_or_safepoint(Heap_lock);
|
|
3227 size_t size = ReservedSpace::page_align_size_down(bytes);
|
|
3228 if (size > 0) {
|
|
3229 shrink_by(size);
|
|
3230 }
|
|
3231 }
|
|
3232
|
|
3233 bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) {
|
|
3234 assert_locked_or_safepoint(Heap_lock);
|
|
3235 bool result = _virtual_space.expand_by(bytes);
|
|
3236 if (result) {
|
|
3237 HeapWord* old_end = _cmsSpace->end();
|
|
3238 size_t new_word_size =
|
|
3239 heap_word_size(_virtual_space.committed_size());
|
|
3240 MemRegion mr(_cmsSpace->bottom(), new_word_size);
|
|
3241 _bts->resize(new_word_size); // resize the block offset shared array
|
|
3242 Universe::heap()->barrier_set()->resize_covered_region(mr);
|
|
3243 // Hmmmm... why doesn't CFLS::set_end verify locking?
|
|
3244 // This is quite ugly; FIX ME XXX
|
|
3245 _cmsSpace->assert_locked();
|
|
3246 _cmsSpace->set_end((HeapWord*)_virtual_space.high());
|
|
3247
|
|
3248 // update the space and generation capacity counters
|
|
3249 if (UsePerfData) {
|
|
3250 _space_counters->update_capacity();
|
|
3251 _gen_counters->update_all();
|
|
3252 }
|
|
3253
|
|
3254 if (Verbose && PrintGC) {
|
|
3255 size_t new_mem_size = _virtual_space.committed_size();
|
|
3256 size_t old_mem_size = new_mem_size - bytes;
|
|
3257 gclog_or_tty->print_cr("Expanding %s from %ldK by %ldK to %ldK",
|
|
3258 name(), old_mem_size/K, bytes/K, new_mem_size/K);
|
|
3259 }
|
|
3260 }
|
|
3261 return result;
|
|
3262 }
|
|
3263
|
|
3264 bool ConcurrentMarkSweepGeneration::grow_to_reserved() {
|
|
3265 assert_locked_or_safepoint(Heap_lock);
|
|
3266 bool success = true;
|
|
3267 const size_t remaining_bytes = _virtual_space.uncommitted_size();
|
|
3268 if (remaining_bytes > 0) {
|
|
3269 success = grow_by(remaining_bytes);
|
|
3270 DEBUG_ONLY(if (!success) warning("grow to reserved failed");)
|
|
3271 }
|
|
3272 return success;
|
|
3273 }
|
|
3274
|
|
3275 void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) {
|
|
3276 assert_locked_or_safepoint(Heap_lock);
|
|
3277 assert_lock_strong(freelistLock());
|
|
3278 // XXX Fix when compaction is implemented.
|
|
3279 warning("Shrinking of CMS not yet implemented");
|
|
3280 return;
|
|
3281 }
|
|
3282
|
|
3283
|
|
3284 // Simple ctor/dtor wrapper for accounting & timer chores around concurrent
|
|
3285 // phases.
|
|
3286 class CMSPhaseAccounting: public StackObj {
|
|
3287 public:
|
|
3288 CMSPhaseAccounting(CMSCollector *collector,
|
|
3289 const char *phase,
|
|
3290 bool print_cr = true);
|
|
3291 ~CMSPhaseAccounting();
|
|
3292
|
|
3293 private:
|
|
3294 CMSCollector *_collector;
|
|
3295 const char *_phase;
|
|
3296 elapsedTimer _wallclock;
|
|
3297 bool _print_cr;
|
|
3298
|
|
3299 public:
|
|
3300 // Not MT-safe; so do not pass around these StackObj's
|
|
3301 // where they may be accessed by other threads.
|
|
3302 jlong wallclock_millis() {
|
|
3303 assert(_wallclock.is_active(), "Wall clock should not stop");
|
|
3304 _wallclock.stop(); // to record time
|
|
3305 jlong ret = _wallclock.milliseconds();
|
|
3306 _wallclock.start(); // restart
|
|
3307 return ret;
|
|
3308 }
|
|
3309 };
|
|
3310
|
|
3311 CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector,
|
|
3312 const char *phase,
|
|
3313 bool print_cr) :
|
|
3314 _collector(collector), _phase(phase), _print_cr(print_cr) {
|
|
3315
|
|
3316 if (PrintCMSStatistics != 0) {
|
|
3317 _collector->resetYields();
|
|
3318 }
|
|
3319 if (PrintGCDetails && PrintGCTimeStamps) {
|
|
3320 gclog_or_tty->date_stamp(PrintGCDateStamps);
|
|
3321 gclog_or_tty->stamp();
|
|
3322 gclog_or_tty->print_cr(": [%s-concurrent-%s-start]",
|
|
3323 _collector->cmsGen()->short_name(), _phase);
|
|
3324 }
|
|
3325 _collector->resetTimer();
|
|
3326 _wallclock.start();
|
|
3327 _collector->startTimer();
|
|
3328 }
|
|
3329
|
|
3330 CMSPhaseAccounting::~CMSPhaseAccounting() {
|
|
3331 assert(_wallclock.is_active(), "Wall clock should not have stopped");
|
|
3332 _collector->stopTimer();
|
|
3333 _wallclock.stop();
|
|
3334 if (PrintGCDetails) {
|
|
3335 gclog_or_tty->date_stamp(PrintGCDateStamps);
|
|
3336 if (PrintGCTimeStamps) {
|
|
3337 gclog_or_tty->stamp();
|
|
3338 gclog_or_tty->print(": ");
|
|
3339 }
|
|
3340 gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]",
|
|
3341 _collector->cmsGen()->short_name(),
|
|
3342 _phase, _collector->timerValue(), _wallclock.seconds());
|
|
3343 if (_print_cr) {
|
|
3344 gclog_or_tty->print_cr("");
|
|
3345 }
|
|
3346 if (PrintCMSStatistics != 0) {
|
|
3347 gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase,
|
|
3348 _collector->yields());
|
|
3349 }
|
|
3350 }
|
|
3351 }
|
|
3352
|
|
3353 // CMS work
|
|
3354
|
|
3355 // Checkpoint the roots into this generation from outside
|
|
3356 // this generation. [Note this initial checkpoint need only
|
|
3357 // be approximate -- we'll do a catch up phase subsequently.]
|
|
3358 void CMSCollector::checkpointRootsInitial(bool asynch) {
|
|
3359 assert(_collectorState == InitialMarking, "Wrong collector state");
|
|
3360 check_correct_thread_executing();
|
|
3361 ReferenceProcessor* rp = ref_processor();
|
|
3362 SpecializationStats::clear();
|
|
3363 assert(_restart_addr == NULL, "Control point invariant");
|
|
3364 if (asynch) {
|
|
3365 // acquire locks for subsequent manipulations
|
|
3366 MutexLockerEx x(bitMapLock(),
|
|
3367 Mutex::_no_safepoint_check_flag);
|
|
3368 checkpointRootsInitialWork(asynch);
|
|
3369 rp->verify_no_references_recorded();
|
|
3370 rp->enable_discovery(); // enable ("weak") refs discovery
|
|
3371 _collectorState = Marking;
|
|
3372 } else {
|
|
3373 // (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection
|
|
3374 // which recognizes if we are a CMS generation, and doesn't try to turn on
|
|
3375 // discovery; verify that they aren't meddling.
|
|
3376 assert(!rp->discovery_is_atomic(),
|
|
3377 "incorrect setting of discovery predicate");
|
|
3378 assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control "
|
|
3379 "ref discovery for this generation kind");
|
|
3380 // already have locks
|
|
3381 checkpointRootsInitialWork(asynch);
|
|
3382 rp->enable_discovery(); // now enable ("weak") refs discovery
|
|
3383 _collectorState = Marking;
|
|
3384 }
|
|
3385 SpecializationStats::print();
|
|
3386 }
|
|
3387
|
|
3388 void CMSCollector::checkpointRootsInitialWork(bool asynch) {
|
|
3389 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped");
|
|
3390 assert(_collectorState == InitialMarking, "just checking");
|
|
3391
|
|
3392 // If there has not been a GC[n-1] since last GC[n] cycle completed,
|
|
3393 // precede our marking with a collection of all
|
|
3394 // younger generations to keep floating garbage to a minimum.
|
|
3395 // XXX: we won't do this for now -- it's an optimization to be done later.
|
|
3396
|
|
3397 // already have locks
|
|
3398 assert_lock_strong(bitMapLock());
|
|
3399 assert(_markBitMap.isAllClear(), "was reset at end of previous cycle");
|
|
3400
|
|
3401 // Setup the verification and class unloading state for this
|
|
3402 // CMS collection cycle.
|
|
3403 setup_cms_unloading_and_verification_state();
|
|
3404
|
|
3405 NOT_PRODUCT(TraceTime t("\ncheckpointRootsInitialWork",
|
|
3406 PrintGCDetails && Verbose, true, gclog_or_tty);)
|
|
3407 if (UseAdaptiveSizePolicy) {
|
|
3408 size_policy()->checkpoint_roots_initial_begin();
|
|
3409 }
|
|
3410
|
|
3411 // Reset all the PLAB chunk arrays if necessary.
|
|
3412 if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) {
|
|
3413 reset_survivor_plab_arrays();
|
|
3414 }
|
|
3415
|
|
3416 ResourceMark rm;
|
|
3417 HandleMark hm;
|
|
3418
|
|
3419 FalseClosure falseClosure;
|
|
3420 // In the case of a synchronous collection, we will elide the
|
|
3421 // remark step, so it's important to catch all the nmethod oops
|
|
3422 // in this step; hence the last argument to the constrcutor below.
|
|
3423 MarkRefsIntoClosure notOlder(_span, &_markBitMap, !asynch /* nmethods */);
|
|
3424 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
3425
|
|
3426 verify_work_stacks_empty();
|
|
3427 verify_overflow_empty();
|
|
3428
|
|
3429 gch->ensure_parsability(false); // fill TLABs, but no need to retire them
|
|
3430 // Update the saved marks which may affect the root scans.
|
|
3431 gch->save_marks();
|
|
3432
|
|
3433 // weak reference processing has not started yet.
|
|
3434 ref_processor()->set_enqueuing_is_done(false);
|
|
3435
|
|
3436 {
|
|
3437 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;)
|
|
3438 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel.
|
|
3439 gch->gen_process_strong_roots(_cmsGen->level(),
|
|
3440 true, // younger gens are roots
|
|
3441 true, // collecting perm gen
|
|
3442 SharedHeap::ScanningOption(roots_scanning_options()),
|
|
3443 NULL, ¬Older);
|
|
3444 }
|
|
3445
|
|
3446 // Clear mod-union table; it will be dirtied in the prologue of
|
|
3447 // CMS generation per each younger generation collection.
|
|
3448
|
|
3449 assert(_modUnionTable.isAllClear(),
|
|
3450 "Was cleared in most recent final checkpoint phase"
|
|
3451 " or no bits are set in the gc_prologue before the start of the next "
|
|
3452 "subsequent marking phase.");
|
|
3453
|
|
3454 // Temporarily disabled, since pre/post-consumption closures don't
|
|
3455 // care about precleaned cards
|
|
3456 #if 0
|
|
3457 {
|
|
3458 MemRegion mr = MemRegion((HeapWord*)_virtual_space.low(),
|
|
3459 (HeapWord*)_virtual_space.high());
|
|
3460 _ct->ct_bs()->preclean_dirty_cards(mr);
|
|
3461 }
|
|
3462 #endif
|
|
3463
|
|
3464 // Save the end of the used_region of the constituent generations
|
|
3465 // to be used to limit the extent of sweep in each generation.
|
|
3466 save_sweep_limits();
|
|
3467 if (UseAdaptiveSizePolicy) {
|
|
3468 size_policy()->checkpoint_roots_initial_end(gch->gc_cause());
|
|
3469 }
|
|
3470 verify_overflow_empty();
|
|
3471 }
|
|
3472
|
|
3473 bool CMSCollector::markFromRoots(bool asynch) {
|
|
3474 // we might be tempted to assert that:
|
|
3475 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
|
|
3476 // "inconsistent argument?");
|
|
3477 // However that wouldn't be right, because it's possible that
|
|
3478 // a safepoint is indeed in progress as a younger generation
|
|
3479 // stop-the-world GC happens even as we mark in this generation.
|
|
3480 assert(_collectorState == Marking, "inconsistent state?");
|
|
3481 check_correct_thread_executing();
|
|
3482 verify_overflow_empty();
|
|
3483
|
|
3484 bool res;
|
|
3485 if (asynch) {
|
|
3486
|
|
3487 // Start the timers for adaptive size policy for the concurrent phases
|
|
3488 // Do it here so that the foreground MS can use the concurrent
|
|
3489 // timer since a foreground MS might has the sweep done concurrently
|
|
3490 // or STW.
|
|
3491 if (UseAdaptiveSizePolicy) {
|
|
3492 size_policy()->concurrent_marking_begin();
|
|
3493 }
|
|
3494
|
|
3495 // Weak ref discovery note: We may be discovering weak
|
|
3496 // refs in this generation concurrent (but interleaved) with
|
|
3497 // weak ref discovery by a younger generation collector.
|
|
3498
|
|
3499 CMSTokenSyncWithLocks ts(true, bitMapLock());
|
|
3500 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
|
|
3501 CMSPhaseAccounting pa(this, "mark", !PrintGCDetails);
|
|
3502 res = markFromRootsWork(asynch);
|
|
3503 if (res) {
|
|
3504 _collectorState = Precleaning;
|
|
3505 } else { // We failed and a foreground collection wants to take over
|
|
3506 assert(_foregroundGCIsActive, "internal state inconsistency");
|
|
3507 assert(_restart_addr == NULL, "foreground will restart from scratch");
|
|
3508 if (PrintGCDetails) {
|
|
3509 gclog_or_tty->print_cr("bailing out to foreground collection");
|
|
3510 }
|
|
3511 }
|
|
3512 if (UseAdaptiveSizePolicy) {
|
|
3513 size_policy()->concurrent_marking_end();
|
|
3514 }
|
|
3515 } else {
|
|
3516 assert(SafepointSynchronize::is_at_safepoint(),
|
|
3517 "inconsistent with asynch == false");
|
|
3518 if (UseAdaptiveSizePolicy) {
|
|
3519 size_policy()->ms_collection_marking_begin();
|
|
3520 }
|
|
3521 // already have locks
|
|
3522 res = markFromRootsWork(asynch);
|
|
3523 _collectorState = FinalMarking;
|
|
3524 if (UseAdaptiveSizePolicy) {
|
|
3525 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
3526 size_policy()->ms_collection_marking_end(gch->gc_cause());
|
|
3527 }
|
|
3528 }
|
|
3529 verify_overflow_empty();
|
|
3530 return res;
|
|
3531 }
|
|
3532
|
|
3533 bool CMSCollector::markFromRootsWork(bool asynch) {
|
|
3534 // iterate over marked bits in bit map, doing a full scan and mark
|
|
3535 // from these roots using the following algorithm:
|
|
3536 // . if oop is to the right of the current scan pointer,
|
|
3537 // mark corresponding bit (we'll process it later)
|
|
3538 // . else (oop is to left of current scan pointer)
|
|
3539 // push oop on marking stack
|
|
3540 // . drain the marking stack
|
|
3541
|
|
3542 // Note that when we do a marking step we need to hold the
|
|
3543 // bit map lock -- recall that direct allocation (by mutators)
|
|
3544 // and promotion (by younger generation collectors) is also
|
|
3545 // marking the bit map. [the so-called allocate live policy.]
|
|
3546 // Because the implementation of bit map marking is not
|
|
3547 // robust wrt simultaneous marking of bits in the same word,
|
|
3548 // we need to make sure that there is no such interference
|
|
3549 // between concurrent such updates.
|
|
3550
|
|
3551 // already have locks
|
|
3552 assert_lock_strong(bitMapLock());
|
|
3553
|
|
3554 // Clear the revisit stack, just in case there are any
|
|
3555 // obsolete contents from a short-circuited previous CMS cycle.
|
|
3556 _revisitStack.reset();
|
|
3557 verify_work_stacks_empty();
|
|
3558 verify_overflow_empty();
|
|
3559 assert(_revisitStack.isEmpty(), "tabula rasa");
|
|
3560
|
|
3561 bool result = false;
|
|
3562 if (CMSConcurrentMTEnabled && ParallelCMSThreads > 0) {
|
|
3563 result = do_marking_mt(asynch);
|
|
3564 } else {
|
|
3565 result = do_marking_st(asynch);
|
|
3566 }
|
|
3567 return result;
|
|
3568 }
|
|
3569
|
|
3570 // Forward decl
|
|
3571 class CMSConcMarkingTask;
|
|
3572
|
|
3573 class CMSConcMarkingTerminator: public ParallelTaskTerminator {
|
|
3574 CMSCollector* _collector;
|
|
3575 CMSConcMarkingTask* _task;
|
|
3576 bool _yield;
|
|
3577 protected:
|
|
3578 virtual void yield();
|
|
3579 public:
|
|
3580 // "n_threads" is the number of threads to be terminated.
|
|
3581 // "queue_set" is a set of work queues of other threads.
|
|
3582 // "collector" is the CMS collector associated with this task terminator.
|
|
3583 // "yield" indicates whether we need the gang as a whole to yield.
|
|
3584 CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set,
|
|
3585 CMSCollector* collector, bool yield) :
|
|
3586 ParallelTaskTerminator(n_threads, queue_set),
|
|
3587 _collector(collector),
|
|
3588 _yield(yield) { }
|
|
3589
|
|
3590 void set_task(CMSConcMarkingTask* task) {
|
|
3591 _task = task;
|
|
3592 }
|
|
3593 };
|
|
3594
|
|
3595 // MT Concurrent Marking Task
|
|
3596 class CMSConcMarkingTask: public YieldingFlexibleGangTask {
|
|
3597 CMSCollector* _collector;
|
|
3598 YieldingFlexibleWorkGang* _workers; // the whole gang
|
|
3599 int _n_workers; // requested/desired # workers
|
|
3600 bool _asynch;
|
|
3601 bool _result;
|
|
3602 CompactibleFreeListSpace* _cms_space;
|
|
3603 CompactibleFreeListSpace* _perm_space;
|
|
3604 HeapWord* _global_finger;
|
|
3605
|
|
3606 // Exposed here for yielding support
|
|
3607 Mutex* const _bit_map_lock;
|
|
3608
|
|
3609 // The per thread work queues, available here for stealing
|
|
3610 OopTaskQueueSet* _task_queues;
|
|
3611 CMSConcMarkingTerminator _term;
|
|
3612
|
|
3613 public:
|
|
3614 CMSConcMarkingTask(CMSCollector* collector,
|
|
3615 CompactibleFreeListSpace* cms_space,
|
|
3616 CompactibleFreeListSpace* perm_space,
|
|
3617 bool asynch, int n_workers,
|
|
3618 YieldingFlexibleWorkGang* workers,
|
|
3619 OopTaskQueueSet* task_queues):
|
|
3620 YieldingFlexibleGangTask("Concurrent marking done multi-threaded"),
|
|
3621 _collector(collector),
|
|
3622 _cms_space(cms_space),
|
|
3623 _perm_space(perm_space),
|
|
3624 _asynch(asynch), _n_workers(n_workers), _result(true),
|
|
3625 _workers(workers), _task_queues(task_queues),
|
|
3626 _term(n_workers, task_queues, _collector, asynch),
|
|
3627 _bit_map_lock(collector->bitMapLock())
|
|
3628 {
|
|
3629 assert(n_workers <= workers->total_workers(),
|
|
3630 "Else termination won't work correctly today"); // XXX FIX ME!
|
|
3631 _requested_size = n_workers;
|
|
3632 _term.set_task(this);
|
|
3633 assert(_cms_space->bottom() < _perm_space->bottom(),
|
|
3634 "Finger incorrectly initialized below");
|
|
3635 _global_finger = _cms_space->bottom();
|
|
3636 }
|
|
3637
|
|
3638
|
|
3639 OopTaskQueueSet* task_queues() { return _task_queues; }
|
|
3640
|
|
3641 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); }
|
|
3642
|
|
3643 HeapWord** global_finger_addr() { return &_global_finger; }
|
|
3644
|
|
3645 CMSConcMarkingTerminator* terminator() { return &_term; }
|
|
3646
|
|
3647 void work(int i);
|
|
3648
|
|
3649 virtual void coordinator_yield(); // stuff done by coordinator
|
|
3650 bool result() { return _result; }
|
|
3651
|
|
3652 void reset(HeapWord* ra) {
|
|
3653 _term.reset_for_reuse();
|
|
3654 }
|
|
3655
|
|
3656 static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk,
|
|
3657 OopTaskQueue* work_q);
|
|
3658
|
|
3659 private:
|
|
3660 void do_scan_and_mark(int i, CompactibleFreeListSpace* sp);
|
|
3661 void do_work_steal(int i);
|
|
3662 void bump_global_finger(HeapWord* f);
|
|
3663 };
|
|
3664
|
|
3665 void CMSConcMarkingTerminator::yield() {
|
|
3666 if (ConcurrentMarkSweepThread::should_yield() &&
|
|
3667 !_collector->foregroundGCIsActive() &&
|
|
3668 _yield) {
|
|
3669 _task->yield();
|
|
3670 } else {
|
|
3671 ParallelTaskTerminator::yield();
|
|
3672 }
|
|
3673 }
|
|
3674
|
|
3675 ////////////////////////////////////////////////////////////////
|
|
3676 // Concurrent Marking Algorithm Sketch
|
|
3677 ////////////////////////////////////////////////////////////////
|
|
3678 // Until all tasks exhausted (both spaces):
|
|
3679 // -- claim next available chunk
|
|
3680 // -- bump global finger via CAS
|
|
3681 // -- find first object that starts in this chunk
|
|
3682 // and start scanning bitmap from that position
|
|
3683 // -- scan marked objects for oops
|
|
3684 // -- CAS-mark target, and if successful:
|
|
3685 // . if target oop is above global finger (volatile read)
|
|
3686 // nothing to do
|
|
3687 // . if target oop is in chunk and above local finger
|
|
3688 // then nothing to do
|
|
3689 // . else push on work-queue
|
|
3690 // -- Deal with possible overflow issues:
|
|
3691 // . local work-queue overflow causes stuff to be pushed on
|
|
3692 // global (common) overflow queue
|
|
3693 // . always first empty local work queue
|
|
3694 // . then get a batch of oops from global work queue if any
|
|
3695 // . then do work stealing
|
|
3696 // -- When all tasks claimed (both spaces)
|
|
3697 // and local work queue empty,
|
|
3698 // then in a loop do:
|
|
3699 // . check global overflow stack; steal a batch of oops and trace
|
|
3700 // . try to steal from other threads oif GOS is empty
|
|
3701 // . if neither is available, offer termination
|
|
3702 // -- Terminate and return result
|
|
3703 //
|
|
3704 void CMSConcMarkingTask::work(int i) {
|
|
3705 elapsedTimer _timer;
|
|
3706 ResourceMark rm;
|
|
3707 HandleMark hm;
|
|
3708
|
|
3709 DEBUG_ONLY(_collector->verify_overflow_empty();)
|
|
3710
|
|
3711 // Before we begin work, our work queue should be empty
|
|
3712 assert(work_queue(i)->size() == 0, "Expected to be empty");
|
|
3713 // Scan the bitmap covering _cms_space, tracing through grey objects.
|
|
3714 _timer.start();
|
|
3715 do_scan_and_mark(i, _cms_space);
|
|
3716 _timer.stop();
|
|
3717 if (PrintCMSStatistics != 0) {
|
|
3718 gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec",
|
|
3719 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers
|
|
3720 }
|
|
3721
|
|
3722 // ... do the same for the _perm_space
|
|
3723 _timer.reset();
|
|
3724 _timer.start();
|
|
3725 do_scan_and_mark(i, _perm_space);
|
|
3726 _timer.stop();
|
|
3727 if (PrintCMSStatistics != 0) {
|
|
3728 gclog_or_tty->print_cr("Finished perm space scanning in %dth thread: %3.3f sec",
|
|
3729 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers
|
|
3730 }
|
|
3731
|
|
3732 // ... do work stealing
|
|
3733 _timer.reset();
|
|
3734 _timer.start();
|
|
3735 do_work_steal(i);
|
|
3736 _timer.stop();
|
|
3737 if (PrintCMSStatistics != 0) {
|
|
3738 gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec",
|
|
3739 i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers
|
|
3740 }
|
|
3741 assert(_collector->_markStack.isEmpty(), "Should have been emptied");
|
|
3742 assert(work_queue(i)->size() == 0, "Should have been emptied");
|
|
3743 // Note that under the current task protocol, the
|
|
3744 // following assertion is true even of the spaces
|
|
3745 // expanded since the completion of the concurrent
|
|
3746 // marking. XXX This will likely change under a strict
|
|
3747 // ABORT semantics.
|
|
3748 assert(_global_finger > _cms_space->end() &&
|
|
3749 _global_finger >= _perm_space->end(),
|
|
3750 "All tasks have been completed");
|
|
3751 DEBUG_ONLY(_collector->verify_overflow_empty();)
|
|
3752 }
|
|
3753
|
|
3754 void CMSConcMarkingTask::bump_global_finger(HeapWord* f) {
|
|
3755 HeapWord* read = _global_finger;
|
|
3756 HeapWord* cur = read;
|
|
3757 while (f > read) {
|
|
3758 cur = read;
|
|
3759 read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur);
|
|
3760 if (cur == read) {
|
|
3761 // our cas succeeded
|
|
3762 assert(_global_finger >= f, "protocol consistency");
|
|
3763 break;
|
|
3764 }
|
|
3765 }
|
|
3766 }
|
|
3767
|
|
3768 // This is really inefficient, and should be redone by
|
|
3769 // using (not yet available) block-read and -write interfaces to the
|
|
3770 // stack and the work_queue. XXX FIX ME !!!
|
|
3771 bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk,
|
|
3772 OopTaskQueue* work_q) {
|
|
3773 // Fast lock-free check
|
|
3774 if (ovflw_stk->length() == 0) {
|
|
3775 return false;
|
|
3776 }
|
|
3777 assert(work_q->size() == 0, "Shouldn't steal");
|
|
3778 MutexLockerEx ml(ovflw_stk->par_lock(),
|
|
3779 Mutex::_no_safepoint_check_flag);
|
|
3780 // Grab up to 1/4 the size of the work queue
|
|
3781 size_t num = MIN2((size_t)work_q->max_elems()/4,
|
|
3782 (size_t)ParGCDesiredObjsFromOverflowList);
|
|
3783 num = MIN2(num, ovflw_stk->length());
|
|
3784 for (int i = (int) num; i > 0; i--) {
|
|
3785 oop cur = ovflw_stk->pop();
|
|
3786 assert(cur != NULL, "Counted wrong?");
|
|
3787 work_q->push(cur);
|
|
3788 }
|
|
3789 return num > 0;
|
|
3790 }
|
|
3791
|
|
3792 void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) {
|
|
3793 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks();
|
|
3794 int n_tasks = pst->n_tasks();
|
|
3795 // We allow that there may be no tasks to do here because
|
|
3796 // we are restarting after a stack overflow.
|
|
3797 assert(pst->valid() || n_tasks == 0, "Uninitializd use?");
|
|
3798 int nth_task = 0;
|
|
3799
|
|
3800 HeapWord* start = sp->bottom();
|
|
3801 size_t chunk_size = sp->marking_task_size();
|
|
3802 while (!pst->is_task_claimed(/* reference */ nth_task)) {
|
|
3803 // Having claimed the nth task in this space,
|
|
3804 // compute the chunk that it corresponds to:
|
|
3805 MemRegion span = MemRegion(start + nth_task*chunk_size,
|
|
3806 start + (nth_task+1)*chunk_size);
|
|
3807 // Try and bump the global finger via a CAS;
|
|
3808 // note that we need to do the global finger bump
|
|
3809 // _before_ taking the intersection below, because
|
|
3810 // the task corresponding to that region will be
|
|
3811 // deemed done even if the used_region() expands
|
|
3812 // because of allocation -- as it almost certainly will
|
|
3813 // during start-up while the threads yield in the
|
|
3814 // closure below.
|
|
3815 HeapWord* finger = span.end();
|
|
3816 bump_global_finger(finger); // atomically
|
|
3817 // There are null tasks here corresponding to chunks
|
|
3818 // beyond the "top" address of the space.
|
|
3819 span = span.intersection(sp->used_region());
|
|
3820 if (!span.is_empty()) { // Non-null task
|
|
3821 // We want to skip the first object because
|
|
3822 // the protocol is to scan any object in its entirety
|
|
3823 // that _starts_ in this span; a fortiori, any
|
|
3824 // object starting in an earlier span is scanned
|
|
3825 // as part of an earlier claimed task.
|
|
3826 // Below we use the "careful" version of block_start
|
|
3827 // so we do not try to navigate uninitialized objects.
|
|
3828 HeapWord* prev_obj = sp->block_start_careful(span.start());
|
|
3829 // Below we use a variant of block_size that uses the
|
|
3830 // Printezis bits to avoid waiting for allocated
|
|
3831 // objects to become initialized/parsable.
|
|
3832 while (prev_obj < span.start()) {
|
|
3833 size_t sz = sp->block_size_no_stall(prev_obj, _collector);
|
|
3834 if (sz > 0) {
|
|
3835 prev_obj += sz;
|
|
3836 } else {
|
|
3837 // In this case we may end up doing a bit of redundant
|
|
3838 // scanning, but that appears unavoidable, short of
|
|
3839 // locking the free list locks; see bug 6324141.
|
|
3840 break;
|
|
3841 }
|
|
3842 }
|
|
3843 if (prev_obj < span.end()) {
|
|
3844 MemRegion my_span = MemRegion(prev_obj, span.end());
|
|
3845 // Do the marking work within a non-empty span --
|
|
3846 // the last argument to the constructor indicates whether the
|
|
3847 // iteration should be incremental with periodic yields.
|
|
3848 Par_MarkFromRootsClosure cl(this, _collector, my_span,
|
|
3849 &_collector->_markBitMap,
|
|
3850 work_queue(i),
|
|
3851 &_collector->_markStack,
|
|
3852 &_collector->_revisitStack,
|
|
3853 _asynch);
|
|
3854 _collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end());
|
|
3855 } // else nothing to do for this task
|
|
3856 } // else nothing to do for this task
|
|
3857 }
|
|
3858 // We'd be tempted to assert here that since there are no
|
|
3859 // more tasks left to claim in this space, the global_finger
|
|
3860 // must exceed space->top() and a fortiori space->end(). However,
|
|
3861 // that would not quite be correct because the bumping of
|
|
3862 // global_finger occurs strictly after the claiming of a task,
|
|
3863 // so by the time we reach here the global finger may not yet
|
|
3864 // have been bumped up by the thread that claimed the last
|
|
3865 // task.
|
|
3866 pst->all_tasks_completed();
|
|
3867 }
|
|
3868
|
|
3869 class Par_ConcMarkingClosure: public OopClosure {
|
|
3870 CMSCollector* _collector;
|
|
3871 MemRegion _span;
|
|
3872 CMSBitMap* _bit_map;
|
|
3873 CMSMarkStack* _overflow_stack;
|
|
3874 CMSMarkStack* _revisit_stack; // XXXXXX Check proper use
|
|
3875 OopTaskQueue* _work_queue;
|
|
3876
|
|
3877 public:
|
|
3878 Par_ConcMarkingClosure(CMSCollector* collector, OopTaskQueue* work_queue,
|
|
3879 CMSBitMap* bit_map, CMSMarkStack* overflow_stack):
|
|
3880 _collector(collector),
|
|
3881 _span(_collector->_span),
|
|
3882 _work_queue(work_queue),
|
|
3883 _bit_map(bit_map),
|
|
3884 _overflow_stack(overflow_stack) { } // need to initialize revisit stack etc.
|
|
3885
|
|
3886 void do_oop(oop* p);
|
|
3887 void trim_queue(size_t max);
|
|
3888 void handle_stack_overflow(HeapWord* lost);
|
|
3889 };
|
|
3890
|
|
3891 // Grey object rescan during work stealing phase --
|
|
3892 // the salient assumption here is that stolen oops must
|
|
3893 // always be initialized, so we do not need to check for
|
|
3894 // uninitialized objects before scanning here.
|
|
3895 void Par_ConcMarkingClosure::do_oop(oop* p) {
|
|
3896 oop this_oop = *p;
|
|
3897 assert(this_oop->is_oop_or_null(),
|
|
3898 "expected an oop or NULL");
|
|
3899 HeapWord* addr = (HeapWord*)this_oop;
|
|
3900 // Check if oop points into the CMS generation
|
|
3901 // and is not marked
|
|
3902 if (_span.contains(addr) && !_bit_map->isMarked(addr)) {
|
|
3903 // a white object ...
|
|
3904 // If we manage to "claim" the object, by being the
|
|
3905 // first thread to mark it, then we push it on our
|
|
3906 // marking stack
|
|
3907 if (_bit_map->par_mark(addr)) { // ... now grey
|
|
3908 // push on work queue (grey set)
|
|
3909 bool simulate_overflow = false;
|
|
3910 NOT_PRODUCT(
|
|
3911 if (CMSMarkStackOverflowALot &&
|
|
3912 _collector->simulate_overflow()) {
|
|
3913 // simulate a stack overflow
|
|
3914 simulate_overflow = true;
|
|
3915 }
|
|
3916 )
|
|
3917 if (simulate_overflow ||
|
|
3918 !(_work_queue->push(this_oop) || _overflow_stack->par_push(this_oop))) {
|
|
3919 // stack overflow
|
|
3920 if (PrintCMSStatistics != 0) {
|
|
3921 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at "
|
|
3922 SIZE_FORMAT, _overflow_stack->capacity());
|
|
3923 }
|
|
3924 // We cannot assert that the overflow stack is full because
|
|
3925 // it may have been emptied since.
|
|
3926 assert(simulate_overflow ||
|
|
3927 _work_queue->size() == _work_queue->max_elems(),
|
|
3928 "Else push should have succeeded");
|
|
3929 handle_stack_overflow(addr);
|
|
3930 }
|
|
3931 } // Else, some other thread got there first
|
|
3932 }
|
|
3933 }
|
|
3934
|
|
3935 void Par_ConcMarkingClosure::trim_queue(size_t max) {
|
|
3936 while (_work_queue->size() > max) {
|
|
3937 oop new_oop;
|
|
3938 if (_work_queue->pop_local(new_oop)) {
|
|
3939 assert(new_oop->is_oop(), "Should be an oop");
|
|
3940 assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object");
|
|
3941 assert(_span.contains((HeapWord*)new_oop), "Not in span");
|
|
3942 assert(new_oop->is_parsable(), "Should be parsable");
|
|
3943 new_oop->oop_iterate(this); // do_oop() above
|
|
3944 }
|
|
3945 }
|
|
3946 }
|
|
3947
|
|
3948 // Upon stack overflow, we discard (part of) the stack,
|
|
3949 // remembering the least address amongst those discarded
|
|
3950 // in CMSCollector's _restart_address.
|
|
3951 void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) {
|
|
3952 // We need to do this under a mutex to prevent other
|
|
3953 // workers from interfering with the expansion below.
|
|
3954 MutexLockerEx ml(_overflow_stack->par_lock(),
|
|
3955 Mutex::_no_safepoint_check_flag);
|
|
3956 // Remember the least grey address discarded
|
|
3957 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost);
|
|
3958 _collector->lower_restart_addr(ra);
|
|
3959 _overflow_stack->reset(); // discard stack contents
|
|
3960 _overflow_stack->expand(); // expand the stack if possible
|
|
3961 }
|
|
3962
|
|
3963
|
|
3964 void CMSConcMarkingTask::do_work_steal(int i) {
|
|
3965 OopTaskQueue* work_q = work_queue(i);
|
|
3966 oop obj_to_scan;
|
|
3967 CMSBitMap* bm = &(_collector->_markBitMap);
|
|
3968 CMSMarkStack* ovflw = &(_collector->_markStack);
|
|
3969 int* seed = _collector->hash_seed(i);
|
|
3970 Par_ConcMarkingClosure cl(_collector, work_q, bm, ovflw);
|
|
3971 while (true) {
|
|
3972 cl.trim_queue(0);
|
|
3973 assert(work_q->size() == 0, "Should have been emptied above");
|
|
3974 if (get_work_from_overflow_stack(ovflw, work_q)) {
|
|
3975 // Can't assert below because the work obtained from the
|
|
3976 // overflow stack may already have been stolen from us.
|
|
3977 // assert(work_q->size() > 0, "Work from overflow stack");
|
|
3978 continue;
|
|
3979 } else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) {
|
|
3980 assert(obj_to_scan->is_oop(), "Should be an oop");
|
|
3981 assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object");
|
|
3982 obj_to_scan->oop_iterate(&cl);
|
|
3983 } else if (terminator()->offer_termination()) {
|
|
3984 assert(work_q->size() == 0, "Impossible!");
|
|
3985 break;
|
|
3986 }
|
|
3987 }
|
|
3988 }
|
|
3989
|
|
3990 // This is run by the CMS (coordinator) thread.
|
|
3991 void CMSConcMarkingTask::coordinator_yield() {
|
|
3992 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
3993 "CMS thread should hold CMS token");
|
|
3994
|
|
3995 // First give up the locks, then yield, then re-lock
|
|
3996 // We should probably use a constructor/destructor idiom to
|
|
3997 // do this unlock/lock or modify the MutexUnlocker class to
|
|
3998 // serve our purpose. XXX
|
|
3999 assert_lock_strong(_bit_map_lock);
|
|
4000 _bit_map_lock->unlock();
|
|
4001 ConcurrentMarkSweepThread::desynchronize(true);
|
|
4002 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
4003 _collector->stopTimer();
|
|
4004 if (PrintCMSStatistics != 0) {
|
|
4005 _collector->incrementYields();
|
|
4006 }
|
|
4007 _collector->icms_wait();
|
|
4008
|
|
4009 // It is possible for whichever thread initiated the yield request
|
|
4010 // not to get a chance to wake up and take the bitmap lock between
|
|
4011 // this thread releasing it and reacquiring it. So, while the
|
|
4012 // should_yield() flag is on, let's sleep for a bit to give the
|
|
4013 // other thread a chance to wake up. The limit imposed on the number
|
|
4014 // of iterations is defensive, to avoid any unforseen circumstances
|
|
4015 // putting us into an infinite loop. Since it's always been this
|
|
4016 // (coordinator_yield()) method that was observed to cause the
|
|
4017 // problem, we are using a parameter (CMSCoordinatorYieldSleepCount)
|
|
4018 // which is by default non-zero. For the other seven methods that
|
|
4019 // also perform the yield operation, as are using a different
|
|
4020 // parameter (CMSYieldSleepCount) which is by default zero. This way we
|
|
4021 // can enable the sleeping for those methods too, if necessary.
|
|
4022 // See 6442774.
|
|
4023 //
|
|
4024 // We really need to reconsider the synchronization between the GC
|
|
4025 // thread and the yield-requesting threads in the future and we
|
|
4026 // should really use wait/notify, which is the recommended
|
|
4027 // way of doing this type of interaction. Additionally, we should
|
|
4028 // consolidate the eight methods that do the yield operation and they
|
|
4029 // are almost identical into one for better maintenability and
|
|
4030 // readability. See 6445193.
|
|
4031 //
|
|
4032 // Tony 2006.06.29
|
|
4033 for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount &&
|
|
4034 ConcurrentMarkSweepThread::should_yield() &&
|
|
4035 !CMSCollector::foregroundGCIsActive(); ++i) {
|
|
4036 os::sleep(Thread::current(), 1, false);
|
|
4037 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
4038 }
|
|
4039
|
|
4040 ConcurrentMarkSweepThread::synchronize(true);
|
|
4041 _bit_map_lock->lock_without_safepoint_check();
|
|
4042 _collector->startTimer();
|
|
4043 }
|
|
4044
|
|
4045 bool CMSCollector::do_marking_mt(bool asynch) {
|
|
4046 assert(ParallelCMSThreads > 0 && conc_workers() != NULL, "precondition");
|
|
4047 // In the future this would be determined ergonomically, based
|
|
4048 // on #cpu's, # active mutator threads (and load), and mutation rate.
|
|
4049 int num_workers = ParallelCMSThreads;
|
|
4050
|
|
4051 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace();
|
|
4052 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace();
|
|
4053
|
|
4054 CMSConcMarkingTask tsk(this, cms_space, perm_space,
|
|
4055 asynch, num_workers /* number requested XXX */,
|
|
4056 conc_workers(), task_queues());
|
|
4057
|
|
4058 // Since the actual number of workers we get may be different
|
|
4059 // from the number we requested above, do we need to do anything different
|
|
4060 // below? In particular, may be we need to subclass the SequantialSubTasksDone
|
|
4061 // class?? XXX
|
|
4062 cms_space ->initialize_sequential_subtasks_for_marking(num_workers);
|
|
4063 perm_space->initialize_sequential_subtasks_for_marking(num_workers);
|
|
4064
|
|
4065 // Refs discovery is already non-atomic.
|
|
4066 assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic");
|
|
4067 // Mutate the Refs discovery so it is MT during the
|
|
4068 // multi-threaded marking phase.
|
|
4069 ReferenceProcessorMTMutator mt(ref_processor(), num_workers > 1);
|
|
4070
|
|
4071 conc_workers()->start_task(&tsk);
|
|
4072 while (tsk.yielded()) {
|
|
4073 tsk.coordinator_yield();
|
|
4074 conc_workers()->continue_task(&tsk);
|
|
4075 }
|
|
4076 // If the task was aborted, _restart_addr will be non-NULL
|
|
4077 assert(tsk.completed() || _restart_addr != NULL, "Inconsistency");
|
|
4078 while (_restart_addr != NULL) {
|
|
4079 // XXX For now we do not make use of ABORTED state and have not
|
|
4080 // yet implemented the right abort semantics (even in the original
|
|
4081 // single-threaded CMS case). That needs some more investigation
|
|
4082 // and is deferred for now; see CR# TBF. 07252005YSR. XXX
|
|
4083 assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency");
|
|
4084 // If _restart_addr is non-NULL, a marking stack overflow
|
|
4085 // occured; we need to do a fresh marking iteration from the
|
|
4086 // indicated restart address.
|
|
4087 if (_foregroundGCIsActive && asynch) {
|
|
4088 // We may be running into repeated stack overflows, having
|
|
4089 // reached the limit of the stack size, while making very
|
|
4090 // slow forward progress. It may be best to bail out and
|
|
4091 // let the foreground collector do its job.
|
|
4092 // Clear _restart_addr, so that foreground GC
|
|
4093 // works from scratch. This avoids the headache of
|
|
4094 // a "rescan" which would otherwise be needed because
|
|
4095 // of the dirty mod union table & card table.
|
|
4096 _restart_addr = NULL;
|
|
4097 return false;
|
|
4098 }
|
|
4099 // Adjust the task to restart from _restart_addr
|
|
4100 tsk.reset(_restart_addr);
|
|
4101 cms_space ->initialize_sequential_subtasks_for_marking(num_workers,
|
|
4102 _restart_addr);
|
|
4103 perm_space->initialize_sequential_subtasks_for_marking(num_workers,
|
|
4104 _restart_addr);
|
|
4105 _restart_addr = NULL;
|
|
4106 // Get the workers going again
|
|
4107 conc_workers()->start_task(&tsk);
|
|
4108 while (tsk.yielded()) {
|
|
4109 tsk.coordinator_yield();
|
|
4110 conc_workers()->continue_task(&tsk);
|
|
4111 }
|
|
4112 }
|
|
4113 assert(tsk.completed(), "Inconsistency");
|
|
4114 assert(tsk.result() == true, "Inconsistency");
|
|
4115 return true;
|
|
4116 }
|
|
4117
|
|
4118 bool CMSCollector::do_marking_st(bool asynch) {
|
|
4119 ResourceMark rm;
|
|
4120 HandleMark hm;
|
|
4121
|
|
4122 MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap,
|
|
4123 &_markStack, &_revisitStack, CMSYield && asynch);
|
|
4124 // the last argument to iterate indicates whether the iteration
|
|
4125 // should be incremental with periodic yields.
|
|
4126 _markBitMap.iterate(&markFromRootsClosure);
|
|
4127 // If _restart_addr is non-NULL, a marking stack overflow
|
|
4128 // occured; we need to do a fresh iteration from the
|
|
4129 // indicated restart address.
|
|
4130 while (_restart_addr != NULL) {
|
|
4131 if (_foregroundGCIsActive && asynch) {
|
|
4132 // We may be running into repeated stack overflows, having
|
|
4133 // reached the limit of the stack size, while making very
|
|
4134 // slow forward progress. It may be best to bail out and
|
|
4135 // let the foreground collector do its job.
|
|
4136 // Clear _restart_addr, so that foreground GC
|
|
4137 // works from scratch. This avoids the headache of
|
|
4138 // a "rescan" which would otherwise be needed because
|
|
4139 // of the dirty mod union table & card table.
|
|
4140 _restart_addr = NULL;
|
|
4141 return false; // indicating failure to complete marking
|
|
4142 }
|
|
4143 // Deal with stack overflow:
|
|
4144 // we restart marking from _restart_addr
|
|
4145 HeapWord* ra = _restart_addr;
|
|
4146 markFromRootsClosure.reset(ra);
|
|
4147 _restart_addr = NULL;
|
|
4148 _markBitMap.iterate(&markFromRootsClosure, ra, _span.end());
|
|
4149 }
|
|
4150 return true;
|
|
4151 }
|
|
4152
|
|
4153 void CMSCollector::preclean() {
|
|
4154 check_correct_thread_executing();
|
|
4155 assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread");
|
|
4156 verify_work_stacks_empty();
|
|
4157 verify_overflow_empty();
|
|
4158 _abort_preclean = false;
|
|
4159 if (CMSPrecleaningEnabled) {
|
|
4160 _eden_chunk_index = 0;
|
|
4161 size_t used = get_eden_used();
|
|
4162 size_t capacity = get_eden_capacity();
|
|
4163 // Don't start sampling unless we will get sufficiently
|
|
4164 // many samples.
|
|
4165 if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100)
|
|
4166 * CMSScheduleRemarkEdenPenetration)) {
|
|
4167 _start_sampling = true;
|
|
4168 } else {
|
|
4169 _start_sampling = false;
|
|
4170 }
|
|
4171 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
|
|
4172 CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails);
|
|
4173 preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1);
|
|
4174 }
|
|
4175 CMSTokenSync x(true); // is cms thread
|
|
4176 if (CMSPrecleaningEnabled) {
|
|
4177 sample_eden();
|
|
4178 _collectorState = AbortablePreclean;
|
|
4179 } else {
|
|
4180 _collectorState = FinalMarking;
|
|
4181 }
|
|
4182 verify_work_stacks_empty();
|
|
4183 verify_overflow_empty();
|
|
4184 }
|
|
4185
|
|
4186 // Try and schedule the remark such that young gen
|
|
4187 // occupancy is CMSScheduleRemarkEdenPenetration %.
|
|
4188 void CMSCollector::abortable_preclean() {
|
|
4189 check_correct_thread_executing();
|
|
4190 assert(CMSPrecleaningEnabled, "Inconsistent control state");
|
|
4191 assert(_collectorState == AbortablePreclean, "Inconsistent control state");
|
|
4192
|
|
4193 // If Eden's current occupancy is below this threshold,
|
|
4194 // immediately schedule the remark; else preclean
|
|
4195 // past the next scavenge in an effort to
|
|
4196 // schedule the pause as described avove. By choosing
|
|
4197 // CMSScheduleRemarkEdenSizeThreshold >= max eden size
|
|
4198 // we will never do an actual abortable preclean cycle.
|
|
4199 if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) {
|
|
4200 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
|
|
4201 CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails);
|
|
4202 // We need more smarts in the abortable preclean
|
|
4203 // loop below to deal with cases where allocation
|
|
4204 // in young gen is very very slow, and our precleaning
|
|
4205 // is running a losing race against a horde of
|
|
4206 // mutators intent on flooding us with CMS updates
|
|
4207 // (dirty cards).
|
|
4208 // One, admittedly dumb, strategy is to give up
|
|
4209 // after a certain number of abortable precleaning loops
|
|
4210 // or after a certain maximum time. We want to make
|
|
4211 // this smarter in the next iteration.
|
|
4212 // XXX FIX ME!!! YSR
|
|
4213 size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0;
|
|
4214 while (!(should_abort_preclean() ||
|
|
4215 ConcurrentMarkSweepThread::should_terminate())) {
|
|
4216 workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2);
|
|
4217 cumworkdone += workdone;
|
|
4218 loops++;
|
|
4219 // Voluntarily terminate abortable preclean phase if we have
|
|
4220 // been at it for too long.
|
|
4221 if ((CMSMaxAbortablePrecleanLoops != 0) &&
|
|
4222 loops >= CMSMaxAbortablePrecleanLoops) {
|
|
4223 if (PrintGCDetails) {
|
|
4224 gclog_or_tty->print(" CMS: abort preclean due to loops ");
|
|
4225 }
|
|
4226 break;
|
|
4227 }
|
|
4228 if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) {
|
|
4229 if (PrintGCDetails) {
|
|
4230 gclog_or_tty->print(" CMS: abort preclean due to time ");
|
|
4231 }
|
|
4232 break;
|
|
4233 }
|
|
4234 // If we are doing little work each iteration, we should
|
|
4235 // take a short break.
|
|
4236 if (workdone < CMSAbortablePrecleanMinWorkPerIteration) {
|
|
4237 // Sleep for some time, waiting for work to accumulate
|
|
4238 stopTimer();
|
|
4239 cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis);
|
|
4240 startTimer();
|
|
4241 waited++;
|
|
4242 }
|
|
4243 }
|
|
4244 if (PrintCMSStatistics > 0) {
|
|
4245 gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ",
|
|
4246 loops, waited, cumworkdone);
|
|
4247 }
|
|
4248 }
|
|
4249 CMSTokenSync x(true); // is cms thread
|
|
4250 if (_collectorState != Idling) {
|
|
4251 assert(_collectorState == AbortablePreclean,
|
|
4252 "Spontaneous state transition?");
|
|
4253 _collectorState = FinalMarking;
|
|
4254 } // Else, a foreground collection completed this CMS cycle.
|
|
4255 return;
|
|
4256 }
|
|
4257
|
|
4258 // Respond to an Eden sampling opportunity
|
|
4259 void CMSCollector::sample_eden() {
|
|
4260 // Make sure a young gc cannot sneak in between our
|
|
4261 // reading and recording of a sample.
|
|
4262 assert(Thread::current()->is_ConcurrentGC_thread(),
|
|
4263 "Only the cms thread may collect Eden samples");
|
|
4264 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
4265 "Should collect samples while holding CMS token");
|
|
4266 if (!_start_sampling) {
|
|
4267 return;
|
|
4268 }
|
|
4269 if (_eden_chunk_array) {
|
|
4270 if (_eden_chunk_index < _eden_chunk_capacity) {
|
|
4271 _eden_chunk_array[_eden_chunk_index] = *_top_addr; // take sample
|
|
4272 assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr,
|
|
4273 "Unexpected state of Eden");
|
|
4274 // We'd like to check that what we just sampled is an oop-start address;
|
|
4275 // however, we cannot do that here since the object may not yet have been
|
|
4276 // initialized. So we'll instead do the check when we _use_ this sample
|
|
4277 // later.
|
|
4278 if (_eden_chunk_index == 0 ||
|
|
4279 (pointer_delta(_eden_chunk_array[_eden_chunk_index],
|
|
4280 _eden_chunk_array[_eden_chunk_index-1])
|
|
4281 >= CMSSamplingGrain)) {
|
|
4282 _eden_chunk_index++; // commit sample
|
|
4283 }
|
|
4284 }
|
|
4285 }
|
|
4286 if ((_collectorState == AbortablePreclean) && !_abort_preclean) {
|
|
4287 size_t used = get_eden_used();
|
|
4288 size_t capacity = get_eden_capacity();
|
|
4289 assert(used <= capacity, "Unexpected state of Eden");
|
|
4290 if (used > (capacity/100 * CMSScheduleRemarkEdenPenetration)) {
|
|
4291 _abort_preclean = true;
|
|
4292 }
|
|
4293 }
|
|
4294 }
|
|
4295
|
|
4296
|
|
4297 size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) {
|
|
4298 assert(_collectorState == Precleaning ||
|
|
4299 _collectorState == AbortablePreclean, "incorrect state");
|
|
4300 ResourceMark rm;
|
|
4301 HandleMark hm;
|
|
4302 // Do one pass of scrubbing the discovered reference lists
|
|
4303 // to remove any reference objects with strongly-reachable
|
|
4304 // referents.
|
|
4305 if (clean_refs) {
|
|
4306 ReferenceProcessor* rp = ref_processor();
|
|
4307 CMSPrecleanRefsYieldClosure yield_cl(this);
|
|
4308 assert(rp->span().equals(_span), "Spans should be equal");
|
|
4309 CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap,
|
|
4310 &_markStack);
|
|
4311 CMSDrainMarkingStackClosure complete_trace(this,
|
|
4312 _span, &_markBitMap, &_markStack,
|
|
4313 &keep_alive);
|
|
4314
|
|
4315 // We don't want this step to interfere with a young
|
|
4316 // collection because we don't want to take CPU
|
|
4317 // or memory bandwidth away from the young GC threads
|
|
4318 // (which may be as many as there are CPUs).
|
|
4319 // Note that we don't need to protect ourselves from
|
|
4320 // interference with mutators because they can't
|
|
4321 // manipulate the discovered reference lists nor affect
|
|
4322 // the computed reachability of the referents, the
|
|
4323 // only properties manipulated by the precleaning
|
|
4324 // of these reference lists.
|
|
4325 stopTimer();
|
|
4326 CMSTokenSyncWithLocks x(true /* is cms thread */,
|
|
4327 bitMapLock());
|
|
4328 startTimer();
|
|
4329 sample_eden();
|
|
4330 // The following will yield to allow foreground
|
|
4331 // collection to proceed promptly. XXX YSR:
|
|
4332 // The code in this method may need further
|
|
4333 // tweaking for better performance and some restructuring
|
|
4334 // for cleaner interfaces.
|
|
4335 rp->preclean_discovered_references(
|
|
4336 rp->is_alive_non_header(), &keep_alive, &complete_trace,
|
|
4337 &yield_cl);
|
|
4338 }
|
|
4339
|
|
4340 if (clean_survivor) { // preclean the active survivor space(s)
|
|
4341 assert(_young_gen->kind() == Generation::DefNew ||
|
|
4342 _young_gen->kind() == Generation::ParNew ||
|
|
4343 _young_gen->kind() == Generation::ASParNew,
|
|
4344 "incorrect type for cast");
|
|
4345 DefNewGeneration* dng = (DefNewGeneration*)_young_gen;
|
|
4346 PushAndMarkClosure pam_cl(this, _span, ref_processor(),
|
|
4347 &_markBitMap, &_modUnionTable,
|
|
4348 &_markStack, &_revisitStack,
|
|
4349 true /* precleaning phase */);
|
|
4350 stopTimer();
|
|
4351 CMSTokenSyncWithLocks ts(true /* is cms thread */,
|
|
4352 bitMapLock());
|
|
4353 startTimer();
|
|
4354 unsigned int before_count =
|
|
4355 GenCollectedHeap::heap()->total_collections();
|
|
4356 SurvivorSpacePrecleanClosure
|
|
4357 sss_cl(this, _span, &_markBitMap, &_markStack,
|
|
4358 &pam_cl, before_count, CMSYield);
|
|
4359 dng->from()->object_iterate_careful(&sss_cl);
|
|
4360 dng->to()->object_iterate_careful(&sss_cl);
|
|
4361 }
|
|
4362 MarkRefsIntoAndScanClosure
|
|
4363 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable,
|
|
4364 &_markStack, &_revisitStack, this, CMSYield,
|
|
4365 true /* precleaning phase */);
|
|
4366 // CAUTION: The following closure has persistent state that may need to
|
|
4367 // be reset upon a decrease in the sequence of addresses it
|
|
4368 // processes.
|
|
4369 ScanMarkedObjectsAgainCarefullyClosure
|
|
4370 smoac_cl(this, _span,
|
|
4371 &_markBitMap, &_markStack, &_revisitStack, &mrias_cl, CMSYield);
|
|
4372
|
|
4373 // Preclean dirty cards in ModUnionTable and CardTable using
|
|
4374 // appropriate convergence criterion;
|
|
4375 // repeat CMSPrecleanIter times unless we find that
|
|
4376 // we are losing.
|
|
4377 assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large");
|
|
4378 assert(CMSPrecleanNumerator < CMSPrecleanDenominator,
|
|
4379 "Bad convergence multiplier");
|
|
4380 assert(CMSPrecleanThreshold >= 100,
|
|
4381 "Unreasonably low CMSPrecleanThreshold");
|
|
4382
|
|
4383 size_t numIter, cumNumCards, lastNumCards, curNumCards;
|
|
4384 for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0;
|
|
4385 numIter < CMSPrecleanIter;
|
|
4386 numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) {
|
|
4387 curNumCards = preclean_mod_union_table(_cmsGen, &smoac_cl);
|
|
4388 if (CMSPermGenPrecleaningEnabled) {
|
|
4389 curNumCards += preclean_mod_union_table(_permGen, &smoac_cl);
|
|
4390 }
|
|
4391 if (Verbose && PrintGCDetails) {
|
|
4392 gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards);
|
|
4393 }
|
|
4394 // Either there are very few dirty cards, so re-mark
|
|
4395 // pause will be small anyway, or our pre-cleaning isn't
|
|
4396 // that much faster than the rate at which cards are being
|
|
4397 // dirtied, so we might as well stop and re-mark since
|
|
4398 // precleaning won't improve our re-mark time by much.
|
|
4399 if (curNumCards <= CMSPrecleanThreshold ||
|
|
4400 (numIter > 0 &&
|
|
4401 (curNumCards * CMSPrecleanDenominator >
|
|
4402 lastNumCards * CMSPrecleanNumerator))) {
|
|
4403 numIter++;
|
|
4404 cumNumCards += curNumCards;
|
|
4405 break;
|
|
4406 }
|
|
4407 }
|
|
4408 curNumCards = preclean_card_table(_cmsGen, &smoac_cl);
|
|
4409 if (CMSPermGenPrecleaningEnabled) {
|
|
4410 curNumCards += preclean_card_table(_permGen, &smoac_cl);
|
|
4411 }
|
|
4412 cumNumCards += curNumCards;
|
|
4413 if (PrintGCDetails && PrintCMSStatistics != 0) {
|
|
4414 gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)",
|
|
4415 curNumCards, cumNumCards, numIter);
|
|
4416 }
|
|
4417 return cumNumCards; // as a measure of useful work done
|
|
4418 }
|
|
4419
|
|
4420 // PRECLEANING NOTES:
|
|
4421 // Precleaning involves:
|
|
4422 // . reading the bits of the modUnionTable and clearing the set bits.
|
|
4423 // . For the cards corresponding to the set bits, we scan the
|
|
4424 // objects on those cards. This means we need the free_list_lock
|
|
4425 // so that we can safely iterate over the CMS space when scanning
|
|
4426 // for oops.
|
|
4427 // . When we scan the objects, we'll be both reading and setting
|
|
4428 // marks in the marking bit map, so we'll need the marking bit map.
|
|
4429 // . For protecting _collector_state transitions, we take the CGC_lock.
|
|
4430 // Note that any races in the reading of of card table entries by the
|
|
4431 // CMS thread on the one hand and the clearing of those entries by the
|
|
4432 // VM thread or the setting of those entries by the mutator threads on the
|
|
4433 // other are quite benign. However, for efficiency it makes sense to keep
|
|
4434 // the VM thread from racing with the CMS thread while the latter is
|
|
4435 // dirty card info to the modUnionTable. We therefore also use the
|
|
4436 // CGC_lock to protect the reading of the card table and the mod union
|
|
4437 // table by the CM thread.
|
|
4438 // . We run concurrently with mutator updates, so scanning
|
|
4439 // needs to be done carefully -- we should not try to scan
|
|
4440 // potentially uninitialized objects.
|
|
4441 //
|
|
4442 // Locking strategy: While holding the CGC_lock, we scan over and
|
|
4443 // reset a maximal dirty range of the mod union / card tables, then lock
|
|
4444 // the free_list_lock and bitmap lock to do a full marking, then
|
|
4445 // release these locks; and repeat the cycle. This allows for a
|
|
4446 // certain amount of fairness in the sharing of these locks between
|
|
4447 // the CMS collector on the one hand, and the VM thread and the
|
|
4448 // mutators on the other.
|
|
4449
|
|
4450 // NOTE: preclean_mod_union_table() and preclean_card_table()
|
|
4451 // further below are largely identical; if you need to modify
|
|
4452 // one of these methods, please check the other method too.
|
|
4453
|
|
4454 size_t CMSCollector::preclean_mod_union_table(
|
|
4455 ConcurrentMarkSweepGeneration* gen,
|
|
4456 ScanMarkedObjectsAgainCarefullyClosure* cl) {
|
|
4457 verify_work_stacks_empty();
|
|
4458 verify_overflow_empty();
|
|
4459
|
|
4460 // strategy: starting with the first card, accumulate contiguous
|
|
4461 // ranges of dirty cards; clear these cards, then scan the region
|
|
4462 // covered by these cards.
|
|
4463
|
|
4464 // Since all of the MUT is committed ahead, we can just use
|
|
4465 // that, in case the generations expand while we are precleaning.
|
|
4466 // It might also be fine to just use the committed part of the
|
|
4467 // generation, but we might potentially miss cards when the
|
|
4468 // generation is rapidly expanding while we are in the midst
|
|
4469 // of precleaning.
|
|
4470 HeapWord* startAddr = gen->reserved().start();
|
|
4471 HeapWord* endAddr = gen->reserved().end();
|
|
4472
|
|
4473 cl->setFreelistLock(gen->freelistLock()); // needed for yielding
|
|
4474
|
|
4475 size_t numDirtyCards, cumNumDirtyCards;
|
|
4476 HeapWord *nextAddr, *lastAddr;
|
|
4477 for (cumNumDirtyCards = numDirtyCards = 0,
|
|
4478 nextAddr = lastAddr = startAddr;
|
|
4479 nextAddr < endAddr;
|
|
4480 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) {
|
|
4481
|
|
4482 ResourceMark rm;
|
|
4483 HandleMark hm;
|
|
4484
|
|
4485 MemRegion dirtyRegion;
|
|
4486 {
|
|
4487 stopTimer();
|
|
4488 CMSTokenSync ts(true);
|
|
4489 startTimer();
|
|
4490 sample_eden();
|
|
4491 // Get dirty region starting at nextOffset (inclusive),
|
|
4492 // simultaneously clearing it.
|
|
4493 dirtyRegion =
|
|
4494 _modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr);
|
|
4495 assert(dirtyRegion.start() >= nextAddr,
|
|
4496 "returned region inconsistent?");
|
|
4497 }
|
|
4498 // Remember where the next search should begin.
|
|
4499 // The returned region (if non-empty) is a right open interval,
|
|
4500 // so lastOffset is obtained from the right end of that
|
|
4501 // interval.
|
|
4502 lastAddr = dirtyRegion.end();
|
|
4503 // Should do something more transparent and less hacky XXX
|
|
4504 numDirtyCards =
|
|
4505 _modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size());
|
|
4506
|
|
4507 // We'll scan the cards in the dirty region (with periodic
|
|
4508 // yields for foreground GC as needed).
|
|
4509 if (!dirtyRegion.is_empty()) {
|
|
4510 assert(numDirtyCards > 0, "consistency check");
|
|
4511 HeapWord* stop_point = NULL;
|
|
4512 {
|
|
4513 stopTimer();
|
|
4514 CMSTokenSyncWithLocks ts(true, gen->freelistLock(),
|
|
4515 bitMapLock());
|
|
4516 startTimer();
|
|
4517 verify_work_stacks_empty();
|
|
4518 verify_overflow_empty();
|
|
4519 sample_eden();
|
|
4520 stop_point =
|
|
4521 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl);
|
|
4522 }
|
|
4523 if (stop_point != NULL) {
|
|
4524 // The careful iteration stopped early either because it found an
|
|
4525 // uninitialized object, or because we were in the midst of an
|
|
4526 // "abortable preclean", which should now be aborted. Redirty
|
|
4527 // the bits corresponding to the partially-scanned or unscanned
|
|
4528 // cards. We'll either restart at the next block boundary or
|
|
4529 // abort the preclean.
|
|
4530 assert((CMSPermGenPrecleaningEnabled && (gen == _permGen)) ||
|
|
4531 (_collectorState == AbortablePreclean && should_abort_preclean()),
|
|
4532 "Unparsable objects should only be in perm gen.");
|
|
4533
|
|
4534 stopTimer();
|
|
4535 CMSTokenSyncWithLocks ts(true, bitMapLock());
|
|
4536 startTimer();
|
|
4537 _modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end()));
|
|
4538 if (should_abort_preclean()) {
|
|
4539 break; // out of preclean loop
|
|
4540 } else {
|
|
4541 // Compute the next address at which preclean should pick up;
|
|
4542 // might need bitMapLock in order to read P-bits.
|
|
4543 lastAddr = next_card_start_after_block(stop_point);
|
|
4544 }
|
|
4545 }
|
|
4546 } else {
|
|
4547 assert(lastAddr == endAddr, "consistency check");
|
|
4548 assert(numDirtyCards == 0, "consistency check");
|
|
4549 break;
|
|
4550 }
|
|
4551 }
|
|
4552 verify_work_stacks_empty();
|
|
4553 verify_overflow_empty();
|
|
4554 return cumNumDirtyCards;
|
|
4555 }
|
|
4556
|
|
4557 // NOTE: preclean_mod_union_table() above and preclean_card_table()
|
|
4558 // below are largely identical; if you need to modify
|
|
4559 // one of these methods, please check the other method too.
|
|
4560
|
|
4561 size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen,
|
|
4562 ScanMarkedObjectsAgainCarefullyClosure* cl) {
|
|
4563 // strategy: it's similar to precleamModUnionTable above, in that
|
|
4564 // we accumulate contiguous ranges of dirty cards, mark these cards
|
|
4565 // precleaned, then scan the region covered by these cards.
|
|
4566 HeapWord* endAddr = (HeapWord*)(gen->_virtual_space.high());
|
|
4567 HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low());
|
|
4568
|
|
4569 cl->setFreelistLock(gen->freelistLock()); // needed for yielding
|
|
4570
|
|
4571 size_t numDirtyCards, cumNumDirtyCards;
|
|
4572 HeapWord *lastAddr, *nextAddr;
|
|
4573
|
|
4574 for (cumNumDirtyCards = numDirtyCards = 0,
|
|
4575 nextAddr = lastAddr = startAddr;
|
|
4576 nextAddr < endAddr;
|
|
4577 nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) {
|
|
4578
|
|
4579 ResourceMark rm;
|
|
4580 HandleMark hm;
|
|
4581
|
|
4582 MemRegion dirtyRegion;
|
|
4583 {
|
|
4584 // See comments in "Precleaning notes" above on why we
|
|
4585 // do this locking. XXX Could the locking overheads be
|
|
4586 // too high when dirty cards are sparse? [I don't think so.]
|
|
4587 stopTimer();
|
|
4588 CMSTokenSync x(true); // is cms thread
|
|
4589 startTimer();
|
|
4590 sample_eden();
|
|
4591 // Get and clear dirty region from card table
|
|
4592 dirtyRegion = _ct->ct_bs()->dirty_card_range_after_preclean(
|
|
4593 MemRegion(nextAddr, endAddr));
|
|
4594 assert(dirtyRegion.start() >= nextAddr,
|
|
4595 "returned region inconsistent?");
|
|
4596 }
|
|
4597 lastAddr = dirtyRegion.end();
|
|
4598 numDirtyCards =
|
|
4599 dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words;
|
|
4600
|
|
4601 if (!dirtyRegion.is_empty()) {
|
|
4602 stopTimer();
|
|
4603 CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock());
|
|
4604 startTimer();
|
|
4605 sample_eden();
|
|
4606 verify_work_stacks_empty();
|
|
4607 verify_overflow_empty();
|
|
4608 HeapWord* stop_point =
|
|
4609 gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl);
|
|
4610 if (stop_point != NULL) {
|
|
4611 // The careful iteration stopped early because it found an
|
|
4612 // uninitialized object. Redirty the bits corresponding to the
|
|
4613 // partially-scanned or unscanned cards, and start again at the
|
|
4614 // next block boundary.
|
|
4615 assert(CMSPermGenPrecleaningEnabled ||
|
|
4616 (_collectorState == AbortablePreclean && should_abort_preclean()),
|
|
4617 "Unparsable objects should only be in perm gen.");
|
|
4618 _ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end()));
|
|
4619 if (should_abort_preclean()) {
|
|
4620 break; // out of preclean loop
|
|
4621 } else {
|
|
4622 // Compute the next address at which preclean should pick up.
|
|
4623 lastAddr = next_card_start_after_block(stop_point);
|
|
4624 }
|
|
4625 }
|
|
4626 } else {
|
|
4627 break;
|
|
4628 }
|
|
4629 }
|
|
4630 verify_work_stacks_empty();
|
|
4631 verify_overflow_empty();
|
|
4632 return cumNumDirtyCards;
|
|
4633 }
|
|
4634
|
|
4635 void CMSCollector::checkpointRootsFinal(bool asynch,
|
|
4636 bool clear_all_soft_refs, bool init_mark_was_synchronous) {
|
|
4637 assert(_collectorState == FinalMarking, "incorrect state transition?");
|
|
4638 check_correct_thread_executing();
|
|
4639 // world is stopped at this checkpoint
|
|
4640 assert(SafepointSynchronize::is_at_safepoint(),
|
|
4641 "world should be stopped");
|
|
4642 verify_work_stacks_empty();
|
|
4643 verify_overflow_empty();
|
|
4644
|
|
4645 SpecializationStats::clear();
|
|
4646 if (PrintGCDetails) {
|
|
4647 gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]",
|
|
4648 _young_gen->used() / K,
|
|
4649 _young_gen->capacity() / K);
|
|
4650 }
|
|
4651 if (asynch) {
|
|
4652 if (CMSScavengeBeforeRemark) {
|
|
4653 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
4654 // Temporarily set flag to false, GCH->do_collection will
|
|
4655 // expect it to be false and set to true
|
|
4656 FlagSetting fl(gch->_is_gc_active, false);
|
|
4657 NOT_PRODUCT(TraceTime t("Scavenge-Before-Remark",
|
|
4658 PrintGCDetails && Verbose, true, gclog_or_tty);)
|
|
4659 int level = _cmsGen->level() - 1;
|
|
4660 if (level >= 0) {
|
|
4661 gch->do_collection(true, // full (i.e. force, see below)
|
|
4662 false, // !clear_all_soft_refs
|
|
4663 0, // size
|
|
4664 false, // is_tlab
|
|
4665 level // max_level
|
|
4666 );
|
|
4667 }
|
|
4668 }
|
|
4669 FreelistLocker x(this);
|
|
4670 MutexLockerEx y(bitMapLock(),
|
|
4671 Mutex::_no_safepoint_check_flag);
|
|
4672 assert(!init_mark_was_synchronous, "but that's impossible!");
|
|
4673 checkpointRootsFinalWork(asynch, clear_all_soft_refs, false);
|
|
4674 } else {
|
|
4675 // already have all the locks
|
|
4676 checkpointRootsFinalWork(asynch, clear_all_soft_refs,
|
|
4677 init_mark_was_synchronous);
|
|
4678 }
|
|
4679 verify_work_stacks_empty();
|
|
4680 verify_overflow_empty();
|
|
4681 SpecializationStats::print();
|
|
4682 }
|
|
4683
|
|
4684 void CMSCollector::checkpointRootsFinalWork(bool asynch,
|
|
4685 bool clear_all_soft_refs, bool init_mark_was_synchronous) {
|
|
4686
|
|
4687 NOT_PRODUCT(TraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, gclog_or_tty);)
|
|
4688
|
|
4689 assert(haveFreelistLocks(), "must have free list locks");
|
|
4690 assert_lock_strong(bitMapLock());
|
|
4691
|
|
4692 if (UseAdaptiveSizePolicy) {
|
|
4693 size_policy()->checkpoint_roots_final_begin();
|
|
4694 }
|
|
4695
|
|
4696 ResourceMark rm;
|
|
4697 HandleMark hm;
|
|
4698
|
|
4699 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
4700
|
|
4701 if (cms_should_unload_classes()) {
|
|
4702 CodeCache::gc_prologue();
|
|
4703 }
|
|
4704 assert(haveFreelistLocks(), "must have free list locks");
|
|
4705 assert_lock_strong(bitMapLock());
|
|
4706
|
|
4707 if (!init_mark_was_synchronous) {
|
|
4708 // We might assume that we need not fill TLAB's when
|
|
4709 // CMSScavengeBeforeRemark is set, because we may have just done
|
|
4710 // a scavenge which would have filled all TLAB's -- and besides
|
|
4711 // Eden would be empty. This however may not always be the case --
|
|
4712 // for instance although we asked for a scavenge, it may not have
|
|
4713 // happened because of a JNI critical section. We probably need
|
|
4714 // a policy for deciding whether we can in that case wait until
|
|
4715 // the critical section releases and then do the remark following
|
|
4716 // the scavenge, and skip it here. In the absence of that policy,
|
|
4717 // or of an indication of whether the scavenge did indeed occur,
|
|
4718 // we cannot rely on TLAB's having been filled and must do
|
|
4719 // so here just in case a scavenge did not happen.
|
|
4720 gch->ensure_parsability(false); // fill TLAB's, but no need to retire them
|
|
4721 // Update the saved marks which may affect the root scans.
|
|
4722 gch->save_marks();
|
|
4723
|
|
4724 {
|
|
4725 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;)
|
|
4726
|
|
4727 // Note on the role of the mod union table:
|
|
4728 // Since the marker in "markFromRoots" marks concurrently with
|
|
4729 // mutators, it is possible for some reachable objects not to have been
|
|
4730 // scanned. For instance, an only reference to an object A was
|
|
4731 // placed in object B after the marker scanned B. Unless B is rescanned,
|
|
4732 // A would be collected. Such updates to references in marked objects
|
|
4733 // are detected via the mod union table which is the set of all cards
|
|
4734 // dirtied since the first checkpoint in this GC cycle and prior to
|
|
4735 // the most recent young generation GC, minus those cleaned up by the
|
|
4736 // concurrent precleaning.
|
|
4737 if (CMSParallelRemarkEnabled && ParallelGCThreads > 0) {
|
|
4738 TraceTime t("Rescan (parallel) ", PrintGCDetails, false, gclog_or_tty);
|
|
4739 do_remark_parallel();
|
|
4740 } else {
|
|
4741 TraceTime t("Rescan (non-parallel) ", PrintGCDetails, false,
|
|
4742 gclog_or_tty);
|
|
4743 do_remark_non_parallel();
|
|
4744 }
|
|
4745 }
|
|
4746 } else {
|
|
4747 assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode");
|
|
4748 // The initial mark was stop-world, so there's no rescanning to
|
|
4749 // do; go straight on to the next step below.
|
|
4750 }
|
|
4751 verify_work_stacks_empty();
|
|
4752 verify_overflow_empty();
|
|
4753
|
|
4754 {
|
|
4755 NOT_PRODUCT(TraceTime ts("refProcessingWork", PrintGCDetails, false, gclog_or_tty);)
|
|
4756 refProcessingWork(asynch, clear_all_soft_refs);
|
|
4757 }
|
|
4758 verify_work_stacks_empty();
|
|
4759 verify_overflow_empty();
|
|
4760
|
|
4761 if (cms_should_unload_classes()) {
|
|
4762 CodeCache::gc_epilogue();
|
|
4763 }
|
|
4764
|
|
4765 // If we encountered any (marking stack / work queue) overflow
|
|
4766 // events during the current CMS cycle, take appropriate
|
|
4767 // remedial measures, where possible, so as to try and avoid
|
|
4768 // recurrence of that condition.
|
|
4769 assert(_markStack.isEmpty(), "No grey objects");
|
|
4770 size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw +
|
|
4771 _ser_kac_ovflw;
|
|
4772 if (ser_ovflw > 0) {
|
|
4773 if (PrintCMSStatistics != 0) {
|
|
4774 gclog_or_tty->print_cr("Marking stack overflow (benign) "
|
|
4775 "(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")",
|
|
4776 _ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw,
|
|
4777 _ser_kac_ovflw);
|
|
4778 }
|
|
4779 _markStack.expand();
|
|
4780 _ser_pmc_remark_ovflw = 0;
|
|
4781 _ser_pmc_preclean_ovflw = 0;
|
|
4782 _ser_kac_ovflw = 0;
|
|
4783 }
|
|
4784 if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) {
|
|
4785 if (PrintCMSStatistics != 0) {
|
|
4786 gclog_or_tty->print_cr("Work queue overflow (benign) "
|
|
4787 "(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")",
|
|
4788 _par_pmc_remark_ovflw, _par_kac_ovflw);
|
|
4789 }
|
|
4790 _par_pmc_remark_ovflw = 0;
|
|
4791 _par_kac_ovflw = 0;
|
|
4792 }
|
|
4793 if (PrintCMSStatistics != 0) {
|
|
4794 if (_markStack._hit_limit > 0) {
|
|
4795 gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")",
|
|
4796 _markStack._hit_limit);
|
|
4797 }
|
|
4798 if (_markStack._failed_double > 0) {
|
|
4799 gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT"),"
|
|
4800 " current capacity "SIZE_FORMAT,
|
|
4801 _markStack._failed_double,
|
|
4802 _markStack.capacity());
|
|
4803 }
|
|
4804 }
|
|
4805 _markStack._hit_limit = 0;
|
|
4806 _markStack._failed_double = 0;
|
|
4807
|
|
4808 if ((VerifyAfterGC || VerifyDuringGC) &&
|
|
4809 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
|
|
4810 verify_after_remark();
|
|
4811 }
|
|
4812
|
|
4813 // Change under the freelistLocks.
|
|
4814 _collectorState = Sweeping;
|
|
4815 // Call isAllClear() under bitMapLock
|
|
4816 assert(_modUnionTable.isAllClear(), "Should be clear by end of the"
|
|
4817 " final marking");
|
|
4818 if (UseAdaptiveSizePolicy) {
|
|
4819 size_policy()->checkpoint_roots_final_end(gch->gc_cause());
|
|
4820 }
|
|
4821 }
|
|
4822
|
|
4823 // Parallel remark task
|
|
4824 class CMSParRemarkTask: public AbstractGangTask {
|
|
4825 CMSCollector* _collector;
|
|
4826 WorkGang* _workers;
|
|
4827 int _n_workers;
|
|
4828 CompactibleFreeListSpace* _cms_space;
|
|
4829 CompactibleFreeListSpace* _perm_space;
|
|
4830
|
|
4831 // The per-thread work queues, available here for stealing.
|
|
4832 OopTaskQueueSet* _task_queues;
|
|
4833 ParallelTaskTerminator _term;
|
|
4834
|
|
4835 public:
|
|
4836 CMSParRemarkTask(CMSCollector* collector,
|
|
4837 CompactibleFreeListSpace* cms_space,
|
|
4838 CompactibleFreeListSpace* perm_space,
|
|
4839 int n_workers, WorkGang* workers,
|
|
4840 OopTaskQueueSet* task_queues):
|
|
4841 AbstractGangTask("Rescan roots and grey objects in parallel"),
|
|
4842 _collector(collector),
|
|
4843 _cms_space(cms_space), _perm_space(perm_space),
|
|
4844 _n_workers(n_workers),
|
|
4845 _workers(workers),
|
|
4846 _task_queues(task_queues),
|
|
4847 _term(workers->total_workers(), task_queues) { }
|
|
4848
|
|
4849 OopTaskQueueSet* task_queues() { return _task_queues; }
|
|
4850
|
|
4851 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); }
|
|
4852
|
|
4853 ParallelTaskTerminator* terminator() { return &_term; }
|
|
4854
|
|
4855 void work(int i);
|
|
4856
|
|
4857 private:
|
|
4858 // Work method in support of parallel rescan ... of young gen spaces
|
|
4859 void do_young_space_rescan(int i, Par_MarkRefsIntoAndScanClosure* cl,
|
|
4860 ContiguousSpace* space,
|
|
4861 HeapWord** chunk_array, size_t chunk_top);
|
|
4862
|
|
4863 // ... of dirty cards in old space
|
|
4864 void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i,
|
|
4865 Par_MarkRefsIntoAndScanClosure* cl);
|
|
4866
|
|
4867 // ... work stealing for the above
|
|
4868 void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed);
|
|
4869 };
|
|
4870
|
|
4871 void CMSParRemarkTask::work(int i) {
|
|
4872 elapsedTimer _timer;
|
|
4873 ResourceMark rm;
|
|
4874 HandleMark hm;
|
|
4875
|
|
4876 // ---------- rescan from roots --------------
|
|
4877 _timer.start();
|
|
4878 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
4879 Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector,
|
|
4880 _collector->_span, _collector->ref_processor(),
|
|
4881 &(_collector->_markBitMap),
|
|
4882 work_queue(i), &(_collector->_revisitStack));
|
|
4883
|
|
4884 // Rescan young gen roots first since these are likely
|
|
4885 // coarsely partitioned and may, on that account, constitute
|
|
4886 // the critical path; thus, it's best to start off that
|
|
4887 // work first.
|
|
4888 // ---------- young gen roots --------------
|
|
4889 {
|
|
4890 DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration();
|
|
4891 EdenSpace* eden_space = dng->eden();
|
|
4892 ContiguousSpace* from_space = dng->from();
|
|
4893 ContiguousSpace* to_space = dng->to();
|
|
4894
|
|
4895 HeapWord** eca = _collector->_eden_chunk_array;
|
|
4896 size_t ect = _collector->_eden_chunk_index;
|
|
4897 HeapWord** sca = _collector->_survivor_chunk_array;
|
|
4898 size_t sct = _collector->_survivor_chunk_index;
|
|
4899
|
|
4900 assert(ect <= _collector->_eden_chunk_capacity, "out of bounds");
|
|
4901 assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds");
|
|
4902
|
|
4903 do_young_space_rescan(i, &par_mrias_cl, to_space, NULL, 0);
|
|
4904 do_young_space_rescan(i, &par_mrias_cl, from_space, sca, sct);
|
|
4905 do_young_space_rescan(i, &par_mrias_cl, eden_space, eca, ect);
|
|
4906
|
|
4907 _timer.stop();
|
|
4908 if (PrintCMSStatistics != 0) {
|
|
4909 gclog_or_tty->print_cr(
|
|
4910 "Finished young gen rescan work in %dth thread: %3.3f sec",
|
|
4911 i, _timer.seconds());
|
|
4912 }
|
|
4913 }
|
|
4914
|
|
4915 // ---------- remaining roots --------------
|
|
4916 _timer.reset();
|
|
4917 _timer.start();
|
|
4918 gch->gen_process_strong_roots(_collector->_cmsGen->level(),
|
|
4919 false, // yg was scanned above
|
|
4920 true, // collecting perm gen
|
|
4921 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()),
|
|
4922 NULL, &par_mrias_cl);
|
|
4923 _timer.stop();
|
|
4924 if (PrintCMSStatistics != 0) {
|
|
4925 gclog_or_tty->print_cr(
|
|
4926 "Finished remaining root rescan work in %dth thread: %3.3f sec",
|
|
4927 i, _timer.seconds());
|
|
4928 }
|
|
4929
|
|
4930 // ---------- rescan dirty cards ------------
|
|
4931 _timer.reset();
|
|
4932 _timer.start();
|
|
4933
|
|
4934 // Do the rescan tasks for each of the two spaces
|
|
4935 // (cms_space and perm_space) in turn.
|
|
4936 do_dirty_card_rescan_tasks(_cms_space, i, &par_mrias_cl);
|
|
4937 do_dirty_card_rescan_tasks(_perm_space, i, &par_mrias_cl);
|
|
4938 _timer.stop();
|
|
4939 if (PrintCMSStatistics != 0) {
|
|
4940 gclog_or_tty->print_cr(
|
|
4941 "Finished dirty card rescan work in %dth thread: %3.3f sec",
|
|
4942 i, _timer.seconds());
|
|
4943 }
|
|
4944
|
|
4945 // ---------- steal work from other threads ...
|
|
4946 // ---------- ... and drain overflow list.
|
|
4947 _timer.reset();
|
|
4948 _timer.start();
|
|
4949 do_work_steal(i, &par_mrias_cl, _collector->hash_seed(i));
|
|
4950 _timer.stop();
|
|
4951 if (PrintCMSStatistics != 0) {
|
|
4952 gclog_or_tty->print_cr(
|
|
4953 "Finished work stealing in %dth thread: %3.3f sec",
|
|
4954 i, _timer.seconds());
|
|
4955 }
|
|
4956 }
|
|
4957
|
|
4958 void
|
|
4959 CMSParRemarkTask::do_young_space_rescan(int i,
|
|
4960 Par_MarkRefsIntoAndScanClosure* cl, ContiguousSpace* space,
|
|
4961 HeapWord** chunk_array, size_t chunk_top) {
|
|
4962 // Until all tasks completed:
|
|
4963 // . claim an unclaimed task
|
|
4964 // . compute region boundaries corresponding to task claimed
|
|
4965 // using chunk_array
|
|
4966 // . par_oop_iterate(cl) over that region
|
|
4967
|
|
4968 ResourceMark rm;
|
|
4969 HandleMark hm;
|
|
4970
|
|
4971 SequentialSubTasksDone* pst = space->par_seq_tasks();
|
|
4972 assert(pst->valid(), "Uninitialized use?");
|
|
4973
|
|
4974 int nth_task = 0;
|
|
4975 int n_tasks = pst->n_tasks();
|
|
4976
|
|
4977 HeapWord *start, *end;
|
|
4978 while (!pst->is_task_claimed(/* reference */ nth_task)) {
|
|
4979 // We claimed task # nth_task; compute its boundaries.
|
|
4980 if (chunk_top == 0) { // no samples were taken
|
|
4981 assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task");
|
|
4982 start = space->bottom();
|
|
4983 end = space->top();
|
|
4984 } else if (nth_task == 0) {
|
|
4985 start = space->bottom();
|
|
4986 end = chunk_array[nth_task];
|
|
4987 } else if (nth_task < (jint)chunk_top) {
|
|
4988 assert(nth_task >= 1, "Control point invariant");
|
|
4989 start = chunk_array[nth_task - 1];
|
|
4990 end = chunk_array[nth_task];
|
|
4991 } else {
|
|
4992 assert(nth_task == (jint)chunk_top, "Control point invariant");
|
|
4993 start = chunk_array[chunk_top - 1];
|
|
4994 end = space->top();
|
|
4995 }
|
|
4996 MemRegion mr(start, end);
|
|
4997 // Verify that mr is in space
|
|
4998 assert(mr.is_empty() || space->used_region().contains(mr),
|
|
4999 "Should be in space");
|
|
5000 // Verify that "start" is an object boundary
|
|
5001 assert(mr.is_empty() || oop(mr.start())->is_oop(),
|
|
5002 "Should be an oop");
|
|
5003 space->par_oop_iterate(mr, cl);
|
|
5004 }
|
|
5005 pst->all_tasks_completed();
|
|
5006 }
|
|
5007
|
|
5008 void
|
|
5009 CMSParRemarkTask::do_dirty_card_rescan_tasks(
|
|
5010 CompactibleFreeListSpace* sp, int i,
|
|
5011 Par_MarkRefsIntoAndScanClosure* cl) {
|
|
5012 // Until all tasks completed:
|
|
5013 // . claim an unclaimed task
|
|
5014 // . compute region boundaries corresponding to task claimed
|
|
5015 // . transfer dirty bits ct->mut for that region
|
|
5016 // . apply rescanclosure to dirty mut bits for that region
|
|
5017
|
|
5018 ResourceMark rm;
|
|
5019 HandleMark hm;
|
|
5020
|
|
5021 OopTaskQueue* work_q = work_queue(i);
|
|
5022 ModUnionClosure modUnionClosure(&(_collector->_modUnionTable));
|
|
5023 // CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION!
|
|
5024 // CAUTION: This closure has state that persists across calls to
|
|
5025 // the work method dirty_range_iterate_clear() in that it has
|
|
5026 // imbedded in it a (subtype of) UpwardsObjectClosure. The
|
|
5027 // use of that state in the imbedded UpwardsObjectClosure instance
|
|
5028 // assumes that the cards are always iterated (even if in parallel
|
|
5029 // by several threads) in monotonically increasing order per each
|
|
5030 // thread. This is true of the implementation below which picks
|
|
5031 // card ranges (chunks) in monotonically increasing order globally
|
|
5032 // and, a-fortiori, in monotonically increasing order per thread
|
|
5033 // (the latter order being a subsequence of the former).
|
|
5034 // If the work code below is ever reorganized into a more chaotic
|
|
5035 // work-partitioning form than the current "sequential tasks"
|
|
5036 // paradigm, the use of that persistent state will have to be
|
|
5037 // revisited and modified appropriately. See also related
|
|
5038 // bug 4756801 work on which should examine this code to make
|
|
5039 // sure that the changes there do not run counter to the
|
|
5040 // assumptions made here and necessary for correctness and
|
|
5041 // efficiency. Note also that this code might yield inefficient
|
|
5042 // behaviour in the case of very large objects that span one or
|
|
5043 // more work chunks. Such objects would potentially be scanned
|
|
5044 // several times redundantly. Work on 4756801 should try and
|
|
5045 // address that performance anomaly if at all possible. XXX
|
|
5046 MemRegion full_span = _collector->_span;
|
|
5047 CMSBitMap* bm = &(_collector->_markBitMap); // shared
|
|
5048 CMSMarkStack* rs = &(_collector->_revisitStack); // shared
|
|
5049 MarkFromDirtyCardsClosure
|
|
5050 greyRescanClosure(_collector, full_span, // entire span of interest
|
|
5051 sp, bm, work_q, rs, cl);
|
|
5052
|
|
5053 SequentialSubTasksDone* pst = sp->conc_par_seq_tasks();
|
|
5054 assert(pst->valid(), "Uninitialized use?");
|
|
5055 int nth_task = 0;
|
|
5056 const int alignment = CardTableModRefBS::card_size * BitsPerWord;
|
|
5057 MemRegion span = sp->used_region();
|
|
5058 HeapWord* start_addr = span.start();
|
|
5059 HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(),
|
|
5060 alignment);
|
|
5061 const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units
|
|
5062 assert((HeapWord*)round_to((intptr_t)start_addr, alignment) ==
|
|
5063 start_addr, "Check alignment");
|
|
5064 assert((size_t)round_to((intptr_t)chunk_size, alignment) ==
|
|
5065 chunk_size, "Check alignment");
|
|
5066
|
|
5067 while (!pst->is_task_claimed(/* reference */ nth_task)) {
|
|
5068 // Having claimed the nth_task, compute corresponding mem-region,
|
|
5069 // which is a-fortiori aligned correctly (i.e. at a MUT bopundary).
|
|
5070 // The alignment restriction ensures that we do not need any
|
|
5071 // synchronization with other gang-workers while setting or
|
|
5072 // clearing bits in thus chunk of the MUT.
|
|
5073 MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size,
|
|
5074 start_addr + (nth_task+1)*chunk_size);
|
|
5075 // The last chunk's end might be way beyond end of the
|
|
5076 // used region. In that case pull back appropriately.
|
|
5077 if (this_span.end() > end_addr) {
|
|
5078 this_span.set_end(end_addr);
|
|
5079 assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)");
|
|
5080 }
|
|
5081 // Iterate over the dirty cards covering this chunk, marking them
|
|
5082 // precleaned, and setting the corresponding bits in the mod union
|
|
5083 // table. Since we have been careful to partition at Card and MUT-word
|
|
5084 // boundaries no synchronization is needed between parallel threads.
|
|
5085 _collector->_ct->ct_bs()->dirty_card_iterate(this_span,
|
|
5086 &modUnionClosure);
|
|
5087
|
|
5088 // Having transferred these marks into the modUnionTable,
|
|
5089 // rescan the marked objects on the dirty cards in the modUnionTable.
|
|
5090 // Even if this is at a synchronous collection, the initial marking
|
|
5091 // may have been done during an asynchronous collection so there
|
|
5092 // may be dirty bits in the mod-union table.
|
|
5093 _collector->_modUnionTable.dirty_range_iterate_clear(
|
|
5094 this_span, &greyRescanClosure);
|
|
5095 _collector->_modUnionTable.verifyNoOneBitsInRange(
|
|
5096 this_span.start(),
|
|
5097 this_span.end());
|
|
5098 }
|
|
5099 pst->all_tasks_completed(); // declare that i am done
|
|
5100 }
|
|
5101
|
|
5102 // . see if we can share work_queues with ParNew? XXX
|
|
5103 void
|
|
5104 CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl,
|
|
5105 int* seed) {
|
|
5106 OopTaskQueue* work_q = work_queue(i);
|
|
5107 NOT_PRODUCT(int num_steals = 0;)
|
|
5108 oop obj_to_scan;
|
|
5109 CMSBitMap* bm = &(_collector->_markBitMap);
|
|
5110 size_t num_from_overflow_list =
|
|
5111 MIN2((size_t)work_q->max_elems()/4,
|
|
5112 (size_t)ParGCDesiredObjsFromOverflowList);
|
|
5113
|
|
5114 while (true) {
|
|
5115 // Completely finish any left over work from (an) earlier round(s)
|
|
5116 cl->trim_queue(0);
|
|
5117 // Now check if there's any work in the overflow list
|
|
5118 if (_collector->par_take_from_overflow_list(num_from_overflow_list,
|
|
5119 work_q)) {
|
|
5120 // found something in global overflow list;
|
|
5121 // not yet ready to go stealing work from others.
|
|
5122 // We'd like to assert(work_q->size() != 0, ...)
|
|
5123 // because we just took work from the overflow list,
|
|
5124 // but of course we can't since all of that could have
|
|
5125 // been already stolen from us.
|
|
5126 // "He giveth and He taketh away."
|
|
5127 continue;
|
|
5128 }
|
|
5129 // Verify that we have no work before we resort to stealing
|
|
5130 assert(work_q->size() == 0, "Have work, shouldn't steal");
|
|
5131 // Try to steal from other queues that have work
|
|
5132 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) {
|
|
5133 NOT_PRODUCT(num_steals++;)
|
|
5134 assert(obj_to_scan->is_oop(), "Oops, not an oop!");
|
|
5135 assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?");
|
|
5136 // Do scanning work
|
|
5137 obj_to_scan->oop_iterate(cl);
|
|
5138 // Loop around, finish this work, and try to steal some more
|
|
5139 } else if (terminator()->offer_termination()) {
|
|
5140 break; // nirvana from the infinite cycle
|
|
5141 }
|
|
5142 }
|
|
5143 NOT_PRODUCT(
|
|
5144 if (PrintCMSStatistics != 0) {
|
|
5145 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals);
|
|
5146 }
|
|
5147 )
|
|
5148 assert(work_q->size() == 0 && _collector->overflow_list_is_empty(),
|
|
5149 "Else our work is not yet done");
|
|
5150 }
|
|
5151
|
|
5152 // Return a thread-local PLAB recording array, as appropriate.
|
|
5153 void* CMSCollector::get_data_recorder(int thr_num) {
|
|
5154 if (_survivor_plab_array != NULL &&
|
|
5155 (CMSPLABRecordAlways ||
|
|
5156 (_collectorState > Marking && _collectorState < FinalMarking))) {
|
|
5157 assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds");
|
|
5158 ChunkArray* ca = &_survivor_plab_array[thr_num];
|
|
5159 ca->reset(); // clear it so that fresh data is recorded
|
|
5160 return (void*) ca;
|
|
5161 } else {
|
|
5162 return NULL;
|
|
5163 }
|
|
5164 }
|
|
5165
|
|
5166 // Reset all the thread-local PLAB recording arrays
|
|
5167 void CMSCollector::reset_survivor_plab_arrays() {
|
|
5168 for (uint i = 0; i < ParallelGCThreads; i++) {
|
|
5169 _survivor_plab_array[i].reset();
|
|
5170 }
|
|
5171 }
|
|
5172
|
|
5173 // Merge the per-thread plab arrays into the global survivor chunk
|
|
5174 // array which will provide the partitioning of the survivor space
|
|
5175 // for CMS rescan.
|
|
5176 void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv) {
|
|
5177 assert(_survivor_plab_array != NULL, "Error");
|
|
5178 assert(_survivor_chunk_array != NULL, "Error");
|
|
5179 assert(_collectorState == FinalMarking, "Error");
|
|
5180 for (uint j = 0; j < ParallelGCThreads; j++) {
|
|
5181 _cursor[j] = 0;
|
|
5182 }
|
|
5183 HeapWord* top = surv->top();
|
|
5184 size_t i;
|
|
5185 for (i = 0; i < _survivor_chunk_capacity; i++) { // all sca entries
|
|
5186 HeapWord* min_val = top; // Higher than any PLAB address
|
|
5187 uint min_tid = 0; // position of min_val this round
|
|
5188 for (uint j = 0; j < ParallelGCThreads; j++) {
|
|
5189 ChunkArray* cur_sca = &_survivor_plab_array[j];
|
|
5190 if (_cursor[j] == cur_sca->end()) {
|
|
5191 continue;
|
|
5192 }
|
|
5193 assert(_cursor[j] < cur_sca->end(), "ctl pt invariant");
|
|
5194 HeapWord* cur_val = cur_sca->nth(_cursor[j]);
|
|
5195 assert(surv->used_region().contains(cur_val), "Out of bounds value");
|
|
5196 if (cur_val < min_val) {
|
|
5197 min_tid = j;
|
|
5198 min_val = cur_val;
|
|
5199 } else {
|
|
5200 assert(cur_val < top, "All recorded addresses should be less");
|
|
5201 }
|
|
5202 }
|
|
5203 // At this point min_val and min_tid are respectively
|
|
5204 // the least address in _survivor_plab_array[j]->nth(_cursor[j])
|
|
5205 // and the thread (j) that witnesses that address.
|
|
5206 // We record this address in the _survivor_chunk_array[i]
|
|
5207 // and increment _cursor[min_tid] prior to the next round i.
|
|
5208 if (min_val == top) {
|
|
5209 break;
|
|
5210 }
|
|
5211 _survivor_chunk_array[i] = min_val;
|
|
5212 _cursor[min_tid]++;
|
|
5213 }
|
|
5214 // We are all done; record the size of the _survivor_chunk_array
|
|
5215 _survivor_chunk_index = i; // exclusive: [0, i)
|
|
5216 if (PrintCMSStatistics > 0) {
|
|
5217 gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i);
|
|
5218 }
|
|
5219 // Verify that we used up all the recorded entries
|
|
5220 #ifdef ASSERT
|
|
5221 size_t total = 0;
|
|
5222 for (uint j = 0; j < ParallelGCThreads; j++) {
|
|
5223 assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant");
|
|
5224 total += _cursor[j];
|
|
5225 }
|
|
5226 assert(total == _survivor_chunk_index, "Ctl Pt Invariant");
|
|
5227 // Check that the merged array is in sorted order
|
|
5228 if (total > 0) {
|
|
5229 for (size_t i = 0; i < total - 1; i++) {
|
|
5230 if (PrintCMSStatistics > 0) {
|
|
5231 gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ",
|
|
5232 i, _survivor_chunk_array[i]);
|
|
5233 }
|
|
5234 assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1],
|
|
5235 "Not sorted");
|
|
5236 }
|
|
5237 }
|
|
5238 #endif // ASSERT
|
|
5239 }
|
|
5240
|
|
5241 // Set up the space's par_seq_tasks structure for work claiming
|
|
5242 // for parallel rescan of young gen.
|
|
5243 // See ParRescanTask where this is currently used.
|
|
5244 void
|
|
5245 CMSCollector::
|
|
5246 initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) {
|
|
5247 assert(n_threads > 0, "Unexpected n_threads argument");
|
|
5248 DefNewGeneration* dng = (DefNewGeneration*)_young_gen;
|
|
5249
|
|
5250 // Eden space
|
|
5251 {
|
|
5252 SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks();
|
|
5253 assert(!pst->valid(), "Clobbering existing data?");
|
|
5254 // Each valid entry in [0, _eden_chunk_index) represents a task.
|
|
5255 size_t n_tasks = _eden_chunk_index + 1;
|
|
5256 assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error");
|
|
5257 pst->set_par_threads(n_threads);
|
|
5258 pst->set_n_tasks((int)n_tasks);
|
|
5259 }
|
|
5260
|
|
5261 // Merge the survivor plab arrays into _survivor_chunk_array
|
|
5262 if (_survivor_plab_array != NULL) {
|
|
5263 merge_survivor_plab_arrays(dng->from());
|
|
5264 } else {
|
|
5265 assert(_survivor_chunk_index == 0, "Error");
|
|
5266 }
|
|
5267
|
|
5268 // To space
|
|
5269 {
|
|
5270 SequentialSubTasksDone* pst = dng->to()->par_seq_tasks();
|
|
5271 assert(!pst->valid(), "Clobbering existing data?");
|
|
5272 pst->set_par_threads(n_threads);
|
|
5273 pst->set_n_tasks(1);
|
|
5274 assert(pst->valid(), "Error");
|
|
5275 }
|
|
5276
|
|
5277 // From space
|
|
5278 {
|
|
5279 SequentialSubTasksDone* pst = dng->from()->par_seq_tasks();
|
|
5280 assert(!pst->valid(), "Clobbering existing data?");
|
|
5281 size_t n_tasks = _survivor_chunk_index + 1;
|
|
5282 assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error");
|
|
5283 pst->set_par_threads(n_threads);
|
|
5284 pst->set_n_tasks((int)n_tasks);
|
|
5285 assert(pst->valid(), "Error");
|
|
5286 }
|
|
5287 }
|
|
5288
|
|
5289 // Parallel version of remark
|
|
5290 void CMSCollector::do_remark_parallel() {
|
|
5291 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
5292 WorkGang* workers = gch->workers();
|
|
5293 assert(workers != NULL, "Need parallel worker threads.");
|
|
5294 int n_workers = workers->total_workers();
|
|
5295 CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace();
|
|
5296 CompactibleFreeListSpace* perm_space = _permGen->cmsSpace();
|
|
5297
|
|
5298 CMSParRemarkTask tsk(this,
|
|
5299 cms_space, perm_space,
|
|
5300 n_workers, workers, task_queues());
|
|
5301
|
|
5302 // Set up for parallel process_strong_roots work.
|
|
5303 gch->set_par_threads(n_workers);
|
|
5304 gch->change_strong_roots_parity();
|
|
5305 // We won't be iterating over the cards in the card table updating
|
|
5306 // the younger_gen cards, so we shouldn't call the following else
|
|
5307 // the verification code as well as subsequent younger_refs_iterate
|
|
5308 // code would get confused. XXX
|
|
5309 // gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel
|
|
5310
|
|
5311 // The young gen rescan work will not be done as part of
|
|
5312 // process_strong_roots (which currently doesn't knw how to
|
|
5313 // parallelize such a scan), but rather will be broken up into
|
|
5314 // a set of parallel tasks (via the sampling that the [abortable]
|
|
5315 // preclean phase did of EdenSpace, plus the [two] tasks of
|
|
5316 // scanning the [two] survivor spaces. Further fine-grain
|
|
5317 // parallelization of the scanning of the survivor spaces
|
|
5318 // themselves, and of precleaning of the younger gen itself
|
|
5319 // is deferred to the future.
|
|
5320 initialize_sequential_subtasks_for_young_gen_rescan(n_workers);
|
|
5321
|
|
5322 // The dirty card rescan work is broken up into a "sequence"
|
|
5323 // of parallel tasks (per constituent space) that are dynamically
|
|
5324 // claimed by the parallel threads.
|
|
5325 cms_space->initialize_sequential_subtasks_for_rescan(n_workers);
|
|
5326 perm_space->initialize_sequential_subtasks_for_rescan(n_workers);
|
|
5327
|
|
5328 // It turns out that even when we're using 1 thread, doing the work in a
|
|
5329 // separate thread causes wide variance in run times. We can't help this
|
|
5330 // in the multi-threaded case, but we special-case n=1 here to get
|
|
5331 // repeatable measurements of the 1-thread overhead of the parallel code.
|
|
5332 if (n_workers > 1) {
|
|
5333 // Make refs discovery MT-safe
|
|
5334 ReferenceProcessorMTMutator mt(ref_processor(), true);
|
|
5335 workers->run_task(&tsk);
|
|
5336 } else {
|
|
5337 tsk.work(0);
|
|
5338 }
|
|
5339 gch->set_par_threads(0); // 0 ==> non-parallel.
|
|
5340 // restore, single-threaded for now, any preserved marks
|
|
5341 // as a result of work_q overflow
|
|
5342 restore_preserved_marks_if_any();
|
|
5343 }
|
|
5344
|
|
5345 // Non-parallel version of remark
|
|
5346 void CMSCollector::do_remark_non_parallel() {
|
|
5347 ResourceMark rm;
|
|
5348 HandleMark hm;
|
|
5349 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
5350 MarkRefsIntoAndScanClosure
|
|
5351 mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable,
|
|
5352 &_markStack, &_revisitStack, this,
|
|
5353 false /* should_yield */, false /* not precleaning */);
|
|
5354 MarkFromDirtyCardsClosure
|
|
5355 markFromDirtyCardsClosure(this, _span,
|
|
5356 NULL, // space is set further below
|
|
5357 &_markBitMap, &_markStack, &_revisitStack,
|
|
5358 &mrias_cl);
|
|
5359 {
|
|
5360 TraceTime t("grey object rescan", PrintGCDetails, false, gclog_or_tty);
|
|
5361 // Iterate over the dirty cards, marking them precleaned, and
|
|
5362 // setting the corresponding bits in the mod union table.
|
|
5363 {
|
|
5364 ModUnionClosure modUnionClosure(&_modUnionTable);
|
|
5365 _ct->ct_bs()->dirty_card_iterate(
|
|
5366 _cmsGen->used_region(),
|
|
5367 &modUnionClosure);
|
|
5368 _ct->ct_bs()->dirty_card_iterate(
|
|
5369 _permGen->used_region(),
|
|
5370 &modUnionClosure);
|
|
5371 }
|
|
5372 // Having transferred these marks into the modUnionTable, we just need
|
|
5373 // to rescan the marked objects on the dirty cards in the modUnionTable.
|
|
5374 // The initial marking may have been done during an asynchronous
|
|
5375 // collection so there may be dirty bits in the mod-union table.
|
|
5376 const int alignment =
|
|
5377 CardTableModRefBS::card_size * BitsPerWord;
|
|
5378 {
|
|
5379 // ... First handle dirty cards in CMS gen
|
|
5380 markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace());
|
|
5381 MemRegion ur = _cmsGen->used_region();
|
|
5382 HeapWord* lb = ur.start();
|
|
5383 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment);
|
|
5384 MemRegion cms_span(lb, ub);
|
|
5385 _modUnionTable.dirty_range_iterate_clear(cms_span,
|
|
5386 &markFromDirtyCardsClosure);
|
|
5387 verify_work_stacks_empty();
|
|
5388 if (PrintCMSStatistics != 0) {
|
|
5389 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ",
|
|
5390 markFromDirtyCardsClosure.num_dirty_cards());
|
|
5391 }
|
|
5392 }
|
|
5393 {
|
|
5394 // .. and then repeat for dirty cards in perm gen
|
|
5395 markFromDirtyCardsClosure.set_space(_permGen->cmsSpace());
|
|
5396 MemRegion ur = _permGen->used_region();
|
|
5397 HeapWord* lb = ur.start();
|
|
5398 HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment);
|
|
5399 MemRegion perm_span(lb, ub);
|
|
5400 _modUnionTable.dirty_range_iterate_clear(perm_span,
|
|
5401 &markFromDirtyCardsClosure);
|
|
5402 verify_work_stacks_empty();
|
|
5403 if (PrintCMSStatistics != 0) {
|
|
5404 gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in perm gen) ",
|
|
5405 markFromDirtyCardsClosure.num_dirty_cards());
|
|
5406 }
|
|
5407 }
|
|
5408 }
|
|
5409 if (VerifyDuringGC &&
|
|
5410 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
|
|
5411 HandleMark hm; // Discard invalid handles created during verification
|
|
5412 Universe::verify(true);
|
|
5413 }
|
|
5414 {
|
|
5415 TraceTime t("root rescan", PrintGCDetails, false, gclog_or_tty);
|
|
5416
|
|
5417 verify_work_stacks_empty();
|
|
5418
|
|
5419 gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel.
|
|
5420 gch->gen_process_strong_roots(_cmsGen->level(),
|
|
5421 true, // younger gens as roots
|
|
5422 true, // collecting perm gen
|
|
5423 SharedHeap::ScanningOption(roots_scanning_options()),
|
|
5424 NULL, &mrias_cl);
|
|
5425 }
|
|
5426 verify_work_stacks_empty();
|
|
5427 // Restore evacuated mark words, if any, used for overflow list links
|
|
5428 if (!CMSOverflowEarlyRestoration) {
|
|
5429 restore_preserved_marks_if_any();
|
|
5430 }
|
|
5431 verify_overflow_empty();
|
|
5432 }
|
|
5433
|
|
5434 ////////////////////////////////////////////////////////
|
|
5435 // Parallel Reference Processing Task Proxy Class
|
|
5436 ////////////////////////////////////////////////////////
|
|
5437 class CMSRefProcTaskProxy: public AbstractGangTask {
|
|
5438 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
|
|
5439 CMSCollector* _collector;
|
|
5440 CMSBitMap* _mark_bit_map;
|
|
5441 MemRegion _span;
|
|
5442 OopTaskQueueSet* _task_queues;
|
|
5443 ParallelTaskTerminator _term;
|
|
5444 ProcessTask& _task;
|
|
5445
|
|
5446 public:
|
|
5447 CMSRefProcTaskProxy(ProcessTask& task,
|
|
5448 CMSCollector* collector,
|
|
5449 const MemRegion& span,
|
|
5450 CMSBitMap* mark_bit_map,
|
|
5451 int total_workers,
|
|
5452 OopTaskQueueSet* task_queues):
|
|
5453 AbstractGangTask("Process referents by policy in parallel"),
|
|
5454 _task(task),
|
|
5455 _collector(collector), _span(span), _mark_bit_map(mark_bit_map),
|
|
5456 _task_queues(task_queues),
|
|
5457 _term(total_workers, task_queues)
|
|
5458 { }
|
|
5459
|
|
5460 OopTaskQueueSet* task_queues() { return _task_queues; }
|
|
5461
|
|
5462 OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); }
|
|
5463
|
|
5464 ParallelTaskTerminator* terminator() { return &_term; }
|
|
5465
|
|
5466 void do_work_steal(int i,
|
|
5467 CMSParDrainMarkingStackClosure* drain,
|
|
5468 CMSParKeepAliveClosure* keep_alive,
|
|
5469 int* seed);
|
|
5470
|
|
5471 virtual void work(int i);
|
|
5472 };
|
|
5473
|
|
5474 void CMSRefProcTaskProxy::work(int i) {
|
|
5475 CMSParKeepAliveClosure par_keep_alive(_collector, _span,
|
|
5476 _mark_bit_map, work_queue(i));
|
|
5477 CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span,
|
|
5478 _mark_bit_map, work_queue(i));
|
|
5479 CMSIsAliveClosure is_alive_closure(_mark_bit_map);
|
|
5480 _task.work(i, is_alive_closure, par_keep_alive, par_drain_stack);
|
|
5481 if (_task.marks_oops_alive()) {
|
|
5482 do_work_steal(i, &par_drain_stack, &par_keep_alive,
|
|
5483 _collector->hash_seed(i));
|
|
5484 }
|
|
5485 assert(work_queue(i)->size() == 0, "work_queue should be empty");
|
|
5486 assert(_collector->_overflow_list == NULL, "non-empty _overflow_list");
|
|
5487 }
|
|
5488
|
|
5489 class CMSRefEnqueueTaskProxy: public AbstractGangTask {
|
|
5490 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
|
|
5491 EnqueueTask& _task;
|
|
5492
|
|
5493 public:
|
|
5494 CMSRefEnqueueTaskProxy(EnqueueTask& task)
|
|
5495 : AbstractGangTask("Enqueue reference objects in parallel"),
|
|
5496 _task(task)
|
|
5497 { }
|
|
5498
|
|
5499 virtual void work(int i)
|
|
5500 {
|
|
5501 _task.work(i);
|
|
5502 }
|
|
5503 };
|
|
5504
|
|
5505 CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector,
|
|
5506 MemRegion span, CMSBitMap* bit_map, OopTaskQueue* work_queue):
|
|
5507 _collector(collector),
|
|
5508 _span(span),
|
|
5509 _bit_map(bit_map),
|
|
5510 _work_queue(work_queue),
|
|
5511 _mark_and_push(collector, span, bit_map, work_queue),
|
|
5512 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4),
|
|
5513 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads)))
|
|
5514 { }
|
|
5515
|
|
5516 // . see if we can share work_queues with ParNew? XXX
|
|
5517 void CMSRefProcTaskProxy::do_work_steal(int i,
|
|
5518 CMSParDrainMarkingStackClosure* drain,
|
|
5519 CMSParKeepAliveClosure* keep_alive,
|
|
5520 int* seed) {
|
|
5521 OopTaskQueue* work_q = work_queue(i);
|
|
5522 NOT_PRODUCT(int num_steals = 0;)
|
|
5523 oop obj_to_scan;
|
|
5524 size_t num_from_overflow_list =
|
|
5525 MIN2((size_t)work_q->max_elems()/4,
|
|
5526 (size_t)ParGCDesiredObjsFromOverflowList);
|
|
5527
|
|
5528 while (true) {
|
|
5529 // Completely finish any left over work from (an) earlier round(s)
|
|
5530 drain->trim_queue(0);
|
|
5531 // Now check if there's any work in the overflow list
|
|
5532 if (_collector->par_take_from_overflow_list(num_from_overflow_list,
|
|
5533 work_q)) {
|
|
5534 // Found something in global overflow list;
|
|
5535 // not yet ready to go stealing work from others.
|
|
5536 // We'd like to assert(work_q->size() != 0, ...)
|
|
5537 // because we just took work from the overflow list,
|
|
5538 // but of course we can't, since all of that might have
|
|
5539 // been already stolen from us.
|
|
5540 continue;
|
|
5541 }
|
|
5542 // Verify that we have no work before we resort to stealing
|
|
5543 assert(work_q->size() == 0, "Have work, shouldn't steal");
|
|
5544 // Try to steal from other queues that have work
|
|
5545 if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) {
|
|
5546 NOT_PRODUCT(num_steals++;)
|
|
5547 assert(obj_to_scan->is_oop(), "Oops, not an oop!");
|
|
5548 assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?");
|
|
5549 // Do scanning work
|
|
5550 obj_to_scan->oop_iterate(keep_alive);
|
|
5551 // Loop around, finish this work, and try to steal some more
|
|
5552 } else if (terminator()->offer_termination()) {
|
|
5553 break; // nirvana from the infinite cycle
|
|
5554 }
|
|
5555 }
|
|
5556 NOT_PRODUCT(
|
|
5557 if (PrintCMSStatistics != 0) {
|
|
5558 gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals);
|
|
5559 }
|
|
5560 )
|
|
5561 }
|
|
5562
|
|
5563 void CMSRefProcTaskExecutor::execute(ProcessTask& task)
|
|
5564 {
|
|
5565 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
5566 WorkGang* workers = gch->workers();
|
|
5567 assert(workers != NULL, "Need parallel worker threads.");
|
|
5568 int n_workers = workers->total_workers();
|
|
5569 CMSRefProcTaskProxy rp_task(task, &_collector,
|
|
5570 _collector.ref_processor()->span(),
|
|
5571 _collector.markBitMap(),
|
|
5572 n_workers, _collector.task_queues());
|
|
5573 workers->run_task(&rp_task);
|
|
5574 }
|
|
5575
|
|
5576 void CMSRefProcTaskExecutor::execute(EnqueueTask& task)
|
|
5577 {
|
|
5578
|
|
5579 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
5580 WorkGang* workers = gch->workers();
|
|
5581 assert(workers != NULL, "Need parallel worker threads.");
|
|
5582 CMSRefEnqueueTaskProxy enq_task(task);
|
|
5583 workers->run_task(&enq_task);
|
|
5584 }
|
|
5585
|
|
5586 void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) {
|
|
5587
|
|
5588 ResourceMark rm;
|
|
5589 HandleMark hm;
|
|
5590 ReferencePolicy* soft_ref_policy;
|
|
5591
|
|
5592 assert(!ref_processor()->enqueuing_is_done(), "Enqueuing should not be complete");
|
|
5593 // Process weak references.
|
|
5594 if (clear_all_soft_refs) {
|
|
5595 soft_ref_policy = new AlwaysClearPolicy();
|
|
5596 } else {
|
|
5597 #ifdef COMPILER2
|
|
5598 soft_ref_policy = new LRUMaxHeapPolicy();
|
|
5599 #else
|
|
5600 soft_ref_policy = new LRUCurrentHeapPolicy();
|
|
5601 #endif // COMPILER2
|
|
5602 }
|
|
5603 verify_work_stacks_empty();
|
|
5604
|
|
5605 ReferenceProcessor* rp = ref_processor();
|
|
5606 assert(rp->span().equals(_span), "Spans should be equal");
|
|
5607 CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap,
|
|
5608 &_markStack);
|
|
5609 CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this,
|
|
5610 _span, &_markBitMap, &_markStack,
|
|
5611 &cmsKeepAliveClosure);
|
|
5612 {
|
|
5613 TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty);
|
|
5614 if (rp->processing_is_mt()) {
|
|
5615 CMSRefProcTaskExecutor task_executor(*this);
|
|
5616 rp->process_discovered_references(soft_ref_policy,
|
|
5617 &_is_alive_closure,
|
|
5618 &cmsKeepAliveClosure,
|
|
5619 &cmsDrainMarkingStackClosure,
|
|
5620 &task_executor);
|
|
5621 } else {
|
|
5622 rp->process_discovered_references(soft_ref_policy,
|
|
5623 &_is_alive_closure,
|
|
5624 &cmsKeepAliveClosure,
|
|
5625 &cmsDrainMarkingStackClosure,
|
|
5626 NULL);
|
|
5627 }
|
|
5628 verify_work_stacks_empty();
|
|
5629 }
|
|
5630
|
|
5631 if (cms_should_unload_classes()) {
|
|
5632 {
|
|
5633 TraceTime t("class unloading", PrintGCDetails, false, gclog_or_tty);
|
|
5634
|
|
5635 // Follow SystemDictionary roots and unload classes
|
|
5636 bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure);
|
|
5637
|
|
5638 // Follow CodeCache roots and unload any methods marked for unloading
|
|
5639 CodeCache::do_unloading(&_is_alive_closure,
|
|
5640 &cmsKeepAliveClosure,
|
|
5641 purged_class);
|
|
5642
|
|
5643 cmsDrainMarkingStackClosure.do_void();
|
|
5644 verify_work_stacks_empty();
|
|
5645
|
|
5646 // Update subklass/sibling/implementor links in KlassKlass descendants
|
|
5647 assert(!_revisitStack.isEmpty(), "revisit stack should not be empty");
|
|
5648 oop k;
|
|
5649 while ((k = _revisitStack.pop()) != NULL) {
|
|
5650 ((Klass*)(oopDesc*)k)->follow_weak_klass_links(
|
|
5651 &_is_alive_closure,
|
|
5652 &cmsKeepAliveClosure);
|
|
5653 }
|
|
5654 assert(!ClassUnloading ||
|
|
5655 (_markStack.isEmpty() && overflow_list_is_empty()),
|
|
5656 "Should not have found new reachable objects");
|
|
5657 assert(_revisitStack.isEmpty(), "revisit stack should have been drained");
|
|
5658 cmsDrainMarkingStackClosure.do_void();
|
|
5659 verify_work_stacks_empty();
|
|
5660 }
|
|
5661
|
|
5662 {
|
|
5663 TraceTime t("scrub symbol & string tables", PrintGCDetails, false, gclog_or_tty);
|
|
5664 // Now clean up stale oops in SymbolTable and StringTable
|
|
5665 SymbolTable::unlink(&_is_alive_closure);
|
|
5666 StringTable::unlink(&_is_alive_closure);
|
|
5667 }
|
|
5668 }
|
|
5669
|
|
5670 verify_work_stacks_empty();
|
|
5671 // Restore any preserved marks as a result of mark stack or
|
|
5672 // work queue overflow
|
|
5673 restore_preserved_marks_if_any(); // done single-threaded for now
|
|
5674
|
|
5675 rp->set_enqueuing_is_done(true);
|
|
5676 if (rp->processing_is_mt()) {
|
|
5677 CMSRefProcTaskExecutor task_executor(*this);
|
|
5678 rp->enqueue_discovered_references(&task_executor);
|
|
5679 } else {
|
|
5680 rp->enqueue_discovered_references(NULL);
|
|
5681 }
|
|
5682 rp->verify_no_references_recorded();
|
|
5683 assert(!rp->discovery_enabled(), "should have been disabled");
|
|
5684
|
|
5685 // JVMTI object tagging is based on JNI weak refs. If any of these
|
|
5686 // refs were cleared then JVMTI needs to update its maps and
|
|
5687 // maybe post ObjectFrees to agents.
|
|
5688 JvmtiExport::cms_ref_processing_epilogue();
|
|
5689 }
|
|
5690
|
|
5691 #ifndef PRODUCT
|
|
5692 void CMSCollector::check_correct_thread_executing() {
|
|
5693 Thread* t = Thread::current();
|
|
5694 // Only the VM thread or the CMS thread should be here.
|
|
5695 assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(),
|
|
5696 "Unexpected thread type");
|
|
5697 // If this is the vm thread, the foreground process
|
|
5698 // should not be waiting. Note that _foregroundGCIsActive is
|
|
5699 // true while the foreground collector is waiting.
|
|
5700 if (_foregroundGCShouldWait) {
|
|
5701 // We cannot be the VM thread
|
|
5702 assert(t->is_ConcurrentGC_thread(),
|
|
5703 "Should be CMS thread");
|
|
5704 } else {
|
|
5705 // We can be the CMS thread only if we are in a stop-world
|
|
5706 // phase of CMS collection.
|
|
5707 if (t->is_ConcurrentGC_thread()) {
|
|
5708 assert(_collectorState == InitialMarking ||
|
|
5709 _collectorState == FinalMarking,
|
|
5710 "Should be a stop-world phase");
|
|
5711 // The CMS thread should be holding the CMS_token.
|
|
5712 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
5713 "Potential interference with concurrently "
|
|
5714 "executing VM thread");
|
|
5715 }
|
|
5716 }
|
|
5717 }
|
|
5718 #endif
|
|
5719
|
|
5720 void CMSCollector::sweep(bool asynch) {
|
|
5721 assert(_collectorState == Sweeping, "just checking");
|
|
5722 check_correct_thread_executing();
|
|
5723 verify_work_stacks_empty();
|
|
5724 verify_overflow_empty();
|
|
5725 incrementSweepCount();
|
|
5726 _sweep_timer.stop();
|
|
5727 _sweep_estimate.sample(_sweep_timer.seconds());
|
|
5728 size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free());
|
|
5729
|
|
5730 // PermGen verification support: If perm gen sweeping is disabled in
|
|
5731 // this cycle, we preserve the perm gen object "deadness" information
|
|
5732 // in the perm_gen_verify_bit_map. In order to do that we traverse
|
|
5733 // all blocks in perm gen and mark all dead objects.
|
|
5734 if (verifying() && !cms_should_unload_classes()) {
|
|
5735 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(),
|
|
5736 bitMapLock());
|
|
5737 assert(perm_gen_verify_bit_map()->sizeInBits() != 0,
|
|
5738 "Should have already been allocated");
|
|
5739 MarkDeadObjectsClosure mdo(this, _permGen->cmsSpace(),
|
|
5740 markBitMap(), perm_gen_verify_bit_map());
|
|
5741 _permGen->cmsSpace()->blk_iterate(&mdo);
|
|
5742 }
|
|
5743
|
|
5744 if (asynch) {
|
|
5745 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
|
|
5746 CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails);
|
|
5747 // First sweep the old gen then the perm gen
|
|
5748 {
|
|
5749 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(),
|
|
5750 bitMapLock());
|
|
5751 sweepWork(_cmsGen, asynch);
|
|
5752 }
|
|
5753
|
|
5754 // Now repeat for perm gen
|
|
5755 if (cms_should_unload_classes()) {
|
|
5756 CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(),
|
|
5757 bitMapLock());
|
|
5758 sweepWork(_permGen, asynch);
|
|
5759 }
|
|
5760
|
|
5761 // Update Universe::_heap_*_at_gc figures.
|
|
5762 // We need all the free list locks to make the abstract state
|
|
5763 // transition from Sweeping to Resetting. See detailed note
|
|
5764 // further below.
|
|
5765 {
|
|
5766 CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(),
|
|
5767 _permGen->freelistLock());
|
|
5768 // Update heap occupancy information which is used as
|
|
5769 // input to soft ref clearing policy at the next gc.
|
|
5770 Universe::update_heap_info_at_gc();
|
|
5771 _collectorState = Resizing;
|
|
5772 }
|
|
5773 } else {
|
|
5774 // already have needed locks
|
|
5775 sweepWork(_cmsGen, asynch);
|
|
5776
|
|
5777 if (cms_should_unload_classes()) {
|
|
5778 sweepWork(_permGen, asynch);
|
|
5779 }
|
|
5780 // Update heap occupancy information which is used as
|
|
5781 // input to soft ref clearing policy at the next gc.
|
|
5782 Universe::update_heap_info_at_gc();
|
|
5783 _collectorState = Resizing;
|
|
5784 }
|
|
5785 verify_work_stacks_empty();
|
|
5786 verify_overflow_empty();
|
|
5787
|
|
5788 _sweep_timer.reset();
|
|
5789 _sweep_timer.start();
|
|
5790
|
|
5791 update_time_of_last_gc(os::javaTimeMillis());
|
|
5792
|
|
5793 // NOTE on abstract state transitions:
|
|
5794 // Mutators allocate-live and/or mark the mod-union table dirty
|
|
5795 // based on the state of the collection. The former is done in
|
|
5796 // the interval [Marking, Sweeping] and the latter in the interval
|
|
5797 // [Marking, Sweeping). Thus the transitions into the Marking state
|
|
5798 // and out of the Sweeping state must be synchronously visible
|
|
5799 // globally to the mutators.
|
|
5800 // The transition into the Marking state happens with the world
|
|
5801 // stopped so the mutators will globally see it. Sweeping is
|
|
5802 // done asynchronously by the background collector so the transition
|
|
5803 // from the Sweeping state to the Resizing state must be done
|
|
5804 // under the freelistLock (as is the check for whether to
|
|
5805 // allocate-live and whether to dirty the mod-union table).
|
|
5806 assert(_collectorState == Resizing, "Change of collector state to"
|
|
5807 " Resizing must be done under the freelistLocks (plural)");
|
|
5808
|
|
5809 // Now that sweeping has been completed, if the GCH's
|
|
5810 // incremental_collection_will_fail flag is set, clear it,
|
|
5811 // thus inviting a younger gen collection to promote into
|
|
5812 // this generation. If such a promotion may still fail,
|
|
5813 // the flag will be set again when a young collection is
|
|
5814 // attempted.
|
|
5815 // I think the incremental_collection_will_fail flag's use
|
|
5816 // is specific to a 2 generation collection policy, so i'll
|
|
5817 // assert that that's the configuration we are operating within.
|
|
5818 // The use of the flag can and should be generalized appropriately
|
|
5819 // in the future to deal with a general n-generation system.
|
|
5820
|
|
5821 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
5822 assert(gch->collector_policy()->is_two_generation_policy(),
|
|
5823 "Resetting of incremental_collection_will_fail flag"
|
|
5824 " may be incorrect otherwise");
|
|
5825 gch->clear_incremental_collection_will_fail();
|
|
5826 gch->update_full_collections_completed(_collection_count_start);
|
|
5827 }
|
|
5828
|
|
5829 // FIX ME!!! Looks like this belongs in CFLSpace, with
|
|
5830 // CMSGen merely delegating to it.
|
|
5831 void ConcurrentMarkSweepGeneration::setNearLargestChunk() {
|
|
5832 double nearLargestPercent = 0.999;
|
|
5833 HeapWord* minAddr = _cmsSpace->bottom();
|
|
5834 HeapWord* largestAddr =
|
|
5835 (HeapWord*) _cmsSpace->dictionary()->findLargestDict();
|
|
5836 if (largestAddr == 0) {
|
|
5837 // The dictionary appears to be empty. In this case
|
|
5838 // try to coalesce at the end of the heap.
|
|
5839 largestAddr = _cmsSpace->end();
|
|
5840 }
|
|
5841 size_t largestOffset = pointer_delta(largestAddr, minAddr);
|
|
5842 size_t nearLargestOffset =
|
|
5843 (size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize;
|
|
5844 _cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset);
|
|
5845 }
|
|
5846
|
|
5847 bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) {
|
|
5848 return addr >= _cmsSpace->nearLargestChunk();
|
|
5849 }
|
|
5850
|
|
5851 FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() {
|
|
5852 return _cmsSpace->find_chunk_at_end();
|
|
5853 }
|
|
5854
|
|
5855 void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level,
|
|
5856 bool full) {
|
|
5857 // The next lower level has been collected. Gather any statistics
|
|
5858 // that are of interest at this point.
|
|
5859 if (!full && (current_level + 1) == level()) {
|
|
5860 // Gather statistics on the young generation collection.
|
|
5861 collector()->stats().record_gc0_end(used());
|
|
5862 }
|
|
5863 }
|
|
5864
|
|
5865 CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() {
|
|
5866 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
5867 assert(gch->kind() == CollectedHeap::GenCollectedHeap,
|
|
5868 "Wrong type of heap");
|
|
5869 CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*)
|
|
5870 gch->gen_policy()->size_policy();
|
|
5871 assert(sp->is_gc_cms_adaptive_size_policy(),
|
|
5872 "Wrong type of size policy");
|
|
5873 return sp;
|
|
5874 }
|
|
5875
|
|
5876 void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() {
|
|
5877 if (PrintGCDetails && Verbose) {
|
|
5878 gclog_or_tty->print("Rotate from %d ", _debug_collection_type);
|
|
5879 }
|
|
5880 _debug_collection_type = (CollectionTypes) (_debug_collection_type + 1);
|
|
5881 _debug_collection_type =
|
|
5882 (CollectionTypes) (_debug_collection_type % Unknown_collection_type);
|
|
5883 if (PrintGCDetails && Verbose) {
|
|
5884 gclog_or_tty->print_cr("to %d ", _debug_collection_type);
|
|
5885 }
|
|
5886 }
|
|
5887
|
|
5888 void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen,
|
|
5889 bool asynch) {
|
|
5890 // We iterate over the space(s) underlying this generation,
|
|
5891 // checking the mark bit map to see if the bits corresponding
|
|
5892 // to specific blocks are marked or not. Blocks that are
|
|
5893 // marked are live and are not swept up. All remaining blocks
|
|
5894 // are swept up, with coalescing on-the-fly as we sweep up
|
|
5895 // contiguous free and/or garbage blocks:
|
|
5896 // We need to ensure that the sweeper synchronizes with allocators
|
|
5897 // and stop-the-world collectors. In particular, the following
|
|
5898 // locks are used:
|
|
5899 // . CMS token: if this is held, a stop the world collection cannot occur
|
|
5900 // . freelistLock: if this is held no allocation can occur from this
|
|
5901 // generation by another thread
|
|
5902 // . bitMapLock: if this is held, no other thread can access or update
|
|
5903 //
|
|
5904
|
|
5905 // Note that we need to hold the freelistLock if we use
|
|
5906 // block iterate below; else the iterator might go awry if
|
|
5907 // a mutator (or promotion) causes block contents to change
|
|
5908 // (for instance if the allocator divvies up a block).
|
|
5909 // If we hold the free list lock, for all practical purposes
|
|
5910 // young generation GC's can't occur (they'll usually need to
|
|
5911 // promote), so we might as well prevent all young generation
|
|
5912 // GC's while we do a sweeping step. For the same reason, we might
|
|
5913 // as well take the bit map lock for the entire duration
|
|
5914
|
|
5915 // check that we hold the requisite locks
|
|
5916 assert(have_cms_token(), "Should hold cms token");
|
|
5917 assert( (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token())
|
|
5918 || (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()),
|
|
5919 "Should possess CMS token to sweep");
|
|
5920 assert_lock_strong(gen->freelistLock());
|
|
5921 assert_lock_strong(bitMapLock());
|
|
5922
|
|
5923 assert(!_sweep_timer.is_active(), "Was switched off in an outer context");
|
|
5924 gen->cmsSpace()->beginSweepFLCensus((float)(_sweep_timer.seconds()),
|
|
5925 _sweep_estimate.padded_average());
|
|
5926 gen->setNearLargestChunk();
|
|
5927
|
|
5928 {
|
|
5929 SweepClosure sweepClosure(this, gen, &_markBitMap,
|
|
5930 CMSYield && asynch);
|
|
5931 gen->cmsSpace()->blk_iterate_careful(&sweepClosure);
|
|
5932 // We need to free-up/coalesce garbage/blocks from a
|
|
5933 // co-terminal free run. This is done in the SweepClosure
|
|
5934 // destructor; so, do not remove this scope, else the
|
|
5935 // end-of-sweep-census below will be off by a little bit.
|
|
5936 }
|
|
5937 gen->cmsSpace()->sweep_completed();
|
|
5938 gen->cmsSpace()->endSweepFLCensus(sweepCount());
|
|
5939 }
|
|
5940
|
|
5941 // Reset CMS data structures (for now just the marking bit map)
|
|
5942 // preparatory for the next cycle.
|
|
5943 void CMSCollector::reset(bool asynch) {
|
|
5944 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
5945 CMSAdaptiveSizePolicy* sp = size_policy();
|
|
5946 AdaptiveSizePolicyOutput(sp, gch->total_collections());
|
|
5947 if (asynch) {
|
|
5948 CMSTokenSyncWithLocks ts(true, bitMapLock());
|
|
5949
|
|
5950 // If the state is not "Resetting", the foreground thread
|
|
5951 // has done a collection and the resetting.
|
|
5952 if (_collectorState != Resetting) {
|
|
5953 assert(_collectorState == Idling, "The state should only change"
|
|
5954 " because the foreground collector has finished the collection");
|
|
5955 return;
|
|
5956 }
|
|
5957
|
|
5958 // Clear the mark bitmap (no grey objects to start with)
|
|
5959 // for the next cycle.
|
|
5960 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
|
|
5961 CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails);
|
|
5962
|
|
5963 HeapWord* curAddr = _markBitMap.startWord();
|
|
5964 while (curAddr < _markBitMap.endWord()) {
|
|
5965 size_t remaining = pointer_delta(_markBitMap.endWord(), curAddr);
|
|
5966 MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining));
|
|
5967 _markBitMap.clear_large_range(chunk);
|
|
5968 if (ConcurrentMarkSweepThread::should_yield() &&
|
|
5969 !foregroundGCIsActive() &&
|
|
5970 CMSYield) {
|
|
5971 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
5972 "CMS thread should hold CMS token");
|
|
5973 assert_lock_strong(bitMapLock());
|
|
5974 bitMapLock()->unlock();
|
|
5975 ConcurrentMarkSweepThread::desynchronize(true);
|
|
5976 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
5977 stopTimer();
|
|
5978 if (PrintCMSStatistics != 0) {
|
|
5979 incrementYields();
|
|
5980 }
|
|
5981 icms_wait();
|
|
5982
|
|
5983 // See the comment in coordinator_yield()
|
|
5984 for (unsigned i = 0; i < CMSYieldSleepCount &&
|
|
5985 ConcurrentMarkSweepThread::should_yield() &&
|
|
5986 !CMSCollector::foregroundGCIsActive(); ++i) {
|
|
5987 os::sleep(Thread::current(), 1, false);
|
|
5988 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
5989 }
|
|
5990
|
|
5991 ConcurrentMarkSweepThread::synchronize(true);
|
|
5992 bitMapLock()->lock_without_safepoint_check();
|
|
5993 startTimer();
|
|
5994 }
|
|
5995 curAddr = chunk.end();
|
|
5996 }
|
|
5997 _collectorState = Idling;
|
|
5998 } else {
|
|
5999 // already have the lock
|
|
6000 assert(_collectorState == Resetting, "just checking");
|
|
6001 assert_lock_strong(bitMapLock());
|
|
6002 _markBitMap.clear_all();
|
|
6003 _collectorState = Idling;
|
|
6004 }
|
|
6005
|
|
6006 // Stop incremental mode after a cycle completes, so that any future cycles
|
|
6007 // are triggered by allocation.
|
|
6008 stop_icms();
|
|
6009
|
|
6010 NOT_PRODUCT(
|
|
6011 if (RotateCMSCollectionTypes) {
|
|
6012 _cmsGen->rotate_debug_collection_type();
|
|
6013 }
|
|
6014 )
|
|
6015 }
|
|
6016
|
|
6017 void CMSCollector::do_CMS_operation(CMS_op_type op) {
|
|
6018 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
|
|
6019 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
|
|
6020 TraceTime t("GC", PrintGC, !PrintGCDetails, gclog_or_tty);
|
|
6021 TraceCollectorStats tcs(counters());
|
|
6022
|
|
6023 switch (op) {
|
|
6024 case CMS_op_checkpointRootsInitial: {
|
|
6025 checkpointRootsInitial(true); // asynch
|
|
6026 if (PrintGC) {
|
|
6027 _cmsGen->printOccupancy("initial-mark");
|
|
6028 }
|
|
6029 break;
|
|
6030 }
|
|
6031 case CMS_op_checkpointRootsFinal: {
|
|
6032 checkpointRootsFinal(true, // asynch
|
|
6033 false, // !clear_all_soft_refs
|
|
6034 false); // !init_mark_was_synchronous
|
|
6035 if (PrintGC) {
|
|
6036 _cmsGen->printOccupancy("remark");
|
|
6037 }
|
|
6038 break;
|
|
6039 }
|
|
6040 default:
|
|
6041 fatal("No such CMS_op");
|
|
6042 }
|
|
6043 }
|
|
6044
|
|
6045 #ifndef PRODUCT
|
|
6046 size_t const CMSCollector::skip_header_HeapWords() {
|
|
6047 return FreeChunk::header_size();
|
|
6048 }
|
|
6049
|
|
6050 // Try and collect here conditions that should hold when
|
|
6051 // CMS thread is exiting. The idea is that the foreground GC
|
|
6052 // thread should not be blocked if it wants to terminate
|
|
6053 // the CMS thread and yet continue to run the VM for a while
|
|
6054 // after that.
|
|
6055 void CMSCollector::verify_ok_to_terminate() const {
|
|
6056 assert(Thread::current()->is_ConcurrentGC_thread(),
|
|
6057 "should be called by CMS thread");
|
|
6058 assert(!_foregroundGCShouldWait, "should be false");
|
|
6059 // We could check here that all the various low-level locks
|
|
6060 // are not held by the CMS thread, but that is overkill; see
|
|
6061 // also CMSThread::verify_ok_to_terminate() where the CGC_lock
|
|
6062 // is checked.
|
|
6063 }
|
|
6064 #endif
|
|
6065
|
|
6066 size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const {
|
|
6067 assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1),
|
|
6068 "missing Printezis mark?");
|
|
6069 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2);
|
|
6070 size_t size = pointer_delta(nextOneAddr + 1, addr);
|
|
6071 assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
|
|
6072 "alignment problem");
|
|
6073 assert(size >= 3, "Necessary for Printezis marks to work");
|
|
6074 return size;
|
|
6075 }
|
|
6076
|
|
6077 // A variant of the above (block_size_using_printezis_bits()) except
|
|
6078 // that we return 0 if the P-bits are not yet set.
|
|
6079 size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const {
|
|
6080 if (_markBitMap.isMarked(addr)) {
|
|
6081 assert(_markBitMap.isMarked(addr + 1), "Missing Printezis bit?");
|
|
6082 HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2);
|
|
6083 size_t size = pointer_delta(nextOneAddr + 1, addr);
|
|
6084 assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
|
|
6085 "alignment problem");
|
|
6086 assert(size >= 3, "Necessary for Printezis marks to work");
|
|
6087 return size;
|
|
6088 } else {
|
|
6089 assert(!_markBitMap.isMarked(addr + 1), "Bit map inconsistency?");
|
|
6090 return 0;
|
|
6091 }
|
|
6092 }
|
|
6093
|
|
6094 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const {
|
|
6095 size_t sz = 0;
|
|
6096 oop p = (oop)addr;
|
|
6097 if (p->klass() != NULL && p->is_parsable()) {
|
|
6098 sz = CompactibleFreeListSpace::adjustObjectSize(p->size());
|
|
6099 } else {
|
|
6100 sz = block_size_using_printezis_bits(addr);
|
|
6101 }
|
|
6102 assert(sz > 0, "size must be nonzero");
|
|
6103 HeapWord* next_block = addr + sz;
|
|
6104 HeapWord* next_card = (HeapWord*)round_to((uintptr_t)next_block,
|
|
6105 CardTableModRefBS::card_size);
|
|
6106 assert(round_down((uintptr_t)addr, CardTableModRefBS::card_size) <
|
|
6107 round_down((uintptr_t)next_card, CardTableModRefBS::card_size),
|
|
6108 "must be different cards");
|
|
6109 return next_card;
|
|
6110 }
|
|
6111
|
|
6112
|
|
6113 // CMS Bit Map Wrapper /////////////////////////////////////////
|
|
6114
|
|
6115 // Construct a CMS bit map infrastructure, but don't create the
|
|
6116 // bit vector itself. That is done by a separate call CMSBitMap::allocate()
|
|
6117 // further below.
|
|
6118 CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name):
|
|
6119 _bm(NULL,0),
|
|
6120 _shifter(shifter),
|
|
6121 _lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL)
|
|
6122 {
|
|
6123 _bmStartWord = 0;
|
|
6124 _bmWordSize = 0;
|
|
6125 }
|
|
6126
|
|
6127 bool CMSBitMap::allocate(MemRegion mr) {
|
|
6128 _bmStartWord = mr.start();
|
|
6129 _bmWordSize = mr.word_size();
|
|
6130 ReservedSpace brs(ReservedSpace::allocation_align_size_up(
|
|
6131 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1));
|
|
6132 if (!brs.is_reserved()) {
|
|
6133 warning("CMS bit map allocation failure");
|
|
6134 return false;
|
|
6135 }
|
|
6136 // For now we'll just commit all of the bit map up fromt.
|
|
6137 // Later on we'll try to be more parsimonious with swap.
|
|
6138 if (!_virtual_space.initialize(brs, brs.size())) {
|
|
6139 warning("CMS bit map backing store failure");
|
|
6140 return false;
|
|
6141 }
|
|
6142 assert(_virtual_space.committed_size() == brs.size(),
|
|
6143 "didn't reserve backing store for all of CMS bit map?");
|
|
6144 _bm.set_map((uintptr_t*)_virtual_space.low());
|
|
6145 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >=
|
|
6146 _bmWordSize, "inconsistency in bit map sizing");
|
|
6147 _bm.set_size(_bmWordSize >> _shifter);
|
|
6148
|
|
6149 // bm.clear(); // can we rely on getting zero'd memory? verify below
|
|
6150 assert(isAllClear(),
|
|
6151 "Expected zero'd memory from ReservedSpace constructor");
|
|
6152 assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()),
|
|
6153 "consistency check");
|
|
6154 return true;
|
|
6155 }
|
|
6156
|
|
6157 void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) {
|
|
6158 HeapWord *next_addr, *end_addr, *last_addr;
|
|
6159 assert_locked();
|
|
6160 assert(covers(mr), "out-of-range error");
|
|
6161 // XXX assert that start and end are appropriately aligned
|
|
6162 for (next_addr = mr.start(), end_addr = mr.end();
|
|
6163 next_addr < end_addr; next_addr = last_addr) {
|
|
6164 MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr);
|
|
6165 last_addr = dirty_region.end();
|
|
6166 if (!dirty_region.is_empty()) {
|
|
6167 cl->do_MemRegion(dirty_region);
|
|
6168 } else {
|
|
6169 assert(last_addr == end_addr, "program logic");
|
|
6170 return;
|
|
6171 }
|
|
6172 }
|
|
6173 }
|
|
6174
|
|
6175 #ifndef PRODUCT
|
|
6176 void CMSBitMap::assert_locked() const {
|
|
6177 CMSLockVerifier::assert_locked(lock());
|
|
6178 }
|
|
6179
|
|
6180 bool CMSBitMap::covers(MemRegion mr) const {
|
|
6181 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
|
|
6182 assert((size_t)_bm.size() == (_bmWordSize >> _shifter),
|
|
6183 "size inconsistency");
|
|
6184 return (mr.start() >= _bmStartWord) &&
|
|
6185 (mr.end() <= endWord());
|
|
6186 }
|
|
6187
|
|
6188 bool CMSBitMap::covers(HeapWord* start, size_t size) const {
|
|
6189 return (start >= _bmStartWord && (start + size) <= endWord());
|
|
6190 }
|
|
6191
|
|
6192 void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) {
|
|
6193 // verify that there are no 1 bits in the interval [left, right)
|
|
6194 FalseBitMapClosure falseBitMapClosure;
|
|
6195 iterate(&falseBitMapClosure, left, right);
|
|
6196 }
|
|
6197
|
|
6198 void CMSBitMap::region_invariant(MemRegion mr)
|
|
6199 {
|
|
6200 assert_locked();
|
|
6201 // mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
|
|
6202 assert(!mr.is_empty(), "unexpected empty region");
|
|
6203 assert(covers(mr), "mr should be covered by bit map");
|
|
6204 // convert address range into offset range
|
|
6205 size_t start_ofs = heapWordToOffset(mr.start());
|
|
6206 // Make sure that end() is appropriately aligned
|
|
6207 assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(),
|
|
6208 (1 << (_shifter+LogHeapWordSize))),
|
|
6209 "Misaligned mr.end()");
|
|
6210 size_t end_ofs = heapWordToOffset(mr.end());
|
|
6211 assert(end_ofs > start_ofs, "Should mark at least one bit");
|
|
6212 }
|
|
6213
|
|
6214 #endif
|
|
6215
|
|
6216 bool CMSMarkStack::allocate(size_t size) {
|
|
6217 // allocate a stack of the requisite depth
|
|
6218 ReservedSpace rs(ReservedSpace::allocation_align_size_up(
|
|
6219 size * sizeof(oop)));
|
|
6220 if (!rs.is_reserved()) {
|
|
6221 warning("CMSMarkStack allocation failure");
|
|
6222 return false;
|
|
6223 }
|
|
6224 if (!_virtual_space.initialize(rs, rs.size())) {
|
|
6225 warning("CMSMarkStack backing store failure");
|
|
6226 return false;
|
|
6227 }
|
|
6228 assert(_virtual_space.committed_size() == rs.size(),
|
|
6229 "didn't reserve backing store for all of CMS stack?");
|
|
6230 _base = (oop*)(_virtual_space.low());
|
|
6231 _index = 0;
|
|
6232 _capacity = size;
|
|
6233 NOT_PRODUCT(_max_depth = 0);
|
|
6234 return true;
|
|
6235 }
|
|
6236
|
|
6237 // XXX FIX ME !!! In the MT case we come in here holding a
|
|
6238 // leaf lock. For printing we need to take a further lock
|
|
6239 // which has lower rank. We need to recallibrate the two
|
|
6240 // lock-ranks involved in order to be able to rpint the
|
|
6241 // messages below. (Or defer the printing to the caller.
|
|
6242 // For now we take the expedient path of just disabling the
|
|
6243 // messages for the problematic case.)
|
|
6244 void CMSMarkStack::expand() {
|
|
6245 assert(_capacity <= CMSMarkStackSizeMax, "stack bigger than permitted");
|
|
6246 if (_capacity == CMSMarkStackSizeMax) {
|
|
6247 if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) {
|
|
6248 // We print a warning message only once per CMS cycle.
|
|
6249 gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit");
|
|
6250 }
|
|
6251 return;
|
|
6252 }
|
|
6253 // Double capacity if possible
|
|
6254 size_t new_capacity = MIN2(_capacity*2, CMSMarkStackSizeMax);
|
|
6255 // Do not give up existing stack until we have managed to
|
|
6256 // get the double capacity that we desired.
|
|
6257 ReservedSpace rs(ReservedSpace::allocation_align_size_up(
|
|
6258 new_capacity * sizeof(oop)));
|
|
6259 if (rs.is_reserved()) {
|
|
6260 // Release the backing store associated with old stack
|
|
6261 _virtual_space.release();
|
|
6262 // Reinitialize virtual space for new stack
|
|
6263 if (!_virtual_space.initialize(rs, rs.size())) {
|
|
6264 fatal("Not enough swap for expanded marking stack");
|
|
6265 }
|
|
6266 _base = (oop*)(_virtual_space.low());
|
|
6267 _index = 0;
|
|
6268 _capacity = new_capacity;
|
|
6269 } else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) {
|
|
6270 // Failed to double capacity, continue;
|
|
6271 // we print a detail message only once per CMS cycle.
|
|
6272 gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to "
|
|
6273 SIZE_FORMAT"K",
|
|
6274 _capacity / K, new_capacity / K);
|
|
6275 }
|
|
6276 }
|
|
6277
|
|
6278
|
|
6279 // Closures
|
|
6280 // XXX: there seems to be a lot of code duplication here;
|
|
6281 // should refactor and consolidate common code.
|
|
6282
|
|
6283 // This closure is used to mark refs into the CMS generation in
|
|
6284 // the CMS bit map. Called at the first checkpoint. This closure
|
|
6285 // assumes that we do not need to re-mark dirty cards; if the CMS
|
|
6286 // generation on which this is used is not an oldest (modulo perm gen)
|
|
6287 // generation then this will lose younger_gen cards!
|
|
6288
|
|
6289 MarkRefsIntoClosure::MarkRefsIntoClosure(
|
|
6290 MemRegion span, CMSBitMap* bitMap, bool should_do_nmethods):
|
|
6291 _span(span),
|
|
6292 _bitMap(bitMap),
|
|
6293 _should_do_nmethods(should_do_nmethods)
|
|
6294 {
|
|
6295 assert(_ref_processor == NULL, "deliberately left NULL");
|
|
6296 assert(_bitMap->covers(_span), "_bitMap/_span mismatch");
|
|
6297 }
|
|
6298
|
|
6299 void MarkRefsIntoClosure::do_oop(oop* p) {
|
|
6300 // if p points into _span, then mark corresponding bit in _markBitMap
|
|
6301 oop thisOop = *p;
|
|
6302 if (thisOop != NULL) {
|
|
6303 assert(thisOop->is_oop(), "expected an oop");
|
|
6304 HeapWord* addr = (HeapWord*)thisOop;
|
|
6305 if (_span.contains(addr)) {
|
|
6306 // this should be made more efficient
|
|
6307 _bitMap->mark(addr);
|
|
6308 }
|
|
6309 }
|
|
6310 }
|
|
6311
|
|
6312 // A variant of the above, used for CMS marking verification.
|
|
6313 MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure(
|
|
6314 MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm,
|
|
6315 bool should_do_nmethods):
|
|
6316 _span(span),
|
|
6317 _verification_bm(verification_bm),
|
|
6318 _cms_bm(cms_bm),
|
|
6319 _should_do_nmethods(should_do_nmethods) {
|
|
6320 assert(_ref_processor == NULL, "deliberately left NULL");
|
|
6321 assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch");
|
|
6322 }
|
|
6323
|
|
6324 void MarkRefsIntoVerifyClosure::do_oop(oop* p) {
|
|
6325 // if p points into _span, then mark corresponding bit in _markBitMap
|
|
6326 oop this_oop = *p;
|
|
6327 if (this_oop != NULL) {
|
|
6328 assert(this_oop->is_oop(), "expected an oop");
|
|
6329 HeapWord* addr = (HeapWord*)this_oop;
|
|
6330 if (_span.contains(addr)) {
|
|
6331 _verification_bm->mark(addr);
|
|
6332 if (!_cms_bm->isMarked(addr)) {
|
|
6333 oop(addr)->print();
|
|
6334 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr);
|
|
6335 fatal("... aborting");
|
|
6336 }
|
|
6337 }
|
|
6338 }
|
|
6339 }
|
|
6340
|
|
6341 //////////////////////////////////////////////////
|
|
6342 // MarkRefsIntoAndScanClosure
|
|
6343 //////////////////////////////////////////////////
|
|
6344
|
|
6345 MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span,
|
|
6346 ReferenceProcessor* rp,
|
|
6347 CMSBitMap* bit_map,
|
|
6348 CMSBitMap* mod_union_table,
|
|
6349 CMSMarkStack* mark_stack,
|
|
6350 CMSMarkStack* revisit_stack,
|
|
6351 CMSCollector* collector,
|
|
6352 bool should_yield,
|
|
6353 bool concurrent_precleaning):
|
|
6354 _collector(collector),
|
|
6355 _span(span),
|
|
6356 _bit_map(bit_map),
|
|
6357 _mark_stack(mark_stack),
|
|
6358 _pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table,
|
|
6359 mark_stack, revisit_stack, concurrent_precleaning),
|
|
6360 _yield(should_yield),
|
|
6361 _concurrent_precleaning(concurrent_precleaning),
|
|
6362 _freelistLock(NULL)
|
|
6363 {
|
|
6364 _ref_processor = rp;
|
|
6365 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL");
|
|
6366 }
|
|
6367
|
|
6368 // This closure is used to mark refs into the CMS generation at the
|
|
6369 // second (final) checkpoint, and to scan and transitively follow
|
|
6370 // the unmarked oops. It is also used during the concurrent precleaning
|
|
6371 // phase while scanning objects on dirty cards in the CMS generation.
|
|
6372 // The marks are made in the marking bit map and the marking stack is
|
|
6373 // used for keeping the (newly) grey objects during the scan.
|
|
6374 // The parallel version (Par_...) appears further below.
|
|
6375 void MarkRefsIntoAndScanClosure::do_oop(oop* p) {
|
|
6376 oop this_oop = *p;
|
|
6377 if (this_oop != NULL) {
|
|
6378 assert(this_oop->is_oop(), "expected an oop");
|
|
6379 HeapWord* addr = (HeapWord*)this_oop;
|
|
6380 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)");
|
|
6381 assert(_collector->overflow_list_is_empty(), "should be empty");
|
|
6382 if (_span.contains(addr) &&
|
|
6383 !_bit_map->isMarked(addr)) {
|
|
6384 // mark bit map (object is now grey)
|
|
6385 _bit_map->mark(addr);
|
|
6386 // push on marking stack (stack should be empty), and drain the
|
|
6387 // stack by applying this closure to the oops in the oops popped
|
|
6388 // from the stack (i.e. blacken the grey objects)
|
|
6389 bool res = _mark_stack->push(this_oop);
|
|
6390 assert(res, "Should have space to push on empty stack");
|
|
6391 do {
|
|
6392 oop new_oop = _mark_stack->pop();
|
|
6393 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop");
|
|
6394 assert(new_oop->is_parsable(), "Found unparsable oop");
|
|
6395 assert(_bit_map->isMarked((HeapWord*)new_oop),
|
|
6396 "only grey objects on this stack");
|
|
6397 // iterate over the oops in this oop, marking and pushing
|
|
6398 // the ones in CMS heap (i.e. in _span).
|
|
6399 new_oop->oop_iterate(&_pushAndMarkClosure);
|
|
6400 // check if it's time to yield
|
|
6401 do_yield_check();
|
|
6402 } while (!_mark_stack->isEmpty() ||
|
|
6403 (!_concurrent_precleaning && take_from_overflow_list()));
|
|
6404 // if marking stack is empty, and we are not doing this
|
|
6405 // during precleaning, then check the overflow list
|
|
6406 }
|
|
6407 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)");
|
|
6408 assert(_collector->overflow_list_is_empty(),
|
|
6409 "overflow list was drained above");
|
|
6410 // We could restore evacuated mark words, if any, used for
|
|
6411 // overflow list links here because the overflow list is
|
|
6412 // provably empty here. That would reduce the maximum
|
|
6413 // size requirements for preserved_{oop,mark}_stack.
|
|
6414 // But we'll just postpone it until we are all done
|
|
6415 // so we can just stream through.
|
|
6416 if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) {
|
|
6417 _collector->restore_preserved_marks_if_any();
|
|
6418 assert(_collector->no_preserved_marks(), "No preserved marks");
|
|
6419 }
|
|
6420 assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(),
|
|
6421 "All preserved marks should have been restored above");
|
|
6422 }
|
|
6423 }
|
|
6424
|
|
6425 void MarkRefsIntoAndScanClosure::do_yield_work() {
|
|
6426 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
6427 "CMS thread should hold CMS token");
|
|
6428 assert_lock_strong(_freelistLock);
|
|
6429 assert_lock_strong(_bit_map->lock());
|
|
6430 // relinquish the free_list_lock and bitMaplock()
|
|
6431 _bit_map->lock()->unlock();
|
|
6432 _freelistLock->unlock();
|
|
6433 ConcurrentMarkSweepThread::desynchronize(true);
|
|
6434 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
6435 _collector->stopTimer();
|
|
6436 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
|
|
6437 if (PrintCMSStatistics != 0) {
|
|
6438 _collector->incrementYields();
|
|
6439 }
|
|
6440 _collector->icms_wait();
|
|
6441
|
|
6442 // See the comment in coordinator_yield()
|
|
6443 for (unsigned i = 0; i < CMSYieldSleepCount &&
|
|
6444 ConcurrentMarkSweepThread::should_yield() &&
|
|
6445 !CMSCollector::foregroundGCIsActive(); ++i) {
|
|
6446 os::sleep(Thread::current(), 1, false);
|
|
6447 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
6448 }
|
|
6449
|
|
6450 ConcurrentMarkSweepThread::synchronize(true);
|
|
6451 _freelistLock->lock_without_safepoint_check();
|
|
6452 _bit_map->lock()->lock_without_safepoint_check();
|
|
6453 _collector->startTimer();
|
|
6454 }
|
|
6455
|
|
6456 ///////////////////////////////////////////////////////////
|
|
6457 // Par_MarkRefsIntoAndScanClosure: a parallel version of
|
|
6458 // MarkRefsIntoAndScanClosure
|
|
6459 ///////////////////////////////////////////////////////////
|
|
6460 Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure(
|
|
6461 CMSCollector* collector, MemRegion span, ReferenceProcessor* rp,
|
|
6462 CMSBitMap* bit_map, OopTaskQueue* work_queue, CMSMarkStack* revisit_stack):
|
|
6463 _span(span),
|
|
6464 _bit_map(bit_map),
|
|
6465 _work_queue(work_queue),
|
|
6466 _low_water_mark(MIN2((uint)(work_queue->max_elems()/4),
|
|
6467 (uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))),
|
|
6468 _par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue,
|
|
6469 revisit_stack)
|
|
6470 {
|
|
6471 _ref_processor = rp;
|
|
6472 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL");
|
|
6473 }
|
|
6474
|
|
6475 // This closure is used to mark refs into the CMS generation at the
|
|
6476 // second (final) checkpoint, and to scan and transitively follow
|
|
6477 // the unmarked oops. The marks are made in the marking bit map and
|
|
6478 // the work_queue is used for keeping the (newly) grey objects during
|
|
6479 // the scan phase whence they are also available for stealing by parallel
|
|
6480 // threads. Since the marking bit map is shared, updates are
|
|
6481 // synchronized (via CAS).
|
|
6482 void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) {
|
|
6483 oop this_oop = *p;
|
|
6484 if (this_oop != NULL) {
|
|
6485 // Ignore mark word because this could be an already marked oop
|
|
6486 // that may be chained at the end of the overflow list.
|
|
6487 assert(this_oop->is_oop(true /* ignore mark word */), "expected an oop");
|
|
6488 HeapWord* addr = (HeapWord*)this_oop;
|
|
6489 if (_span.contains(addr) &&
|
|
6490 !_bit_map->isMarked(addr)) {
|
|
6491 // mark bit map (object will become grey):
|
|
6492 // It is possible for several threads to be
|
|
6493 // trying to "claim" this object concurrently;
|
|
6494 // the unique thread that succeeds in marking the
|
|
6495 // object first will do the subsequent push on
|
|
6496 // to the work queue (or overflow list).
|
|
6497 if (_bit_map->par_mark(addr)) {
|
|
6498 // push on work_queue (which may not be empty), and trim the
|
|
6499 // queue to an appropriate length by applying this closure to
|
|
6500 // the oops in the oops popped from the stack (i.e. blacken the
|
|
6501 // grey objects)
|
|
6502 bool res = _work_queue->push(this_oop);
|
|
6503 assert(res, "Low water mark should be less than capacity?");
|
|
6504 trim_queue(_low_water_mark);
|
|
6505 } // Else, another thread claimed the object
|
|
6506 }
|
|
6507 }
|
|
6508 }
|
|
6509
|
|
6510 // This closure is used to rescan the marked objects on the dirty cards
|
|
6511 // in the mod union table and the card table proper.
|
|
6512 size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m(
|
|
6513 oop p, MemRegion mr) {
|
|
6514
|
|
6515 size_t size = 0;
|
|
6516 HeapWord* addr = (HeapWord*)p;
|
|
6517 DEBUG_ONLY(_collector->verify_work_stacks_empty();)
|
|
6518 assert(_span.contains(addr), "we are scanning the CMS generation");
|
|
6519 // check if it's time to yield
|
|
6520 if (do_yield_check()) {
|
|
6521 // We yielded for some foreground stop-world work,
|
|
6522 // and we have been asked to abort this ongoing preclean cycle.
|
|
6523 return 0;
|
|
6524 }
|
|
6525 if (_bitMap->isMarked(addr)) {
|
|
6526 // it's marked; is it potentially uninitialized?
|
|
6527 if (p->klass() != NULL) {
|
|
6528 if (CMSPermGenPrecleaningEnabled && !p->is_parsable()) {
|
|
6529 // Signal precleaning to redirty the card since
|
|
6530 // the klass pointer is already installed.
|
|
6531 assert(size == 0, "Initial value");
|
|
6532 } else {
|
|
6533 assert(p->is_parsable(), "must be parsable.");
|
|
6534 // an initialized object; ignore mark word in verification below
|
|
6535 // since we are running concurrent with mutators
|
|
6536 assert(p->is_oop(true), "should be an oop");
|
|
6537 if (p->is_objArray()) {
|
|
6538 // objArrays are precisely marked; restrict scanning
|
|
6539 // to dirty cards only.
|
|
6540 size = p->oop_iterate(_scanningClosure, mr);
|
|
6541 assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
|
|
6542 "adjustObjectSize should be the identity for array sizes, "
|
|
6543 "which are necessarily larger than minimum object size of "
|
|
6544 "two heap words");
|
|
6545 } else {
|
|
6546 // A non-array may have been imprecisely marked; we need
|
|
6547 // to scan object in its entirety.
|
|
6548 size = CompactibleFreeListSpace::adjustObjectSize(
|
|
6549 p->oop_iterate(_scanningClosure));
|
|
6550 }
|
|
6551 #ifdef DEBUG
|
|
6552 size_t direct_size =
|
|
6553 CompactibleFreeListSpace::adjustObjectSize(p->size());
|
|
6554 assert(size == direct_size, "Inconsistency in size");
|
|
6555 assert(size >= 3, "Necessary for Printezis marks to work");
|
|
6556 if (!_bitMap->isMarked(addr+1)) {
|
|
6557 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size);
|
|
6558 } else {
|
|
6559 _bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1);
|
|
6560 assert(_bitMap->isMarked(addr+size-1),
|
|
6561 "inconsistent Printezis mark");
|
|
6562 }
|
|
6563 #endif // DEBUG
|
|
6564 }
|
|
6565 } else {
|
|
6566 // an unitialized object
|
|
6567 assert(_bitMap->isMarked(addr+1), "missing Printezis mark?");
|
|
6568 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2);
|
|
6569 size = pointer_delta(nextOneAddr + 1, addr);
|
|
6570 assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
|
|
6571 "alignment problem");
|
|
6572 // Note that pre-cleaning needn't redirty the card. OopDesc::set_klass()
|
|
6573 // will dirty the card when the klass pointer is installed in the
|
|
6574 // object (signalling the completion of initialization).
|
|
6575 }
|
|
6576 } else {
|
|
6577 // Either a not yet marked object or an uninitialized object
|
|
6578 if (p->klass() == NULL || !p->is_parsable()) {
|
|
6579 // An uninitialized object, skip to the next card, since
|
|
6580 // we may not be able to read its P-bits yet.
|
|
6581 assert(size == 0, "Initial value");
|
|
6582 } else {
|
|
6583 // An object not (yet) reached by marking: we merely need to
|
|
6584 // compute its size so as to go look at the next block.
|
|
6585 assert(p->is_oop(true), "should be an oop");
|
|
6586 size = CompactibleFreeListSpace::adjustObjectSize(p->size());
|
|
6587 }
|
|
6588 }
|
|
6589 DEBUG_ONLY(_collector->verify_work_stacks_empty();)
|
|
6590 return size;
|
|
6591 }
|
|
6592
|
|
6593 void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() {
|
|
6594 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
6595 "CMS thread should hold CMS token");
|
|
6596 assert_lock_strong(_freelistLock);
|
|
6597 assert_lock_strong(_bitMap->lock());
|
|
6598 // relinquish the free_list_lock and bitMaplock()
|
|
6599 _bitMap->lock()->unlock();
|
|
6600 _freelistLock->unlock();
|
|
6601 ConcurrentMarkSweepThread::desynchronize(true);
|
|
6602 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
6603 _collector->stopTimer();
|
|
6604 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
|
|
6605 if (PrintCMSStatistics != 0) {
|
|
6606 _collector->incrementYields();
|
|
6607 }
|
|
6608 _collector->icms_wait();
|
|
6609
|
|
6610 // See the comment in coordinator_yield()
|
|
6611 for (unsigned i = 0; i < CMSYieldSleepCount &&
|
|
6612 ConcurrentMarkSweepThread::should_yield() &&
|
|
6613 !CMSCollector::foregroundGCIsActive(); ++i) {
|
|
6614 os::sleep(Thread::current(), 1, false);
|
|
6615 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
6616 }
|
|
6617
|
|
6618 ConcurrentMarkSweepThread::synchronize(true);
|
|
6619 _freelistLock->lock_without_safepoint_check();
|
|
6620 _bitMap->lock()->lock_without_safepoint_check();
|
|
6621 _collector->startTimer();
|
|
6622 }
|
|
6623
|
|
6624
|
|
6625 //////////////////////////////////////////////////////////////////
|
|
6626 // SurvivorSpacePrecleanClosure
|
|
6627 //////////////////////////////////////////////////////////////////
|
|
6628 // This (single-threaded) closure is used to preclean the oops in
|
|
6629 // the survivor spaces.
|
|
6630 size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) {
|
|
6631
|
|
6632 HeapWord* addr = (HeapWord*)p;
|
|
6633 DEBUG_ONLY(_collector->verify_work_stacks_empty();)
|
|
6634 assert(!_span.contains(addr), "we are scanning the survivor spaces");
|
|
6635 assert(p->klass() != NULL, "object should be initializd");
|
|
6636 assert(p->is_parsable(), "must be parsable.");
|
|
6637 // an initialized object; ignore mark word in verification below
|
|
6638 // since we are running concurrent with mutators
|
|
6639 assert(p->is_oop(true), "should be an oop");
|
|
6640 // Note that we do not yield while we iterate over
|
|
6641 // the interior oops of p, pushing the relevant ones
|
|
6642 // on our marking stack.
|
|
6643 size_t size = p->oop_iterate(_scanning_closure);
|
|
6644 do_yield_check();
|
|
6645 // Observe that below, we do not abandon the preclean
|
|
6646 // phase as soon as we should; rather we empty the
|
|
6647 // marking stack before returning. This is to satisfy
|
|
6648 // some existing assertions. In general, it may be a
|
|
6649 // good idea to abort immediately and complete the marking
|
|
6650 // from the grey objects at a later time.
|
|
6651 while (!_mark_stack->isEmpty()) {
|
|
6652 oop new_oop = _mark_stack->pop();
|
|
6653 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop");
|
|
6654 assert(new_oop->is_parsable(), "Found unparsable oop");
|
|
6655 assert(_bit_map->isMarked((HeapWord*)new_oop),
|
|
6656 "only grey objects on this stack");
|
|
6657 // iterate over the oops in this oop, marking and pushing
|
|
6658 // the ones in CMS heap (i.e. in _span).
|
|
6659 new_oop->oop_iterate(_scanning_closure);
|
|
6660 // check if it's time to yield
|
|
6661 do_yield_check();
|
|
6662 }
|
|
6663 unsigned int after_count =
|
|
6664 GenCollectedHeap::heap()->total_collections();
|
|
6665 bool abort = (_before_count != after_count) ||
|
|
6666 _collector->should_abort_preclean();
|
|
6667 return abort ? 0 : size;
|
|
6668 }
|
|
6669
|
|
6670 void SurvivorSpacePrecleanClosure::do_yield_work() {
|
|
6671 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
6672 "CMS thread should hold CMS token");
|
|
6673 assert_lock_strong(_bit_map->lock());
|
|
6674 // Relinquish the bit map lock
|
|
6675 _bit_map->lock()->unlock();
|
|
6676 ConcurrentMarkSweepThread::desynchronize(true);
|
|
6677 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
6678 _collector->stopTimer();
|
|
6679 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
|
|
6680 if (PrintCMSStatistics != 0) {
|
|
6681 _collector->incrementYields();
|
|
6682 }
|
|
6683 _collector->icms_wait();
|
|
6684
|
|
6685 // See the comment in coordinator_yield()
|
|
6686 for (unsigned i = 0; i < CMSYieldSleepCount &&
|
|
6687 ConcurrentMarkSweepThread::should_yield() &&
|
|
6688 !CMSCollector::foregroundGCIsActive(); ++i) {
|
|
6689 os::sleep(Thread::current(), 1, false);
|
|
6690 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
6691 }
|
|
6692
|
|
6693 ConcurrentMarkSweepThread::synchronize(true);
|
|
6694 _bit_map->lock()->lock_without_safepoint_check();
|
|
6695 _collector->startTimer();
|
|
6696 }
|
|
6697
|
|
6698 // This closure is used to rescan the marked objects on the dirty cards
|
|
6699 // in the mod union table and the card table proper. In the parallel
|
|
6700 // case, although the bitMap is shared, we do a single read so the
|
|
6701 // isMarked() query is "safe".
|
|
6702 bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) {
|
|
6703 // Ignore mark word because we are running concurrent with mutators
|
|
6704 assert(p->is_oop_or_null(true), "expected an oop or null");
|
|
6705 HeapWord* addr = (HeapWord*)p;
|
|
6706 assert(_span.contains(addr), "we are scanning the CMS generation");
|
|
6707 bool is_obj_array = false;
|
|
6708 #ifdef DEBUG
|
|
6709 if (!_parallel) {
|
|
6710 assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)");
|
|
6711 assert(_collector->overflow_list_is_empty(),
|
|
6712 "overflow list should be empty");
|
|
6713
|
|
6714 }
|
|
6715 #endif // DEBUG
|
|
6716 if (_bit_map->isMarked(addr)) {
|
|
6717 // Obj arrays are precisely marked, non-arrays are not;
|
|
6718 // so we scan objArrays precisely and non-arrays in their
|
|
6719 // entirety.
|
|
6720 if (p->is_objArray()) {
|
|
6721 is_obj_array = true;
|
|
6722 if (_parallel) {
|
|
6723 p->oop_iterate(_par_scan_closure, mr);
|
|
6724 } else {
|
|
6725 p->oop_iterate(_scan_closure, mr);
|
|
6726 }
|
|
6727 } else {
|
|
6728 if (_parallel) {
|
|
6729 p->oop_iterate(_par_scan_closure);
|
|
6730 } else {
|
|
6731 p->oop_iterate(_scan_closure);
|
|
6732 }
|
|
6733 }
|
|
6734 }
|
|
6735 #ifdef DEBUG
|
|
6736 if (!_parallel) {
|
|
6737 assert(_mark_stack->isEmpty(), "post-condition (eager drainage)");
|
|
6738 assert(_collector->overflow_list_is_empty(),
|
|
6739 "overflow list should be empty");
|
|
6740
|
|
6741 }
|
|
6742 #endif // DEBUG
|
|
6743 return is_obj_array;
|
|
6744 }
|
|
6745
|
|
6746 MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector,
|
|
6747 MemRegion span,
|
|
6748 CMSBitMap* bitMap, CMSMarkStack* markStack,
|
|
6749 CMSMarkStack* revisitStack,
|
|
6750 bool should_yield, bool verifying):
|
|
6751 _collector(collector),
|
|
6752 _span(span),
|
|
6753 _bitMap(bitMap),
|
|
6754 _mut(&collector->_modUnionTable),
|
|
6755 _markStack(markStack),
|
|
6756 _revisitStack(revisitStack),
|
|
6757 _yield(should_yield),
|
|
6758 _skipBits(0)
|
|
6759 {
|
|
6760 assert(_markStack->isEmpty(), "stack should be empty");
|
|
6761 _finger = _bitMap->startWord();
|
|
6762 _threshold = _finger;
|
|
6763 assert(_collector->_restart_addr == NULL, "Sanity check");
|
|
6764 assert(_span.contains(_finger), "Out of bounds _finger?");
|
|
6765 DEBUG_ONLY(_verifying = verifying;)
|
|
6766 }
|
|
6767
|
|
6768 void MarkFromRootsClosure::reset(HeapWord* addr) {
|
|
6769 assert(_markStack->isEmpty(), "would cause duplicates on stack");
|
|
6770 assert(_span.contains(addr), "Out of bounds _finger?");
|
|
6771 _finger = addr;
|
|
6772 _threshold = (HeapWord*)round_to(
|
|
6773 (intptr_t)_finger, CardTableModRefBS::card_size);
|
|
6774 }
|
|
6775
|
|
6776 // Should revisit to see if this should be restructured for
|
|
6777 // greater efficiency.
|
|
6778 void MarkFromRootsClosure::do_bit(size_t offset) {
|
|
6779 if (_skipBits > 0) {
|
|
6780 _skipBits--;
|
|
6781 return;
|
|
6782 }
|
|
6783 // convert offset into a HeapWord*
|
|
6784 HeapWord* addr = _bitMap->startWord() + offset;
|
|
6785 assert(_bitMap->endWord() && addr < _bitMap->endWord(),
|
|
6786 "address out of range");
|
|
6787 assert(_bitMap->isMarked(addr), "tautology");
|
|
6788 if (_bitMap->isMarked(addr+1)) {
|
|
6789 // this is an allocated but not yet initialized object
|
|
6790 assert(_skipBits == 0, "tautology");
|
|
6791 _skipBits = 2; // skip next two marked bits ("Printezis-marks")
|
|
6792 oop p = oop(addr);
|
|
6793 if (p->klass() == NULL || !p->is_parsable()) {
|
|
6794 DEBUG_ONLY(if (!_verifying) {)
|
|
6795 // We re-dirty the cards on which this object lies and increase
|
|
6796 // the _threshold so that we'll come back to scan this object
|
|
6797 // during the preclean or remark phase. (CMSCleanOnEnter)
|
|
6798 if (CMSCleanOnEnter) {
|
|
6799 size_t sz = _collector->block_size_using_printezis_bits(addr);
|
|
6800 HeapWord* start_card_addr = (HeapWord*)round_down(
|
|
6801 (intptr_t)addr, CardTableModRefBS::card_size);
|
|
6802 HeapWord* end_card_addr = (HeapWord*)round_to(
|
|
6803 (intptr_t)(addr+sz), CardTableModRefBS::card_size);
|
|
6804 MemRegion redirty_range = MemRegion(start_card_addr, end_card_addr);
|
|
6805 assert(!redirty_range.is_empty(), "Arithmetical tautology");
|
|
6806 // Bump _threshold to end_card_addr; note that
|
|
6807 // _threshold cannot possibly exceed end_card_addr, anyhow.
|
|
6808 // This prevents future clearing of the card as the scan proceeds
|
|
6809 // to the right.
|
|
6810 assert(_threshold <= end_card_addr,
|
|
6811 "Because we are just scanning into this object");
|
|
6812 if (_threshold < end_card_addr) {
|
|
6813 _threshold = end_card_addr;
|
|
6814 }
|
|
6815 if (p->klass() != NULL) {
|
|
6816 // Redirty the range of cards...
|
|
6817 _mut->mark_range(redirty_range);
|
|
6818 } // ...else the setting of klass will dirty the card anyway.
|
|
6819 }
|
|
6820 DEBUG_ONLY(})
|
|
6821 return;
|
|
6822 }
|
|
6823 }
|
|
6824 scanOopsInOop(addr);
|
|
6825 }
|
|
6826
|
|
6827 // We take a break if we've been at this for a while,
|
|
6828 // so as to avoid monopolizing the locks involved.
|
|
6829 void MarkFromRootsClosure::do_yield_work() {
|
|
6830 // First give up the locks, then yield, then re-lock
|
|
6831 // We should probably use a constructor/destructor idiom to
|
|
6832 // do this unlock/lock or modify the MutexUnlocker class to
|
|
6833 // serve our purpose. XXX
|
|
6834 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
6835 "CMS thread should hold CMS token");
|
|
6836 assert_lock_strong(_bitMap->lock());
|
|
6837 _bitMap->lock()->unlock();
|
|
6838 ConcurrentMarkSweepThread::desynchronize(true);
|
|
6839 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
6840 _collector->stopTimer();
|
|
6841 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
|
|
6842 if (PrintCMSStatistics != 0) {
|
|
6843 _collector->incrementYields();
|
|
6844 }
|
|
6845 _collector->icms_wait();
|
|
6846
|
|
6847 // See the comment in coordinator_yield()
|
|
6848 for (unsigned i = 0; i < CMSYieldSleepCount &&
|
|
6849 ConcurrentMarkSweepThread::should_yield() &&
|
|
6850 !CMSCollector::foregroundGCIsActive(); ++i) {
|
|
6851 os::sleep(Thread::current(), 1, false);
|
|
6852 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
6853 }
|
|
6854
|
|
6855 ConcurrentMarkSweepThread::synchronize(true);
|
|
6856 _bitMap->lock()->lock_without_safepoint_check();
|
|
6857 _collector->startTimer();
|
|
6858 }
|
|
6859
|
|
6860 void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) {
|
|
6861 assert(_bitMap->isMarked(ptr), "expected bit to be set");
|
|
6862 assert(_markStack->isEmpty(),
|
|
6863 "should drain stack to limit stack usage");
|
|
6864 // convert ptr to an oop preparatory to scanning
|
|
6865 oop this_oop = oop(ptr);
|
|
6866 // Ignore mark word in verification below, since we
|
|
6867 // may be running concurrent with mutators.
|
|
6868 assert(this_oop->is_oop(true), "should be an oop");
|
|
6869 assert(_finger <= ptr, "_finger runneth ahead");
|
|
6870 // advance the finger to right end of this object
|
|
6871 _finger = ptr + this_oop->size();
|
|
6872 assert(_finger > ptr, "we just incremented it above");
|
|
6873 // On large heaps, it may take us some time to get through
|
|
6874 // the marking phase (especially if running iCMS). During
|
|
6875 // this time it's possible that a lot of mutations have
|
|
6876 // accumulated in the card table and the mod union table --
|
|
6877 // these mutation records are redundant until we have
|
|
6878 // actually traced into the corresponding card.
|
|
6879 // Here, we check whether advancing the finger would make
|
|
6880 // us cross into a new card, and if so clear corresponding
|
|
6881 // cards in the MUT (preclean them in the card-table in the
|
|
6882 // future).
|
|
6883
|
|
6884 DEBUG_ONLY(if (!_verifying) {)
|
|
6885 // The clean-on-enter optimization is disabled by default,
|
|
6886 // until we fix 6178663.
|
|
6887 if (CMSCleanOnEnter && (_finger > _threshold)) {
|
|
6888 // [_threshold, _finger) represents the interval
|
|
6889 // of cards to be cleared in MUT (or precleaned in card table).
|
|
6890 // The set of cards to be cleared is all those that overlap
|
|
6891 // with the interval [_threshold, _finger); note that
|
|
6892 // _threshold is always kept card-aligned but _finger isn't
|
|
6893 // always card-aligned.
|
|
6894 HeapWord* old_threshold = _threshold;
|
|
6895 assert(old_threshold == (HeapWord*)round_to(
|
|
6896 (intptr_t)old_threshold, CardTableModRefBS::card_size),
|
|
6897 "_threshold should always be card-aligned");
|
|
6898 _threshold = (HeapWord*)round_to(
|
|
6899 (intptr_t)_finger, CardTableModRefBS::card_size);
|
|
6900 MemRegion mr(old_threshold, _threshold);
|
|
6901 assert(!mr.is_empty(), "Control point invariant");
|
|
6902 assert(_span.contains(mr), "Should clear within span");
|
|
6903 // XXX When _finger crosses from old gen into perm gen
|
|
6904 // we may be doing unnecessary cleaning; do better in the
|
|
6905 // future by detecting that condition and clearing fewer
|
|
6906 // MUT/CT entries.
|
|
6907 _mut->clear_range(mr);
|
|
6908 }
|
|
6909 DEBUG_ONLY(})
|
|
6910
|
|
6911 // Note: the finger doesn't advance while we drain
|
|
6912 // the stack below.
|
|
6913 PushOrMarkClosure pushOrMarkClosure(_collector,
|
|
6914 _span, _bitMap, _markStack,
|
|
6915 _revisitStack,
|
|
6916 _finger, this);
|
|
6917 bool res = _markStack->push(this_oop);
|
|
6918 assert(res, "Empty non-zero size stack should have space for single push");
|
|
6919 while (!_markStack->isEmpty()) {
|
|
6920 oop new_oop = _markStack->pop();
|
|
6921 // Skip verifying header mark word below because we are
|
|
6922 // running concurrent with mutators.
|
|
6923 assert(new_oop->is_oop(true), "Oops! expected to pop an oop");
|
|
6924 // now scan this oop's oops
|
|
6925 new_oop->oop_iterate(&pushOrMarkClosure);
|
|
6926 do_yield_check();
|
|
6927 }
|
|
6928 assert(_markStack->isEmpty(), "tautology, emphasizing post-condition");
|
|
6929 }
|
|
6930
|
|
6931 Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task,
|
|
6932 CMSCollector* collector, MemRegion span,
|
|
6933 CMSBitMap* bit_map,
|
|
6934 OopTaskQueue* work_queue,
|
|
6935 CMSMarkStack* overflow_stack,
|
|
6936 CMSMarkStack* revisit_stack,
|
|
6937 bool should_yield):
|
|
6938 _collector(collector),
|
|
6939 _whole_span(collector->_span),
|
|
6940 _span(span),
|
|
6941 _bit_map(bit_map),
|
|
6942 _mut(&collector->_modUnionTable),
|
|
6943 _work_queue(work_queue),
|
|
6944 _overflow_stack(overflow_stack),
|
|
6945 _revisit_stack(revisit_stack),
|
|
6946 _yield(should_yield),
|
|
6947 _skip_bits(0),
|
|
6948 _task(task)
|
|
6949 {
|
|
6950 assert(_work_queue->size() == 0, "work_queue should be empty");
|
|
6951 _finger = span.start();
|
|
6952 _threshold = _finger; // XXX Defer clear-on-enter optimization for now
|
|
6953 assert(_span.contains(_finger), "Out of bounds _finger?");
|
|
6954 }
|
|
6955
|
|
6956 // Should revisit to see if this should be restructured for
|
|
6957 // greater efficiency.
|
|
6958 void Par_MarkFromRootsClosure::do_bit(size_t offset) {
|
|
6959 if (_skip_bits > 0) {
|
|
6960 _skip_bits--;
|
|
6961 return;
|
|
6962 }
|
|
6963 // convert offset into a HeapWord*
|
|
6964 HeapWord* addr = _bit_map->startWord() + offset;
|
|
6965 assert(_bit_map->endWord() && addr < _bit_map->endWord(),
|
|
6966 "address out of range");
|
|
6967 assert(_bit_map->isMarked(addr), "tautology");
|
|
6968 if (_bit_map->isMarked(addr+1)) {
|
|
6969 // this is an allocated object that might not yet be initialized
|
|
6970 assert(_skip_bits == 0, "tautology");
|
|
6971 _skip_bits = 2; // skip next two marked bits ("Printezis-marks")
|
|
6972 oop p = oop(addr);
|
|
6973 if (p->klass() == NULL || !p->is_parsable()) {
|
|
6974 // in the case of Clean-on-Enter optimization, redirty card
|
|
6975 // and avoid clearing card by increasing the threshold.
|
|
6976 return;
|
|
6977 }
|
|
6978 }
|
|
6979 scan_oops_in_oop(addr);
|
|
6980 }
|
|
6981
|
|
6982 void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) {
|
|
6983 assert(_bit_map->isMarked(ptr), "expected bit to be set");
|
|
6984 // Should we assert that our work queue is empty or
|
|
6985 // below some drain limit?
|
|
6986 assert(_work_queue->size() == 0,
|
|
6987 "should drain stack to limit stack usage");
|
|
6988 // convert ptr to an oop preparatory to scanning
|
|
6989 oop this_oop = oop(ptr);
|
|
6990 // Ignore mark word in verification below, since we
|
|
6991 // may be running concurrent with mutators.
|
|
6992 assert(this_oop->is_oop(true), "should be an oop");
|
|
6993 assert(_finger <= ptr, "_finger runneth ahead");
|
|
6994 // advance the finger to right end of this object
|
|
6995 _finger = ptr + this_oop->size();
|
|
6996 assert(_finger > ptr, "we just incremented it above");
|
|
6997 // On large heaps, it may take us some time to get through
|
|
6998 // the marking phase (especially if running iCMS). During
|
|
6999 // this time it's possible that a lot of mutations have
|
|
7000 // accumulated in the card table and the mod union table --
|
|
7001 // these mutation records are redundant until we have
|
|
7002 // actually traced into the corresponding card.
|
|
7003 // Here, we check whether advancing the finger would make
|
|
7004 // us cross into a new card, and if so clear corresponding
|
|
7005 // cards in the MUT (preclean them in the card-table in the
|
|
7006 // future).
|
|
7007
|
|
7008 // The clean-on-enter optimization is disabled by default,
|
|
7009 // until we fix 6178663.
|
|
7010 if (CMSCleanOnEnter && (_finger > _threshold)) {
|
|
7011 // [_threshold, _finger) represents the interval
|
|
7012 // of cards to be cleared in MUT (or precleaned in card table).
|
|
7013 // The set of cards to be cleared is all those that overlap
|
|
7014 // with the interval [_threshold, _finger); note that
|
|
7015 // _threshold is always kept card-aligned but _finger isn't
|
|
7016 // always card-aligned.
|
|
7017 HeapWord* old_threshold = _threshold;
|
|
7018 assert(old_threshold == (HeapWord*)round_to(
|
|
7019 (intptr_t)old_threshold, CardTableModRefBS::card_size),
|
|
7020 "_threshold should always be card-aligned");
|
|
7021 _threshold = (HeapWord*)round_to(
|
|
7022 (intptr_t)_finger, CardTableModRefBS::card_size);
|
|
7023 MemRegion mr(old_threshold, _threshold);
|
|
7024 assert(!mr.is_empty(), "Control point invariant");
|
|
7025 assert(_span.contains(mr), "Should clear within span"); // _whole_span ??
|
|
7026 // XXX When _finger crosses from old gen into perm gen
|
|
7027 // we may be doing unnecessary cleaning; do better in the
|
|
7028 // future by detecting that condition and clearing fewer
|
|
7029 // MUT/CT entries.
|
|
7030 _mut->clear_range(mr);
|
|
7031 }
|
|
7032
|
|
7033 // Note: the local finger doesn't advance while we drain
|
|
7034 // the stack below, but the global finger sure can and will.
|
|
7035 HeapWord** gfa = _task->global_finger_addr();
|
|
7036 Par_PushOrMarkClosure pushOrMarkClosure(_collector,
|
|
7037 _span, _bit_map,
|
|
7038 _work_queue,
|
|
7039 _overflow_stack,
|
|
7040 _revisit_stack,
|
|
7041 _finger,
|
|
7042 gfa, this);
|
|
7043 bool res = _work_queue->push(this_oop); // overflow could occur here
|
|
7044 assert(res, "Will hold once we use workqueues");
|
|
7045 while (true) {
|
|
7046 oop new_oop;
|
|
7047 if (!_work_queue->pop_local(new_oop)) {
|
|
7048 // We emptied our work_queue; check if there's stuff that can
|
|
7049 // be gotten from the overflow stack.
|
|
7050 if (CMSConcMarkingTask::get_work_from_overflow_stack(
|
|
7051 _overflow_stack, _work_queue)) {
|
|
7052 do_yield_check();
|
|
7053 continue;
|
|
7054 } else { // done
|
|
7055 break;
|
|
7056 }
|
|
7057 }
|
|
7058 // Skip verifying header mark word below because we are
|
|
7059 // running concurrent with mutators.
|
|
7060 assert(new_oop->is_oop(true), "Oops! expected to pop an oop");
|
|
7061 // now scan this oop's oops
|
|
7062 new_oop->oop_iterate(&pushOrMarkClosure);
|
|
7063 do_yield_check();
|
|
7064 }
|
|
7065 assert(_work_queue->size() == 0, "tautology, emphasizing post-condition");
|
|
7066 }
|
|
7067
|
|
7068 // Yield in response to a request from VM Thread or
|
|
7069 // from mutators.
|
|
7070 void Par_MarkFromRootsClosure::do_yield_work() {
|
|
7071 assert(_task != NULL, "sanity");
|
|
7072 _task->yield();
|
|
7073 }
|
|
7074
|
|
7075 // A variant of the above used for verifying CMS marking work.
|
|
7076 MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector,
|
|
7077 MemRegion span,
|
|
7078 CMSBitMap* verification_bm, CMSBitMap* cms_bm,
|
|
7079 CMSMarkStack* mark_stack):
|
|
7080 _collector(collector),
|
|
7081 _span(span),
|
|
7082 _verification_bm(verification_bm),
|
|
7083 _cms_bm(cms_bm),
|
|
7084 _mark_stack(mark_stack),
|
|
7085 _pam_verify_closure(collector, span, verification_bm, cms_bm,
|
|
7086 mark_stack)
|
|
7087 {
|
|
7088 assert(_mark_stack->isEmpty(), "stack should be empty");
|
|
7089 _finger = _verification_bm->startWord();
|
|
7090 assert(_collector->_restart_addr == NULL, "Sanity check");
|
|
7091 assert(_span.contains(_finger), "Out of bounds _finger?");
|
|
7092 }
|
|
7093
|
|
7094 void MarkFromRootsVerifyClosure::reset(HeapWord* addr) {
|
|
7095 assert(_mark_stack->isEmpty(), "would cause duplicates on stack");
|
|
7096 assert(_span.contains(addr), "Out of bounds _finger?");
|
|
7097 _finger = addr;
|
|
7098 }
|
|
7099
|
|
7100 // Should revisit to see if this should be restructured for
|
|
7101 // greater efficiency.
|
|
7102 void MarkFromRootsVerifyClosure::do_bit(size_t offset) {
|
|
7103 // convert offset into a HeapWord*
|
|
7104 HeapWord* addr = _verification_bm->startWord() + offset;
|
|
7105 assert(_verification_bm->endWord() && addr < _verification_bm->endWord(),
|
|
7106 "address out of range");
|
|
7107 assert(_verification_bm->isMarked(addr), "tautology");
|
|
7108 assert(_cms_bm->isMarked(addr), "tautology");
|
|
7109
|
|
7110 assert(_mark_stack->isEmpty(),
|
|
7111 "should drain stack to limit stack usage");
|
|
7112 // convert addr to an oop preparatory to scanning
|
|
7113 oop this_oop = oop(addr);
|
|
7114 assert(this_oop->is_oop(), "should be an oop");
|
|
7115 assert(_finger <= addr, "_finger runneth ahead");
|
|
7116 // advance the finger to right end of this object
|
|
7117 _finger = addr + this_oop->size();
|
|
7118 assert(_finger > addr, "we just incremented it above");
|
|
7119 // Note: the finger doesn't advance while we drain
|
|
7120 // the stack below.
|
|
7121 bool res = _mark_stack->push(this_oop);
|
|
7122 assert(res, "Empty non-zero size stack should have space for single push");
|
|
7123 while (!_mark_stack->isEmpty()) {
|
|
7124 oop new_oop = _mark_stack->pop();
|
|
7125 assert(new_oop->is_oop(), "Oops! expected to pop an oop");
|
|
7126 // now scan this oop's oops
|
|
7127 new_oop->oop_iterate(&_pam_verify_closure);
|
|
7128 }
|
|
7129 assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition");
|
|
7130 }
|
|
7131
|
|
7132 PushAndMarkVerifyClosure::PushAndMarkVerifyClosure(
|
|
7133 CMSCollector* collector, MemRegion span,
|
|
7134 CMSBitMap* verification_bm, CMSBitMap* cms_bm,
|
|
7135 CMSMarkStack* mark_stack):
|
|
7136 OopClosure(collector->ref_processor()),
|
|
7137 _collector(collector),
|
|
7138 _span(span),
|
|
7139 _verification_bm(verification_bm),
|
|
7140 _cms_bm(cms_bm),
|
|
7141 _mark_stack(mark_stack)
|
|
7142 { }
|
|
7143
|
|
7144
|
|
7145 // Upon stack overflow, we discard (part of) the stack,
|
|
7146 // remembering the least address amongst those discarded
|
|
7147 // in CMSCollector's _restart_address.
|
|
7148 void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) {
|
|
7149 // Remember the least grey address discarded
|
|
7150 HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost);
|
|
7151 _collector->lower_restart_addr(ra);
|
|
7152 _mark_stack->reset(); // discard stack contents
|
|
7153 _mark_stack->expand(); // expand the stack if possible
|
|
7154 }
|
|
7155
|
|
7156 void PushAndMarkVerifyClosure::do_oop(oop* p) {
|
|
7157 oop this_oop = *p;
|
|
7158 assert(this_oop->is_oop_or_null(), "expected an oop or NULL");
|
|
7159 HeapWord* addr = (HeapWord*)this_oop;
|
|
7160 if (_span.contains(addr) && !_verification_bm->isMarked(addr)) {
|
|
7161 // Oop lies in _span and isn't yet grey or black
|
|
7162 _verification_bm->mark(addr); // now grey
|
|
7163 if (!_cms_bm->isMarked(addr)) {
|
|
7164 oop(addr)->print();
|
|
7165 gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr);
|
|
7166 fatal("... aborting");
|
|
7167 }
|
|
7168
|
|
7169 if (!_mark_stack->push(this_oop)) { // stack overflow
|
|
7170 if (PrintCMSStatistics != 0) {
|
|
7171 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at "
|
|
7172 SIZE_FORMAT, _mark_stack->capacity());
|
|
7173 }
|
|
7174 assert(_mark_stack->isFull(), "Else push should have succeeded");
|
|
7175 handle_stack_overflow(addr);
|
|
7176 }
|
|
7177 // anything including and to the right of _finger
|
|
7178 // will be scanned as we iterate over the remainder of the
|
|
7179 // bit map
|
|
7180 }
|
|
7181 }
|
|
7182
|
|
7183 PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector,
|
|
7184 MemRegion span,
|
|
7185 CMSBitMap* bitMap, CMSMarkStack* markStack,
|
|
7186 CMSMarkStack* revisitStack,
|
|
7187 HeapWord* finger, MarkFromRootsClosure* parent) :
|
|
7188 OopClosure(collector->ref_processor()),
|
|
7189 _collector(collector),
|
|
7190 _span(span),
|
|
7191 _bitMap(bitMap),
|
|
7192 _markStack(markStack),
|
|
7193 _revisitStack(revisitStack),
|
|
7194 _finger(finger),
|
|
7195 _parent(parent),
|
|
7196 _should_remember_klasses(collector->cms_should_unload_classes())
|
|
7197 { }
|
|
7198
|
|
7199 Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector,
|
|
7200 MemRegion span,
|
|
7201 CMSBitMap* bit_map,
|
|
7202 OopTaskQueue* work_queue,
|
|
7203 CMSMarkStack* overflow_stack,
|
|
7204 CMSMarkStack* revisit_stack,
|
|
7205 HeapWord* finger,
|
|
7206 HeapWord** global_finger_addr,
|
|
7207 Par_MarkFromRootsClosure* parent) :
|
|
7208 OopClosure(collector->ref_processor()),
|
|
7209 _collector(collector),
|
|
7210 _whole_span(collector->_span),
|
|
7211 _span(span),
|
|
7212 _bit_map(bit_map),
|
|
7213 _work_queue(work_queue),
|
|
7214 _overflow_stack(overflow_stack),
|
|
7215 _revisit_stack(revisit_stack),
|
|
7216 _finger(finger),
|
|
7217 _global_finger_addr(global_finger_addr),
|
|
7218 _parent(parent),
|
|
7219 _should_remember_klasses(collector->cms_should_unload_classes())
|
|
7220 { }
|
|
7221
|
|
7222
|
|
7223 void CMSCollector::lower_restart_addr(HeapWord* low) {
|
|
7224 assert(_span.contains(low), "Out of bounds addr");
|
|
7225 if (_restart_addr == NULL) {
|
|
7226 _restart_addr = low;
|
|
7227 } else {
|
|
7228 _restart_addr = MIN2(_restart_addr, low);
|
|
7229 }
|
|
7230 }
|
|
7231
|
|
7232 // Upon stack overflow, we discard (part of) the stack,
|
|
7233 // remembering the least address amongst those discarded
|
|
7234 // in CMSCollector's _restart_address.
|
|
7235 void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) {
|
|
7236 // Remember the least grey address discarded
|
|
7237 HeapWord* ra = (HeapWord*)_markStack->least_value(lost);
|
|
7238 _collector->lower_restart_addr(ra);
|
|
7239 _markStack->reset(); // discard stack contents
|
|
7240 _markStack->expand(); // expand the stack if possible
|
|
7241 }
|
|
7242
|
|
7243 // Upon stack overflow, we discard (part of) the stack,
|
|
7244 // remembering the least address amongst those discarded
|
|
7245 // in CMSCollector's _restart_address.
|
|
7246 void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) {
|
|
7247 // We need to do this under a mutex to prevent other
|
|
7248 // workers from interfering with the expansion below.
|
|
7249 MutexLockerEx ml(_overflow_stack->par_lock(),
|
|
7250 Mutex::_no_safepoint_check_flag);
|
|
7251 // Remember the least grey address discarded
|
|
7252 HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost);
|
|
7253 _collector->lower_restart_addr(ra);
|
|
7254 _overflow_stack->reset(); // discard stack contents
|
|
7255 _overflow_stack->expand(); // expand the stack if possible
|
|
7256 }
|
|
7257
|
|
7258
|
|
7259 void PushOrMarkClosure::do_oop(oop* p) {
|
|
7260 oop thisOop = *p;
|
|
7261 // Ignore mark word because we are running concurrent with mutators.
|
|
7262 assert(thisOop->is_oop_or_null(true), "expected an oop or NULL");
|
|
7263 HeapWord* addr = (HeapWord*)thisOop;
|
|
7264 if (_span.contains(addr) && !_bitMap->isMarked(addr)) {
|
|
7265 // Oop lies in _span and isn't yet grey or black
|
|
7266 _bitMap->mark(addr); // now grey
|
|
7267 if (addr < _finger) {
|
|
7268 // the bit map iteration has already either passed, or
|
|
7269 // sampled, this bit in the bit map; we'll need to
|
|
7270 // use the marking stack to scan this oop's oops.
|
|
7271 bool simulate_overflow = false;
|
|
7272 NOT_PRODUCT(
|
|
7273 if (CMSMarkStackOverflowALot &&
|
|
7274 _collector->simulate_overflow()) {
|
|
7275 // simulate a stack overflow
|
|
7276 simulate_overflow = true;
|
|
7277 }
|
|
7278 )
|
|
7279 if (simulate_overflow || !_markStack->push(thisOop)) { // stack overflow
|
|
7280 if (PrintCMSStatistics != 0) {
|
|
7281 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at "
|
|
7282 SIZE_FORMAT, _markStack->capacity());
|
|
7283 }
|
|
7284 assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded");
|
|
7285 handle_stack_overflow(addr);
|
|
7286 }
|
|
7287 }
|
|
7288 // anything including and to the right of _finger
|
|
7289 // will be scanned as we iterate over the remainder of the
|
|
7290 // bit map
|
|
7291 do_yield_check();
|
|
7292 }
|
|
7293 }
|
|
7294
|
|
7295 void Par_PushOrMarkClosure::do_oop(oop* p) {
|
|
7296 oop this_oop = *p;
|
|
7297 // Ignore mark word because we are running concurrent with mutators.
|
|
7298 assert(this_oop->is_oop_or_null(true), "expected an oop or NULL");
|
|
7299 HeapWord* addr = (HeapWord*)this_oop;
|
|
7300 if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) {
|
|
7301 // Oop lies in _span and isn't yet grey or black
|
|
7302 // We read the global_finger (volatile read) strictly after marking oop
|
|
7303 bool res = _bit_map->par_mark(addr); // now grey
|
|
7304 volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr;
|
|
7305 // Should we push this marked oop on our stack?
|
|
7306 // -- if someone else marked it, nothing to do
|
|
7307 // -- if target oop is above global finger nothing to do
|
|
7308 // -- if target oop is in chunk and above local finger
|
|
7309 // then nothing to do
|
|
7310 // -- else push on work queue
|
|
7311 if ( !res // someone else marked it, they will deal with it
|
|
7312 || (addr >= *gfa) // will be scanned in a later task
|
|
7313 || (_span.contains(addr) && addr >= _finger)) { // later in this chunk
|
|
7314 return;
|
|
7315 }
|
|
7316 // the bit map iteration has already either passed, or
|
|
7317 // sampled, this bit in the bit map; we'll need to
|
|
7318 // use the marking stack to scan this oop's oops.
|
|
7319 bool simulate_overflow = false;
|
|
7320 NOT_PRODUCT(
|
|
7321 if (CMSMarkStackOverflowALot &&
|
|
7322 _collector->simulate_overflow()) {
|
|
7323 // simulate a stack overflow
|
|
7324 simulate_overflow = true;
|
|
7325 }
|
|
7326 )
|
|
7327 if (simulate_overflow ||
|
|
7328 !(_work_queue->push(this_oop) || _overflow_stack->par_push(this_oop))) {
|
|
7329 // stack overflow
|
|
7330 if (PrintCMSStatistics != 0) {
|
|
7331 gclog_or_tty->print_cr("CMS marking stack overflow (benign) at "
|
|
7332 SIZE_FORMAT, _overflow_stack->capacity());
|
|
7333 }
|
|
7334 // We cannot assert that the overflow stack is full because
|
|
7335 // it may have been emptied since.
|
|
7336 assert(simulate_overflow ||
|
|
7337 _work_queue->size() == _work_queue->max_elems(),
|
|
7338 "Else push should have succeeded");
|
|
7339 handle_stack_overflow(addr);
|
|
7340 }
|
|
7341 do_yield_check();
|
|
7342 }
|
|
7343 }
|
|
7344
|
|
7345
|
|
7346 PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector,
|
|
7347 MemRegion span,
|
|
7348 ReferenceProcessor* rp,
|
|
7349 CMSBitMap* bit_map,
|
|
7350 CMSBitMap* mod_union_table,
|
|
7351 CMSMarkStack* mark_stack,
|
|
7352 CMSMarkStack* revisit_stack,
|
|
7353 bool concurrent_precleaning):
|
|
7354 OopClosure(rp),
|
|
7355 _collector(collector),
|
|
7356 _span(span),
|
|
7357 _bit_map(bit_map),
|
|
7358 _mod_union_table(mod_union_table),
|
|
7359 _mark_stack(mark_stack),
|
|
7360 _revisit_stack(revisit_stack),
|
|
7361 _concurrent_precleaning(concurrent_precleaning),
|
|
7362 _should_remember_klasses(collector->cms_should_unload_classes())
|
|
7363 {
|
|
7364 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL");
|
|
7365 }
|
|
7366
|
|
7367 // Grey object rescan during pre-cleaning and second checkpoint phases --
|
|
7368 // the non-parallel version (the parallel version appears further below.)
|
|
7369 void PushAndMarkClosure::do_oop(oop* p) {
|
|
7370 oop this_oop = *p;
|
|
7371 // Ignore mark word verification. If during concurrent precleaning
|
|
7372 // the object monitor may be locked. If during the checkpoint
|
|
7373 // phases, the object may already have been reached by a different
|
|
7374 // path and may be at the end of the global overflow list (so
|
|
7375 // the mark word may be NULL).
|
|
7376 assert(this_oop->is_oop_or_null(true/* ignore mark word */),
|
|
7377 "expected an oop or NULL");
|
|
7378 HeapWord* addr = (HeapWord*)this_oop;
|
|
7379 // Check if oop points into the CMS generation
|
|
7380 // and is not marked
|
|
7381 if (_span.contains(addr) && !_bit_map->isMarked(addr)) {
|
|
7382 // a white object ...
|
|
7383 _bit_map->mark(addr); // ... now grey
|
|
7384 // push on the marking stack (grey set)
|
|
7385 bool simulate_overflow = false;
|
|
7386 NOT_PRODUCT(
|
|
7387 if (CMSMarkStackOverflowALot &&
|
|
7388 _collector->simulate_overflow()) {
|
|
7389 // simulate a stack overflow
|
|
7390 simulate_overflow = true;
|
|
7391 }
|
|
7392 )
|
|
7393 if (simulate_overflow || !_mark_stack->push(this_oop)) {
|
|
7394 if (_concurrent_precleaning) {
|
|
7395 // During precleaning we can just dirty the appropriate card
|
|
7396 // in the mod union table, thus ensuring that the object remains
|
|
7397 // in the grey set and continue. Note that no one can be intefering
|
|
7398 // with us in this action of dirtying the mod union table, so
|
|
7399 // no locking is required.
|
|
7400 _mod_union_table->mark(addr);
|
|
7401 _collector->_ser_pmc_preclean_ovflw++;
|
|
7402 } else {
|
|
7403 // During the remark phase, we need to remember this oop
|
|
7404 // in the overflow list.
|
|
7405 _collector->push_on_overflow_list(this_oop);
|
|
7406 _collector->_ser_pmc_remark_ovflw++;
|
|
7407 }
|
|
7408 }
|
|
7409 }
|
|
7410 }
|
|
7411
|
|
7412 Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector,
|
|
7413 MemRegion span,
|
|
7414 ReferenceProcessor* rp,
|
|
7415 CMSBitMap* bit_map,
|
|
7416 OopTaskQueue* work_queue,
|
|
7417 CMSMarkStack* revisit_stack):
|
|
7418 OopClosure(rp),
|
|
7419 _collector(collector),
|
|
7420 _span(span),
|
|
7421 _bit_map(bit_map),
|
|
7422 _work_queue(work_queue),
|
|
7423 _revisit_stack(revisit_stack),
|
|
7424 _should_remember_klasses(collector->cms_should_unload_classes())
|
|
7425 {
|
|
7426 assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL");
|
|
7427 }
|
|
7428
|
|
7429 // Grey object rescan during second checkpoint phase --
|
|
7430 // the parallel version.
|
|
7431 void Par_PushAndMarkClosure::do_oop(oop* p) {
|
|
7432 oop this_oop = *p;
|
|
7433 // In the assert below, we ignore the mark word because
|
|
7434 // this oop may point to an already visited object that is
|
|
7435 // on the overflow stack (in which case the mark word has
|
|
7436 // been hijacked for chaining into the overflow stack --
|
|
7437 // if this is the last object in the overflow stack then
|
|
7438 // its mark word will be NULL). Because this object may
|
|
7439 // have been subsequently popped off the global overflow
|
|
7440 // stack, and the mark word possibly restored to the prototypical
|
|
7441 // value, by the time we get to examined this failing assert in
|
|
7442 // the debugger, is_oop_or_null(false) may subsequently start
|
|
7443 // to hold.
|
|
7444 assert(this_oop->is_oop_or_null(true),
|
|
7445 "expected an oop or NULL");
|
|
7446 HeapWord* addr = (HeapWord*)this_oop;
|
|
7447 // Check if oop points into the CMS generation
|
|
7448 // and is not marked
|
|
7449 if (_span.contains(addr) && !_bit_map->isMarked(addr)) {
|
|
7450 // a white object ...
|
|
7451 // If we manage to "claim" the object, by being the
|
|
7452 // first thread to mark it, then we push it on our
|
|
7453 // marking stack
|
|
7454 if (_bit_map->par_mark(addr)) { // ... now grey
|
|
7455 // push on work queue (grey set)
|
|
7456 bool simulate_overflow = false;
|
|
7457 NOT_PRODUCT(
|
|
7458 if (CMSMarkStackOverflowALot &&
|
|
7459 _collector->par_simulate_overflow()) {
|
|
7460 // simulate a stack overflow
|
|
7461 simulate_overflow = true;
|
|
7462 }
|
|
7463 )
|
|
7464 if (simulate_overflow || !_work_queue->push(this_oop)) {
|
|
7465 _collector->par_push_on_overflow_list(this_oop);
|
|
7466 _collector->_par_pmc_remark_ovflw++; // imprecise OK: no need to CAS
|
|
7467 }
|
|
7468 } // Else, some other thread got there first
|
|
7469 }
|
|
7470 }
|
|
7471
|
|
7472 void PushAndMarkClosure::remember_klass(Klass* k) {
|
|
7473 if (!_revisit_stack->push(oop(k))) {
|
|
7474 fatal("Revisit stack overflowed in PushAndMarkClosure");
|
|
7475 }
|
|
7476 }
|
|
7477
|
|
7478 void Par_PushAndMarkClosure::remember_klass(Klass* k) {
|
|
7479 if (!_revisit_stack->par_push(oop(k))) {
|
|
7480 fatal("Revist stack overflowed in Par_PushAndMarkClosure");
|
|
7481 }
|
|
7482 }
|
|
7483
|
|
7484 void CMSPrecleanRefsYieldClosure::do_yield_work() {
|
|
7485 Mutex* bml = _collector->bitMapLock();
|
|
7486 assert_lock_strong(bml);
|
|
7487 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
7488 "CMS thread should hold CMS token");
|
|
7489
|
|
7490 bml->unlock();
|
|
7491 ConcurrentMarkSweepThread::desynchronize(true);
|
|
7492
|
|
7493 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
7494
|
|
7495 _collector->stopTimer();
|
|
7496 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
|
|
7497 if (PrintCMSStatistics != 0) {
|
|
7498 _collector->incrementYields();
|
|
7499 }
|
|
7500 _collector->icms_wait();
|
|
7501
|
|
7502 // See the comment in coordinator_yield()
|
|
7503 for (unsigned i = 0; i < CMSYieldSleepCount &&
|
|
7504 ConcurrentMarkSweepThread::should_yield() &&
|
|
7505 !CMSCollector::foregroundGCIsActive(); ++i) {
|
|
7506 os::sleep(Thread::current(), 1, false);
|
|
7507 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
7508 }
|
|
7509
|
|
7510 ConcurrentMarkSweepThread::synchronize(true);
|
|
7511 bml->lock();
|
|
7512
|
|
7513 _collector->startTimer();
|
|
7514 }
|
|
7515
|
|
7516 bool CMSPrecleanRefsYieldClosure::should_return() {
|
|
7517 if (ConcurrentMarkSweepThread::should_yield()) {
|
|
7518 do_yield_work();
|
|
7519 }
|
|
7520 return _collector->foregroundGCIsActive();
|
|
7521 }
|
|
7522
|
|
7523 void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) {
|
|
7524 assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0,
|
|
7525 "mr should be aligned to start at a card boundary");
|
|
7526 // We'd like to assert:
|
|
7527 // assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0,
|
|
7528 // "mr should be a range of cards");
|
|
7529 // However, that would be too strong in one case -- the last
|
|
7530 // partition ends at _unallocated_block which, in general, can be
|
|
7531 // an arbitrary boundary, not necessarily card aligned.
|
|
7532 if (PrintCMSStatistics != 0) {
|
|
7533 _num_dirty_cards +=
|
|
7534 mr.word_size()/CardTableModRefBS::card_size_in_words;
|
|
7535 }
|
|
7536 _space->object_iterate_mem(mr, &_scan_cl);
|
|
7537 }
|
|
7538
|
|
7539 SweepClosure::SweepClosure(CMSCollector* collector,
|
|
7540 ConcurrentMarkSweepGeneration* g,
|
|
7541 CMSBitMap* bitMap, bool should_yield) :
|
|
7542 _collector(collector),
|
|
7543 _g(g),
|
|
7544 _sp(g->cmsSpace()),
|
|
7545 _limit(_sp->sweep_limit()),
|
|
7546 _freelistLock(_sp->freelistLock()),
|
|
7547 _bitMap(bitMap),
|
|
7548 _yield(should_yield),
|
|
7549 _inFreeRange(false), // No free range at beginning of sweep
|
|
7550 _freeRangeInFreeLists(false), // No free range at beginning of sweep
|
|
7551 _lastFreeRangeCoalesced(false),
|
|
7552 _freeFinger(g->used_region().start())
|
|
7553 {
|
|
7554 NOT_PRODUCT(
|
|
7555 _numObjectsFreed = 0;
|
|
7556 _numWordsFreed = 0;
|
|
7557 _numObjectsLive = 0;
|
|
7558 _numWordsLive = 0;
|
|
7559 _numObjectsAlreadyFree = 0;
|
|
7560 _numWordsAlreadyFree = 0;
|
|
7561 _last_fc = NULL;
|
|
7562
|
|
7563 _sp->initializeIndexedFreeListArrayReturnedBytes();
|
|
7564 _sp->dictionary()->initializeDictReturnedBytes();
|
|
7565 )
|
|
7566 assert(_limit >= _sp->bottom() && _limit <= _sp->end(),
|
|
7567 "sweep _limit out of bounds");
|
|
7568 if (CMSTraceSweeper) {
|
|
7569 gclog_or_tty->print("\n====================\nStarting new sweep\n");
|
|
7570 }
|
|
7571 }
|
|
7572
|
|
7573 // We need this destructor to reclaim any space at the end
|
|
7574 // of the space, which do_blk below may not have added back to
|
|
7575 // the free lists. [basically dealing with the "fringe effect"]
|
|
7576 SweepClosure::~SweepClosure() {
|
|
7577 assert_lock_strong(_freelistLock);
|
|
7578 // this should be treated as the end of a free run if any
|
|
7579 // The current free range should be returned to the free lists
|
|
7580 // as one coalesced chunk.
|
|
7581 if (inFreeRange()) {
|
|
7582 flushCurFreeChunk(freeFinger(),
|
|
7583 pointer_delta(_limit, freeFinger()));
|
|
7584 assert(freeFinger() < _limit, "the finger pointeth off base");
|
|
7585 if (CMSTraceSweeper) {
|
|
7586 gclog_or_tty->print("destructor:");
|
|
7587 gclog_or_tty->print("Sweep:put_free_blk 0x%x ("SIZE_FORMAT") "
|
|
7588 "[coalesced:"SIZE_FORMAT"]\n",
|
|
7589 freeFinger(), pointer_delta(_limit, freeFinger()),
|
|
7590 lastFreeRangeCoalesced());
|
|
7591 }
|
|
7592 }
|
|
7593 NOT_PRODUCT(
|
|
7594 if (Verbose && PrintGC) {
|
|
7595 gclog_or_tty->print("Collected "SIZE_FORMAT" objects, "
|
|
7596 SIZE_FORMAT " bytes",
|
|
7597 _numObjectsFreed, _numWordsFreed*sizeof(HeapWord));
|
|
7598 gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects, "
|
|
7599 SIZE_FORMAT" bytes "
|
|
7600 "Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes",
|
|
7601 _numObjectsLive, _numWordsLive*sizeof(HeapWord),
|
|
7602 _numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord));
|
|
7603 size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) *
|
|
7604 sizeof(HeapWord);
|
|
7605 gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes);
|
|
7606
|
|
7607 if (PrintCMSStatistics && CMSVerifyReturnedBytes) {
|
|
7608 size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes();
|
|
7609 size_t dictReturnedBytes = _sp->dictionary()->sumDictReturnedBytes();
|
|
7610 size_t returnedBytes = indexListReturnedBytes + dictReturnedBytes;
|
|
7611 gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returnedBytes);
|
|
7612 gclog_or_tty->print(" Indexed List Returned "SIZE_FORMAT" bytes",
|
|
7613 indexListReturnedBytes);
|
|
7614 gclog_or_tty->print_cr(" Dictionary Returned "SIZE_FORMAT" bytes",
|
|
7615 dictReturnedBytes);
|
|
7616 }
|
|
7617 }
|
|
7618 )
|
|
7619 // Now, in debug mode, just null out the sweep_limit
|
|
7620 NOT_PRODUCT(_sp->clear_sweep_limit();)
|
|
7621 if (CMSTraceSweeper) {
|
|
7622 gclog_or_tty->print("end of sweep\n================\n");
|
|
7623 }
|
|
7624 }
|
|
7625
|
|
7626 void SweepClosure::initialize_free_range(HeapWord* freeFinger,
|
|
7627 bool freeRangeInFreeLists) {
|
|
7628 if (CMSTraceSweeper) {
|
|
7629 gclog_or_tty->print("---- Start free range 0x%x with free block [%d] (%d)\n",
|
|
7630 freeFinger, _sp->block_size(freeFinger),
|
|
7631 freeRangeInFreeLists);
|
|
7632 }
|
|
7633 assert(!inFreeRange(), "Trampling existing free range");
|
|
7634 set_inFreeRange(true);
|
|
7635 set_lastFreeRangeCoalesced(false);
|
|
7636
|
|
7637 set_freeFinger(freeFinger);
|
|
7638 set_freeRangeInFreeLists(freeRangeInFreeLists);
|
|
7639 if (CMSTestInFreeList) {
|
|
7640 if (freeRangeInFreeLists) {
|
|
7641 FreeChunk* fc = (FreeChunk*) freeFinger;
|
|
7642 assert(fc->isFree(), "A chunk on the free list should be free.");
|
|
7643 assert(fc->size() > 0, "Free range should have a size");
|
|
7644 assert(_sp->verifyChunkInFreeLists(fc), "Chunk is not in free lists");
|
|
7645 }
|
|
7646 }
|
|
7647 }
|
|
7648
|
|
7649 // Note that the sweeper runs concurrently with mutators. Thus,
|
|
7650 // it is possible for direct allocation in this generation to happen
|
|
7651 // in the middle of the sweep. Note that the sweeper also coalesces
|
|
7652 // contiguous free blocks. Thus, unless the sweeper and the allocator
|
|
7653 // synchronize appropriately freshly allocated blocks may get swept up.
|
|
7654 // This is accomplished by the sweeper locking the free lists while
|
|
7655 // it is sweeping. Thus blocks that are determined to be free are
|
|
7656 // indeed free. There is however one additional complication:
|
|
7657 // blocks that have been allocated since the final checkpoint and
|
|
7658 // mark, will not have been marked and so would be treated as
|
|
7659 // unreachable and swept up. To prevent this, the allocator marks
|
|
7660 // the bit map when allocating during the sweep phase. This leads,
|
|
7661 // however, to a further complication -- objects may have been allocated
|
|
7662 // but not yet initialized -- in the sense that the header isn't yet
|
|
7663 // installed. The sweeper can not then determine the size of the block
|
|
7664 // in order to skip over it. To deal with this case, we use a technique
|
|
7665 // (due to Printezis) to encode such uninitialized block sizes in the
|
|
7666 // bit map. Since the bit map uses a bit per every HeapWord, but the
|
|
7667 // CMS generation has a minimum object size of 3 HeapWords, it follows
|
|
7668 // that "normal marks" won't be adjacent in the bit map (there will
|
|
7669 // always be at least two 0 bits between successive 1 bits). We make use
|
|
7670 // of these "unused" bits to represent uninitialized blocks -- the bit
|
|
7671 // corresponding to the start of the uninitialized object and the next
|
|
7672 // bit are both set. Finally, a 1 bit marks the end of the object that
|
|
7673 // started with the two consecutive 1 bits to indicate its potentially
|
|
7674 // uninitialized state.
|
|
7675
|
|
7676 size_t SweepClosure::do_blk_careful(HeapWord* addr) {
|
|
7677 FreeChunk* fc = (FreeChunk*)addr;
|
|
7678 size_t res;
|
|
7679
|
|
7680 // check if we are done sweepinrg
|
|
7681 if (addr == _limit) { // we have swept up to the limit, do nothing more
|
|
7682 assert(_limit >= _sp->bottom() && _limit <= _sp->end(),
|
|
7683 "sweep _limit out of bounds");
|
|
7684 // help the closure application finish
|
|
7685 return pointer_delta(_sp->end(), _limit);
|
|
7686 }
|
|
7687 assert(addr <= _limit, "sweep invariant");
|
|
7688
|
|
7689 // check if we should yield
|
|
7690 do_yield_check(addr);
|
|
7691 if (fc->isFree()) {
|
|
7692 // Chunk that is already free
|
|
7693 res = fc->size();
|
|
7694 doAlreadyFreeChunk(fc);
|
|
7695 debug_only(_sp->verifyFreeLists());
|
|
7696 assert(res == fc->size(), "Don't expect the size to change");
|
|
7697 NOT_PRODUCT(
|
|
7698 _numObjectsAlreadyFree++;
|
|
7699 _numWordsAlreadyFree += res;
|
|
7700 )
|
|
7701 NOT_PRODUCT(_last_fc = fc;)
|
|
7702 } else if (!_bitMap->isMarked(addr)) {
|
|
7703 // Chunk is fresh garbage
|
|
7704 res = doGarbageChunk(fc);
|
|
7705 debug_only(_sp->verifyFreeLists());
|
|
7706 NOT_PRODUCT(
|
|
7707 _numObjectsFreed++;
|
|
7708 _numWordsFreed += res;
|
|
7709 )
|
|
7710 } else {
|
|
7711 // Chunk that is alive.
|
|
7712 res = doLiveChunk(fc);
|
|
7713 debug_only(_sp->verifyFreeLists());
|
|
7714 NOT_PRODUCT(
|
|
7715 _numObjectsLive++;
|
|
7716 _numWordsLive += res;
|
|
7717 )
|
|
7718 }
|
|
7719 return res;
|
|
7720 }
|
|
7721
|
|
7722 // For the smart allocation, record following
|
|
7723 // split deaths - a free chunk is removed from its free list because
|
|
7724 // it is being split into two or more chunks.
|
|
7725 // split birth - a free chunk is being added to its free list because
|
|
7726 // a larger free chunk has been split and resulted in this free chunk.
|
|
7727 // coal death - a free chunk is being removed from its free list because
|
|
7728 // it is being coalesced into a large free chunk.
|
|
7729 // coal birth - a free chunk is being added to its free list because
|
|
7730 // it was created when two or more free chunks where coalesced into
|
|
7731 // this free chunk.
|
|
7732 //
|
|
7733 // These statistics are used to determine the desired number of free
|
|
7734 // chunks of a given size. The desired number is chosen to be relative
|
|
7735 // to the end of a CMS sweep. The desired number at the end of a sweep
|
|
7736 // is the
|
|
7737 // count-at-end-of-previous-sweep (an amount that was enough)
|
|
7738 // - count-at-beginning-of-current-sweep (the excess)
|
|
7739 // + split-births (gains in this size during interval)
|
|
7740 // - split-deaths (demands on this size during interval)
|
|
7741 // where the interval is from the end of one sweep to the end of the
|
|
7742 // next.
|
|
7743 //
|
|
7744 // When sweeping the sweeper maintains an accumulated chunk which is
|
|
7745 // the chunk that is made up of chunks that have been coalesced. That
|
|
7746 // will be termed the left-hand chunk. A new chunk of garbage that
|
|
7747 // is being considered for coalescing will be referred to as the
|
|
7748 // right-hand chunk.
|
|
7749 //
|
|
7750 // When making a decision on whether to coalesce a right-hand chunk with
|
|
7751 // the current left-hand chunk, the current count vs. the desired count
|
|
7752 // of the left-hand chunk is considered. Also if the right-hand chunk
|
|
7753 // is near the large chunk at the end of the heap (see
|
|
7754 // ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the
|
|
7755 // left-hand chunk is coalesced.
|
|
7756 //
|
|
7757 // When making a decision about whether to split a chunk, the desired count
|
|
7758 // vs. the current count of the candidate to be split is also considered.
|
|
7759 // If the candidate is underpopulated (currently fewer chunks than desired)
|
|
7760 // a chunk of an overpopulated (currently more chunks than desired) size may
|
|
7761 // be chosen. The "hint" associated with a free list, if non-null, points
|
|
7762 // to a free list which may be overpopulated.
|
|
7763 //
|
|
7764
|
|
7765 void SweepClosure::doAlreadyFreeChunk(FreeChunk* fc) {
|
|
7766 size_t size = fc->size();
|
|
7767 // Chunks that cannot be coalesced are not in the
|
|
7768 // free lists.
|
|
7769 if (CMSTestInFreeList && !fc->cantCoalesce()) {
|
|
7770 assert(_sp->verifyChunkInFreeLists(fc),
|
|
7771 "free chunk should be in free lists");
|
|
7772 }
|
|
7773 // a chunk that is already free, should not have been
|
|
7774 // marked in the bit map
|
|
7775 HeapWord* addr = (HeapWord*) fc;
|
|
7776 assert(!_bitMap->isMarked(addr), "free chunk should be unmarked");
|
|
7777 // Verify that the bit map has no bits marked between
|
|
7778 // addr and purported end of this block.
|
|
7779 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size);
|
|
7780
|
|
7781 // Some chunks cannot be coalesced in under any circumstances.
|
|
7782 // See the definition of cantCoalesce().
|
|
7783 if (!fc->cantCoalesce()) {
|
|
7784 // This chunk can potentially be coalesced.
|
|
7785 if (_sp->adaptive_freelists()) {
|
|
7786 // All the work is done in
|
|
7787 doPostIsFreeOrGarbageChunk(fc, size);
|
|
7788 } else { // Not adaptive free lists
|
|
7789 // this is a free chunk that can potentially be coalesced by the sweeper;
|
|
7790 if (!inFreeRange()) {
|
|
7791 // if the next chunk is a free block that can't be coalesced
|
|
7792 // it doesn't make sense to remove this chunk from the free lists
|
|
7793 FreeChunk* nextChunk = (FreeChunk*)(addr + size);
|
|
7794 assert((HeapWord*)nextChunk <= _limit, "sweep invariant");
|
|
7795 if ((HeapWord*)nextChunk < _limit && // there's a next chunk...
|
|
7796 nextChunk->isFree() && // which is free...
|
|
7797 nextChunk->cantCoalesce()) { // ... but cant be coalesced
|
|
7798 // nothing to do
|
|
7799 } else {
|
|
7800 // Potentially the start of a new free range:
|
|
7801 // Don't eagerly remove it from the free lists.
|
|
7802 // No need to remove it if it will just be put
|
|
7803 // back again. (Also from a pragmatic point of view
|
|
7804 // if it is a free block in a region that is beyond
|
|
7805 // any allocated blocks, an assertion will fail)
|
|
7806 // Remember the start of a free run.
|
|
7807 initialize_free_range(addr, true);
|
|
7808 // end - can coalesce with next chunk
|
|
7809 }
|
|
7810 } else {
|
|
7811 // the midst of a free range, we are coalescing
|
|
7812 debug_only(record_free_block_coalesced(fc);)
|
|
7813 if (CMSTraceSweeper) {
|
|
7814 gclog_or_tty->print(" -- pick up free block 0x%x (%d)\n", fc, size);
|
|
7815 }
|
|
7816 // remove it from the free lists
|
|
7817 _sp->removeFreeChunkFromFreeLists(fc);
|
|
7818 set_lastFreeRangeCoalesced(true);
|
|
7819 // If the chunk is being coalesced and the current free range is
|
|
7820 // in the free lists, remove the current free range so that it
|
|
7821 // will be returned to the free lists in its entirety - all
|
|
7822 // the coalesced pieces included.
|
|
7823 if (freeRangeInFreeLists()) {
|
|
7824 FreeChunk* ffc = (FreeChunk*) freeFinger();
|
|
7825 assert(ffc->size() == pointer_delta(addr, freeFinger()),
|
|
7826 "Size of free range is inconsistent with chunk size.");
|
|
7827 if (CMSTestInFreeList) {
|
|
7828 assert(_sp->verifyChunkInFreeLists(ffc),
|
|
7829 "free range is not in free lists");
|
|
7830 }
|
|
7831 _sp->removeFreeChunkFromFreeLists(ffc);
|
|
7832 set_freeRangeInFreeLists(false);
|
|
7833 }
|
|
7834 }
|
|
7835 }
|
|
7836 } else {
|
|
7837 // Code path common to both original and adaptive free lists.
|
|
7838
|
|
7839 // cant coalesce with previous block; this should be treated
|
|
7840 // as the end of a free run if any
|
|
7841 if (inFreeRange()) {
|
|
7842 // we kicked some butt; time to pick up the garbage
|
|
7843 assert(freeFinger() < addr, "the finger pointeth off base");
|
|
7844 flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger()));
|
|
7845 }
|
|
7846 // else, nothing to do, just continue
|
|
7847 }
|
|
7848 }
|
|
7849
|
|
7850 size_t SweepClosure::doGarbageChunk(FreeChunk* fc) {
|
|
7851 // This is a chunk of garbage. It is not in any free list.
|
|
7852 // Add it to a free list or let it possibly be coalesced into
|
|
7853 // a larger chunk.
|
|
7854 HeapWord* addr = (HeapWord*) fc;
|
|
7855 size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size());
|
|
7856
|
|
7857 if (_sp->adaptive_freelists()) {
|
|
7858 // Verify that the bit map has no bits marked between
|
|
7859 // addr and purported end of just dead object.
|
|
7860 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size);
|
|
7861
|
|
7862 doPostIsFreeOrGarbageChunk(fc, size);
|
|
7863 } else {
|
|
7864 if (!inFreeRange()) {
|
|
7865 // start of a new free range
|
|
7866 assert(size > 0, "A free range should have a size");
|
|
7867 initialize_free_range(addr, false);
|
|
7868
|
|
7869 } else {
|
|
7870 // this will be swept up when we hit the end of the
|
|
7871 // free range
|
|
7872 if (CMSTraceSweeper) {
|
|
7873 gclog_or_tty->print(" -- pick up garbage 0x%x (%d) \n", fc, size);
|
|
7874 }
|
|
7875 // If the chunk is being coalesced and the current free range is
|
|
7876 // in the free lists, remove the current free range so that it
|
|
7877 // will be returned to the free lists in its entirety - all
|
|
7878 // the coalesced pieces included.
|
|
7879 if (freeRangeInFreeLists()) {
|
|
7880 FreeChunk* ffc = (FreeChunk*)freeFinger();
|
|
7881 assert(ffc->size() == pointer_delta(addr, freeFinger()),
|
|
7882 "Size of free range is inconsistent with chunk size.");
|
|
7883 if (CMSTestInFreeList) {
|
|
7884 assert(_sp->verifyChunkInFreeLists(ffc),
|
|
7885 "free range is not in free lists");
|
|
7886 }
|
|
7887 _sp->removeFreeChunkFromFreeLists(ffc);
|
|
7888 set_freeRangeInFreeLists(false);
|
|
7889 }
|
|
7890 set_lastFreeRangeCoalesced(true);
|
|
7891 }
|
|
7892 // this will be swept up when we hit the end of the free range
|
|
7893
|
|
7894 // Verify that the bit map has no bits marked between
|
|
7895 // addr and purported end of just dead object.
|
|
7896 _bitMap->verifyNoOneBitsInRange(addr + 1, addr + size);
|
|
7897 }
|
|
7898 return size;
|
|
7899 }
|
|
7900
|
|
7901 size_t SweepClosure::doLiveChunk(FreeChunk* fc) {
|
|
7902 HeapWord* addr = (HeapWord*) fc;
|
|
7903 // The sweeper has just found a live object. Return any accumulated
|
|
7904 // left hand chunk to the free lists.
|
|
7905 if (inFreeRange()) {
|
|
7906 if (_sp->adaptive_freelists()) {
|
|
7907 flushCurFreeChunk(freeFinger(),
|
|
7908 pointer_delta(addr, freeFinger()));
|
|
7909 } else { // not adaptive freelists
|
|
7910 set_inFreeRange(false);
|
|
7911 // Add the free range back to the free list if it is not already
|
|
7912 // there.
|
|
7913 if (!freeRangeInFreeLists()) {
|
|
7914 assert(freeFinger() < addr, "the finger pointeth off base");
|
|
7915 if (CMSTraceSweeper) {
|
|
7916 gclog_or_tty->print("Sweep:put_free_blk 0x%x (%d) "
|
|
7917 "[coalesced:%d]\n",
|
|
7918 freeFinger(), pointer_delta(addr, freeFinger()),
|
|
7919 lastFreeRangeCoalesced());
|
|
7920 }
|
|
7921 _sp->addChunkAndRepairOffsetTable(freeFinger(),
|
|
7922 pointer_delta(addr, freeFinger()), lastFreeRangeCoalesced());
|
|
7923 }
|
|
7924 }
|
|
7925 }
|
|
7926
|
|
7927 // Common code path for original and adaptive free lists.
|
|
7928
|
|
7929 // this object is live: we'd normally expect this to be
|
|
7930 // an oop, and like to assert the following:
|
|
7931 // assert(oop(addr)->is_oop(), "live block should be an oop");
|
|
7932 // However, as we commented above, this may be an object whose
|
|
7933 // header hasn't yet been initialized.
|
|
7934 size_t size;
|
|
7935 assert(_bitMap->isMarked(addr), "Tautology for this control point");
|
|
7936 if (_bitMap->isMarked(addr + 1)) {
|
|
7937 // Determine the size from the bit map, rather than trying to
|
|
7938 // compute it from the object header.
|
|
7939 HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2);
|
|
7940 size = pointer_delta(nextOneAddr + 1, addr);
|
|
7941 assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
|
|
7942 "alignment problem");
|
|
7943
|
|
7944 #ifdef DEBUG
|
|
7945 if (oop(addr)->klass() != NULL &&
|
|
7946 ( !_collector->cms_should_unload_classes()
|
|
7947 || oop(addr)->is_parsable())) {
|
|
7948 // Ignore mark word because we are running concurrent with mutators
|
|
7949 assert(oop(addr)->is_oop(true), "live block should be an oop");
|
|
7950 assert(size ==
|
|
7951 CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()),
|
|
7952 "P-mark and computed size do not agree");
|
|
7953 }
|
|
7954 #endif
|
|
7955
|
|
7956 } else {
|
|
7957 // This should be an initialized object that's alive.
|
|
7958 assert(oop(addr)->klass() != NULL &&
|
|
7959 (!_collector->cms_should_unload_classes()
|
|
7960 || oop(addr)->is_parsable()),
|
|
7961 "Should be an initialized object");
|
|
7962 // Ignore mark word because we are running concurrent with mutators
|
|
7963 assert(oop(addr)->is_oop(true), "live block should be an oop");
|
|
7964 // Verify that the bit map has no bits marked between
|
|
7965 // addr and purported end of this block.
|
|
7966 size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size());
|
|
7967 assert(size >= 3, "Necessary for Printezis marks to work");
|
|
7968 assert(!_bitMap->isMarked(addr+1), "Tautology for this control point");
|
|
7969 DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);)
|
|
7970 }
|
|
7971 return size;
|
|
7972 }
|
|
7973
|
|
7974 void SweepClosure::doPostIsFreeOrGarbageChunk(FreeChunk* fc,
|
|
7975 size_t chunkSize) {
|
|
7976 // doPostIsFreeOrGarbageChunk() should only be called in the smart allocation
|
|
7977 // scheme.
|
|
7978 bool fcInFreeLists = fc->isFree();
|
|
7979 assert(_sp->adaptive_freelists(), "Should only be used in this case.");
|
|
7980 assert((HeapWord*)fc <= _limit, "sweep invariant");
|
|
7981 if (CMSTestInFreeList && fcInFreeLists) {
|
|
7982 assert(_sp->verifyChunkInFreeLists(fc),
|
|
7983 "free chunk is not in free lists");
|
|
7984 }
|
|
7985
|
|
7986
|
|
7987 if (CMSTraceSweeper) {
|
|
7988 gclog_or_tty->print_cr(" -- pick up another chunk at 0x%x (%d)", fc, chunkSize);
|
|
7989 }
|
|
7990
|
|
7991 HeapWord* addr = (HeapWord*) fc;
|
|
7992
|
|
7993 bool coalesce;
|
|
7994 size_t left = pointer_delta(addr, freeFinger());
|
|
7995 size_t right = chunkSize;
|
|
7996 switch (FLSCoalescePolicy) {
|
|
7997 // numeric value forms a coalition aggressiveness metric
|
|
7998 case 0: { // never coalesce
|
|
7999 coalesce = false;
|
|
8000 break;
|
|
8001 }
|
|
8002 case 1: { // coalesce if left & right chunks on overpopulated lists
|
|
8003 coalesce = _sp->coalOverPopulated(left) &&
|
|
8004 _sp->coalOverPopulated(right);
|
|
8005 break;
|
|
8006 }
|
|
8007 case 2: { // coalesce if left chunk on overpopulated list (default)
|
|
8008 coalesce = _sp->coalOverPopulated(left);
|
|
8009 break;
|
|
8010 }
|
|
8011 case 3: { // coalesce if left OR right chunk on overpopulated list
|
|
8012 coalesce = _sp->coalOverPopulated(left) ||
|
|
8013 _sp->coalOverPopulated(right);
|
|
8014 break;
|
|
8015 }
|
|
8016 case 4: { // always coalesce
|
|
8017 coalesce = true;
|
|
8018 break;
|
|
8019 }
|
|
8020 default:
|
|
8021 ShouldNotReachHere();
|
|
8022 }
|
|
8023
|
|
8024 // Should the current free range be coalesced?
|
|
8025 // If the chunk is in a free range and either we decided to coalesce above
|
|
8026 // or the chunk is near the large block at the end of the heap
|
|
8027 // (isNearLargestChunk() returns true), then coalesce this chunk.
|
|
8028 bool doCoalesce = inFreeRange() &&
|
|
8029 (coalesce || _g->isNearLargestChunk((HeapWord*)fc));
|
|
8030 if (doCoalesce) {
|
|
8031 // Coalesce the current free range on the left with the new
|
|
8032 // chunk on the right. If either is on a free list,
|
|
8033 // it must be removed from the list and stashed in the closure.
|
|
8034 if (freeRangeInFreeLists()) {
|
|
8035 FreeChunk* ffc = (FreeChunk*)freeFinger();
|
|
8036 assert(ffc->size() == pointer_delta(addr, freeFinger()),
|
|
8037 "Size of free range is inconsistent with chunk size.");
|
|
8038 if (CMSTestInFreeList) {
|
|
8039 assert(_sp->verifyChunkInFreeLists(ffc),
|
|
8040 "Chunk is not in free lists");
|
|
8041 }
|
|
8042 _sp->coalDeath(ffc->size());
|
|
8043 _sp->removeFreeChunkFromFreeLists(ffc);
|
|
8044 set_freeRangeInFreeLists(false);
|
|
8045 }
|
|
8046 if (fcInFreeLists) {
|
|
8047 _sp->coalDeath(chunkSize);
|
|
8048 assert(fc->size() == chunkSize,
|
|
8049 "The chunk has the wrong size or is not in the free lists");
|
|
8050 _sp->removeFreeChunkFromFreeLists(fc);
|
|
8051 }
|
|
8052 set_lastFreeRangeCoalesced(true);
|
|
8053 } else { // not in a free range and/or should not coalesce
|
|
8054 // Return the current free range and start a new one.
|
|
8055 if (inFreeRange()) {
|
|
8056 // In a free range but cannot coalesce with the right hand chunk.
|
|
8057 // Put the current free range into the free lists.
|
|
8058 flushCurFreeChunk(freeFinger(),
|
|
8059 pointer_delta(addr, freeFinger()));
|
|
8060 }
|
|
8061 // Set up for new free range. Pass along whether the right hand
|
|
8062 // chunk is in the free lists.
|
|
8063 initialize_free_range((HeapWord*)fc, fcInFreeLists);
|
|
8064 }
|
|
8065 }
|
|
8066 void SweepClosure::flushCurFreeChunk(HeapWord* chunk, size_t size) {
|
|
8067 assert(inFreeRange(), "Should only be called if currently in a free range.");
|
|
8068 assert(size > 0,
|
|
8069 "A zero sized chunk cannot be added to the free lists.");
|
|
8070 if (!freeRangeInFreeLists()) {
|
|
8071 if(CMSTestInFreeList) {
|
|
8072 FreeChunk* fc = (FreeChunk*) chunk;
|
|
8073 fc->setSize(size);
|
|
8074 assert(!_sp->verifyChunkInFreeLists(fc),
|
|
8075 "chunk should not be in free lists yet");
|
|
8076 }
|
|
8077 if (CMSTraceSweeper) {
|
|
8078 gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists",
|
|
8079 chunk, size);
|
|
8080 }
|
|
8081 // A new free range is going to be starting. The current
|
|
8082 // free range has not been added to the free lists yet or
|
|
8083 // was removed so add it back.
|
|
8084 // If the current free range was coalesced, then the death
|
|
8085 // of the free range was recorded. Record a birth now.
|
|
8086 if (lastFreeRangeCoalesced()) {
|
|
8087 _sp->coalBirth(size);
|
|
8088 }
|
|
8089 _sp->addChunkAndRepairOffsetTable(chunk, size,
|
|
8090 lastFreeRangeCoalesced());
|
|
8091 }
|
|
8092 set_inFreeRange(false);
|
|
8093 set_freeRangeInFreeLists(false);
|
|
8094 }
|
|
8095
|
|
8096 // We take a break if we've been at this for a while,
|
|
8097 // so as to avoid monopolizing the locks involved.
|
|
8098 void SweepClosure::do_yield_work(HeapWord* addr) {
|
|
8099 // Return current free chunk being used for coalescing (if any)
|
|
8100 // to the appropriate freelist. After yielding, the next
|
|
8101 // free block encountered will start a coalescing range of
|
|
8102 // free blocks. If the next free block is adjacent to the
|
|
8103 // chunk just flushed, they will need to wait for the next
|
|
8104 // sweep to be coalesced.
|
|
8105 if (inFreeRange()) {
|
|
8106 flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger()));
|
|
8107 }
|
|
8108
|
|
8109 // First give up the locks, then yield, then re-lock.
|
|
8110 // We should probably use a constructor/destructor idiom to
|
|
8111 // do this unlock/lock or modify the MutexUnlocker class to
|
|
8112 // serve our purpose. XXX
|
|
8113 assert_lock_strong(_bitMap->lock());
|
|
8114 assert_lock_strong(_freelistLock);
|
|
8115 assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
|
|
8116 "CMS thread should hold CMS token");
|
|
8117 _bitMap->lock()->unlock();
|
|
8118 _freelistLock->unlock();
|
|
8119 ConcurrentMarkSweepThread::desynchronize(true);
|
|
8120 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
8121 _collector->stopTimer();
|
|
8122 GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
|
|
8123 if (PrintCMSStatistics != 0) {
|
|
8124 _collector->incrementYields();
|
|
8125 }
|
|
8126 _collector->icms_wait();
|
|
8127
|
|
8128 // See the comment in coordinator_yield()
|
|
8129 for (unsigned i = 0; i < CMSYieldSleepCount &&
|
|
8130 ConcurrentMarkSweepThread::should_yield() &&
|
|
8131 !CMSCollector::foregroundGCIsActive(); ++i) {
|
|
8132 os::sleep(Thread::current(), 1, false);
|
|
8133 ConcurrentMarkSweepThread::acknowledge_yield_request();
|
|
8134 }
|
|
8135
|
|
8136 ConcurrentMarkSweepThread::synchronize(true);
|
|
8137 _freelistLock->lock();
|
|
8138 _bitMap->lock()->lock_without_safepoint_check();
|
|
8139 _collector->startTimer();
|
|
8140 }
|
|
8141
|
|
8142 #ifndef PRODUCT
|
|
8143 // This is actually very useful in a product build if it can
|
|
8144 // be called from the debugger. Compile it into the product
|
|
8145 // as needed.
|
|
8146 bool debug_verifyChunkInFreeLists(FreeChunk* fc) {
|
|
8147 return debug_cms_space->verifyChunkInFreeLists(fc);
|
|
8148 }
|
|
8149
|
|
8150 void SweepClosure::record_free_block_coalesced(FreeChunk* fc) const {
|
|
8151 if (CMSTraceSweeper) {
|
|
8152 gclog_or_tty->print("Sweep:coal_free_blk 0x%x (%d)\n", fc, fc->size());
|
|
8153 }
|
|
8154 }
|
|
8155 #endif
|
|
8156
|
|
8157 // CMSIsAliveClosure
|
|
8158 bool CMSIsAliveClosure::do_object_b(oop obj) {
|
|
8159 HeapWord* addr = (HeapWord*)obj;
|
|
8160 return addr != NULL &&
|
|
8161 (!_span.contains(addr) || _bit_map->isMarked(addr));
|
|
8162 }
|
|
8163
|
|
8164 // CMSKeepAliveClosure: the serial version
|
|
8165 void CMSKeepAliveClosure::do_oop(oop* p) {
|
|
8166 oop this_oop = *p;
|
|
8167 HeapWord* addr = (HeapWord*)this_oop;
|
|
8168 if (_span.contains(addr) &&
|
|
8169 !_bit_map->isMarked(addr)) {
|
|
8170 _bit_map->mark(addr);
|
|
8171 bool simulate_overflow = false;
|
|
8172 NOT_PRODUCT(
|
|
8173 if (CMSMarkStackOverflowALot &&
|
|
8174 _collector->simulate_overflow()) {
|
|
8175 // simulate a stack overflow
|
|
8176 simulate_overflow = true;
|
|
8177 }
|
|
8178 )
|
|
8179 if (simulate_overflow || !_mark_stack->push(this_oop)) {
|
|
8180 _collector->push_on_overflow_list(this_oop);
|
|
8181 _collector->_ser_kac_ovflw++;
|
|
8182 }
|
|
8183 }
|
|
8184 }
|
|
8185
|
|
8186 // CMSParKeepAliveClosure: a parallel version of the above.
|
|
8187 // The work queues are private to each closure (thread),
|
|
8188 // but (may be) available for stealing by other threads.
|
|
8189 void CMSParKeepAliveClosure::do_oop(oop* p) {
|
|
8190 oop this_oop = *p;
|
|
8191 HeapWord* addr = (HeapWord*)this_oop;
|
|
8192 if (_span.contains(addr) &&
|
|
8193 !_bit_map->isMarked(addr)) {
|
|
8194 // In general, during recursive tracing, several threads
|
|
8195 // may be concurrently getting here; the first one to
|
|
8196 // "tag" it, claims it.
|
|
8197 if (_bit_map->par_mark(addr)) {
|
|
8198 bool res = _work_queue->push(this_oop);
|
|
8199 assert(res, "Low water mark should be much less than capacity");
|
|
8200 // Do a recursive trim in the hope that this will keep
|
|
8201 // stack usage lower, but leave some oops for potential stealers
|
|
8202 trim_queue(_low_water_mark);
|
|
8203 } // Else, another thread got there first
|
|
8204 }
|
|
8205 }
|
|
8206
|
|
8207 void CMSParKeepAliveClosure::trim_queue(uint max) {
|
|
8208 while (_work_queue->size() > max) {
|
|
8209 oop new_oop;
|
|
8210 if (_work_queue->pop_local(new_oop)) {
|
|
8211 assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop");
|
|
8212 assert(_bit_map->isMarked((HeapWord*)new_oop),
|
|
8213 "no white objects on this stack!");
|
|
8214 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop");
|
|
8215 // iterate over the oops in this oop, marking and pushing
|
|
8216 // the ones in CMS heap (i.e. in _span).
|
|
8217 new_oop->oop_iterate(&_mark_and_push);
|
|
8218 }
|
|
8219 }
|
|
8220 }
|
|
8221
|
|
8222 void CMSInnerParMarkAndPushClosure::do_oop(oop* p) {
|
|
8223 oop this_oop = *p;
|
|
8224 HeapWord* addr = (HeapWord*)this_oop;
|
|
8225 if (_span.contains(addr) &&
|
|
8226 !_bit_map->isMarked(addr)) {
|
|
8227 if (_bit_map->par_mark(addr)) {
|
|
8228 bool simulate_overflow = false;
|
|
8229 NOT_PRODUCT(
|
|
8230 if (CMSMarkStackOverflowALot &&
|
|
8231 _collector->par_simulate_overflow()) {
|
|
8232 // simulate a stack overflow
|
|
8233 simulate_overflow = true;
|
|
8234 }
|
|
8235 )
|
|
8236 if (simulate_overflow || !_work_queue->push(this_oop)) {
|
|
8237 _collector->par_push_on_overflow_list(this_oop);
|
|
8238 _collector->_par_kac_ovflw++;
|
|
8239 }
|
|
8240 } // Else another thread got there already
|
|
8241 }
|
|
8242 }
|
|
8243
|
|
8244 //////////////////////////////////////////////////////////////////
|
|
8245 // CMSExpansionCause /////////////////////////////
|
|
8246 //////////////////////////////////////////////////////////////////
|
|
8247 const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) {
|
|
8248 switch (cause) {
|
|
8249 case _no_expansion:
|
|
8250 return "No expansion";
|
|
8251 case _satisfy_free_ratio:
|
|
8252 return "Free ratio";
|
|
8253 case _satisfy_promotion:
|
|
8254 return "Satisfy promotion";
|
|
8255 case _satisfy_allocation:
|
|
8256 return "allocation";
|
|
8257 case _allocate_par_lab:
|
|
8258 return "Par LAB";
|
|
8259 case _allocate_par_spooling_space:
|
|
8260 return "Par Spooling Space";
|
|
8261 case _adaptive_size_policy:
|
|
8262 return "Ergonomics";
|
|
8263 default:
|
|
8264 return "unknown";
|
|
8265 }
|
|
8266 }
|
|
8267
|
|
8268 void CMSDrainMarkingStackClosure::do_void() {
|
|
8269 // the max number to take from overflow list at a time
|
|
8270 const size_t num = _mark_stack->capacity()/4;
|
|
8271 while (!_mark_stack->isEmpty() ||
|
|
8272 // if stack is empty, check the overflow list
|
|
8273 _collector->take_from_overflow_list(num, _mark_stack)) {
|
|
8274 oop this_oop = _mark_stack->pop();
|
|
8275 HeapWord* addr = (HeapWord*)this_oop;
|
|
8276 assert(_span.contains(addr), "Should be within span");
|
|
8277 assert(_bit_map->isMarked(addr), "Should be marked");
|
|
8278 assert(this_oop->is_oop(), "Should be an oop");
|
|
8279 this_oop->oop_iterate(_keep_alive);
|
|
8280 }
|
|
8281 }
|
|
8282
|
|
8283 void CMSParDrainMarkingStackClosure::do_void() {
|
|
8284 // drain queue
|
|
8285 trim_queue(0);
|
|
8286 }
|
|
8287
|
|
8288 // Trim our work_queue so its length is below max at return
|
|
8289 void CMSParDrainMarkingStackClosure::trim_queue(uint max) {
|
|
8290 while (_work_queue->size() > max) {
|
|
8291 oop new_oop;
|
|
8292 if (_work_queue->pop_local(new_oop)) {
|
|
8293 assert(new_oop->is_oop(), "Expected an oop");
|
|
8294 assert(_bit_map->isMarked((HeapWord*)new_oop),
|
|
8295 "no white objects on this stack!");
|
|
8296 assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop");
|
|
8297 // iterate over the oops in this oop, marking and pushing
|
|
8298 // the ones in CMS heap (i.e. in _span).
|
|
8299 new_oop->oop_iterate(&_mark_and_push);
|
|
8300 }
|
|
8301 }
|
|
8302 }
|
|
8303
|
|
8304 ////////////////////////////////////////////////////////////////////
|
|
8305 // Support for Marking Stack Overflow list handling and related code
|
|
8306 ////////////////////////////////////////////////////////////////////
|
|
8307 // Much of the following code is similar in shape and spirit to the
|
|
8308 // code used in ParNewGC. We should try and share that code
|
|
8309 // as much as possible in the future.
|
|
8310
|
|
8311 #ifndef PRODUCT
|
|
8312 // Debugging support for CMSStackOverflowALot
|
|
8313
|
|
8314 // It's OK to call this multi-threaded; the worst thing
|
|
8315 // that can happen is that we'll get a bunch of closely
|
|
8316 // spaced simulated oveflows, but that's OK, in fact
|
|
8317 // probably good as it would exercise the overflow code
|
|
8318 // under contention.
|
|
8319 bool CMSCollector::simulate_overflow() {
|
|
8320 if (_overflow_counter-- <= 0) { // just being defensive
|
|
8321 _overflow_counter = CMSMarkStackOverflowInterval;
|
|
8322 return true;
|
|
8323 } else {
|
|
8324 return false;
|
|
8325 }
|
|
8326 }
|
|
8327
|
|
8328 bool CMSCollector::par_simulate_overflow() {
|
|
8329 return simulate_overflow();
|
|
8330 }
|
|
8331 #endif
|
|
8332
|
|
8333 // Single-threaded
|
|
8334 bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) {
|
|
8335 assert(stack->isEmpty(), "Expected precondition");
|
|
8336 assert(stack->capacity() > num, "Shouldn't bite more than can chew");
|
|
8337 size_t i = num;
|
|
8338 oop cur = _overflow_list;
|
|
8339 const markOop proto = markOopDesc::prototype();
|
|
8340 NOT_PRODUCT(size_t n = 0;)
|
|
8341 for (oop next; i > 0 && cur != NULL; cur = next, i--) {
|
|
8342 next = oop(cur->mark());
|
|
8343 cur->set_mark(proto); // until proven otherwise
|
|
8344 assert(cur->is_oop(), "Should be an oop");
|
|
8345 bool res = stack->push(cur);
|
|
8346 assert(res, "Bit off more than can chew?");
|
|
8347 NOT_PRODUCT(n++;)
|
|
8348 }
|
|
8349 _overflow_list = cur;
|
|
8350 #ifndef PRODUCT
|
|
8351 assert(_num_par_pushes >= n, "Too many pops?");
|
|
8352 _num_par_pushes -=n;
|
|
8353 #endif
|
|
8354 return !stack->isEmpty();
|
|
8355 }
|
|
8356
|
|
8357 // Multi-threaded; use CAS to break off a prefix
|
|
8358 bool CMSCollector::par_take_from_overflow_list(size_t num,
|
|
8359 OopTaskQueue* work_q) {
|
|
8360 assert(work_q->size() == 0, "That's the current policy");
|
|
8361 assert(num < work_q->max_elems(), "Can't bite more than we can chew");
|
|
8362 if (_overflow_list == NULL) {
|
|
8363 return false;
|
|
8364 }
|
|
8365 // Grab the entire list; we'll put back a suffix
|
|
8366 oop prefix = (oop)Atomic::xchg_ptr(NULL, &_overflow_list);
|
|
8367 if (prefix == NULL) { // someone grabbed it before we did ...
|
|
8368 // ... we could spin for a short while, but for now we don't
|
|
8369 return false;
|
|
8370 }
|
|
8371 size_t i = num;
|
|
8372 oop cur = prefix;
|
|
8373 for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--);
|
|
8374 if (cur->mark() != NULL) {
|
|
8375 oop suffix_head = cur->mark(); // suffix will be put back on global list
|
|
8376 cur->set_mark(NULL); // break off suffix
|
|
8377 // Find tail of suffix so we can prepend suffix to global list
|
|
8378 for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark()));
|
|
8379 oop suffix_tail = cur;
|
|
8380 assert(suffix_tail != NULL && suffix_tail->mark() == NULL,
|
|
8381 "Tautology");
|
|
8382 oop observed_overflow_list = _overflow_list;
|
|
8383 do {
|
|
8384 cur = observed_overflow_list;
|
|
8385 suffix_tail->set_mark(markOop(cur));
|
|
8386 observed_overflow_list =
|
|
8387 (oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur);
|
|
8388 } while (cur != observed_overflow_list);
|
|
8389 }
|
|
8390
|
|
8391 // Push the prefix elements on work_q
|
|
8392 assert(prefix != NULL, "control point invariant");
|
|
8393 const markOop proto = markOopDesc::prototype();
|
|
8394 oop next;
|
|
8395 NOT_PRODUCT(size_t n = 0;)
|
|
8396 for (cur = prefix; cur != NULL; cur = next) {
|
|
8397 next = oop(cur->mark());
|
|
8398 cur->set_mark(proto); // until proven otherwise
|
|
8399 assert(cur->is_oop(), "Should be an oop");
|
|
8400 bool res = work_q->push(cur);
|
|
8401 assert(res, "Bit off more than we can chew?");
|
|
8402 NOT_PRODUCT(n++;)
|
|
8403 }
|
|
8404 #ifndef PRODUCT
|
|
8405 assert(_num_par_pushes >= n, "Too many pops?");
|
|
8406 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes);
|
|
8407 #endif
|
|
8408 return true;
|
|
8409 }
|
|
8410
|
|
8411 // Single-threaded
|
|
8412 void CMSCollector::push_on_overflow_list(oop p) {
|
|
8413 NOT_PRODUCT(_num_par_pushes++;)
|
|
8414 assert(p->is_oop(), "Not an oop");
|
|
8415 preserve_mark_if_necessary(p);
|
|
8416 p->set_mark((markOop)_overflow_list);
|
|
8417 _overflow_list = p;
|
|
8418 }
|
|
8419
|
|
8420 // Multi-threaded; use CAS to prepend to overflow list
|
|
8421 void CMSCollector::par_push_on_overflow_list(oop p) {
|
|
8422 NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);)
|
|
8423 assert(p->is_oop(), "Not an oop");
|
|
8424 par_preserve_mark_if_necessary(p);
|
|
8425 oop observed_overflow_list = _overflow_list;
|
|
8426 oop cur_overflow_list;
|
|
8427 do {
|
|
8428 cur_overflow_list = observed_overflow_list;
|
|
8429 p->set_mark(markOop(cur_overflow_list));
|
|
8430 observed_overflow_list =
|
|
8431 (oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list);
|
|
8432 } while (cur_overflow_list != observed_overflow_list);
|
|
8433 }
|
|
8434
|
|
8435 // Single threaded
|
|
8436 // General Note on GrowableArray: pushes may silently fail
|
|
8437 // because we are (temporarily) out of C-heap for expanding
|
|
8438 // the stack. The problem is quite ubiquitous and affects
|
|
8439 // a lot of code in the JVM. The prudent thing for GrowableArray
|
|
8440 // to do (for now) is to exit with an error. However, that may
|
|
8441 // be too draconian in some cases because the caller may be
|
|
8442 // able to recover without much harm. For suych cases, we
|
|
8443 // should probably introduce a "soft_push" method which returns
|
|
8444 // an indication of success or failure with the assumption that
|
|
8445 // the caller may be able to recover from a failure; code in
|
|
8446 // the VM can then be changed, incrementally, to deal with such
|
|
8447 // failures where possible, thus, incrementally hardening the VM
|
|
8448 // in such low resource situations.
|
|
8449 void CMSCollector::preserve_mark_work(oop p, markOop m) {
|
|
8450 int PreserveMarkStackSize = 128;
|
|
8451
|
|
8452 if (_preserved_oop_stack == NULL) {
|
|
8453 assert(_preserved_mark_stack == NULL,
|
|
8454 "bijection with preserved_oop_stack");
|
|
8455 // Allocate the stacks
|
|
8456 _preserved_oop_stack = new (ResourceObj::C_HEAP)
|
|
8457 GrowableArray<oop>(PreserveMarkStackSize, true);
|
|
8458 _preserved_mark_stack = new (ResourceObj::C_HEAP)
|
|
8459 GrowableArray<markOop>(PreserveMarkStackSize, true);
|
|
8460 if (_preserved_oop_stack == NULL || _preserved_mark_stack == NULL) {
|
|
8461 vm_exit_out_of_memory(2* PreserveMarkStackSize * sizeof(oop) /* punt */,
|
|
8462 "Preserved Mark/Oop Stack for CMS (C-heap)");
|
|
8463 }
|
|
8464 }
|
|
8465 _preserved_oop_stack->push(p);
|
|
8466 _preserved_mark_stack->push(m);
|
|
8467 assert(m == p->mark(), "Mark word changed");
|
|
8468 assert(_preserved_oop_stack->length() == _preserved_mark_stack->length(),
|
|
8469 "bijection");
|
|
8470 }
|
|
8471
|
|
8472 // Single threaded
|
|
8473 void CMSCollector::preserve_mark_if_necessary(oop p) {
|
|
8474 markOop m = p->mark();
|
|
8475 if (m->must_be_preserved(p)) {
|
|
8476 preserve_mark_work(p, m);
|
|
8477 }
|
|
8478 }
|
|
8479
|
|
8480 void CMSCollector::par_preserve_mark_if_necessary(oop p) {
|
|
8481 markOop m = p->mark();
|
|
8482 if (m->must_be_preserved(p)) {
|
|
8483 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
|
|
8484 // Even though we read the mark word without holding
|
|
8485 // the lock, we are assured that it will not change
|
|
8486 // because we "own" this oop, so no other thread can
|
|
8487 // be trying to push it on the overflow list; see
|
|
8488 // the assertion in preserve_mark_work() that checks
|
|
8489 // that m == p->mark().
|
|
8490 preserve_mark_work(p, m);
|
|
8491 }
|
|
8492 }
|
|
8493
|
|
8494 // We should be able to do this multi-threaded,
|
|
8495 // a chunk of stack being a task (this is
|
|
8496 // correct because each oop only ever appears
|
|
8497 // once in the overflow list. However, it's
|
|
8498 // not very easy to completely overlap this with
|
|
8499 // other operations, so will generally not be done
|
|
8500 // until all work's been completed. Because we
|
|
8501 // expect the preserved oop stack (set) to be small,
|
|
8502 // it's probably fine to do this single-threaded.
|
|
8503 // We can explore cleverer concurrent/overlapped/parallel
|
|
8504 // processing of preserved marks if we feel the
|
|
8505 // need for this in the future. Stack overflow should
|
|
8506 // be so rare in practice and, when it happens, its
|
|
8507 // effect on performance so great that this will
|
|
8508 // likely just be in the noise anyway.
|
|
8509 void CMSCollector::restore_preserved_marks_if_any() {
|
|
8510 if (_preserved_oop_stack == NULL) {
|
|
8511 assert(_preserved_mark_stack == NULL,
|
|
8512 "bijection with preserved_oop_stack");
|
|
8513 return;
|
|
8514 }
|
|
8515
|
|
8516 assert(SafepointSynchronize::is_at_safepoint(),
|
|
8517 "world should be stopped");
|
|
8518 assert(Thread::current()->is_ConcurrentGC_thread() ||
|
|
8519 Thread::current()->is_VM_thread(),
|
|
8520 "should be single-threaded");
|
|
8521
|
|
8522 int length = _preserved_oop_stack->length();
|
|
8523 assert(_preserved_mark_stack->length() == length, "bijection");
|
|
8524 for (int i = 0; i < length; i++) {
|
|
8525 oop p = _preserved_oop_stack->at(i);
|
|
8526 assert(p->is_oop(), "Should be an oop");
|
|
8527 assert(_span.contains(p), "oop should be in _span");
|
|
8528 assert(p->mark() == markOopDesc::prototype(),
|
|
8529 "Set when taken from overflow list");
|
|
8530 markOop m = _preserved_mark_stack->at(i);
|
|
8531 p->set_mark(m);
|
|
8532 }
|
|
8533 _preserved_mark_stack->clear();
|
|
8534 _preserved_oop_stack->clear();
|
|
8535 assert(_preserved_mark_stack->is_empty() &&
|
|
8536 _preserved_oop_stack->is_empty(),
|
|
8537 "stacks were cleared above");
|
|
8538 }
|
|
8539
|
|
8540 #ifndef PRODUCT
|
|
8541 bool CMSCollector::no_preserved_marks() const {
|
|
8542 return ( ( _preserved_mark_stack == NULL
|
|
8543 && _preserved_oop_stack == NULL)
|
|
8544 || ( _preserved_mark_stack->is_empty()
|
|
8545 && _preserved_oop_stack->is_empty()));
|
|
8546 }
|
|
8547 #endif
|
|
8548
|
|
8549 CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const
|
|
8550 {
|
|
8551 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap();
|
|
8552 CMSAdaptiveSizePolicy* size_policy =
|
|
8553 (CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy();
|
|
8554 assert(size_policy->is_gc_cms_adaptive_size_policy(),
|
|
8555 "Wrong type for size policy");
|
|
8556 return size_policy;
|
|
8557 }
|
|
8558
|
|
8559 void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size,
|
|
8560 size_t desired_promo_size) {
|
|
8561 if (cur_promo_size < desired_promo_size) {
|
|
8562 size_t expand_bytes = desired_promo_size - cur_promo_size;
|
|
8563 if (PrintAdaptiveSizePolicy && Verbose) {
|
|
8564 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize "
|
|
8565 "Expanding tenured generation by " SIZE_FORMAT " (bytes)",
|
|
8566 expand_bytes);
|
|
8567 }
|
|
8568 expand(expand_bytes,
|
|
8569 MinHeapDeltaBytes,
|
|
8570 CMSExpansionCause::_adaptive_size_policy);
|
|
8571 } else if (desired_promo_size < cur_promo_size) {
|
|
8572 size_t shrink_bytes = cur_promo_size - desired_promo_size;
|
|
8573 if (PrintAdaptiveSizePolicy && Verbose) {
|
|
8574 gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize "
|
|
8575 "Shrinking tenured generation by " SIZE_FORMAT " (bytes)",
|
|
8576 shrink_bytes);
|
|
8577 }
|
|
8578 shrink(shrink_bytes);
|
|
8579 }
|
|
8580 }
|
|
8581
|
|
8582 CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() {
|
|
8583 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
8584 CMSGCAdaptivePolicyCounters* counters =
|
|
8585 (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters();
|
|
8586 assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind,
|
|
8587 "Wrong kind of counters");
|
|
8588 return counters;
|
|
8589 }
|
|
8590
|
|
8591
|
|
8592 void ASConcurrentMarkSweepGeneration::update_counters() {
|
|
8593 if (UsePerfData) {
|
|
8594 _space_counters->update_all();
|
|
8595 _gen_counters->update_all();
|
|
8596 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters();
|
|
8597 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
8598 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats();
|
|
8599 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind,
|
|
8600 "Wrong gc statistics type");
|
|
8601 counters->update_counters(gc_stats_l);
|
|
8602 }
|
|
8603 }
|
|
8604
|
|
8605 void ASConcurrentMarkSweepGeneration::update_counters(size_t used) {
|
|
8606 if (UsePerfData) {
|
|
8607 _space_counters->update_used(used);
|
|
8608 _space_counters->update_capacity();
|
|
8609 _gen_counters->update_all();
|
|
8610
|
|
8611 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters();
|
|
8612 GenCollectedHeap* gch = GenCollectedHeap::heap();
|
|
8613 CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats();
|
|
8614 assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind,
|
|
8615 "Wrong gc statistics type");
|
|
8616 counters->update_counters(gc_stats_l);
|
|
8617 }
|
|
8618 }
|
|
8619
|
|
8620 // The desired expansion delta is computed so that:
|
|
8621 // . desired free percentage or greater is used
|
|
8622 void ASConcurrentMarkSweepGeneration::compute_new_size() {
|
|
8623 assert_locked_or_safepoint(Heap_lock);
|
|
8624
|
|
8625 GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap();
|
|
8626
|
|
8627 // If incremental collection failed, we just want to expand
|
|
8628 // to the limit.
|
|
8629 if (incremental_collection_failed()) {
|
|
8630 clear_incremental_collection_failed();
|
|
8631 grow_to_reserved();
|
|
8632 return;
|
|
8633 }
|
|
8634
|
|
8635 assert(UseAdaptiveSizePolicy, "Should be using adaptive sizing");
|
|
8636
|
|
8637 assert(gch->kind() == CollectedHeap::GenCollectedHeap,
|
|
8638 "Wrong type of heap");
|
|
8639 int prev_level = level() - 1;
|
|
8640 assert(prev_level >= 0, "The cms generation is the lowest generation");
|
|
8641 Generation* prev_gen = gch->get_gen(prev_level);
|
|
8642 assert(prev_gen->kind() == Generation::ASParNew,
|
|
8643 "Wrong type of young generation");
|
|
8644 ParNewGeneration* younger_gen = (ParNewGeneration*) prev_gen;
|
|
8645 size_t cur_eden = younger_gen->eden()->capacity();
|
|
8646 CMSAdaptiveSizePolicy* size_policy = cms_size_policy();
|
|
8647 size_t cur_promo = free();
|
|
8648 size_policy->compute_tenured_generation_free_space(cur_promo,
|
|
8649 max_available(),
|
|
8650 cur_eden);
|
|
8651 resize(cur_promo, size_policy->promo_size());
|
|
8652
|
|
8653 // Record the new size of the space in the cms generation
|
|
8654 // that is available for promotions. This is temporary.
|
|
8655 // It should be the desired promo size.
|
|
8656 size_policy->avg_cms_promo()->sample(free());
|
|
8657 size_policy->avg_old_live()->sample(used());
|
|
8658
|
|
8659 if (UsePerfData) {
|
|
8660 CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters();
|
|
8661 counters->update_cms_capacity_counter(capacity());
|
|
8662 }
|
|
8663 }
|
|
8664
|
|
8665 void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) {
|
|
8666 assert_locked_or_safepoint(Heap_lock);
|
|
8667 assert_lock_strong(freelistLock());
|
|
8668 HeapWord* old_end = _cmsSpace->end();
|
|
8669 HeapWord* unallocated_start = _cmsSpace->unallocated_block();
|
|
8670 assert(old_end >= unallocated_start, "Miscalculation of unallocated_start");
|
|
8671 FreeChunk* chunk_at_end = find_chunk_at_end();
|
|
8672 if (chunk_at_end == NULL) {
|
|
8673 // No room to shrink
|
|
8674 if (PrintGCDetails && Verbose) {
|
|
8675 gclog_or_tty->print_cr("No room to shrink: old_end "
|
|
8676 PTR_FORMAT " unallocated_start " PTR_FORMAT
|
|
8677 " chunk_at_end " PTR_FORMAT,
|
|
8678 old_end, unallocated_start, chunk_at_end);
|
|
8679 }
|
|
8680 return;
|
|
8681 } else {
|
|
8682
|
|
8683 // Find the chunk at the end of the space and determine
|
|
8684 // how much it can be shrunk.
|
|
8685 size_t shrinkable_size_in_bytes = chunk_at_end->size();
|
|
8686 size_t aligned_shrinkable_size_in_bytes =
|
|
8687 align_size_down(shrinkable_size_in_bytes, os::vm_page_size());
|
|
8688 assert(unallocated_start <= chunk_at_end->end(),
|
|
8689 "Inconsistent chunk at end of space");
|
|
8690 size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes);
|
|
8691 size_t word_size_before = heap_word_size(_virtual_space.committed_size());
|
|
8692
|
|
8693 // Shrink the underlying space
|
|
8694 _virtual_space.shrink_by(bytes);
|
|
8695 if (PrintGCDetails && Verbose) {
|
|
8696 gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:"
|
|
8697 " desired_bytes " SIZE_FORMAT
|
|
8698 " shrinkable_size_in_bytes " SIZE_FORMAT
|
|
8699 " aligned_shrinkable_size_in_bytes " SIZE_FORMAT
|
|
8700 " bytes " SIZE_FORMAT,
|
|
8701 desired_bytes, shrinkable_size_in_bytes,
|
|
8702 aligned_shrinkable_size_in_bytes, bytes);
|
|
8703 gclog_or_tty->print_cr(" old_end " SIZE_FORMAT
|
|
8704 " unallocated_start " SIZE_FORMAT,
|
|
8705 old_end, unallocated_start);
|
|
8706 }
|
|
8707
|
|
8708 // If the space did shrink (shrinking is not guaranteed),
|
|
8709 // shrink the chunk at the end by the appropriate amount.
|
|
8710 if (((HeapWord*)_virtual_space.high()) < old_end) {
|
|
8711 size_t new_word_size =
|
|
8712 heap_word_size(_virtual_space.committed_size());
|
|
8713
|
|
8714 // Have to remove the chunk from the dictionary because it is changing
|
|
8715 // size and might be someplace elsewhere in the dictionary.
|
|
8716
|
|
8717 // Get the chunk at end, shrink it, and put it
|
|
8718 // back.
|
|
8719 _cmsSpace->removeChunkFromDictionary(chunk_at_end);
|
|
8720 size_t word_size_change = word_size_before - new_word_size;
|
|
8721 size_t chunk_at_end_old_size = chunk_at_end->size();
|
|
8722 assert(chunk_at_end_old_size >= word_size_change,
|
|
8723 "Shrink is too large");
|
|
8724 chunk_at_end->setSize(chunk_at_end_old_size -
|
|
8725 word_size_change);
|
|
8726 _cmsSpace->freed((HeapWord*) chunk_at_end->end(),
|
|
8727 word_size_change);
|
|
8728
|
|
8729 _cmsSpace->returnChunkToDictionary(chunk_at_end);
|
|
8730
|
|
8731 MemRegion mr(_cmsSpace->bottom(), new_word_size);
|
|
8732 _bts->resize(new_word_size); // resize the block offset shared array
|
|
8733 Universe::heap()->barrier_set()->resize_covered_region(mr);
|
|
8734 _cmsSpace->assert_locked();
|
|
8735 _cmsSpace->set_end((HeapWord*)_virtual_space.high());
|
|
8736
|
|
8737 NOT_PRODUCT(_cmsSpace->dictionary()->verify());
|
|
8738
|
|
8739 // update the space and generation capacity counters
|
|
8740 if (UsePerfData) {
|
|
8741 _space_counters->update_capacity();
|
|
8742 _gen_counters->update_all();
|
|
8743 }
|
|
8744
|
|
8745 if (Verbose && PrintGCDetails) {
|
|
8746 size_t new_mem_size = _virtual_space.committed_size();
|
|
8747 size_t old_mem_size = new_mem_size + bytes;
|
|
8748 gclog_or_tty->print_cr("Shrinking %s from %ldK by %ldK to %ldK",
|
|
8749 name(), old_mem_size/K, bytes/K, new_mem_size/K);
|
|
8750 }
|
|
8751 }
|
|
8752
|
|
8753 assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(),
|
|
8754 "Inconsistency at end of space");
|
|
8755 assert(chunk_at_end->end() == _cmsSpace->end(),
|
|
8756 "Shrinking is inconsistent");
|
|
8757 return;
|
|
8758 }
|
|
8759 }
|
|
8760
|
|
8761 // Transfer some number of overflown objects to usual marking
|
|
8762 // stack. Return true if some objects were transferred.
|
|
8763 bool MarkRefsIntoAndScanClosure::take_from_overflow_list() {
|
|
8764 size_t num = MIN2((size_t)_mark_stack->capacity()/4,
|
|
8765 (size_t)ParGCDesiredObjsFromOverflowList);
|
|
8766
|
|
8767 bool res = _collector->take_from_overflow_list(num, _mark_stack);
|
|
8768 assert(_collector->overflow_list_is_empty() || res,
|
|
8769 "If list is not empty, we should have taken something");
|
|
8770 assert(!res || !_mark_stack->isEmpty(),
|
|
8771 "If we took something, it should now be on our stack");
|
|
8772 return res;
|
|
8773 }
|
|
8774
|
|
8775 size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) {
|
|
8776 size_t res = _sp->block_size_no_stall(addr, _collector);
|
|
8777 assert(res != 0, "Should always be able to compute a size");
|
|
8778 if (_sp->block_is_obj(addr)) {
|
|
8779 if (_live_bit_map->isMarked(addr)) {
|
|
8780 // It can't have been dead in a previous cycle
|
|
8781 guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!");
|
|
8782 } else {
|
|
8783 _dead_bit_map->mark(addr); // mark the dead object
|
|
8784 }
|
|
8785 }
|
|
8786 return res;
|
|
8787 }
|