342
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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/_concurrentZFThread.cpp.incl"
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27
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28 // ======= Concurrent Zero-Fill Thread ========
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29
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30 // The CM thread is created when the G1 garbage collector is used
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31
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32 int ConcurrentZFThread::_region_allocs = 0;
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33 int ConcurrentZFThread::_sync_zfs = 0;
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34 int ConcurrentZFThread::_zf_waits = 0;
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35 int ConcurrentZFThread::_regions_filled = 0;
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36
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37 ConcurrentZFThread::ConcurrentZFThread() :
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38 ConcurrentGCThread(),
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39 _co_tracker(G1ZFGroup)
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40 {
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41 create_and_start();
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42 }
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43
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44 void ConcurrentZFThread::wait_for_ZF_completed(HeapRegion* hr) {
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45 assert(ZF_mon->owned_by_self(), "Precondition.");
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46 note_zf_wait();
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47 while (hr->zero_fill_state() == HeapRegion::ZeroFilling) {
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48 ZF_mon->wait(Mutex::_no_safepoint_check_flag);
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49 }
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50 }
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51
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52 void ConcurrentZFThread::processHeapRegion(HeapRegion* hr) {
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53 assert(!Universe::heap()->is_gc_active(),
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54 "This should not happen during GC.");
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55 assert(hr != NULL, "Precondition");
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56 // These are unlocked reads, but if this test is successful, then no
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57 // other thread will attempt this zero filling. Only a GC thread can
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58 // modify the ZF state of a region whose state is zero-filling, and this
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59 // should only happen while the ZF thread is locking out GC.
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60 if (hr->zero_fill_state() == HeapRegion::ZeroFilling
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61 && hr->zero_filler() == Thread::current()) {
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62 assert(hr->top() == hr->bottom(), "better be empty!");
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63 assert(!hr->isHumongous(), "Only free regions on unclean list.");
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64 Copy::fill_to_words(hr->bottom(), hr->capacity()/HeapWordSize);
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65 note_region_filled();
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66 }
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67 }
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68
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69 void ConcurrentZFThread::run() {
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70 initialize_in_thread();
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71 Thread* thr_self = Thread::current();
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72 _vtime_start = os::elapsedVTime();
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73 wait_for_universe_init();
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74 _co_tracker.enable();
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75 _co_tracker.start();
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76
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77 G1CollectedHeap* g1 = G1CollectedHeap::heap();
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78 _sts.join();
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79 while (!_should_terminate) {
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80 _sts.leave();
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81
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82 {
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83 MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);
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84
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85 // This local variable will hold a region being zero-filled. This
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86 // region will neither be on the unclean or zero-filled lists, and
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87 // will not be available for allocation; thus, we might have an
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88 // allocation fail, causing a full GC, because of this, but this is a
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89 // price we will pay. (In future, we might want to make the fact
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90 // that there's a region being zero-filled apparent to the G1 heap,
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91 // which could then wait for it in this extreme case...)
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92 HeapRegion* to_fill;
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93
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94 while (!g1->should_zf()
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95 || (to_fill = g1->pop_unclean_region_list_locked()) == NULL)
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96 ZF_mon->wait(Mutex::_no_safepoint_check_flag);
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97 while (to_fill->zero_fill_state() == HeapRegion::ZeroFilling)
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98 ZF_mon->wait(Mutex::_no_safepoint_check_flag);
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99
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100 // So now to_fill is non-NULL and is not ZeroFilling. It might be
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101 // Allocated or ZeroFilled. (The latter could happen if this thread
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102 // starts the zero-filling of a region, but a GC intervenes and
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103 // pushes new regions needing on the front of the filling on the
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104 // front of the list.)
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105
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106 switch (to_fill->zero_fill_state()) {
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107 case HeapRegion::Allocated:
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108 to_fill = NULL;
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109 break;
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110
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111 case HeapRegion::NotZeroFilled:
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112 to_fill->set_zero_fill_in_progress(thr_self);
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113
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114 ZF_mon->unlock();
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115 _sts.join();
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116 processHeapRegion(to_fill);
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117 _sts.leave();
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118 ZF_mon->lock_without_safepoint_check();
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119
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120 if (to_fill->zero_fill_state() == HeapRegion::ZeroFilling
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121 && to_fill->zero_filler() == thr_self) {
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122 to_fill->set_zero_fill_complete();
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123 (void)g1->put_free_region_on_list_locked(to_fill);
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124 }
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125 break;
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126
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127 case HeapRegion::ZeroFilled:
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128 (void)g1->put_free_region_on_list_locked(to_fill);
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129 break;
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130
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131 case HeapRegion::ZeroFilling:
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132 ShouldNotReachHere();
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133 break;
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134 }
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135 }
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136 _vtime_accum = (os::elapsedVTime() - _vtime_start);
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137 _sts.join();
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138
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139 _co_tracker.update();
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140 }
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141 _co_tracker.update(false);
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142 _sts.leave();
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143
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144 assert(_should_terminate, "just checking");
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145 terminate();
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146 }
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147
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148 bool ConcurrentZFThread::offer_yield() {
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149 if (_sts.should_yield()) {
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150 _sts.yield("Concurrent ZF");
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151 return true;
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152 } else {
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153 return false;
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154 }
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155 }
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156
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157 void ConcurrentZFThread::stop() {
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158 // it is ok to take late safepoints here, if needed
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159 MutexLockerEx mu(Terminator_lock);
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160 _should_terminate = true;
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161 while (!_has_terminated) {
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162 Terminator_lock->wait();
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163 }
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164 }
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165
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166 void ConcurrentZFThread::print() {
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167 gclog_or_tty->print("\"Concurrent ZF Thread\" ");
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168 Thread::print();
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169 gclog_or_tty->cr();
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170 }
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171
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172
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173 double ConcurrentZFThread::_vtime_accum;
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174
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175 void ConcurrentZFThread::print_summary_info() {
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176 gclog_or_tty->print("\nConcurrent Zero-Filling:\n");
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177 gclog_or_tty->print(" Filled %d regions, used %5.2fs.\n",
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178 _regions_filled,
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179 vtime_accum());
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180 gclog_or_tty->print(" Of %d region allocs, %d (%5.2f%%) required sync ZF,\n",
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181 _region_allocs, _sync_zfs,
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182 (_region_allocs > 0 ?
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183 (float)_sync_zfs/(float)_region_allocs*100.0 :
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184 0.0));
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185 gclog_or_tty->print(" and %d (%5.2f%%) required a ZF wait.\n",
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186 _zf_waits,
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187 (_region_allocs > 0 ?
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188 (float)_zf_waits/(float)_region_allocs*100.0 :
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189 0.0));
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190
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191 }
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