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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 } |