1 /* 2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "gc_implementation/g1/g1MMUTracker.hpp" 27 #include "runtime/mutexLocker.hpp" 28 #include "utilities/ostream.hpp" 29 30 #define _DISABLE_MMU 0 31 32 // can't rely on comparing doubles with tolerating a small margin for error 33 #define SMALL_MARGIN 0.0000001 34 #define is_double_leq_0(_value) ( (_value) < SMALL_MARGIN ) 35 #define is_double_leq(_val1, _val2) is_double_leq_0((_val1) - (_val2)) 36 #define is_double_geq(_val1, _val2) is_double_leq_0((_val2) - (_val1)) 37 38 /***** ALL TIMES ARE IN SECS!!!!!!! *****/ 39 40 G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) : 41 _time_slice(time_slice), 42 _max_gc_time(max_gc_time) { } 43 44 G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) : 45 G1MMUTracker(time_slice, max_gc_time), 46 _head_index(0), 47 _tail_index(trim_index(_head_index+1)), 48 _no_entries(0) { } 49 50 void G1MMUTrackerQueue::remove_expired_entries(double current_time) { 51 double limit = current_time - _time_slice; 52 while (_no_entries > 0) { 53 if (is_double_geq(limit, _array[_tail_index].end_time())) { 54 _tail_index = trim_index(_tail_index + 1); 55 --_no_entries; 56 } else 57 return; 58 } 59 guarantee(_no_entries == 0, "should have no entries in the array"); 60 } 61 62 double G1MMUTrackerQueue::calculate_gc_time(double current_time) { 63 double gc_time = 0.0; 64 double limit = current_time - _time_slice; 65 for (int i = 0; i < _no_entries; ++i) { 66 int index = trim_index(_tail_index + i); 67 G1MMUTrackerQueueElem *elem = &_array[index]; 68 if (elem->end_time() > limit) { 69 if (elem->start_time() > limit) 70 gc_time += elem->duration(); 71 else 72 gc_time += elem->end_time() - limit; 73 } 74 } 75 return gc_time; 76 } 77 78 void G1MMUTrackerQueue::add_pause(double start, double end, bool gc_thread) { 79 double longest_allowed = longest_pause_internal(start); 80 if (longest_allowed < 0.0) 81 longest_allowed = 0.0; 82 double duration = end - start; 83 84 remove_expired_entries(end); 85 if (_no_entries == QueueLength) { 86 // OK, we've filled up the queue. There are a few ways 87 // of dealing with this "gracefully" 88 // increase the array size (:-) 89 // remove the oldest entry (this might allow more GC time for 90 // the time slice than what's allowed) - this is what we 91 // currently do 92 // consolidate the two entries with the minimum gap between them 93 // (this might allow less GC time than what's allowed) 94 95 // In the case where ScavengeALot is true, such overflow is not 96 // uncommon; in such cases, we can, without much loss of precision 97 // or performance (we are GC'ing most of the time anyway!), 98 // simply overwrite the oldest entry in the tracker. 99 100 if (G1PolicyVerbose > 1) { 101 warning("MMU Tracker Queue overflow. Replacing earliest entry."); 102 } 103 104 _head_index = trim_index(_head_index + 1); 105 assert(_head_index == _tail_index, "Because we have a full circular buffer"); 106 _tail_index = trim_index(_tail_index + 1); 107 } else { 108 _head_index = trim_index(_head_index + 1); 109 ++_no_entries; 110 } 111 _array[_head_index] = G1MMUTrackerQueueElem(start, end); 112 } 113 114 // basically the _internal call does not remove expired entries 115 // this is for trying things out in the future and a couple 116 // of other places (debugging) 117 118 double G1MMUTrackerQueue::longest_pause(double current_time) { 119 if (_DISABLE_MMU) 120 return _max_gc_time; 121 122 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag); 123 remove_expired_entries(current_time); 124 125 return longest_pause_internal(current_time); 126 } 127 128 double G1MMUTrackerQueue::longest_pause_internal(double current_time) { 129 double target_time = _max_gc_time; 130 131 while( 1 ) { 132 double gc_time = 133 calculate_gc_time(current_time + target_time); 134 double diff = target_time + gc_time - _max_gc_time; 135 if (!is_double_leq_0(diff)) { 136 target_time -= diff; 137 if (is_double_leq_0(target_time)) { 138 target_time = -1.0; 139 break; 140 } 141 } else { 142 break; 143 } 144 } 145 146 return target_time; 147 } 148 149 // basically the _internal call does not remove expired entries 150 // this is for trying things out in the future and a couple 151 // of other places (debugging) 152 153 double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) { 154 if (_DISABLE_MMU) 155 return 0.0; 156 157 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag); 158 remove_expired_entries(current_time); 159 160 return when_internal(current_time, pause_time); 161 } 162 163 double G1MMUTrackerQueue::when_internal(double current_time, 164 double pause_time) { 165 // if the pause is over the maximum, just assume that it's the maximum 166 double adjusted_pause_time = 167 (pause_time > max_gc_time()) ? max_gc_time() : pause_time; 168 double earliest_end = current_time + adjusted_pause_time; 169 double limit = earliest_end - _time_slice; 170 double gc_time = calculate_gc_time(earliest_end); 171 double diff = gc_time + adjusted_pause_time - max_gc_time(); 172 if (is_double_leq_0(diff)) 173 return 0.0; 174 175 int index = _tail_index; 176 while ( 1 ) { 177 G1MMUTrackerQueueElem *elem = &_array[index]; 178 if (elem->end_time() > limit) { 179 if (elem->start_time() > limit) 180 diff -= elem->duration(); 181 else 182 diff -= elem->end_time() - limit; 183 if (is_double_leq_0(diff)) 184 return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time; 185 } 186 index = trim_index(index+1); 187 guarantee(index != trim_index(_head_index + 1), "should not go past head"); 188 } 189 }