1 /* 2 * Copyright (c) 2001, 2015, 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/g1/g1MMUTracker.hpp" 27 #include "gc/shared/gcTrace.hpp" 28 #include "runtime/mutexLocker.hpp" 29 #include "utilities/ostream.hpp" 30 31 #define _DISABLE_MMU 0 32 33 // can't rely on comparing doubles with tolerating a small margin for error 34 #define SMALL_MARGIN 0.0000001 35 #define is_double_leq_0(_value) ( (_value) < SMALL_MARGIN ) 36 #define is_double_leq(_val1, _val2) is_double_leq_0((_val1) - (_val2)) 37 #define is_double_geq(_val1, _val2) is_double_leq_0((_val2) - (_val1)) 38 39 /***** ALL TIMES ARE IN SECS!!!!!!! *****/ 40 41 G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) : 42 _time_slice(time_slice), 43 _max_gc_time(max_gc_time) { } 44 45 G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) : 46 G1MMUTracker(time_slice, max_gc_time), 47 _head_index(0), 48 _tail_index(trim_index(_head_index+1)), 49 _no_entries(0) { } 50 51 void G1MMUTrackerQueue::remove_expired_entries(double current_time) { 52 double limit = current_time - _time_slice; 53 while (_no_entries > 0) { 54 if (is_double_geq(limit, _array[_tail_index].end_time())) { 55 _tail_index = trim_index(_tail_index + 1); 56 --_no_entries; 57 } else 58 return; 59 } 60 guarantee(_no_entries == 0, "should have no entries in the array"); 61 } 62 63 double G1MMUTrackerQueue::calculate_gc_time(double current_time) { 64 double gc_time = 0.0; 65 double limit = current_time - _time_slice; 66 for (int i = 0; i < _no_entries; ++i) { 67 int index = trim_index(_tail_index + i); 68 G1MMUTrackerQueueElem *elem = &_array[index]; 69 if (elem->end_time() > limit) { 70 if (elem->start_time() > limit) 71 gc_time += elem->duration(); 72 else 73 gc_time += elem->end_time() - limit; 74 } 75 } 76 return gc_time; 77 } 78 79 void G1MMUTrackerQueue::add_pause(double start, double end) { 80 double duration = end - start; 81 82 remove_expired_entries(end); 83 if (_no_entries == QueueLength) { 84 // OK, we've filled up the queue. There are a few ways 85 // of dealing with this "gracefully" 86 // increase the array size (:-) 87 // remove the oldest entry (this might allow more GC time for 88 // the time slice than what's allowed) - this is what we 89 // currently do 90 // consolidate the two entries with the minimum gap between them 91 // (this might allow less GC time than what's allowed) 92 93 // In the case where ScavengeALot is true, such overflow is not 94 // uncommon; in such cases, we can, without much loss of precision 95 // or performance (we are GC'ing most of the time anyway!), 96 // simply overwrite the oldest entry in the tracker. 97 98 _head_index = trim_index(_head_index + 1); 99 assert(_head_index == _tail_index, "Because we have a full circular buffer"); 100 _tail_index = trim_index(_tail_index + 1); 101 } else { 102 _head_index = trim_index(_head_index + 1); 103 ++_no_entries; 104 } 105 _array[_head_index] = G1MMUTrackerQueueElem(start, end); 106 107 // Current entry needs to be added before calculating the value 108 double slice_time = calculate_gc_time(end); 109 G1MMUTracer::report_mmu(_time_slice, slice_time, _max_gc_time); 110 } 111 112 // basically the _internal call does not remove expired entries 113 // this is for trying things out in the future and a couple 114 // of other places (debugging) 115 116 double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) { 117 if (_DISABLE_MMU) 118 return 0.0; 119 120 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag); 121 remove_expired_entries(current_time); 122 123 return when_internal(current_time, pause_time); 124 } 125 126 double G1MMUTrackerQueue::when_internal(double current_time, 127 double pause_time) { 128 // if the pause is over the maximum, just assume that it's the maximum 129 double adjusted_pause_time = 130 (pause_time > max_gc_time()) ? max_gc_time() : pause_time; 131 double earliest_end = current_time + adjusted_pause_time; 132 double limit = earliest_end - _time_slice; 133 double gc_time = calculate_gc_time(earliest_end); 134 double diff = gc_time + adjusted_pause_time - max_gc_time(); 135 if (is_double_leq_0(diff)) 136 return 0.0; 137 138 int index = _tail_index; 139 while ( 1 ) { 140 G1MMUTrackerQueueElem *elem = &_array[index]; 141 if (elem->end_time() > limit) { 142 if (elem->start_time() > limit) 143 diff -= elem->duration(); 144 else 145 diff -= elem->end_time() - limit; 146 if (is_double_leq_0(diff)) 147 return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time; 148 } 149 index = trim_index(index+1); 150 guarantee(index != trim_index(_head_index + 1), "should not go past head"); 151 } 152 }