Tue, 13 Apr 2010 13:52:10 -0700
6858496: Clear all SoftReferences before an out-of-memory due to GC overhead limit.
Summary: Ensure a full GC that clears SoftReferences before throwing an out-of-memory
Reviewed-by: ysr, jcoomes
ysr@777 | 1 | /* |
xdono@1383 | 2 | * Copyright 2001-2009 Sun Microsystems, Inc. All Rights Reserved. |
ysr@777 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
ysr@777 | 4 | * |
ysr@777 | 5 | * This code is free software; you can redistribute it and/or modify it |
ysr@777 | 6 | * under the terms of the GNU General Public License version 2 only, as |
ysr@777 | 7 | * published by the Free Software Foundation. |
ysr@777 | 8 | * |
ysr@777 | 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
ysr@777 | 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
ysr@777 | 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
ysr@777 | 12 | * version 2 for more details (a copy is included in the LICENSE file that |
ysr@777 | 13 | * accompanied this code). |
ysr@777 | 14 | * |
ysr@777 | 15 | * You should have received a copy of the GNU General Public License version |
ysr@777 | 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
ysr@777 | 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
ysr@777 | 18 | * |
ysr@777 | 19 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
ysr@777 | 20 | * CA 95054 USA or visit www.sun.com if you need additional information or |
ysr@777 | 21 | * have any questions. |
ysr@777 | 22 | * |
ysr@777 | 23 | */ |
ysr@777 | 24 | |
ysr@777 | 25 | #include "incls/_precompiled.incl" |
ysr@777 | 26 | #include "incls/_g1MMUTracker.cpp.incl" |
ysr@777 | 27 | |
ysr@777 | 28 | #define _DISABLE_MMU 0 |
ysr@777 | 29 | |
ysr@777 | 30 | // can't rely on comparing doubles with tolerating a small margin for error |
ysr@777 | 31 | #define SMALL_MARGIN 0.0000001 |
ysr@777 | 32 | #define is_double_leq_0(_value) ( (_value) < SMALL_MARGIN ) |
ysr@777 | 33 | #define is_double_leq(_val1, _val2) is_double_leq_0((_val1) - (_val2)) |
ysr@777 | 34 | #define is_double_geq(_val1, _val2) is_double_leq_0((_val2) - (_val1)) |
ysr@777 | 35 | |
ysr@777 | 36 | /***** ALL TIMES ARE IN SECS!!!!!!! *****/ |
ysr@777 | 37 | |
ysr@777 | 38 | G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) : |
ysr@777 | 39 | _time_slice(time_slice), |
tonyp@1371 | 40 | _max_gc_time(max_gc_time) { } |
ysr@777 | 41 | |
ysr@777 | 42 | G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) : |
ysr@777 | 43 | G1MMUTracker(time_slice, max_gc_time), |
ysr@777 | 44 | _head_index(0), |
ysr@777 | 45 | _tail_index(trim_index(_head_index+1)), |
ysr@777 | 46 | _no_entries(0) { } |
ysr@777 | 47 | |
ysr@777 | 48 | void G1MMUTrackerQueue::remove_expired_entries(double current_time) { |
ysr@777 | 49 | double limit = current_time - _time_slice; |
ysr@777 | 50 | while (_no_entries > 0) { |
ysr@777 | 51 | if (is_double_geq(limit, _array[_tail_index].end_time())) { |
ysr@777 | 52 | _tail_index = trim_index(_tail_index + 1); |
ysr@777 | 53 | --_no_entries; |
ysr@777 | 54 | } else |
ysr@777 | 55 | return; |
ysr@777 | 56 | } |
ysr@777 | 57 | guarantee(_no_entries == 0, "should have no entries in the array"); |
ysr@777 | 58 | } |
ysr@777 | 59 | |
ysr@777 | 60 | double G1MMUTrackerQueue::calculate_gc_time(double current_time) { |
ysr@777 | 61 | double gc_time = 0.0; |
ysr@777 | 62 | double limit = current_time - _time_slice; |
ysr@777 | 63 | for (int i = 0; i < _no_entries; ++i) { |
ysr@777 | 64 | int index = trim_index(_tail_index + i); |
ysr@777 | 65 | G1MMUTrackerQueueElem *elem = &_array[index]; |
ysr@777 | 66 | if (elem->end_time() > limit) { |
ysr@777 | 67 | if (elem->start_time() > limit) |
ysr@777 | 68 | gc_time += elem->duration(); |
ysr@777 | 69 | else |
ysr@777 | 70 | gc_time += elem->end_time() - limit; |
ysr@777 | 71 | } |
ysr@777 | 72 | } |
ysr@777 | 73 | return gc_time; |
ysr@777 | 74 | } |
ysr@777 | 75 | |
ysr@777 | 76 | void G1MMUTrackerQueue::add_pause(double start, double end, bool gc_thread) { |
ysr@777 | 77 | double longest_allowed = longest_pause_internal(start); |
ysr@777 | 78 | if (longest_allowed < 0.0) |
ysr@777 | 79 | longest_allowed = 0.0; |
ysr@777 | 80 | double duration = end - start; |
ysr@777 | 81 | |
ysr@777 | 82 | remove_expired_entries(end); |
ysr@777 | 83 | if (_no_entries == QueueLength) { |
ysr@777 | 84 | // OK, right now when we fill up we bomb out |
ysr@777 | 85 | // there are a few ways of dealing with this "gracefully" |
ysr@777 | 86 | // increase the array size (:-) |
ysr@777 | 87 | // remove the oldest entry (this might allow more GC time for |
ysr@777 | 88 | // the time slice than what's allowed) |
ysr@1523 | 89 | // consolidate the two entries with the minimum gap between them |
ysr@1523 | 90 | // (this might allow less GC time than what's allowed) |
tonyp@1717 | 91 | guarantee(NOT_PRODUCT(ScavengeALot ||) G1UseFixedWindowMMUTracker, |
tonyp@1717 | 92 | "array full, currently we can't recover unless +G1UseFixedWindowMMUTracker"); |
ysr@1523 | 93 | // In the case where ScavengeALot is true, such overflow is not |
ysr@1523 | 94 | // uncommon; in such cases, we can, without much loss of precision |
ysr@1523 | 95 | // or performance (we are GC'ing most of the time anyway!), |
ysr@1523 | 96 | // simply overwrite the oldest entry in the tracker: this |
tonyp@1717 | 97 | // is also the behaviour when G1UseFixedWindowMMUTracker is enabled. |
ysr@1523 | 98 | _head_index = trim_index(_head_index + 1); |
ysr@1523 | 99 | assert(_head_index == _tail_index, "Because we have a full circular buffer"); |
ysr@1523 | 100 | _tail_index = trim_index(_tail_index + 1); |
ysr@1523 | 101 | } else { |
ysr@1523 | 102 | _head_index = trim_index(_head_index + 1); |
ysr@1523 | 103 | ++_no_entries; |
ysr@777 | 104 | } |
ysr@777 | 105 | _array[_head_index] = G1MMUTrackerQueueElem(start, end); |
ysr@777 | 106 | } |
ysr@777 | 107 | |
ysr@777 | 108 | // basically the _internal call does not remove expired entries |
ysr@777 | 109 | // this is for trying things out in the future and a couple |
ysr@777 | 110 | // of other places (debugging) |
ysr@777 | 111 | |
ysr@777 | 112 | double G1MMUTrackerQueue::longest_pause(double current_time) { |
ysr@777 | 113 | if (_DISABLE_MMU) |
ysr@777 | 114 | return _max_gc_time; |
ysr@777 | 115 | |
ysr@777 | 116 | MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag); |
ysr@777 | 117 | remove_expired_entries(current_time); |
ysr@777 | 118 | |
ysr@777 | 119 | return longest_pause_internal(current_time); |
ysr@777 | 120 | } |
ysr@777 | 121 | |
ysr@777 | 122 | double G1MMUTrackerQueue::longest_pause_internal(double current_time) { |
ysr@777 | 123 | double target_time = _max_gc_time; |
ysr@777 | 124 | |
ysr@777 | 125 | while( 1 ) { |
ysr@777 | 126 | double gc_time = |
tonyp@1371 | 127 | calculate_gc_time(current_time + target_time); |
ysr@777 | 128 | double diff = target_time + gc_time - _max_gc_time; |
ysr@777 | 129 | if (!is_double_leq_0(diff)) { |
ysr@777 | 130 | target_time -= diff; |
ysr@777 | 131 | if (is_double_leq_0(target_time)) { |
ysr@777 | 132 | target_time = -1.0; |
ysr@777 | 133 | break; |
ysr@777 | 134 | } |
ysr@777 | 135 | } else { |
ysr@777 | 136 | break; |
ysr@777 | 137 | } |
ysr@777 | 138 | } |
ysr@777 | 139 | |
ysr@777 | 140 | return target_time; |
ysr@777 | 141 | } |
ysr@777 | 142 | |
ysr@777 | 143 | // basically the _internal call does not remove expired entries |
ysr@777 | 144 | // this is for trying things out in the future and a couple |
ysr@777 | 145 | // of other places (debugging) |
ysr@777 | 146 | |
ysr@777 | 147 | double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) { |
ysr@777 | 148 | if (_DISABLE_MMU) |
ysr@777 | 149 | return 0.0; |
ysr@777 | 150 | |
ysr@777 | 151 | MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag); |
ysr@777 | 152 | remove_expired_entries(current_time); |
ysr@777 | 153 | |
ysr@777 | 154 | return when_internal(current_time, pause_time); |
ysr@777 | 155 | } |
ysr@777 | 156 | |
ysr@777 | 157 | double G1MMUTrackerQueue::when_internal(double current_time, |
ysr@777 | 158 | double pause_time) { |
ysr@777 | 159 | // if the pause is over the maximum, just assume that it's the maximum |
ysr@777 | 160 | double adjusted_pause_time = |
ysr@777 | 161 | (pause_time > max_gc_time()) ? max_gc_time() : pause_time; |
ysr@777 | 162 | double earliest_end = current_time + adjusted_pause_time; |
ysr@777 | 163 | double limit = earliest_end - _time_slice; |
ysr@777 | 164 | double gc_time = calculate_gc_time(earliest_end); |
ysr@777 | 165 | double diff = gc_time + adjusted_pause_time - max_gc_time(); |
ysr@777 | 166 | if (is_double_leq_0(diff)) |
ysr@777 | 167 | return 0.0; |
ysr@777 | 168 | |
ysr@777 | 169 | int index = _tail_index; |
ysr@777 | 170 | while ( 1 ) { |
ysr@777 | 171 | G1MMUTrackerQueueElem *elem = &_array[index]; |
ysr@777 | 172 | if (elem->end_time() > limit) { |
ysr@777 | 173 | if (elem->start_time() > limit) |
ysr@777 | 174 | diff -= elem->duration(); |
ysr@777 | 175 | else |
ysr@777 | 176 | diff -= elem->end_time() - limit; |
ysr@777 | 177 | if (is_double_leq_0(diff)) |
ysr@777 | 178 | return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time; |
ysr@777 | 179 | } |
ysr@777 | 180 | index = trim_index(index+1); |
ysr@777 | 181 | guarantee(index != trim_index(_head_index + 1), "should not go past head"); |
ysr@777 | 182 | } |
ysr@777 | 183 | } |