Tue, 26 Jan 2010 16:52:29 -0800
6920090: G1: Disable ReduceInitialCardMarks at least until 6920109 is fixed
Summary: G1 now answers "no" to the query can_elide_initializing_store_barrier() in the product build. A debug flag allows alternate behaviour in debug builds.
Reviewed-by: iveresov, tonyp
1 /*
2 * Copyright 2001-2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 #include "incls/_precompiled.incl"
26 #include "incls/_g1MMUTracker.cpp.incl"
28 #define _DISABLE_MMU 0
30 // can't rely on comparing doubles with tolerating a small margin for error
31 #define SMALL_MARGIN 0.0000001
32 #define is_double_leq_0(_value) ( (_value) < SMALL_MARGIN )
33 #define is_double_leq(_val1, _val2) is_double_leq_0((_val1) - (_val2))
34 #define is_double_geq(_val1, _val2) is_double_leq_0((_val2) - (_val1))
36 /***** ALL TIMES ARE IN SECS!!!!!!! *****/
38 G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) :
39 _time_slice(time_slice),
40 _max_gc_time(max_gc_time) { }
42 G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) :
43 G1MMUTracker(time_slice, max_gc_time),
44 _head_index(0),
45 _tail_index(trim_index(_head_index+1)),
46 _no_entries(0) { }
48 void G1MMUTrackerQueue::remove_expired_entries(double current_time) {
49 double limit = current_time - _time_slice;
50 while (_no_entries > 0) {
51 if (is_double_geq(limit, _array[_tail_index].end_time())) {
52 _tail_index = trim_index(_tail_index + 1);
53 --_no_entries;
54 } else
55 return;
56 }
57 guarantee(_no_entries == 0, "should have no entries in the array");
58 }
60 double G1MMUTrackerQueue::calculate_gc_time(double current_time) {
61 double gc_time = 0.0;
62 double limit = current_time - _time_slice;
63 for (int i = 0; i < _no_entries; ++i) {
64 int index = trim_index(_tail_index + i);
65 G1MMUTrackerQueueElem *elem = &_array[index];
66 if (elem->end_time() > limit) {
67 if (elem->start_time() > limit)
68 gc_time += elem->duration();
69 else
70 gc_time += elem->end_time() - limit;
71 }
72 }
73 return gc_time;
74 }
76 void G1MMUTrackerQueue::add_pause(double start, double end, bool gc_thread) {
77 double longest_allowed = longest_pause_internal(start);
78 if (longest_allowed < 0.0)
79 longest_allowed = 0.0;
80 double duration = end - start;
82 remove_expired_entries(end);
83 if (_no_entries == QueueLength) {
84 // OK, right now when we fill up we bomb out
85 // there are a few ways 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)
89 // consolidate the two entries with the minimum gap between them
90 // (this might allow less GC time than what's allowed)
91 guarantee(NOT_PRODUCT(ScavengeALot ||) G1ForgetfulMMUTracker,
92 "array full, currently we can't recover unless +G1ForgetfulMMUTracker");
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: this
97 // is also the behaviour when G1ForgetfulMMUTracker is enabled.
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 }
108 // basically the _internal call does not remove expired entries
109 // this is for trying things out in the future and a couple
110 // of other places (debugging)
112 double G1MMUTrackerQueue::longest_pause(double current_time) {
113 if (_DISABLE_MMU)
114 return _max_gc_time;
116 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
117 remove_expired_entries(current_time);
119 return longest_pause_internal(current_time);
120 }
122 double G1MMUTrackerQueue::longest_pause_internal(double current_time) {
123 double target_time = _max_gc_time;
125 while( 1 ) {
126 double gc_time =
127 calculate_gc_time(current_time + target_time);
128 double diff = target_time + gc_time - _max_gc_time;
129 if (!is_double_leq_0(diff)) {
130 target_time -= diff;
131 if (is_double_leq_0(target_time)) {
132 target_time = -1.0;
133 break;
134 }
135 } else {
136 break;
137 }
138 }
140 return target_time;
141 }
143 // basically the _internal call does not remove expired entries
144 // this is for trying things out in the future and a couple
145 // of other places (debugging)
147 double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) {
148 if (_DISABLE_MMU)
149 return 0.0;
151 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
152 remove_expired_entries(current_time);
154 return when_internal(current_time, pause_time);
155 }
157 double G1MMUTrackerQueue::when_internal(double current_time,
158 double pause_time) {
159 // if the pause is over the maximum, just assume that it's the maximum
160 double adjusted_pause_time =
161 (pause_time > max_gc_time()) ? max_gc_time() : pause_time;
162 double earliest_end = current_time + adjusted_pause_time;
163 double limit = earliest_end - _time_slice;
164 double gc_time = calculate_gc_time(earliest_end);
165 double diff = gc_time + adjusted_pause_time - max_gc_time();
166 if (is_double_leq_0(diff))
167 return 0.0;
169 int index = _tail_index;
170 while ( 1 ) {
171 G1MMUTrackerQueueElem *elem = &_array[index];
172 if (elem->end_time() > limit) {
173 if (elem->start_time() > limit)
174 diff -= elem->duration();
175 else
176 diff -= elem->end_time() - limit;
177 if (is_double_leq_0(diff))
178 return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time;
179 }
180 index = trim_index(index+1);
181 guarantee(index != trim_index(_head_index + 1), "should not go past head");
182 }
183 }