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comparison src/share/vm/gc_implementation/g1/g1MMUTracker.cpp @ 342:37f87013dfd8

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6711316: Open source the Garbage-First garbage collector Summary: First mercurial integration of the code for the Garbage-First garbage collector. Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr
author ysr
date Thu, 05 Jun 2008 15:57:56 -0700
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children e1fdf4fd34dc
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189:0b27f3512f9e 342:37f87013dfd8
1 /*
2 * Copyright 2001-2007 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 */
24
25 #include "incls/_precompiled.incl"
26 #include "incls/_g1MMUTracker.cpp.incl"
27
28 #define _DISABLE_MMU 0
29
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))
35
36 /***** ALL TIMES ARE IN SECS!!!!!!! *****/
37
38 G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) :
39 _time_slice(time_slice),
40 _max_gc_time(max_gc_time),
41 _conc_overhead_time_sec(0.0) { }
42
43 void
44 G1MMUTracker::update_conc_overhead(double conc_overhead) {
45 double conc_overhead_time_sec = _time_slice * conc_overhead;
46 if (conc_overhead_time_sec > 0.9 * _max_gc_time) {
47 // We are screwed, as we only seem to have <10% of the soft
48 // real-time goal available for pauses. Let's admit defeat and
49 // allow something more generous as a pause target.
50 conc_overhead_time_sec = 0.75 * _max_gc_time;
51 }
52
53 _conc_overhead_time_sec = conc_overhead_time_sec;
54 }
55
56 G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) :
57 G1MMUTracker(time_slice, max_gc_time),
58 _head_index(0),
59 _tail_index(trim_index(_head_index+1)),
60 _no_entries(0) { }
61
62 void G1MMUTrackerQueue::remove_expired_entries(double current_time) {
63 double limit = current_time - _time_slice;
64 while (_no_entries > 0) {
65 if (is_double_geq(limit, _array[_tail_index].end_time())) {
66 _tail_index = trim_index(_tail_index + 1);
67 --_no_entries;
68 } else
69 return;
70 }
71 guarantee(_no_entries == 0, "should have no entries in the array");
72 }
73
74 double G1MMUTrackerQueue::calculate_gc_time(double current_time) {
75 double gc_time = 0.0;
76 double limit = current_time - _time_slice;
77 for (int i = 0; i < _no_entries; ++i) {
78 int index = trim_index(_tail_index + i);
79 G1MMUTrackerQueueElem *elem = &_array[index];
80 if (elem->end_time() > limit) {
81 if (elem->start_time() > limit)
82 gc_time += elem->duration();
83 else
84 gc_time += elem->end_time() - limit;
85 }
86 }
87 return gc_time;
88 }
89
90 void G1MMUTrackerQueue::add_pause(double start, double end, bool gc_thread) {
91 double longest_allowed = longest_pause_internal(start);
92 if (longest_allowed < 0.0)
93 longest_allowed = 0.0;
94 double duration = end - start;
95
96 remove_expired_entries(end);
97 if (_no_entries == QueueLength) {
98 // OK, right now when we fill up we bomb out
99 // there are a few ways of dealing with this "gracefully"
100 // increase the array size (:-)
101 // remove the oldest entry (this might allow more GC time for
102 // the time slice than what's allowed)
103 // concolidate the two entries with the minimum gap between them
104 // (this mighte allow less GC time than what's allowed)
105 guarantee(0, "array full, currently we can't recover");
106 }
107 _head_index = trim_index(_head_index + 1);
108 ++_no_entries;
109 _array[_head_index] = G1MMUTrackerQueueElem(start, end);
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::longest_pause(double current_time) {
117 if (_DISABLE_MMU)
118 return _max_gc_time;
119
120 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
121 remove_expired_entries(current_time);
122
123 return longest_pause_internal(current_time);
124 }
125
126 double G1MMUTrackerQueue::longest_pause_internal(double current_time) {
127 double target_time = _max_gc_time;
128
129 while( 1 ) {
130 double gc_time =
131 calculate_gc_time(current_time + target_time) + _conc_overhead_time_sec;
132 double diff = target_time + gc_time - _max_gc_time;
133 if (!is_double_leq_0(diff)) {
134 target_time -= diff;
135 if (is_double_leq_0(target_time)) {
136 target_time = -1.0;
137 break;
138 }
139 } else {
140 break;
141 }
142 }
143
144 return target_time;
145 }
146
147 // basically the _internal call does not remove expired entries
148 // this is for trying things out in the future and a couple
149 // of other places (debugging)
150
151 double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) {
152 if (_DISABLE_MMU)
153 return 0.0;
154
155 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
156 remove_expired_entries(current_time);
157
158 return when_internal(current_time, pause_time);
159 }
160
161 double G1MMUTrackerQueue::when_internal(double current_time,
162 double pause_time) {
163 // if the pause is over the maximum, just assume that it's the maximum
164 double adjusted_pause_time =
165 (pause_time > max_gc_time()) ? max_gc_time() : pause_time;
166 double earliest_end = current_time + adjusted_pause_time;
167 double limit = earliest_end - _time_slice;
168 double gc_time = calculate_gc_time(earliest_end);
169 double diff = gc_time + adjusted_pause_time - max_gc_time();
170 if (is_double_leq_0(diff))
171 return 0.0;
172
173 int index = _tail_index;
174 while ( 1 ) {
175 G1MMUTrackerQueueElem *elem = &_array[index];
176 if (elem->end_time() > limit) {
177 if (elem->start_time() > limit)
178 diff -= elem->duration();
179 else
180 diff -= elem->end_time() - limit;
181 if (is_double_leq_0(diff))
182 return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time;
183 }
184 index = trim_index(index+1);
185 guarantee(index != trim_index(_head_index + 1), "should not go past head");
186 }
187 }