1 /*
2 * Copyright (c) 2001, 2011, 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 _head_index = trim_index(_head_index + 1);
101 assert(_head_index == _tail_index, "Because we have a full circular buffer");
102 _tail_index = trim_index(_tail_index + 1);
103 } else {
104 _head_index = trim_index(_head_index + 1);
105 ++_no_entries;
106 }
107 _array[_head_index] = G1MMUTrackerQueueElem(start, end);
108 }
109
110 // basically the _internal call does not remove expired entries
111 // this is for trying things out in the future and a couple
112 // of other places (debugging)
113
114 double G1MMUTrackerQueue::longest_pause(double current_time) {
115 if (_DISABLE_MMU)
116 return _max_gc_time;
117
118 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
119 remove_expired_entries(current_time);
120
121 return longest_pause_internal(current_time);
122 }
123
124 double G1MMUTrackerQueue::longest_pause_internal(double current_time) {
125 double target_time = _max_gc_time;
126
127 while( 1 ) {
128 double gc_time =
129 calculate_gc_time(current_time + target_time);
130 double diff = target_time + gc_time - _max_gc_time;
131 if (!is_double_leq_0(diff)) {
132 target_time -= diff;
133 if (is_double_leq_0(target_time)) {
134 target_time = -1.0;
135 break;
136 }
137 } else {
138 break;
139 }
140 }
141
142 return target_time;
143 }
144
145 // basically the _internal call does not remove expired entries
146 // this is for trying things out in the future and a couple
147 // of other places (debugging)
148
149 double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) {
150 if (_DISABLE_MMU)
151 return 0.0;
152
153 MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);
154 remove_expired_entries(current_time);
155
156 return when_internal(current_time, pause_time);
157 }
158
159 double G1MMUTrackerQueue::when_internal(double current_time,
160 double pause_time) {
161 // if the pause is over the maximum, just assume that it's the maximum
162 double adjusted_pause_time =
163 (pause_time > max_gc_time()) ? max_gc_time() : pause_time;
164 double earliest_end = current_time + adjusted_pause_time;
165 double limit = earliest_end - _time_slice;
166 double gc_time = calculate_gc_time(earliest_end);
167 double diff = gc_time + adjusted_pause_time - max_gc_time();
168 if (is_double_leq_0(diff))
169 return 0.0;
170
171 int index = _tail_index;
172 while ( 1 ) {
173 G1MMUTrackerQueueElem *elem = &_array[index];
174 if (elem->end_time() > limit) {
175 if (elem->start_time() > limit)
176 diff -= elem->duration();
177 else
178 diff -= elem->end_time() - limit;
179 if (is_double_leq_0(diff))
180 return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time;
181 }
182 index = trim_index(index+1);
183 guarantee(index != trim_index(_head_index + 1), "should not go past head");
184 }
185 }