1 /*
2 * Copyright (c) 2001, 2009, 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 "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
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) { }
47
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 }
59
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 }
75
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;
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 if (G1PolicyVerbose > 1) {
99 warning("MMU Tracker Queue overflow. Replacing earliest entry.");
100 }
101
102 _head_index = trim_index(_head_index + 1);
103 assert(_head_index == _tail_index, "Because we have a full circular buffer");
104 _tail_index = trim_index(_tail_index + 1);
105 } else {
106 _head_index = trim_index(_head_index + 1);
107 ++_no_entries;
108 }
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);
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 }