1/*
2 * Copyright (c) 2001, 2017, 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/g1/g1MMUTracker.hpp"
27#include "gc/shared/gcTrace.hpp"
28#include "logging/log.hpp"
29#include "runtime/mutexLocker.hpp"
30#include "utilities/ostream.hpp"
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
40G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) :
41 _time_slice(time_slice),
42 _max_gc_time(max_gc_time) { }
43
44G1MMUTrackerQueue::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
50void 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
62double 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
78void G1MMUTrackerQueue::add_pause(double start, double end) {
79 double duration = end - start;
80
81 remove_expired_entries(end);
82 if (_no_entries == QueueLength) {
83 // OK, we've filled up the queue. There are a few ways
84 // of dealing with this "gracefully"
85 // increase the array size (:-)
86 // remove the oldest entry (this might allow more GC time for
87 // the time slice than what's allowed) - this is what we
88 // currently do
89 // consolidate the two entries with the minimum gap between them
90 // (this might allow less GC time than what's allowed)
91
92 // In the case where ScavengeALot is true, such overflow is not
93 // uncommon; in such cases, we can, without much loss of precision
94 // or performance (we are GC'ing most of the time anyway!),
95 // simply overwrite the oldest entry in the tracker.
96
97 _head_index = trim_index(_head_index + 1);
98 assert(_head_index == _tail_index, "Because we have a full circular buffer");
99 _tail_index = trim_index(_tail_index + 1);
100 } else {
101 _head_index = trim_index(_head_index + 1);
102 ++_no_entries;
103 }
104 _array[_head_index] = G1MMUTrackerQueueElem(start, end);
105
106 // Current entry needs to be added before calculating the value
107 double slice_time = calculate_gc_time(end);
108 G1MMUTracer::report_mmu(_time_slice, slice_time, _max_gc_time);
109
110 if (slice_time >= _max_gc_time) {
111 log_info(gc, mmu)("MMU target violated: %.1lfms (%.1lfms/%.1lfms)", slice_time * 1000.0, _max_gc_time * 1000.0, _time_slice * 1000);
112 }
113}
114
115double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) {
116 // if the pause is over the maximum, just assume that it's the maximum
117 double adjusted_pause_time =
118 (pause_time > max_gc_time()) ? max_gc_time() : pause_time;
119 double earliest_end = current_time + adjusted_pause_time;
120 double limit = earliest_end - _time_slice;
121 double gc_time = calculate_gc_time(earliest_end);
122 double diff = gc_time + adjusted_pause_time - max_gc_time();
123 if (is_double_leq_0(diff))
124 return 0.0;
125
126 int index = _tail_index;
127 while ( 1 ) {
128 G1MMUTrackerQueueElem *elem = &_array[index];
129 if (elem->end_time() > limit) {
130 if (elem->start_time() > limit)
131 diff -= elem->duration();
132 else
133 diff -= elem->end_time() - limit;
134 if (is_double_leq_0(diff))
135 return elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time;
136 }
137 index = trim_index(index+1);
138 guarantee(index != trim_index(_head_index + 1), "should not go past head");
139 }
140}
141