1 /*
2 * Copyright (c) 2001, 2015, 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.
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1MMUTRACKER_HPP
26 #define SHARE_VM_GC_G1_G1MMUTRACKER_HPP
27
28 #include "gc/shared/gcId.hpp"
29 #include "memory/allocation.hpp"
30 #include "utilities/debug.hpp"
31
32 // Keeps track of the GC work and decides when it is OK to do GC work
33 // and for how long so that the MMU invariants are maintained.
34
35 /***** ALL TIMES ARE IN SECS!!!!!!! *****/
36
37 // this is the "interface"
38 class G1MMUTracker: public CHeapObj<mtGC> {
39 protected:
40 double _time_slice;
41 double _max_gc_time; // this is per time slice
42
43 public:
44 G1MMUTracker(double time_slice, double max_gc_time);
45
46 virtual void add_pause(double start, double end, const GCId& gcId) = 0;
47 virtual double when_sec(double current_time, double pause_time) = 0;
48
49 double max_gc_time() {
50 return _max_gc_time;
51 }
52
53 inline bool now_max_gc(double current_time) {
54 return when_sec(current_time, max_gc_time()) < 0.00001;
55 }
56
57 inline double when_max_gc_sec(double current_time) {
58 return when_sec(current_time, max_gc_time());
59 }
60
61 inline jlong when_max_gc_ms(double current_time) {
62 double when = when_max_gc_sec(current_time);
63 return (jlong) (when * 1000.0);
64 }
65
66 inline jlong when_ms(double current_time, double pause_time) {
67 double when = when_sec(current_time, pause_time);
68 return (jlong) (when * 1000.0);
69 }
70 };
71
72 class G1MMUTrackerQueueElem VALUE_OBJ_CLASS_SPEC {
73 private:
74 double _start_time;
75 double _end_time;
76
77 public:
78 inline double start_time() { return _start_time; }
79 inline double end_time() { return _end_time; }
80 inline double duration() { return _end_time - _start_time; }
81
82 G1MMUTrackerQueueElem() {
83 _start_time = 0.0;
84 _end_time = 0.0;
85 }
86
87 G1MMUTrackerQueueElem(double start_time, double end_time) {
88 _start_time = start_time;
89 _end_time = end_time;
90 }
91 };
92
93 // this is an implementation of the MMUTracker using a (fixed-size) queue
94 // that keeps track of all the recent pause times
95 class G1MMUTrackerQueue: public G1MMUTracker {
96 private:
97 enum PrivateConstants {
98 QueueLength = 64
99 };
100
101 // The array keeps track of all the pauses that fall within a time
102 // slice (the last time slice during which pauses took place).
103 // The data structure implemented is a circular queue.
104 // Head "points" to the most recent addition, tail to the oldest one.
105 // The array is of fixed size and I don't think we'll need more than
106 // two or three entries with the current behavior of G1 pauses.
107 // If the array is full, an easy fix is to look for the pauses with
108 // the shortest gap between them and consolidate them.
109 // For now, we have taken the expedient alternative of forgetting
110 // the oldest entry in the event that +G1UseFixedWindowMMUTracker, thus
111 // potentially violating MMU specs for some time thereafter.
112
113 G1MMUTrackerQueueElem _array[QueueLength];
114 int _head_index;
115 int _tail_index;
116 int _no_entries;
117
118 inline int trim_index(int index) {
119 return (index + QueueLength) % QueueLength;
120 }
121
122 void remove_expired_entries(double current_time);
123 double calculate_gc_time(double current_time);
124
125 double when_internal(double current_time, double pause_time);
126
127 public:
128 G1MMUTrackerQueue(double time_slice, double max_gc_time);
129
130 virtual void add_pause(double start, double end, const GCId& gcId);
131
132 virtual double when_sec(double current_time, double pause_time);
133 };
134
135 #endif // SHARE_VM_GC_G1_G1MMUTRACKER_HPP