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.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_G1_G1MMUTRACKER_HPP
26 #define SHARE_VM_GC_G1_G1MMUTRACKER_HPP
27
28 #include "memory/allocation.hpp"
29 #include "utilities/debug.hpp"
30
31 // Keeps track of the GC work and decides when it is OK to do GC work
32 // and for how long so that the MMU invariants are maintained.
33
34 /***** ALL TIMES ARE IN SECS!!!!!!! *****/
35
36 // this is the "interface"
37 class G1MMUTracker: public CHeapObj<mtGC> {
38 protected:
39 double _time_slice;
40 double _max_gc_time; // this is per time slice
41
42 public:
43 G1MMUTracker(double time_slice, double max_gc_time);
44
45 virtual void add_pause(double start, double end, bool gc_thread) = 0;
46 virtual double when_sec(double current_time, double pause_time) = 0;
47
48 double max_gc_time() {
49 return _max_gc_time;
50 }
51
52 inline bool now_max_gc(double current_time) {
53 return when_sec(current_time, max_gc_time()) < 0.00001;
54 }
55
56 inline double when_max_gc_sec(double current_time) {
57 return when_sec(current_time, max_gc_time());
58 }
59
60 inline jlong when_max_gc_ms(double current_time) {
61 double when = when_max_gc_sec(current_time);
62 return (jlong) (when * 1000.0);
63 }
64
65 inline jlong when_ms(double current_time, double pause_time) {
66 double when = when_sec(current_time, pause_time);
67 return (jlong) (when * 1000.0);
68 }
69 };
70
71 class G1MMUTrackerQueueElem VALUE_OBJ_CLASS_SPEC {
72 private:
73 double _start_time;
74 double _end_time;
75
76 public:
77 inline double start_time() { return _start_time; }
78 inline double end_time() { return _end_time; }
79 inline double duration() { return _end_time - _start_time; }
80
81 G1MMUTrackerQueueElem() {
82 _start_time = 0.0;
83 _end_time = 0.0;
84 }
85
86 G1MMUTrackerQueueElem(double start_time, double end_time) {
87 _start_time = start_time;
88 _end_time = end_time;
89 }
90 };
91
92 // this is an implementation of the MMUTracker using a (fixed-size) queue
93 // that keeps track of all the recent pause times
94 class G1MMUTrackerQueue: public G1MMUTracker {
95 private:
96 enum PrivateConstants {
97 QueueLength = 64
98 };
99
100 // The array keeps track of all the pauses that fall within a time
101 // slice (the last time slice during which pauses took place).
102 // The data structure implemented is a circular queue.
103 // Head "points" to the most recent addition, tail to the oldest one.
104 // The array is of fixed size and I don't think we'll need more than
105 // two or three entries with the current behavior of G1 pauses.
106 // If the array is full, an easy fix is to look for the pauses with
107 // the shortest gap between them and consolidate them.
108 // For now, we have taken the expedient alternative of forgetting
109 // the oldest entry in the event that +G1UseFixedWindowMMUTracker, thus
110 // potentially violating MMU specs for some time thereafter.
111
112 G1MMUTrackerQueueElem _array[QueueLength];
113 int _head_index;
114 int _tail_index;
115 int _no_entries;
116
117 inline int trim_index(int index) {
118 return (index + QueueLength) % QueueLength;
119 }
120
121 void remove_expired_entries(double current_time);
122 double calculate_gc_time(double current_time);
123
124 double when_internal(double current_time, double pause_time);
125
126 public:
127 G1MMUTrackerQueue(double time_slice, double max_gc_time);
128
129 virtual void add_pause(double start, double end, bool gc_thread);
130
131 virtual double when_sec(double current_time, double pause_time);
132 };
133
134 #endif // SHARE_VM_GC_G1_G1MMUTRACKER_HPP