1/*
2 * Copyright (C) 2017 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28#include "MutatorScheduler.h"
29#include <wtf/Seconds.h>
30#include <wtf/WeakRandom.h>
31
32namespace JSC {
33
34class Heap;
35
36// The JSC concurrent GC sometimes stops the world in order to stay ahead of it. These deliberate,
37// synthetic pauses ensure that the GC won't have to do one huge pause in order to catch up to the
38// retreating wavefront. The scheduler is called "space-time" because it links the amount of time
39// that the world is paused for to the amount of space that the world allocated since the GC cycle
40// began.
41
42class StochasticSpaceTimeMutatorScheduler : public MutatorScheduler {
43public:
44 StochasticSpaceTimeMutatorScheduler(Heap&);
45 ~StochasticSpaceTimeMutatorScheduler();
46
47 State state() const override;
48
49 void beginCollection() override;
50
51 void didStop() override;
52 void willResume() override;
53 void didReachTermination() override;
54 void didExecuteConstraints() override;
55 void synchronousDrainingDidStall() override;
56
57 MonotonicTime timeToStop() override;
58 MonotonicTime timeToResume() override;
59
60 void log() override;
61
62 void endCollection() override;
63
64private:
65 class Snapshot;
66 friend class Snapshot;
67
68 double bytesAllocatedThisCycleImpl();
69
70 double bytesSinceBeginningOfCycle(const Snapshot&);
71 double maxHeadroom();
72 double headroomFullness(const Snapshot&);
73 double mutatorUtilization(const Snapshot&);
74
75 Heap& m_heap;
76 State m_state { Normal };
77
78 WeakRandom m_random;
79
80 Seconds m_minimumPause;
81 double m_pauseScale;
82 Seconds m_targetPause;
83
84 double m_bytesAllocatedThisCycleAtTheBeginning { 0 };
85 double m_bytesAllocatedThisCycleAtTheEnd { 0 };
86
87 MonotonicTime m_beforeConstraints;
88 MonotonicTime m_plannedResumeTime;
89};
90
91} // namespace JSC
92
93