1/*
2 * Copyright (C) 2016-2017 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
31namespace JSC {
32
33class Heap;
34
35// The JSC concurrent GC sometimes stops the world in order to stay ahead of it. These deliberate,
36// synthetic pauses ensure that the GC won't have to do one huge pause in order to catch up to the
37// retreating wavefront. The scheduler is called "space-time" because it links the amount of time
38// that the world is paused for to the amount of space that the world allocated since the GC cycle
39// began.
40
41class SpaceTimeMutatorScheduler : public MutatorScheduler {
42public:
43 SpaceTimeMutatorScheduler(Heap&);
44 ~SpaceTimeMutatorScheduler();
45
46 State state() const override;
47
48 void beginCollection() override;
49
50 void didStop() override;
51 void willResume() override;
52 void didExecuteConstraints() override;
53
54 MonotonicTime timeToStop() override;
55 MonotonicTime timeToResume() override;
56
57 void log() override;
58
59 void endCollection() override;
60
61private:
62 class Snapshot;
63 friend class Snapshot;
64
65 double bytesAllocatedThisCycleImpl();
66
67 double bytesSinceBeginningOfCycle(const Snapshot&);
68 double maxHeadroom();
69 double headroomFullness(const Snapshot&);
70 double mutatorUtilization(const Snapshot&);
71 double collectorUtilization(const Snapshot&);
72 Seconds elapsedInPeriod(const Snapshot&);
73 double phase(const Snapshot&);
74 bool shouldBeResumed(const Snapshot&);
75
76 Heap& m_heap;
77 Seconds m_period;
78 State m_state { Normal };
79
80 double m_bytesAllocatedThisCycleAtTheBeginning { 0 };
81 double m_bytesAllocatedThisCycleAtTheEnd { 0 };
82 MonotonicTime m_startTime;
83};
84
85} // namespace JSC
86
87