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/*
* Copyright (C) 2016-2017 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include "MutatorScheduler.h"
#include <wtf/Seconds.h>
namespace JSC {
class Heap;
// The JSC concurrent GC sometimes stops the world in order to stay ahead of it. These deliberate,
// synthetic pauses ensure that the GC won't have to do one huge pause in order to catch up to the
// retreating wavefront. The scheduler is called "space-time" because it links the amount of time
// that the world is paused for to the amount of space that the world allocated since the GC cycle
// began.
class SpaceTimeMutatorScheduler final : public MutatorScheduler {
public:
SpaceTimeMutatorScheduler(Heap&);
~SpaceTimeMutatorScheduler() final;
State state() const final;
void beginCollection() final;
void didStop() final;
void willResume() final;
void didExecuteConstraints() final;
MonotonicTime timeToStop() final;
MonotonicTime timeToResume() final;
void log() final;
void endCollection() final;
private:
class Snapshot;
friend class Snapshot;
double bytesAllocatedThisCycleImpl();
double bytesSinceBeginningOfCycle(const Snapshot&);
double maxHeadroom();
double headroomFullness(const Snapshot&);
double mutatorUtilization(const Snapshot&);
double collectorUtilization(const Snapshot&);
Seconds elapsedInPeriod(const Snapshot&);
double phase(const Snapshot&);
bool shouldBeResumed(const Snapshot&);
Heap& m_heap;
Seconds m_period;
State m_state { Normal };
double m_bytesAllocatedThisCycleAtTheBeginning { 0 };
double m_bytesAllocatedThisCycleAtTheEnd { 0 };
MonotonicTime m_startTime;
};
} // namespace JSC