WebKit/Source/JavaScriptCore/heap/GCActivityCallback.cpp at main · WebKit/WebKit · GitHub

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* 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.

* 3. Neither the name of Apple Inc. ("Apple") nor the names of

* its contributors may be used to endorse or promote products derived

* from this software without specific prior written permission.

* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "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 OR ITS 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.

#include "config.h"

#include "GCActivityCallback.h"

#include "HeapInlines.h"

#include "VM.h"

namespace JSC {

bool GCActivityCallback::s_shouldCreateGCTimer = true;

const double timerSlop = 2.0; // Fudge factor to avoid performance cost of resetting timer.

GCActivityCallback::GCActivityCallback(JSC::Heap& heap, Synchronousness synchronousness)

: GCActivityCallback(heap.vm(), synchronousness)

{

}

GCActivityCallback::GCActivityCallback(VM& vm, Synchronousness synchronousness)

: Base(vm)

, m_synchronousness(synchronousness)

{

}

GCActivityCallback::~GCActivityCallback() = default;

void GCActivityCallback::doWork(VM& vm)

{

if (!isEnabled())

return;

ASSERT(vm.currentThreadIsHoldingAPILock());

JSC::Heap& heap = vm.heap;

if (heap.isDeferred()) {

scheduleTimer(0_s);

return;

}

doCollection(vm);

}

void GCActivityCallback::scheduleTimer(Seconds newDelay)

{

if (newDelay * timerSlop > m_delay)

return;

Seconds delta = m_delay - newDelay;

m_delay = newDelay;

if (auto timeUntilFire = this->timeUntilFire())

newDelay = *timeUntilFire - delta;

setTimeUntilFire(newDelay);

}

double GCActivityCallback::deathRate(size_t sizeBefore, size_t sizeAfter)

{

if (!sizeBefore)

return 1.0;

if (sizeAfter > sizeBefore) {

// GC caused the heap to grow(!)

// This could happen if the we visited more extra memory than was reported allocated.

// We don't return a negative death rate, since that would schedule the next GC in the past.

return 0;

}

return static_cast<double>(sizeBefore - sizeAfter) / static_cast<double>(sizeBefore);

}

void GCActivityCallback::didAllocate(JSC::Heap& heap, size_t bytes)

{

// The first byte allocated in an allocation cycle will report 0 bytes to didAllocate.

// We pretend it's one byte so that we don't ignore this allocation entirely.

if (!bytes)

bytes = 1;

double bytesExpectedToReclaim = static_cast<double>(bytes) * deathRate(heap);

Seconds newDelay = lastGCLength(heap) / gcTimeSlice(bytesExpectedToReclaim);

scheduleTimer(newDelay);

}

void GCActivityCallback::willCollect()

{

cancel();

}

void GCActivityCallback::cancel()

{

m_delay = s_decade;

cancelTimer();

}

WebKit/Source/JavaScriptCore/heap/GCActivityCallback.cpp at main · WebKit/WebKit · GitHub

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