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/*
* Copyright (C) 2009, 2011 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.
*/
#include "config.h"
#include "MarkStack.h"
#include "MarkStackInlines.h"
#include "ConservativeRoots.h"
#include "CopiedSpace.h"
#include "CopiedSpaceInlines.h"
#include "Heap.h"
#include "Options.h"
#include "JSArray.h"
#include "JSCell.h"
#include "JSObject.h"
#include "SlotVisitorInlines.h"
#include "Structure.h"
#include "WriteBarrier.h"
#include <wtf/Atomics.h>
#include <wtf/DataLog.h>
#include <wtf/MainThread.h>
namespace JSC {
MarkStackArray::MarkStackArray(BlockAllocator& blockAllocator)
: m_blockAllocator(blockAllocator)
, m_segmentCapacity(MarkStackSegment::capacityFromSize(Options::gcMarkStackSegmentSize()))
, m_top(0)
, m_numberOfSegments(0)
{
ASSERT(MarkStackSegment::blockSize == WeakBlock::blockSize);
m_segments.push(MarkStackSegment::create(m_blockAllocator.allocate<MarkStackSegment>()));
m_numberOfSegments++;
}
MarkStackArray::~MarkStackArray()
{
ASSERT(m_numberOfSegments == 1 && m_segments.size() == 1);
m_blockAllocator.deallocate(MarkStackSegment::destroy(m_segments.removeHead()));
}
void MarkStackArray::expand()
{
ASSERT(m_segments.head()->m_top == m_segmentCapacity);
MarkStackSegment* nextSegment = MarkStackSegment::create(m_blockAllocator.allocate<MarkStackSegment>());
m_numberOfSegments++;
#if !ASSERT_DISABLED
nextSegment->m_top = 0;
#endif
m_segments.push(nextSegment);
setTopForEmptySegment();
validatePrevious();
}
bool MarkStackArray::refill()
{
validatePrevious();
if (top())
return true;
m_blockAllocator.deallocate(MarkStackSegment::destroy(m_segments.removeHead()));
ASSERT(m_numberOfSegments > 1);
m_numberOfSegments--;
setTopForFullSegment();
validatePrevious();
return true;
}
void MarkStackArray::donateSomeCellsTo(MarkStackArray& other)
{
// Try to donate about 1 / 2 of our cells. To reduce copying costs,
// we prefer donating whole segments over donating individual cells,
// even if this skews away from our 1 / 2 target.
ASSERT(m_segmentCapacity == other.m_segmentCapacity);
size_t segmentsToDonate = m_numberOfSegments / 2; // If we only have one segment (our head) we don't donate any segments.
if (!segmentsToDonate) {
size_t cellsToDonate = m_top / 2; // Round down to donate 0 / 1 cells.
while (cellsToDonate--) {
ASSERT(m_top);
other.append(removeLast());
}
return;
}
validatePrevious();
other.validatePrevious();
// Remove our head and the head of the other list before we start moving segments around.
// We'll add them back on once we're done donating.
MarkStackSegment* myHead = m_segments.removeHead();
MarkStackSegment* otherHead = other.m_segments.removeHead();
while (segmentsToDonate--) {
MarkStackSegment* current = m_segments.removeHead();
ASSERT(current);
ASSERT(m_numberOfSegments > 1);
other.m_segments.push(current);
m_numberOfSegments--;
other.m_numberOfSegments++;
}
// Put the original heads back in their places.
m_segments.push(myHead);
other.m_segments.push(otherHead);
validatePrevious();
other.validatePrevious();
}
void MarkStackArray::stealSomeCellsFrom(MarkStackArray& other, size_t idleThreadCount)
{
// Try to steal 1 / Nth of the shared array, where N is the number of idle threads.
// To reduce copying costs, we prefer stealing a whole segment over stealing
// individual cells, even if this skews away from our 1 / N target.
ASSERT(m_segmentCapacity == other.m_segmentCapacity);
validatePrevious();
other.validatePrevious();
// If other has an entire segment, steal it and return.
if (other.m_numberOfSegments > 1) {
// Move the heads of the lists aside. We'll push them back on after.
MarkStackSegment* otherHead = other.m_segments.removeHead();
MarkStackSegment* myHead = m_segments.removeHead();
ASSERT(other.m_segments.head()->m_top == m_segmentCapacity);
m_segments.push(other.m_segments.removeHead());
m_numberOfSegments++;
other.m_numberOfSegments--;
m_segments.push(myHead);
other.m_segments.push(otherHead);
validatePrevious();
other.validatePrevious();
return;
}
size_t numberOfCellsToSteal = (other.size() + idleThreadCount - 1) / idleThreadCount; // Round up to steal 1 / 1.
while (numberOfCellsToSteal-- > 0 && other.canRemoveLast())
append(other.removeLast());
}
} // namespace JSC
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