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Copy pathMarkedBlock.cpp
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294 lines (246 loc) · 9.92 KB
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/*
* Copyright (C) 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. 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 INC. 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 "MarkedBlock.h"
#include "DelayedReleaseScope.h"
#include "IncrementalSweeper.h"
#include "JSCell.h"
#include "JSDestructibleObject.h"
#include "JSCInlines.h"
namespace JSC {
MarkedBlock* MarkedBlock::create(DeadBlock* block, MarkedAllocator* allocator, size_t cellSize, DestructorType destructorType)
{
ASSERT(reinterpret_cast<size_t>(block) == (reinterpret_cast<size_t>(block) & blockMask));
Region* region = block->region();
return new (NotNull, block) MarkedBlock(region, allocator, cellSize, destructorType);
}
MarkedBlock::MarkedBlock(Region* region, MarkedAllocator* allocator, size_t cellSize, DestructorType destructorType)
: HeapBlock<MarkedBlock>(region)
, m_atomsPerCell((cellSize + atomSize - 1) / atomSize)
, m_endAtom((allocator->cellSize() ? atomsPerBlock : region->blockSize() / atomSize) - m_atomsPerCell + 1)
, m_destructorType(destructorType)
, m_allocator(allocator)
, m_state(New) // All cells start out unmarked.
, m_weakSet(allocator->heap()->vm())
{
ASSERT(allocator);
HEAP_LOG_BLOCK_STATE_TRANSITION(this);
}
template<MarkedBlock::DestructorType dtorType>
inline void MarkedBlock::callDestructor(JSCell* cell)
{
// A previous eager sweep may already have run cell's destructor.
if (cell->isZapped())
return;
if (dtorType == MarkedBlock::Normal)
jsCast<JSDestructibleObject*>(cell)->classInfo()->methodTable.destroy(cell);
else
cell->structure(*vm())->classInfo()->methodTable.destroy(cell);
cell->zap();
}
template<MarkedBlock::BlockState blockState, MarkedBlock::SweepMode sweepMode, MarkedBlock::DestructorType dtorType>
MarkedBlock::FreeList MarkedBlock::specializedSweep()
{
ASSERT(blockState != Allocated && blockState != FreeListed);
ASSERT(!(dtorType == MarkedBlock::None && sweepMode == SweepOnly));
// This produces a free list that is ordered in reverse through the block.
// This is fine, since the allocation code makes no assumptions about the
// order of the free list.
FreeCell* head = 0;
size_t count = 0;
for (size_t i = firstAtom(); i < m_endAtom; i += m_atomsPerCell) {
if (blockState == Marked && (m_marks.get(i) || (m_newlyAllocated && m_newlyAllocated->get(i))))
continue;
JSCell* cell = reinterpret_cast_ptr<JSCell*>(&atoms()[i]);
if (dtorType != MarkedBlock::None && blockState != New)
callDestructor<dtorType>(cell);
if (sweepMode == SweepToFreeList) {
FreeCell* freeCell = reinterpret_cast<FreeCell*>(cell);
freeCell->next = head;
head = freeCell;
++count;
}
}
// We only want to discard the newlyAllocated bits if we're creating a FreeList,
// otherwise we would lose information on what's currently alive.
if (sweepMode == SweepToFreeList && m_newlyAllocated)
m_newlyAllocated.clear();
m_state = ((sweepMode == SweepToFreeList) ? FreeListed : Marked);
return FreeList(head, count * cellSize());
}
MarkedBlock::FreeList MarkedBlock::sweep(SweepMode sweepMode)
{
ASSERT(DelayedReleaseScope::isInEffectFor(heap()->m_objectSpace));
HEAP_LOG_BLOCK_STATE_TRANSITION(this);
m_weakSet.sweep();
if (sweepMode == SweepOnly && m_destructorType == MarkedBlock::None)
return FreeList();
if (m_destructorType == MarkedBlock::ImmortalStructure)
return sweepHelper<MarkedBlock::ImmortalStructure>(sweepMode);
if (m_destructorType == MarkedBlock::Normal)
return sweepHelper<MarkedBlock::Normal>(sweepMode);
return sweepHelper<MarkedBlock::None>(sweepMode);
}
template<MarkedBlock::DestructorType dtorType>
MarkedBlock::FreeList MarkedBlock::sweepHelper(SweepMode sweepMode)
{
switch (m_state) {
case New:
ASSERT(sweepMode == SweepToFreeList);
return specializedSweep<New, SweepToFreeList, dtorType>();
case FreeListed:
// Happens when a block transitions to fully allocated.
ASSERT(sweepMode == SweepToFreeList);
return FreeList();
case Retired:
case Allocated:
RELEASE_ASSERT_NOT_REACHED();
return FreeList();
case Marked:
return sweepMode == SweepToFreeList
? specializedSweep<Marked, SweepToFreeList, dtorType>()
: specializedSweep<Marked, SweepOnly, dtorType>();
}
RELEASE_ASSERT_NOT_REACHED();
return FreeList();
}
class SetNewlyAllocatedFunctor : public MarkedBlock::VoidFunctor {
public:
SetNewlyAllocatedFunctor(MarkedBlock* block)
: m_block(block)
{
}
void operator()(JSCell* cell)
{
ASSERT(MarkedBlock::blockFor(cell) == m_block);
m_block->setNewlyAllocated(cell);
}
private:
MarkedBlock* m_block;
};
void MarkedBlock::stopAllocating(const FreeList& freeList)
{
HEAP_LOG_BLOCK_STATE_TRANSITION(this);
FreeCell* head = freeList.head;
if (m_state == Marked) {
// If the block is in the Marked state then we know that:
// 1) It was not used for allocation during the previous allocation cycle.
// 2) It may have dead objects, and we only know them to be dead by the
// fact that their mark bits are unset.
// Hence if the block is Marked we need to leave it Marked.
ASSERT(!head);
return;
}
ASSERT(m_state == FreeListed);
// Roll back to a coherent state for Heap introspection. Cells newly
// allocated from our free list are not currently marked, so we need another
// way to tell what's live vs dead.
ASSERT(!m_newlyAllocated);
m_newlyAllocated = adoptPtr(new WTF::Bitmap<atomsPerBlock>());
SetNewlyAllocatedFunctor functor(this);
forEachCell(functor);
FreeCell* next;
for (FreeCell* current = head; current; current = next) {
next = current->next;
reinterpret_cast<JSCell*>(current)->zap();
clearNewlyAllocated(current);
}
m_state = Marked;
}
void MarkedBlock::clearMarks()
{
#if ENABLE(GGC)
if (heap()->operationInProgress() == JSC::EdenCollection)
this->clearMarksWithCollectionType<EdenCollection>();
else
this->clearMarksWithCollectionType<FullCollection>();
#else
this->clearMarksWithCollectionType<FullCollection>();
#endif
}
void MarkedBlock::clearRememberedSet()
{
m_rememberedSet.clearAll();
}
template <HeapOperation collectionType>
void MarkedBlock::clearMarksWithCollectionType()
{
ASSERT(collectionType == FullCollection || collectionType == EdenCollection);
HEAP_LOG_BLOCK_STATE_TRANSITION(this);
ASSERT(m_state != New && m_state != FreeListed);
if (collectionType == FullCollection) {
m_marks.clearAll();
#if ENABLE(GGC)
m_rememberedSet.clearAll();
#endif
// This will become true at the end of the mark phase. We set it now to
// avoid an extra pass to do so later.
m_state = Marked;
return;
}
ASSERT(collectionType == EdenCollection);
// If a block was retired then there's no way an EdenCollection can un-retire it.
if (m_state != Retired)
m_state = Marked;
}
void MarkedBlock::lastChanceToFinalize()
{
m_weakSet.lastChanceToFinalize();
clearNewlyAllocated();
clearMarksWithCollectionType<FullCollection>();
sweep();
}
MarkedBlock::FreeList MarkedBlock::resumeAllocating()
{
HEAP_LOG_BLOCK_STATE_TRANSITION(this);
ASSERT(m_state == Marked);
if (!m_newlyAllocated) {
// We didn't have to create a "newly allocated" bitmap. That means we were already Marked
// when we last stopped allocation, so return an empty free list and stay in the Marked state.
return FreeList();
}
// Re-create our free list from before stopping allocation.
return sweep(SweepToFreeList);
}
void MarkedBlock::didRetireBlock(const FreeList& freeList)
{
HEAP_LOG_BLOCK_STATE_TRANSITION(this);
FreeCell* head = freeList.head;
// Currently we don't notify the Heap that we're giving up on this block.
// The Heap might be able to make a better decision about how many bytes should
// be allocated before the next collection if it knew about this retired block.
// On the other hand we'll waste at most 10% of our Heap space between FullCollections
// and only under heavy fragmentation.
// We need to zap the free list when retiring a block so that we don't try to destroy
// previously destroyed objects when we re-sweep the block in the future.
FreeCell* next;
for (FreeCell* current = head; current; current = next) {
next = current->next;
reinterpret_cast<JSCell*>(current)->zap();
}
ASSERT(m_state == FreeListed);
m_state = Retired;
}
} // namespace JSC