Source/JavaScriptCore/heap/MarkedAllocator.cpp

/*
 * Copyright (C) 2012, 2013, 2016 Apple Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#include "config.h"
#include "MarkedAllocator.h"

#include "GCActivityCallback.h"
#include "Heap.h"
#include "IncrementalSweeper.h"
#include "JSCInlines.h"
#include "VM.h"
#include <wtf/CurrentTime.h>

namespace JSC {

static bool isListPagedOut(double deadline, DoublyLinkedList<MarkedBlock>& list)
{
    unsigned itersSinceLastTimeCheck = 0;
    MarkedBlock* block = list.head();
    while (block) {
        block = block->next();
        ++itersSinceLastTimeCheck;
        if (itersSinceLastTimeCheck >= Heap::s_timeCheckResolution) {
            double currentTime = WTF::monotonicallyIncreasingTime();
            if (currentTime > deadline)
                return true;
            itersSinceLastTimeCheck = 0;
        }
    }
    return false;
}

bool MarkedAllocator::isPagedOut(double deadline)
{
    if (isListPagedOut(deadline, m_blockList))
        return true;
    return false;
}

void MarkedAllocator::retire(MarkedBlock* block, MarkedBlock::FreeList& freeList)
{
    m_blockList.remove(block);
    m_retiredBlocks.push(block);
    block->didRetireBlock(freeList);
}

inline void* MarkedAllocator::tryAllocateHelper(size_t bytes)
{
    if (m_currentBlock) {
        ASSERT(m_currentBlock == m_nextBlockToSweep);
        m_currentBlock->didConsumeFreeList();
        m_nextBlockToSweep = m_currentBlock->next();
    }

    MarkedBlock* next;
    for (MarkedBlock*& block = m_nextBlockToSweep; block; block = next) {
        next = block->next();

        MarkedBlock::FreeList freeList = block->sweep(MarkedBlock::SweepToFreeList);
        
        double utilization = ((double)MarkedBlock::blockSize - (double)freeList.bytes) / (double)MarkedBlock::blockSize;
        if (utilization >= Options::minMarkedBlockUtilization()) {
            ASSERT(freeList.bytes || !freeList.head);
            retire(block, freeList);
            continue;
        }

        if (bytes > block->cellSize()) {
            block->stopAllocating(freeList);
            continue;
        }

        m_currentBlock = block;
        m_freeList = freeList;
        break;
    }
    
    if (!m_freeList.head) {
        m_currentBlock = 0;
        return 0;
    }

    ASSERT(m_freeList.head);
    void* head = tryPopFreeList(bytes);
    ASSERT(head);
    m_markedSpace->didAllocateInBlock(m_currentBlock);
    return head;
}

inline void* MarkedAllocator::tryPopFreeList(size_t bytes)
{
    ASSERT(m_currentBlock);
    if (bytes > m_currentBlock->cellSize())
        return 0;

    MarkedBlock::FreeCell* head = m_freeList.head;
    m_freeList.head = head->next;
    return head;
}

inline void* MarkedAllocator::tryAllocate(size_t bytes)
{
    ASSERT(!m_heap->isBusy());
    m_heap->m_operationInProgress = Allocation;
    void* result = tryAllocateHelper(bytes);

    m_heap->m_operationInProgress = NoOperation;
    ASSERT(result || !m_currentBlock);
    return result;
}

ALWAYS_INLINE void MarkedAllocator::doTestCollectionsIfNeeded()
{
    if (!Options::slowPathAllocsBetweenGCs())
        return;

    static unsigned allocationCount = 0;
    if (!allocationCount) {
        if (!m_heap->isDeferred())
            m_heap->collectAllGarbage();
        ASSERT(m_heap->m_operationInProgress == NoOperation);
    }
    if (++allocationCount >= Options::slowPathAllocsBetweenGCs())
        allocationCount = 0;
}

void* MarkedAllocator::allocateSlowCase(size_t bytes)
{
    ASSERT(m_heap->vm()->currentThreadIsHoldingAPILock());
    doTestCollectionsIfNeeded();

    ASSERT(!m_markedSpace->isIterating());
    ASSERT(!m_freeList.head);
    m_heap->didAllocate(m_freeList.bytes);
    
    void* result = tryAllocate(bytes);
    
    if (LIKELY(result != 0))
        return result;
    
    if (m_heap->collectIfNecessaryOrDefer()) {
        result = tryAllocate(bytes);
        if (result)
            return result;
    }

    ASSERT(!m_heap->shouldCollect());
    
    MarkedBlock* block = allocateBlock(bytes);
    ASSERT(block);
    addBlock(block);
        
    result = tryAllocate(bytes);
    ASSERT(result);
    return result;
}

MarkedBlock* MarkedAllocator::allocateBlock(size_t bytes)
{
    size_t minBlockSize = MarkedBlock::blockSize;
    size_t minAllocationSize = WTF::roundUpToMultipleOf<MarkedBlock::atomSize>(sizeof(MarkedBlock)) + WTF::roundUpToMultipleOf<MarkedBlock::atomSize>(bytes);
    minAllocationSize = WTF::roundUpToMultipleOf(WTF::pageSize(), minAllocationSize);
    size_t blockSize = std::max(minBlockSize, minAllocationSize);

    size_t cellSize = m_cellSize ? m_cellSize : WTF::roundUpToMultipleOf<MarkedBlock::atomSize>(bytes);

    // FIXME: Support allocating storage in marked blocks. This would mean that allocateBlock()
    // takes a HeapCell::Kind, or something like that.
    // https://bugs.webkit.org/show_bug.cgi?id=159658
    return MarkedBlock::create(*m_heap, this, blockSize, cellSize, m_needsDestruction, HeapCell::JSCell);
}

void MarkedAllocator::addBlock(MarkedBlock* block)
{
    ASSERT(!m_currentBlock);
    ASSERT(!m_freeList.head);
    
    m_blockList.append(block);
    m_nextBlockToSweep = block;
    m_markedSpace->didAddBlock(block);
}

void MarkedAllocator::removeBlock(MarkedBlock* block)
{
    if (m_currentBlock == block) {
        m_currentBlock = m_currentBlock->next();
        m_freeList = MarkedBlock::FreeList();
    }
    if (m_nextBlockToSweep == block)
        m_nextBlockToSweep = m_nextBlockToSweep->next();

    block->willRemoveBlock();
    m_blockList.remove(block);
}

void MarkedAllocator::reset()
{
    m_lastActiveBlock = 0;
    m_currentBlock = 0;
    m_freeList = MarkedBlock::FreeList();
    if (m_heap->operationInProgress() == FullCollection)
        m_blockList.append(m_retiredBlocks);

    m_nextBlockToSweep = m_blockList.head();

    if (UNLIKELY(Options::useImmortalObjects())) {
        MarkedBlock* next;
        for (MarkedBlock*& block = m_nextBlockToSweep; block; block = next) {
            next = block->next();

            MarkedBlock::FreeList freeList = block->sweep(MarkedBlock::SweepToFreeList);
            retire(block, freeList);
        }
    }
}

void MarkedAllocator::lastChanceToFinalize()
{
    m_blockList.append(m_retiredBlocks);
    forEachBlock(
        [&] (MarkedBlock* block) {
            block->lastChanceToFinalize();
        });
}

} // namespace JSC