Imported WebKit commit 2ea9d364d0f6efa8fa64acf19f451504c59be0e4 (http://svn.webkit.org/repository/webkit/trunk@104285)

1 files changed, 480 insertions, 0 deletions

diff --git a/Source/JavaScriptCore/heap/MarkStack.cpp b/Source/JavaScriptCore/heap/MarkStack.cpp
new file mode 100644
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+++ b/Source/JavaScriptCore/heap/MarkStack.cpp
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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 "ConservativeRoots.h"
+#include "Heap.h"
+#include "Options.h"
+#include "JSArray.h"
+#include "JSCell.h"
+#include "JSObject.h"
+#include "ScopeChain.h"
+#include "Structure.h"
+#include "WriteBarrier.h"
+#include <wtf/MainThread.h>
+
+namespace JSC {
+
+MarkStackSegmentAllocator::MarkStackSegmentAllocator()
+    : m_nextFreeSegment(0)
+{
+}
+
+MarkStackSegmentAllocator::~MarkStackSegmentAllocator()
+{
+    shrinkReserve();
+}
+
+MarkStackSegment* MarkStackSegmentAllocator::allocate()
+{
+    {
+        MutexLocker locker(m_lock);
+        if (m_nextFreeSegment) {
+            MarkStackSegment* result = m_nextFreeSegment;
+            m_nextFreeSegment = result->m_previous;
+            return result;
+        }
+    }
+
+    return static_cast<MarkStackSegment*>(OSAllocator::reserveAndCommit(Options::gcMarkStackSegmentSize));
+}
+
+void MarkStackSegmentAllocator::release(MarkStackSegment* segment)
+{
+    MutexLocker locker(m_lock);
+    segment->m_previous = m_nextFreeSegment;
+    m_nextFreeSegment = segment;
+}
+
+void MarkStackSegmentAllocator::shrinkReserve()
+{
+    MarkStackSegment* segments;
+    {
+        MutexLocker locker(m_lock);
+        segments = m_nextFreeSegment;
+        m_nextFreeSegment = 0;
+    }
+    while (segments) {
+        MarkStackSegment* toFree = segments;
+        segments = segments->m_previous;
+        OSAllocator::decommitAndRelease(toFree, Options::gcMarkStackSegmentSize);
+    }
+}
+
+MarkStackArray::MarkStackArray(MarkStackSegmentAllocator& allocator)
+    : m_allocator(allocator)
+    , m_segmentCapacity(MarkStackSegment::capacityFromSize(Options::gcMarkStackSegmentSize))
+    , m_top(0)
+    , m_numberOfPreviousSegments(0)
+{
+    m_topSegment = m_allocator.allocate();
+#if !ASSERT_DISABLED
+    m_topSegment->m_top = 0;
+#endif
+    m_topSegment->m_previous = 0;
+}
+
+MarkStackArray::~MarkStackArray()
+{
+    ASSERT(!m_topSegment->m_previous);
+    m_allocator.release(m_topSegment);
+}
+
+void MarkStackArray::expand()
+{
+    ASSERT(m_topSegment->m_top == m_segmentCapacity);
+    
+    m_numberOfPreviousSegments++;
+    
+    MarkStackSegment* nextSegment = m_allocator.allocate();
+#if !ASSERT_DISABLED
+    nextSegment->m_top = 0;
+#endif
+    nextSegment->m_previous = m_topSegment;
+    m_topSegment = nextSegment;
+    setTopForEmptySegment();
+    validatePrevious();
+}
+
+bool MarkStackArray::refill()
+{
+    validatePrevious();
+    if (top())
+        return true;
+    MarkStackSegment* toFree = m_topSegment;
+    MarkStackSegment* previous = m_topSegment->m_previous;
+    if (!previous)
+        return false;
+    ASSERT(m_numberOfPreviousSegments);
+    m_numberOfPreviousSegments--;
+    m_topSegment = previous;
+    m_allocator.release(toFree);
+    setTopForFullSegment();
+    validatePrevious();
+    return true;
+}
+
+bool MarkStackArray::donateSomeCellsTo(MarkStackArray& other)
+{
+    ASSERT(m_segmentCapacity == other.m_segmentCapacity);
+    validatePrevious();
+    other.validatePrevious();
+        
+    // Fast check: see if the other mark stack already has enough segments.
+    if (other.m_numberOfPreviousSegments + 1 >= Options::maximumNumberOfSharedSegments)
+        return false;
+        
+    size_t numberOfCellsToKeep = Options::minimumNumberOfCellsToKeep;
+    ASSERT(m_top > numberOfCellsToKeep || m_topSegment->m_previous);
+        
+    // Looks like we should donate! Give the other mark stack all of our
+    // previous segments, and then top it off.
+    MarkStackSegment* previous = m_topSegment->m_previous;
+    while (previous) {
+        ASSERT(m_numberOfPreviousSegments);
+
+        MarkStackSegment* current = previous;
+        previous = current->m_previous;
+            
+        current->m_previous = other.m_topSegment->m_previous;
+        other.m_topSegment->m_previous = current;
+            
+        m_numberOfPreviousSegments--;
+        other.m_numberOfPreviousSegments++;
+    }
+    ASSERT(!m_numberOfPreviousSegments);
+    m_topSegment->m_previous = 0;
+    validatePrevious();
+    other.validatePrevious();
+        
+    // Now top off. We want to keep at a minimum numberOfCellsToKeep, but if
+    // we really have a lot of work, we give up half.
+    if (m_top > numberOfCellsToKeep * 2)
+        numberOfCellsToKeep = m_top / 2;
+    while (m_top > numberOfCellsToKeep)
+        other.append(removeLast());
+        
+    return true;
+}
+
+void MarkStackArray::stealSomeCellsFrom(MarkStackArray& other)
+{
+    ASSERT(m_segmentCapacity == other.m_segmentCapacity);
+    validatePrevious();
+    other.validatePrevious();
+        
+    // If other has an entire segment, steal it and return.
+    if (other.m_topSegment->m_previous) {
+        ASSERT(other.m_topSegment->m_previous->m_top == m_segmentCapacity);
+            
+        // First remove a segment from other.
+        MarkStackSegment* current = other.m_topSegment->m_previous;
+        other.m_topSegment->m_previous = current->m_previous;
+        other.m_numberOfPreviousSegments--;
+            
+        ASSERT(!!other.m_numberOfPreviousSegments == !!other.m_topSegment->m_previous);
+            
+        // Now add it to this.
+        current->m_previous = m_topSegment->m_previous;
+        m_topSegment->m_previous = current;
+        m_numberOfPreviousSegments++;
+            
+        validatePrevious();
+        other.validatePrevious();
+        return;
+    }
+        
+    // Otherwise drain 1/Nth of the shared array where N is the number of
+    // workers, or Options::minimumNumberOfCellsToKeep, whichever is bigger.
+    size_t numberOfCellsToSteal = std::max((size_t)Options::minimumNumberOfCellsToKeep, other.size() / Options::numberOfGCMarkers);
+    while (numberOfCellsToSteal-- > 0 && other.canRemoveLast())
+        append(other.removeLast());
+}
+
+#if ENABLE(PARALLEL_GC)
+void MarkStackThreadSharedData::markingThreadMain()
+{
+    WTF::registerGCThread();
+    SlotVisitor slotVisitor(*this);
+    ParallelModeEnabler enabler(slotVisitor);
+    slotVisitor.drainFromShared(SlotVisitor::SlaveDrain);
+}
+
+void* MarkStackThreadSharedData::markingThreadStartFunc(void* shared)
+{
+    static_cast<MarkStackThreadSharedData*>(shared)->markingThreadMain();
+    return 0;
+}
+#endif
+
+MarkStackThreadSharedData::MarkStackThreadSharedData(JSGlobalData* globalData)
+    : m_globalData(globalData)
+    , m_sharedMarkStack(m_segmentAllocator)
+    , m_numberOfActiveParallelMarkers(0)
+    , m_parallelMarkersShouldExit(false)
+{
+#if ENABLE(PARALLEL_GC)
+    for (unsigned i = 1; i < Options::numberOfGCMarkers; ++i) {
+        m_markingThreads.append(createThread(markingThreadStartFunc, this, "JavaScriptCore::Marking"));
+        ASSERT(m_markingThreads.last());
+    }
+#endif
+}
+
+MarkStackThreadSharedData::~MarkStackThreadSharedData()
+{
+#if ENABLE(PARALLEL_GC)    
+    // Destroy our marking threads.
+    {
+        MutexLocker locker(m_markingLock);
+        m_parallelMarkersShouldExit = true;
+        m_markingCondition.broadcast();
+    }
+    for (unsigned i = 0; i < m_markingThreads.size(); ++i)
+        waitForThreadCompletion(m_markingThreads[i], 0);
+#endif
+}
+    
+void MarkStackThreadSharedData::reset()
+{
+    ASSERT(!m_numberOfActiveParallelMarkers);
+    ASSERT(!m_parallelMarkersShouldExit);
+    ASSERT(m_sharedMarkStack.isEmpty());
+    
+#if ENABLE(PARALLEL_GC)
+    m_segmentAllocator.shrinkReserve();
+    m_opaqueRoots.clear();
+#else
+    ASSERT(m_opaqueRoots.isEmpty());
+#endif
+    
+    m_weakReferenceHarvesters.removeAll();
+}
+
+void MarkStack::reset()
+{
+    m_visitCount = 0;
+    ASSERT(m_stack.isEmpty());
+#if ENABLE(PARALLEL_GC)
+    ASSERT(m_opaqueRoots.isEmpty()); // Should have merged by now.
+#else
+    m_opaqueRoots.clear();
+#endif
+}
+
+void MarkStack::append(ConservativeRoots& conservativeRoots)
+{
+    JSCell** roots = conservativeRoots.roots();
+    size_t size = conservativeRoots.size();
+    for (size_t i = 0; i < size; ++i)
+        internalAppend(roots[i]);
+}
+
+ALWAYS_INLINE static void visitChildren(SlotVisitor& visitor, const JSCell* cell)
+{
+#if ENABLE(SIMPLE_HEAP_PROFILING)
+    m_visitedTypeCounts.count(cell);
+#endif
+
+    ASSERT(Heap::isMarked(cell));
+
+    if (isJSString(cell)) {
+        JSString::visitChildren(const_cast<JSCell*>(cell), visitor);
+        return;
+    }
+
+    if (isJSFinalObject(cell)) {
+        JSObject::visitChildren(const_cast<JSCell*>(cell), visitor);
+        return;
+    }
+
+    if (isJSArray(cell)) {
+        JSArray::visitChildren(const_cast<JSCell*>(cell), visitor);
+        return;
+    }
+
+    cell->methodTable()->visitChildren(const_cast<JSCell*>(cell), visitor);
+}
+
+void SlotVisitor::donateSlow()
+{
+    // Refuse to donate if shared has more entries than I do.
+    if (m_shared.m_sharedMarkStack.size() > m_stack.size())
+        return;
+    MutexLocker locker(m_shared.m_markingLock);
+    if (m_stack.donateSomeCellsTo(m_shared.m_sharedMarkStack)) {
+        // Only wake up threads if the shared stack is big enough; otherwise assume that
+        // it's more profitable for us to just scan this ourselves later.
+        if (m_shared.m_sharedMarkStack.size() >= Options::sharedStackWakeupThreshold)
+            m_shared.m_markingCondition.broadcast();
+    }
+}
+
+void SlotVisitor::drain()
+{
+    ASSERT(m_isInParallelMode);
+    
+#if ENABLE(PARALLEL_GC)
+    if (Options::numberOfGCMarkers > 1) {
+        while (!m_stack.isEmpty()) {
+            m_stack.refill();
+            for (unsigned countdown = Options::minimumNumberOfScansBetweenRebalance; m_stack.canRemoveLast() && countdown--;)
+                visitChildren(*this, m_stack.removeLast());
+            donateKnownParallel();
+        }
+        
+        mergeOpaqueRootsIfNecessary();
+        return;
+    }
+#endif
+    
+    while (!m_stack.isEmpty()) {
+        m_stack.refill();
+        while (m_stack.canRemoveLast())
+            visitChildren(*this, m_stack.removeLast());
+    }
+}
+
+void SlotVisitor::drainFromShared(SharedDrainMode sharedDrainMode)
+{
+    ASSERT(m_isInParallelMode);
+    
+    ASSERT(Options::numberOfGCMarkers);
+    
+    bool shouldBeParallel;
+
+#if ENABLE(PARALLEL_GC)
+    shouldBeParallel = Options::numberOfGCMarkers > 1;
+#else
+    ASSERT(Options::numberOfGCMarkers == 1);
+    shouldBeParallel = false;
+#endif
+    
+    if (!shouldBeParallel) {
+        // This call should be a no-op.
+        ASSERT_UNUSED(sharedDrainMode, sharedDrainMode == MasterDrain);
+        ASSERT(m_stack.isEmpty());
+        ASSERT(m_shared.m_sharedMarkStack.isEmpty());
+        return;
+    }
+    
+#if ENABLE(PARALLEL_GC)
+    {
+        MutexLocker locker(m_shared.m_markingLock);
+        m_shared.m_numberOfActiveParallelMarkers++;
+    }
+    while (true) {
+        {
+            MutexLocker locker(m_shared.m_markingLock);
+            m_shared.m_numberOfActiveParallelMarkers--;
+
+            // How we wait differs depending on drain mode.
+            if (sharedDrainMode == MasterDrain) {
+                // Wait until either termination is reached, or until there is some work
+                // for us to do.
+                while (true) {
+                    // Did we reach termination?
+                    if (!m_shared.m_numberOfActiveParallelMarkers && m_shared.m_sharedMarkStack.isEmpty())
+                        return;
+                    
+                    // Is there work to be done?
+                    if (!m_shared.m_sharedMarkStack.isEmpty())
+                        break;
+                    
+                    // Otherwise wait.
+                    m_shared.m_markingCondition.wait(m_shared.m_markingLock);
+                }
+            } else {
+                ASSERT(sharedDrainMode == SlaveDrain);
+                
+                // Did we detect termination? If so, let the master know.
+                if (!m_shared.m_numberOfActiveParallelMarkers && m_shared.m_sharedMarkStack.isEmpty())
+                    m_shared.m_markingCondition.broadcast();
+                
+                while (m_shared.m_sharedMarkStack.isEmpty() && !m_shared.m_parallelMarkersShouldExit)
+                    m_shared.m_markingCondition.wait(m_shared.m_markingLock);
+                
+                // Is the VM exiting? If so, exit this thread.
+                if (m_shared.m_parallelMarkersShouldExit)
+                    return;
+            }
+            
+            m_stack.stealSomeCellsFrom(m_shared.m_sharedMarkStack);
+            m_shared.m_numberOfActiveParallelMarkers++;
+        }
+        
+        drain();
+    }
+#endif
+}
+
+void MarkStack::mergeOpaqueRoots()
+{
+    ASSERT(!m_opaqueRoots.isEmpty()); // Should only be called when opaque roots are non-empty.
+    {
+        MutexLocker locker(m_shared.m_opaqueRootsLock);
+        HashSet<void*>::iterator begin = m_opaqueRoots.begin();
+        HashSet<void*>::iterator end = m_opaqueRoots.end();
+        for (HashSet<void*>::iterator iter = begin; iter != end; ++iter)
+            m_shared.m_opaqueRoots.add(*iter);
+    }
+    m_opaqueRoots.clear();
+}
+
+void SlotVisitor::harvestWeakReferences()
+{
+    for (WeakReferenceHarvester* current = m_shared.m_weakReferenceHarvesters.head(); current; current = current->next())
+        current->visitWeakReferences(*this);
+}
+
+void SlotVisitor::finalizeUnconditionalFinalizers()
+{
+    while (m_shared.m_unconditionalFinalizers.hasNext())
+        m_shared.m_unconditionalFinalizers.removeNext()->finalizeUnconditionally();
+}
+
+#if ENABLE(GC_VALIDATION)
+void MarkStack::validate(JSCell* cell)
+{
+    if (!cell)
+        CRASH();
+
+    if (!cell->structure())
+        CRASH();
+
+    // Both the cell's structure, and the cell's structure's structure should be the Structure Structure.
+    // I hate this sentence.
+    if (cell->structure()->structure()->JSCell::classInfo() != cell->structure()->JSCell::classInfo())
+        CRASH();
+}
+#else
+void MarkStack::validate(JSCell*)
+{
+}
+#endif
+
+} // namespace JSC