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/*
* Copyright (C) 2009 Google 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:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
* * Neither the name of Google Inc. 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 THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
* OWNER 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 "V8GCController.h"
#include "Attr.h"
#include "HTMLImageElement.h"
#include "MemoryUsageSupport.h"
#include "TraceEvent.h"
#include "V8AbstractEventListener.h"
#include "V8Binding.h"
#include "V8MessagePort.h"
#include "V8MutationObserver.h"
#include "V8Node.h"
#include "V8RecursionScope.h"
#include "WrapperTypeInfo.h"
#include <algorithm>
namespace WebCore {
class ImplicitConnection {
public:
ImplicitConnection(void* root, v8::Persistent<v8::Value> wrapper)
: m_root(root)
, m_wrapper(wrapper)
{
}
void* root() const { return m_root; }
v8::Persistent<v8::Value> wrapper() const { return m_wrapper; }
private:
void* m_root;
v8::Persistent<v8::Value> m_wrapper;
};
bool operator<(const ImplicitConnection& left, const ImplicitConnection& right)
{
return left.root() < right.root();
}
class WrapperGrouper {
public:
WrapperGrouper()
{
m_liveObjects.append(V8PerIsolateData::current()->ensureLiveRoot());
}
void addToGroup(void* root, v8::Persistent<v8::Value> wrapper)
{
m_connections.append(ImplicitConnection(root, wrapper));
}
void keepAlive(v8::Persistent<v8::Value> wrapper)
{
m_liveObjects.append(wrapper);
}
void apply()
{
if (m_liveObjects.size() > 1)
v8::V8::AddObjectGroup(m_liveObjects.data(), m_liveObjects.size());
std::sort(m_connections.begin(), m_connections.end());
Vector<v8::Persistent<v8::Value> > group;
size_t i = 0;
while (i < m_connections.size()) {
void* root = m_connections[i].root();
do {
group.append(m_connections[i++].wrapper());
} while (i < m_connections.size() && root == m_connections[i].root());
if (group.size() > 1)
v8::V8::AddObjectGroup(group.data(), group.size(), 0);
group.shrink(0);
}
}
private:
Vector<v8::Persistent<v8::Value> > m_liveObjects;
Vector<ImplicitConnection> m_connections;
};
// FIXME: This should use opaque GC roots.
static void addImplicitReferencesForNodeWithEventListeners(Node* node, v8::Persistent<v8::Object> wrapper)
{
ASSERT(node->hasEventListeners());
Vector<v8::Persistent<v8::Value> > listeners;
EventListenerIterator iterator(node);
while (EventListener* listener = iterator.nextListener()) {
if (listener->type() != EventListener::JSEventListenerType)
continue;
V8AbstractEventListener* v8listener = static_cast<V8AbstractEventListener*>(listener);
if (!v8listener->hasExistingListenerObject())
continue;
listeners.append(v8listener->existingListenerObjectPersistentHandle());
}
if (listeners.isEmpty())
return;
v8::V8::AddImplicitReferences(wrapper, listeners.data(), listeners.size());
}
void* V8GCController::opaqueRootForGC(Node* node)
{
if (node->inDocument() || (node->hasTagName(HTMLNames::imgTag) && static_cast<HTMLImageElement*>(node)->hasPendingActivity()))
return node->document();
if (node->isAttributeNode()) {
Node* ownerElement = static_cast<Attr*>(node)->ownerElement();
if (!ownerElement)
return node;
node = ownerElement;
}
while (Node* parent = node->parentOrHostNode())
node = parent;
return node;
}
class WrapperVisitor : public v8::PersistentHandleVisitor {
public:
virtual void VisitPersistentHandle(v8::Persistent<v8::Value> value, uint16_t classId) OVERRIDE
{
ASSERT(value->IsObject());
v8::Persistent<v8::Object> wrapper = v8::Persistent<v8::Object>::Cast(value);
if (classId != v8DOMNodeClassId && classId != v8DOMObjectClassId)
return;
ASSERT(V8DOMWrapper::maybeDOMWrapper(value));
if (value.IsIndependent())
return;
WrapperTypeInfo* type = V8DOMWrapper::domWrapperType(wrapper);
void* object = toNative(wrapper);
if (V8MessagePort::info.equals(type)) {
// Mark each port as in-use if it's entangled. For simplicity's sake,
// we assume all ports are remotely entangled, since the Chromium port
// implementation can't tell the difference.
MessagePort* port = static_cast<MessagePort*>(object);
if (port->isEntangled() || port->hasPendingActivity())
m_grouper.keepAlive(wrapper);
#if ENABLE(MUTATION_OBSERVERS)
} else if (V8MutationObserver::info.equals(type)) {
// FIXME: Allow opaqueRootForGC to operate on multiple roots and move this logic into V8MutationObserverCustom.
MutationObserver* observer = static_cast<MutationObserver*>(object);
HashSet<Node*> observedNodes = observer->getObservedNodes();
for (HashSet<Node*>::iterator it = observedNodes.begin(); it != observedNodes.end(); ++it)
m_grouper.addToGroup(V8GCController::opaqueRootForGC(*it), wrapper);
#endif // ENABLE(MUTATION_OBSERVERS)
} else {
ActiveDOMObject* activeDOMObject = type->toActiveDOMObject(wrapper);
if (activeDOMObject && activeDOMObject->hasPendingActivity())
m_grouper.keepAlive(wrapper);
}
if (classId == v8DOMNodeClassId) {
ASSERT(V8Node::HasInstance(wrapper));
ASSERT(!wrapper.IsIndependent());
Node* node = static_cast<Node*>(object);
if (node->hasEventListeners())
addImplicitReferencesForNodeWithEventListeners(node, wrapper);
m_grouper.addToGroup(V8GCController::opaqueRootForGC(node), wrapper);
} else if (classId == v8DOMObjectClassId) {
m_grouper.addToGroup(type->opaqueRootForGC(object, wrapper), wrapper);
} else {
ASSERT_NOT_REACHED();
}
}
void notifyFinished()
{
m_grouper.apply();
}
private:
WrapperGrouper m_grouper;
};
// Regarding a minor GC algorithm for DOM nodes, see this document:
// https://docs.google.com/a/google.com/presentation/d/1uifwVYGNYTZDoGLyCb7sXa7g49mWNMW2gaWvMN5NLk8/edit#slide=id.p
//
// m_edenNodes stores nodes that have wrappers that have been created since the last minor/major GC.
Vector<Node*>* V8GCController::m_edenNodes = 0;
static void gcTree(Node* startNode)
{
Vector<v8::Persistent<v8::Value>, initialNodeVectorSize> newSpaceWrappers;
// We traverse a DOM tree in the DFS order starting from startNode.
// The traversal order does not matter for correctness but does matter for performance.
Node* node = startNode;
// To make each minor GC time bounded, we might need to give up
// traversing at some point for a large DOM tree. That being said,
// I could not observe the need even in pathological test cases.
do {
ASSERT(node);
if (!node->wrapper().IsEmpty()) {
if (!node->isV8CollectableDuringMinorGC()) {
// The fact that we encounter a node that is not in the Eden space
// implies that its wrapper might be in the old space of V8.
// This indicates that the minor GC cannot anyway judge reachability
// of this DOM tree. Thus we give up traversing the DOM tree.
return;
}
// A once traversed node is removed from the Eden space.
node->setV8CollectableDuringMinorGC(false);
newSpaceWrappers.append(node->wrapper());
}
if (node->firstChild()) {
node = node->firstChild();
continue;
}
while (!node->nextSibling()) {
if (!node->parentNode())
break;
node = node->parentNode();
}
if (node->parentNode())
node = node->nextSibling();
} while (node != startNode);
// We completed the DOM tree traversal. All wrappers in the DOM tree are
// stored in newSpaceWrappers and are expected to exist in the new space of V8.
// We report those wrappers to V8 as an object group.
for (size_t i = 0; i < newSpaceWrappers.size(); i++)
newSpaceWrappers[i].MarkPartiallyDependent();
if (newSpaceWrappers.size() > 0)
v8::V8::AddObjectGroup(&newSpaceWrappers[0], newSpaceWrappers.size());
}
void V8GCController::didCreateWrapperForNode(Node* node)
{
// To make minor GC cycle time bounded, we limit the number of wrappers handled
// by each minor GC cycle to 10000. This value was selected so that the minor
// GC cycle time is bounded to 20 ms in a case where the new space size
// is 16 MB and it is full of wrappers (which is almost the worst case).
// Practically speaking, as far as I crawled real web applications,
// the number of wrappers handled by each minor GC cycle is at most 3000.
// So this limit is mainly for pathological micro benchmarks.
const unsigned wrappersHandledByEachMinorGC = 10000;
ASSERT(!node->wrapper().IsEmpty());
if (!m_edenNodes)
m_edenNodes = adoptPtr(new Vector<Node*>).leakPtr();
if (m_edenNodes->size() <= wrappersHandledByEachMinorGC) {
// A node of a newly created wrapper is put into the Eden space.
m_edenNodes->append(node);
node->setV8CollectableDuringMinorGC(true);
}
}
void V8GCController::gcPrologue(v8::GCType type, v8::GCCallbackFlags flags)
{
if (type == v8::kGCTypeScavenge)
minorGCPrologue();
else if (type == v8::kGCTypeMarkSweepCompact)
majorGCPrologue();
if (isMainThreadOrGCThread() && m_edenNodes) {
// The Eden space is cleared at every minor/major GC.
m_edenNodes->clear();
}
}
void V8GCController::minorGCPrologue()
{
if (isMainThreadOrGCThread() && m_edenNodes) {
for (size_t i = 0; i < m_edenNodes->size(); i++) {
ASSERT(!m_edenNodes->at(i)->wrapper().IsEmpty());
if (m_edenNodes->at(i)->isV8CollectableDuringMinorGC()) // This branch is just for performance.
gcTree(m_edenNodes->at(i));
}
}
}
// Create object groups for DOM tree nodes.
void V8GCController::majorGCPrologue()
{
TRACE_EVENT_BEGIN0("v8", "GC");
v8::HandleScope scope;
WrapperVisitor visitor;
v8::V8::VisitHandlesWithClassIds(&visitor);
visitor.notifyFinished();
V8PerIsolateData* data = V8PerIsolateData::current();
data->stringCache()->clearOnGC();
}
static int workingSetEstimateMB = 0;
static Mutex& workingSetEstimateMBMutex()
{
AtomicallyInitializedStatic(Mutex&, mutex = *new Mutex);
return mutex;
}
void V8GCController::gcEpilogue(v8::GCType type, v8::GCCallbackFlags flags)
{
if (type == v8::kGCTypeScavenge)
minorGCEpilogue();
else if (type == v8::kGCTypeMarkSweepCompact)
majorGCEpilogue();
}
void V8GCController::minorGCEpilogue()
{
}
void V8GCController::majorGCEpilogue()
{
v8::HandleScope scope;
// The GC can happen on multiple threads in case of dedicated workers which run in-process.
{
MutexLocker locker(workingSetEstimateMBMutex());
workingSetEstimateMB = MemoryUsageSupport::actualMemoryUsageMB();
}
TRACE_EVENT_END0("v8", "GC");
}
void V8GCController::checkMemoryUsage()
{
const int lowMemoryUsageMB = MemoryUsageSupport::lowMemoryUsageMB();
const int highMemoryUsageMB = MemoryUsageSupport::highMemoryUsageMB();
const int highUsageDeltaMB = MemoryUsageSupport::highUsageDeltaMB();
int memoryUsageMB = MemoryUsageSupport::memoryUsageMB();
int workingSetEstimateMBCopy;
{
MutexLocker locker(workingSetEstimateMBMutex());
workingSetEstimateMBCopy = workingSetEstimateMB;
}
if (memoryUsageMB > lowMemoryUsageMB && memoryUsageMB > 2 * workingSetEstimateMBCopy) {
// Memory usage is large and doubled since the last GC.
// Check if we need to send low memory notification.
v8::HeapStatistics heapStatistics;
v8::V8::GetHeapStatistics(&heapStatistics);
int heapSizeMB = heapStatistics.total_heap_size() >> 20;
// Do not send low memory notification if V8 heap size is more than 7/8
// of total memory usage. Let V8 to schedule GC itself in this case.
if (heapSizeMB < memoryUsageMB / 8 * 7)
v8::V8::LowMemoryNotification();
} else if (memoryUsageMB > highMemoryUsageMB && memoryUsageMB > workingSetEstimateMBCopy + highUsageDeltaMB) {
// We are approaching OOM and memory usage increased by highUsageDeltaMB since the last GC.
v8::V8::LowMemoryNotification();
}
}
void V8GCController::hintForCollectGarbage()
{
V8PerIsolateData* data = V8PerIsolateData::current();
if (!data->shouldCollectGarbageSoon())
return;
const int longIdlePauseInMS = 1000;
data->clearShouldCollectGarbageSoon();
v8::V8::ContextDisposedNotification();
v8::V8::IdleNotification(longIdlePauseInMS);
}
void V8GCController::collectGarbage()
{
v8::HandleScope handleScope;
ScopedPersistent<v8::Context> context;
context.adopt(v8::Context::New());
if (context.isEmpty())
return;
{
v8::Context::Scope scope(context.get());
v8::Local<v8::String> source = v8::String::New("if (gc) gc();");
v8::Local<v8::String> name = v8::String::New("gc");
v8::Handle<v8::Script> script = v8::Script::Compile(source, name);
if (!script.IsEmpty()) {
V8RecursionScope::MicrotaskSuppression scope;
script->Run();
}
}
context.clear();
}
} // namespace WebCore
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