WebKit/Source/JavaScriptCore/heap/Heap.cpp at main · WebKit/WebKit · GitHub

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* This library is free software; you can redistribute it and/or

* modify it under the terms of the GNU Lesser General Public

* License as published by the Free Software Foundation; either

* version 2 of the License, or (at your option) any later version.

* This library is distributed in the hope that it will be useful,

* but WITHOUT ANY WARRANTY; without even the implied warranty of

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

* Lesser General Public License for more details.

* You should have received a copy of the GNU Lesser General Public

* License along with this library; if not, write to the Free Software

* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

#include "config.h"

#include "Heap.h"

#include "JSCJSValueInlines.h"

#include "BaselineJITCode.h"

#include "BuiltinExecutables.h"

#include "CodeBlock.h"

#include "CodeBlockSetInlines.h"

#include "CollectingScope.h"

#include "ConservativeRoots.h"

#include "EdenGCActivityCallback.h"

#include "EvalExecutable.h"

#include "Exception.h"

#include "FastMallocAlignedMemoryAllocator.h"

#include "FullGCActivityCallback.h"

#include "FunctionExecutableInlines.h"

#include "GCActivityCallback.h"

#include "GCIncomingRefCountedInlines.h"

#include "GCIncomingRefCountedSetInlines.h"

#include "GCSegmentedArrayInlines.h"

#include "GCTypeMap.h"

#include "GigacageAlignedMemoryAllocator.h"

#include "HasOwnPropertyCache.h"

#include "HeapHelperPool.h"

#include "HeapIterationScope.h"

#include "HeapProfiler.h"

#include "HeapSnapshot.h"

#include "HeapSubspaceTypes.h"

#include "HeapVerifier.h"

#include "IncrementalSweeper.h"

#include "Interpreter.h"

#include "IsoCellSetInlines.h"

#include "IsoInlinedHeapCellTypeInlines.h"

#include "JITStubRoutineSet.h"

#include "JITWorklistInlines.h"

#include "JSFinalizationRegistry.h"

#include "JSFunctionWithFields.h"

#include "JSIterator.h"

#include "JSMicrotaskDispatcher.h"

#include "JSModuleLoader.h"

#include "JSPromiseCombinatorsContext.h"

#include "JSPromiseCombinatorsGlobalContext.h"

#include "JSPromiseReaction.h"

#include "JSRawJSONObject.h"

#include "JSRemoteFunction.h"

#include "JSSentinel.h"

#include "JSVirtualMachineInternal.h"

#include "JSWeakMap.h"

#include "JSWeakObjectRef.h"

#include "JSWeakSet.h"

#include "MachineStackMarker.h"

#include "MarkStackMergingConstraint.h"

#include "MarkedSpaceInlines.h"

#include "MarkingConstraintSet.h"

#include "MegamorphicCache.h"

#include "ModuleLoadingContext.h"

#include "ModuleProgramExecutable.h"

#include "ModuleRegistryEntry.h"

#include "NumberObject.h"

#include "PinballCompletion.h"

#include "PreventCollectionScope.h"

#include "ProgramExecutable.h"

#include "ProxyObject.h"

#include "SamplingProfiler.h"

#include "ShadowChicken.h"

#include "SpaceTimeMutatorScheduler.h"

#include "StochasticSpaceTimeMutatorScheduler.h"

#include "StopIfNecessaryTimer.h"

#include "StringSplitCache.h"

#include "StructureAlignedMemoryAllocator.h"

#include "SubspaceInlines.h"

#include "SuperSampler.h"

#include "SweepingScope.h"

#include "SymbolTableInlines.h"

#include "SynchronousStopTheWorldMutatorScheduler.h"

#include "TypeProfiler.h"

#include "TypeProfilerLog.h"

#include "UnlinkedEvalCodeBlock.h"

#include "VM.h"

#include "VerifierSlotVisitorInlines.h"

#include "WasmCallee.h"

#include "WeakMapImplInlines.h"

#include "WeakSetInlines.h"

#include <algorithm>

#include <wtf/AvailableMemory.h>

#include <wtf/CryptographicallyRandomNumber.h>

#include <wtf/ListDump.h>

#include <wtf/MemoryFootprint.h>

#include <wtf/RAMSize.h>

#include <wtf/Scope.h>

#include <wtf/SetForScope.h>

#include <wtf/SimpleStats.h>

#include <wtf/SystemTracing.h>

#include <wtf/TZoneMallocInlines.h>

#include <wtf/Threading.h>

#if USE(FOUNDATION)

#include <wtf/spi/cocoa/objcSPI.h>

#endif

#ifdef JSC_GLIB_API_ENABLED

#include "JSCGLibWrapperObject.h"

#endif

namespace JSC {

namespace HeapInternal {

static constexpr bool verbose = false;

static constexpr bool verboseStop = false;

}

namespace {

static double maxPauseMS(double thisPauseMS)

{

static double maxPauseMS;

maxPauseMS = std::max(thisPauseMS, maxPauseMS);

return maxPauseMS;

}

static GrowthMode NODELETE growthMode(size_t ramSize)

{

// An Aggressive heap uses more memory to go faster.

// We do this for machines with enough RAM.

size_t aggressiveHeapThresholdInBytes = static_cast<size_t>(Options::aggressiveHeapThresholdInMB()) * MB;

if (ramSize >= aggressiveHeapThresholdInBytes)

return GrowthMode::Aggressive;

return GrowthMode::Default;

}

static size_t minHeapSize(HeapType heapType, size_t ramSize)

{

switch (heapType) {

case HeapType::Large:

return static_cast<size_t>(std::min(

static_cast<double>(Options::largeHeapSize()),

ramSize * Options::smallHeapRAMFraction()));

case HeapType::Medium:

return Options::mediumHeapSize();

case HeapType::Small:

return Options::smallHeapSize();

default:

RELEASE_ASSERT_NOT_REACHED();

break;

}

static size_t NODELETE maxEdenSizeForRateLimiting(GrowthMode growthMode, size_t minBytesPerCycle)

{

// Only do rate limiting for Aggressive heaps.

if (growthMode == GrowthMode::Aggressive)

return Options::maxEdenSizeForRateLimitingMultiplier() * minBytesPerCycle;

return 0.0;

}

static size_t proportionalHeapSize(size_t heapSize, GrowthMode growthMode, size_t ramSize)

{

if (VM::isInMiniMode())

return Options::miniVMHeapGrowthFactor() * heapSize;

bool useNewHeapGrowthFactor = growthMode == GrowthMode::Aggressive;

// Use new heuristic function for Aggressive heaps (machines >= 16GB RAM).

// https://www.mathway.com/en/Algebra?asciimath=2%20*%20e%5E(-1%20*%20x)%20%2B%201%20%3Dy

// Disable it for Darwin Intel machine.

#if OS(DARWIN) && CPU(X86_64)

useNewHeapGrowthFactor = false;

#endif

if (useNewHeapGrowthFactor) {

double x = static_cast<double>(std::min(heapSize, ramSize)) / ramSize;

double ratio = Options::heapGrowthMaxIncrease() * std::exp(-(Options::heapGrowthSteepnessFactor() * x)) + 1;

return ratio * heapSize;

}

#if USE(MEMORY_FOOTPRINT_API)

size_t memoryFootprint = WTF::memoryFootprint();

if (memoryFootprint < ramSize * Options::smallHeapRAMFraction())

return Options::smallHeapGrowthFactor() * heapSize;

if (memoryFootprint < ramSize * Options::mediumHeapRAMFraction())

return Options::mediumHeapGrowthFactor() * heapSize;

#else

if (heapSize < ramSize * Options::smallHeapRAMFraction())

return Options::smallHeapGrowthFactor() * heapSize;

if (heapSize < ramSize * Options::mediumHeapRAMFraction())

return Options::mediumHeapGrowthFactor() * heapSize;

#endif

return Options::largeHeapGrowthFactor() * heapSize;

}

static void recordType(TypeCountSet& set, JSCell* cell)

{

auto typeName = "[unknown]"_s;

const ClassInfo* info = cell->classInfo();

if (info && info->className)

typeName = info->className;

set.add(typeName);

}

constexpr bool NODELETE measurePhaseTiming()

{

return false;

}

UncheckedKeyHashMap<const char*, GCTypeMap<SimpleStats>>& timingStats()

{

static UncheckedKeyHashMap<const char*, GCTypeMap<SimpleStats>>* result;

static std::once_flag once;

std::call_once(

once,

[] {

result = new UncheckedKeyHashMap<const char*, GCTypeMap<SimpleStats>>();

});

return *result;

}

SimpleStats& timingStats(const char* name, CollectionScope scope)

{

return timingStats().add(name, GCTypeMap<SimpleStats>()).iterator->value[scope];

}

class TimingScope {

public:

TimingScope(std::optional<CollectionScope> scope, ASCIILiteral name)

: m_scope(scope)

, m_name(name)

{

if (measurePhaseTiming())

m_before = MonotonicTime::now();

}

TimingScope(JSC::Heap& heap, ASCIILiteral name)

: TimingScope(heap.collectionScope(), name)

{

}

void NODELETE setScope(std::optional<CollectionScope> scope)

{

m_scope = scope;

}

void NODELETE setScope(JSC::Heap& heap)

{

setScope(heap.collectionScope());

}

~TimingScope()

{

if (measurePhaseTiming()) {

MonotonicTime after = MonotonicTime::now();

Seconds timing = after - m_before;

SimpleStats& stats = timingStats(m_name, *m_scope);

stats.add(timing.milliseconds());

dataLog("[GC:", *m_scope, "] ", m_name, " took: ", timing.milliseconds(), "ms (average ", stats.mean(), "ms).\n");

}

private:

std::optional<CollectionScope> m_scope;

MonotonicTime m_before;

ASCIILiteral m_name;

};

} // anonymous namespace

class Heap::HeapThread final : public AutomaticThread {

WTF_MAKE_TZONE_ALLOCATED_INLINE(HeapThread);

WTF_OVERRIDE_DELETE_FOR_CHECKED_PTR(HeapThread);

public:

HeapThread(const AbstractLocker& locker, JSC::Heap& heap)

: AutomaticThread(locker, heap.m_threadLock, heap.m_threadCondition.copyRef())

, m_heap(heap)

{

}

ASCIILiteral name() const final

{

return "JSC Heap Collector Thread"_s;

}

private:

PollResult poll(const AbstractLocker& locker) final

{

if (m_heap.m_threadShouldStop) {

m_heap.notifyThreadStopping(locker);

return PollResult::Stop;

}

if (m_heap.shouldCollectInCollectorThread(locker)) {

m_heap.m_collectorThreadIsRunning = true;

return PollResult::Work;

}

m_heap.m_collectorThreadIsRunning = false;

return PollResult::Wait;

}

WorkResult work() final

{

m_heap.collectInCollectorThread();

return WorkResult::Continue;

}

void threadDidStart() final

{

Thread::registerGCThread(GCThreadType::Main);

}

void threadIsStopping(const AbstractLocker&) final

{

m_heap.m_collectorThreadIsRunning = false;

}

JSC::Heap& m_heap;

};

#define INIT_SERVER_ISO_SUBSPACE(name, heapCellType, type) \

, name ISO_SUBSPACE_INIT(*this, heapCellType, type)

#define INIT_SERVER_STRUCTURE_ISO_SUBSPACE(name, heapCellType, type) \

, name(#name, *this, heapCellType, WTF::roundUpToMultipleOf<type::atomSize>(sizeof(type)), type::numberOfLowerTierPreciseCells, makeUnique<StructureAlignedMemoryAllocator>())

Heap::Heap(VM& vm, HeapType heapType)

: m_heapType(heapType)

, m_ramSize(Options::forceRAMSize() ? Options::forceRAMSize() : ramSize())

, m_growthMode(growthMode(m_ramSize))

, m_minBytesPerCycle(minHeapSize(m_heapType, m_ramSize))

, m_maxEdenSizeForRateLimiting(maxEdenSizeForRateLimiting(m_growthMode, m_minBytesPerCycle))

, m_maxEdenSize(m_minBytesPerCycle)

, m_maxHeapSize(m_minBytesPerCycle)

, m_objectSpace(this)

, m_machineThreads(makeUnique<MachineThreads>())

, m_collectorSlotVisitor(makeUnique<SlotVisitor>(*this, "C"_s))

, m_mutatorSlotVisitor(makeUnique<SlotVisitor>(*this, "M"_s))

, m_mutatorMarkStack(makeUnique<MarkStackArray>())

, m_raceMarkStack(makeUnique<MarkStackArray>())

, m_constraintSet(makeUnique<MarkingConstraintSet>(*this))

, m_strongSet(vm)

, m_codeBlocks(makeUnique<CodeBlockSet>())

, m_jitStubRoutines(makeUnique<JITStubRoutineSet>())

// We seed with 10ms so that GCActivityCallback::didAllocate doesn't continuously

// schedule the timer if we've never done a collection.

, m_fullActivityCallback(FullGCActivityCallback::tryCreate(*this))

, m_edenActivityCallback(EdenGCActivityCallback::tryCreate(*this))

, m_sweeper(adoptRef(*new IncrementalSweeper(this)))

, m_stopIfNecessaryTimer(adoptRef(*new StopIfNecessaryTimer(vm)))

, m_sharedCollectorMarkStack(makeUnique<MarkStackArray>())

, m_sharedMutatorMarkStack(makeUnique<MarkStackArray>())

, m_helperClient(&heapHelperPool())

, m_threadLock(Box<Lock>::create())

, m_threadCondition(AutomaticThreadCondition::create())

// HeapCellTypes

, auxiliaryHeapCellType(CellAttributes(DoesNotNeedDestruction, HeapCell::Auxiliary))

, immutableButterflyHeapCellType(CellAttributes(DoesNotNeedDestruction, HeapCell::JSCellWithIndexingHeader))

, cellHeapCellType(CellAttributes(DoesNotNeedDestruction, HeapCell::JSCell))

, destructibleCellHeapCellType(CellAttributes(NeedsDestruction, HeapCell::JSCell))

, apiGlobalObjectHeapCellType(IsoHeapCellType::Args<JSAPIGlobalObject>())

, callbackConstructorHeapCellType(IsoHeapCellType::Args<JSCallbackConstructor>())

, callbackGlobalObjectHeapCellType(IsoHeapCellType::Args<JSCallbackObject<JSGlobalObject>>())

, callbackObjectHeapCellType(IsoHeapCellType::Args<JSCallbackObject<JSNonFinalObject>>())

, customGetterFunctionHeapCellType(IsoHeapCellType::Args<JSCustomGetterFunction>())

, customSetterFunctionHeapCellType(IsoHeapCellType::Args<JSCustomSetterFunction>())

, dateInstanceHeapCellType(IsoHeapCellType::Args<DateInstance>())

, errorInstanceHeapCellType(IsoHeapCellType::Args<ErrorInstance>())

, finalizationRegistryCellType(IsoHeapCellType::Args<JSFinalizationRegistry>())

, globalLexicalEnvironmentHeapCellType(IsoHeapCellType::Args<JSGlobalLexicalEnvironment>())

, globalObjectHeapCellType(IsoHeapCellType::Args<JSGlobalObject>())

, injectedScriptHostSpaceHeapCellType(IsoHeapCellType::Args<Inspector::JSInjectedScriptHost>())

, javaScriptCallFrameHeapCellType(IsoHeapCellType::Args<Inspector::JSJavaScriptCallFrame>())

, jsModuleRecordHeapCellType(IsoHeapCellType::Args<JSModuleRecord>())

, syntheticModuleRecordHeapCellType(IsoHeapCellType::Args<SyntheticModuleRecord>())

, moduleNamespaceObjectHeapCellType(IsoHeapCellType::Args<JSModuleNamespaceObject>())

, nativeStdFunctionHeapCellType(IsoHeapCellType::Args<JSNativeStdFunction>())

, weakMapHeapCellType(IsoHeapCellType::Args<JSWeakMap>())

, weakSetHeapCellType(IsoHeapCellType::Args<JSWeakSet>())

#if JSC_OBJC_API_ENABLED

, apiWrapperObjectHeapCellType(IsoHeapCellType::Args<JSCallbackObject<JSAPIWrapperObject>>())

, objCCallbackFunctionHeapCellType(IsoHeapCellType::Args<ObjCCallbackFunction>())

#endif

#ifdef JSC_GLIB_API_ENABLED

, apiWrapperObjectHeapCellType(IsoHeapCellType::Args<JSCallbackObject<JSAPIWrapperObject>>())

, callbackAPIWrapperGlobalObjectHeapCellType(IsoHeapCellType::Args<JSCallbackObject<JSAPIWrapperGlobalObject>>())

, jscCallbackFunctionHeapCellType(IsoHeapCellType::Args<JSCCallbackFunction>())

#endif

, intlCollatorHeapCellType(IsoHeapCellType::Args<IntlCollator>())

, intlDateTimeFormatHeapCellType(IsoHeapCellType::Args<IntlDateTimeFormat>())

, intlDisplayNamesHeapCellType(IsoHeapCellType::Args<IntlDisplayNames>())

, intlDurationFormatHeapCellType(IsoHeapCellType::Args<IntlDurationFormat>())

, intlListFormatHeapCellType(IsoHeapCellType::Args<IntlListFormat>())

, intlLocaleHeapCellType(IsoHeapCellType::Args<IntlLocale>())

, intlNumberFormatHeapCellType(IsoHeapCellType::Args<IntlNumberFormat>())

, intlPluralRulesHeapCellType(IsoHeapCellType::Args<IntlPluralRules>())

, intlRelativeTimeFormatHeapCellType(IsoHeapCellType::Args<IntlRelativeTimeFormat>())

, intlSegmentIteratorHeapCellType(IsoHeapCellType::Args<IntlSegmentIterator>())

, intlSegmenterHeapCellType(IsoHeapCellType::Args<IntlSegmenter>())

, intlSegmentsHeapCellType(IsoHeapCellType::Args<IntlSegments>())

#if ENABLE(WEBASSEMBLY)

, webAssemblyExceptionHeapCellType(IsoHeapCellType::Args<JSWebAssemblyException>())

, webAssemblyFunctionHeapCellType(IsoHeapCellType::Args<WebAssemblyFunction>())

, webAssemblyGlobalHeapCellType(IsoHeapCellType::Args<JSWebAssemblyGlobal>())

, webAssemblyInstanceHeapCellType(IsoHeapCellType::Args<JSWebAssemblyInstance>())

, webAssemblyMemoryHeapCellType(IsoHeapCellType::Args<JSWebAssemblyMemory>())

, webAssemblyModuleHeapCellType(IsoHeapCellType::Args<JSWebAssemblyModule>())

, webAssemblyModuleRecordHeapCellType(IsoHeapCellType::Args<WebAssemblyModuleRecord>())

, webAssemblyTableHeapCellType(IsoHeapCellType::Args<JSWebAssemblyTable>())

, webAssemblyTagHeapCellType(IsoHeapCellType::Args<JSWebAssemblyTag>())

#endif

// AlignedMemoryAllocators

, fastMallocAllocator(makeUnique<FastMallocAlignedMemoryAllocator>())

, primitiveGigacageAllocator(makeUnique<GigacageAlignedMemoryAllocator>(Gigacage::Primitive))

// Subspaces

, primitiveGigacageAuxiliarySpace("Primitive Gigacage Auxiliary"_s, *this, auxiliaryHeapCellType, primitiveGigacageAllocator.get()) // Hash:0x3e7cd762

, auxiliarySpace("Auxiliary"_s, *this, auxiliaryHeapCellType, fastMallocAllocator.get()) // Hash:0x96255ba1

, immutableButterflyAuxiliarySpace("ImmutableButterfly JSCellWithIndexingHeader"_s, *this, immutableButterflyHeapCellType, fastMallocAllocator.get()) // Hash:0xaadcb3c1

, cellSpace("JSCell"_s, *this, cellHeapCellType, fastMallocAllocator.get()) // Hash:0xadfb5a79

, destructibleObjectSpace("JSDestructibleObject"_s, *this, destructibleObjectHeapCellType, fastMallocAllocator.get()) // Hash:0x4f5ed7a9

FOR_EACH_JSC_COMMON_ISO_SUBSPACE(INIT_SERVER_ISO_SUBSPACE)

FOR_EACH_JSC_STRUCTURE_ISO_SUBSPACE(INIT_SERVER_STRUCTURE_ISO_SUBSPACE)

, codeBlockSpaceAndSet ISO_SUBSPACE_INIT(*this, destructibleCellHeapCellType, CodeBlock) // Hash:0x2b743c6a

, functionExecutableSpaceAndSet ISO_SUBSPACE_INIT(*this, destructibleCellHeapCellType, FunctionExecutable) // Hash:0xbcb36268

, programExecutableSpaceAndSet ISO_SUBSPACE_INIT(*this, destructibleCellHeapCellType, ProgramExecutable) // Hash:0x4c9208f7

, unlinkedFunctionExecutableSpaceAndSet ISO_SUBSPACE_INIT(*this, destructibleCellHeapCellType, UnlinkedFunctionExecutable) // Hash:0x3ba0f4e1

{

if (Options::forceFencedBarrier()) {

m_mutatorShouldBeFenced = true;

m_barrierThreshold = tautologicalThreshold;

}

m_worldState.store(0);

for (unsigned i = 0, numberOfParallelThreads = heapHelperPool().numberOfThreads(); i < numberOfParallelThreads; ++i) {

std::unique_ptr<SlotVisitor> visitor = makeUnique<SlotVisitor>(*this, toCString("P", i + 1));

if (Options::optimizeParallelSlotVisitorsForStoppedMutator())

visitor->optimizeForStoppedMutator();

m_availableParallelSlotVisitors.append(visitor.get());

m_parallelSlotVisitors.append(WTF::move(visitor));

}

if (Options::useConcurrentGC()) {

if (Options::useStochasticMutatorScheduler())

m_scheduler = makeUnique<StochasticSpaceTimeMutatorScheduler>(*this);

else

m_scheduler = makeUnique<SpaceTimeMutatorScheduler>(*this);

} else {

// We simulate turning off concurrent GC by making the scheduler say that the world

// should always be stopped when the collector is running.

m_scheduler = makeUnique<SynchronousStopTheWorldMutatorScheduler>();

}

if (Options::verifyHeap())

m_verifier = makeUnique<HeapVerifier>(this, Options::numberOfGCCyclesToRecordForVerification());

m_collectorSlotVisitor->optimizeForStoppedMutator();

// When memory is critical, allow allocating 25% of the amount above the critical threshold before collecting.

size_t memoryAboveCriticalThreshold = static_cast<size_t>(static_cast<double>(m_ramSize) * (1.0 - Options::criticalGCMemoryThreshold()));

m_maxEdenSizeWhenCritical = memoryAboveCriticalThreshold / 4;

Locker locker { *m_threadLock };

lazyInitialize(m_thread, adoptRef(*new HeapThread(locker, *this)));

}

#undef INIT_SERVER_ISO_SUBSPACE

#undef INIT_SERVER_STRUCTURE_ISO_SUBSPACE

Heap::~Heap()

{

// Scribble m_worldState to make it clear that the heap has already been destroyed if we crash in checkConn

m_worldState.store(0xbadbeeffu);

forEachSlotVisitor(

[&] (SlotVisitor& visitor) {

visitor.clearMarkStacks();

});

m_mutatorMarkStack->clear();

m_raceMarkStack->clear();

for (WeakBlock* block : m_logicallyEmptyWeakBlocks)

WeakBlock::destroy(*this, block);

}

bool Heap::isPagedOut()

{

return m_objectSpace.isPagedOut();

}

void Heap::dumpHeapStatisticsAtVMDestruction()

{

unsigned counter = 0;

HeapIterationScope iterationScope(*this);

m_objectSpace.forEachBlock([&] (MarkedBlock::Handle* block) {

unsigned live = 0;

block->forEachLiveCell([&] (size_t, HeapCell*, HeapCell::Kind) {

live++;

return IterationStatus::Continue;

});

dataLogLn("[", counter++, "] ", block->cellSize(), ", ", live, " / ", block->cellsPerBlock(), " ", static_cast<double>(live) / block->cellsPerBlock() * 100, "% ", block->attributes(), " ", block->subspace()->name());

block->forEachLiveCell([&] (size_t, HeapCell* heapCell, HeapCell::Kind kind) {

if (kind == HeapCell::Kind::JSCell) {

auto* cell = static_cast<JSCell*>(heapCell);

if (cell->isObject())

dataLogLn(" ", JSValue((JSObject*)cell));

else

dataLogLn(" ", *cell);

}

return IterationStatus::Continue;

});

}

// The VM is being destroyed and the collector will never run again.

// Run all pending finalizers now because we won't get another chance.

void Heap::lastChanceToFinalize()

{

MonotonicTime before;

if (Options::logGC()) [[unlikely]] {

before = MonotonicTime::now();

dataLog("[GC<", RawPointer(this), ">: shutdown ");

}

m_isShuttingDown = true;

RELEASE_ASSERT(!vm().entryScope);

RELEASE_ASSERT(m_mutatorState == MutatorState::Running);

if (m_collectContinuouslyThread) {

{

Locker locker { m_collectContinuouslyLock };

m_shouldStopCollectingContinuously = true;

m_collectContinuouslyCondition.notifyOne();

}

m_collectContinuouslyThread->waitForCompletion();

}

dataLogIf(Options::logGC(), "1");

// Prevent new collections from being started. This is probably not even necessary, since we're not

// going to call into anything that starts collections. Still, this makes the algorithm more

// obviously sound.

m_isSafeToCollect = false;

dataLogIf(Options::logGC(), "2");

bool isCollecting;

{

Locker locker { *m_threadLock };

RELEASE_ASSERT(m_lastServedTicket <= m_lastGrantedTicket);

isCollecting = m_lastServedTicket < m_lastGrantedTicket;

}

if (isCollecting) {

dataLogIf(Options::logGC(), "...]\n");

// Wait for the current collection to finish.

waitForCollector(

[&] (const AbstractLocker&) -> bool {

RELEASE_ASSERT(m_lastServedTicket <= m_lastGrantedTicket);

return m_lastServedTicket == m_lastGrantedTicket;

});

dataLogIf(Options::logGC(), "[GC<", RawPointer(this), ">: shutdown ");

}

dataLogIf(Options::logGC(), "3");

RELEASE_ASSERT(m_requests.isEmpty());

RELEASE_ASSERT(m_lastServedTicket == m_lastGrantedTicket);

// Carefully bring the thread down.

bool stopped = false;

{

Locker locker { *m_threadLock };

stopped = m_thread->tryStop(locker);

m_threadShouldStop = true;

if (!stopped)

m_threadCondition->notifyOne(locker);

}

dataLogIf(Options::logGC(), "4");

if (!stopped)

m_thread->join();

dataLogIf(Options::logGC(), "5 ");

if (Options::dumpHeapStatisticsAtVMDestruction()) [[unlikely]]

dumpHeapStatisticsAtVMDestruction();

m_arrayBuffers.lastChanceToFinalize();

m_objectSpace.lastChanceToFinalize();

releaseDelayedReleasedObjects();

#if ENABLE(WEBASSEMBLY)

Wasm::TypeInformation::cleanupIfRequested();

#endif

sweepAllLogicallyEmptyWeakBlocks();

m_objectSpace.freeMemory();

dataLogIf(Options::logGC(), (MonotonicTime::now() - before).milliseconds(), "ms]\n");

}

void Heap::releaseDelayedReleasedObjects()

{

#if USE(FOUNDATION) || defined(JSC_GLIB_API_ENABLED)

// We need to guard against the case that releasing an object can create more objects due to the

// release calling into JS. When those JS call(s) exit and all locks are being dropped we end up

// back here and could try to recursively release objects. We guard that with a recursive entry

// count. Only the initial call will release objects, recursive calls simple return and let the

// the initial call to the function take care of any objects created during release time.

// This also means that we need to loop until there are no objects in m_delayedReleaseObjects

// and use a temp Vector for the actual releasing.

if (!m_delayedReleaseRecursionCount++) {

while (!m_delayedReleaseObjects.isEmpty()) {

ASSERT(vm().currentThreadIsHoldingAPILock());

auto objectsToRelease = WTF::move(m_delayedReleaseObjects);

{

// We need to drop locks before calling out to arbitrary code.

JSLock::DropAllLocks dropAllLocks(vm());

#if USE(FOUNDATION)

void* context = objc_autoreleasePoolPush();

#endif

objectsToRelease.clear();

#if USE(FOUNDATION)

objc_autoreleasePoolPop(context);

#endif

}

m_delayedReleaseRecursionCount--;

#endif

}

void Heap::reportExtraMemoryAllocatedPossiblyFromAlreadyMarkedCell(const JSCell* cell, size_t size)

{

ASSERT(cell);

// Increasing extraMemory of already marked objects will not be visible as a retained memory.

// We need to report this additionally to tell GC that we get additional extra memory now,

// and GC needs to consider scheduling GC based on this increase.

if (mutatorShouldBeFenced()) [[unlikely]] {

// In this case, the barrierThreshold is the tautological threshold, so cell could still be

// not black. But we can't know for sure until we fire off a fence.

WTF::storeLoadFence();

if (cell->cellState() != CellState::PossiblyBlack)

return;

WTF::loadLoadFence();

if (!isMarked(cell)) {

// During a full collection a store into an unmarked object that had surivived past

// collections will manifest as a store to an unmarked PossiblyBlack object. If the

// object gets marked at some time after this then it will go down the normal marking

// path. So, we don't have to remember this object. We could return here. But we go

// further and attempt to re-white the object.

ASSERT(m_collectionScope && m_collectionScope.value() == CollectionScope::Full);

return;

}

} else

ASSERT(isMarked(cell));

// It could be that the object was *just* marked. This means that the collector may set the

// state to DefinitelyGrey and then to PossiblyOldOrBlack at any time. It's OK for us to

// race with the collector here. If we win then this is accurate because the object _will_

// get scanned again. If we lose then someone else will barrier the object again. That would

// be unfortunate but not the end of the world.

reportExtraMemoryVisited(size);

}

void Heap::reportExtraMemoryAllocatedSlowCase(GCDeferralContext* deferralContext, const JSCell* cell, size_t size)

{

didAllocate(size);

if (cell) {

if (isWithinThreshold(cell->cellState(), barrierThreshold())) [[unlikely]]

reportExtraMemoryAllocatedPossiblyFromAlreadyMarkedCell(cell, size);

}

collectIfNecessaryOrDefer(deferralContext);

}

void Heap::deprecatedReportExtraMemorySlowCase(size_t size)

{

// FIXME: Change this to use SaturatingArithmetic when available.

// https://bugs.webkit.org/show_bug.cgi?id=170411

CheckedSize checkedNewSize = m_deprecatedExtraMemorySize;

checkedNewSize += size;

size_t newSize = std::numeric_limits<size_t>::max();

if (!checkedNewSize.hasOverflowed()) [[likely]]

newSize = checkedNewSize.value();

m_deprecatedExtraMemorySize = newSize;

reportExtraMemoryAllocatedSlowCase(nullptr, nullptr, size);

}

bool Heap::overCriticalMemoryThreshold(MemoryThresholdCallType memoryThresholdCallType)

{

#if USE(MEMORY_FOOTPRINT_API)

if (memoryThresholdCallType == MemoryThresholdCallType::Direct || ++m_percentAvailableMemoryCachedCallCount >= 100) {

m_overCriticalMemoryThreshold = WTF::percentAvailableMemoryInUse() > Options::criticalGCMemoryThreshold();

m_percentAvailableMemoryCachedCallCount = 0;

}

return m_overCriticalMemoryThreshold;

#else

UNUSED_PARAM(memoryThresholdCallType);

return false;

#endif

}

void Heap::reportAbandonedObjectGraph()

{

// Our clients don't know exactly how much memory they

// are abandoning so we just guess for them.

size_t abandonedBytes = static_cast<size_t>(0.1 * capacity());

m_bytesAbandonedSinceLastFullCollect += abandonedBytes;

// We want to accelerate the next collection. Because memory has just

// been abandoned, the next collection has the potential to

// be more profitable. Since allocation is the trigger for collection,

// we hasten the next collection by pretending that we've allocated more memory.

if (m_fullActivityCallback) {

m_fullActivityCallback->didAllocate(*this,

m_sizeAfterLastCollect - m_sizeAfterLastFullCollect + totalBytesAllocatedThisCycle() + m_bytesAbandonedSinceLastFullCollect);

}

void Heap::protect(JSValue k)

{

ASSERT(k);

ASSERT(vm().currentThreadIsHoldingAPILock());

if (!k.isCell())

return;

m_protectedValues.add(k.asCell());

}

bool Heap::unprotect(JSValue k)

{

ASSERT(k);

ASSERT(vm().currentThreadIsHoldingAPILock());

if (!k.isCell())

return false;

return m_protectedValues.remove(k.asCell());

}

void Heap::addReference(JSCell* cell, ArrayBuffer* buffer)

{

if (m_arrayBuffers.addReference(cell, buffer)) {

collectIfNecessaryOrDefer();

didAllocate(buffer->gcSizeEstimateInBytes());

}

template<typename CellType, typename CellSet>

void Heap::reconcileWeakReferencesInMarkedCells(CellSet& cellSet, CollectionScope collectionScope)

{

cellSet.forEachMarkedCell(

[&] (HeapCell* cell, HeapCell::Kind) {

static_cast<CellType*>(cell)->reconcileWeakReferencesAtGCEnd(vm(), collectionScope);

});

}

// Weak reference reconciliation: settle every untraced pointer against the liveness that

// marking just established. Must run after marking, because isMarked() only means "dead"

// once the closure is complete, and before sweeping, because a dying referent may still

// need to be identified or read.

void Heap::reconcileWeakReferencesAtGCEnd()

{

CollectionScope collectionScope = this->collectionScope().value_or(CollectionScope::Full);

{

// Executables go before CodeBlock, since CodeBlock::reconcileWeakReferencesAtGCEnd looks at the owner executable's installed CodeBlock.

// FunctionExecutable requires all live instances to be processed, so iterate the whole space rather than a tracking set.

reconcileWeakReferencesInMarkedCells<FunctionExecutable>(functionExecutableSpaceAndSet.space, collectionScope);

reconcileWeakReferencesInMarkedCells<ProgramExecutable>(programExecutableSpaceAndSet.weakReconciliationSet, collectionScope);

if (m_evalExecutableSpace)

reconcileWeakReferencesInMarkedCells<EvalExecutable>(m_evalExecutableSpace->weakReconciliationSet, collectionScope);

if (m_moduleProgramExecutableSpace)

reconcileWeakReferencesInMarkedCells<ModuleProgramExecutable>(m_moduleProgramExecutableSpace->weakReconciliationSet, collectionScope);

}

reconcileWeakReferencesInMarkedCells<SymbolTable>(symbolTableSpace, collectionScope);

forEachCodeBlockSpace(

[&] (auto& space) {

this->reconcileWeakReferencesInMarkedCells<CodeBlock>(space.set, collectionScope);

});

if (collectionScope == CollectionScope::Full) {

reconcileWeakReferencesInMarkedCells<Structure>(structureSpace, collectionScope);

reconcileWeakReferencesInMarkedCells<BrandedStructure>(brandedStructureSpace, collectionScope);

#if ENABLE(WEBASSEMBLY)

reconcileWeakReferencesInMarkedCells<WebAssemblyGCStructure>(webAssemblyGCStructureSpace, collectionScope);

#endif

}

reconcileWeakReferencesInMarkedCells<StructureRareData>(structureRareDataSpace, collectionScope);

reconcileWeakReferencesInMarkedCells<UnlinkedFunctionExecutable>(unlinkedFunctionExecutableSpaceAndSet.set, collectionScope);

if (m_weakSetSpace)

reconcileWeakReferencesInMarkedCells<JSWeakSet>(*m_weakSetSpace, collectionScope);

if (m_weakMapSpace)

reconcileWeakReferencesInMarkedCells<JSWeakMap>(*m_weakMapSpace, collectionScope);

if (m_weakObjectRefSpace)

reconcileWeakReferencesInMarkedCells<JSWeakObjectRef>(*m_weakObjectRefSpace, collectionScope);

if (m_errorInstanceSpace)

reconcileWeakReferencesInMarkedCells<ErrorInstance>(*m_errorInstanceSpace, collectionScope);

// FinalizationRegistries currently rely on serial finalization because they can post tasks to the deferredWorkTimer, which normally expects tasks to only be posted by the API lock holder.

if (m_finalizationRegistrySpace)

reconcileWeakReferencesInMarkedCells<JSFinalizationRegistry>(*m_finalizationRegistrySpace, collectionScope);

#if ENABLE(WEBASSEMBLY)

if (m_webAssemblyInstanceSpace)

reconcileWeakReferencesInMarkedCells<JSWebAssemblyInstance>(*m_webAssemblyInstanceSpace, collectionScope);

#endif

vm().reconcileWeakReferencesAtGCEnd();

}

void Heap::willStartIterating()

{

m_objectSpace.willStartIterating();

}

void Heap::didFinishIterating()

{

m_objectSpace.didFinishIterating();

}

void Heap::completeAllJITPlans()

{

if (!Options::useJIT())

return;

#if ENABLE(JIT)

JITWorklist::ensureGlobalWorklist().completeAllPlansForVM(vm());

#endif // ENABLE(JIT)

}

template<typename Visitor>

void Heap::iterateExecutingAndCompilingCodeBlocks(Visitor& visitor, NOESCAPE const Function<void(CodeBlock*)>& func)

{

m_codeBlocks->iterateCurrentlyExecuting(func);

#if ENABLE(JIT)

if (Options::useJIT())

JITWorklist::ensureGlobalWorklist().iterateCodeBlocksForGC(visitor, vm(), func);

#else

UNUSED_PARAM(visitor);

#endif // ENABLE(JIT)

}

template<typename Func, typename Visitor>

void Heap::iterateExecutingAndCompilingCodeBlocksWithoutHoldingLocks(Visitor& visitor, const Func& func)

{

Vector<CodeBlock*, 256> codeBlocks;

iterateExecutingAndCompilingCodeBlocks(visitor,

[&] (CodeBlock* codeBlock) {

codeBlocks.append(codeBlock);

});

for (CodeBlock* codeBlock : codeBlocks)

func(codeBlock);

}

void Heap::assertMarkStacksEmpty()

{

bool ok = true;

if (!m_sharedCollectorMarkStack->isEmpty()) {

dataLog("FATAL: Shared collector mark stack not empty! It has ", m_sharedCollectorMarkStack->size(), " elements.\n");

ok = false;

}

if (!m_sharedMutatorMarkStack->isEmpty()) {

dataLog("FATAL: Shared mutator mark stack not empty! It has ", m_sharedMutatorMarkStack->size(), " elements.\n");

ok = false;

}

forEachSlotVisitor(

[&] (SlotVisitor& visitor) {

if (visitor.isEmpty())

return;

dataLog("FATAL: Visitor ", RawPointer(&visitor), " is not empty!\n");

ok = false;

});

RELEASE_ASSERT(ok);

}

void Heap::gatherStackRoots(ConservativeRoots& roots)

{

m_machineThreads->gatherConservativeRoots(roots, *m_jitStubRoutines, *m_codeBlocks, m_currentThreadState, m_currentThread);

#if ENABLE(C_LOOP)

vm().cloopStack().gatherConservativeRoots(roots, *m_jitStubRoutines, *m_codeBlocks);

#endif

}

void Heap::gatherVMRoots(ConservativeRoots& roots)

{

VM& vm = this->vm();

#if ENABLE(DFG_JIT)

if (Options::useJIT()) {

vm.gatherScratchBufferRoots(roots);

vm.scanSideState(roots);

}

#endif

#if !ENABLE(DFG_JIT)

UNUSED_PARAM(roots);

UNUSED_VARIABLE(vm);

#endif

}

void Heap::beginMarking()

{

TimingScope timingScope(*this, "Heap::beginMarking"_s);

m_jitStubRoutines->clearMarks();

m_objectSpace.beginMarking();

vm().beginMarking();

setMutatorShouldBeFenced(true);

}

void Heap::removeDeadCompilerWorklistEntries()

{

if (!Options::useJIT())

return;

#if ENABLE(JIT)

JITWorklist::ensureGlobalWorklist().removeDeadPlans(vm());

#endif // ENABLE(JIT)

}

struct GatherExtraHeapData : MarkedBlock::CountFunctor {

GatherExtraHeapData(HeapAnalyzer& analyzer)

: m_analyzer(analyzer)

{

}

IterationStatus operator()(HeapCell* heapCell, HeapCell::Kind kind) const

{

if (isJSCellKind(kind)) {

JSCell* cell = static_cast<JSCell*>(heapCell);

cell->methodTable()->analyzeHeap(cell, m_analyzer);

}

return IterationStatus::Continue;

}

HeapAnalyzer& m_analyzer;

};

void Heap::gatherExtraHeapData(HeapProfiler& heapProfiler)

{

if (auto* analyzer = heapProfiler.activeHeapAnalyzer()) {

HeapIterationScope heapIterationScope(*this);

GatherExtraHeapData functor(*analyzer);

m_objectSpace.forEachLiveCell(heapIterationScope, functor);

}

struct RemoveDeadHeapSnapshotNodes : MarkedBlock::CountFunctor {

RemoveDeadHeapSnapshotNodes(HeapSnapshot& snapshot)

: m_snapshot(snapshot)

{

}

IterationStatus operator()(HeapCell* cell, HeapCell::Kind kind) const

{

if (isJSCellKind(kind))

m_snapshot.sweepCell(static_cast<JSCell*>(cell));

return IterationStatus::Continue;

}

HeapSnapshot& m_snapshot;

};

void Heap::removeDeadHeapSnapshotNodes(HeapProfiler& heapProfiler)

{

if (HeapSnapshot* snapshot = heapProfiler.mostRecentSnapshot()) {

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