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2874 lines (2451 loc) · 106 KB
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/*
* Copyright (C) 2003-2026 Apple Inc. All rights reserved.
* Copyright (C) 2007 Eric Seidel <eric@webkit.org>
* Copyright (C) 2026 Igalia S.L.
*
* 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 "CollectorInlines.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 "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 "JSONCache.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 "StopIfNecessaryTimer.h"
#include "StringSplitCache.h"
#include "StructureAlignedMemoryAllocator.h"
#include "SubspaceInlines.h"
#include "SuperSampler.h"
#include "SweepingScope.h"
#include "SymbolTableInlines.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/SpinBackoff.h>
#include <wtf/StringPrintStream.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 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
#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 ""_s, *this, heapCellType, WTF::roundUpToMultipleOf<type::atomSize>(sizeof(type)), type::numberOfLowerTierPreciseCells, structureAllocator.get())
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_collector(makeUnique<Collector>(*this))
, m_mutatorSlotVisitor(makeUnique<SlotVisitor>(*m_collector, "M"_s))
, m_mutatorMarkStack(makeUnique<MarkStackArray>())
, 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)))
// 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>())
, 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))
, structureAllocator(makeUnique<StructureAlignedMemoryAllocator>())
// 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);
if (Options::verifyHeap())
m_verifier = makeUnique<HeapVerifier>(this, Options::numberOfGCCyclesToRecordForVerification());
// 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;
}
#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);
m_mutatorMarkStack->clear();
while (WeakBlock* block = m_detachedWeakBlocks.removeHead())
WeakBlock::destroy(*this, block);
destroyAllPooledWeakBlocks();
ASSERT(!m_weakBlockCount);
}
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.
void Heap::shutDown()
{
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);
// The collect-continuously thread requests a collection whenever the queue is empty, so it has to
// stop before the queue drains.
m_collector->stopCollectingContinuously();
dataLogIf(Options::logGC(), "stopped collecting continuously, ");
// 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(), "disabled collection, ");
if (m_collector->hasOutstandingRequest()) {
dataLogIf(Options::logGC(), "waiting for outstanding collections...]\n");
waitForAllCollections();
dataLogIf(Options::logGC(), "[GC<", RawPointer(this), ">: shutdown: ");
}
dataLogIf(Options::logGC(), "no collection pending, stopping the collector thread, ");
m_collector->stopThread();
dataLogIf(Options::logGC(), "stopped, ");
if (Options::dumpHeapStatisticsAtVMDestruction()) [[unlikely]]
dumpHeapStatisticsAtVMDestruction();
lastChanceToFinalize();
dataLogIf(Options::logGC(), (MonotonicTime::now() - before).milliseconds(), "ms]\n");
}
// Run all pending finalizers now because we won't get another chance.
void Heap::lastChanceToFinalize()
{
m_arrayBuffers.lastChanceToFinalize();
m_objectSpace.lastChanceToFinalize();
releaseDelayedReleasedObjects();
#if ENABLE(WEBASSEMBLY)
Wasm::TypeInformation::cleanupIfRequested();
#endif
m_objectSpace.freeMemory();
}
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();
if (auto* clientData = vm().clientData)
clientData->reconcileWeakReferencesAtGCEnd(vm(), collectionScope);
}
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, NOESCAPE const Func& func)
{
Vector<CodeBlock*, 256> codeBlocks;
iterateExecutingAndCompilingCodeBlocks(visitor,
[&] (CodeBlock* codeBlock) {
codeBlocks.append(codeBlock);
});
for (CodeBlock* codeBlock : codeBlocks)
func(codeBlock);
}
// Collector::runEndPhase calls this from another translation unit, which cannot instantiate a
// definition that lives here.
template void Heap::iterateExecutingAndCompilingCodeBlocks<SlotVisitor>(SlotVisitor&, NOESCAPE const Function<void(CodeBlock*)>&);
void Heap::gatherStackRoots(ConservativeRoots& roots)
{
m_machineThreads->gatherConservativeRoots(roots, *m_jitStubRoutines, *m_codeBlocks, m_collector->m_conductingMutatorState, m_collector->m_conductorThread);
#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);
ASSERT(m_collectionScope);
if (*m_collectionScope == CollectionScope::Full)
m_mutatorMarkStack->clear();
m_jitStubRoutines->clearMarks();
m_objectSpace.beginMarking();
vm().beginMarking();
setMutatorShouldBeFenced(true);
#if ENABLE(WEBASSEMBLY)
beginMarkingWasmCallees();
#endif
}
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()) {
HeapIterationScope heapIterationScope(*this);
RemoveDeadHeapSnapshotNodes functor(*snapshot);
m_objectSpace.forEachDeadCell(heapIterationScope, functor);
snapshot->shrinkToFit();
}
}
void Heap::updateObjectCounts()
{
if (m_collectionScope && m_collectionScope.value() == CollectionScope::Full) {
m_totalBytesVisitedAfterLastFullCollect = m_totalBytesVisited;
m_totalBytesVisited = 0;
}
m_totalBytesVisitedThisCycle = m_collector->bytesVisited();
m_totalBytesVisited += m_totalBytesVisitedThisCycle;
}
void Heap::endMarking()
{
m_objectSpace.endMarking();
setMutatorShouldBeFenced(Options::forceFencedBarrier());
#if ENABLE(WEBASSEMBLY)
releaseUnmarkedWasmCallees();
#endif
}
size_t Heap::objectCount()
{
return m_objectSpace.objectCount();
}
size_t Heap::extraMemorySize()
{
// FIXME: Change this to use SaturatingArithmetic when available.
// https://bugs.webkit.org/show_bug.cgi?id=170411
CheckedSize checkedTotal = m_extraMemorySize;
checkedTotal += m_deprecatedExtraMemorySize;
checkedTotal += m_arrayBuffers.size();
size_t total = std::numeric_limits<size_t>::max();
if (!checkedTotal.hasOverflowed()) [[likely]]
total = checkedTotal.value();
// It would be nice to have `ASSERT(m_objectSpace.capacity() >= m_objectSpace.size());` here but `m_objectSpace.size()`
// requires having heap access which thread might not. Specifically, we might be called from the resource usage thread.
return std::min(total, std::numeric_limits<size_t>::max() - m_objectSpace.capacity());
}
size_t Heap::size()
{
return m_objectSpace.size() + extraMemorySize();
}
size_t Heap::capacity()
{
return m_objectSpace.capacity() + extraMemorySize();
}
size_t Heap::protectedGlobalObjectCount()
{
size_t result = 0;
forEachProtectedCell(
[&] (JSCell* cell) {
if (cell->isObject() && asObject(cell)->isGlobalObject())
result++;
});
return result;
}
size_t Heap::globalObjectCount()
{
HeapIterationScope iterationScope(*this);
size_t result = 0;
m_objectSpace.forEachLiveCell(
iterationScope,
[&] (HeapCell* heapCell, HeapCell::Kind kind) -> IterationStatus {
if (!isJSCellKind(kind))
return IterationStatus::Continue;
JSCell* cell = static_cast<JSCell*>(heapCell);
if (cell->isObject() && asObject(cell)->isGlobalObject())
result++;
return IterationStatus::Continue;
});
return result;
}
size_t Heap::protectedObjectCount()
{
size_t result = 0;
forEachProtectedCell(
[&] (JSCell*) {
result++;
});
return result;
}
TypeCountSet Heap::protectedObjectTypeCounts()
{
TypeCountSet result;
forEachProtectedCell(
[&] (JSCell* cell) {
recordType(result, cell);
});
return result;
}
TypeCountSet Heap::objectTypeCounts()
{
TypeCountSet result;
HeapIterationScope iterationScope(*this);
m_objectSpace.forEachLiveCell(
iterationScope,
[&] (HeapCell* cell, HeapCell::Kind kind) -> IterationStatus {
if (isJSCellKind(kind))
recordType(result, static_cast<JSCell*>(cell));
return IterationStatus::Continue;
});
return result;
}
void Heap::deleteAllCodeBlocks(DeleteAllCodeEffort effort)
{
if (m_collectionScope && effort == DeleteAllCodeIfNotCollecting)
return;
VM& vm = this->vm();
PreventCollectionScope preventCollectionScope(*this);
// If JavaScript is running, it's not safe to delete all JavaScript code, since
// we'll end up returning to deleted code.
RELEASE_ASSERT(!vm.entryScope);
RELEASE_ASSERT(!m_collectionScope);
completeAllJITPlans();
forEachScriptExecutableSpace(
[&] (auto& spaceAndSet) {
HeapIterationScope heapIterationScope(*this);