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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/*
* [SMDOC] Garbage Collector
*
* This code implements an incremental mark-and-sweep garbage collector, with
* most sweeping carried out in the background on a parallel thread.
*
* Full vs. zone GC
* ----------------
*
* The collector can collect all zones at once, or a subset. These types of
* collection are referred to as a full GC and a zone GC respectively.
*
* It is possible for an incremental collection that started out as a full GC to
* become a zone GC if new zones are created during the course of the
* collection.
*
* Incremental collection
* ----------------------
*
* For a collection to be carried out incrementally the following conditions
* must be met:
* - the collection must be run by calling js::GCSlice() rather than js::GC()
* - the GC parameter JSGC_INCREMENTAL_GC_ENABLED must be true.
*
* The last condition is an engine-internal mechanism to ensure that incremental
* collection is not carried out without the correct barriers being implemented.
* For more information see 'Incremental marking' below.
*
* If the collection is not incremental, all foreground activity happens inside
* a single call to GC() or GCSlice(). However the collection is not complete
* until the background sweeping activity has finished.
*
* An incremental collection proceeds as a series of slices, interleaved with
* mutator activity, i.e. running JavaScript code. Slices are limited by a time
* budget. The slice finishes as soon as possible after the requested time has
* passed.
*
* Collector states
* ----------------
*
* The collector proceeds through the following states, the current state being
* held in JSRuntime::gcIncrementalState:
*
* - Prepare - unmarks GC things, discards JIT code and other setup
* - MarkRoots - marks the stack and other roots
* - Mark - incrementally marks reachable things
* - Sweep - sweeps zones in groups and continues marking unswept zones
* - Finalize - performs background finalization, concurrent with mutator
* - Compact - incrementally compacts by zone
* - Decommit - performs background decommit and chunk removal
*
* Roots are marked in the first MarkRoots slice; this is the start of the GC
* proper. The following states can take place over one or more slices.
*
* In other words an incremental collection proceeds like this:
*
* Slice 1: Prepare: Starts background task to unmark GC things
*
* ... JS code runs, background unmarking finishes ...
*
* Slice 2: MarkRoots: Roots are pushed onto the mark stack.
* Mark: The mark stack is processed by popping an element,
* marking it, and pushing its children.
*
* ... JS code runs ...
*
* Slice 3: Mark: More mark stack processing.
*
* ... JS code runs ...
*
* Slice n-1: Mark: More mark stack processing.
*
* ... JS code runs ...
*
* Slice n: Mark: Mark stack is completely drained.
* Sweep: Select first group of zones to sweep and sweep them.
*
* ... JS code runs ...
*
* Slice n+1: Sweep: Mark objects in unswept zones that were newly
* identified as alive (see below). Then sweep more zone
* sweep groups.
*
* ... JS code runs ...
*
* Slice n+2: Sweep: Mark objects in unswept zones that were newly
* identified as alive. Then sweep more zones.
*
* ... JS code runs ...
*
* Slice m: Sweep: Sweeping is finished, and background sweeping
* started on the helper thread.
*
* ... JS code runs, remaining sweeping done on background thread ...
*
* When background sweeping finishes the GC is complete.
*
* Incremental marking
* -------------------
*
* Incremental collection requires close collaboration with the mutator (i.e.,
* JS code) to guarantee correctness.
*
* - During an incremental GC, if a memory location (except a root) is written
* to, then the value it previously held must be marked. Write barriers
* ensure this.
*
* - Any object that is allocated during incremental GC must start out marked.
*
* - Roots are marked in the first slice and hence don't need write barriers.
* Roots are things like the C stack and the VM stack.
*
* The problem that write barriers solve is that between slices the mutator can
* change the object graph. We must ensure that it cannot do this in such a way
* that makes us fail to mark a reachable object (marking an unreachable object
* is tolerable).
*
* We use a snapshot-at-the-beginning algorithm to do this. This means that we
* promise to mark at least everything that is reachable at the beginning of
* collection. To implement it we mark the old contents of every non-root memory
* location written to by the mutator while the collection is in progress, using
* write barriers. This is described in gc/Barrier.h.
*
* Incremental sweeping
* --------------------
*
* Sweeping is difficult to do incrementally because object finalizers must be
* run at the start of sweeping, before any mutator code runs. The reason is
* that some objects use their finalizers to remove themselves from caches. If
* mutator code was allowed to run after the start of sweeping, it could observe
* the state of the cache and create a new reference to an object that was just
* about to be destroyed.
*
* Sweeping all finalizable objects in one go would introduce long pauses, so
* instead sweeping broken up into groups of zones. Zones which are not yet
* being swept are still marked, so the issue above does not apply.
*
* The order of sweeping is restricted by cross compartment pointers - for
* example say that object |a| from zone A points to object |b| in zone B and
* neither object was marked when we transitioned to the Sweep phase. Imagine we
* sweep B first and then return to the mutator. It's possible that the mutator
* could cause |a| to become alive through a read barrier (perhaps it was a
* shape that was accessed via a shape table). Then we would need to mark |b|,
* which |a| points to, but |b| has already been swept.
*
* So if there is such a pointer then marking of zone B must not finish before
* marking of zone A. Pointers which form a cycle between zones therefore
* restrict those zones to being swept at the same time, and these are found
* using Tarjan's algorithm for finding the strongly connected components of a
* graph.
*
* GC things without finalizers, and things with finalizers that are able to run
* in the background, are swept on the background thread. This accounts for most
* of the sweeping work.
*
* Reset
* -----
*
* During incremental collection it is possible, although unlikely, for
* conditions to change such that incremental collection is no longer safe. In
* this case, the collection is 'reset' by resetIncrementalGC(). If we are in
* the mark state, this just stops marking, but if we have started sweeping
* already, we continue non-incrementally until we have swept the current sweep
* group. Following a reset, a new collection is started.
*
* Compacting GC
* -------------
*
* Compacting GC happens at the end of a major GC as part of the last slice.
* There are three parts:
*
* - Arenas are selected for compaction.
* - The contents of those arenas are moved to new arenas.
* - All references to moved things are updated.
*
* Collecting Atoms
* ----------------
*
* Atoms are collected differently from other GC things. They are contained in
* a special zone and things in other zones may have pointers to them that are
* not recorded in the cross compartment pointer map. Each zone holds a bitmap
* with the atoms it might be keeping alive, and atoms are only collected if
* they are not included in any zone's atom bitmap. See AtomMarking.cpp for how
* this bitmap is managed.
*/
#include "gc/GC-inl.h"
#include "mozilla/Range.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/TextUtils.h"
#include "mozilla/TimeStamp.h"
#include <algorithm>
#include <initializer_list>
#include <iterator>
#include <stdlib.h>
#include <string.h>
#include <utility>
#include "jsapi.h" // JS_AbortIfWrongThread
#include "jstypes.h"
#include "debugger/DebugAPI.h"
#include "gc/ClearEdgesTracer.h"
#include "gc/GCContext.h"
#include "gc/GCInternals.h"
#include "gc/GCLock.h"
#include "gc/GCProbes.h"
#include "gc/Memory.h"
#include "gc/ParallelMarking.h"
#include "gc/ParallelWork.h"
#include "gc/WeakMap.h"
#include "jit/ExecutableAllocator.h"
#include "jit/JitCode.h"
#include "jit/JitRuntime.h"
#include "jit/ProcessExecutableMemory.h"
#include "js/HeapAPI.h" // JS::GCCellPtr
#include "js/Printer.h"
#include "js/SliceBudget.h"
#include "util/DifferentialTesting.h"
#include "vm/BigIntType.h"
#include "vm/EnvironmentObject.h"
#include "vm/GetterSetter.h"
#include "vm/HelperThreadState.h"
#include "vm/JitActivation.h"
#include "vm/JSObject.h"
#include "vm/JSScript.h"
#include "vm/PropMap.h"
#include "vm/Realm.h"
#include "vm/Shape.h"
#include "vm/StringType.h"
#include "vm/SymbolType.h"
#include "vm/Time.h"
#include "gc/Heap-inl.h"
#include "gc/Nursery-inl.h"
#include "gc/ObjectKind-inl.h"
#include "gc/PrivateIterators-inl.h"
#include "vm/GeckoProfiler-inl.h"
#include "vm/JSContext-inl.h"
#include "vm/Realm-inl.h"
#include "vm/Stack-inl.h"
using namespace js;
using namespace js::gc;
using mozilla::MakeScopeExit;
using mozilla::Maybe;
using mozilla::Nothing;
using mozilla::Some;
using mozilla::TimeDuration;
using mozilla::TimeStamp;
using JS::AutoGCRooter;
const AllocKind gc::slotsToThingKind[] = {
// clang-format off
/* 0 */ AllocKind::OBJECT0, AllocKind::OBJECT2, AllocKind::OBJECT2, AllocKind::OBJECT4,
/* 4 */ AllocKind::OBJECT4, AllocKind::OBJECT8, AllocKind::OBJECT8, AllocKind::OBJECT8,
/* 8 */ AllocKind::OBJECT8, AllocKind::OBJECT12, AllocKind::OBJECT12, AllocKind::OBJECT12,
/* 12 */ AllocKind::OBJECT12, AllocKind::OBJECT16, AllocKind::OBJECT16, AllocKind::OBJECT16,
/* 16 */ AllocKind::OBJECT16
// clang-format on
};
static_assert(std::size(slotsToThingKind) == SLOTS_TO_THING_KIND_LIMIT,
"We have defined a slot count for each kind.");
// A table converting an object size in "slots" (increments of
// sizeof(js::Value)) to the total number of bytes in the corresponding
// AllocKind. See gc::slotsToThingKind. This primarily allows wasm jit code to
// remain compliant with the AllocKind system.
//
// To use this table, subtract sizeof(NativeObject) from your desired allocation
// size, divide by sizeof(js::Value) to get the number of "slots", and then
// index into this table. See gc::GetGCObjectKindForBytes.
const constexpr uint32_t gc::slotsToAllocKindBytes[] = {
// These entries correspond exactly to gc::slotsToThingKind. The numeric
// comments therefore indicate the number of slots that the "bytes" would
// correspond to.
// clang-format off
/* 0 */ sizeof(JSObject_Slots0), sizeof(JSObject_Slots2), sizeof(JSObject_Slots2), sizeof(JSObject_Slots4),
/* 4 */ sizeof(JSObject_Slots4), sizeof(JSObject_Slots8), sizeof(JSObject_Slots8), sizeof(JSObject_Slots8),
/* 8 */ sizeof(JSObject_Slots8), sizeof(JSObject_Slots12), sizeof(JSObject_Slots12), sizeof(JSObject_Slots12),
/* 12 */ sizeof(JSObject_Slots12), sizeof(JSObject_Slots16), sizeof(JSObject_Slots16), sizeof(JSObject_Slots16),
/* 16 */ sizeof(JSObject_Slots16)
// clang-format on
};
static_assert(std::size(slotsToAllocKindBytes) == SLOTS_TO_THING_KIND_LIMIT);
MOZ_THREAD_LOCAL(JS::GCContext*) js::TlsGCContext;
JS::GCContext::GCContext(JSRuntime* runtime) : runtime_(runtime) {}
JS::GCContext::~GCContext() {
MOZ_ASSERT(!hasJitCodeToPoison());
MOZ_ASSERT(!isCollecting());
MOZ_ASSERT(gcUse() == GCUse::None);
MOZ_ASSERT(!gcSweepZone());
MOZ_ASSERT(!isTouchingGrayThings());
}
void JS::GCContext::poisonJitCode() {
if (hasJitCodeToPoison()) {
jit::ExecutableAllocator::poisonCode(runtime(), jitPoisonRanges);
jitPoisonRanges.clearAndFree();
}
}
#ifdef DEBUG
void GCRuntime::verifyAllChunks() {
AutoLockGC lock(this);
fullChunks(lock).verifyChunks();
availableChunks(lock).verifyChunks();
emptyChunks(lock).verifyChunks();
}
#endif
void GCRuntime::setMinEmptyChunkCount(uint32_t value, const AutoLockGC& lock) {
minEmptyChunkCount_ = value;
if (minEmptyChunkCount_ > maxEmptyChunkCount_) {
maxEmptyChunkCount_ = minEmptyChunkCount_;
}
MOZ_ASSERT(maxEmptyChunkCount_ >= minEmptyChunkCount_);
}
void GCRuntime::setMaxEmptyChunkCount(uint32_t value, const AutoLockGC& lock) {
maxEmptyChunkCount_ = value;
if (minEmptyChunkCount_ > maxEmptyChunkCount_) {
minEmptyChunkCount_ = maxEmptyChunkCount_;
}
MOZ_ASSERT(maxEmptyChunkCount_ >= minEmptyChunkCount_);
}
inline bool GCRuntime::tooManyEmptyChunks(const AutoLockGC& lock) {
return emptyChunks(lock).count() > minEmptyChunkCount(lock);
}
ChunkPool GCRuntime::expireEmptyChunkPool(const AutoLockGC& lock) {
MOZ_ASSERT(emptyChunks(lock).verify());
MOZ_ASSERT(minEmptyChunkCount(lock) <= maxEmptyChunkCount(lock));
ChunkPool expired;
while (tooManyEmptyChunks(lock)) {
TenuredChunk* chunk = emptyChunks(lock).pop();
prepareToFreeChunk(chunk->info);
expired.push(chunk);
}
MOZ_ASSERT(expired.verify());
MOZ_ASSERT(emptyChunks(lock).verify());
MOZ_ASSERT(emptyChunks(lock).count() <= maxEmptyChunkCount(lock));
MOZ_ASSERT(emptyChunks(lock).count() <= minEmptyChunkCount(lock));
return expired;
}
static void FreeChunkPool(ChunkPool& pool) {
for (ChunkPool::Iter iter(pool); !iter.done();) {
TenuredChunk* chunk = iter.get();
iter.next();
pool.remove(chunk);
MOZ_ASSERT(chunk->unused());
UnmapPages(static_cast<void*>(chunk), ChunkSize);
}
MOZ_ASSERT(pool.count() == 0);
}
void GCRuntime::freeEmptyChunks(const AutoLockGC& lock) {
FreeChunkPool(emptyChunks(lock));
}
inline void GCRuntime::prepareToFreeChunk(TenuredChunkInfo& info) {
MOZ_ASSERT(numArenasFreeCommitted >= info.numArenasFreeCommitted);
numArenasFreeCommitted -= info.numArenasFreeCommitted;
stats().count(gcstats::COUNT_DESTROY_CHUNK);
#ifdef DEBUG
/*
* Let FreeChunkPool detect a missing prepareToFreeChunk call before it
* frees chunk.
*/
info.numArenasFreeCommitted = 0;
#endif
}
void GCRuntime::releaseArena(Arena* arena, const AutoLockGC& lock) {
MOZ_ASSERT(arena->allocated());
MOZ_ASSERT(!arena->onDelayedMarkingList());
MOZ_ASSERT(TlsGCContext.get()->isFinalizing());
arena->zone->gcHeapSize.removeGCArena(heapSize);
arena->release(lock);
arena->chunk()->releaseArena(this, arena, lock);
}
GCRuntime::GCRuntime(JSRuntime* rt)
: rt(rt),
systemZone(nullptr),
mainThreadContext(rt),
heapState_(JS::HeapState::Idle),
stats_(this),
sweepingTracer(rt),
fullGCRequested(false),
helperThreadRatio(TuningDefaults::HelperThreadRatio),
maxHelperThreads(TuningDefaults::MaxHelperThreads),
helperThreadCount(1),
maxMarkingThreads(TuningDefaults::MaxMarkingThreads),
markingThreadCount(1),
createBudgetCallback(nullptr),
minEmptyChunkCount_(TuningDefaults::MinEmptyChunkCount),
maxEmptyChunkCount_(TuningDefaults::MaxEmptyChunkCount),
rootsHash(256),
nextCellUniqueId_(LargestTaggedNullCellPointer +
1), // Ensure disjoint from null tagged pointers.
numArenasFreeCommitted(0),
verifyPreData(nullptr),
lastGCStartTime_(TimeStamp::Now()),
lastGCEndTime_(TimeStamp::Now()),
incrementalGCEnabled(TuningDefaults::IncrementalGCEnabled),
perZoneGCEnabled(TuningDefaults::PerZoneGCEnabled),
numActiveZoneIters(0),
cleanUpEverything(false),
grayBitsValid(true),
majorGCTriggerReason(JS::GCReason::NO_REASON),
minorGCNumber(0),
majorGCNumber(0),
number(0),
sliceNumber(0),
isFull(false),
incrementalState(gc::State::NotActive),
initialState(gc::State::NotActive),
useZeal(false),
lastMarkSlice(false),
safeToYield(true),
markOnBackgroundThreadDuringSweeping(false),
useBackgroundThreads(false),
#ifdef DEBUG
hadShutdownGC(false),
#endif
requestSliceAfterBackgroundTask(false),
lifoBlocksToFree((size_t)JSContext::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE),
lifoBlocksToFreeAfterFullMinorGC(
(size_t)JSContext::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE),
lifoBlocksToFreeAfterNextMinorGC(
(size_t)JSContext::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE),
sweepGroupIndex(0),
sweepGroups(nullptr),
currentSweepGroup(nullptr),
sweepZone(nullptr),
abortSweepAfterCurrentGroup(false),
sweepMarkResult(IncrementalProgress::NotFinished),
#ifdef DEBUG
testMarkQueue(rt),
#endif
startedCompacting(false),
zonesCompacted(0),
#ifdef DEBUG
relocatedArenasToRelease(nullptr),
#endif
#ifdef JS_GC_ZEAL
markingValidator(nullptr),
#endif
defaultTimeBudgetMS_(TuningDefaults::DefaultTimeBudgetMS),
incrementalAllowed(true),
compactingEnabled(TuningDefaults::CompactingEnabled),
parallelMarkingEnabled(TuningDefaults::ParallelMarkingEnabled),
rootsRemoved(false),
#ifdef JS_GC_ZEAL
zealModeBits(0),
zealFrequency(0),
nextScheduled(0),
deterministicOnly(false),
zealSliceBudget(0),
selectedForMarking(rt),
#endif
fullCompartmentChecks(false),
gcCallbackDepth(0),
alwaysPreserveCode(false),
lowMemoryState(false),
lock(mutexid::GCLock),
storeBufferLock(mutexid::StoreBuffer),
delayedMarkingLock(mutexid::GCDelayedMarkingLock),
allocTask(this, emptyChunks_.ref()),
unmarkTask(this),
markTask(this),
sweepTask(this),
freeTask(this),
decommitTask(this),
nursery_(this),
storeBuffer_(rt),
lastAllocRateUpdateTime(TimeStamp::Now()) {
}
using CharRange = mozilla::Range<const char>;
using CharRangeVector = Vector<CharRange, 0, SystemAllocPolicy>;
static bool SplitStringBy(const CharRange& text, char delimiter,
CharRangeVector* result) {
auto start = text.begin();
for (auto ptr = start; ptr != text.end(); ptr++) {
if (*ptr == delimiter) {
if (!result->emplaceBack(start, ptr)) {
return false;
}
start = ptr + 1;
}
}
return result->emplaceBack(start, text.end());
}
static bool ParseTimeDuration(const CharRange& text,
TimeDuration* durationOut) {
const char* str = text.begin().get();
char* end;
long millis = strtol(str, &end, 10);
*durationOut = TimeDuration::FromMilliseconds(double(millis));
return str != end && end == text.end().get();
}
static void PrintProfileHelpAndExit(const char* envName, const char* helpText) {
fprintf(stderr, "%s=N[,(main|all)]\n", envName);
fprintf(stderr, "%s", helpText);
exit(0);
}
void js::gc::ReadProfileEnv(const char* envName, const char* helpText,
bool* enableOut, bool* workersOut,
TimeDuration* thresholdOut) {
*enableOut = false;
*workersOut = false;
*thresholdOut = TimeDuration::Zero();
const char* env = getenv(envName);
if (!env) {
return;
}
if (strcmp(env, "help") == 0) {
PrintProfileHelpAndExit(envName, helpText);
}
CharRangeVector parts;
auto text = CharRange(env, strlen(env));
if (!SplitStringBy(text, ',', &parts)) {
MOZ_CRASH("OOM parsing environment variable");
}
if (parts.length() == 0 || parts.length() > 2) {
PrintProfileHelpAndExit(envName, helpText);
}
*enableOut = true;
if (!ParseTimeDuration(parts[0], thresholdOut)) {
PrintProfileHelpAndExit(envName, helpText);
}
if (parts.length() == 2) {
const char* threads = parts[1].begin().get();
if (strcmp(threads, "all") == 0) {
*workersOut = true;
} else if (strcmp(threads, "main") != 0) {
PrintProfileHelpAndExit(envName, helpText);
}
}
}
bool js::gc::ShouldPrintProfile(JSRuntime* runtime, bool enable,
bool profileWorkers, TimeDuration threshold,
TimeDuration duration) {
return enable && (runtime->isMainRuntime() || profileWorkers) &&
duration >= threshold;
}
#ifdef JS_GC_ZEAL
void GCRuntime::getZealBits(uint32_t* zealBits, uint32_t* frequency,
uint32_t* scheduled) {
*zealBits = zealModeBits;
*frequency = zealFrequency;
*scheduled = nextScheduled;
}
const char gc::ZealModeHelpText[] =
" Specifies how zealous the garbage collector should be. Some of these "
"modes can\n"
" be set simultaneously, by passing multiple level options, e.g. \"2;4\" "
"will activate\n"
" both modes 2 and 4. Modes can be specified by name or number.\n"
" \n"
" Values:\n"
" 0: (None) Normal amount of collection (resets all modes)\n"
" 1: (RootsChange) Collect when roots are added or removed\n"
" 2: (Alloc) Collect when every N allocations (default: 100)\n"
" 4: (VerifierPre) Verify pre write barriers between instructions\n"
" 6: (YieldBeforeRootMarking) Incremental GC in two slices that yields "
"before root marking\n"
" 7: (GenerationalGC) Collect the nursery every N nursery allocations\n"
" 8: (YieldBeforeMarking) Incremental GC in two slices that yields "
"between\n"
" the root marking and marking phases\n"
" 9: (YieldBeforeSweeping) Incremental GC in two slices that yields "
"between\n"
" the marking and sweeping phases\n"
" 10: (IncrementalMultipleSlices) Incremental GC in many slices\n"
" 11: (IncrementalMarkingValidator) Verify incremental marking\n"
" 12: (ElementsBarrier) Use the individual element post-write barrier\n"
" regardless of elements size\n"
" 13: (CheckHashTablesOnMinorGC) Check internal hashtables on minor GC\n"
" 14: (Compact) Perform a shrinking collection every N allocations\n"
" 15: (CheckHeapAfterGC) Walk the heap to check its integrity after "
"every GC\n"
" 17: (YieldBeforeSweepingAtoms) Incremental GC in two slices that "
"yields\n"
" before sweeping the atoms table\n"
" 18: (CheckGrayMarking) Check gray marking invariants after every GC\n"
" 19: (YieldBeforeSweepingCaches) Incremental GC in two slices that "
"yields\n"
" before sweeping weak caches\n"
" 21: (YieldBeforeSweepingObjects) Incremental GC in two slices that "
"yields\n"
" before sweeping foreground finalized objects\n"
" 22: (YieldBeforeSweepingNonObjects) Incremental GC in two slices that "
"yields\n"
" before sweeping non-object GC things\n"
" 23: (YieldBeforeSweepingPropMapTrees) Incremental GC in two slices "
"that "
"yields\n"
" before sweeping shape trees\n"
" 24: (CheckWeakMapMarking) Check weak map marking invariants after "
"every GC\n"
" 25: (YieldWhileGrayMarking) Incremental GC in two slices that yields\n"
" during gray marking\n";
// The set of zeal modes that control incremental slices. These modes are
// mutually exclusive.
static const mozilla::EnumSet<ZealMode> IncrementalSliceZealModes = {
ZealMode::YieldBeforeRootMarking,
ZealMode::YieldBeforeMarking,
ZealMode::YieldBeforeSweeping,
ZealMode::IncrementalMultipleSlices,
ZealMode::YieldBeforeSweepingAtoms,
ZealMode::YieldBeforeSweepingCaches,
ZealMode::YieldBeforeSweepingObjects,
ZealMode::YieldBeforeSweepingNonObjects,
ZealMode::YieldBeforeSweepingPropMapTrees};
void GCRuntime::setZeal(uint8_t zeal, uint32_t frequency) {
MOZ_ASSERT(zeal <= unsigned(ZealMode::Limit));
if (verifyPreData) {
VerifyBarriers(rt, PreBarrierVerifier);
}
if (zeal == 0) {
if (hasZealMode(ZealMode::GenerationalGC)) {
evictNursery();
nursery().leaveZealMode();
}
if (isIncrementalGCInProgress()) {
finishGC(JS::GCReason::DEBUG_GC);
}
}
ZealMode zealMode = ZealMode(zeal);
if (zealMode == ZealMode::GenerationalGC) {
evictNursery(JS::GCReason::EVICT_NURSERY);
nursery().enterZealMode();
}
// Some modes are mutually exclusive. If we're setting one of those, we
// first reset all of them.
if (IncrementalSliceZealModes.contains(zealMode)) {
for (auto mode : IncrementalSliceZealModes) {
clearZealMode(mode);
}
}
bool schedule = zealMode >= ZealMode::Alloc;
if (zeal != 0) {
zealModeBits |= 1 << unsigned(zeal);
} else {
zealModeBits = 0;
}
zealFrequency = frequency;
nextScheduled = schedule ? frequency : 0;
}
void GCRuntime::unsetZeal(uint8_t zeal) {
MOZ_ASSERT(zeal <= unsigned(ZealMode::Limit));
ZealMode zealMode = ZealMode(zeal);
if (!hasZealMode(zealMode)) {
return;
}
if (verifyPreData) {
VerifyBarriers(rt, PreBarrierVerifier);
}
if (zealMode == ZealMode::GenerationalGC) {
evictNursery();
nursery().leaveZealMode();
}
clearZealMode(zealMode);
if (zealModeBits == 0) {
if (isIncrementalGCInProgress()) {
finishGC(JS::GCReason::DEBUG_GC);
}
zealFrequency = 0;
nextScheduled = 0;
}
}
void GCRuntime::setNextScheduled(uint32_t count) { nextScheduled = count; }
static bool ParseZealModeName(const CharRange& text, uint32_t* modeOut) {
struct ModeInfo {
const char* name;
size_t length;
uint32_t value;
};
static const ModeInfo zealModes[] = {{"None", 0},
# define ZEAL_MODE(name, value) {#name, strlen(#name), value},
JS_FOR_EACH_ZEAL_MODE(ZEAL_MODE)
# undef ZEAL_MODE
};
for (auto mode : zealModes) {
if (text.length() == mode.length &&
memcmp(text.begin().get(), mode.name, mode.length) == 0) {
*modeOut = mode.value;
return true;
}
}
return false;
}
static bool ParseZealModeNumericParam(const CharRange& text,
uint32_t* paramOut) {
if (text.length() == 0) {
return false;
}
for (auto c : text) {
if (!mozilla::IsAsciiDigit(c)) {
return false;
}
}
*paramOut = atoi(text.begin().get());
return true;
}
static bool PrintZealHelpAndFail() {
fprintf(stderr, "Format: JS_GC_ZEAL=level(;level)*[,N]\n");
fputs(ZealModeHelpText, stderr);
return false;
}
bool GCRuntime::parseAndSetZeal(const char* str) {
// Set the zeal mode from a string consisting of one or more mode specifiers
// separated by ';', optionally followed by a ',' and the trigger frequency.
// The mode specifiers can by a mode name or its number.
auto text = CharRange(str, strlen(str));
CharRangeVector parts;
if (!SplitStringBy(text, ',', &parts)) {
return false;
}
if (parts.length() == 0 || parts.length() > 2) {
return PrintZealHelpAndFail();
}
uint32_t frequency = JS_DEFAULT_ZEAL_FREQ;
if (parts.length() == 2 && !ParseZealModeNumericParam(parts[1], &frequency)) {
return PrintZealHelpAndFail();
}
CharRangeVector modes;
if (!SplitStringBy(parts[0], ';', &modes)) {
return false;
}
for (const auto& descr : modes) {
uint32_t mode;
if (!ParseZealModeName(descr, &mode) &&
!(ParseZealModeNumericParam(descr, &mode) &&
mode <= unsigned(ZealMode::Limit))) {
return PrintZealHelpAndFail();
}
setZeal(mode, frequency);
}
return true;
}
const char* js::gc::AllocKindName(AllocKind kind) {
static const char* const names[] = {
# define EXPAND_THING_NAME(allocKind, _1, _2, _3, _4, _5, _6) #allocKind,
FOR_EACH_ALLOCKIND(EXPAND_THING_NAME)
# undef EXPAND_THING_NAME
};
static_assert(std::size(names) == AllocKindCount,
"names array should have an entry for every AllocKind");
size_t i = size_t(kind);
MOZ_ASSERT(i < std::size(names));
return names[i];
}
void js::gc::DumpArenaInfo() {
fprintf(stderr, "Arena header size: %zu\n\n", ArenaHeaderSize);
fprintf(stderr, "GC thing kinds:\n");
fprintf(stderr, "%25s %8s %8s %8s\n",
"AllocKind:", "Size:", "Count:", "Padding:");
for (auto kind : AllAllocKinds()) {
fprintf(stderr, "%25s %8zu %8zu %8zu\n", AllocKindName(kind),
Arena::thingSize(kind), Arena::thingsPerArena(kind),
Arena::firstThingOffset(kind) - ArenaHeaderSize);
}
}
#endif // JS_GC_ZEAL
bool GCRuntime::init(uint32_t maxbytes) {
MOZ_ASSERT(!wasInitialized());
MOZ_ASSERT(SystemPageSize());
Arena::checkLookupTables();
if (!TlsGCContext.init()) {
return false;
}
TlsGCContext.set(&mainThreadContext.ref());
updateHelperThreadCount();
#ifdef JS_GC_ZEAL
const char* size = getenv("JSGC_MARK_STACK_LIMIT");
if (size) {
maybeMarkStackLimit = atoi(size);
}
#endif
if (!updateMarkersVector()) {
return false;
}
{
AutoLockGCBgAlloc lock(this);
MOZ_ALWAYS_TRUE(tunables.setParameter(JSGC_MAX_BYTES, maxbytes));
if (!nursery().init(lock)) {
return false;
}
}
#ifdef JS_GC_ZEAL
const char* zealSpec = getenv("JS_GC_ZEAL");
if (zealSpec && zealSpec[0] && !parseAndSetZeal(zealSpec)) {
return false;
}
#endif
for (auto& marker : markers) {
if (!marker->init()) {
return false;
}
}
if (!initSweepActions()) {
return false;
}
UniquePtr<Zone> zone = MakeUnique<Zone>(rt, Zone::AtomsZone);
if (!zone || !zone->init()) {
return false;
}
// The atoms zone is stored as the first element of the zones vector.
MOZ_ASSERT(zone->isAtomsZone());
MOZ_ASSERT(zones().empty());
MOZ_ALWAYS_TRUE(zones().reserve(1)); // ZonesVector has inline capacity 4.
zones().infallibleAppend(zone.release());
gcprobes::Init(this);
initialized = true;
return true;
}
void GCRuntime::finish() {
MOZ_ASSERT(inPageLoadCount == 0);
MOZ_ASSERT(!sharedAtomsZone_);
// Wait for nursery background free to end and disable it to release memory.
if (nursery().isEnabled()) {
nursery().disable();
}
// Wait until the background finalization and allocation stops and the
// helper thread shuts down before we forcefully release any remaining GC
// memory.
sweepTask.join();
markTask.join();
freeTask.join();
allocTask.cancelAndWait();
decommitTask.cancelAndWait();
#ifdef DEBUG
{
MOZ_ASSERT(dispatchedParallelTasks == 0);
AutoLockHelperThreadState lock;
MOZ_ASSERT(queuedParallelTasks.ref().isEmpty(lock));
}
#endif
releaseMarkingThreads();
#ifdef JS_GC_ZEAL
// Free memory associated with GC verification.
finishVerifier();
#endif
// Delete all remaining zones.
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
AutoSetThreadIsSweeping threadIsSweeping(rt->gcContext(), zone);
for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) {
for (RealmsInCompartmentIter realm(comp); !realm.done(); realm.next()) {
js_delete(realm.get());
}
comp->realms().clear();
js_delete(comp.get());
}
zone->compartments().clear();
js_delete(zone.get());
}
zones().clear();
FreeChunkPool(fullChunks_.ref());
FreeChunkPool(availableChunks_.ref());
FreeChunkPool(emptyChunks_.ref());
TlsGCContext.set(nullptr);
gcprobes::Finish(this);
nursery().printTotalProfileTimes();
stats().printTotalProfileTimes();
}
bool GCRuntime::freezeSharedAtomsZone() {
// This is called just after permanent atoms and well-known symbols have been
// created. At this point all existing atoms and symbols are permanent.
//
// This method makes the current atoms zone into a shared atoms zone and
// removes it from the zones list. Everything in it is marked black. A new
// empty atoms zone is created, where all atoms local to this runtime will
// live.
//
// The shared atoms zone will not be collected until shutdown when it is
// returned to the zone list by restoreSharedAtomsZone().
MOZ_ASSERT(rt->isMainRuntime());
MOZ_ASSERT(!sharedAtomsZone_);
MOZ_ASSERT(zones().length() == 1);
MOZ_ASSERT(atomsZone());
MOZ_ASSERT(!atomsZone()->wasGCStarted());
MOZ_ASSERT(!atomsZone()->needsIncrementalBarrier());
AutoAssertEmptyNursery nurseryIsEmpty(rt->mainContextFromOwnThread());
atomsZone()->arenas.clearFreeLists();
for (auto kind : AllAllocKinds()) {
for (auto thing =
atomsZone()->cellIterUnsafe<TenuredCell>(kind, nurseryIsEmpty);
!thing.done(); thing.next()) {
TenuredCell* cell = thing.getCell();
MOZ_ASSERT((cell->is<JSString>() &&
cell->as<JSString>()->isPermanentAndMayBeShared()) ||
(cell->is<JS::Symbol>() &&
cell->as<JS::Symbol>()->isPermanentAndMayBeShared()));
cell->markBlack();
}
}
sharedAtomsZone_ = atomsZone();
zones().clear();
UniquePtr<Zone> zone = MakeUnique<Zone>(rt, Zone::AtomsZone);
if (!zone || !zone->init()) {
return false;
}
MOZ_ASSERT(zone->isAtomsZone());
zones().infallibleAppend(zone.release());
return true;
}
void GCRuntime::restoreSharedAtomsZone() {
// Return the shared atoms zone to the zone list. This allows the contents of
// the shared atoms zone to be collected when the parent runtime is shut down.
if (!sharedAtomsZone_) {
return;
}
MOZ_ASSERT(rt->isMainRuntime());
MOZ_ASSERT(rt->childRuntimeCount == 0);
AutoEnterOOMUnsafeRegion oomUnsafe;
if (!zones().append(sharedAtomsZone_)) {
oomUnsafe.crash("restoreSharedAtomsZone");
}
sharedAtomsZone_ = nullptr;
}
bool GCRuntime::setParameter(JSContext* cx, JSGCParamKey key, uint32_t value) {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
AutoStopVerifyingBarriers pauseVerification(rt, false);
FinishGC(cx);
waitBackgroundSweepEnd();
AutoLockGC lock(this);
return setParameter(key, value, lock);
}
static bool IsGCThreadParameter(JSGCParamKey key) {
return key == JSGC_HELPER_THREAD_RATIO || key == JSGC_MAX_HELPER_THREADS ||
key == JSGC_MAX_MARKING_THREADS;
}
bool GCRuntime::setParameter(JSGCParamKey key, uint32_t value,
AutoLockGC& lock) {
switch (key) {
case JSGC_SLICE_TIME_BUDGET_MS:
defaultTimeBudgetMS_ = value;
break;
case JSGC_INCREMENTAL_GC_ENABLED:
setIncrementalGCEnabled(value != 0);
break;
case JSGC_PER_ZONE_GC_ENABLED:
perZoneGCEnabled = value != 0;
break;
case JSGC_COMPACTING_ENABLED:
compactingEnabled = value != 0;
break;
case JSGC_PARALLEL_MARKING_ENABLED:
setParallelMarkingEnabled(value != 0);
break;
case JSGC_INCREMENTAL_WEAKMAP_ENABLED:
for (auto& marker : markers) {
marker->incrementalWeakMapMarkingEnabled = value != 0;
}
break;
case JSGC_SEMISPACE_NURSERY_ENABLED: {
AutoUnlockGC unlock(lock);
nursery().setSemispaceEnabled(value);
break;
}
case JSGC_MIN_EMPTY_CHUNK_COUNT:
setMinEmptyChunkCount(value, lock);
break;
case JSGC_MAX_EMPTY_CHUNK_COUNT:
setMaxEmptyChunkCount(value, lock);
break;
default:
if (IsGCThreadParameter(key)) {
return setThreadParameter(key, value, lock);
}
if (!tunables.setParameter(key, value)) {
return false;
}
updateAllGCStartThresholds();
}
return true;
}
bool GCRuntime::setThreadParameter(JSGCParamKey key, uint32_t value,
AutoLockGC& lock) {
if (rt->parentRuntime) {
// Don't allow these to be set for worker runtimes.
return false;
}
switch (key) {
case JSGC_HELPER_THREAD_RATIO:
if (value == 0) {
return false;
}
helperThreadRatio = double(value) / 100.0;
break;
case JSGC_MAX_HELPER_THREADS:
if (value == 0) {
return false;
}
maxHelperThreads = value;
break;
case JSGC_MAX_MARKING_THREADS:
maxMarkingThreads = std::min(size_t(value), MaxParallelWorkers);
break;
default:
MOZ_CRASH("Unexpected parameter key");
}
updateHelperThreadCount();
initOrDisableParallelMarking();
return true;
}
void GCRuntime::resetParameter(JSContext* cx, JSGCParamKey key) {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
AutoStopVerifyingBarriers pauseVerification(rt, false);
FinishGC(cx);
waitBackgroundSweepEnd();
AutoLockGC lock(this);
resetParameter(key, lock);
}
void GCRuntime::resetParameter(JSGCParamKey key, AutoLockGC& lock) {
switch (key) {
case JSGC_SLICE_TIME_BUDGET_MS:
defaultTimeBudgetMS_ = TuningDefaults::DefaultTimeBudgetMS;
break;
case JSGC_INCREMENTAL_GC_ENABLED:
setIncrementalGCEnabled(TuningDefaults::IncrementalGCEnabled);
break;
case JSGC_PER_ZONE_GC_ENABLED:
perZoneGCEnabled = TuningDefaults::PerZoneGCEnabled;
break;
case JSGC_COMPACTING_ENABLED:
compactingEnabled = TuningDefaults::CompactingEnabled;
break;
case JSGC_PARALLEL_MARKING_ENABLED:
setParallelMarkingEnabled(TuningDefaults::ParallelMarkingEnabled);
break;
case JSGC_INCREMENTAL_WEAKMAP_ENABLED:
for (auto& marker : markers) {
marker->incrementalWeakMapMarkingEnabled =
TuningDefaults::IncrementalWeakMapMarkingEnabled;
}
break;
case JSGC_SEMISPACE_NURSERY_ENABLED: {
AutoUnlockGC unlock(lock);
nursery().setSemispaceEnabled(TuningDefaults::SemispaceNurseryEnabled);
break;
}
case JSGC_MIN_EMPTY_CHUNK_COUNT:
setMinEmptyChunkCount(TuningDefaults::MinEmptyChunkCount, lock);
break;
case JSGC_MAX_EMPTY_CHUNK_COUNT:
setMaxEmptyChunkCount(TuningDefaults::MaxEmptyChunkCount, lock);
break;
default:
if (IsGCThreadParameter(key)) {
resetThreadParameter(key, lock);
return;
}
tunables.resetParameter(key);
updateAllGCStartThresholds();
}
}
void GCRuntime::resetThreadParameter(JSGCParamKey key, AutoLockGC& lock) {
if (rt->parentRuntime) {
return;
}
switch (key) {
case JSGC_HELPER_THREAD_RATIO:
helperThreadRatio = TuningDefaults::HelperThreadRatio;
break;
case JSGC_MAX_HELPER_THREADS:
maxHelperThreads = TuningDefaults::MaxHelperThreads;
break;
case JSGC_MAX_MARKING_THREADS:
maxMarkingThreads = TuningDefaults::MaxMarkingThreads;
break;
default:
MOZ_CRASH("Unexpected parameter key");
}
updateHelperThreadCount();
initOrDisableParallelMarking();
}
uint32_t GCRuntime::getParameter(JSGCParamKey key) {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
AutoLockGC lock(this);
return getParameter(key, lock);
}
uint32_t GCRuntime::getParameter(JSGCParamKey key, const AutoLockGC& lock) {
switch (key) {
case JSGC_BYTES:
return uint32_t(heapSize.bytes());
case JSGC_NURSERY_BYTES:
return nursery().capacity();
case JSGC_NUMBER:
return uint32_t(number);
case JSGC_MAJOR_GC_NUMBER:
return uint32_t(majorGCNumber);
case JSGC_MINOR_GC_NUMBER:
return uint32_t(minorGCNumber);
case JSGC_INCREMENTAL_GC_ENABLED:
return incrementalGCEnabled;
case JSGC_PER_ZONE_GC_ENABLED:
return perZoneGCEnabled;
case JSGC_UNUSED_CHUNKS:
return uint32_t(emptyChunks(lock).count());
case JSGC_TOTAL_CHUNKS:
return uint32_t(fullChunks(lock).count() + availableChunks(lock).count() +
emptyChunks(lock).count());
case JSGC_SLICE_TIME_BUDGET_MS:
MOZ_RELEASE_ASSERT(defaultTimeBudgetMS_ >= 0);
MOZ_RELEASE_ASSERT(defaultTimeBudgetMS_ <= UINT32_MAX);
return uint32_t(defaultTimeBudgetMS_);
case JSGC_MIN_EMPTY_CHUNK_COUNT:
return minEmptyChunkCount(lock);
case JSGC_MAX_EMPTY_CHUNK_COUNT:
return maxEmptyChunkCount(lock);
case JSGC_COMPACTING_ENABLED:
return compactingEnabled;
case JSGC_PARALLEL_MARKING_ENABLED:
return parallelMarkingEnabled;
case JSGC_INCREMENTAL_WEAKMAP_ENABLED:
return marker().incrementalWeakMapMarkingEnabled;
case JSGC_SEMISPACE_NURSERY_ENABLED:
return nursery().semispaceEnabled();
case JSGC_CHUNK_BYTES:
return ChunkSize;
case JSGC_HELPER_THREAD_RATIO:
MOZ_ASSERT(helperThreadRatio > 0.0);
return uint32_t(helperThreadRatio * 100.0);
case JSGC_MAX_HELPER_THREADS:
MOZ_ASSERT(maxHelperThreads <= UINT32_MAX);
return maxHelperThreads;
case JSGC_HELPER_THREAD_COUNT:
return helperThreadCount;
case JSGC_MAX_MARKING_THREADS:
return maxMarkingThreads;
case JSGC_MARKING_THREAD_COUNT:
return markingThreadCount;
case JSGC_SYSTEM_PAGE_SIZE_KB:
return SystemPageSize() / 1024;
default:
return tunables.getParameter(key);
}
}
#ifdef JS_GC_ZEAL
void GCRuntime::setMarkStackLimit(size_t limit, AutoLockGC& lock) {
MOZ_ASSERT(!JS::RuntimeHeapIsBusy());
maybeMarkStackLimit = limit;
AutoUnlockGC unlock(lock);
AutoStopVerifyingBarriers pauseVerification(rt, false);
for (auto& marker : markers) {
marker->setMaxCapacity(limit);
}
}
#endif
void GCRuntime::setIncrementalGCEnabled(bool enabled) {
incrementalGCEnabled = enabled;
}
void GCRuntime::updateHelperThreadCount() {
if (!CanUseExtraThreads()) {
// startTask will run the work on the main thread if the count is 1.
MOZ_ASSERT(helperThreadCount == 1);
markingThreadCount = 1;
AutoLockHelperThreadState lock;
maxParallelThreads = 1;
return;
}
// Number of extra threads required during parallel marking to ensure we can
// start the necessary marking tasks. Background free and background
// allocation may already be running and we want to avoid these tasks blocking
// marking. In real configurations there will be enough threads that this
// won't affect anything.
static constexpr size_t SpareThreadsDuringParallelMarking = 2;
// Calculate the target thread count for GC parallel tasks.
size_t cpuCount = GetHelperThreadCPUCount();
helperThreadCount =
std::clamp(size_t(double(cpuCount) * helperThreadRatio.ref()), size_t(1),
maxHelperThreads.ref());
// Calculate the target thread count for parallel marking, which uses separate
// parameters to let us adjust this independently.
markingThreadCount = std::min(cpuCount / 2, maxMarkingThreads.ref());
// Calculate the overall target thread count taking into account the separate
// target for parallel marking threads. Add spare threads to avoid blocking
// parallel marking when there is other GC work happening.
size_t targetCount =
std::max(helperThreadCount.ref(),
markingThreadCount.ref() + SpareThreadsDuringParallelMarking);
// Attempt to create extra threads if possible. This is not supported when
// using an external thread pool.
AutoLockHelperThreadState lock;
(void)HelperThreadState().ensureThreadCount(targetCount, lock);
// Limit all thread counts based on the number of threads available, which may
// be fewer than requested.
size_t availableThreadCount = GetHelperThreadCount();
MOZ_ASSERT(availableThreadCount != 0);
targetCount = std::min(targetCount, availableThreadCount);
helperThreadCount = std::min(helperThreadCount.ref(), availableThreadCount);
if (availableThreadCount < SpareThreadsDuringParallelMarking) {
markingThreadCount = 1;
} else {
markingThreadCount =
std::min(markingThreadCount.ref(),
availableThreadCount - SpareThreadsDuringParallelMarking);
}
// Update the maximum number of threads that will be used for GC work.
maxParallelThreads = targetCount;
}
size_t GCRuntime::markingWorkerCount() const {
if (!CanUseExtraThreads() || !parallelMarkingEnabled) {
return 1;
}
if (markingThreadCount) {
return markingThreadCount;
}
// Limit parallel marking to use at most two threads initially.
return 2;
}
#ifdef DEBUG
void GCRuntime::assertNoMarkingWork() const {
for (const auto& marker : markers) {
MOZ_ASSERT(marker->isDrained());
}
MOZ_ASSERT(!hasDelayedMarking());
}
#endif
bool GCRuntime::setParallelMarkingEnabled(bool enabled) {
if (enabled == parallelMarkingEnabled) {
return true;
}
parallelMarkingEnabled = enabled;
return initOrDisableParallelMarking();
}
bool GCRuntime::initOrDisableParallelMarking() {
// Attempt to initialize parallel marking state or disable it on failure. This
// is called when parallel marking is enabled or disabled.
MOZ_ASSERT(markers.length() != 0);
if (updateMarkersVector()) {
return true;
}
// Failed to initialize parallel marking so disable it instead.
MOZ_ASSERT(parallelMarkingEnabled);
parallelMarkingEnabled = false;
MOZ_ALWAYS_TRUE(updateMarkersVector());
return false;
}
void GCRuntime::releaseMarkingThreads() {
MOZ_ALWAYS_TRUE(reserveMarkingThreads(0));
}
bool GCRuntime::reserveMarkingThreads(size_t newCount) {
if (reservedMarkingThreads == newCount) {
return true;
}
// Update the helper thread system's global count by subtracting this
// runtime's current contribution |reservedMarkingThreads| and adding the new
// contribution |newCount|.
AutoLockHelperThreadState lock;
auto& globalCount = HelperThreadState().gcParallelMarkingThreads;
MOZ_ASSERT(globalCount >= reservedMarkingThreads);
size_t newGlobalCount = globalCount - reservedMarkingThreads + newCount;
if (newGlobalCount > HelperThreadState().threadCount) {
// Not enough total threads.
return false;
}
globalCount = newGlobalCount;
reservedMarkingThreads = newCount;
return true;
}
size_t GCRuntime::getMaxParallelThreads() const {
AutoLockHelperThreadState lock;
return maxParallelThreads.ref();
}
bool GCRuntime::updateMarkersVector() {
MOZ_ASSERT(helperThreadCount >= 1,
"There must always be at least one mark task");
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
assertNoMarkingWork();
// Limit worker count to number of GC parallel tasks that can run
// concurrently, otherwise one thread can deadlock waiting on another.
size_t targetCount = std::min(markingWorkerCount(), getMaxParallelThreads());
if (rt->isMainRuntime()) {
// For the main runtime, reserve helper threads as long as parallel marking
// is enabled. Worker runtimes may not mark in parallel if there are
// insufficient threads available at the time.
size_t threadsToReserve = targetCount > 1 ? targetCount : 0;
if (!reserveMarkingThreads(threadsToReserve)) {
return false;
}
}
if (markers.length() > targetCount) {
return markers.resize(targetCount);
}
while (markers.length() < targetCount) {
auto marker = MakeUnique<GCMarker>(rt);
if (!marker) {
return false;
}
#ifdef JS_GC_ZEAL
if (maybeMarkStackLimit) {
marker->setMaxCapacity(maybeMarkStackLimit);
}
#endif
if (!marker->init()) {
return false;
}
if (!markers.emplaceBack(std::move(marker))) {
return false;
}
}
return true;
}
template <typename F>
static bool EraseCallback(CallbackVector<F>& vector, F callback) {
for (Callback<F>* p = vector.begin(); p != vector.end(); p++) {
if (p->op == callback) {
vector.erase(p);
return true;
}
}
return false;
}
template <typename F>
static bool EraseCallback(CallbackVector<F>& vector, F callback, void* data) {
for (Callback<F>* p = vector.begin(); p != vector.end(); p++) {
if (p->op == callback && p->data == data) {
vector.erase(p);
return true;
}
}
return false;
}
bool GCRuntime::addBlackRootsTracer(JSTraceDataOp traceOp, void* data) {
AssertHeapIsIdle();
return blackRootTracers.ref().append(Callback<JSTraceDataOp>(traceOp, data));
}
void GCRuntime::removeBlackRootsTracer(JSTraceDataOp traceOp, void* data) {
// Can be called from finalizers
MOZ_ALWAYS_TRUE(EraseCallback(blackRootTracers.ref(), traceOp));
}
void GCRuntime::setGrayRootsTracer(JSGrayRootsTracer traceOp, void* data) {
AssertHeapIsIdle();
grayRootTracer.ref() = {traceOp, data};
}
void GCRuntime::clearBlackAndGrayRootTracers() {
MOZ_ASSERT(rt->isBeingDestroyed());
blackRootTracers.ref().clear();
setGrayRootsTracer(nullptr, nullptr);
}
void GCRuntime::setGCCallback(JSGCCallback callback, void* data) {
gcCallback.ref() = {callback, data};
}
void GCRuntime::callGCCallback(JSGCStatus status, JS::GCReason reason) const {
const auto& callback = gcCallback.ref();
MOZ_ASSERT(callback.op);
callback.op(rt->mainContextFromOwnThread(), status, reason, callback.data);
}
void GCRuntime::setObjectsTenuredCallback(JSObjectsTenuredCallback callback,
void* data) {
tenuredCallback.ref() = {callback, data};
}
void GCRuntime::callObjectsTenuredCallback() {
JS::AutoSuppressGCAnalysis nogc;
const auto& callback = tenuredCallback.ref();
if (callback.op) {
callback.op(rt->mainContextFromOwnThread(), callback.data);
}
}
bool GCRuntime::addFinalizeCallback(JSFinalizeCallback callback, void* data) {
return finalizeCallbacks.ref().append(
Callback<JSFinalizeCallback>(callback, data));
}
void GCRuntime::removeFinalizeCallback(JSFinalizeCallback callback) {
MOZ_ALWAYS_TRUE(EraseCallback(finalizeCallbacks.ref(), callback));
}
void GCRuntime::callFinalizeCallbacks(JS::GCContext* gcx,
JSFinalizeStatus status) const {
for (const auto& p : finalizeCallbacks.ref()) {
p.op(gcx, status, p.data);
}
}
void GCRuntime::setHostCleanupFinalizationRegistryCallback(
JSHostCleanupFinalizationRegistryCallback callback, void* data) {
hostCleanupFinalizationRegistryCallback.ref() = {callback, data};
}
void GCRuntime::callHostCleanupFinalizationRegistryCallback(
JSFunction* doCleanup, GlobalObject* incumbentGlobal) {
JS::AutoSuppressGCAnalysis nogc;
const auto& callback = hostCleanupFinalizationRegistryCallback.ref();
if (callback.op) {
callback.op(doCleanup, incumbentGlobal, callback.data);
}
}
bool GCRuntime::addWeakPointerZonesCallback(JSWeakPointerZonesCallback callback,
void* data) {
return updateWeakPointerZonesCallbacks.ref().append(
Callback<JSWeakPointerZonesCallback>(callback, data));
}
void GCRuntime::removeWeakPointerZonesCallback(
JSWeakPointerZonesCallback callback) {
MOZ_ALWAYS_TRUE(
EraseCallback(updateWeakPointerZonesCallbacks.ref(), callback));
}
void GCRuntime::callWeakPointerZonesCallbacks(JSTracer* trc) const {
for (auto const& p : updateWeakPointerZonesCallbacks.ref()) {
p.op(trc, p.data);
}
}
bool GCRuntime::addWeakPointerCompartmentCallback(
JSWeakPointerCompartmentCallback callback, void* data) {
return updateWeakPointerCompartmentCallbacks.ref().append(
Callback<JSWeakPointerCompartmentCallback>(callback, data));
}
void GCRuntime::removeWeakPointerCompartmentCallback(
JSWeakPointerCompartmentCallback callback) {
MOZ_ALWAYS_TRUE(
EraseCallback(updateWeakPointerCompartmentCallbacks.ref(), callback));
}
void GCRuntime::callWeakPointerCompartmentCallbacks(
JSTracer* trc, JS::Compartment* comp) const {
for (auto const& p : updateWeakPointerCompartmentCallbacks.ref()) {
p.op(trc, comp, p.data);
}
}
JS::GCSliceCallback GCRuntime::setSliceCallback(JS::GCSliceCallback callback) {
return stats().setSliceCallback(callback);
}
bool GCRuntime::addNurseryCollectionCallback(
JS::GCNurseryCollectionCallback callback, void* data) {
return nurseryCollectionCallbacks.ref().append(
Callback<JS::GCNurseryCollectionCallback>(callback, data));
}
void GCRuntime::removeNurseryCollectionCallback(
JS::GCNurseryCollectionCallback callback, void* data) {
MOZ_ALWAYS_TRUE(
EraseCallback(nurseryCollectionCallbacks.ref(), callback, data));
}
void GCRuntime::callNurseryCollectionCallbacks(JS::GCNurseryProgress progress,
JS::GCReason reason) {
for (auto const& p : nurseryCollectionCallbacks.ref()) {
p.op(rt->mainContextFromOwnThread(), progress, reason, p.data);
}
}
JS::DoCycleCollectionCallback GCRuntime::setDoCycleCollectionCallback(
JS::DoCycleCollectionCallback callback) {
const auto prior = gcDoCycleCollectionCallback.ref();
gcDoCycleCollectionCallback.ref() = {callback, nullptr};
return prior.op;
}
void GCRuntime::callDoCycleCollectionCallback(JSContext* cx) {
const auto& callback = gcDoCycleCollectionCallback.ref();
if (callback.op) {
callback.op(cx);
}
}
bool GCRuntime::addRoot(Value* vp, const char* name) {
/*
* Sometimes Firefox will hold weak references to objects and then convert
* them to strong references by calling AddRoot (e.g., via PreserveWrapper,
* or ModifyBusyCount in workers). We need a read barrier to cover these
* cases.
*/
MOZ_ASSERT(vp);
Value value = *vp;
if (value.isGCThing()) {
ValuePreWriteBarrier(value);
}
return rootsHash.ref().put(vp, name);
}
void GCRuntime::removeRoot(Value* vp) {
rootsHash.ref().remove(vp);
notifyRootsRemoved();
}
/* Compacting GC */
bool js::gc::IsCurrentlyAnimating(const TimeStamp& lastAnimationTime,
const TimeStamp& currentTime) {
// Assume that we're currently animating if js::NotifyAnimationActivity has
// been called in the last second.
static const auto oneSecond = TimeDuration::FromSeconds(1);
return !lastAnimationTime.IsNull() &&
currentTime < (lastAnimationTime + oneSecond);
}
static bool DiscardedCodeRecently(Zone* zone, const TimeStamp& currentTime) {
static const auto thirtySeconds = TimeDuration::FromSeconds(30);
return !zone->lastDiscardedCodeTime().IsNull() &&
currentTime < (zone->lastDiscardedCodeTime() + thirtySeconds);
}
bool GCRuntime::shouldCompact() {
// Compact on shrinking GC if enabled. Skip compacting in incremental GCs
// if we are currently animating, unless the user is inactive or we're
// responding to memory pressure.
if (!isShrinkingGC() || !isCompactingGCEnabled()) {
return false;
}
if (initialReason == JS::GCReason::USER_INACTIVE ||
initialReason == JS::GCReason::MEM_PRESSURE) {
return true;
}
return !isIncremental ||
!IsCurrentlyAnimating(rt->lastAnimationTime, TimeStamp::Now());
}
bool GCRuntime::isCompactingGCEnabled() const {
return compactingEnabled &&
rt->mainContextFromOwnThread()->compactingDisabledCount == 0;
}
JS_PUBLIC_API void JS::SetCreateGCSliceBudgetCallback(
JSContext* cx, JS::CreateSliceBudgetCallback cb) {
cx->runtime()->gc.createBudgetCallback = cb;
}
void TimeBudget::setDeadlineFromNow() { deadline = TimeStamp::Now() + budget; }
SliceBudget::SliceBudget(TimeBudget time, InterruptRequestFlag* interrupt)
: counter(StepsPerExpensiveCheck),
interruptRequested(interrupt),
budget(TimeBudget(time)) {
budget.as<TimeBudget>().setDeadlineFromNow();
}
SliceBudget::SliceBudget(WorkBudget work)
: counter(work.budget), interruptRequested(nullptr), budget(work) {}
int SliceBudget::describe(char* buffer, size_t maxlen) const {
if (isUnlimited()) {
return snprintf(buffer, maxlen, "unlimited");
}
if (isWorkBudget()) {
return snprintf(buffer, maxlen, "work(%" PRId64 ")", workBudget());
}
const char* interruptStr = "";
if (interruptRequested) {
interruptStr = interrupted ? "INTERRUPTED " : "interruptible ";
}
const char* extra = "";
if (idle) {
extra = extended ? " (started idle but extended)" : " (idle)";
}
return snprintf(buffer, maxlen, "%s%" PRId64 "ms%s", interruptStr,
timeBudget(), extra);
}
bool SliceBudget::checkOverBudget() {
MOZ_ASSERT(counter <= 0);
MOZ_ASSERT(!isUnlimited());
if (isWorkBudget()) {
return true;
}
if (interruptRequested && *interruptRequested) {
interrupted = true;
}
if (interrupted) {
return true;
}
if (TimeStamp::Now() >= budget.as<TimeBudget>().deadline) {
return true;
}
counter = StepsPerExpensiveCheck;
return false;
}
void GCRuntime::requestMajorGC(JS::GCReason reason) {
MOZ_ASSERT_IF(reason != JS::GCReason::BG_TASK_FINISHED,
!CurrentThreadIsPerformingGC());
if (majorGCRequested()) {
return;
}
majorGCTriggerReason = reason;
rt->mainContextFromAnyThread()->requestInterrupt(InterruptReason::MajorGC);
}
bool GCRuntime::triggerGC(JS::GCReason reason) {
/*
* Don't trigger GCs if this is being called off the main thread from
* onTooMuchMalloc().
*/
if (!CurrentThreadCanAccessRuntime(rt)) {
return false;
}
/* GC is already running. */
if (JS::RuntimeHeapIsCollecting()) {
return false;
}
JS::PrepareForFullGC(rt->mainContextFromOwnThread());
requestMajorGC(reason);
return true;
}
void GCRuntime::maybeTriggerGCAfterAlloc(Zone* zone) {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
MOZ_ASSERT(!JS::RuntimeHeapIsCollecting());
TriggerResult trigger =
checkHeapThreshold(zone, zone->gcHeapSize, zone->gcHeapThreshold);
if (trigger.shouldTrigger) {
// Start or continue an in progress incremental GC. We do this to try to
// avoid performing non-incremental GCs on zones which allocate a lot of
// data, even when incremental slices can't be triggered via scheduling in
// the event loop.
triggerZoneGC(zone, JS::GCReason::ALLOC_TRIGGER, trigger.usedBytes,
trigger.thresholdBytes);
}
}
void js::gc::MaybeMallocTriggerZoneGC(JSRuntime* rt, ZoneAllocator* zoneAlloc,
const HeapSize& heap,
const HeapThreshold& threshold,
JS::GCReason reason) {
rt->gc.maybeTriggerGCAfterMalloc(Zone::from(zoneAlloc), heap, threshold,
reason);
}
void GCRuntime::maybeTriggerGCAfterMalloc(Zone* zone) {
if (maybeTriggerGCAfterMalloc(zone, zone->mallocHeapSize,
zone->mallocHeapThreshold,
JS::GCReason::TOO_MUCH_MALLOC)) {
return;
}
maybeTriggerGCAfterMalloc(zone, zone->jitHeapSize, zone->jitHeapThreshold,
JS::GCReason::TOO_MUCH_JIT_CODE);
}
bool GCRuntime::maybeTriggerGCAfterMalloc(Zone* zone, const HeapSize& heap,
const HeapThreshold& threshold,
JS::GCReason reason) {
// Ignore malloc during sweeping, for example when we resize hash tables.
if (heapState() != JS::HeapState::Idle) {
return false;
}
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
TriggerResult trigger = checkHeapThreshold(zone, heap, threshold);
if (!trigger.shouldTrigger) {
return false;
}
// Trigger a zone GC. budgetIncrementalGC() will work out whether to do an
// incremental or non-incremental collection.
triggerZoneGC(zone, reason, trigger.usedBytes, trigger.thresholdBytes);
return true;
}
TriggerResult GCRuntime::checkHeapThreshold(
Zone* zone, const HeapSize& heapSize, const HeapThreshold& heapThreshold) {
MOZ_ASSERT_IF(heapThreshold.hasSliceThreshold(), zone->wasGCStarted());
size_t usedBytes = heapSize.bytes();
size_t thresholdBytes = heapThreshold.hasSliceThreshold()
? heapThreshold.sliceBytes()
: heapThreshold.startBytes();
// The incremental limit will be checked if we trigger a GC slice.
MOZ_ASSERT(thresholdBytes <= heapThreshold.incrementalLimitBytes());
return TriggerResult{usedBytes >= thresholdBytes, usedBytes, thresholdBytes};
}
bool GCRuntime::triggerZoneGC(Zone* zone, JS::GCReason reason, size_t used,
size_t threshold) {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
/* GC is already running. */
if (JS::RuntimeHeapIsBusy()) {
return false;
}
#ifdef JS_GC_ZEAL
if (hasZealMode(ZealMode::Alloc)) {
MOZ_RELEASE_ASSERT(triggerGC(reason));
return true;
}
#endif
if (zone->isAtomsZone()) {
stats().recordTrigger(used, threshold);
MOZ_RELEASE_ASSERT(triggerGC(reason));
return true;
}
stats().recordTrigger(used, threshold);
zone->scheduleGC();
requestMajorGC(reason);
return true;
}
void GCRuntime::maybeGC() {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
#ifdef JS_GC_ZEAL
if (hasZealMode(ZealMode::Alloc) || hasZealMode(ZealMode::RootsChange)) {
JS::PrepareForFullGC(rt->mainContextFromOwnThread());
gc(JS::GCOptions::Normal, JS::GCReason::DEBUG_GC);
return;
}
#endif
(void)gcIfRequestedImpl(/* eagerOk = */ true);
}
JS::GCReason GCRuntime::wantMajorGC(bool eagerOk) {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
if (majorGCRequested()) {
return majorGCTriggerReason;
}
if (isIncrementalGCInProgress() || !eagerOk) {
return JS::GCReason::NO_REASON;
}
JS::GCReason reason = JS::GCReason::NO_REASON;
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
if (checkEagerAllocTrigger(zone->gcHeapSize, zone->gcHeapThreshold) ||
checkEagerAllocTrigger(zone->mallocHeapSize,
zone->mallocHeapThreshold)) {
zone->scheduleGC();
reason = JS::GCReason::EAGER_ALLOC_TRIGGER;
}
}
return reason;
}
bool GCRuntime::checkEagerAllocTrigger(const HeapSize& size,
const HeapThreshold& threshold) {
size_t thresholdBytes =
threshold.eagerAllocTrigger(schedulingState.inHighFrequencyGCMode());
size_t usedBytes = size.bytes();
if (usedBytes <= 1024 * 1024 || usedBytes < thresholdBytes) {
return false;
}
stats().recordTrigger(usedBytes, thresholdBytes);
return true;
}
bool GCRuntime::shouldDecommit() const {
// If we're doing a shrinking GC we always decommit to release as much memory
// as possible.
if (cleanUpEverything) {
return true;
}
// If we are allocating heavily enough to trigger "high frequency" GC then
// skip decommit so that we do not compete with the mutator.
return !schedulingState.inHighFrequencyGCMode();
}
void GCRuntime::startDecommit() {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::DECOMMIT);
#ifdef DEBUG
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
MOZ_ASSERT(decommitTask.isIdle());
{
AutoLockGC lock(this);
MOZ_ASSERT(fullChunks(lock).verify());
MOZ_ASSERT(availableChunks(lock).verify());
MOZ_ASSERT(emptyChunks(lock).verify());
// Verify that all entries in the empty chunks pool are unused.
for (ChunkPool::Iter chunk(emptyChunks(lock)); !chunk.done();
chunk.next()) {
MOZ_ASSERT(chunk->unused());
}
}
#endif
if (!shouldDecommit()) {
return;
}
{
AutoLockGC lock(this);
if (availableChunks(lock).empty() && !tooManyEmptyChunks(lock) &&
emptyChunks(lock).empty()) {
return; // Nothing to do.
}
}
#ifdef DEBUG
{
AutoLockHelperThreadState lock;
MOZ_ASSERT(!requestSliceAfterBackgroundTask);
}
#endif
if (useBackgroundThreads) {
decommitTask.start();
return;
}
decommitTask.runFromMainThread();
}
BackgroundDecommitTask::BackgroundDecommitTask(GCRuntime* gc)
: GCParallelTask(gc, gcstats::PhaseKind::DECOMMIT) {}
void js::gc::BackgroundDecommitTask::run(AutoLockHelperThreadState& lock) {
{
AutoUnlockHelperThreadState unlock(lock);
ChunkPool emptyChunksToFree;
{
AutoLockGC gcLock(gc);
emptyChunksToFree = gc->expireEmptyChunkPool(gcLock);
}
FreeChunkPool(emptyChunksToFree);
{
AutoLockGC gcLock(gc);
// To help minimize the total number of chunks needed over time, sort the
// available chunks list so that we allocate into more-used chunks first.
gc->availableChunks(gcLock).sort();
if (DecommitEnabled()) {
gc->decommitEmptyChunks(cancel_, gcLock);
gc->decommitFreeArenas(cancel_, gcLock);
}
}
}
gc->maybeRequestGCAfterBackgroundTask(lock);
}
static inline bool CanDecommitWholeChunk(TenuredChunk* chunk) {
return chunk->unused() && chunk->info.numArenasFreeCommitted != 0;
}
// Called from a background thread to decommit free arenas. Releases the GC
// lock.
void GCRuntime::decommitEmptyChunks(const bool& cancel, AutoLockGC& lock) {
Vector<TenuredChunk*, 0, SystemAllocPolicy> chunksToDecommit;
for (ChunkPool::Iter chunk(emptyChunks(lock)); !chunk.done(); chunk.next()) {
if (CanDecommitWholeChunk(chunk) && !chunksToDecommit.append(chunk)) {
onOutOfMallocMemory(lock);
return;
}
}
for (TenuredChunk* chunk : chunksToDecommit) {
if (cancel) {
break;
}
// Check whether something used the chunk while lock was released.
if (!CanDecommitWholeChunk(chunk)) {
continue;
}
// Temporarily remove the chunk while decommitting its memory so that the
// mutator doesn't start allocating from it when we drop the lock.
emptyChunks(lock).remove(chunk);
{
AutoUnlockGC unlock(lock);
chunk->decommitAllArenas();
MOZ_ASSERT(chunk->info.numArenasFreeCommitted == 0);
}
emptyChunks(lock).push(chunk);
}
}
// Called from a background thread to decommit free arenas. Releases the GC
// lock.
void GCRuntime::decommitFreeArenas(const bool& cancel, AutoLockGC& lock) {
MOZ_ASSERT(DecommitEnabled());
// Since we release the GC lock while doing the decommit syscall below,
// it is dangerous to iterate the available list directly, as the active
// thread could modify it concurrently. Instead, we build and pass an
// explicit Vector containing the Chunks we want to visit.
Vector<TenuredChunk*, 0, SystemAllocPolicy> chunksToDecommit;
for (ChunkPool::Iter chunk(availableChunks(lock)); !chunk.done();
chunk.next()) {
if (chunk->info.numArenasFreeCommitted != 0 &&
!chunksToDecommit.append(chunk)) {
onOutOfMallocMemory(lock);
return;
}
}
for (TenuredChunk* chunk : chunksToDecommit) {
chunk->decommitFreeArenas(this, cancel, lock);
}
}
// Do all possible decommit immediately from the current thread without
// releasing the GC lock or allocating any memory.
void GCRuntime::decommitFreeArenasWithoutUnlocking(const AutoLockGC& lock) {
MOZ_ASSERT(DecommitEnabled());
for (ChunkPool::Iter chunk(availableChunks(lock)); !chunk.done();
chunk.next()) {
chunk->decommitFreeArenasWithoutUnlocking(lock);
}
MOZ_ASSERT(availableChunks(lock).verify());
}
void GCRuntime::maybeRequestGCAfterBackgroundTask(
const AutoLockHelperThreadState& lock) {
if (requestSliceAfterBackgroundTask) {
// Trigger a slice so the main thread can continue the collection
// immediately.
requestSliceAfterBackgroundTask = false;
requestMajorGC(JS::GCReason::BG_TASK_FINISHED);
}
}
void GCRuntime::cancelRequestedGCAfterBackgroundTask() {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
#ifdef DEBUG
{
AutoLockHelperThreadState lock;
MOZ_ASSERT(!requestSliceAfterBackgroundTask);
}
#endif
majorGCTriggerReason.compareExchange(JS::GCReason::BG_TASK_FINISHED,
JS::GCReason::NO_REASON);
}
bool GCRuntime::isWaitingOnBackgroundTask() const {
AutoLockHelperThreadState lock;
return requestSliceAfterBackgroundTask;
}
void GCRuntime::queueUnusedLifoBlocksForFree(LifoAlloc* lifo) {
MOZ_ASSERT(JS::RuntimeHeapIsBusy());
AutoLockHelperThreadState lock;
lifoBlocksToFree.ref().transferUnusedFrom(lifo);
}
void GCRuntime::queueAllLifoBlocksForFreeAfterMinorGC(LifoAlloc* lifo) {
lifoBlocksToFreeAfterFullMinorGC.ref().transferFrom(lifo);
}
void GCRuntime::queueBuffersForFreeAfterMinorGC(Nursery::BufferSet& buffers) {
AutoLockHelperThreadState lock;
if (!buffersToFreeAfterMinorGC.ref().empty()) {
// In the rare case that this hasn't processed the buffers from a previous
// minor GC we have to wait here.
MOZ_ASSERT(!freeTask.isIdle(lock));
freeTask.joinWithLockHeld(lock);
}
MOZ_ASSERT(buffersToFreeAfterMinorGC.ref().empty());
std::swap(buffersToFreeAfterMinorGC.ref(), buffers);
}
void Realm::destroy(JS::GCContext* gcx) {
JSRuntime* rt = gcx->runtime();
if (auto callback = rt->destroyRealmCallback) {
callback(gcx, this);
}
if (principals()) {
JS_DropPrincipals(rt->mainContextFromOwnThread(), principals());
}
// GC thing is not currently tracked.
gcx->deleteUntracked(this);
}
void Compartment::destroy(JS::GCContext* gcx) {
JSRuntime* rt = gcx->runtime();
if (auto callback = rt->destroyCompartmentCallback) {
callback(gcx, this);
}
// GC thing is not currently tracked.
gcx->deleteUntracked(this);
rt->gc.stats().sweptCompartment();
}
void Zone::destroy(JS::GCContext* gcx) {
MOZ_ASSERT(compartments().empty());
JSRuntime* rt = gcx->runtime();
if (auto callback = rt->destroyZoneCallback) {
callback(gcx, this);
}
// GC thing is not currently tracked.
gcx->deleteUntracked(this);
gcx->runtime()->gc.stats().sweptZone();
}
/*
* It's simpler if we preserve the invariant that every zone (except atoms
* zones) has at least one compartment, and every compartment has at least one
* realm. If we know we're deleting the entire zone, then sweepCompartments is
* allowed to delete all compartments. In this case, |keepAtleastOne| is false.
* If any cells remain alive in the zone, set |keepAtleastOne| true to prohibit
* sweepCompartments from deleting every compartment. Instead, it preserves an
* arbitrary compartment in the zone.
*/
void Zone::sweepCompartments(JS::GCContext* gcx, bool keepAtleastOne,
bool destroyingRuntime) {
MOZ_ASSERT_IF(!isAtomsZone(), !compartments().empty());
MOZ_ASSERT_IF(destroyingRuntime, !keepAtleastOne);
Compartment** read = compartments().begin();
Compartment** end = compartments().end();
Compartment** write = read;
while (read < end) {
Compartment* comp = *read++;
/*
* Don't delete the last compartment and realm if keepAtleastOne is
* still true, meaning all the other compartments were deleted.
*/
bool keepAtleastOneRealm = read == end && keepAtleastOne;
comp->sweepRealms(gcx, keepAtleastOneRealm, destroyingRuntime);
if (!comp->realms().empty()) {
*write++ = comp;
keepAtleastOne = false;
} else {
comp->destroy(gcx);
}
}
compartments().shrinkTo(write - compartments().begin());
MOZ_ASSERT_IF(keepAtleastOne, !compartments().empty());
MOZ_ASSERT_IF(destroyingRuntime, compartments().empty());
}
void Compartment::sweepRealms(JS::GCContext* gcx, bool keepAtleastOne,
bool destroyingRuntime) {
MOZ_ASSERT(!realms().empty());
MOZ_ASSERT_IF(destroyingRuntime, !keepAtleastOne);
Realm** read = realms().begin();
Realm** end = realms().end();
Realm** write = read;
while (read < end) {
Realm* realm = *read++;
/*
* Don't delete the last realm if keepAtleastOne is still true, meaning
* all the other realms were deleted.
*/
bool dontDelete = read == end && keepAtleastOne;
if ((realm->marked() || dontDelete) && !destroyingRuntime) {
*write++ = realm;
keepAtleastOne = false;
} else {
realm->destroy(gcx);
}
}
realms().shrinkTo(write - realms().begin());
MOZ_ASSERT_IF(keepAtleastOne, !realms().empty());
MOZ_ASSERT_IF(destroyingRuntime, realms().empty());
}
void GCRuntime::sweepZones(JS::GCContext* gcx, bool destroyingRuntime) {
MOZ_ASSERT_IF(destroyingRuntime, numActiveZoneIters == 0);
MOZ_ASSERT(foregroundFinalizedArenas.ref().isNothing());
if (numActiveZoneIters) {
return;
}
assertBackgroundSweepingFinished();
// Sweep zones following the atoms zone.
MOZ_ASSERT(zones()[0]->isAtomsZone());
Zone** read = zones().begin() + 1;
Zone** end = zones().end();
Zone** write = read;
while (read < end) {
Zone* zone = *read++;
if (zone->wasGCStarted()) {
MOZ_ASSERT(!zone->isQueuedForBackgroundSweep());
AutoSetThreadIsSweeping threadIsSweeping(zone);
const bool zoneIsDead =
zone->arenas.arenaListsAreEmpty() && !zone->hasMarkedRealms();
MOZ_ASSERT_IF(destroyingRuntime, zoneIsDead);
if (zoneIsDead) {
zone->arenas.checkEmptyFreeLists();
zone->sweepCompartments(gcx, false, destroyingRuntime);
MOZ_ASSERT(zone->compartments().empty());
zone->destroy(gcx);
continue;
}
zone->sweepCompartments(gcx, true, destroyingRuntime);
}
*write++ = zone;
}
zones().shrinkTo(write - zones().begin());
}
void ArenaLists::checkEmptyArenaList(AllocKind kind) {
MOZ_ASSERT(arenaList(kind).isEmpty());
}
void GCRuntime::purgeRuntimeForMinorGC() {
for (ZonesIter zone(this, SkipAtoms); !zone.done(); zone.next()) {
zone->externalStringCache().purge();
zone->functionToStringCache().purge();
}
}
void GCRuntime::purgeRuntime() {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::PURGE);
for (GCRealmsIter realm(rt); !realm.done(); realm.next()) {
realm->purge();
}
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
zone->purgeAtomCache();
zone->externalStringCache().purge();
zone->functionToStringCache().purge();
zone->boundPrefixCache().clearAndCompact();
zone->shapeZone().purgeShapeCaches(rt->gcContext());
}
JSContext* cx = rt->mainContextFromOwnThread();
queueUnusedLifoBlocksForFree(&cx->tempLifoAlloc());
cx->interpreterStack().purge(rt);
cx->frontendCollectionPool().purge();
rt->caches().purge();
if (rt->isMainRuntime()) {
SharedImmutableStringsCache::getSingleton().purge();
}
MOZ_ASSERT(marker().unmarkGrayStack.empty());
marker().unmarkGrayStack.clearAndFree();
}
bool GCRuntime::shouldPreserveJITCode(Realm* realm,
const TimeStamp& currentTime,
JS::GCReason reason,
bool canAllocateMoreCode,
bool isActiveCompartment) {
if (cleanUpEverything) {
return false;
}
if (!canAllocateMoreCode) {
return false;
}
if (isActiveCompartment) {
return true;
}
if (alwaysPreserveCode) {
return true;
}
if (realm->preserveJitCode()) {
return true;
}
if (IsCurrentlyAnimating(realm->lastAnimationTime, currentTime) &&
DiscardedCodeRecently(realm->zone(), currentTime)) {
return true;
}
if (reason == JS::GCReason::DEBUG_GC) {
return true;
}
return false;
}
#ifdef DEBUG
class CompartmentCheckTracer final : public JS::CallbackTracer {
void onChild(JS::GCCellPtr thing, const char* name) override;
bool edgeIsInCrossCompartmentMap(JS::GCCellPtr dst);
public:
explicit CompartmentCheckTracer(JSRuntime* rt)
: JS::CallbackTracer(rt, JS::TracerKind::CompartmentCheck,
JS::WeakEdgeTraceAction::Skip) {}
Cell* src = nullptr;
JS::TraceKind srcKind = JS::TraceKind::Null;
Zone* zone = nullptr;
Compartment* compartment = nullptr;
};
static bool InCrossCompartmentMap(JSRuntime* rt, JSObject* src,
JS::GCCellPtr dst) {
// Cross compartment edges are either in the cross compartment map or in a
// debugger weakmap.
Compartment* srccomp = src->compartment();
if (dst.is<JSObject>()) {
if (ObjectWrapperMap::Ptr p = srccomp->lookupWrapper(&dst.as<JSObject>())) {
if (*p->value().unsafeGet() == src) {
return true;
}
}
}
if (DebugAPI::edgeIsInDebuggerWeakmap(rt, src, dst)) {
return true;
}
return false;
}
void CompartmentCheckTracer::onChild(JS::GCCellPtr thing, const char* name) {
Compartment* comp =
MapGCThingTyped(thing, [](auto t) { return t->maybeCompartment(); });
if (comp && compartment) {
MOZ_ASSERT(comp == compartment || edgeIsInCrossCompartmentMap(thing));
} else {
TenuredCell* tenured = &thing.asCell()->asTenured();
Zone* thingZone = tenured->zoneFromAnyThread();
MOZ_ASSERT(thingZone == zone || thingZone->isAtomsZone());
}
}
bool CompartmentCheckTracer::edgeIsInCrossCompartmentMap(JS::GCCellPtr dst) {
return srcKind == JS::TraceKind::Object &&
InCrossCompartmentMap(runtime(), static_cast<JSObject*>(src), dst);
}
void GCRuntime::checkForCompartmentMismatches() {
JSContext* cx = rt->mainContextFromOwnThread();
if (cx->disableStrictProxyCheckingCount) {
return;
}
CompartmentCheckTracer trc(rt);
AutoAssertEmptyNursery empty(cx);
for (ZonesIter zone(this, SkipAtoms); !zone.done(); zone.next()) {
trc.zone = zone;
for (auto thingKind : AllAllocKinds()) {
for (auto i = zone->cellIterUnsafe<TenuredCell>(thingKind, empty);
!i.done(); i.next()) {
trc.src = i.getCell();
trc.srcKind = MapAllocToTraceKind(thingKind);
trc.compartment = MapGCThingTyped(
trc.src, trc.srcKind, [](auto t) { return t->maybeCompartment(); });
JS::TraceChildren(&trc, JS::GCCellPtr(trc.src, trc.srcKind));
}
}
}
}
#endif
static bool ShouldCleanUpEverything(JS::GCOptions options) {
// During shutdown, we must clean everything up, for the sake of leak
// detection. When a runtime has no contexts, or we're doing a GC before a
// shutdown CC, those are strong indications that we're shutting down.
return options == JS::GCOptions::Shutdown || options == JS::GCOptions::Shrink;
}
static bool ShouldUseBackgroundThreads(bool isIncremental,
JS::GCReason reason) {
bool shouldUse = isIncremental && CanUseExtraThreads();
MOZ_ASSERT_IF(reason == JS::GCReason::DESTROY_RUNTIME, !shouldUse);
return shouldUse;
}
void GCRuntime::startCollection(JS::GCReason reason) {
checkGCStateNotInUse();
MOZ_ASSERT_IF(
isShuttingDown(),
isShutdownGC() ||
initialReason = reason;
cleanUpEverything = ShouldCleanUpEverything(gcOptions());
isCompacting = shouldCompact();
rootsRemoved = false;
sweepGroupIndex = 0;
lastGCStartTime_ = TimeStamp::Now();
#ifdef DEBUG
if (isShutdownGC()) {
hadShutdownGC = true;
}
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
zone->gcSweepGroupIndex = 0;
}
#endif
}
static void RelazifyFunctions(Zone* zone, AllocKind kind) {
MOZ_ASSERT(kind == AllocKind::FUNCTION ||
kind == AllocKind::FUNCTION_EXTENDED);
JSRuntime* rt = zone->runtimeFromMainThread();
AutoAssertEmptyNursery empty(rt->mainContextFromOwnThread());
for (auto i = zone->cellIterUnsafe<JSObject>(kind, empty); !i.done();
i.next()) {
JSFunction* fun = &i->as<JSFunction>();
// When iterating over the GC-heap, we may encounter function objects that
// are incomplete (missing a BaseScript when we expect one). We must check
// for this case before we can call JSFunction::hasBytecode().
if (fun->isIncomplete()) {
continue;
}
if (fun->hasBytecode()) {
fun->maybeRelazify(rt);
}
}
}
static bool ShouldCollectZone(Zone* zone, JS::GCReason reason) {
// If we are repeating a GC because we noticed dead compartments haven't
// been collected, then only collect zones containing those compartments.
if (reason == JS::GCReason::COMPARTMENT_REVIVED) {
for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) {
if (comp->gcState.scheduledForDestruction) {
return true;
}
}
return false;
}
// Otherwise we only collect scheduled zones.
return zone->isGCScheduled();
}
bool GCRuntime::prepareZonesForCollection(JS::GCReason reason,
bool* isFullOut) {
#ifdef DEBUG
/* Assert that zone state is as we expect */
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
MOZ_ASSERT(!zone->isCollecting());
MOZ_ASSERT_IF(!zone->isAtomsZone(), !zone->compartments().empty());
for (auto i : AllAllocKinds()) {
MOZ_ASSERT(zone->arenas.collectingArenaList(i).isEmpty());
}
}
#endif
*isFullOut = true;
bool any = false;
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
/* Set up which zones will be collected. */
bool shouldCollect = ShouldCollectZone(zone, reason);
if (shouldCollect) {
any = true;
zone->changeGCState(Zone::NoGC, Zone::Prepare);
} else {
*isFullOut = false;
}
zone->setWasCollected(shouldCollect);
}
/* Check that at least one zone is scheduled for collection. */
return any;
}
void GCRuntime::discardJITCodeForGC() {
size_t nurserySiteResetCount = 0;
size_t pretenuredSiteResetCount = 0;
js::CancelOffThreadIonCompile(rt, JS::Zone::Prepare);
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK_DISCARD_CODE);
// We may need to reset allocation sites and discard JIT code to recover if
// we find object lifetimes have changed.
PretenuringZone& pz = zone->pretenuring;
bool resetNurserySites = pz.shouldResetNurseryAllocSites();
bool resetPretenuredSites = pz.shouldResetPretenuredAllocSites();
if (!zone->isPreservingCode()) {
Zone::DiscardOptions options;
options.discardJitScripts = true;
options.resetNurseryAllocSites = resetNurserySites;
options.resetPretenuredAllocSites = resetPretenuredSites;
zone->discardJitCode(rt->gcContext(), options);
} else if (resetNurserySites || resetPretenuredSites) {
zone->resetAllocSitesAndInvalidate(resetNurserySites,
resetPretenuredSites);
}
if (resetNurserySites) {
nurserySiteResetCount++;
}
if (resetPretenuredSites) {
pretenuredSiteResetCount++;
}
}
if (nursery().reportPretenuring()) {
if (nurserySiteResetCount) {
fprintf(
stderr,
"GC reset nursery alloc sites and invalidated code in %zu zones\n",
nurserySiteResetCount);
}
if (pretenuredSiteResetCount) {
fprintf(
stderr,
"GC reset pretenured alloc sites and invalidated code in %zu zones\n",
pretenuredSiteResetCount);
}
}
}
void GCRuntime::relazifyFunctionsForShrinkingGC() {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::RELAZIFY_FUNCTIONS);
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
RelazifyFunctions(zone, AllocKind::FUNCTION);
RelazifyFunctions(zone, AllocKind::FUNCTION_EXTENDED);
}
}
void GCRuntime::purgePropMapTablesForShrinkingGC() {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::PURGE_PROP_MAP_TABLES);
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
if (!canRelocateZone(zone) || zone->keepPropMapTables()) {
continue;
}
// Note: CompactPropMaps never have a table.
for (auto map = zone->cellIterUnsafe<NormalPropMap>(); !map.done();
map.next()) {
if (map->asLinked()->hasTable()) {
map->asLinked()->purgeTable(rt->gcContext());
}
}
for (auto map = zone->cellIterUnsafe<DictionaryPropMap>(); !map.done();
map.next()) {
if (map->asLinked()->hasTable()) {
map->asLinked()->purgeTable(rt->gcContext());
}
}
}
}
// The debugger keeps track of the URLs for the sources of each realm's scripts.
// These URLs are purged on shrinking GCs.
void GCRuntime::purgeSourceURLsForShrinkingGC() {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::PURGE_SOURCE_URLS);
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
// URLs are not tracked for realms in the system zone.
if (!canRelocateZone(zone) || zone->isSystemZone()) {
continue;
}
for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) {
for (RealmsInCompartmentIter realm(comp); !realm.done(); realm.next()) {
GlobalObject* global = realm.get()->unsafeUnbarrieredMaybeGlobal();
if (global) {
global->clearSourceURLSHolder();
}
}
}
}
}
void GCRuntime::unmarkWeakMaps() {
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
/* Unmark all weak maps in the zones being collected. */
WeakMapBase::unmarkZone(zone);
}
}
bool GCRuntime::beginPreparePhase(JS::GCReason reason, AutoGCSession& session) {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::PREPARE);
if (!prepareZonesForCollection(reason, &isFull.ref())) {
return false;
}
/*
* Start a parallel task to clear all mark state for the zones we are
* collecting. This is linear in the size of the heap we are collecting and so
* can be slow. This usually happens concurrently with the mutator and GC
* proper does not start until this is complete.
*/
unmarkTask.initZones();
if (useBackgroundThreads) {
unmarkTask.start();
} else {
unmarkTask.runFromMainThread();
}
/*
* Process any queued source compressions during the start of a major
* GC.
*
* GCReason::XPCONNECT_SHUTDOWN GCs we can remove the extra check.
*/
if (!isShutdownGC() && reason != JS::GCReason::XPCONNECT_SHUTDOWN) {
StartHandlingCompressionsOnGC(rt);
}
return true;
}
BackgroundUnmarkTask::BackgroundUnmarkTask(GCRuntime* gc)
: GCParallelTask(gc, gcstats::PhaseKind::UNMARK) {}
void BackgroundUnmarkTask::initZones() {
MOZ_ASSERT(isIdle());
MOZ_ASSERT(zones.empty());
MOZ_ASSERT(!isCancelled());
// We can't safely iterate the zones vector from another thread so we copy the
// zones to be collected into another vector.
AutoEnterOOMUnsafeRegion oomUnsafe;
for (GCZonesIter zone(gc); !zone.done(); zone.next()) {
if (!zones.append(zone.get())) {
oomUnsafe.crash("BackgroundUnmarkTask::initZones");
}
zone->arenas.clearFreeLists();
zone->arenas.moveArenasToCollectingLists();
}
}
void BackgroundUnmarkTask::run(AutoLockHelperThreadState& helperTheadLock) {
AutoUnlockHelperThreadState unlock(helperTheadLock);
for (Zone* zone : zones) {
for (auto kind : AllAllocKinds()) {
ArenaList& arenas = zone->arenas.collectingArenaList(kind);
for (ArenaListIter arena(arenas.head()); !arena.done(); arena.next()) {
arena->unmarkAll();
if (isCancelled()) {
break;
}
}
}
}
zones.clear();
}
void GCRuntime::endPreparePhase(JS::GCReason reason) {
MOZ_ASSERT(unmarkTask.isIdle());
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
zone->setPreservingCode(false);
}
// Discard JIT code more aggressively if the process is approaching its
// executable code limit.
bool canAllocateMoreCode = jit::CanLikelyAllocateMoreExecutableMemory();
auto currentTime = TimeStamp::Now();
Compartment* activeCompartment = nullptr;
jit::JitActivationIterator activation(rt->mainContextFromOwnThread());
if (!activation.done()) {
activeCompartment = activation->compartment();
}
for (CompartmentsIter c(rt); !c.done(); c.next()) {
c->gcState.scheduledForDestruction = false;
c->gcState.maybeAlive = false;
c->gcState.hasEnteredRealm = false;
if (c->invisibleToDebugger()) {
c->gcState.maybeAlive = true; // Presumed to be a system compartment.
}
bool isActiveCompartment = c == activeCompartment;
for (RealmsInCompartmentIter r(c); !r.done(); r.next()) {
if (r->shouldTraceGlobal() || !r->zone()->isGCScheduled()) {
c->gcState.maybeAlive = true;
}
if (shouldPreserveJITCode(r, currentTime, reason, canAllocateMoreCode,
isActiveCompartment)) {
r->zone()->setPreservingCode(true);
}
if (r->hasBeenEnteredIgnoringJit()) {
c->gcState.hasEnteredRealm = true;
}
}
}
/*
* Perform remaining preparation work that must take place in the first true
* GC slice.
*/
{
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::PREPARE);
AutoLockHelperThreadState helperLock;
/* Clear mark state for WeakMaps in parallel with other work. */
AutoRunParallelTask unmarkWeakMaps(this, &GCRuntime::unmarkWeakMaps,
gcstats::PhaseKind::UNMARK_WEAKMAPS,
GCUse::Unspecified, helperLock);
AutoUnlockHelperThreadState unlock(helperLock);
// Discard JIT code. For incremental collections, the sweep phase may
// also discard JIT code.
discardJITCodeForGC();
haveDiscardedJITCodeThisSlice = true;
/*
* We must purge the runtime at the beginning of an incremental GC. The
* danger if we purge later is that the snapshot invariant of
* incremental GC will be broken, as follows. If some object is
* reachable only through some cache (say the dtoaCache) then it will
* not be part of the snapshot. If we purge after root marking, then
* the mutator could obtain a pointer to the object and start using
* it. This object might never be marked, so a GC hazard would exist.
*/
purgeRuntime();
}
// This will start background free for lifo blocks queued by purgeRuntime,
// even if there's nothing in the nursery.
collectNurseryFromMajorGC(reason);
{
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::PREPARE);
// Relazify functions after discarding JIT code (we can't relazify functions
// with JIT code) and before the actual mark phase, so that the current GC
// can collect the JSScripts we're unlinking here. We do this only when
// we're performing a shrinking GC, as too much relazification can cause
// performance issues when we have to reparse the same functions over and
// over.
if (isShrinkingGC()) {
relazifyFunctionsForShrinkingGC();
purgePropMapTablesForShrinkingGC();
purgeSourceURLsForShrinkingGC();
}
if (isShutdownGC()) {
/* Clear any engine roots that may hold external data live. */
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
zone->clearRootsForShutdownGC();
}
#ifdef DEBUG
testMarkQueue.clear();
queuePos = 0;
#endif
}
}
#ifdef DEBUG
if (fullCompartmentChecks) {
checkForCompartmentMismatches();
}
#endif
}
AutoUpdateLiveCompartments::AutoUpdateLiveCompartments(GCRuntime* gc) : gc(gc) {
for (GCCompartmentsIter c(gc->rt); !c.done(); c.next()) {
c->gcState.hasMarkedCells = false;
}
}
AutoUpdateLiveCompartments::~AutoUpdateLiveCompartments() {
for (GCCompartmentsIter c(gc->rt); !c.done(); c.next()) {
if (c->gcState.hasMarkedCells) {
c->gcState.maybeAlive = true;
}
}
}
Zone::GCState Zone::initialMarkingState() const {
if (isAtomsZone()) {
// Don't delay gray marking in the atoms zone like we do in other zones.
return MarkBlackAndGray;
}
return MarkBlackOnly;
}
void GCRuntime::beginMarkPhase(AutoGCSession& session) {
/*
* Mark phase.
*/
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK);
// This is the slice we actually start collecting. The number can be used to
// check whether a major GC has started so we must not increment it until we
// get here.
incMajorGcNumber();
#ifdef DEBUG
queuePos = 0;
queueMarkColor.reset();
#endif
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
// In an incremental GC, clear the arena free lists to ensure that
// subsequent allocations refill them and end up marking new cells black.
// See arenaAllocatedDuringGC().
zone->arenas.clearFreeLists();
#ifdef JS_GC_ZEAL
if (hasZealMode(ZealMode::YieldBeforeRootMarking)) {
for (auto kind : AllAllocKinds()) {
for (ArenaIter arena(zone, kind); !arena.done(); arena.next()) {
arena->checkNoMarkedCells();
}
}
}
#endif
// Incremental marking barriers are enabled at this point.
zone->changeGCState(Zone::Prepare, zone->initialMarkingState());
// Merge arenas allocated during the prepare phase, then move all arenas to
// the collecting arena lists.
zone->arenas.mergeArenasFromCollectingLists();
zone->arenas.moveArenasToCollectingLists();
for (RealmsInZoneIter realm(zone); !realm.done(); realm.next()) {
realm->clearAllocatedDuringGC();
}
}
updateSchedulingStateOnGCStart();
stats().measureInitialHeapSize();
useParallelMarking = SingleThreadedMarking;
if (canMarkInParallel() && initParallelMarking()) {
useParallelMarking = AllowParallelMarking;
}
MOZ_ASSERT(!hasDelayedMarking());
for (auto& marker : markers) {
marker->start();
}
if (rt->isBeingDestroyed()) {
checkNoRuntimeRoots(session);
} else {
AutoUpdateLiveCompartments updateLive(this);
marker().setRootMarkingMode(true);
traceRuntimeForMajorGC(marker().tracer(), session);
marker().setRootMarkingMode(false);
}
}
void GCRuntime::findDeadCompartments() {
gcstats::AutoPhase ap1(stats(), gcstats::PhaseKind::FIND_DEAD_COMPARTMENTS);
/*
* This code ensures that if a compartment is "dead", then it will be
* collected in this GC. A compartment is considered dead if its maybeAlive
* flag is false. The maybeAlive flag is set if:
*
* (1) the compartment has been entered (set in beginMarkPhase() above)
* (2) the compartment's zone is not being collected (set in
* endPreparePhase() above)
* (3) an object in the compartment was marked during root marking, either
* as a black root or a gray root. This is arranged by
* SetCompartmentHasMarkedCells and AutoUpdateLiveCompartments.
* (4) the compartment has incoming cross-compartment edges from another
* compartment that has maybeAlive set (set by this method).
* (5) the compartment has the invisibleToDebugger flag set, as it is
* presumed to be a system compartment (set in endPreparePhase() above)
*
* If the maybeAlive is false, then we set the scheduledForDestruction flag.
* At the end of the GC, we look for compartments where
* scheduledForDestruction is true. These are compartments that were somehow
* "revived" during the incremental GC. If any are found, we do a special,
* non-incremental GC of those compartments to try to collect them.
*
* Compartments can be revived for a variety of reasons, including:
*
* (1) A dead reflector can be revived by DOM code that still refers to the
* (2) JS_TransplantObject iterates over all compartments, live or dead, and
* operates on their objects. This can trigger read barriers and mark
* avoid the problem, we try to avoid allocation and read barriers
* during JS_TransplantObject and the like.
* (3) Read barriers. A compartment may only have weak roots and reading one
* of these will cause the compartment to stay alive even though the GC
* thought it should die. An example of this is Gecko's unprivileged
* junk scope, which is handled by ignoring system compartments (see bug
* 1868437).
*/
// Propagate the maybeAlive flag via cross-compartment edges.
Vector<Compartment*, 0, js::SystemAllocPolicy> workList;
for (CompartmentsIter comp(rt); !comp.done(); comp.next()) {
if (comp->gcState.maybeAlive) {
if (!workList.append(comp)) {
return;
}
}
}
while (!workList.empty()) {
Compartment* comp = workList.popCopy();
for (Compartment::WrappedObjectCompartmentEnum e(comp); !e.empty();
e.popFront()) {
Compartment* dest = e.front();
if (!dest->gcState.maybeAlive) {
dest->gcState.maybeAlive = true;
if (!workList.append(dest)) {
return;
}
}
}
}
// Set scheduledForDestruction based on maybeAlive.
for (GCCompartmentsIter comp(rt); !comp.done(); comp.next()) {
MOZ_ASSERT(!comp->gcState.scheduledForDestruction);
if (!comp->gcState.maybeAlive) {
comp->gcState.scheduledForDestruction = true;
}
}
}
void GCRuntime::updateSchedulingStateOnGCStart() {
heapSize.updateOnGCStart();
// Update memory counters for the zones we are collecting.
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
zone->updateSchedulingStateOnGCStart();
}
}
inline bool GCRuntime::canMarkInParallel() const {
MOZ_ASSERT(state() >= gc::State::MarkRoots);
#if defined(DEBUG) || defined(JS_OOM_BREAKPOINT)
// OOM testing limits the engine to using a single helper thread.
if (oom::simulator.targetThread() == THREAD_TYPE_GCPARALLEL) {
return false;
}
#endif
return markers.length() > 1 && stats().initialCollectedBytes() >=
tunables.parallelMarkingThresholdBytes();
}
bool GCRuntime::initParallelMarking() {
// This is called at the start of collection.
MOZ_ASSERT(canMarkInParallel());
// Reserve/release helper threads for worker runtimes. These are released at
// the end of sweeping. If there are not enough helper threads because
// other runtimes are marking in parallel then parallel marking will not be
// used.
if (!rt->isMainRuntime() && !reserveMarkingThreads(markers.length())) {
return false;
}
// Allocate stack for parallel markers. The first marker always has stack
// allocated. Other markers have their stack freed in
// GCRuntime::finishCollection.
for (size_t i = 1; i < markers.length(); i++) {
if (!markers[i]->initStack()) {
return false;
}
}
return true;
}
IncrementalProgress GCRuntime::markUntilBudgetExhausted(
SliceBudget& sliceBudget, ParallelMarking allowParallelMarking,
ShouldReportMarkTime reportTime) {
// Run a marking slice and return whether the stack is now empty.
AutoMajorGCProfilerEntry s(this);
if (initialState != State::Mark) {
sliceBudget.forceCheck();
if (sliceBudget.isOverBudget()) {
return NotFinished;
}
}
if (processTestMarkQueue() == QueueYielded) {
return NotFinished;
}
if (allowParallelMarking) {
MOZ_ASSERT(canMarkInParallel());
MOZ_ASSERT(parallelMarkingEnabled);
MOZ_ASSERT(reportTime);
MOZ_ASSERT(!isBackgroundMarking());
ParallelMarker pm(this);
if (!pm.mark(sliceBudget)) {
return NotFinished;
}
assertNoMarkingWork();
return Finished;
}
#ifdef DEBUG
AutoSetThreadIsMarking threadIsMarking;
#endif // DEBUG
return marker().markUntilBudgetExhausted(sliceBudget, reportTime)
? Finished
: NotFinished;
}
void GCRuntime::drainMarkStack() {
auto unlimited = SliceBudget::unlimited();
MOZ_RELEASE_ASSERT(marker().markUntilBudgetExhausted(unlimited));
}
#ifdef DEBUG
const GCVector<HeapPtr<JS::Value>, 0, SystemAllocPolicy>&
GCRuntime::getTestMarkQueue() const {
return testMarkQueue.get();
}
bool GCRuntime::appendTestMarkQueue(const JS::Value& value) {
return testMarkQueue.append(value);
}
void GCRuntime::clearTestMarkQueue() {
testMarkQueue.clear();
queuePos = 0;
}
size_t GCRuntime::testMarkQueuePos() const { return queuePos; }
#endif
GCRuntime::MarkQueueProgress GCRuntime::processTestMarkQueue() {
#ifdef DEBUG
if (testMarkQueue.empty()) {
return QueueComplete;
}
if (queueMarkColor == mozilla::Some(MarkColor::Gray) &&
state() != State::Sweep) {
return QueueSuspended;
}
// If the queue wants to be gray marking, but we've pushed a black object
// since set-color-gray was processed, then we can't switch to gray and must
// again wait until gray marking is possible.
//
// Remove this code if the restriction against marking gray during black is
// relaxed.
if (queueMarkColor == mozilla::Some(MarkColor::Gray) &&
marker().hasBlackEntries()) {
return QueueSuspended;
}
// If the queue wants to be marking a particular color, switch to that color.
// In any case, restore the mark color to whatever it was when we entered
// this function.
bool willRevertToGray = marker().markColor() == MarkColor::Gray;
AutoSetMarkColor autoRevertColor(
marker(), queueMarkColor.valueOr(marker().markColor()));
// Process the mark queue by taking each object in turn, pushing it onto the
// mark stack, and processing just the top element with processMarkStackTop
// without recursing into reachable objects.
while (queuePos < testMarkQueue.length()) {
Value val = testMarkQueue[queuePos++].get();
if (val.isObject()) {
JSObject* obj = &val.toObject();
JS::Zone* zone = obj->zone();
if (!zone->isGCMarking() || obj->isMarkedAtLeast(marker().markColor())) {
continue;
}
// If we have started sweeping, obey sweep group ordering. But note that
// we will first be called during the initial sweep slice, when the sweep
// group indexes have not yet been computed. In that case, we can mark
// freely.
if (state() == State::Sweep && initialState != State::Sweep) {
if (zone->gcSweepGroupIndex < getCurrentSweepGroupIndex()) {
// Too late. This must have been added after we started collecting,
// and we've already processed its sweep group. Skip it.
continue;
}
if (zone->gcSweepGroupIndex > getCurrentSweepGroupIndex()) {
// Not ready yet. Wait until we reach the object's sweep group.
queuePos--;
return QueueSuspended;
}
}
if (marker().markColor() == MarkColor::Gray &&
zone->isGCMarkingBlackOnly()) {
// Have not yet reached the point where we can mark this object, so
// continue with the GC.
queuePos--;
return QueueSuspended;
}
if (marker().markColor() == MarkColor::Black && willRevertToGray) {
// If we put any black objects on the stack, we wouldn't be able to
// return to gray marking. So delay the marking until we're back to
// black marking.
queuePos--;
return QueueSuspended;
}
// Mark the object.
AutoEnterOOMUnsafeRegion oomUnsafe;
if (!marker().markOneObjectForTest(obj)) {
// If we overflowed the stack here and delayed marking, then we won't be
// testing what we think we're testing.
MOZ_ASSERT(obj->asTenured().arena()->onDelayedMarkingList());
oomUnsafe.crash("Overflowed stack while marking test queue");
}
} else if (val.isString()) {
JSLinearString* str = &val.toString()->asLinear();
if (js::StringEqualsLiteral(str, "yield") && isIncrementalGc()) {
return QueueYielded;
}
if (js::StringEqualsLiteral(str, "enter-weak-marking-mode") ||
js::StringEqualsLiteral(str, "abort-weak-marking-mode")) {
if (marker().isRegularMarking()) {
// We can't enter weak marking mode at just any time, so instead
// we'll stop processing the queue and continue on with the GC. Once
// we enter weak marking mode, we can continue to the rest of the
// queue. Note that we will also suspend for aborting, and then abort
// the earliest following weak marking mode.
queuePos--;
return QueueSuspended;
}
if (js::StringEqualsLiteral(str, "abort-weak-marking-mode")) {
marker().abortLinearWeakMarking();
}
} else if (js::StringEqualsLiteral(str, "drain")) {
auto unlimited = SliceBudget::unlimited();
MOZ_RELEASE_ASSERT(
marker().markUntilBudgetExhausted(unlimited, DontReportMarkTime));
} else if (js::StringEqualsLiteral(str, "set-color-gray")) {
queueMarkColor = mozilla::Some(MarkColor::Gray);
if (state() != State::Sweep || marker().hasBlackEntries()) {
// Cannot mark gray yet, so continue with the GC.
queuePos--;
return QueueSuspended;
}
marker().setMarkColor(MarkColor::Gray);
} else if (js::StringEqualsLiteral(str, "set-color-black")) {
queueMarkColor = mozilla::Some(MarkColor::Black);
marker().setMarkColor(MarkColor::Black);
} else if (js::StringEqualsLiteral(str, "unset-color")) {
queueMarkColor.reset();
}
}
}
#endif
return QueueComplete;
}
static bool IsEmergencyGC(JS::GCReason reason) {
return reason == JS::GCReason::LAST_DITCH ||
reason == JS::GCReason::MEM_PRESSURE;
}
void GCRuntime::finishCollection(JS::GCReason reason) {
assertBackgroundSweepingFinished();
MOZ_ASSERT(!hasDelayedMarking());
for (size_t i = 0; i < markers.length(); i++) {
const auto& marker = markers[i];
marker->stop();
if (i == 0) {
marker->resetStackCapacity();
} else {
marker->freeStack();
}
}
maybeStopPretenuring();
if (IsEmergencyGC(reason)) {
waitBackgroundFreeEnd();
}
TimeStamp currentTime = TimeStamp::Now();
updateSchedulingStateAfterCollection(currentTime);
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
zone->changeGCState(Zone::Finished, Zone::NoGC);
zone->notifyObservingDebuggers();
}
#ifdef JS_GC_ZEAL
clearSelectedForMarking();
#endif
schedulingState.updateHighFrequencyMode(lastGCEndTime_, currentTime,
tunables);
lastGCEndTime_ = currentTime;
checkGCStateNotInUse();
}
void GCRuntime::checkGCStateNotInUse() {
#ifdef DEBUG
for (auto& marker : markers) {
MOZ_ASSERT(!marker->isActive());
MOZ_ASSERT(marker->isDrained());
}
MOZ_ASSERT(!hasDelayedMarking());
MOZ_ASSERT(!lastMarkSlice);
MOZ_ASSERT(foregroundFinalizedArenas.ref().isNothing());
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
if (zone->wasCollected()) {
zone->arenas.checkGCStateNotInUse();
}
MOZ_ASSERT(!zone->wasGCStarted());
MOZ_ASSERT(!zone->needsIncrementalBarrier());
MOZ_ASSERT(!zone->isOnList());
}
MOZ_ASSERT(zonesToMaybeCompact.ref().isEmpty());
MOZ_ASSERT(cellsToAssertNotGray.ref().empty());
AutoLockHelperThreadState lock;
MOZ_ASSERT(!requestSliceAfterBackgroundTask);
MOZ_ASSERT(unmarkTask.isIdle(lock));
MOZ_ASSERT(markTask.isIdle(lock));
MOZ_ASSERT(sweepTask.isIdle(lock));
MOZ_ASSERT(decommitTask.isIdle(lock));
#endif
}
void GCRuntime::maybeStopPretenuring() {
nursery().maybeStopPretenuring(this);
size_t zonesWhereStringsEnabled = 0;
size_t zonesWhereBigIntsEnabled = 0;
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
if (zone->nurseryStringsDisabled || zone->nurseryBigIntsDisabled) {
// We may need to reset allocation sites and discard JIT code to recover
// if we find object lifetimes have changed.
if (zone->pretenuring.shouldResetPretenuredAllocSites()) {
zone->unknownAllocSite(JS::TraceKind::String)->maybeResetState();
zone->unknownAllocSite(JS::TraceKind::BigInt)->maybeResetState();
if (zone->nurseryStringsDisabled) {
zone->nurseryStringsDisabled = false;
zonesWhereStringsEnabled++;
}
if (zone->nurseryBigIntsDisabled) {
zone->nurseryBigIntsDisabled = false;
zonesWhereBigIntsEnabled++;
}
nursery().updateAllocFlagsForZone(zone);
}
}
}
if (nursery().reportPretenuring()) {
if (zonesWhereStringsEnabled) {
fprintf(stderr, "GC re-enabled nursery string allocation in %zu zones\n",
zonesWhereStringsEnabled);
}
if (zonesWhereBigIntsEnabled) {
fprintf(stderr, "GC re-enabled nursery big int allocation in %zu zones\n",
zonesWhereBigIntsEnabled);
}
}
}
void GCRuntime::updateSchedulingStateAfterCollection(TimeStamp currentTime) {
TimeDuration totalGCTime = stats().totalGCTime();
size_t totalInitialBytes = stats().initialCollectedBytes();
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
if (tunables.balancedHeapLimitsEnabled() && totalInitialBytes != 0) {
zone->updateCollectionRate(totalGCTime, totalInitialBytes);
}
zone->clearGCSliceThresholds();
zone->updateGCStartThresholds(*this);
}
}
void GCRuntime::updateAllGCStartThresholds() {
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
zone->updateGCStartThresholds(*this);
}
}
void GCRuntime::updateAllocationRates() {
// Calculate mutator time since the last update. This ignores the fact that
// the zone could have been created since the last update.
TimeStamp currentTime = TimeStamp::Now();
TimeDuration totalTime = currentTime - lastAllocRateUpdateTime;
if (collectorTimeSinceAllocRateUpdate >= totalTime) {
// It shouldn't happen but occasionally we see collector time being larger
// than total time. Skip the update in that case.
return;
}
TimeDuration mutatorTime = totalTime - collectorTimeSinceAllocRateUpdate;
for (AllZonesIter zone(this); !zone.done(); zone.next()) {
zone->updateAllocationRate(mutatorTime);
zone->updateGCStartThresholds(*this);
}
lastAllocRateUpdateTime = currentTime;
collectorTimeSinceAllocRateUpdate = TimeDuration::Zero();
}
static const char* GCHeapStateToLabel(JS::HeapState heapState) {
switch (heapState) {
case JS::HeapState::MinorCollecting:
return "Minor GC";
case JS::HeapState::MajorCollecting:
return "Major GC";
default:
MOZ_CRASH("Unexpected heap state when pushing GC profiling stack frame");
}
MOZ_ASSERT_UNREACHABLE("Should have exhausted every JS::HeapState variant!");
return nullptr;
}
static JS::ProfilingCategoryPair GCHeapStateToProfilingCategory(
JS::HeapState heapState) {
return heapState == JS::HeapState::MinorCollecting
? JS::ProfilingCategoryPair::GCCC_MinorGC
: JS::ProfilingCategoryPair::GCCC_MajorGC;
}
/* Start a new heap session. */
AutoHeapSession::AutoHeapSession(GCRuntime* gc, JS::HeapState heapState)
: gc(gc), prevState(gc->heapState_) {
MOZ_ASSERT(CurrentThreadCanAccessRuntime(gc->rt));
MOZ_ASSERT(prevState == JS::HeapState::Idle ||
(prevState == JS::HeapState::MajorCollecting &&
heapState == JS::HeapState::MinorCollecting));
MOZ_ASSERT(heapState != JS::HeapState::Idle);
gc->heapState_ = heapState;
if (heapState == JS::HeapState::MinorCollecting ||
heapState == JS::HeapState::MajorCollecting) {
profilingStackFrame.emplace(
gc->rt->mainContextFromOwnThread(), GCHeapStateToLabel(heapState),
GCHeapStateToProfilingCategory(heapState),
uint32_t(ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
}
}
AutoHeapSession::~AutoHeapSession() {
MOZ_ASSERT(JS::RuntimeHeapIsBusy());
gc->heapState_ = prevState;
}
static const char* MajorGCStateToLabel(State state) {
switch (state) {
case State::Mark:
return "js::GCRuntime::markUntilBudgetExhausted";
case State::Sweep:
return "js::GCRuntime::performSweepActions";
case State::Compact:
return "js::GCRuntime::compactPhase";
default:
MOZ_CRASH("Unexpected heap state when pushing GC profiling stack frame");
}
MOZ_ASSERT_UNREACHABLE("Should have exhausted every State variant!");
return nullptr;
}
static JS::ProfilingCategoryPair MajorGCStateToProfilingCategory(State state) {
switch (state) {
case State::Mark:
return JS::ProfilingCategoryPair::GCCC_MajorGC_Mark;
case State::Sweep:
return JS::ProfilingCategoryPair::GCCC_MajorGC_Sweep;
case State::Compact:
return JS::ProfilingCategoryPair::GCCC_MajorGC_Compact;
default:
MOZ_CRASH("Unexpected heap state when pushing GC profiling stack frame");
}
}
AutoMajorGCProfilerEntry::AutoMajorGCProfilerEntry(GCRuntime* gc)
: AutoGeckoProfilerEntry(gc->rt->mainContextFromAnyThread(),
MajorGCStateToLabel(gc->state()),
MajorGCStateToProfilingCategory(gc->state())) {
MOZ_ASSERT(gc->heapState() == JS::HeapState::MajorCollecting);
}
GCRuntime::IncrementalResult GCRuntime::resetIncrementalGC(
GCAbortReason reason) {
MOZ_ASSERT(reason != GCAbortReason::None);
// Drop as much work as possible from an ongoing incremental GC so
// we can start a new GC after it has finished.
if (incrementalState == State::NotActive) {
return IncrementalResult::Ok;
}
AutoGCSession session(this, JS::HeapState::MajorCollecting);
switch (incrementalState) {
case State::NotActive:
case State::MarkRoots:
case State::Finish:
MOZ_CRASH("Unexpected GC state in resetIncrementalGC");
break;
case State::Prepare:
unmarkTask.cancelAndWait();
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
zone->changeGCState(Zone::Prepare, Zone::NoGC);
zone->clearGCSliceThresholds();
zone->arenas.clearFreeLists();
zone->arenas.mergeArenasFromCollectingLists();
}
incrementalState = State::NotActive;
checkGCStateNotInUse();
break;
case State::Mark: {
// Cancel any ongoing marking.
for (auto& marker : markers) {
marker->reset();
}
resetDelayedMarking();
for (GCCompartmentsIter c(rt); !c.done(); c.next()) {
resetGrayList(c);
}
for (GCZonesIter zone(this); !zone.done(); zone.next()) {
zone->changeGCState(zone->initialMarkingState(), Zone::NoGC);
zone->clearGCSliceThresholds();
zone->arenas.unmarkPreMarkedFreeCells();
zone->arenas.mergeArenasFromCollectingLists();
}
{
AutoLockHelperThreadState lock;
lifoBlocksToFree.ref().freeAll();
}
lastMarkSlice = false;
incrementalState = State::Finish;
#ifdef DEBUG
for (auto& marker : markers) {
MOZ_ASSERT(!marker->shouldCheckCompartments());
}
#endif
break;
}
case State::Sweep: {
// Finish sweeping the current sweep group, then abort.
for (CompartmentsIter c(rt); !c.done(); c.next()) {
c->gcState.scheduledForDestruction = false;
}
abortSweepAfterCurrentGroup = true;
isCompacting = false;
break;
}
case State::Finalize: {
isCompacting = false;
break;
}
case State::Compact: {
// Skip any remaining zones that would have been compacted.
MOZ_ASSERT(isCompacting);
startedCompacting = true;
zonesToMaybeCompact.ref().clear();
break;
}
case State::Decommit: {
break;
}
}
stats().reset(reason);
return IncrementalResult::ResetIncremental;
}
AutoDisableBarriers::AutoDisableBarriers(GCRuntime* gc) : gc(gc) {
/*
* Clear needsIncrementalBarrier early so we don't do any write barriers
* during sweeping.
*/
for (GCZonesIter zone(gc); !zone.done(); zone.next()) {
if (zone->isGCMarking()) {
MOZ_ASSERT(zone->needsIncrementalBarrier());
zone->setNeedsIncrementalBarrier(false);
}
MOZ_ASSERT(!zone->needsIncrementalBarrier());
}
}
AutoDisableBarriers::~AutoDisableBarriers() {
for (GCZonesIter zone(gc); !zone.done(); zone.next()) {
MOZ_ASSERT(!zone->needsIncrementalBarrier());
if (zone->isGCMarking()) {
zone->setNeedsIncrementalBarrier(true);
}
}
}
static bool NeedToCollectNursery(GCRuntime* gc) {
return !gc->nursery().isEmpty() || !gc->storeBuffer().isEmpty();
}
#ifdef DEBUG
static const char* DescribeBudget(const SliceBudget& budget) {
constexpr size_t length = 32;
static char buffer[length];
budget.describe(buffer, length);
return buffer;
}
#endif
static bool ShouldPauseMutatorWhileWaiting(const SliceBudget& budget,
JS::GCReason reason,
bool budgetWasIncreased) {
// When we're nearing the incremental limit at which we will finish the
// collection synchronously, pause the main thread if there is only background
// GC work happening. This allows the GC to catch up and avoid hitting the
// limit.
return budget.isTimeBudget() &&
(reason == JS::GCReason::ALLOC_TRIGGER ||
reason == JS::GCReason::TOO_MUCH_MALLOC) &&
budgetWasIncreased;
}
void GCRuntime::incrementalSlice(SliceBudget& budget, JS::GCReason reason,
bool budgetWasIncreased) {
MOZ_ASSERT_IF(isIncrementalGCInProgress(), isIncremental);
AutoSetThreadIsPerformingGC performingGC(rt->gcContext());
AutoGCSession session(this, JS::HeapState::MajorCollecting);
bool destroyingRuntime = (reason == JS::GCReason::DESTROY_RUNTIME);
initialState = incrementalState;
isIncremental = !budget.isUnlimited();
useBackgroundThreads = ShouldUseBackgroundThreads(isIncremental, reason);
haveDiscardedJITCodeThisSlice = false;
#ifdef JS_GC_ZEAL
// Do the incremental collection type specified by zeal mode if the collection
// was triggered by runDebugGC() and incremental GC has not been cancelled by
// resetIncrementalGC().
useZeal = isIncremental && reason == JS::GCReason::DEBUG_GC;
#endif
#ifdef DEBUG
stats().log(
"Incremental: %d, lastMarkSlice: %d, useZeal: %d, budget: %s, "
"budgetWasIncreased: %d",
bool(isIncremental), bool(lastMarkSlice), bool(useZeal),
DescribeBudget(budget), budgetWasIncreased);
#endif
if (useZeal && hasIncrementalTwoSliceZealMode()) {
// Yields between slices occurs at predetermined points in these modes; the
// budget is not used. |isIncremental| is still true.
stats().log("Using unlimited budget for two-slice zeal mode");
budget = SliceBudget::unlimited();
}
bool shouldPauseMutator =
ShouldPauseMutatorWhileWaiting(budget, reason, budgetWasIncreased);
switch (incrementalState) {
case State::NotActive:
startCollection(reason);
incrementalState = State::Prepare;
if (!beginPreparePhase(reason, session)) {
incrementalState = State::NotActive;
break;
}
if (useZeal && hasZealMode(ZealMode::YieldBeforeRootMarking)) {
break;
}
[[fallthrough]];
case State::Prepare:
if (waitForBackgroundTask(unmarkTask, budget, shouldPauseMutator,
DontTriggerSliceWhenFinished) == NotFinished) {
break;
}
incrementalState = State::MarkRoots;
[[fallthrough]];
case State::MarkRoots:
endPreparePhase(reason);
beginMarkPhase(session);
incrementalState = State::Mark;
if (useZeal && hasZealMode(ZealMode::YieldBeforeMarking) &&
isIncremental) {
break;
}
[[fallthrough]];
case State::Mark:
if (mightSweepInThisSlice(budget.isUnlimited())) {
// Trace wrapper rooters before marking if we might start sweeping in
// this slice.
rt->mainContextFromOwnThread()->traceWrapperGCRooters(
marker().tracer());
}
{
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK);
if (markUntilBudgetExhausted(budget, useParallelMarking) ==
NotFinished) {
break;
}
}
assertNoMarkingWork();
/*
* There are a number of reasons why we break out of collection here,
* either ending the slice or to run a new interation of the loop in
* GCRuntime::collect()
*/
/*
* In incremental GCs where we have already performed more than one
* slice we yield after marking with the aim of starting the sweep in
* the next slice, since the first slice of sweeping can be expensive.
*
* This is modified by the various zeal modes. We don't yield in
* YieldBeforeMarking mode and we always yield in YieldBeforeSweeping
* mode.
*
* We will need to mark anything new on the stack when we resume, so
* we stay in Mark state.
*/
if (isIncremental && !lastMarkSlice) {
if ((initialState == State::Mark &&
!(useZeal && hasZealMode(ZealMode::YieldBeforeMarking))) ||
(useZeal && hasZealMode(ZealMode::YieldBeforeSweeping))) {
lastMarkSlice = true;
stats().log("Yielding before starting sweeping");
break;
}
}
incrementalState = State::Sweep;
lastMarkSlice = false;
beginSweepPhase(reason, session);
[[fallthrough]];
case State::Sweep:
if (storeBuffer().mayHavePointersToDeadCells()) {
collectNurseryFromMajorGC(reason);
}
if (initialState == State::Sweep) {
rt->mainContextFromOwnThread()->traceWrapperGCRooters(
marker().tracer());
}
if (performSweepActions(budget) == NotFinished) {
break;
}
endSweepPhase(destroyingRuntime);
incrementalState = State::Finalize;
[[fallthrough]];
case State::Finalize:
if (waitForBackgroundTask(sweepTask, budget, shouldPauseMutator,
TriggerSliceWhenFinished) == NotFinished) {
break;
}
assertBackgroundSweepingFinished();
{
// Sweep the zones list now that background finalization is finished to
// remove and free dead zones, compartments and realms.
gcstats::AutoPhase ap1(stats(), gcstats::PhaseKind::SWEEP);
gcstats::AutoPhase ap2(stats(), gcstats::PhaseKind::DESTROY);
sweepZones(rt->gcContext(), destroyingRuntime);
}
MOZ_ASSERT(!startedCompacting);
incrementalState = State::Compact;
// Always yield before compacting since it is not incremental.
if (isCompacting && !budget.isUnlimited()) {
break;
}
[[fallthrough]];
case State::Compact:
if (isCompacting) {
if (NeedToCollectNursery(this)) {
collectNurseryFromMajorGC(reason);
}
storeBuffer().checkEmpty();
if (!startedCompacting) {
beginCompactPhase();
}
if (compactPhase(reason, budget, session) == NotFinished) {
break;
}
endCompactPhase();
}
startDecommit();
incrementalState = State::Decommit;
[[fallthrough]];
case State::Decommit:
if (waitForBackgroundTask(decommitTask, budget, shouldPauseMutator,
TriggerSliceWhenFinished) == NotFinished) {
break;
}
incrementalState = State::Finish;
[[fallthrough]];
case State::Finish:
finishCollection(reason);
incrementalState = State::NotActive;
break;
}
#ifdef DEBUG
MOZ_ASSERT(safeToYield);
for (auto& marker : markers) {
MOZ_ASSERT(marker->markColor() == MarkColor::Black);
}
MOZ_ASSERT(!rt->gcContext()->hasJitCodeToPoison());
#endif
}
void GCRuntime::collectNurseryFromMajorGC(JS::GCReason reason) {
collectNursery(gcOptions(), JS::GCReason::EVICT_NURSERY,
gcstats::PhaseKind::EVICT_NURSERY_FOR_MAJOR_GC);
MOZ_ASSERT(nursery().isEmpty());
MOZ_ASSERT(storeBuffer().isEmpty());
}
bool GCRuntime::hasForegroundWork() const {
switch (incrementalState) {
case State::NotActive:
// Incremental GC is not running and no work is pending.
return false;
case State::Prepare:
// We yield in the Prepare state after starting unmarking.
return !unmarkTask.wasStarted();
case State::Finalize:
// We yield in the Finalize state to wait for background sweeping.
return !isBackgroundSweeping();
case State::Decommit:
// We yield in the Decommit state to wait for background decommit.
return !decommitTask.wasStarted();
default:
// In all other states there is still work to do.
return true;
}
}
IncrementalProgress GCRuntime::waitForBackgroundTask(
GCParallelTask& task, const SliceBudget& budget, bool shouldPauseMutator,
ShouldTriggerSliceWhenFinished triggerSlice) {
// Wait here in non-incremental collections, or if we want to pause the
// mutator to let the GC catch up.
if (budget.isUnlimited() || shouldPauseMutator) {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::WAIT_BACKGROUND_THREAD);
Maybe<TimeStamp> deadline;
if (budget.isTimeBudget()) {
deadline.emplace(budget.deadline());
}
task.join(deadline);
}
// In incremental collections, yield if the task has not finished and
// optionally request a slice to notify us when this happens.
if (!budget.isUnlimited()) {
AutoLockHelperThreadState lock;
if (task.wasStarted(lock)) {
if (triggerSlice) {
requestSliceAfterBackgroundTask = true;
}
return NotFinished;
}
task.joinWithLockHeld(lock);
}
MOZ_ASSERT(task.isIdle());
if (triggerSlice) {
cancelRequestedGCAfterBackgroundTask();
}
return Finished;
}
GCAbortReason gc::IsIncrementalGCUnsafe(JSRuntime* rt) {
MOZ_ASSERT(!rt->mainContextFromOwnThread()->suppressGC);
if (!rt->gc.isIncrementalGCAllowed()) {
return GCAbortReason::IncrementalDisabled;
}
return GCAbortReason::None;
}
inline void GCRuntime::checkZoneIsScheduled(Zone* zone, JS::GCReason reason,
const char* trigger) {
#ifdef DEBUG
if (zone->isGCScheduled()) {
return;
}
fprintf(stderr,
"checkZoneIsScheduled: Zone %p not scheduled as expected in %s GC "
"for %s trigger\n",
zone, JS::ExplainGCReason(reason), trigger);
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
fprintf(stderr, " Zone %p:%s%s\n", zone.get(),
zone->isAtomsZone() ? " atoms" : "",
zone->isGCScheduled() ? " scheduled" : "");
}
fflush(stderr);
MOZ_CRASH("Zone not scheduled");
#endif
}
GCRuntime::IncrementalResult GCRuntime::budgetIncrementalGC(
bool nonincrementalByAPI, JS::GCReason reason, SliceBudget& budget) {
if (nonincrementalByAPI) {
stats().nonincremental(GCAbortReason::NonIncrementalRequested);
budget = SliceBudget::unlimited();
// Reset any in progress incremental GC if this was triggered via the
// API. This isn't required for correctness, but sometimes during tests
// the caller expects this GC to collect certain objects, and we need
// to make sure to collect everything possible.
if (reason != JS::GCReason::ALLOC_TRIGGER) {
return resetIncrementalGC(GCAbortReason::NonIncrementalRequested);
}
return IncrementalResult::Ok;
}
if (reason == JS::GCReason::ABORT_GC) {
budget = SliceBudget::unlimited();
stats().nonincremental(GCAbortReason::AbortRequested);
return resetIncrementalGC(GCAbortReason::AbortRequested);
}
if (!budget.isUnlimited()) {
GCAbortReason unsafeReason = IsIncrementalGCUnsafe(rt);
if (unsafeReason == GCAbortReason::None) {
if (reason == JS::GCReason::COMPARTMENT_REVIVED) {
unsafeReason = GCAbortReason::CompartmentRevived;
} else if (!incrementalGCEnabled) {
unsafeReason = GCAbortReason::ModeChange;
}
}
if (unsafeReason != GCAbortReason::None) {
budget = SliceBudget::unlimited();
stats().nonincremental(unsafeReason);
return resetIncrementalGC(unsafeReason);
}
}
GCAbortReason resetReason = GCAbortReason::None;
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
if (zone->gcHeapSize.bytes() >=
zone->gcHeapThreshold.incrementalLimitBytes()) {
checkZoneIsScheduled(zone, reason, "GC bytes");
budget = SliceBudget::unlimited();
stats().nonincremental(GCAbortReason::GCBytesTrigger);
if (zone->wasGCStarted() && zone->gcState() > Zone::Sweep) {
resetReason = GCAbortReason::GCBytesTrigger;
}
}
if (zone->mallocHeapSize.bytes() >=
zone->mallocHeapThreshold.incrementalLimitBytes()) {
checkZoneIsScheduled(zone, reason, "malloc bytes");
budget = SliceBudget::unlimited();
stats().nonincremental(GCAbortReason::MallocBytesTrigger);
if (zone->wasGCStarted() && zone->gcState() > Zone::Sweep) {
resetReason = GCAbortReason::MallocBytesTrigger;
}
}
if (zone->jitHeapSize.bytes() >=
zone->jitHeapThreshold.incrementalLimitBytes()) {
checkZoneIsScheduled(zone, reason, "JIT code bytes");
budget = SliceBudget::unlimited();
stats().nonincremental(GCAbortReason::JitCodeBytesTrigger);
if (zone->wasGCStarted() && zone->gcState() > Zone::Sweep) {
resetReason = GCAbortReason::JitCodeBytesTrigger;
}
}
if (isIncrementalGCInProgress() &&
zone->isGCScheduled() != zone->wasGCStarted()) {
budget = SliceBudget::unlimited();
resetReason = GCAbortReason::ZoneChange;
}
}
if (resetReason != GCAbortReason::None) {
return resetIncrementalGC(resetReason);
}
return IncrementalResult::Ok;
}
bool GCRuntime::maybeIncreaseSliceBudget(SliceBudget& budget) {
if (js::SupportDifferentialTesting()) {
return false;
}
if (!budget.isTimeBudget() || !isIncrementalGCInProgress()) {
return false;
}
bool wasIncreasedForLongCollections =
maybeIncreaseSliceBudgetForLongCollections(budget);
bool wasIncreasedForUgentCollections =
maybeIncreaseSliceBudgetForUrgentCollections(budget);
return wasIncreasedForLongCollections || wasIncreasedForUgentCollections;
}
// Return true if the budget is actually extended after rounding.
static bool ExtendBudget(SliceBudget& budget, double newDuration) {
long millis = lround(newDuration);
if (millis <= budget.timeBudget()) {
return false;
}
bool idleTriggered = budget.idle;
budget = SliceBudget(TimeBudget(millis), nullptr); // Uninterruptible.
budget.idle = idleTriggered;
budget.extended = true;
return true;
}
bool GCRuntime::maybeIncreaseSliceBudgetForLongCollections(
SliceBudget& budget) {
// For long-running collections, enforce a minimum time budget that increases
// linearly with time up to a maximum.
// All times are in milliseconds.
struct BudgetAtTime {
double time;
double budget;
};
const BudgetAtTime MinBudgetStart{1500, 0.0};
const BudgetAtTime MinBudgetEnd{2500, 100.0};
double totalTime = (TimeStamp::Now() - lastGCStartTime()).ToMilliseconds();
double minBudget =
LinearInterpolate(totalTime, MinBudgetStart.time, MinBudgetStart.budget,
MinBudgetEnd.time, MinBudgetEnd.budget);
return ExtendBudget(budget, minBudget);
}
bool GCRuntime::maybeIncreaseSliceBudgetForUrgentCollections(
SliceBudget& budget) {
// Enforce a minimum time budget based on how close we are to the incremental
// limit.
size_t minBytesRemaining = SIZE_MAX;
for (AllZonesIter zone(this); !zone.done(); zone.next()) {
if (!zone->wasGCStarted()) {
continue;
}
size_t gcBytesRemaining =
zone->gcHeapThreshold.incrementalBytesRemaining(zone->gcHeapSize);
minBytesRemaining = std::min(minBytesRemaining, gcBytesRemaining);
size_t mallocBytesRemaining =
zone->mallocHeapThreshold.incrementalBytesRemaining(
zone->mallocHeapSize);
minBytesRemaining = std::min(minBytesRemaining, mallocBytesRemaining);
}
if (minBytesRemaining < tunables.urgentThresholdBytes() &&
minBytesRemaining != 0) {
// Increase budget based on the reciprocal of the fraction remaining.
double fractionRemaining =
double(minBytesRemaining) / double(tunables.urgentThresholdBytes());
double minBudget = double(defaultSliceBudgetMS()) / fractionRemaining;
return ExtendBudget(budget, minBudget);
}
return false;
}
static void ScheduleZones(GCRuntime* gc, JS::GCReason reason) {
for (ZonesIter zone(gc, WithAtoms); !zone.done(); zone.next()) {
// Re-check heap threshold for alloc-triggered zones that were not
// previously collected. Now we have allocation rate data, the heap limit
// may have been increased beyond the current size.
if (gc->tunables.balancedHeapLimitsEnabled() && zone->isGCScheduled() &&
zone->smoothedCollectionRate.ref().isNothing() &&
reason == JS::GCReason::ALLOC_TRIGGER &&
zone->gcHeapSize.bytes() < zone->gcHeapThreshold.startBytes()) {
zone->unscheduleGC(); // May still be re-scheduled below.
}
if (gc->isShutdownGC()) {
zone->scheduleGC();
}
if (!gc->isPerZoneGCEnabled()) {
zone->scheduleGC();
}
// To avoid resets, continue to collect any zones that were being
// collected in a previous slice.
if (gc->isIncrementalGCInProgress() && zone->wasGCStarted()) {
zone->scheduleGC();
}
// This is a heuristic to reduce the total number of collections.
bool inHighFrequencyMode = gc->schedulingState.inHighFrequencyGCMode();
if (zone->gcHeapSize.bytes() >=
zone->gcHeapThreshold.eagerAllocTrigger(inHighFrequencyMode) ||
zone->mallocHeapSize.bytes() >=
zone->mallocHeapThreshold.eagerAllocTrigger(inHighFrequencyMode) ||
zone->jitHeapSize.bytes() >= zone->jitHeapThreshold.startBytes()) {
zone->scheduleGC();
}
}
}
static void UnscheduleZones(GCRuntime* gc) {
for (ZonesIter zone(gc->rt, WithAtoms); !zone.done(); zone.next()) {
zone->unscheduleGC();
}
}
class js::gc::AutoCallGCCallbacks {
GCRuntime& gc_;
JS::GCReason reason_;
public:
explicit AutoCallGCCallbacks(GCRuntime& gc, JS::GCReason reason)
: gc_(gc), reason_(reason) {
gc_.maybeCallGCCallback(JSGC_BEGIN, reason);
}
~AutoCallGCCallbacks() { gc_.maybeCallGCCallback(JSGC_END, reason_); }
};
void GCRuntime::maybeCallGCCallback(JSGCStatus status, JS::GCReason reason) {
if (!gcCallback.ref().op) {
return;
}
if (isIncrementalGCInProgress()) {
return;
}
if (gcCallbackDepth == 0) {
// Save scheduled zone information in case the callback clears it.
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
zone->gcScheduledSaved_ = zone->gcScheduled_;
}
}
// Save and clear GC options and state in case the callback reenters GC.
JS::GCOptions options = gcOptions();
maybeGcOptions = Nothing();
bool savedFullGCRequested = fullGCRequested;
fullGCRequested = false;
gcCallbackDepth++;
callGCCallback(status, reason);
MOZ_ASSERT(gcCallbackDepth != 0);
gcCallbackDepth--;
// Restore the original GC options.
maybeGcOptions = Some(options);
// At the end of a GC, clear out the fullGCRequested state. At the start,
// restore the previous setting.
fullGCRequested = (status == JSGC_END) ? false : savedFullGCRequested;
if (gcCallbackDepth == 0) {
// Ensure any zone that was originally scheduled stays scheduled.
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
zone->gcScheduled_ = zone->gcScheduled_ || zone->gcScheduledSaved_;
}
}
}
/*
* We disable inlining to ensure that the bottom of the stack with possible GC
* roots recorded in MarkRuntime excludes any pointers we use during the marking
* implementation.
*/
MOZ_NEVER_INLINE GCRuntime::IncrementalResult GCRuntime::gcCycle(
bool nonincrementalByAPI, const SliceBudget& budgetArg,
JS::GCReason reason) {
// Assert if this is a GC unsafe region.
rt->mainContextFromOwnThread()->verifyIsSafeToGC();
// It's ok if threads other than the main thread have suppressGC set, as
// they are operating on zones which will not be collected from here.
MOZ_ASSERT(!rt->mainContextFromOwnThread()->suppressGC);
// This reason is used internally. See below.
MOZ_ASSERT(reason != JS::GCReason::RESET);
// Background finalization and decommit are finished by definition before we
// can start a new major GC. Background allocation may still be running, but
// that's OK because chunk pools are protected by the GC lock.
if (!isIncrementalGCInProgress()) {
assertBackgroundSweepingFinished();
MOZ_ASSERT(decommitTask.isIdle());
}
// Note that GC callbacks are allowed to re-enter GC.
AutoCallGCCallbacks callCallbacks(*this, reason);
// Increase slice budget for long running collections before it is recorded by
// AutoGCSlice.
SliceBudget budget(budgetArg);
bool budgetWasIncreased = maybeIncreaseSliceBudget(budget);
ScheduleZones(this, reason);
auto updateCollectorTime = MakeScopeExit([&] {
if (const gcstats::Statistics::SliceData* slice = stats().lastSlice()) {
collectorTimeSinceAllocRateUpdate += slice->duration();
}
});
gcstats::AutoGCSlice agc(stats(), scanZonesBeforeGC(), gcOptions(), budget,
reason, budgetWasIncreased);
IncrementalResult result =
budgetIncrementalGC(nonincrementalByAPI, reason, budget);
if (result == IncrementalResult::ResetIncremental) {
if (incrementalState == State::NotActive) {
// The collection was reset and has finished.
return result;
}
// The collection was reset but we must finish up some remaining work.
reason = JS::GCReason::RESET;
}
majorGCTriggerReason = JS::GCReason::NO_REASON;
MOZ_ASSERT(!stats().hasTrigger());
incGcNumber();
incGcSliceNumber();
gcprobes::MajorGCStart();
incrementalSlice(budget, reason, budgetWasIncreased);
gcprobes::MajorGCEnd();
MOZ_ASSERT_IF(result == IncrementalResult::ResetIncremental,
!isIncrementalGCInProgress());
return result;
}
inline bool GCRuntime::mightSweepInThisSlice(bool nonIncremental) {
MOZ_ASSERT(incrementalState < State::Sweep);
return nonIncremental || lastMarkSlice || hasIncrementalTwoSliceZealMode();
}
#ifdef JS_GC_ZEAL
static bool IsDeterministicGCReason(JS::GCReason reason) {
switch (reason) {
case JS::GCReason::API:
case JS::GCReason::DESTROY_RUNTIME:
case JS::GCReason::LAST_DITCH:
case JS::GCReason::TOO_MUCH_MALLOC:
case JS::GCReason::TOO_MUCH_WASM_MEMORY:
case JS::GCReason::TOO_MUCH_JIT_CODE:
case JS::GCReason::ALLOC_TRIGGER:
case JS::GCReason::DEBUG_GC:
case JS::GCReason::CC_FORCED:
case JS::GCReason::SHUTDOWN_CC:
case JS::GCReason::ABORT_GC:
case JS::GCReason::DISABLE_GENERATIONAL_GC:
case JS::GCReason::FINISH_GC:
case JS::GCReason::PREPARE_FOR_TRACING:
return true;
default:
return false;
}
}
#endif
gcstats::ZoneGCStats GCRuntime::scanZonesBeforeGC() {
gcstats::ZoneGCStats zoneStats;
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
zoneStats.zoneCount++;
zoneStats.compartmentCount += zone->compartments().length();
for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) {
zoneStats.realmCount += comp->realms().length();
}
if (zone->isGCScheduled()) {
zoneStats.collectedZoneCount++;
zoneStats.collectedCompartmentCount += zone->compartments().length();
}
}
return zoneStats;
}
// The GC can only clean up scheduledForDestruction realms that were marked live
// by a barrier (e.g. by RemapWrappers from a navigation event). It is also
// common to have realms held live because they are part of a cycle in gecko,
// e.g. involving the HTMLDocument wrapper. In this case, we need to run the
// CycleCollector in order to remove these edges before the realm can be freed.
void GCRuntime::maybeDoCycleCollection() {
const static float ExcessiveGrayRealms = 0.8f;
const static size_t LimitGrayRealms = 200;
size_t realmsTotal = 0;
size_t realmsGray = 0;
for (RealmsIter realm(rt); !realm.done(); realm.next()) {
++realmsTotal;
GlobalObject* global = realm->unsafeUnbarrieredMaybeGlobal();
if (global && global->isMarkedGray()) {
++realmsGray;
}
}
float grayFraction = float(realmsGray) / float(realmsTotal);
if (grayFraction > ExcessiveGrayRealms || realmsGray > LimitGrayRealms) {
callDoCycleCollectionCallback(rt->mainContextFromOwnThread());
}
}
void GCRuntime::checkCanCallAPI() {
MOZ_RELEASE_ASSERT(CurrentThreadCanAccessRuntime(rt));
/* If we attempt to invoke the GC while we are running in the GC, assert. */
MOZ_RELEASE_ASSERT(!JS::RuntimeHeapIsBusy());
}
bool GCRuntime::checkIfGCAllowedInCurrentState(JS::GCReason reason) {
if (rt->mainContextFromOwnThread()->suppressGC) {
return false;
}
// Only allow shutdown GCs when we're destroying the runtime. This keeps
// the GC callback from triggering a nested GC and resetting global state.
if (rt->isBeingDestroyed() && !isShutdownGC()) {
return false;
}
#ifdef JS_GC_ZEAL
if (deterministicOnly && !IsDeterministicGCReason(reason)) {
return false;
}
#endif
return true;
}
bool GCRuntime::shouldRepeatForDeadZone(JS::GCReason reason) {
MOZ_ASSERT_IF(reason == JS::GCReason::COMPARTMENT_REVIVED, !isIncremental);
MOZ_ASSERT(!isIncrementalGCInProgress());
if (!isIncremental) {
return false;
}
for (CompartmentsIter c(rt); !c.done(); c.next()) {
if (c->gcState.scheduledForDestruction) {
return true;
}
}
return false;
}
struct MOZ_RAII AutoSetZoneSliceThresholds {
explicit AutoSetZoneSliceThresholds(GCRuntime* gc) : gc(gc) {
// On entry, zones that are already collecting should have a slice threshold
// set.
for (ZonesIter zone(gc, WithAtoms); !zone.done(); zone.next()) {
MOZ_ASSERT(zone->wasGCStarted() ==
zone->gcHeapThreshold.hasSliceThreshold());
MOZ_ASSERT(zone->wasGCStarted() ==
zone->mallocHeapThreshold.hasSliceThreshold());
}
}
~AutoSetZoneSliceThresholds() {
// On exit, update the thresholds for all collecting zones.
bool waitingOnBGTask = gc->isWaitingOnBackgroundTask();
for (ZonesIter zone(gc, WithAtoms); !zone.done(); zone.next()) {
if (zone->wasGCStarted()) {
zone->setGCSliceThresholds(*gc, waitingOnBGTask);
} else {
MOZ_ASSERT(!zone->gcHeapThreshold.hasSliceThreshold());
MOZ_ASSERT(!zone->mallocHeapThreshold.hasSliceThreshold());
}
}
}
GCRuntime* gc;
};
void GCRuntime::collect(bool nonincrementalByAPI, const SliceBudget& budget,
JS::GCReason reason) {
TimeStamp startTime = TimeStamp::Now();
auto timer = MakeScopeExit([&] {
if (Realm* realm = rt->mainContextFromOwnThread()->realm()) {
realm->timers.gcTime += TimeStamp::Now() - startTime;
}
});
auto clearGCOptions = MakeScopeExit([&] {
if (!isIncrementalGCInProgress()) {
maybeGcOptions = Nothing();
}
});
MOZ_ASSERT(reason != JS::GCReason::NO_REASON);
// Checks run for each request, even if we do not actually GC.
checkCanCallAPI();
// Check if we are allowed to GC at this time before proceeding.
if (!checkIfGCAllowedInCurrentState(reason)) {
return;
}
stats().log("GC slice starting in state %s", StateName(incrementalState));
AutoStopVerifyingBarriers av(rt, isShutdownGC());
AutoMaybeLeaveAtomsZone leaveAtomsZone(rt->mainContextFromOwnThread());
AutoSetZoneSliceThresholds sliceThresholds(this);
schedulingState.updateHighFrequencyModeForReason(reason);
if (!isIncrementalGCInProgress() && tunables.balancedHeapLimitsEnabled()) {
updateAllocationRates();
}
bool repeat;
do {
IncrementalResult cycleResult =
gcCycle(nonincrementalByAPI, budget, reason);
if (reason == JS::GCReason::ABORT_GC) {
MOZ_ASSERT(!isIncrementalGCInProgress());
stats().log("GC aborted by request");
break;
}
/*
* Sometimes when we finish a GC we need to immediately start a new one.
* This happens in the following cases:
* - when we reset the current GC
* - when finalizers drop roots during shutdown
* - when zones that we thought were dead at the start of GC are
* not collected (see the large comment in beginMarkPhase)
*/
repeat = false;
if (!isIncrementalGCInProgress()) {
if (cycleResult == ResetIncremental) {
repeat = true;
} else if (rootsRemoved && isShutdownGC()) {
/* Need to re-schedule all zones for GC. */
JS::PrepareForFullGC(rt->mainContextFromOwnThread());
repeat = true;
reason = JS::GCReason::ROOTS_REMOVED;
} else if (shouldRepeatForDeadZone(reason)) {
repeat = true;
reason = JS::GCReason::COMPARTMENT_REVIVED;
}
}
} while (repeat);
if (reason == JS::GCReason::COMPARTMENT_REVIVED) {
maybeDoCycleCollection();
}
#ifdef JS_GC_ZEAL
if (hasZealMode(ZealMode::CheckHeapAfterGC)) {
gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::TRACE_HEAP);
CheckHeapAfterGC(rt);
}
if (hasZealMode(ZealMode::CheckGrayMarking) && !isIncrementalGCInProgress()) {
MOZ_RELEASE_ASSERT(CheckGrayMarkingState(rt));
}
#endif
stats().log("GC slice ending in state %s", StateName(incrementalState));
UnscheduleZones(this);
}
SliceBudget GCRuntime::defaultBudget(JS::GCReason reason, int64_t millis) {
// millis == 0 means use internal GC scheduling logic to come up with
// a duration for the slice budget. This may end up still being zero
// based on preferences.
if (millis == 0) {
millis = defaultSliceBudgetMS();
}
// If the embedding has registered a callback for creating SliceBudgets,
// then use it.
if (createBudgetCallback) {
return createBudgetCallback(reason, millis);
}
// Otherwise, the preference can request an unlimited duration slice.
if (millis == 0) {
return SliceBudget::unlimited();
}
return SliceBudget(TimeBudget(millis));
}
void GCRuntime::gc(JS::GCOptions options, JS::GCReason reason) {
if (!isIncrementalGCInProgress()) {
setGCOptions(options);
}
collect(true, SliceBudget::unlimited(), reason);
}
void GCRuntime::startGC(JS::GCOptions options, JS::GCReason reason,
const js::SliceBudget& budget) {
MOZ_ASSERT(!isIncrementalGCInProgress());
setGCOptions(options);
if (!JS::IsIncrementalGCEnabled(rt->mainContextFromOwnThread())) {
collect(true, SliceBudget::unlimited(), reason);
return;
}
collect(false, budget, reason);
}
void GCRuntime::setGCOptions(JS::GCOptions options) {
MOZ_ASSERT(maybeGcOptions == Nothing());
maybeGcOptions = Some(options);
}
void GCRuntime::gcSlice(JS::GCReason reason, const js::SliceBudget& budget) {
MOZ_ASSERT(isIncrementalGCInProgress());
collect(false, budget, reason);
}
void GCRuntime::finishGC(JS::GCReason reason) {
MOZ_ASSERT(isIncrementalGCInProgress());
// If we're not collecting because we're out of memory then skip the
// compacting phase if we need to finish an ongoing incremental GC
// non-incrementally to avoid janking the browser.
if (!IsOOMReason(initialReason)) {
if (incrementalState == State::Compact) {
abortGC();
return;
}
isCompacting = false;
}
collect(false, SliceBudget::unlimited(), reason);
}
void GCRuntime::abortGC() {
MOZ_ASSERT(isIncrementalGCInProgress());
checkCanCallAPI();
MOZ_ASSERT(!rt->mainContextFromOwnThread()->suppressGC);
collect(false, SliceBudget::unlimited(), JS::GCReason::ABORT_GC);
}
static bool ZonesSelected(GCRuntime* gc) {
for (ZonesIter zone(gc, WithAtoms); !zone.done(); zone.next()) {
if (zone->isGCScheduled()) {
return true;
}
}
return false;
}
void GCRuntime::startDebugGC(JS::GCOptions options, const SliceBudget& budget) {
MOZ_ASSERT(!isIncrementalGCInProgress());
setGCOptions(options);
if (!ZonesSelected(this)) {
JS::PrepareForFullGC(rt->mainContextFromOwnThread());
}
collect(false, budget, JS::GCReason::DEBUG_GC);
}
void GCRuntime::debugGCSlice(const SliceBudget& budget) {
MOZ_ASSERT(isIncrementalGCInProgress());
if (!ZonesSelected(this)) {
JS::PrepareForIncrementalGC(rt->mainContextFromOwnThread());
}
collect(false, budget, JS::GCReason::DEBUG_GC);
}
/* Schedule a full GC unless a zone will already be collected. */
void js::PrepareForDebugGC(JSRuntime* rt) {
if (!ZonesSelected(&rt->gc)) {
JS::PrepareForFullGC(rt->mainContextFromOwnThread());
}
}
void GCRuntime::onOutOfMallocMemory() {
// Stop allocating new chunks.
allocTask.cancelAndWait();
// Make sure we release anything queued for release.
decommitTask.join();
nursery().joinDecommitTask();
// Wait for background free of nursery huge slots to finish.
sweepTask.join();
AutoLockGC lock(this);
onOutOfMallocMemory(lock);
}
void GCRuntime::onOutOfMallocMemory(const AutoLockGC& lock) {
#ifdef DEBUG
// Release any relocated arenas we may be holding on to, without releasing
// the GC lock.
releaseHeldRelocatedArenasWithoutUnlocking(lock);
#endif
// Throw away any excess chunks we have lying around.
freeEmptyChunks(lock);
// Immediately decommit as many arenas as possible in the hopes that this
// might let the OS scrape together enough pages to satisfy the failing
// malloc request.
if (DecommitEnabled()) {
decommitFreeArenasWithoutUnlocking(lock);
}
}
void GCRuntime::minorGC(JS::GCReason reason, gcstats::PhaseKind phase) {
MOZ_ASSERT(!JS::RuntimeHeapIsBusy());
MOZ_ASSERT_IF(reason == JS::GCReason::EVICT_NURSERY,
!rt->mainContextFromOwnThread()->suppressGC);
if (rt->mainContextFromOwnThread()->suppressGC) {
return;
}
incGcNumber();
collectNursery(JS::GCOptions::Normal, reason, phase);
#ifdef JS_GC_ZEAL
if (hasZealMode(ZealMode::CheckHeapAfterGC)) {
gcstats::AutoPhase ap(stats(), phase);
CheckHeapAfterGC(rt);
}
#endif
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
maybeTriggerGCAfterAlloc(zone);
maybeTriggerGCAfterMalloc(zone);
}
}
void GCRuntime::collectNursery(JS::GCOptions options, JS::GCReason reason,
gcstats::PhaseKind phase) {
AutoMaybeLeaveAtomsZone leaveAtomsZone(rt->mainContextFromOwnThread());
uint32_t numAllocs = 0;
for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) {
numAllocs += zone->getAndResetTenuredAllocsSinceMinorGC();
}
stats().setAllocsSinceMinorGCTenured(numAllocs);
gcstats::AutoPhase ap(stats(), phase);
nursery().collect(options, reason);
startBackgroundFreeAfterMinorGC();
// We ignore gcMaxBytes when allocating for minor collection. However, if we
// overflowed, we disable the nursery. The next time we allocate, we'll fail
// because bytes >= gcMaxBytes.
if (heapSize.bytes() >= tunables.gcMaxBytes()) {
if (!nursery().isEmpty()) {
nursery().collect(options, JS::GCReason::DISABLE_GENERATIONAL_GC);
MOZ_ASSERT(nursery().isEmpty());
startBackgroundFreeAfterMinorGC();
}
nursery().disable();
}
}
void GCRuntime::startBackgroundFreeAfterMinorGC() {
// Called after nursery collection. Free whatever blocks are safe to free now.
AutoLockHelperThreadState lock;
lifoBlocksToFree.ref().transferFrom(&lifoBlocksToFreeAfterNextMinorGC.ref());
if (nursery().tenuredEverything) {
lifoBlocksToFree.ref().transferFrom(
&lifoBlocksToFreeAfterFullMinorGC.ref());
} else {
lifoBlocksToFreeAfterNextMinorGC.ref().transferFrom(
&lifoBlocksToFreeAfterFullMinorGC.ref());
}
if (lifoBlocksToFree.ref().isEmpty() &&
buffersToFreeAfterMinorGC.ref().empty()) {
return;
}
freeTask.startOrRunIfIdle(lock);
}
bool GCRuntime::gcIfRequestedImpl(bool eagerOk) {
// This method returns whether a major GC was performed.
if (nursery().minorGCRequested()) {
minorGC(nursery().minorGCTriggerReason());
}
JS::GCReason reason = wantMajorGC(eagerOk);
if (reason == JS::GCReason::NO_REASON) {
return false;
}
SliceBudget budget = defaultBudget(reason, 0);
if (!isIncrementalGCInProgress()) {
startGC(JS::GCOptions::Normal, reason, budget);
} else {
gcSlice(reason, budget);
}
return true;
}
void js::gc::FinishGC(JSContext* cx, JS::GCReason reason) {
// Calling this when GC is suppressed won't have any effect.
MOZ_ASSERT(!cx->suppressGC);
// GC callbacks may run arbitrary code, including JS. Check this regardless of
// whether we GC for this invocation.
MOZ_ASSERT(cx->isNurseryAllocAllowed());
if (JS::IsIncrementalGCInProgress(cx)) {
JS::PrepareForIncrementalGC(cx);
JS::FinishIncrementalGC(cx, reason);
}
}
void js::gc::WaitForBackgroundTasks(JSContext* cx) {
cx->runtime()->gc.waitForBackgroundTasks();
}
void GCRuntime::waitForBackgroundTasks() {
MOZ_ASSERT(!isIncrementalGCInProgress());
MOZ_ASSERT(sweepTask.isIdle());
MOZ_ASSERT(decommitTask.isIdle());
MOZ_ASSERT(markTask.isIdle());
allocTask.join();
freeTask.join();
nursery().joinDecommitTask();
}
Realm* js::NewRealm(JSContext* cx, JSPrincipals* principals,
const JS::RealmOptions& options) {
JSRuntime* rt = cx->runtime();
JS_AbortIfWrongThread(cx);
UniquePtr<Zone> zoneHolder;
UniquePtr<Compartment> compHolder;
Compartment* comp = nullptr;
Zone* zone = nullptr;
JS::CompartmentSpecifier compSpec =
options.creationOptions().compartmentSpecifier();
switch (compSpec) {
case JS::CompartmentSpecifier::NewCompartmentInSystemZone:
// systemZone might be null here, in which case we'll make a zone and
// set this field below.
zone = rt->gc.systemZone;
break;
case JS::CompartmentSpecifier::NewCompartmentInExistingZone:
zone = options.creationOptions().zone();
MOZ_ASSERT(zone);
break;
case JS::CompartmentSpecifier::ExistingCompartment:
comp = options.creationOptions().compartment();
zone = comp->zone();
break;
case JS::CompartmentSpecifier::NewCompartmentAndZone:
break;
}
if (!zone) {
Zone::Kind kind = Zone::NormalZone;
const JSPrincipals* trusted = rt->trustedPrincipals();
if (compSpec == JS::CompartmentSpecifier::NewCompartmentInSystemZone ||
(principals && principals == trusted)) {
kind = Zone::SystemZone;
}
zoneHolder = MakeUnique<Zone>(cx->runtime(), kind);
if (!zoneHolder || !zoneHolder->init()) {
ReportOutOfMemory(cx);
return nullptr;
}
zone = zoneHolder.get();
}
bool invisibleToDebugger = options.creationOptions().invisibleToDebugger();
if (comp) {
// Debugger visibility is per-compartment, not per-realm, so make sure the
// new realm's visibility matches its compartment's.
MOZ_ASSERT(comp->invisibleToDebugger() == invisibleToDebugger);
} else {
compHolder = cx->make_unique<JS::Compartment>(zone, invisibleToDebugger);
if (!compHolder) {
return nullptr;
}
comp = compHolder.get();
}
UniquePtr<Realm> realm(cx->new_<Realm>(comp, options));
if (!realm) {
return nullptr;
}
realm->init(cx, principals);
// Make sure we don't put system and non-system realms in the same
// compartment.
if (!compHolder) {
MOZ_RELEASE_ASSERT(realm->isSystem() == IsSystemCompartment(comp));
}
AutoLockGC lock(rt);
// Reserve space in the Vectors before we start mutating them.
if (!comp->realms().reserve(comp->realms().length() + 1) ||
(compHolder &&
!zone->compartments().reserve(zone->compartments().length() + 1)) ||
(zoneHolder && !rt->gc.zones().reserve(rt->gc.zones().length() + 1))) {
ReportOutOfMemory(cx);
return nullptr;
}
// After this everything must be infallible.
comp->realms().infallibleAppend(realm.get());
if (compHolder) {
zone->compartments().infallibleAppend(compHolder.release());
}
if (zoneHolder) {
rt->gc.zones().infallibleAppend(zoneHolder.release());
// Lazily set the runtime's system zone.
if (compSpec == JS::CompartmentSpecifier::NewCompartmentInSystemZone) {
MOZ_RELEASE_ASSERT(!rt->gc.systemZone);
MOZ_ASSERT(zone->isSystemZone());
rt->gc.systemZone = zone;
}
}
return realm.release();
}
void GCRuntime::runDebugGC() {
#ifdef JS_GC_ZEAL
if (rt->mainContextFromOwnThread()->suppressGC) {
return;
}
if (hasZealMode(ZealMode::GenerationalGC)) {
return minorGC(JS::GCReason::DEBUG_GC);
}
PrepareForDebugGC(rt);
auto budget = SliceBudget::unlimited();
if (hasZealMode(ZealMode::IncrementalMultipleSlices)) {
/*
* Start with a small slice limit and double it every slice. This
* ensure that we get multiple slices, and collection runs to
* completion.
*/
if (!isIncrementalGCInProgress()) {
zealSliceBudget = zealFrequency / 2;
} else {
zealSliceBudget *= 2;
}
budget = SliceBudget(WorkBudget(zealSliceBudget));
js::gc::State initialState = incrementalState;
if (!isIncrementalGCInProgress()) {
setGCOptions(JS::GCOptions::Shrink);
}
collect(false, budget, JS::GCReason::DEBUG_GC);
/* Reset the slice size when we get to the sweep or compact phases. */
if ((initialState == State::Mark && incrementalState == State::Sweep) ||
(initialState == State::Sweep && incrementalState == State::Compact)) {
zealSliceBudget = zealFrequency / 2;
}
} else if (hasIncrementalTwoSliceZealMode()) {
// These modes trigger incremental GC that happens in two slices and the
// supplied budget is ignored by incrementalSlice.
budget = SliceBudget(WorkBudget(1));
if (!isIncrementalGCInProgress()) {
setGCOptions(JS::GCOptions::Normal);
}
collect(false, budget, JS::GCReason::DEBUG_GC);
} else if (hasZealMode(ZealMode::Compact)) {
gc(JS::GCOptions::Shrink, JS::GCReason::DEBUG_GC);
} else {
gc(JS::GCOptions::Normal, JS::GCReason::DEBUG_GC);
}
#endif
}
void GCRuntime::setFullCompartmentChecks(bool enabled) {
MOZ_ASSERT(!JS::RuntimeHeapIsMajorCollecting());
fullCompartmentChecks = enabled;
}
void GCRuntime::notifyRootsRemoved() {
rootsRemoved = true;
#ifdef JS_GC_ZEAL
/* Schedule a GC to happen "soon". */
if (hasZealMode(ZealMode::RootsChange)) {
nextScheduled = 1;
}
#endif
}
#ifdef JS_GC_ZEAL
bool GCRuntime::selectForMarking(JSObject* object) {
MOZ_ASSERT(!JS::RuntimeHeapIsMajorCollecting());
return selectedForMarking.ref().get().append(object);
}
void GCRuntime::clearSelectedForMarking() {
selectedForMarking.ref().get().clearAndFree();
}
void GCRuntime::setDeterministic(bool enabled) {
MOZ_ASSERT(!JS::RuntimeHeapIsMajorCollecting());
deterministicOnly = enabled;
}
#endif
#ifdef DEBUG
AutoAssertNoNurseryAlloc::AutoAssertNoNurseryAlloc() {
TlsContext.get()->disallowNurseryAlloc();
}
AutoAssertNoNurseryAlloc::~AutoAssertNoNurseryAlloc() {
TlsContext.get()->allowNurseryAlloc();
}
#endif // DEBUG
#ifdef JSGC_HASH_TABLE_CHECKS
void GCRuntime::checkHashTablesAfterMovingGC() {
/*
* Check that internal hash tables no longer have any pointers to things
* that have been moved.
*/
rt->geckoProfiler().checkStringsMapAfterMovingGC();
if (rt->hasJitRuntime() && rt->jitRuntime()->hasInterpreterEntryMap()) {
rt->jitRuntime()->getInterpreterEntryMap()->checkScriptsAfterMovingGC();
}
for (ZonesIter zone(this, SkipAtoms); !zone.done(); zone.next()) {
zone->checkUniqueIdTableAfterMovingGC();
zone->shapeZone().checkTablesAfterMovingGC();
zone->checkAllCrossCompartmentWrappersAfterMovingGC();
zone->checkScriptMapsAfterMovingGC();
// Note: CompactPropMaps never have a table.
JS::AutoCheckCannotGC nogc;
for (auto map = zone->cellIterUnsafe<NormalPropMap>(); !map.done();
map.next()) {
if (PropMapTable* table = map->asLinked()->maybeTable(nogc)) {
table->checkAfterMovingGC();
}
}
for (auto map = zone->cellIterUnsafe<DictionaryPropMap>(); !map.done();
map.next()) {
if (PropMapTable* table = map->asLinked()->maybeTable(nogc)) {
table->checkAfterMovingGC();
}
}
}
for (CompartmentsIter c(this); !c.done(); c.next()) {
for (RealmsInCompartmentIter r(c); !r.done(); r.next()) {
r->dtoaCache.checkCacheAfterMovingGC();
if (r->debugEnvs()) {
r->debugEnvs()->checkHashTablesAfterMovingGC();
}
}
}
}
#endif
#ifdef DEBUG
bool GCRuntime::hasZone(Zone* target) {
for (AllZonesIter zone(this); !zone.done(); zone.next()) {
if (zone == target) {
return true;
}
}
return false;
}
#endif
void AutoAssertEmptyNursery::checkCondition(JSContext* cx) {
if (!noAlloc) {
noAlloc.emplace();
}
this->cx = cx;
MOZ_ASSERT(cx->nursery().isEmpty());
}
AutoEmptyNursery::AutoEmptyNursery(JSContext* cx) {
MOZ_ASSERT(!cx->suppressGC);
cx->runtime()->gc.stats().suspendPhases();
cx->runtime()->gc.evictNursery(JS::GCReason::EVICT_NURSERY);
cx->runtime()->gc.stats().resumePhases();
checkCondition(cx);
}
#ifdef DEBUG
namespace js {
// We don't want jsfriendapi.h to depend on GenericPrinter,
// so these functions are declared directly in the cpp.
extern JS_PUBLIC_API void DumpString(JSString* str, js::GenericPrinter& out);
} // namespace js
void js::gc::Cell::dump(js::GenericPrinter& out) const {
switch (getTraceKind()) {
case JS::TraceKind::Object:
reinterpret_cast<const JSObject*>(this)->dump(out);
break;
case JS::TraceKind::String:
js::DumpString(reinterpret_cast<JSString*>(const_cast<Cell*>(this)), out);
break;
case JS::TraceKind::Shape:
reinterpret_cast<const Shape*>(this)->dump(out);
break;
default:
out.printf("%s(%p)\n", JS::GCTraceKindToAscii(getTraceKind()),
(void*)this);
}
}
// For use in a debugger.
void js::gc::Cell::dump() const {
js::Fprinter out(stderr);
dump(out);
}
#endif
JS_PUBLIC_API bool js::gc::detail::CanCheckGrayBits(const TenuredCell* cell) {
// We do not check the gray marking state of cells in the following cases:
//
// 1) When OOM has caused us to clear the gcGrayBitsValid_ flag.
//
// 2) When we are in an incremental GC and examine a cell that is in a zone
// that is not being collected. Gray targets of CCWs that are marked black
// by a barrier will eventually be marked black in a later GC slice.
//
// 3) When mark bits are being cleared concurrently by a helper thread.
MOZ_ASSERT(cell);
auto* runtime = cell->runtimeFromAnyThread();
MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime));
if (!runtime->gc.areGrayBitsValid()) {
return false;
}
JS::Zone* zone = cell->zone();
if (runtime->gc.isIncrementalGCInProgress() && !zone->wasGCStarted()) {
return false;
}
return !zone->isGCPreparing();
}
JS_PUBLIC_API bool js::gc::detail::CellIsMarkedGrayIfKnown(
const TenuredCell* cell) {
MOZ_ASSERT_IF(cell->isPermanentAndMayBeShared(), cell->isMarkedBlack());
if (!cell->isMarkedGray()) {
return false;
}
return CanCheckGrayBits(cell);
}
#ifdef DEBUG
JS_PUBLIC_API void js::gc::detail::AssertCellIsNotGray(const Cell* cell) {
if (!cell->isTenured()) {
return;
}
// Check that a cell is not marked gray.
//
// Since this is a debug-only check, take account of the eventual mark state
// of cells that will be marked black by the next GC slice in an incremental
// GC. For performance reasons we don't do this in CellIsMarkedGrayIfKnown.
const auto* tc = &cell->asTenured();
if (!tc->isMarkedGray() || !CanCheckGrayBits(tc)) {
return;
}
// TODO: I'd like to AssertHeapIsIdle() here, but this ends up getting
// called during GC and while iterating the heap for memory reporting.
MOZ_ASSERT(!JS::RuntimeHeapIsCycleCollecting());
if (tc->zone()->isGCMarkingBlackAndGray()) {
// We are doing gray marking in the cell's zone. Even if the cell is
// currently marked gray it may eventually be marked black. Delay checking
// non-black cells until we finish gray marking.
if (!tc->isMarkedBlack()) {
JSRuntime* rt = tc->zone()->runtimeFromMainThread();
AutoEnterOOMUnsafeRegion oomUnsafe;
if (!rt->gc.cellsToAssertNotGray.ref().append(cell)) {
oomUnsafe.crash("Can't append to delayed gray checks list");
}
}
return;
}
MOZ_ASSERT(!tc->isMarkedGray());
}
extern JS_PUBLIC_API bool js::gc::detail::ObjectIsMarkedBlack(
const JSObject* obj) {
return obj->isMarkedBlack();
}
#endif
js::gc::ClearEdgesTracer::ClearEdgesTracer(JSRuntime* rt)
: GenericTracerImpl(rt, JS::TracerKind::ClearEdges,
JS::WeakMapTraceAction::TraceKeysAndValues) {}
template <typename T>
void js::gc::ClearEdgesTracer::onEdge(T** thingp, const char* name) {
// We don't handle removing pointers to nursery edges from the store buffer
// with this tracer. Check that this doesn't happen.
T* thing = *thingp;
MOZ_ASSERT(!IsInsideNursery(thing));
// Fire the pre-barrier since we're removing an edge from the graph.
InternalBarrierMethods<T*>::preBarrier(thing);
*thingp = nullptr;
}
void GCRuntime::setPerformanceHint(PerformanceHint hint) {
if (hint == PerformanceHint::InPageLoad) {
inPageLoadCount++;
} else {
MOZ_ASSERT(inPageLoadCount);
inPageLoadCount--;
}
}