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fune/dom/base/CCGCScheduler.cpp
Nika Layzell 852d02ec16 Bug 1809753 - Part 3: Replace all callers of GetCurrentEventTarget with GetCurrentSerialEventTarget, r=mccr8,necko-reviewers,valentin 
This only changes the behaviour when called with a TaskQueue or other type
using SerialEventTargetGuard on the stack. They are being switched over as the
existing GetCurrentEventTarget method is being removed, as it is somewhat
confusing, and poorly documented.

Callers which need to get the current thread even when on a threadpool or
behind a TaskQueue were switched to GetCurrentEventTarget in the previous part.

Differential Revision: https://phabricator.services.mozilla.com/D166607
2023-01-16 23:14:11 +00:00

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/* 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
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "CCGCScheduler.h"
#include "js/GCAPI.h"
#include "mozilla/StaticPrefs_javascript.h"
#include "mozilla/CycleCollectedJSRuntime.h"
#include "mozilla/ProfilerMarkers.h"
#include "mozilla/dom/ScriptSettings.h"
#include "mozilla/PerfStats.h"
#include "nsRefreshDriver.h"
/*
* GC Scheduling from Firefox
* ==========================
*
* See also GC Scheduling from SpiderMonkey's perspective here:
* https://searchfox.org/mozilla-central/source/js/src/gc/Scheduling.h
*
* From Firefox's perspective GCs can start in 5 different ways:
*
* * The JS engine just starts doing a GC for its own reasons (see above).
* Firefox finds out about these via a callback in nsJSEnvironment.cpp
* * PokeGC()
* * PokeFullGC()
* * PokeShrinkingGC()
* * memory-pressure GCs (via a listener in nsJSEnvironment.cpp).
*
* PokeGC
* ------
*
* void CCGCScheduler::PokeGC(JS::GCReason aReason, JSObject* aObj,
* TimeDuration aDelay)
*
* PokeGC provides a way for callers to say "Hey, there may be some memory
* associated with this object (via Zone) you can collect." PokeGC will:
* * add the zone to a set,
* * set flags including what kind of GC to run (SetWantMajorGC),
* * then creates the mGCRunner with a short delay.
*
* The delay can allow other calls to PokeGC to add their zones so they can
* be collected together.
*
* See below for what happens when mGCRunner fires.
*
* PokeFullGC
* ----------
*
* void CCGCScheduler::PokeFullGC()
*
* PokeFullGC will create a timer that will initiate a "full" (all zones)
* collection. This is usually used after a regular collection if a full GC
* seems like a good idea (to collect inter-zone references).
*
* When the timer fires it will:
* * set flags (SetWantMajorGC),
* * start the mGCRunner with zero delay.
*
* See below for when mGCRunner fires.
*
* PokeShrinkingGC
* ---------------
*
* void CCGCScheduler::PokeShrinkingGC()
*
* PokeShrinkingGC is called when Firefox's user is inactive.
* Like PokeFullGC, PokeShrinkingGC uses a timer, but the timeout is longer
* which should prevent the ShrinkingGC from starting if the user only
* glances away for a brief time. When the timer fires it will:
*
* * set flags (SetWantMajorGC),
* * create the mGCRunner.
*
* There is a check if the user is still inactive in GCRunnerFired), if the
* user has become active the shrinking GC is canceled and either a regular
* GC (if requested, see mWantAtLeastRegularGC) or no GC is run.
*
* When mGCRunner fires
* --------------------
*
* When mGCRunner fires it calls GCRunnerFired. This starts in the
* WaitToMajorGC state:
*
* * If this is a parent process it jumps to the next state
* * If this is a content process it will ask the parent if now is a good
* time to do a GC. (MayGCNow)
* * kill the mGCRunner
* * Exit
*
* Meanwhile the parent process will queue GC requests so that not too many
* are running in parallel overwhelming the CPU cores (see
* IdleSchedulerParent).
*
* When the promise from MayGCNow is resolved it will set some
* state (NoteReadyForMajorGC) and restore the mGCRunner.
*
* When the mGCRunner runs a second time (or this is the parent process and
* which jumped over the above logic. It will be in the StartMajorGC state.
* It will initiate the GC for real, usually. If it's a shrinking GC and the
* user is now active again it may abort. See GCRunnerFiredDoGC().
*
* The runner will then run the first slice of the garbage collection.
* Later slices are also run by the runner, the final slice kills the runner
* from the GC callback in nsJSEnvironment.cpp.
*
* There is additional logic in the code to handle concurrent requests of
* various kinds.
*/
namespace geckoprofiler::markers {
struct CCIntervalMarker {
static constexpr mozilla::Span<const char> MarkerTypeName() {
return mozilla::MakeStringSpan("CC");
}
static void StreamJSONMarkerData(
mozilla::baseprofiler::SpliceableJSONWriter& aWriter, bool aIsStart,
const mozilla::ProfilerString8View& aReason,
uint32_t aForgetSkippableBeforeCC, uint32_t aSuspectedAtCCStart,
uint32_t aRemovedPurples, const mozilla::CycleCollectorResults& aResults,
mozilla::TimeDuration aMaxSliceTime) {
if (aIsStart) {
aWriter.StringProperty("mReason", aReason);
aWriter.IntProperty("mSuspected", aSuspectedAtCCStart);
aWriter.IntProperty("mForgetSkippable", aForgetSkippableBeforeCC);
aWriter.IntProperty("mRemovedPurples", aRemovedPurples);
} else {
aWriter.TimeDoubleMsProperty("mMaxSliceTime",
aMaxSliceTime.ToMilliseconds());
aWriter.IntProperty("mSlices", aResults.mNumSlices);
aWriter.BoolProperty("mAnyManual", aResults.mAnyManual);
aWriter.BoolProperty("mForcedGC", aResults.mForcedGC);
aWriter.BoolProperty("mMergedZones", aResults.mMergedZones);
aWriter.IntProperty("mVisitedRefCounted", aResults.mVisitedRefCounted);
aWriter.IntProperty("mVisitedGCed", aResults.mVisitedGCed);
aWriter.IntProperty("mFreedRefCounted", aResults.mFreedRefCounted);
aWriter.IntProperty("mFreedGCed", aResults.mFreedGCed);
aWriter.IntProperty("mFreedJSZones", aResults.mFreedJSZones);
}
}
static mozilla::MarkerSchema MarkerTypeDisplay() {
using MS = mozilla::MarkerSchema;
MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable,
MS::Location::TimelineMemory};
schema.AddStaticLabelValue(
"Description",
"Summary data for the core part of a cycle collection, possibly "
"encompassing a set of incremental slices. The main thread is not "
"blocked for the entire major CC interval, only for the individual "
"slices.");
schema.AddKeyLabelFormatSearchable("mReason", "Reason", MS::Format::String,
MS::Searchable::Searchable);
schema.AddKeyLabelFormat("mMaxSliceTime", "Max Slice Time",
MS::Format::Duration);
schema.AddKeyLabelFormat("mSuspected", "Suspected Objects",
MS::Format::Integer);
schema.AddKeyLabelFormat("mSlices", "Number of Slices",
MS::Format::Integer);
schema.AddKeyLabelFormat("mAnyManual", "Manually Triggered",
MS::Format::Integer);
schema.AddKeyLabelFormat("mForcedGC", "GC Forced", MS::Format::Integer);
schema.AddKeyLabelFormat("mMergedZones", "Zones Merged",
MS::Format::Integer);
schema.AddKeyLabelFormat("mForgetSkippable", "Forget Skippables",
MS::Format::Integer);
schema.AddKeyLabelFormat("mVisitedRefCounted", "Refcounted Objects Visited",
MS::Format::Integer);
schema.AddKeyLabelFormat("mVisitedGCed", "GC Objects Visited",
MS::Format::Integer);
schema.AddKeyLabelFormat("mFreedRefCounted", "Refcounted Objects Freed",
MS::Format::Integer);
schema.AddKeyLabelFormat("mFreedGCed", "GC Objects Freed",
MS::Format::Integer);
schema.AddKeyLabelFormat("mCollectedGCZones", "JS Zones Freed",
MS::Format::Integer);
schema.AddKeyLabelFormat("mRemovedPurples",
"Objects Removed From Purple Buffer",
MS::Format::Integer);
return schema;
}
};
} // namespace geckoprofiler::markers
namespace mozilla {
void CCGCScheduler::NoteGCBegin(JS::GCReason aReason) {
// Treat all GC as incremental here; non-incremental GC will just appear to
// be one slice.
mInIncrementalGC = true;
mReadyForMajorGC = !mAskParentBeforeMajorGC;
// Tell the parent process that we've started a GC (it might not know if
// we hit a threshold in the JS engine).
using mozilla::ipc::IdleSchedulerChild;
IdleSchedulerChild* child = IdleSchedulerChild::GetMainThreadIdleScheduler();
if (child) {
child->StartedGC();
}
// The reason might have come from mMajorReason, mEagerMajorGCReason, or
// in the case of an internally-generated GC, it might come from the
// internal logic (and be passed in here). It's easier to manage a single
// reason state variable, so merge all sources into mMajorGCReason.
MOZ_ASSERT(aReason != JS::GCReason::NO_REASON);
mMajorGCReason = aReason;
mEagerMajorGCReason = JS::GCReason::NO_REASON;
}
void CCGCScheduler::NoteGCEnd() {
mMajorGCReason = JS::GCReason::NO_REASON;
mEagerMajorGCReason = JS::GCReason::NO_REASON;
mEagerMinorGCReason = JS::GCReason::NO_REASON;
mInIncrementalGC = false;
mCCBlockStart = TimeStamp();
mReadyForMajorGC = !mAskParentBeforeMajorGC;
mWantAtLeastRegularGC = false;
mNeedsFullCC = CCReason::GC_FINISHED;
mHasRunGC = true;
mIsCompactingOnUserInactive = false;
mCleanupsSinceLastGC = 0;
mCCollectedWaitingForGC = 0;
mCCollectedZonesWaitingForGC = 0;
mLikelyShortLivingObjectsNeedingGC = 0;
using mozilla::ipc::IdleSchedulerChild;
IdleSchedulerChild* child = IdleSchedulerChild::GetMainThreadIdleScheduler();
if (child) {
child->DoneGC();
}
}
void CCGCScheduler::NoteGCSliceEnd(TimeStamp aStart, TimeStamp aEnd) {
if (mMajorGCReason == JS::GCReason::NO_REASON) {
// Internally-triggered GCs do not wait for the parent's permission to
// proceed. This flag won't be checked during an incremental GC anyway,
// but it better reflects reality.
mReadyForMajorGC = true;
}
// Subsequent slices should be INTER_SLICE_GC unless they are triggered by
// something else that provides its own reason.
mMajorGCReason = JS::GCReason::INTER_SLICE_GC;
MOZ_ASSERT(aEnd >= aStart);
TimeDuration sliceDuration = aEnd - aStart;
PerfStats::RecordMeasurement(PerfStats::Metric::MajorGC, sliceDuration);
// Compute how much GC time was spent in predicted-to-be-idle time. In the
// unlikely event that the slice started after the deadline had already
// passed, treat the entire slice as non-idle.
TimeDuration nonIdleDuration;
bool startedIdle = mTriggeredGCDeadline.isSome() &&
!mTriggeredGCDeadline->IsNull() &&
*mTriggeredGCDeadline > aStart;
if (!startedIdle) {
nonIdleDuration = sliceDuration;
} else {
if (*mTriggeredGCDeadline < aEnd) {
// Overran the idle deadline.
nonIdleDuration = aEnd - *mTriggeredGCDeadline;
}
}
PerfStats::RecordMeasurement(PerfStats::Metric::NonIdleMajorGC,
nonIdleDuration);
// Note the GC_SLICE_DURING_IDLE previously had a different definition: it was
// a histogram of percentages of externally-triggered slices. It is now a
// histogram of percentages of all slices. That means that now you might have
// a 4ms internal slice (0% during idle) followed by a 16ms external slice
// (15ms during idle), whereas before this would show up as a single record of
// a single slice with 75% of its time during idle (15 of 20ms).
TimeDuration idleDuration = sliceDuration - nonIdleDuration;
uint32_t percent =
uint32_t(idleDuration.ToSeconds() / sliceDuration.ToSeconds() * 100);
Telemetry::Accumulate(Telemetry::GC_SLICE_DURING_IDLE, percent);
mTriggeredGCDeadline.reset();
}
void CCGCScheduler::NoteCCBegin(CCReason aReason, TimeStamp aWhen,
uint32_t aNumForgetSkippables,
uint32_t aSuspected, uint32_t aRemovedPurples) {
CycleCollectorResults ignoredResults;
PROFILER_MARKER(
"CC", GCCC, MarkerOptions(MarkerTiming::IntervalStart(aWhen)),
CCIntervalMarker,
/* aIsStart */ true,
ProfilerString8View::WrapNullTerminatedString(CCReasonToString(aReason)),
aNumForgetSkippables, aSuspected, aRemovedPurples, ignoredResults,
TimeDuration());
mIsCollectingCycles = true;
}
void CCGCScheduler::NoteCCEnd(const CycleCollectorResults& aResults,
TimeStamp aWhen,
mozilla::TimeDuration aMaxSliceTime) {
mCCollectedWaitingForGC += aResults.mFreedGCed;
mCCollectedZonesWaitingForGC += aResults.mFreedJSZones;
PROFILER_MARKER("CC", GCCC, MarkerOptions(MarkerTiming::IntervalEnd(aWhen)),
CCIntervalMarker, /* aIsStart */ false, nullptr, 0, 0, 0,
aResults, aMaxSliceTime);
mIsCollectingCycles = false;
mLastCCEndTime = aWhen;
mNeedsFullCC = CCReason::NO_REASON;
}
void CCGCScheduler::NoteWontGC() {
mReadyForMajorGC = !mAskParentBeforeMajorGC;
mMajorGCReason = JS::GCReason::NO_REASON;
mEagerMajorGCReason = JS::GCReason::NO_REASON;
mWantAtLeastRegularGC = false;
// Don't clear the WantFullGC state, we will do a full GC the next time a
// GC happens for any other reason.
}
bool CCGCScheduler::GCRunnerFired(TimeStamp aDeadline) {
MOZ_ASSERT(!mDidShutdown, "GCRunner still alive during shutdown");
GCRunnerStep step = GetNextGCRunnerAction(aDeadline);
switch (step.mAction) {
case GCRunnerAction::None:
KillGCRunner();
return false;
case GCRunnerAction::MinorGC:
JS::MaybeRunNurseryCollection(CycleCollectedJSRuntime::Get()->Runtime(),
step.mReason);
NoteMinorGCEnd();
return HasMoreIdleGCRunnerWork();
case GCRunnerAction::WaitToMajorGC: {
MOZ_ASSERT(!mHaveAskedParent, "GCRunner alive after asking the parent");
RefPtr<CCGCScheduler::MayGCPromise> mbPromise =
CCGCScheduler::MayGCNow(step.mReason);
if (!mbPromise) {
// We can GC now.
break;
}
mHaveAskedParent = true;
KillGCRunner();
mbPromise->Then(
GetMainThreadSerialEventTarget(), __func__,
[this](bool aMayGC) {
mHaveAskedParent = false;
if (aMayGC) {
if (!NoteReadyForMajorGC()) {
// Another GC started and maybe completed while waiting.
return;
}
// Recreate the GC runner with a 0 delay. The new runner will
// continue in idle time.
KillGCRunner();
EnsureGCRunner(0);
} else if (!InIncrementalGC()) {
// We should kill the GC runner since we're done with it, but
// only if there's no incremental GC.
KillGCRunner();
NoteWontGC();
}
},
[this](mozilla::ipc::ResponseRejectReason r) {
mHaveAskedParent = false;
if (!InIncrementalGC()) {
KillGCRunner();
NoteWontGC();
}
});
return true;
}
case GCRunnerAction::StartMajorGC:
case GCRunnerAction::GCSlice:
break;
}
return GCRunnerFiredDoGC(aDeadline, step);
}
bool CCGCScheduler::GCRunnerFiredDoGC(TimeStamp aDeadline,
const GCRunnerStep& aStep) {
// Run a GC slice, possibly the first one of a major GC.
nsJSContext::IsShrinking is_shrinking = nsJSContext::NonShrinkingGC;
if (!InIncrementalGC() && aStep.mReason == JS::GCReason::USER_INACTIVE) {
bool do_gc = mWantAtLeastRegularGC;
if (!mUserIsActive) {
if (!nsRefreshDriver::IsRegularRateTimerTicking()) {
mIsCompactingOnUserInactive = true;
is_shrinking = nsJSContext::ShrinkingGC;
do_gc = true;
} else {
// Poke again to restart the timer.
PokeShrinkingGC();
}
}
if (!do_gc) {
using mozilla::ipc::IdleSchedulerChild;
IdleSchedulerChild* child =
IdleSchedulerChild::GetMainThreadIdleScheduler();
if (child) {
child->DoneGC();
}
NoteWontGC();
KillGCRunner();
return true;
}
}
// Note that we are triggering the following GC slice and recording whether
// it started in idle time, for use in the callback at the end of the slice.
mTriggeredGCDeadline = Some(aDeadline);
MOZ_ASSERT(mActiveIntersliceGCBudget);
TimeStamp startTimeStamp = TimeStamp::Now();
js::SliceBudget budget = ComputeInterSliceGCBudget(aDeadline, startTimeStamp);
nsJSContext::RunIncrementalGCSlice(aStep.mReason, is_shrinking, budget);
// If the GC doesn't have any more work to do on the foreground thread (and
// e.g. is waiting for background sweeping to finish) then return false to
// make IdleTaskRunner postpone the next call a bit.
JSContext* cx = dom::danger::GetJSContext();
return JS::IncrementalGCHasForegroundWork(cx);
}
RefPtr<CCGCScheduler::MayGCPromise> CCGCScheduler::MayGCNow(
JS::GCReason reason) {
using namespace mozilla::ipc;
// We ask the parent if we should GC for GCs that aren't too timely,
// with the exception of MEM_PRESSURE, in that case we ask the parent
// because GCing on too many processes at the same time when under
// memory pressure could be a very bad experience for the user.
switch (reason) {
case JS::GCReason::PAGE_HIDE:
case JS::GCReason::MEM_PRESSURE:
case JS::GCReason::USER_INACTIVE:
case JS::GCReason::FULL_GC_TIMER:
case JS::GCReason::CC_FINISHED: {
if (XRE_IsContentProcess()) {
IdleSchedulerChild* child =
IdleSchedulerChild::GetMainThreadIdleScheduler();
if (child) {
return child->MayGCNow();
}
}
// The parent process doesn't ask IdleSchedulerParent if it can GC.
break;
}
default:
break;
}
// We use synchronous task dispatch here to avoid a trip through the event
// loop if we're on the parent process or it's a GC reason that does not
// require permission to GC.
RefPtr<MayGCPromise::Private> p = MakeRefPtr<MayGCPromise::Private>(__func__);
p->UseSynchronousTaskDispatch(__func__);
p->Resolve(true, __func__);
return p;
}
void CCGCScheduler::RunNextCollectorTimer(JS::GCReason aReason,
mozilla::TimeStamp aDeadline) {
if (mDidShutdown) {
return;
}
// When we're in an incremental GC, we should always have an sGCRunner, so do
// not check CC timers. The CC timers won't do anything during a GC.
MOZ_ASSERT_IF(InIncrementalGC(), mGCRunner);
RefPtr<IdleTaskRunner> runner;
if (mGCRunner) {
SetWantMajorGC(aReason);
runner = mGCRunner;
} else if (mCCRunner) {
runner = mCCRunner;
}
if (runner) {
runner->SetIdleDeadline(aDeadline);
runner->Run();
}
}
void CCGCScheduler::PokeShrinkingGC() {
if (mShrinkingGCTimer || mDidShutdown) {
return;
}
NS_NewTimerWithFuncCallback(
&mShrinkingGCTimer,
[](nsITimer* aTimer, void* aClosure) {
CCGCScheduler* s = static_cast<CCGCScheduler*>(aClosure);
s->KillShrinkingGCTimer();
if (!s->mUserIsActive) {
if (!nsRefreshDriver::IsRegularRateTimerTicking()) {
s->SetWantMajorGC(JS::GCReason::USER_INACTIVE);
if (!s->mHaveAskedParent) {
s->EnsureGCRunner(0);
}
} else {
s->PokeShrinkingGC();
}
}
},
this, StaticPrefs::javascript_options_compact_on_user_inactive_delay(),
nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY, "ShrinkingGCTimerFired");
}
void CCGCScheduler::PokeFullGC() {
if (!mFullGCTimer && !mDidShutdown) {
NS_NewTimerWithFuncCallback(
&mFullGCTimer,
[](nsITimer* aTimer, void* aClosure) {
CCGCScheduler* s = static_cast<CCGCScheduler*>(aClosure);
s->KillFullGCTimer();
// Even if the GC is denied by the parent process, because we've
// set that we want a full GC we will get one eventually.
s->SetNeedsFullGC();
s->SetWantMajorGC(JS::GCReason::FULL_GC_TIMER);
if (!s->mHaveAskedParent) {
s->EnsureGCRunner(0);
}
},
this, StaticPrefs::javascript_options_gc_delay_full(),
nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY, "FullGCTimerFired");
}
}
void CCGCScheduler::PokeGC(JS::GCReason aReason, JSObject* aObj,
TimeDuration aDelay) {
MOZ_ASSERT(aReason != JS::GCReason::NO_REASON);
MOZ_ASSERT(aReason != JS::GCReason::EAGER_NURSERY_COLLECTION);
if (mDidShutdown) {
return;
}
// If a post-CC GC was pending, then we'll make sure one is happening.
mNeedsGCAfterCC = false;
if (aObj) {
JS::Zone* zone = JS::GetObjectZone(aObj);
CycleCollectedJSRuntime::Get()->AddZoneWaitingForGC(zone);
} else if (aReason != JS::GCReason::CC_FINISHED) {
SetNeedsFullGC();
}
if (mGCRunner || mHaveAskedParent) {
// There's already a GC runner, or there will be, so just return.
return;
}
SetWantMajorGC(aReason);
if (mCCRunner) {
// Make sure CC is called regardless of the size of the purple buffer, and
// GC after it.
EnsureCCThenGC(CCReason::GC_WAITING);
return;
}
// Wait for javascript.options.gc_delay (or delay_first) then start
// looking for idle time to run the initial GC slice.
static bool first = true;
TimeDuration delay =
aDelay ? aDelay
: TimeDuration::FromMilliseconds(
first ? StaticPrefs::javascript_options_gc_delay_first()
: StaticPrefs::javascript_options_gc_delay());
first = false;
EnsureGCRunner(delay);
}
void CCGCScheduler::PokeMinorGC(JS::GCReason aReason) {
MOZ_ASSERT(aReason != JS::GCReason::NO_REASON);
if (mDidShutdown) {
return;
}
SetWantEagerMinorGC(aReason);
if (mGCRunner || mHaveAskedParent || mCCRunner) {
// There's already a runner, or there will be, so just return.
return;
}
// Immediately start looking for idle time to run the minor GC.
EnsureGCRunner(0);
}
void CCGCScheduler::EnsureGCRunner(TimeDuration aDelay) {
if (mGCRunner) {
return;
}
TimeDuration minimumBudget = nsRefreshDriver::IsInHighRateMode()
? TimeDuration::FromMilliseconds(1)
: mActiveIntersliceGCBudget;
// Wait at most the interslice GC delay before forcing a run.
mGCRunner = IdleTaskRunner::Create(
[this](TimeStamp aDeadline) { return GCRunnerFired(aDeadline); },
"CCGCScheduler::EnsureGCRunner", aDelay,
TimeDuration::FromMilliseconds(
StaticPrefs::javascript_options_gc_delay_interslice()),
minimumBudget, true, [this] { return mDidShutdown; },
[this](uint32_t) {
PROFILER_MARKER_UNTYPED("GC Interrupt", GCCC);
mInterruptRequested = true;
});
}
// nsJSEnvironmentObserver observes the user-interaction-inactive notifications
// and triggers a shrinking a garbage collection if the user is still inactive
// after NS_SHRINKING_GC_DELAY ms later, if the appropriate pref is set.
void CCGCScheduler::UserIsInactive() {
mUserIsActive = false;
if (StaticPrefs::javascript_options_compact_on_user_inactive()) {
PokeShrinkingGC();
}
}
void CCGCScheduler::UserIsActive() {
mUserIsActive = true;
KillShrinkingGCTimer();
if (mIsCompactingOnUserInactive) {
mozilla::dom::AutoJSAPI jsapi;
jsapi.Init();
JS::AbortIncrementalGC(jsapi.cx());
}
MOZ_ASSERT(!mIsCompactingOnUserInactive);
}
void CCGCScheduler::KillShrinkingGCTimer() {
if (mShrinkingGCTimer) {
mShrinkingGCTimer->Cancel();
NS_RELEASE(mShrinkingGCTimer);
}
}
void CCGCScheduler::KillFullGCTimer() {
if (mFullGCTimer) {
mFullGCTimer->Cancel();
NS_RELEASE(mFullGCTimer);
}
}
void CCGCScheduler::KillGCRunner() {
// If we're in an incremental GC then killing the timer is only okay if
// we're shutting down.
MOZ_ASSERT(!(InIncrementalGC() && !mDidShutdown));
if (mGCRunner) {
mGCRunner->Cancel();
mGCRunner = nullptr;
}
}
void CCGCScheduler::EnsureCCRunner(TimeDuration aDelay, TimeDuration aBudget) {
MOZ_ASSERT(!mDidShutdown);
TimeDuration minimumBudget = nsRefreshDriver::IsInHighRateMode()
? TimeDuration::FromMilliseconds(1)
: aBudget;
if (!mCCRunner) {
mCCRunner = IdleTaskRunner::Create(
CCRunnerFired, "EnsureCCRunner::CCRunnerFired", 0, aDelay,
minimumBudget, true, [this] { return mDidShutdown; });
} else {
mCCRunner->SetMinimumUsefulBudget(minimumBudget.ToMilliseconds());
nsIEventTarget* target = mozilla::GetCurrentSerialEventTarget();
if (target) {
mCCRunner->SetTimer(aDelay, target);
}
}
}
void CCGCScheduler::MaybePokeCC(TimeStamp aNow, uint32_t aSuspectedCCObjects) {
if (mCCRunner || mDidShutdown) {
return;
}
CCReason reason = ShouldScheduleCC(aNow, aSuspectedCCObjects);
if (reason != CCReason::NO_REASON) {
// We can kill some objects before running forgetSkippable.
nsCycleCollector_dispatchDeferredDeletion();
if (!mCCRunner) {
InitCCRunnerStateMachine(CCRunnerState::ReducePurple, reason);
}
EnsureCCRunner(kCCSkippableDelay, kForgetSkippableSliceDuration);
}
}
void CCGCScheduler::KillCCRunner() {
UnblockCC();
DeactivateCCRunner();
if (mCCRunner) {
mCCRunner->Cancel();
mCCRunner = nullptr;
}
}
void CCGCScheduler::KillAllTimersAndRunners() {
KillShrinkingGCTimer();
KillCCRunner();
KillFullGCTimer();
KillGCRunner();
}
js::SliceBudget CCGCScheduler::ComputeCCSliceBudget(
TimeStamp aDeadline, TimeStamp aCCBeginTime, TimeStamp aPrevSliceEndTime,
TimeStamp aNow, bool* aPreferShorterSlices) const {
*aPreferShorterSlices =
aDeadline.IsNull() || (aDeadline - aNow) < kICCSliceBudget;
TimeDuration baseBudget =
aDeadline.IsNull() ? kICCSliceBudget : aDeadline - aNow;
if (aPrevSliceEndTime.IsNull()) {
// The first slice gets the standard slice time.
return js::SliceBudget(js::TimeBudget(baseBudget));
}
// Only run a limited slice if we're within the max running time.
MOZ_ASSERT(aNow >= aCCBeginTime);
TimeDuration runningTime = aNow - aCCBeginTime;
if (runningTime >= kMaxICCDuration) {
return js::SliceBudget::unlimited();
}
const TimeDuration maxSlice =
TimeDuration::FromMilliseconds(MainThreadIdlePeriod::GetLongIdlePeriod());
// Try to make up for a delay in running this slice.
MOZ_ASSERT(aNow >= aPrevSliceEndTime);
double sliceDelayMultiplier =
(aNow - aPrevSliceEndTime) / kICCIntersliceDelay;
TimeDuration delaySliceBudget =
std::min(baseBudget.MultDouble(sliceDelayMultiplier), maxSlice);
// Increase slice budgets up to |maxSlice| as we approach
// half way through the ICC, to avoid large sync CCs.
double percentToHalfDone =
std::min(2.0 * (runningTime / kMaxICCDuration), 1.0);
TimeDuration laterSliceBudget = maxSlice.MultDouble(percentToHalfDone);
// Note: We may have already overshot the deadline, in which case
// baseBudget will be negative and we will end up returning
// laterSliceBudget.
return js::SliceBudget(js::TimeBudget(
std::max({delaySliceBudget, laterSliceBudget, baseBudget})));
}
js::SliceBudget CCGCScheduler::ComputeInterSliceGCBudget(TimeStamp aDeadline,
TimeStamp aNow) {
// We use longer budgets when the CC has been locked out but the CC has
// tried to run since that means we may have a significant amount of
// garbage to collect and it's better to GC in several longer slices than
// in a very long one.
TimeDuration budget =
aDeadline.IsNull() ? mActiveIntersliceGCBudget * 2 : aDeadline - aNow;
if (!mCCBlockStart) {
return CreateGCSliceBudget(budget, !aDeadline.IsNull(), false);
}
TimeDuration blockedTime = aNow - mCCBlockStart;
TimeDuration maxSliceGCBudget = mActiveIntersliceGCBudget * 10;
double percentOfBlockedTime =
std::min(blockedTime / kMaxCCLockedoutTime, 1.0);
TimeDuration extendedBudget =
maxSliceGCBudget.MultDouble(percentOfBlockedTime);
if (budget >= extendedBudget) {
return CreateGCSliceBudget(budget, !aDeadline.IsNull(), false);
}
// If the budget is being extended, do not allow it to be interrupted.
auto result = js::SliceBudget(js::TimeBudget(extendedBudget), nullptr);
result.idle = !aDeadline.IsNull();
result.extended = true;
return result;
}
CCReason CCGCScheduler::ShouldScheduleCC(TimeStamp aNow,
uint32_t aSuspectedCCObjects) const {
if (!mHasRunGC) {
return CCReason::NO_REASON;
}
// Don't run consecutive CCs too often.
if (mCleanupsSinceLastGC && !mLastCCEndTime.IsNull()) {
if (aNow - mLastCCEndTime < kCCDelay) {
return CCReason::NO_REASON;
}
}
// If GC hasn't run recently and forget skippable only cycle was run,
// don't start a new cycle too soon.
if ((mCleanupsSinceLastGC > kMajorForgetSkippableCalls) &&
!mLastForgetSkippableCycleEndTime.IsNull()) {
if (aNow - mLastForgetSkippableCycleEndTime <
kTimeBetweenForgetSkippableCycles) {
return CCReason::NO_REASON;
}
}
return IsCCNeeded(aNow, aSuspectedCCObjects);
}
CCRunnerStep CCGCScheduler::AdvanceCCRunner(TimeStamp aDeadline, TimeStamp aNow,
uint32_t aSuspectedCCObjects) {
struct StateDescriptor {
// When in this state, should we first check to see if we still have
// enough reason to CC?
bool mCanAbortCC;
// If we do decide to abort the CC, should we still try to forget
// skippables one more time?
bool mTryFinalForgetSkippable;
};
// The state descriptors for Inactive and Canceled will never actually be
// used. We will never call this function while Inactive, and Canceled is
// handled specially at the beginning.
constexpr StateDescriptor stateDescriptors[] = {
{false, false}, /* CCRunnerState::Inactive */
{false, false}, /* CCRunnerState::ReducePurple */
{true, true}, /* CCRunnerState::CleanupChildless */
{true, false}, /* CCRunnerState::CleanupContentUnbinder */
{false, false}, /* CCRunnerState::CleanupDeferred */
{false, false}, /* CCRunnerState::StartCycleCollection */
{false, false}, /* CCRunnerState::CycleCollecting */
{false, false}}; /* CCRunnerState::Canceled */
static_assert(
ArrayLength(stateDescriptors) == size_t(CCRunnerState::NumStates),
"need one state descriptor per state");
const StateDescriptor& desc = stateDescriptors[int(mCCRunnerState)];
// Make sure we initialized the state machine.
MOZ_ASSERT(mCCRunnerState != CCRunnerState::Inactive);
if (mDidShutdown) {
return {CCRunnerAction::StopRunning, Yield};
}
if (mCCRunnerState == CCRunnerState::Canceled) {
// When we cancel a cycle, there may have been a final ForgetSkippable.
return {CCRunnerAction::StopRunning, Yield};
}
if (InIncrementalGC()) {
if (mCCBlockStart.IsNull()) {
BlockCC(aNow);
// If we have reached the CycleCollecting state, then ignore CC timer
// fires while incremental GC is running. (Running ICC during an IGC
// would cause us to synchronously finish the GC, which is bad.)
//
// If we have not yet started cycle collecting, then reset our state so
// that we run forgetSkippable often enough before CC. Because of reduced
// mCCDelay, forgetSkippable will be called just a few times.
//
// The kMaxCCLockedoutTime limit guarantees that we end up calling
// forgetSkippable and CycleCollectNow eventually.
if (mCCRunnerState != CCRunnerState::CycleCollecting) {
mCCRunnerState = CCRunnerState::ReducePurple;
mCCRunnerEarlyFireCount = 0;
mCCDelay = kCCDelay / int64_t(3);
}
return {CCRunnerAction::None, Yield};
}
if (GetCCBlockedTime(aNow) < kMaxCCLockedoutTime) {
return {CCRunnerAction::None, Yield};
}
// Locked out for too long, so proceed and finish the incremental GC
// synchronously.
}
// For states that aren't just continuations of previous states, check
// whether a CC is still needed (after doing various things to reduce the
// purple buffer).
if (desc.mCanAbortCC &&
IsCCNeeded(aNow, aSuspectedCCObjects) == CCReason::NO_REASON) {
// If we don't pass the threshold for wanting to cycle collect, stop now
// (after possibly doing a final ForgetSkippable).
mCCRunnerState = CCRunnerState::Canceled;
NoteForgetSkippableOnlyCycle(aNow);
// Preserve the previous code's idea of when to check whether a
// ForgetSkippable should be fired.
if (desc.mTryFinalForgetSkippable &&
ShouldForgetSkippable(aSuspectedCCObjects)) {
// The Canceled state will make us StopRunning after this action is
// performed (see conditional at top of function).
return {CCRunnerAction::ForgetSkippable, Yield, KeepChildless};
}
return {CCRunnerAction::StopRunning, Yield};
}
if (mEagerMinorGCReason != JS::GCReason::NO_REASON && !aDeadline.IsNull()) {
return {CCRunnerAction::MinorGC, Continue, mEagerMinorGCReason};
}
switch (mCCRunnerState) {
// ReducePurple: a GC ran (or we otherwise decided to try CC'ing). Wait
// for some amount of time (kCCDelay, or less if incremental GC blocked
// this CC) while firing regular ForgetSkippable actions before continuing
// on.
case CCRunnerState::ReducePurple:
++mCCRunnerEarlyFireCount;
if (IsLastEarlyCCTimer(mCCRunnerEarlyFireCount)) {
mCCRunnerState = CCRunnerState::CleanupChildless;
}
if (ShouldForgetSkippable(aSuspectedCCObjects)) {
return {CCRunnerAction::ForgetSkippable, Yield, KeepChildless};
}
if (aDeadline.IsNull()) {
return {CCRunnerAction::None, Yield};
}
// If we're called during idle time, try to find some work to do by
// advancing to the next state, effectively bypassing some possible forget
// skippable calls.
mCCRunnerState = CCRunnerState::CleanupChildless;
// Continue on to CleanupChildless, but only after checking IsCCNeeded
// again.
return {CCRunnerAction::None, Continue};
// CleanupChildless: do a stronger ForgetSkippable that removes nodes with
// no children in the cycle collector graph. This state is split into 3
// parts; the other Cleanup* actions will happen within the same callback
// (unless the ForgetSkippable shrinks the purple buffer enough for the CC
// to be skipped entirely.)
case CCRunnerState::CleanupChildless:
mCCRunnerState = CCRunnerState::CleanupContentUnbinder;
return {CCRunnerAction::ForgetSkippable, Yield, RemoveChildless};
// CleanupContentUnbinder: continuing cleanup, clear out the content
// unbinder.
case CCRunnerState::CleanupContentUnbinder:
if (aDeadline.IsNull()) {
// Non-idle (waiting) callbacks skip the rest of the cleanup, but still
// wait for another fire before the actual CC.
mCCRunnerState = CCRunnerState::StartCycleCollection;
return {CCRunnerAction::None, Yield};
}
// Running in an idle callback.
// The deadline passed, so go straight to CC in the next slice.
if (aNow >= aDeadline) {
mCCRunnerState = CCRunnerState::StartCycleCollection;
return {CCRunnerAction::None, Yield};
}
mCCRunnerState = CCRunnerState::CleanupDeferred;
return {CCRunnerAction::CleanupContentUnbinder, Continue};
// CleanupDeferred: continuing cleanup, do deferred deletion.
case CCRunnerState::CleanupDeferred:
MOZ_ASSERT(!aDeadline.IsNull(),
"Should only be in CleanupDeferred state when idle");
// Our efforts to avoid a CC have failed. Let the timer fire once more
// to trigger a CC.
mCCRunnerState = CCRunnerState::StartCycleCollection;
if (aNow >= aDeadline) {
// The deadline passed, go straight to CC in the next slice.
return {CCRunnerAction::None, Yield};
}
return {CCRunnerAction::CleanupDeferred, Yield};
// StartCycleCollection: start actually doing cycle collection slices.
case CCRunnerState::StartCycleCollection:
// We are in the final timer fire and still meet the conditions for
// triggering a CC. Let RunCycleCollectorSlice finish the current IGC if
// any, because that will allow us to include the GC time in the CC pause.
mCCRunnerState = CCRunnerState::CycleCollecting;
[[fallthrough]];
// CycleCollecting: continue running slices until done.
case CCRunnerState::CycleCollecting: {
CCRunnerStep step{CCRunnerAction::CycleCollect, Yield};
step.mParam.mCCReason = mCCReason;
mCCReason = CCReason::SLICE; // Set reason for following slices.
return step;
}
default:
MOZ_CRASH("Unexpected CCRunner state");
};
}
GCRunnerStep CCGCScheduler::GetNextGCRunnerAction(TimeStamp aDeadline) const {
if (InIncrementalGC()) {
MOZ_ASSERT(mMajorGCReason != JS::GCReason::NO_REASON);
return {GCRunnerAction::GCSlice, mMajorGCReason};
}
// Service a non-eager GC request first, even if it requires waiting.
if (mMajorGCReason != JS::GCReason::NO_REASON) {
return {mReadyForMajorGC ? GCRunnerAction::StartMajorGC
: GCRunnerAction::WaitToMajorGC,
mMajorGCReason};
}
// Now for eager requests, which are ignored unless we're idle.
if (!aDeadline.IsNull()) {
if (mEagerMajorGCReason != JS::GCReason::NO_REASON) {
return {mReadyForMajorGC ? GCRunnerAction::StartMajorGC
: GCRunnerAction::WaitToMajorGC,
mEagerMajorGCReason};
}
if (mEagerMinorGCReason != JS::GCReason::NO_REASON) {
return {GCRunnerAction::MinorGC, mEagerMinorGCReason};
}
}
return {GCRunnerAction::None, JS::GCReason::NO_REASON};
}
js::SliceBudget CCGCScheduler::ComputeForgetSkippableBudget(
TimeStamp aStartTimeStamp, TimeStamp aDeadline) {
if (mForgetSkippableFrequencyStartTime.IsNull()) {
mForgetSkippableFrequencyStartTime = aStartTimeStamp;
} else if (aStartTimeStamp - mForgetSkippableFrequencyStartTime >
kOneMinute) {
TimeStamp startPlusMinute = mForgetSkippableFrequencyStartTime + kOneMinute;
// If we had forget skippables only at the beginning of the interval, we
// still want to use the whole time, minute or more, for frequency
// calculation. mLastForgetSkippableEndTime is needed if forget skippable
// takes enough time to push the interval to be over a minute.
TimeStamp endPoint = std::max(startPlusMinute, mLastForgetSkippableEndTime);
// Duration in minutes.
double duration =
(endPoint - mForgetSkippableFrequencyStartTime).ToSeconds() / 60;
uint32_t frequencyPerMinute = uint32_t(mForgetSkippableCounter / duration);
Telemetry::Accumulate(Telemetry::FORGET_SKIPPABLE_FREQUENCY,
frequencyPerMinute);
mForgetSkippableCounter = 0;
mForgetSkippableFrequencyStartTime = aStartTimeStamp;
}
++mForgetSkippableCounter;
TimeDuration budgetTime =
aDeadline ? (aDeadline - aStartTimeStamp) : kForgetSkippableSliceDuration;
return js::SliceBudget(budgetTime);
}
} // namespace mozilla
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