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Diffstat (limited to 'dom/base/CCGCScheduler.cpp')
| -rw-r--r-- | dom/base/CCGCScheduler.cpp | 1076 |
1 files changed, 1076 insertions, 0 deletions
diff --git a/dom/base/CCGCScheduler.cpp b/dom/base/CCGCScheduler.cpp new file mode 100644 index 0000000000..260290b3db --- /dev/null +++ b/dom/base/CCGCScheduler.cpp @@ -0,0 +1,1076 @@ +/* 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 |