Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 645 insertions, 0 deletions

diff --git a/dom/base/CCGCScheduler.h b/dom/base/CCGCScheduler.h
new file mode 100644
index 0000000000..cd2c46eeff
--- /dev/null
+++ b/dom/base/CCGCScheduler.h
@@ -0,0 +1,645 @@
+/* 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 "js/SliceBudget.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/MainThreadIdlePeriod.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/TimeStamp.h"
+#include "nsCycleCollector.h"
+#include "nsJSEnvironment.h"
+
+namespace mozilla {
+
+static const TimeDuration kOneMinute = TimeDuration::FromSeconds(60.0f);
+
+// The amount of time we wait between a request to CC (after GC ran)
+// and doing the actual CC.
+static const TimeDuration kCCDelay = TimeDuration::FromSeconds(6);
+
+static const TimeDuration kCCSkippableDelay =
+    TimeDuration::FromMilliseconds(250);
+
+// In case the cycle collector isn't run at all, we don't want forget skippables
+// to run too often. So limit the forget skippable cycle to start at earliest 2
+// seconds after the end of the previous cycle.
+static const TimeDuration kTimeBetweenForgetSkippableCycles =
+    TimeDuration::FromSeconds(2);
+
+// ForgetSkippable is usually fast, so we can use small budgets.
+// This isn't a real budget but a hint to IdleTaskRunner whether there
+// is enough time to call ForgetSkippable.
+static const TimeDuration kForgetSkippableSliceDuration =
+    TimeDuration::FromMilliseconds(2);
+
+// Maximum amount of time that should elapse between incremental CC slices
+static const TimeDuration kICCIntersliceDelay =
+    TimeDuration::FromMilliseconds(64);
+
+// Time budget for an incremental CC slice when using timer to run it.
+static const TimeDuration kICCSliceBudget = TimeDuration::FromMilliseconds(3);
+// Minimum budget for an incremental CC slice when using idle time to run it.
+static const TimeDuration kIdleICCSliceBudget =
+    TimeDuration::FromMilliseconds(2);
+
+// Maximum total duration for an ICC
+static const TimeDuration kMaxICCDuration = TimeDuration::FromSeconds(2);
+
+// Force a CC after this long if there's more than NS_CC_FORCED_PURPLE_LIMIT
+// objects in the purple buffer.
+static const TimeDuration kCCForced = kOneMinute * 2;
+static const uint32_t kCCForcedPurpleLimit = 10;
+
+// Don't allow an incremental GC to lock out the CC for too long.
+static const TimeDuration kMaxCCLockedoutTime = TimeDuration::FromSeconds(30);
+
+// Trigger a CC if the purple buffer exceeds this size when we check it.
+static const uint32_t kCCPurpleLimit = 200;
+
+enum class CCRunnerAction {
+  None,
+  ForgetSkippable,
+  CleanupContentUnbinder,
+  CleanupDeferred,
+  CycleCollect,
+  StopRunning
+};
+
+enum CCRunnerYield { Continue, Yield };
+
+enum CCRunnerForgetSkippableRemoveChildless {
+  KeepChildless = false,
+  RemoveChildless = true
+};
+
+struct CCRunnerStep {
+  // The action to scheduler is instructing the caller to perform.
+  CCRunnerAction mAction;
+
+  // Whether to stop processing actions for this invocation of the timer
+  // callback.
+  CCRunnerYield mYield;
+
+  // If the action is ForgetSkippable, then whether to remove childless nodes
+  // or not. (ForgetSkippable is the only action requiring a parameter; if
+  // that changes, this will become a union.)
+  CCRunnerForgetSkippableRemoveChildless mRemoveChildless;
+};
+
+class CCGCScheduler {
+ public:
+  // Mockable functions to interface with the code being scheduled.
+
+  // Current time. In real usage, this will just return TimeStamp::Now(), but
+  // tests can reimplement it to return a value controlled by the test.
+  static inline TimeStamp Now();
+
+  // Number of entries in the purple buffer (those objects whose ref counts
+  // have been decremented since the previous CC, roughly), and are therefore
+  // "suspected" of being members of cyclic garbage.
+  static inline uint32_t SuspectedCCObjects();
+
+  // Parameter setting
+
+  void SetActiveIntersliceGCBudget(TimeDuration aDuration) {
+    mActiveIntersliceGCBudget = aDuration;
+  }
+
+  // State retrieval
+
+  TimeDuration GetCCBlockedTime(TimeStamp aNow) const {
+    MOZ_ASSERT(mInIncrementalGC);
+    MOZ_ASSERT(!mCCBlockStart.IsNull());
+    return aNow - mCCBlockStart;
+  }
+
+  bool InIncrementalGC() const { return mInIncrementalGC; }
+
+  TimeStamp GetLastCCEndTime() const { return mLastCCEndTime; }
+
+  bool IsEarlyForgetSkippable(uint32_t aN = kMajorForgetSkippableCalls) const {
+    return mCleanupsSinceLastGC < aN;
+  }
+
+  bool NeedsFullGC() const { return mNeedsFullGC; }
+
+  // State modification
+
+  void SetNeedsFullGC(bool aNeedGC = true) { mNeedsFullGC = aNeedGC; }
+
+  // Ensure that the current runner does a cycle collection, and trigger a GC
+  // after it finishes.
+  void EnsureCCThenGC() {
+    MOZ_ASSERT(mCCRunnerState != CCRunnerState::Inactive);
+    mNeedsFullCC = true;
+    mNeedsGCAfterCC = true;
+  }
+
+  void NoteGCBegin() {
+    // Treat all GC as incremental here; non-incremental GC will just appear to
+    // be one slice.
+    mInIncrementalGC = true;
+  }
+
+  void NoteGCEnd() {
+    mInIncrementalGC = false;
+    mCCBlockStart = TimeStamp();
+    mInIncrementalGC = false;
+    mNeedsFullCC = true;
+    mHasRunGC = true;
+
+    mCleanupsSinceLastGC = 0;
+    mCCollectedWaitingForGC = 0;
+    mCCollectedZonesWaitingForGC = 0;
+    mLikelyShortLivingObjectsNeedingGC = 0;
+  }
+
+  // When we decide to do a cycle collection but we're in the middle of an
+  // incremental GC, the CC is "locked out" until the GC completes -- unless
+  // the wait is too long, and we decide to finish the incremental GC early.
+  void BlockCC(TimeStamp aNow) {
+    MOZ_ASSERT(mInIncrementalGC);
+    MOZ_ASSERT(mCCBlockStart.IsNull());
+    mCCBlockStart = aNow;
+  }
+
+  void UnblockCC() { mCCBlockStart = TimeStamp(); }
+
+  // Returns the number of purple buffer items that were processed and removed.
+  uint32_t NoteForgetSkippableComplete(
+      TimeStamp aNow, uint32_t aSuspectedBeforeForgetSkippable) {
+    mLastForgetSkippableEndTime = aNow;
+    uint32_t suspected = SuspectedCCObjects();
+    mPreviousSuspectedCount = suspected;
+    mCleanupsSinceLastGC++;
+    return aSuspectedBeforeForgetSkippable - suspected;
+  }
+
+  // After collecting cycles, record the results that are used in scheduling
+  // decisions.
+  void NoteCycleCollected(const CycleCollectorResults& aResults) {
+    mCCollectedWaitingForGC += aResults.mFreedGCed;
+    mCCollectedZonesWaitingForGC += aResults.mFreedJSZones;
+  }
+
+  // This is invoked when the whole process of collection is done -- i.e., CC
+  // preparation (eg ForgetSkippables), the CC itself, and the optional
+  // followup GC. There really ought to be a separate name for the overall CC
+  // as opposed to the actual cycle collection portion.
+  void NoteCCEnd(TimeStamp aWhen) {
+    mLastCCEndTime = aWhen;
+    mNeedsFullCC = false;
+
+    // The GC for this CC has already been requested.
+    mNeedsGCAfterCC = false;
+  }
+
+  // The CC was abandoned without running a slice, so we only did forget
+  // skippables. Prevent running another cycle soon.
+  void NoteForgetSkippableOnlyCycle() {
+    mLastForgetSkippableCycleEndTime = Now();
+  }
+
+  void Shutdown() { mDidShutdown = true; }
+
+  // Scheduling
+
+  // Return a budget along with a boolean saying whether to prefer to run short
+  // slices and stop rather than continuing to the next phase of cycle
+  // collection.
+  inline js::SliceBudget ComputeCCSliceBudget(TimeStamp aDeadline,
+                                              TimeStamp aCCBeginTime,
+                                              TimeStamp aPrevSliceEndTime,
+                                              bool* aPreferShorterSlices) const;
+
+  inline TimeDuration ComputeInterSliceGCBudget(TimeStamp aDeadline,
+                                                TimeStamp aNow) const;
+
+  bool ShouldForgetSkippable() const {
+    // Only do a forget skippable if there are more than a few new objects
+    // or we're doing the initial forget skippables.
+    return ((mPreviousSuspectedCount + 100) <= SuspectedCCObjects()) ||
+           mCleanupsSinceLastGC < kMajorForgetSkippableCalls;
+  }
+
+  // There is reason to suspect that there may be a significant amount of
+  // garbage to cycle collect: either we just finished a GC, or the purple
+  // buffer is getting really big, or it's getting somewhat big and it has been
+  // too long since the last CC.
+  bool IsCCNeeded(TimeStamp aNow = Now()) const {
+    if (mNeedsFullCC) {
+      return true;
+    }
+    uint32_t suspected = SuspectedCCObjects();
+    return suspected > kCCPurpleLimit ||
+           (suspected > kCCForcedPurpleLimit && mLastCCEndTime &&
+            aNow - mLastCCEndTime > kCCForced);
+  }
+
+  inline bool ShouldScheduleCC() const;
+
+  // If we collected a substantial amount of cycles, poke the GC since more
+  // objects might be unreachable now.
+  bool NeedsGCAfterCC() const {
+    return mCCollectedWaitingForGC > 250 || mCCollectedZonesWaitingForGC > 0 ||
+           mLikelyShortLivingObjectsNeedingGC > 2500 || mNeedsGCAfterCC;
+  }
+
+  bool IsLastEarlyCCTimer(int32_t aCurrentFireCount) const {
+    int32_t numEarlyTimerFires =
+        std::max(int32_t(mCCDelay / kCCSkippableDelay) - 2, 1);
+
+    return aCurrentFireCount >= numEarlyTimerFires;
+  }
+
+  enum class CCRunnerState {
+    Inactive,
+    ReducePurple,
+    CleanupChildless,
+    CleanupContentUnbinder,
+    CleanupDeferred,
+    StartCycleCollection,
+    CycleCollecting,
+    Canceled,
+    NumStates
+  };
+
+  void InitCCRunnerStateMachine(CCRunnerState initialState) {
+    // The state machine should always have been deactivated after the previous
+    // collection, however far that collection may have gone.
+    MOZ_ASSERT(mCCRunnerState == CCRunnerState::Inactive,
+               "DeactivateCCRunner should have been called");
+    mCCRunnerState = initialState;
+
+    // Currently, there are only two entry points to the non-Inactive part of
+    // the state machine.
+    if (initialState == CCRunnerState::ReducePurple) {
+      mCCDelay = kCCDelay;
+      mCCRunnerEarlyFireCount = 0;
+    } else if (initialState == CCRunnerState::CycleCollecting) {
+      // Nothing needed.
+    } else {
+      MOZ_CRASH("Invalid initial state");
+    }
+  }
+
+  void DeactivateCCRunner() { mCCRunnerState = CCRunnerState::Inactive; }
+
+  inline CCRunnerStep GetNextCCRunnerAction(TimeStamp aDeadline);
+
+  // aStartTimeStamp : when the ForgetSkippable timer fired. This may be some
+  // time ago, if an incremental GC needed to be finished.
+  js::SliceBudget ComputeForgetSkippableBudget(TimeStamp aStartTimeStamp,
+                                               TimeStamp aDeadline);
+
+ private:
+  // State
+
+  // An incremental GC is in progress, which blocks the CC from running for its
+  // duration (or until it goes too long and is finished synchronously.)
+  bool mInIncrementalGC = false;
+
+  // When the CC started actually waiting for the GC to finish. This will be
+  // set to non-null at a later time than mCCLockedOut.
+  TimeStamp mCCBlockStart;
+
+  bool mDidShutdown = false;
+
+  TimeStamp mLastForgetSkippableEndTime;
+  uint32_t mForgetSkippableCounter = 0;
+  TimeStamp mForgetSkippableFrequencyStartTime;
+  TimeStamp mLastCCEndTime;
+  TimeStamp mLastForgetSkippableCycleEndTime;
+
+  CCRunnerState mCCRunnerState = CCRunnerState::Inactive;
+  int32_t mCCRunnerEarlyFireCount = 0;
+  TimeDuration mCCDelay = kCCDelay;
+
+  // Prevent the very first CC from running before we have GC'd and set the
+  // gray bits.
+  bool mHasRunGC = false;
+
+  bool mNeedsFullCC = false;
+  bool mNeedsFullGC = true;
+  bool mNeedsGCAfterCC = false;
+  uint32_t mPreviousSuspectedCount = 0;
+
+  uint32_t mCleanupsSinceLastGC = UINT32_MAX;
+
+ public:
+  uint32_t mCCollectedWaitingForGC = 0;
+  uint32_t mCCollectedZonesWaitingForGC = 0;
+  uint32_t mLikelyShortLivingObjectsNeedingGC = 0;
+
+  // Configuration parameters
+
+  TimeDuration mActiveIntersliceGCBudget = TimeDuration::FromMilliseconds(5);
+};
+
+js::SliceBudget CCGCScheduler::ComputeCCSliceBudget(
+    TimeStamp aDeadline, TimeStamp aCCBeginTime, TimeStamp aPrevSliceEndTime,
+    bool* aPreferShorterSlices) const {
+  TimeStamp now = Now();
+
+  *aPreferShorterSlices =
+      aDeadline.IsNull() || (aDeadline - now) < kICCSliceBudget;
+
+  TimeDuration baseBudget =
+      aDeadline.IsNull() ? kICCSliceBudget : aDeadline - now;
+
+  if (aCCBeginTime.IsNull()) {
+    // If no CC is in progress, use the standard slice time.
+    return js::SliceBudget(baseBudget);
+  }
+
+  // Only run a limited slice if we're within the max running time.
+  MOZ_ASSERT(now >= aCCBeginTime);
+  TimeDuration runningTime = now - 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(now >= aPrevSliceEndTime);
+  double sliceDelayMultiplier = (now - 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(
+      std::max({delaySliceBudget, laterSliceBudget, baseBudget}));
+}
+
+inline TimeDuration CCGCScheduler::ComputeInterSliceGCBudget(
+    TimeStamp aDeadline, TimeStamp aNow) const {
+  // 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 budget;
+  }
+
+  TimeDuration blockedTime = aNow - mCCBlockStart;
+  TimeDuration maxSliceGCBudget = mActiveIntersliceGCBudget * 10;
+  double percentOfBlockedTime =
+      std::min(blockedTime / kMaxCCLockedoutTime, 1.0);
+  return std::max(budget, maxSliceGCBudget.MultDouble(percentOfBlockedTime));
+}
+
+bool CCGCScheduler::ShouldScheduleCC() const {
+  if (!mHasRunGC) {
+    return false;
+  }
+
+  TimeStamp now = Now();
+
+  // Don't run consecutive CCs too often.
+  if (mCleanupsSinceLastGC && !mLastCCEndTime.IsNull()) {
+    if (now - mLastCCEndTime < kCCDelay) {
+      return false;
+    }
+  }
+
+  // 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 (now - mLastForgetSkippableCycleEndTime <
+        kTimeBetweenForgetSkippableCycles) {
+      return false;
+    }
+  }
+
+  return IsCCNeeded(now);
+}
+
+CCRunnerStep CCGCScheduler::GetNextCCRunnerAction(TimeStamp aDeadline) {
+  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};
+  }
+
+  TimeStamp now = Now();
+
+  if (InIncrementalGC()) {
+    if (mCCBlockStart.IsNull()) {
+      BlockCC(now);
+
+      // 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(now) < 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(now)) {
+    // If we don't pass the threshold for wanting to cycle collect, stop now
+    // (after possibly doing a final ForgetSkippable).
+    mCCRunnerState = CCRunnerState::Canceled;
+    NoteForgetSkippableOnlyCycle();
+
+    // Preserve the previous code's idea of when to check whether a
+    // ForgetSkippable should be fired.
+    if (desc.mTryFinalForgetSkippable && ShouldForgetSkippable()) {
+      // 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};
+  }
+
+  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()) {
+        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 (now >= 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 (now >= 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:
+      return {CCRunnerAction::CycleCollect, Yield};
+
+    default:
+      MOZ_CRASH("Unexpected CCRunner state");
+  };
+}
+
+inline 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