Oilpan: Schedule a precise GC when a page navigates

Source/platform/heap/ThreadState.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 167 matching lines @@
         // thread.
         ThreadTerminationGC,
     };
 
     // See setGCState() for possible state transitions.
     enum GCState {
         NoGCScheduled,
         IdleGCScheduled,
         PreciseGCScheduled,
         FullGCScheduled,
+        PageNavigationGCScheduled,
         GCRunning,
         EagerSweepScheduled,
         LazySweepScheduled,
         Sweeping,
         SweepingAndIdleGCScheduled,
         SweepingAndPreciseGCScheduled,
     };
 
     enum HeapIndices {
         EagerSweepHeapIndex = 0,
@@ skipping 124 matching lines @@
 #endif
 
     void didV8MajorGC();
 
     void performIdleGC(double deadlineSeconds);
     void performIdleLazySweep(double deadlineSeconds);
 
     void scheduleIdleGC();
     void scheduleIdleLazySweep();
     void schedulePreciseGC();
+    void schedulePageNavigationGCIfNeeded(float estimatedRemovalRatio);
+    void schedulePageNavigationGC();
     void scheduleGCIfNeeded();
     void setGCState(GCState);
     GCState gcState() const;
     bool isInGC() const { return gcState() == GCRunning; }
     bool isSweepingInProgress() const
     {
         return gcState() == Sweeping || gcState() == SweepingAndPreciseGCScheduled || gcState() == SweepingAndIdleGCScheduled;
     }
 
     // A GC runs in the following sequence.
@@ skipping 329 matching lines @@
     // shouldSchedule{Precise,Idle}GC and shouldForceConservativeGC
     // implement the heuristics that are used to determine when to collect garbage.
     // If shouldForceConservativeGC returns true, we force the garbage
     // collection immediately. Otherwise, if should*GC returns true, we
     // record that we should garbage collect the next time we return
     // to the event loop. If both return false, we don't need to
     // collect garbage at this point.
     bool shouldScheduleIdleGC();
     bool shouldSchedulePreciseGC();
     bool shouldForceConservativeGC();
+    // estimatedRemovalRatio is the estimated ratio of objects that will be no
+    // longer necessary due to the navigation.
+    bool shouldSchedulePageNavigationGC(float estimatedRemovalRatio);
 
     // Internal helper for GC policy handling code. Returns true if
     // an urgent conservative GC is now needed due to memory pressure.
     bool shouldForceMemoryPressureGC();
     size_t estimatedLiveObjectSize();
     size_t currentObjectSize();
 
     void runScheduledGC(StackState);
 
     void eagerSweep();
@@ skipping 112 matching lines @@
 };
 
 template<> class ThreadStateFor<AnyThread> {
 public:
     static ThreadState* state() { return ThreadState::current(); }
 };
 
 } // namespace blink
 
 #endif // ThreadState_h