Oilpan: Schedule a precise GC when a page navigates

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index 079ac1912d0ce202fbbc8a761bbc15343b422211..23adf7747239f094d6fd31e4d9626a327f62459d 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -648,6 +648,23 @@ bool ThreadState::shouldSchedulePreciseGC()
 #endif
 }
 
+bool ThreadState::shouldSchedulePreciseGCOnNavigation(float estimatedRemovalRatio)
+{
+    // Avoid potential overflow by truncating to Kb.
+    size_t allocatedObjectSizeKb = Heap::allocatedObjectSize() >> 10;
+    // The estimated size is updated when the main thread finishes lazy
+    // sweeping. If this thread reaches here before the main thread finishes
+    // lazy sweeping, the thread will use the estimated size of the last GC.
+    size_t estimatedLiveObjectSizeKb = (estimatedLiveObjectSize() >> 10) * (1 - estimatedRemovalRatio);
+    // Heap::markedObjectSize() may be underestimated if any thread has not
+    // finished completeSweep().
+    size_t currentObjectSizeKb = currentObjectSize() >> 10;
+    // Schedule a precise GC if Oilpan has allocated more than 1 MB since
+    // the last GC and the current memory usage is >50% larger than
+    // the estimated live memory usage.
+    return allocatedObjectSizeKb >= 1024 && currentObjectSizeKb > (estimatedLiveObjectSizeKb * 3) / 2;
+}
+
 // TODO(haraken): We should improve the GC heuristics.
 // These heuristics affect performance significantly.
 bool ThreadState::shouldForceConservativeGC()
@@ -906,7 +923,7 @@ void ThreadState::runScheduledGC(StackState stackState)
         Heap::collectAllGarbage();
         break;
     case PreciseGCScheduled:
-        Heap::collectGarbage(NoHeapPointersOnStack, GCWithoutSweep, Heap::PreciseGC);
+        Heap::collectGarbage(NoHeapPointersOnStack, GCWithSweep, Heap::PreciseGC);

[haraken, 2015/08/03 01:03:59]

Maybe is the regression you're observing in the shadow-dom benchmarks related to
the synchronous sweep? What happens if we change this to GCWithoutSweep? (Maybe
the regression in the shadow-dom benchmarks will be gone but the regression in
Speedometer re-appears.)

         break;
     case IdleGCScheduled:
         // Idle time GC will be scheduled by Blink Scheduler.