Allow Oilpan heap objects account for their external allocations.

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 0ae8284286368653772f4242475dd2bbe5d75e9d..ffb71e3ab4e6b7eb67266741eb072a4a9c02ebb4 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -669,6 +669,9 @@ bool ThreadState::shouldSchedulePreciseGC()
 // These heuristics affect performance significantly.
 bool ThreadState::shouldForceConservativeGC()
 {
+    if (Heap::isGCUrgentlyRequested())
+        return true;
+
     size_t newSize = Heap::allocatedObjectSize();
     if (newSize >= 300 * 1024 * 1024) {
         // If we consume too much memory, trigger a conservative GC
@@ -694,13 +697,22 @@ void ThreadState::scheduleGCIfNeeded()
     checkThread();
     // Allocation is allowed during sweeping, but those allocations should not
     // trigger nested GCs
-    if (isSweepingInProgress())
-        return;
+    if (isSweepingInProgress()) {
+        if (!Heap::isGCUrgentlyRequested() || !isSweepingScheduled())

[haraken, 2015/02/19 23:47:44]

As commented earlier, I guess we should just call completeSweep() if an urgent
GC is scheduled.

Note that scheduleGCIfNeeded can be called by outOfLineAllocate, where it's not
guaranteed that sweeping is complete.

So I still think that something like:
is what we want.

[sof, 2015/02/20 09:33:49]

This will already happen when the collectGarbage() for the conservative GC goes
ahead just below, as previously explained.

[haraken, 2015/02/23 08:42:27]

Makes sense.

+            return;
+        // Urgent GC requested with only a GC scheduled; fall through
+        // and have it be serviced by a conservative GC.
+    }
     ASSERT(!sweepForbidden());
 
-    if (shouldForceConservativeGC())
-        Heap::collectGarbage(ThreadState::HeapPointersOnStack, ThreadState::GCWithoutSweep);
-    else if (shouldSchedulePreciseGC())
+    if (shouldForceConservativeGC()) {

[haraken, 2015/02/19 23:47:44]

Slightly better:

if (Heap::isGCUrgentlyRequested()) {
  completeSweep();
  Heap::clearUrgentGC();
  Heap::collectGarbage(HeapPointersOnStack, GCWithSweep);
  return;
}
if (shouldForceConservativeGC()) {
  Heap::collectGarbage(ThreadState::HeapPointersOnStack,
ThreadState::GCWithoutSweep);
} else if (shouldSchedulePreciseGC())
  ...

[sof, 2015/02/20 09:33:49]

See above; redundant.

+        // If GC is deemed urgent, eagerly sweep and finalize any external allocations right away.
+        GCType gcType = Heap::isGCUrgentlyRequested() ? GCWithSweep : GCWithoutSweep;
+        Heap::clearUrgentGC();
+        Heap::collectGarbage(HeapPointersOnStack, gcType);
+        return;
+    }
+    if (shouldSchedulePreciseGC())
         schedulePreciseGC();
     else if (shouldScheduleIdleGC())
         scheduleIdleGC();