Oilpan: adjust GC policy under memory pressure.

Source/platform/heap/ThreadState.cpp

 /*
  * 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 554 matching lines @@
     // Heap::markedObjectSize() may be underestimated if any thread has not
     // finished completeSweep().
     size_t currentObjectSize = allocatedObjectSize + Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages();
     // 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 allocatedObjectSize >= 1024 * 1024 && currentObjectSize > estimatedLiveObjectSize * 3 / 2;
 #endif
 }
 
+namespace {

[haraken, 2015/06/11 04:10:30]

Or static. No strong opinion.

+
+inline bool shouldForceMemoryPressureGC(size_t currentSize, size_t estimatedSize)

[haraken, 2015/06/11 04:10:30]

currentObjectSize, estimatedLiveObjectSize

+{
+    if (currentSize < 300 * 1024 * 1024)
+        return false;
+
+    // If we're consuming too much memory, trigger a conservative GC
+    // aggressively. This is a safe guard to avoid OOM.
+    return (currentSize >> 10) > (estimatedSize >> 10) * 3 / 2;

[haraken, 2015/06/11 04:10:30]

Add a comment about why we want to shift the size.

[sof, 2015/06/11 08:45:02]

Done.

+}
+
+} // namespace
+
 // TODO(haraken): We should improve the GC heuristics.
 // These heuristics affect performance significantly.
 bool ThreadState::shouldForceConservativeGC()
 {
     if (UNLIKELY(isGCForbidden()))
         return false;
 
     // 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 estimatedLiveObjectSize = Heap::estimatedLiveObjectSize();
     size_t allocatedObjectSize = Heap::allocatedObjectSize();
     // Heap::markedObjectSize() may be underestimated if any thread has not
     // finished completeSweep().
     size_t currentObjectSize = allocatedObjectSize + Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages();
-    if (currentObjectSize >= 300 * 1024 * 1024) {
-        // If we're consuming too much memory, trigger a conservative GC
-        // aggressively. This is a safe guard to avoid OOM.
-        return currentObjectSize > estimatedLiveObjectSize * 3 / 2;
-    }
+    if (shouldForceMemoryPressureGC(currentObjectSize, estimatedLiveObjectSize))
+        return true;
     // Schedule a conservative GC if Oilpan has allocated more than 32 MB since
     // the last GC and the current memory usage is >400% larger than
     // the estimated live memory usage.
     // TODO(haraken): 400% is too large. Lower the heap growing factor.
     return allocatedObjectSize >= 32 * 1024 * 1024 && currentObjectSize > 5 * estimatedLiveObjectSize;
 }
 
 void ThreadState::scheduleGCIfNeeded()
 {
     checkThread();
@@ skipping 180 matching lines @@
 
 ThreadState::GCState ThreadState::gcState() const
 {
     return m_gcState;
 }
 
 void ThreadState::didV8GC()
 {
     checkThread();
     if (isMainThread()) {
+        size_t currentObjectSize = Heap::allocatedObjectSize() + Heap::markedObjectSize() + WTF::Partitions::totalSizeOfCommittedPages();

[haraken, 2015/06/11 04:10:31]

Or you can do:

  if (shouldForceMemoryPressureGC()) {
    Heap::collectGarbage(HeapPointersOnStack, GCWithoutSweep,
Heap::ConservativeGC);
    return;
  }

+        size_t estimatedLiveObjectSize = Heap::estimatedLiveObjectSize();
+        if (shouldForceMemoryPressureGC(currentObjectSize, estimatedLiveObjectSize)) {
+            // Under memory pressure, force a conservative GC.
+            Heap::collectGarbage(HeapPointersOnStack, GCWithoutSweep, Heap::ConservativeGC);
+            return;
+        }
         // Lower the estimated live object size because the V8 major GC is
         // expected to have collected a lot of DOM wrappers and dropped
         // references to their DOM objects.
         Heap::setEstimatedLiveObjectSize(Heap::estimatedLiveObjectSize() / 2);

[haraken, 2015/06/11 04:10:31]

I think we should do this first.

Maybe a better fix would be:

1) Rename this function to didV8MajorGC.

2) Change the code to:

  void didV8MajorGC() {
    if (isMainThread()) {
      Heap::setEstimatedLiveObjectSize(Heap::estimatedLiveObjectSize() / 2);
      scheduleGCIfNeeded();
    }
  }

3) Remove scheduleIdleGC() and schedulePreciseGC() from majorGCEpilogue.

[sof, 2015/06/11 08:45:02]

Nice. I think that makes good sense, shifting this code over to the Oilpan side.
Done.

     }
 }
 
 void ThreadState::runScheduledGC(StackState stackState)
 {
     checkThread();
     if (stackState != NoHeapPointersOnStack)
         return;
 
     // If a safe point is entered while initiating a GC, we clearly do
@@ skipping 568 matching lines @@
         json->beginArray(it->key.ascii().data());
         for (size_t age = 0; age <= maxHeapObjectAge; ++age)
             json->pushInteger(it->value.ages[age]);
         json->endArray();
     }
     TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(TRACE_DISABLED_BY_DEFAULT("blink_gc"), statsName, this, json.release());
 }
 #endif
 
 } // namespace blink