We mustn't finalize sweeping when V8 started collecting garbage.

third_party/WebKit/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 612 matching lines @@
     }
     if (gcType == BlinkGC::V8MajorGC) {
 #if PRINT_HEAP_STATS
         dataLogF("Scheduled IdleGC\n");
 #endif
         scheduleIdleGC();
         return;
     }
 }
 
-void ThreadState::willStartV8GC()

[haraken, 2015/11/20 15:11:35]

And don't remove this code :) I'll prepare a CL to call this in a posted task.

-{
-    // Finish Oilpan's complete sweeping before running a V8 GC.
-    // This will let the GC collect more V8 objects.
-    //
-    // TODO(haraken): It's a bit too late for a major GC to schedule
-    // completeSweep() here, because gcPrologue for a major GC is called
-    // not at the point where the major GC started but at the point where
-    // the major GC requests object grouping.
-    completeSweep();
-
-    // The fact that the PageNavigation GC is scheduled means that there is
-    // a dead frame. In common cases, a sequence of Oilpan's GC => V8 GC =>
-    // Oilpan's GC is needed to collect the dead frame. So we force the
-    // PageNavigation GC before running the V8 GC.
-    if (gcState() == PageNavigationGCScheduled) {
-#if PRINT_HEAP_STATS
-        dataLogF("Scheduled PageNavigationGC\n");
-#endif
-        Heap::collectGarbage(BlinkGC::HeapPointersOnStack, BlinkGC::GCWithSweep, BlinkGC::PageNavigationGC);
-    }
-}
-
 void ThreadState::schedulePageNavigationGCIfNeeded(float estimatedRemovalRatio)
 {
     ASSERT(checkThread());
     Heap::reportMemoryUsageForTracing();
 
 #if PRINT_HEAP_STATS
     dataLogF("ThreadState::schedulePageNavigationGCIfNeeded (estimatedRemovalRatio=%.2lf)\n", estimatedRemovalRatio);
 #endif
 
     if (isGCForbidden())
@@ skipping 817 matching lines @@
     threadDump->addScalar("dead_count", "objects", totalDeadCount);
     threadDump->addScalar("live_size", "bytes", totalLiveSize);
     threadDump->addScalar("dead_size", "bytes", totalDeadSize);
 
     WebMemoryAllocatorDump* heapsDump = BlinkGCMemoryDumpProvider::instance()->createMemoryAllocatorDumpForCurrentGC(heapsDumpName);
     WebMemoryAllocatorDump* classesDump = BlinkGCMemoryDumpProvider::instance()->createMemoryAllocatorDumpForCurrentGC(classesDumpName);
     BlinkGCMemoryDumpProvider::instance()->currentProcessMemoryDump()->addOwnershipEdge(classesDump->guid(), heapsDump->guid());
 }
 
 } // namespace blink