Oilpan: Move synchronous Oilpan GCs out of V8 GC epilogues

third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp

 /*
  * Copyright (C) 2009 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 326 matching lines @@
         }
         // TODO(haraken): Remove this. See the comment in gcPrologue.
         if (ThreadState::current())
             ThreadState::current()->scheduleV8FollowupGCIfNeeded(BlinkGC::V8MinorGC);
         break;
     case v8::kGCTypeMarkSweepCompact:
         TRACE_EVENT_END1("devtools.timeline,v8", "MajorGC", "usedHeapSizeAfter", usedHeapSize(isolate));
         if (isMainThread()) {
             TRACE_EVENT_SET_NONCONST_SAMPLING_STATE(V8PerIsolateData::from(isolate)->previousSamplingState());
         }
+        if (ThreadState::current())

[sof, 2016/02/01 14:41:48]

What does the switch to scheduling via kGCTypeMarkSweepCompact instead of
kGCTypeProcessWeakCallbacks accomplish?

[haraken, 2016/02/01 15:05:57]

V8 is now making a change not to invoke kGCTypeProcessWeakCallbacks if there is
no second-pass callback (in common cases there is no second-pass callback with
oilpan enabled). So we cannot rely on kGCTypeProcessWeakCallbacks any more.

+            ThreadState::current()->scheduleV8FollowupGCIfNeeded(BlinkGC::V8MajorGC);
         break;
     case v8::kGCTypeIncrementalMarking:
         TRACE_EVENT_END1("devtools.timeline,v8", "MajorGC", "usedHeapSizeAfter", usedHeapSize(isolate));
         if (isMainThread()) {
             TRACE_EVENT_SET_NONCONST_SAMPLING_STATE(V8PerIsolateData::from(isolate)->previousSamplingState());
         }
         break;
     case v8::kGCTypeProcessWeakCallbacks:
         TRACE_EVENT_END1("devtools.timeline,v8", "MajorGC", "usedHeapSizeAfter", usedHeapSize(isolate));
         if (isMainThread()) {
             TRACE_EVENT_SET_NONCONST_SAMPLING_STATE(V8PerIsolateData::from(isolate)->previousSamplingState());
         }
-        // TODO(haraken): Remove this. See the comment in gcPrologue.
-        if (ThreadState::current())
-            ThreadState::current()->scheduleV8FollowupGCIfNeeded(BlinkGC::V8MajorGC);
         break;
     default:
         ASSERT_NOT_REACHED();
     }
 
     if (isMainThread())
         ScriptForbiddenScope::exit();
 
     // v8::kGCCallbackFlagForced forces a Blink heap garbage collection
     // when a garbage collection was forced from V8. This is either used
@@ skipping 81 matching lines @@
     Visitor* m_visitor;
 };
 
 void V8GCController::traceDOMWrappers(v8::Isolate* isolate, Visitor* visitor)
 {
     DOMWrapperTracer tracer(visitor);
     isolate->VisitHandlesWithClassIds(&tracer);
 }
 
 } // namespace blink