Forward transition objects to grey if they are referenced by a large object

src/incremental-marking-inl.h

 // Copyright 2012 the V8 project authors. 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 19 matching lines @@
 
 #include "incremental-marking.h"
 
 namespace v8 {
 namespace internal {
 
 
 bool IncrementalMarking::BaseRecordWrite(HeapObject* obj,
                                          Object** slot,
                                          Object* value) {
-  MarkBit value_bit = Marking::MarkBitFrom(HeapObject::cast(value));
+  HeapObject* value_heap_obj = HeapObject::cast(value);
+  MarkBit value_bit = Marking::MarkBitFrom(value_heap_obj);
   if (Marking::IsWhite(value_bit)) {
     MarkBit obj_bit = Marking::MarkBitFrom(obj);
     if (Marking::IsBlack(obj_bit)) {
-      BlackToGreyAndUnshift(obj, obj_bit);
+      // TODO(hpayer): make decision based on if object has a progress bar
+      const int kLargeObjectSize = 1024 * 1024;
+      if (obj->Size() > kLargeObjectSize) {
+        WhiteToGreyAndPush(value_heap_obj, value_bit);
+      } else {
+        BlackToGreyAndUnshift(obj, obj_bit);
+      }
       RestartIfNotMarking();
     }
-
     // Object is either grey or white.  It will be scanned if survives.
     return false;

[Michael Starzinger, 2012/11/14 08:42:24]

This will prevent the slot from being recorded when we do a forward
white-to-grey transition. Compaction might corrupt the pointer. In the case of a
white-to-grey transition we need to fall through to the code below.

[payer, 2012/11/14 09:12:37]

Done.

   }
   if (!is_compacting_) return false;
   MarkBit obj_bit = Marking::MarkBitFrom(obj);
   return Marking::IsBlack(obj_bit);
 }
 
 
 void IncrementalMarking::RecordWrite(HeapObject* obj,
                                      Object** slot,
                                      Object* value) {
@@ skipping 61 matching lines @@
 
 void IncrementalMarking::WhiteToGreyAndPush(HeapObject* obj, MarkBit mark_bit) {
   Marking::WhiteToGrey(mark_bit);
   marking_deque_.PushGrey(obj);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_INCREMENTAL_MARKING_INL_H_