[heap] Evacuation for young generation

src/heap/incremental-marking.h

Index: src/heap/incremental-marking.h
diff --git a/src/heap/incremental-marking.h b/src/heap/incremental-marking.h
index c71328cc508423e2b972851fb3a66bc570aa4f4e..2405938f3171b04d3b55a93296a1012695473b25 100644
--- a/src/heap/incremental-marking.h
+++ b/src/heap/incremental-marking.h
@@ -185,17 +185,20 @@ class V8_EXPORT_PRIVATE IncrementalMarking {
 
   static void TransferMark(Heap* heap, HeapObject* from, HeapObject* to);
 
+  template <MarkBit::AccessMode access_mode = MarkBit::NON_ATOMIC>
   V8_INLINE static void TransferColor(HeapObject* from, HeapObject* to) {

[Michael Lippautz, 2017/04/21 07:05:51]

TransferColor might work concurrently in new space as multiple tasks allocate in
a single page (LAB) for evacuation.

[Hannes Payer (out of office), 2017/04/21 14:46:26]

I guess you do not need to synchronize.

[Michael Lippautz, 2017/04/24 13:15:08]

We need to synchronize for live byte count which is hidden in ObjectMarking.
E.g. multiple tasks might concurrently transfer colors onto the same page.

-    if (ObjectMarking::IsBlack(to, MarkingState::Internal(to))) {
+    if (ObjectMarking::IsBlack<access_mode>(to, MarkingState::Internal(to))) {
       DCHECK(to->GetHeap()->incremental_marking()->black_allocation());
       return;
     }
 
-    DCHECK(ObjectMarking::IsWhite(to, MarkingState::Internal(to)));
-    if (ObjectMarking::IsGrey(from, MarkingState::Internal(from))) {
-      ObjectMarking::WhiteToGrey(to, MarkingState::Internal(to));
-    } else if (ObjectMarking::IsBlack(from, MarkingState::Internal(from))) {
-      ObjectMarking::WhiteToBlack(to, MarkingState::Internal(to));
+    DCHECK(ObjectMarking::IsWhite<access_mode>(to, MarkingState::Internal(to)));
+    if (ObjectMarking::IsGrey<access_mode>(from,
+                                           MarkingState::Internal(from))) {
+      ObjectMarking::WhiteToGrey<access_mode>(to, MarkingState::Internal(to));
+    } else if (ObjectMarking::IsBlack<access_mode>(
+                   from, MarkingState::Internal(from))) {
+      ObjectMarking::WhiteToBlack<access_mode>(to, MarkingState::Internal(to));
     }
   }