[heap] Evacuation for young generation

src/heap/incremental-marking.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_INCREMENTAL_MARKING_H_
 #define V8_HEAP_INCREMENTAL_MARKING_H_
 
 #include "src/cancelable-task.h"
 #include "src/execution.h"
 #include "src/heap/heap.h"
@@ skipping 167 matching lines @@
   void ClearIdleMarkingDelayCounter();
 
   bool IsIdleMarkingDelayCounterLimitReached();
 
   static void MarkGrey(Heap* heap, HeapObject* object);
 
   static void MarkBlack(HeapObject* object, int size);
 
   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));
     }
   }
 
   void IterateBlackObject(HeapObject* object);
 
   Heap* heap() const { return heap_; }
 
   IncrementalMarkingJob* incremental_marking_job() {
     return &incremental_marking_job_;
   }
@@ skipping 86 matching lines @@
 
   Observer new_generation_observer_;
   Observer old_generation_observer_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_INCREMENTAL_MARKING_H_