Just visit young array buffers during scavenge.

src/heap/objects-visiting.cc

Index: src/heap/objects-visiting.cc
diff --git a/src/heap/objects-visiting.cc b/src/heap/objects-visiting.cc
index 7b2e2d9a388939440e0aac0bb5c3263fedc4676f..b31abb8880d9e8bf4805653b61b036166fb2e964 100644
--- a/src/heap/objects-visiting.cc
+++ b/src/heap/objects-visiting.cc
@@ -191,15 +191,22 @@ struct WeakListVisitor;
 
 
 template <class T>
-Object* VisitWeakList(Heap* heap, Object* list, WeakObjectRetainer* retainer) {
+Object* VisitWeakList(Heap* heap, Object* list, WeakObjectRetainer* retainer,
+                      Object* last_young_object,
+                      Object** last_young_object_recorded) {
   Object* undefined = heap->undefined_value();
   Object* head = undefined;
   T* tail = NULL;
   MarkCompactCollector* collector = heap->mark_compact_collector();
   bool record_slots = MustRecordSlots(heap);
+  bool last_young_object_found = false;
   while (list != undefined) {
     // Check whether to keep the candidate in the list.
     T* candidate = reinterpret_cast<T*>(list);
+    if (last_young_object && !last_young_object_found) {
+      last_young_object_found = last_young_object == candidate;
+    }
+
     Object* retained = retainer->RetainAs(list);
     if (retained != NULL) {
       if (head == undefined) {
@@ -227,6 +234,19 @@ Object* VisitWeakList(Heap* heap, Object* list, WeakObjectRetainer* retainer) {
       WeakListVisitor<T>::VisitPhantomObject(heap, candidate);
     }
 
+    if (last_young_object_recorded && !heap->InNewSpace(retained)) {
+      *last_young_object_recorded = retained;
+    }
+
+    // The list of weak objects is usually order. It starts with objects
+    // recently allocated in the young generation followed by objects
+    // allocated in the old generation.
+    // For young generation collections we just have to visit until the last
+    // young generation objects.
+    if (last_young_object_found && retained) {
+      return head;
+    }
+
     // Move to next element in the list.
     list = WeakListVisitor<T>::WeakNext(candidate);
   }
@@ -235,6 +255,7 @@ Object* VisitWeakList(Heap* heap, Object* list, WeakObjectRetainer* retainer) {
   if (tail != NULL) {
     WeakListVisitor<T>::SetWeakNext(tail, undefined);
   }
+
   return head;
 }
 
@@ -316,7 +337,8 @@ struct WeakListVisitor<Context> {
   static void DoWeakList(Heap* heap, Context* context,
                          WeakObjectRetainer* retainer, int index) {
     // Visit the weak list, removing dead intermediate elements.
-    Object* list_head = VisitWeakList<T>(heap, context->get(index), retainer);
+    Object* list_head =
+        VisitWeakList<T>(heap, context->get(index), retainer, NULL, NULL);
 
     // Update the list head.
     context->set(index, list_head, UPDATE_WRITE_BARRIER);
@@ -368,7 +390,7 @@ struct WeakListVisitor<JSArrayBuffer> {
   static void VisitLiveObject(Heap* heap, JSArrayBuffer* array_buffer,
                               WeakObjectRetainer* retainer) {
     Object* typed_array_obj = VisitWeakList<JSArrayBufferView>(
-        heap, array_buffer->weak_first_view(), retainer);
+        heap, array_buffer->weak_first_view(), retainer, NULL, NULL);
     array_buffer->set_weak_first_view(typed_array_obj);
     if (typed_array_obj != heap->undefined_value() && MustRecordSlots(heap)) {
       Object** slot = HeapObject::RawField(array_buffer,
@@ -399,23 +421,19 @@ struct WeakListVisitor<AllocationSite> {
 };
 
 
-template Object* VisitWeakList<Code>(Heap* heap, Object* list,
-                                     WeakObjectRetainer* retainer);
-
-
-template Object* VisitWeakList<JSFunction>(Heap* heap, Object* list,
-                                           WeakObjectRetainer* retainer);
-
-
 template Object* VisitWeakList<Context>(Heap* heap, Object* list,
-                                        WeakObjectRetainer* retainer);
+                                        WeakObjectRetainer* retainer,
+                                        Object* last_young_object,
+                                        Object** last_young_object_recorded);
 
 
-template Object* VisitWeakList<JSArrayBuffer>(Heap* heap, Object* list,
-                                              WeakObjectRetainer* retainer);
+template Object* VisitWeakList<JSArrayBuffer>(
+    Heap* heap, Object* list, WeakObjectRetainer* retainer,
+    Object* last_young_object, Object** last_young_object_recorded);
 
 
-template Object* VisitWeakList<AllocationSite>(Heap* heap, Object* list,
-                                               WeakObjectRetainer* retainer);
+template Object* VisitWeakList<AllocationSite>(
+    Heap* heap, Object* list, WeakObjectRetainer* retainer,
+    Object* last_young_object, Object** last_young_object_recorded);
 }
 }  // namespace v8::internal