Use an allocation site scratchpad to speed up allocaton site processing during gc.

src/heap-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 471 matching lines @@
   ScavengeObject(p, *p);
 }
 
 
 void Heap::UpdateAllocationSiteFeedback(HeapObject* object) {
   if (FLAG_allocation_site_pretenuring && object->IsJSObject()) {
     AllocationMemento* memento = AllocationMemento::FindForJSObject(
         JSObject::cast(object), true);
     if (memento != NULL) {
       ASSERT(memento->IsValid());
-      memento->GetAllocationSite()->IncrementMementoFoundCount();
+      bool add_to_scratchpad =
+          memento->GetAllocationSite()->IncrementMementoFoundCount();
+      Heap* heap = object->GetIsolate()->heap();
+      if (add_to_scratchpad && heap->allocation_sites_scratchpad_length <
+              kAllocationSiteScratchpadSize) {
+        heap->allocation_sites_scratchpad[
+            heap->allocation_sites_scratchpad_length++] =
+                memento->GetAllocationSite();
+      }
     }
   }
 }
 
 
 void Heap::ScavengeObject(HeapObject** p, HeapObject* object) {
   ASSERT(object->GetIsolate()->heap()->InFromSpace(object));
 
   // We use the first word (where the map pointer usually is) of a heap
   // object to record the forwarding pointer.  A forwarding pointer can
@@ skipping 355 matching lines @@
 #ifdef DEBUG
   Isolate* isolate = Isolate::Current();
   isolate->heap()->disallow_allocation_failure_ = old_state_;
 #endif
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_