Do not do post GC processing for scavenges....

src/heap.cc

 // Copyright 2009 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 460 matching lines @@
     old_gen_promotion_limit_ =
         old_gen_size + Max(kMinimumPromotionLimit, old_gen_size / 3);
     old_gen_allocation_limit_ =
         old_gen_size + Max(kMinimumAllocationLimit, old_gen_size / 2);
     old_gen_exhausted_ = false;
   }
   Scavenge();
 
   Counters::objs_since_last_young.Set(0);
 
-  PostGarbageCollectionProcessing();
+  if (collector == MARK_COMPACTOR) {
+    DisableAssertNoAllocation allow_allocation;
+    GlobalHandles::PostGarbageCollectionProcessing();
+  }
+
+  // Update relocatables.
+  Relocatable::PostGarbageCollectionProcessing();
 
   if (collector == MARK_COMPACTOR) {
     // Register the amount of external allocated memory.
     amount_of_external_allocated_memory_at_last_global_gc_ =
         amount_of_external_allocated_memory_;
   }
 
   if (collector == MARK_COMPACTOR && global_gc_epilogue_callback_) {
     ASSERT(!allocation_allowed_);
     global_gc_epilogue_callback_();
   }
   VerifySymbolTable();
 }
 
 
-void Heap::PostGarbageCollectionProcessing() {
-  // Process weak handles post gc.
-  {
-    DisableAssertNoAllocation allow_allocation;
-    GlobalHandles::PostGarbageCollectionProcessing();
-  }
-  // Update relocatables.
-  Relocatable::PostGarbageCollectionProcessing();
-}
-
-
 void Heap::MarkCompact(GCTracer* tracer) {
   gc_state_ = MARK_COMPACT;
   mc_count_++;
   tracer->set_full_gc_count(mc_count_);
   LOG(ResourceEvent("markcompact", "begin"));
 
   MarkCompactCollector::Prepare(tracer);
 
   bool is_compacting = MarkCompactCollector::IsCompacting();
 
@@ skipping 3374 matching lines @@
   for (int i = 0; i < kNumberOfCaches; i++) {
     if (caches_[i] != NULL) {
       delete caches_[i];
       caches_[i] = NULL;
     }
   }
 }
 
 
 } }  // namespace v8::internal