Make --stress-compaction more stressful.

src/spaces-inl.h

 // Copyright 2011 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 277 matching lines @@
   return Failure::RetryAfterGC(identity());
 }
 
 
 // -----------------------------------------------------------------------------
 // NewSpace
 
 
 MaybeObject* NewSpace::AllocateRaw(int size_in_bytes) {
   Address old_top = allocation_info_.top;
+#ifdef DEBUG
+  if (FLAG_stress_compaction) {
+    if (allocation_info_.limit - old_top >= size_in_bytes * 4) {

[Michael Starzinger, 2012/04/24 11:39:15]

Could you add a one-liner comment why it helps to have holes in new-space when
stressing compaction?

+      int filler_size = size_in_bytes * 4;
+      for (int i = 0; i < filler_size; i += kPointerSize) {
+        *(reinterpret_cast<Object**>(old_top + i)) =
+            HEAP->one_pointer_filler_map();
+      }
+      old_top += filler_size;
+      allocation_info_.top += filler_size;
+    }
+  }
+#endif
+
   if (allocation_info_.limit - old_top < size_in_bytes) {
     return SlowAllocateRaw(size_in_bytes);
   }
 
-  Object* obj = HeapObject::FromAddress(allocation_info_.top);
+  Object* obj = HeapObject::FromAddress(old_top);
   allocation_info_.top += size_in_bytes;
   ASSERT_SEMISPACE_ALLOCATION_INFO(allocation_info_, to_space_);
 
   return obj;
 }
 
 
 LargePage* LargePage::Initialize(Heap* heap, MemoryChunk* chunk) {
   heap->incremental_marking()->SetOldSpacePageFlags(chunk);
   return static_cast<LargePage*>(chunk);
@@ skipping 26 matching lines @@
   Map* map = object->map();
   Heap* heap = object->GetHeap();
   return map == heap->raw_unchecked_free_space_map()
       || map == heap->raw_unchecked_one_pointer_filler_map()
       || map == heap->raw_unchecked_two_pointer_filler_map();
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_INL_H_