Provide more accurate results about used heap size via GetHeapStatistics.

src/heap.h

 // Copyright 2010 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
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@@ skipping 257 matching lines @@
   static intptr_t CommittedMemoryExecutable();
 
   // Returns the available bytes in space w/o growing.
   // Heap doesn't guarantee that it can allocate an object that requires
   // all available bytes. Check MaxHeapObjectSize() instead.
   static intptr_t Available();
 
   // Returns the maximum object size in paged space.
   static inline int MaxObjectSizeInPagedSpace();
 
-  // Returns of size of all objects residing in the heap.
+  // Returns size of all objects residing in the heap.
   static intptr_t SizeOfObjects();
+  // Does the same as the previous function, but more precisely,

[Mads Ager (chromium), 2010/11/12 11:11:27]

Hmm, this looks strange. Computing the same but getting a different result.

That indicates to me that the SizeOfObjects method is either incorrectly named
or should be fixed.

I wonder if the difference here is only due to the free-list being excluded in
your implementation. If that is the case we should fix the original method to
exclude the size of the memory in the free list which we should have available
directly somewhere.

+  // by iterating heap contents. The resulting number is usually
+  // ~10% lower.
+  static intptr_t SizeOfObjectsSlow();
 
   // Return the starting address and a mask for the new space.  And-masking an
   // address with the mask will result in the start address of the new space
   // for all addresses in either semispace.
   static Address NewSpaceStart() { return new_space_.start(); }
   static uintptr_t NewSpaceMask() { return new_space_.mask(); }
   static Address NewSpaceTop() { return new_space_.top(); }
 
   static NewSpace* new_space() { return &new_space_; }
   static OldSpace* old_pointer_space() { return old_pointer_space_; }
@@ skipping 1795 matching lines @@
   // Return whether this object should be retained. If NULL is returned the
   // object has no references. Otherwise the address of the retained object
   // should be returned as in some GC situations the object has been moved.
   virtual Object* RetainAs(Object* object) = 0;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_