[PATCH] mm/slab.c: prefetchw the start of new allocated objects

Mostobjects returned by __cache_alloc() will be written by the caller,
(but not all callers want to write all the object, but just at the
begining) prefetchw() tells the modern CPU to think about the future
writes, ie start some memory transactions in advance.
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

mm/slab.c

@@ -2166,7 +2166,9 @@ static inline void *__cache_alloc(kmem_cache_t *cachep, unsigned int __nocast fl
 		objp = cache_alloc_refill(cachep, flags);
 	}
 	local_irq_restore(save_flags);
-	objp = cache_alloc_debugcheck_after(cachep, flags, objp, __builtin_return_address(0));
+	objp = cache_alloc_debugcheck_after(cachep, flags, objp,
+					__builtin_return_address(0));
+	prefetchw(objp);
 	return objp;
 }