mm, slab_common: add 'unlikely' to size check of kmalloc_slab()

Size is usually below than KMALLOC_MAX_SIZE.
If we add a 'unlikely' macro, compiler can make better code.

Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 538bade..f0410eb 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -373,7 +373,7 @@
 {
 	int index;
 
-	if (size > KMALLOC_MAX_SIZE) {
+	if (unlikely(size > KMALLOC_MAX_SIZE)) {
 		WARN_ON_ONCE(!(flags & __GFP_NOWARN));
 		return NULL;
 	}