2013-08-02 02:02:47

by Joonsoo Kim

Subject: [PATCH] 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.

Signed-off-by: Joonsoo Kim <[email protected]>

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 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)
{
int index;

- if (size > KMALLOC_MAX_SIZE) {
+ if (unlikely(size > KMALLOC_MAX_SIZE)) {
WARN_ON_ONCE(!(flags & __GFP_NOWARN));
return NULL;
}
--
1.7.9.5

2013-08-02 14:49:55

by Christoph Lameter (Ampere)

Subject: Re: [PATCH] mm, slab_common: add 'unlikely' to size check of kmalloc_slab()

On Fri, 2 Aug 2013, Joonsoo Kim wrote:

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

Acked-by: Christoph Lameter <[email protected]>