linux-kernel - [PATCH 4/5] mm/slab: noinline __ac_put

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Date:	Thu, 21 Aug 2014 17:09:21 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH 4/5] mm/slab: noinline __ac_put_obj()

Our intention of __ac_put_obj() is that it doesn't affect anything if
sk_memalloc_socks() is disabled. But, because __ac_put_obj() is too small,
compiler inline it to ac_put_obj() and affect code size of free path.
This patch add noinline keyword for __ac_put_obj() not to distrupt normal
free path at all.

<Before>
nm -S slab-orig.o |
	grep -e "t cache_alloc_refill" -e "T kfree" -e "T kmem_cache_free"

0000000000001e80 00000000000002f5 t cache_alloc_refill
0000000000001230 0000000000000258 T kfree
0000000000000690 000000000000024c T kmem_cache_free

<After>
nm -S slab-patched.o |
	grep -e "t cache_alloc_refill" -e "T kfree" -e "T kmem_cache_free"

0000000000001e00 00000000000002e5 t cache_alloc_refill
00000000000011e0 0000000000000228 T kfree
0000000000000670 0000000000000216 T kmem_cache_free

cache_alloc_refill: 0x2f5->0x2e5
kfree: 0x256->0x228
kmem_cache_free: 0x24c->0x216

code size of each function is reduced slightly.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
 mm/slab.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index d364e3f..c9f137f 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -785,8 +785,8 @@ static inline void *ac_get_obj(struct kmem_cache *cachep,
 	return objp;
 }
 
-static void *__ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac,
-								void *objp)
+static noinline void *__ac_put_obj(struct kmem_cache *cachep,
+			struct array_cache *ac, void *objp)
 {
 	if (unlikely(pfmemalloc_active)) {
 		/* Some pfmemalloc slabs exist, check if this is one */
-- 
1.7.9.5

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