linux-kernel - [PATCH 22/22] slab: Use nr_online_nodes to check for a NUMA platform

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Message-Id: <1240408407-21848-23-git-send-email-mel@csn.ul.ie>
Date:	Wed, 22 Apr 2009 14:53:27 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Mel Gorman <mel@....ul.ie>,
	Linux Memory Management List <linux-mm@...ck.org>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 22/22] slab: Use nr_online_nodes to check for a NUMA platform

SLAB currently avoids checking a bitmap repeatedly by checking once and
storing a flag. When the addition of nr_online_nodes as a cheaper version
of num_online_nodes(), this check can be replaced by nr_online_nodes.

(Christoph did a patch that this is lifted almost verbatim from, hence the
first Signed-off-by. Christoph, can you confirm you're ok with that?)

Signed-off-by: Christoph Lameter <cl@...ux.com>
Signed-off-by: Mel Gorman <mel@....ul.ie>
---
 mm/slab.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 1c680e8..4d38dc2 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -892,7 +892,6 @@ static void __slab_error(const char *function, struct kmem_cache *cachep,
   */
 
 static int use_alien_caches __read_mostly = 1;
-static int numa_platform __read_mostly = 1;
 static int __init noaliencache_setup(char *s)
 {
 	use_alien_caches = 0;
@@ -1453,10 +1452,8 @@ void __init kmem_cache_init(void)
 	int order;
 	int node;
 
-	if (num_possible_nodes() == 1) {
+	if (num_possible_nodes() == 1)
 		use_alien_caches = 0;
-		numa_platform = 0;
-	}
 
 	for (i = 0; i < NUM_INIT_LISTS; i++) {
 		kmem_list3_init(&initkmem_list3[i]);
@@ -3579,7 +3576,7 @@ static inline void __cache_free(struct kmem_cache *cachep, void *objp)
 	 * variable to skip the call, which is mostly likely to be present in
 	 * the cache.
 	 */
-	if (numa_platform && cache_free_alien(cachep, objp))
+	if (nr_online_nodes > 1 && cache_free_alien(cachep, objp))
 		return;
 
 	if (likely(ac->avail < ac->limit)) {
-- 
1.5.6.5

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