skip cache_free_alien() on non NUMA

From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>

Set use_alien_caches to 0 on non NUMA platforms.  And avoid calling the
cache_free_alien() when use_alien_caches is not set.  This will avoid the
cache miss that happens while dereferencing slabp to get nodeid.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slab.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Index: linux/mm/slab.c
===================================================================
--- linux.orig/mm/slab.c
+++ linux/mm/slab.c
@@ -1146,7 +1146,7 @@ static inline int cache_free_alien(struc
 	 * Make sure we are not freeing a object from another node to the array
 	 * cache on this cpu.
 	 */
-	if (likely(slabp->nodeid == node) || unlikely(!use_alien_caches))
+	if (likely(slabp->nodeid == node))
 		return 0;
 
 	l3 = cachep->nodelists[node];
@@ -1394,6 +1394,9 @@ void __init kmem_cache_init(void)
 	int order;
 	int node;
 
+	if (num_possible_nodes() == 1)
+		use_alien_caches = 0;
+
 	for (i = 0; i < NUM_INIT_LISTS; i++) {
 		kmem_list3_init(&initkmem_list3[i]);
 		if (i < MAX_NUMNODES)
@@ -3563,7 +3566,7 @@ static inline void __cache_free(struct k
 	check_irq_off();
 	objp = cache_free_debugcheck(cachep, objp, __builtin_return_address(0));
 
-	if (cache_free_alien(cachep, objp))
+	if (use_alien_caches && cache_free_alien(cachep, objp))
 		return;
 
 	if (likely(ac->avail < ac->limit)) {