slub: Disable NUMA remote node defragmentation by default

Switch remote node defragmentation off by default. The current settings can
cause excessive node local allocations with hackbench:

  SLAB:

    % cat /proc/meminfo
    MemTotal:        7701760 kB
    MemFree:         5940096 kB
    Slab:             123840 kB

  SLUB:

    % cat /proc/meminfo
    MemTotal:        7701376 kB
    MemFree:         4740928 kB
    Slab:            1591680 kB

[Note: this feature is not related to slab defragmentation.]

You can find the original discussion here:

  http://lkml.org/lkml/2008/8/4/308Reported-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Tested-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NChristoph Lameter <cl@linux-foundation.org>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>

mm/slub.c

@@ -2312,7 +2312,7 @@ static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags,
 
 	s->refcount = 1;
 #ifdef CONFIG_NUMA
-	s->remote_node_defrag_ratio = 100;
+	s->remote_node_defrag_ratio = 1000;
 #endif
 	if (!init_kmem_cache_nodes(s, gfpflags & ~SLUB_DMA))
 		goto error;
@@ -4058,7 +4058,7 @@ static ssize_t remote_node_defrag_ratio_store(struct kmem_cache *s,
 	if (err)
 		return err;
 
-	if (ratio < 100)
+	if (ratio <= 100)
 		s->remote_node_defrag_ratio = ratio * 10;
 
 	return length;