SLUB defrag: Only scan the defraggable caches on kmem_cache_defrag.

Make sure that the defragmentable slab caches are at the top of the list
of slab caches. We can then stop scanning if we find a non defragmentable
slabcache on the slab list.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 mm/slub.c |   20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

Index: linux-2.6.22-rc6-mm1/mm/slub.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/mm/slub.c	2007-07-04 11:06:25.000000000 -0700
+++ linux-2.6.22-rc6-mm1/mm/slub.c	2007-07-04 11:07:26.000000000 -0700
@@ -2280,7 +2280,7 @@ static struct kmem_cache *create_kmalloc
 			flags, NULL, &slub_default_ops))
 		goto panic;
 
-	list_add(&s->list, &slab_caches);
+	list_add_tail(&s->list, &slab_caches);
 	up_write(&slub_lock);
 	if (sysfs_slab_add(s))
 		goto panic;
@@ -2737,10 +2737,11 @@ int kmem_cache_defrag(int node)
 	list_for_each_entry(s, &slab_caches, list) {
 
 		/*
-		 * The slab cache must have defrag methods.
+		 * The list of slab cachess is sorted so that we only scan
+		 * have to scan the one capable of defragmentation.
 		 */
-		if (!s->ops || !s->ops->kick)
-			continue;
+		if (!s->ops->kick)
+			break;
 
 		scratch = kmalloc(sizeof(struct list_head) * s->objects,
 								GFP_KERNEL);
@@ -2946,7 +2947,16 @@ struct kmem_cache *kmem_cache_create(con
 	if (s) {
 		if (kmem_cache_open(s, GFP_KERNEL, name,
 				size, align, flags, ctor, ops)) {
-			list_add(&s->list, &slab_caches);
+
+			/*
+			 * Reclaimable slabs first because we may have
+			 * to scan them repeatedly.
+			 */
+			if (ops->kick)
+				list_add(&s->list, &slab_caches);
+			else
+				list_add_tail(&s->list, &slab_caches);
+
 			up_write(&slub_lock);
 			raise_kswapd_order(s->order);