[RFC PATCH v2 03/14] slub: Sort slab cache list

[Tobin C. Harding]

It is advantageous to have all defragmentable slabs together at the
beginning of the list of slabs so that there is no need to scan the
complete list. Put defragmentable caches first when adding a slab cache
and others last.

Co-developed-by: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Tobin C. Harding <tobin@xxxxxxxxxx>
---
 mm/slab_common.c | 2 +-
 mm/slub.c        | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 58251ba63e4a..db5e9a0b1535 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -393,7 +393,7 @@ static struct kmem_cache *create_cache(const char *name,
 		goto out_free_cache;
 
 	s->refcount = 1;
-	list_add(&s->list, &slab_caches);
+	list_add_tail(&s->list, &slab_caches);
 	memcg_link_cache(s);
 out:
 	if (err)
diff --git a/mm/slub.c b/mm/slub.c
index ae44d640b8c1..f6b0e4a395ef 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4342,6 +4342,8 @@ void kmem_cache_setup_mobility(struct kmem_cache *s,
 		return;
 	}
 
+	mutex_lock(&slab_mutex);
+
 	s->isolate = isolate;
 	s->migrate = migrate;
 
@@ -4350,6 +4352,10 @@ void kmem_cache_setup_mobility(struct kmem_cache *s,
 	 * to disable fast cmpxchg based processing.
 	 */
 	s->flags &= ~__CMPXCHG_DOUBLE;
+
+	list_move(&s->list, &slab_caches);	/* Move to top */
+
+	mutex_unlock(&slab_mutex);
 }
 EXPORT_SYMBOL(kmem_cache_setup_mobility);
 
-- 
2.21.0