mm, slab: maintain total slab count instead of active count

Rather than tracking the number of active slabs for each node, track the
total number of slabs.  This is a minor improvement that avoids active
slab tracking when a slab goes from free to partial or partial to free.

For slab debugging, this also removes an explicit free count since it
can easily be inferred by the difference in number of total objects and
number of active objects.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1612042020110.115755@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Suggested-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/mm/slab.h b/mm/slab.h
index 26123c512fee..de6579dc362c 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -447,8 +447,8 @@ struct kmem_cache_node {
         struct list_head slabs_partial; /* partial list first, better asm code */
         struct list_head slabs_full;
         struct list_head slabs_free;
-        unsigned long active_slabs;     /* length of slabs_partial+slabs_full */
-        unsigned long free_slabs;       /* length of slabs_free */
+        unsigned long total_slabs;      /* length of all slab lists */
+        unsigned long free_slabs;       /* length of free slab list only */
         unsigned long free_objects;
         unsigned int free_limit;
         unsigned int colour_next;       /* Per-node cache coloring */