From 943a451a87d229ca564a27274b58eaeae35fde5d Mon Sep 17 00:00:00 2001
From: Glauber Costa <glommer@parallels.com>
Date: Tue, 18 Dec 2012 14:23:03 -0800
Subject: slab: propagate tunable values

SLAB allows us to tune a particular cache behavior with tunables.  When
creating a new memcg cache copy, we'd like to preserve any tunables the
parent cache already had.

This could be done by an explicit call to do_tune_cpucache() after the
cache is created.  But this is not very convenient now that the caches are
created from common code, since this function is SLAB-specific.

Another method of doing that is taking advantage of the fact that
do_tune_cpucache() is always called from enable_cpucache(), which is
called at cache initialization.  We can just preset the values, and then
things work as expected.

It can also happen that a root cache has its tunables updated during
normal system operation.  In this case, we will propagate the change to
all caches that are already active.

This change will require us to move the assignment of root_cache in
memcg_params a bit earlier.  We need this to be already set - which
memcg_kmem_register_cache will do - when we reach __kmem_cache_create()

Signed-off-by: Glauber Costa <glommer@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Frederic Weisbecker <fweisbec@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: JoonSoo Kim <js1304@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Rik van Riel <riel@redhat.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/slab.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'mm/slab.h')

diff --git a/mm/slab.h b/mm/slab.h
index ec5dae1c8e75..34a98d642196 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -155,6 +155,13 @@ static inline struct kmem_cache *cache_from_memcg(struct kmem_cache *s, int idx)
 {
 	return s->memcg_params->memcg_caches[idx];
 }
+
+static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
+{
+	if (is_root_cache(s))
+		return s;
+	return s->memcg_params->root_cache;
+}
 #else
 static inline bool is_root_cache(struct kmem_cache *s)
 {
@@ -190,6 +197,11 @@ static inline struct kmem_cache *cache_from_memcg(struct kmem_cache *s, int idx)
 {
 	return NULL;
 }
+
+static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
+{
+	return s;
+}
 #endif
 
 static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
-- 
cgit v1.2.1