GitHub-Mirror/linux-bl808
2
0
Fork 0
mirror of https://github.com/Fishwaldo/linux-bl808.git synced 2025-06-17 20:25:19 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

memcg: add rwsem to synchronize against memcg_caches arrays relocation

Browse source 
We need a stable value of memcg_nr_cache_ids in kmem_cache_create()
(memcg_alloc_cache_params() wants it for root caches), where we only
hold the slab_mutex and no memcg-related locks.  As a result, we have to
update memcg_nr_cache_ids under the slab_mutex, which we can only take
on the slab's side (see memcg_update_array_size).  This looks awkward
and will become even worse when per-memcg list_lru is introduced, which
also wants stable access to memcg_nr_cache_ids.

To get rid of this dependency between the memcg_nr_cache_ids and the
slab_mutex, this patch introduces a special rwsem.  The rwsem is held
for writing during memcg_caches arrays relocation and memcg_nr_cache_ids
updates.  Therefore one can take it for reading to get a stable access
to memcg_caches arrays and/or memcg_nr_cache_ids.

Currently the semaphore is taken for reading only from
kmem_cache_create, right before taking the slab_mutex, so right now
there's no much point in using rwsem instead of mutex.  However, once
list_lru is made per-memcg it will allow list_lru initializations to
proceed concurrently.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.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>
This commit is contained in:
Vladimir Davydov 2015-02-12 14:59:01 -08:00 • committed by Linus Torvalds
parent dbcf73e26c
commit 05257a1a3d
3 changed files with 33 additions and 17 deletions
Download patch file Download diff file Expand all files Collapse all files

12
include/linux/memcontrol.h
View file

@ -399,6 +399,8 @@ static inline void sock_release_memcg(struct sock *sk)
extern struct static_key memcg_kmem_enabled_key;
extern int memcg_nr_cache_ids;
extern void memcg_get_cache_ids(void);
extern void memcg_put_cache_ids(void);
/*
* Helper macro to loop through all memcg-specific caches. Callers must still
@ -434,8 +436,6 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order);
int memcg_cache_id(struct mem_cgroup *memcg);
void memcg_update_array_size(int num_groups);
struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep);
void __memcg_kmem_put_cache(struct kmem_cache *cachep);
@ -569,6 +569,14 @@ static inline int memcg_cache_id(struct mem_cgroup *memcg)
return -1;
}
static inline void memcg_get_cache_ids(void)
{
}
static inline void memcg_put_cache_ids(void)
{
}
static inline struct kmem_cache *
memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
{