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Message-ID: <20140507104514.GC4757@esperanza>
Date: Wed, 7 May 2014 14:45:16 +0400
From: Vladimir Davydov <vdavydov@...allels.com>
To: Michal Hocko <mhocko@...e.cz>
CC: <akpm@...ux-foundation.org>, <hannes@...xchg.org>,
<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name
On Wed, May 07, 2014 at 11:51:27AM +0200, Michal Hocko wrote:
> On Wed 07-05-14 12:15:29, Vladimir Davydov wrote:
> [...]
> > static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
> > struct kmem_cache *root_cache)
> > {
> > + static char *memcg_name_buf;
> > struct kmem_cache *cachep;
> > int id;
>
> So we are relying on memcg_slab_mutex now, right? Worth a comment I
> suppose.
Sure. The updated version is attached below.
Thanks.
--
From: Vladimir Davydov <vdavydov@...allels.com>
Subject: [PATCH] memcg: get rid of memcg_create_cache_name
Instead of calling back to memcontrol.c from kmem_cache_create_memcg in
order to just create the name of a per memcg cache, let's allocate it in
place. We only need to pass the memcg name to kmem_cache_create_memcg
for that - everything else can be done in slab_common.c.
Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6c59056f4bc6..7b639ab48aa8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -501,8 +501,6 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order);
int memcg_cache_id(struct mem_cgroup *memcg);
-char *memcg_create_cache_name(struct mem_cgroup *memcg,
- struct kmem_cache *root_cache);
int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
struct kmem_cache *root_cache);
void memcg_free_cache_params(struct kmem_cache *s);
diff --git a/include/linux/slab.h b/include/linux/slab.h
index ecbec9ccb80d..86e5b26fbdab 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -117,7 +117,8 @@ struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
void (*)(void *));
#ifdef CONFIG_MEMCG_KMEM
struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *,
- struct kmem_cache *);
+ struct kmem_cache *,
+ const char *);
#endif
void kmem_cache_destroy(struct kmem_cache *);
int kmem_cache_shrink(struct kmem_cache *);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f381239ab402..9ff3742f4154 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3101,29 +3101,6 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
return 0;
}
-char *memcg_create_cache_name(struct mem_cgroup *memcg,
- struct kmem_cache *root_cache)
-{
- static char *buf;
-
- /*
- * We need a mutex here to protect the shared buffer. Since this is
- * expected to be called only on cache creation, we can employ the
- * slab_mutex for that purpose.
- */
- lockdep_assert_held(&slab_mutex);
-
- if (!buf) {
- buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
- if (!buf)
- return NULL;
- }
-
- cgroup_name(memcg->css.cgroup, buf, NAME_MAX + 1);
- return kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
- memcg_cache_id(memcg), buf);
-}
-
int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
struct kmem_cache *root_cache)
{
@@ -3164,6 +3141,7 @@ void memcg_free_cache_params(struct kmem_cache *s)
static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
struct kmem_cache *root_cache)
{
+ static char *memcg_name_buf; /* protected by memcg_slab_mutex */
struct kmem_cache *cachep;
int id;
@@ -3179,7 +3157,14 @@ static void memcg_kmem_create_cache(struct mem_cgroup *memcg,
if (cache_from_memcg_idx(root_cache, id))
return;
- cachep = kmem_cache_create_memcg(memcg, root_cache);
+ if (!memcg_name_buf) {
+ memcg_name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+ if (!memcg_name_buf)
+ return;
+ }
+
+ cgroup_name(memcg->css.cgroup, memcg_name_buf, NAME_MAX + 1);
+ cachep = kmem_cache_create_memcg(memcg, root_cache, memcg_name_buf);
/*
* If we could not create a memcg cache, do not complain, because
* that's not critical at all as we can always proceed with the root
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 7e348cff814d..32175617cb75 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -264,13 +264,15 @@ EXPORT_SYMBOL(kmem_cache_create);
* kmem_cache_create_memcg - Create a cache for a memory cgroup.
* @memcg: The memory cgroup the new cache is for.
* @root_cache: The parent of the new cache.
+ * @memcg_name: The name of the memory cgroup (used for naming the new cache).
*
* This function attempts to create a kmem cache that will serve allocation
* requests going from @memcg to @root_cache. The new cache inherits properties
* from its parent.
*/
struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
- struct kmem_cache *root_cache)
+ struct kmem_cache *root_cache,
+ const char *memcg_name)
{
struct kmem_cache *s = NULL;
char *cache_name;
@@ -280,7 +282,8 @@ struct kmem_cache *kmem_cache_create_memcg(struct mem_cgroup *memcg,
mutex_lock(&slab_mutex);
- cache_name = memcg_create_cache_name(memcg, root_cache);
+ cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
+ memcg_cache_id(memcg), memcg_name);
if (!cache_name)
goto out_unlock;
--
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