On Wed 07-05-14 14:45:16, Vladimir Davydov wrote:
[...]
> From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
>
> 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;
>
--
Michal Hocko
SUSE Labs
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