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Date: Tue, 4 Feb 2014 16:33:27 +0100
From: Michal Hocko <mhocko@...e.cz>
To: Vladimir Davydov <vdavydov@...allels.com>
Cc: akpm@...ux-foundation.org, rientjes@...gle.com, penberg@...nel.org,
cl@...ux.com, glommer@...il.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, devel@...nvz.org
Subject: Re: [PATCH] memcg, slab: cleanup memcg cache creation
On Tue 04-02-14 11:39:07, Vladimir Davydov wrote:
> This patch cleanups the memcg cache creation path as follows:
> - Move memcg cache name creation to a separate function to be called
> from kmem_cache_create_memcg(). This allows us to get rid of the
> mutex protecting the temporary buffer used for the name formatting,
> because the whole cache creation path is protected by the slab_mutex.
> - Get rid of memcg_create_kmem_cache(). This function serves as a proxy
> to kmem_cache_create_memcg(). After separating the cache name
> creation path, it would be reduced to a function call, so let's
> inline it.
OK, this looks better but it will still conflict with Tejun's cleanup
now? Can we wait until mmotm settles down a bit and sees those changes?
Maybe we can get rid of the static buffer altogether?
> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
> ---
> include/linux/memcontrol.h | 9 +++++
> mm/memcontrol.c | 89 ++++++++++++++++++++------------------------
> mm/slab_common.c | 5 ++-
> 3 files changed, 54 insertions(+), 49 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index abd0113b6620..84e4801fc36c 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -497,6 +497,9 @@ void __memcg_kmem_commit_charge(struct page *page,
> 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);
> @@ -641,6 +644,12 @@ static inline int memcg_cache_id(struct mem_cgroup *memcg)
> return -1;
> }
>
> +static inline char *memcg_create_cache_name(struct mem_cgroup *memcg,
> + struct kmem_cache *root_cache)
> +{
> + return NULL;
> +}
> +
> static inline int memcg_alloc_cache_params(struct mem_cgroup *memcg,
> struct kmem_cache *s, struct kmem_cache *root_cache)
> {
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 53385cd4e6f0..43e08b7bb365 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3193,6 +3193,32 @@ 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 = NULL;
> +
> + /*
> + * 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(PATH_MAX, GFP_KERNEL);
> + if (!buf)
> + return NULL;
> + }
> +
> + rcu_read_lock();
> + snprintf(buf, PATH_MAX, "%s(%d:%s)", root_cache->name,
> + memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup));
> + rcu_read_unlock();
> +
> + return kstrdup(buf, GFP_KERNEL);
> +}
> +
> int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
> struct kmem_cache *root_cache)
> {
> @@ -3397,44 +3423,6 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
> schedule_work(&cachep->memcg_params->destroy);
> }
>
> -static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
> - struct kmem_cache *s)
> -{
> - struct kmem_cache *new = NULL;
> - static char *tmp_name = NULL;
> - static DEFINE_MUTEX(mutex); /* protects tmp_name */
> -
> - BUG_ON(!memcg_can_account_kmem(memcg));
> -
> - mutex_lock(&mutex);
> - /*
> - * kmem_cache_create_memcg duplicates the given name and
> - * cgroup_name for this name requires RCU context.
> - * This static temporary buffer is used to prevent from
> - * pointless shortliving allocation.
> - */
> - if (!tmp_name) {
> - tmp_name = kmalloc(PATH_MAX, GFP_KERNEL);
> - if (!tmp_name)
> - goto out;
> - }
> -
> - rcu_read_lock();
> - snprintf(tmp_name, PATH_MAX, "%s(%d:%s)", s->name,
> - memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup));
> - rcu_read_unlock();
> -
> - new = kmem_cache_create_memcg(memcg, tmp_name, s->object_size, s->align,
> - (s->flags & ~SLAB_PANIC), s->ctor, s);
> - if (new)
> - new->allocflags |= __GFP_KMEMCG;
> - else
> - new = s;
> -out:
> - mutex_unlock(&mutex);
> - return new;
> -}
> -
> void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
> {
> struct kmem_cache *c;
> @@ -3481,12 +3469,6 @@ void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
> mutex_unlock(&activate_kmem_mutex);
> }
>
> -struct create_work {
> - struct mem_cgroup *memcg;
> - struct kmem_cache *cachep;
> - struct work_struct work;
> -};
> -
> static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
> {
> struct kmem_cache *cachep;
> @@ -3504,13 +3486,24 @@ static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
> mutex_unlock(&memcg->slab_caches_mutex);
> }
>
> +struct create_work {
> + struct mem_cgroup *memcg;
> + struct kmem_cache *cachep;
> + struct work_struct work;
> +};
> +
> static void memcg_create_cache_work_func(struct work_struct *w)
> {
> - struct create_work *cw;
> + struct create_work *cw = container_of(w, struct create_work, work);
> + struct mem_cgroup *memcg = cw->memcg;
> + struct kmem_cache *s = cw->cachep;
> + struct kmem_cache *new;
>
> - cw = container_of(w, struct create_work, work);
> - memcg_create_kmem_cache(cw->memcg, cw->cachep);
> - css_put(&cw->memcg->css);
> + new = kmem_cache_create_memcg(memcg, s->name, s->object_size, s->align,
> + (s->flags & ~SLAB_PANIC), s->ctor, s);
> + if (new)
> + new->allocflags |= __GFP_KMEMCG;
> + css_put(&memcg->css);
> kfree(cw);
> }
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index e77b51eb7347..11857abf7057 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -215,7 +215,10 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
> s->align = calculate_alignment(flags, align, size);
> s->ctor = ctor;
>
> - s->name = kstrdup(name, GFP_KERNEL);
> + if (memcg)
> + s->name = memcg_create_cache_name(memcg, parent_cache);
> + else
> + s->name = kstrdup(name, GFP_KERNEL);
> if (!s->name)
> goto out_free_cache;
>
> --
> 1.7.10.4
>
--
Michal Hocko
SUSE Labs
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