linux-kernel - Re: [PATCH 2/8] memcg, slab: remove cgroup name from memcg cache names

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Message-ID: <20140204144526.GG4890@dhcp22.suse.cz>
Date:	Tue, 4 Feb 2014 15:45:26 +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 2/8] memcg, slab: remove cgroup name from memcg cache
 names

On Sun 02-02-14 20:33:47, Vladimir Davydov wrote:
> The cgroup name is not informative at all in case the cgroup hierarchy
> is not flat. Besides, we can always find the memcg a particular cache
> belongs to by its kmemcg id, which is now exported via "memory.kmem.id"
> cgroup fs file for each memcg.
> 
> So let's remove the cgroup name part from kmem caches names - it will
> greatly simplify the call paths and make the code look clearer.
> 
> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>

I guess this one doesn't make much sense withou 1/8, right?

> ---
>  mm/memcontrol.c  |   63 +++++++++++++-----------------------------------------
>  mm/slab_common.c |    6 +++++-
>  2 files changed, 20 insertions(+), 49 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 91d242707404..3351c5b5486d 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3405,44 +3405,6 @@ 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;
> @@ -3489,12 +3451,6 @@ 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;
> @@ -3512,13 +3468,24 @@ 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 1ec3c619ba04..152d9b118b7a 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -213,7 +213,11 @@ 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 = kstrdup(name, GFP_KERNEL);
> +	else
> +		s->name = kasprintf(GFP_KERNEL, "%s:%d",
> +				    name, memcg_cache_id(memcg));
>  	if (!s->name)
>  		goto out_free_cache;
>  
> -- 
> 1.7.10.4
> 

-- 
Michal Hocko
SUSE Labs
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