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Date: Wed, 7 May 2014 13:53:52 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>, <hannes@cmpxchg.org>,
        <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [PATCH -mm 1/2] memcg: get rid of memcg_create_cache_name
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On Wed, 7 May 2014 14:45:16 +0400 Vladimir Davydov <vdavydov@parallels.com> wrote:

> @@ -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;
> +	}

Does this have any meaningful advantage over the simpler

	static char memcg_name_buf[NAME_MAX + 1];

?

I guess it saves a scrap of memory if the machine never uses memcg's.