linux-kernel - Re: [PATCH 3/8] memcg, slab: never try to merge memcg caches

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Message-ID: <20140206152944.GG20269@dhcp22.suse.cz>
Date:	Thu, 6 Feb 2014 16:29:44 +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 3/8] memcg, slab: never try to merge memcg caches

On Thu 06-02-14 18:15:50, Vladimir Davydov wrote:
> On 02/06/2014 06:07 PM, Michal Hocko wrote:
> > On Tue 04-02-14 19:27:19, Vladimir Davydov wrote:
> > [...]
> >> What does this patch change? Actually, it introduces no functional
> >> changes - it only remove the code trying to find an alias for a memcg
> >> cache, because it will fail anyway. So this is rather a cleanup.
> > But this also means that two different memcgs might share the same cache
> > and so the pages for that cache, no?
> 
> No, because in this patch I explicitly forbid to merge memcg caches by
> this hunk:
> 
> @@ -200,9 +200,11 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg,
> const char *name, size_t size,
>       */
>      flags &= CACHE_CREATE_MASK;
>  
> -    s = __kmem_cache_alias(memcg, name, size, align, flags, ctor);
> -    if (s)
> -        goto out_unlock;
> +    if (!memcg) {
> +        s = __kmem_cache_alias(name, size, align, flags, ctor);
> +        if (s)
> +            goto out_unlock;
> +    }

Ohh, that was the missing part. Thanks and sorry I have missed it. Maybe
it is worth mentioning in the changelog?
-- 
Michal Hocko
SUSE Labs
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