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

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Message-ID: <52F3AC9A.7050600@parallels.com>
Date:	Thu, 6 Feb 2014 19:39:06 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Michal Hocko <mhocko@...e.cz>
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 02/06/2014 07:29 PM, Michal Hocko wrote:
> 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.

Never mind.

> Maybe it is worth mentioning in the changelog?

Hmm, changelog? This hunk was there from the very beginning :-/

Anyway, I'm going to expand this patch's comment, because it's too short
and difficult to understand.

Thanks.
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