linux-kernel - Re: PROBLEM: Crash cgdeleting empty memory cgroups with memory.kmem.limit_in

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Message-ID: <512640DE.4050201@parallels.com>
Date:	Thu, 21 Feb 2013 19:44:30 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Tejun Heo <tj@...nel.org>
CC:	<containers@...ts.linux-foundation.org>,
	<linux-kernel@...r.kernel.org>, Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Steffen Michalke <StMichalke@....de>
Subject: Re: PROBLEM: Crash cgdeleting empty memory cgroups with memory.kmem.limit_in_bytes
 set

On 02/21/2013 03:22 PM, Glauber Costa wrote:
> On 02/21/2013 03:00 AM, Tejun Heo wrote:
>> (cc'ing cgroup / memcg people and quoting whole body)
>>
>> Looks like something is going wrong with memcg cache destruction.
>> Glauber, any ideas?  Also, can we please not use names as generic as
>> kmem_cache_destroy_work_func for something specific to memcg?  How
>> about something like memcg_destroy_cache_workfn?
>>
>> Thanks.
> 
> Steffen,
> 
> Is there any chance you could test that using SLAB instead of SLUB?
> I haven't manage to reproduce it yet, but I am working on some theories
> about why this is happening. If I could at least know if this is likely
> a cache problem vs a inner-memcg problem, that would help. The calltrace
> is not incredibly helpful, but it does indicate that the problem happens
> when freeing cache objects.
> 

Update:

I've already reproduced this and determined this is a problem that
plagues slub only, most likely due to initialization of the node caches.
But I still don't know for sure the exact location. Expect a patch by
tomorrow.

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