netdev - Re: kernel 2.6.37 : oops in cleanup

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Date:	Wed, 02 Feb 2011 16:04:12 +0100
From:	Yann Dupont <Yann.Dupont@...v-nantes.fr>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: kernel 2.6.37 : oops in cleanup_once

Le 02/02/2011 15:53, Eric Dumazet a écrit :
> Le mercredi 02 février 2011 à 14:08 +0100, Yann Dupont a écrit :
>> Le 02/02/2011 12:24, Eric Dumazet a écrit :
>>> Le mercredi 02 février 2011 à 11:52 +0100, Eric Dumazet a écrit :
>>>> Le mercredi 02 février 2011 à 09:53 +0100, Yann Dupont a écrit :
>>>>> Hello.
>>>>> We recently upgraded one machine with vanilla 2.6.37, and experienced 2
>>>>> kernel oops since. Each oops is after ~1 week of uptime.
>>>>> The last oops was last night but we didn't had any trace.
>>> oops, 2.6.37 "only"
>>>
>>>> Yes this is a known problem.
>>>>
>>>> Please try commit 3408404a4c2a4eead9d73b0bbbfe3f225b65f492
>>>> (inetpeer: Use correct AVL tree base pointer in inet_getpeer())
>>>>
>>>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=3408404a4c2a4eead9d73b0bbbfe3f225b65f492
>>>>
>>>> I believe David will send it to stable team shortly, if not already
>>>> done :)
>>> Please ignore, this patch was for linux-2.6 tree, 2.6.37 was not
>>> affected by the problem.
>>>
>>> So its another problem... Is there anything particular you do on this
>>> machine ?
>>>
>>>
>>>
>>>
>> Nothing really special there, we run a lot (20) of KVM guest (mainly
>> linux firewalls for lots of differents vlan), so we have a lot of
>> bridges vlan&  tun/tap.
>> Oh, and CONFIG_BRIDGE_IGMP_SNOOPING is set to n (because of  the other
>> bug already sent to netdev - more to come on next mail)
>>
>> Hard to say if this BUG is new in 2.6.37. This host was running fine
>> with 2.6.34.2 since August 2010.
>> Bisecting will be hard due to the time to trigger the bug (and the fact
>> that this machine is a production machine)
>>
>> Anyway, I can test with a specific kernel version if you suspect something.
>>
> I suspect a mem corruption from another layer (not inetpeer)
>
> Unfortunately many kmem caches share the "64 bytes" cache.
>
> Could you please add "slub_nomerge" on your boot command ?
>
Ok, will do it at 18:30 CET (to minimize impact)
It the suspected bug SLUB related ?

The 2.6.34.2 kernel previously used on that server used SLAB.


2 questions :
-How can I be sure slub_nomerge is active ? Boot message ?
-Is there a very severe impact on performance ?

Regards,

-- 
Yann Dupont - Service IRTS, DSI Université de Nantes
Tel : 02.53.48.49.20 - Mail/Jabber : Yann.Dupont@...v-nantes.fr

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