linux-kernel - Re: doing lots of disk writes causes oom killer to kill processes

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Date:	Thu, 5 Sep 2013 12:12:10 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Hillf Danton <dhillf@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>
Subject: Re: doing lots of disk writes causes oom killer to kill processes

Hello

On 26 August 2013 15:51, Michal Suchanek <hramrach@...il.com> wrote:
> On 12 March 2013 03:15, Hillf Danton <dhillf@...il.com> wrote:
>>>On 11 March 2013 13:15, Michal Suchanek <hramrach@...il.com> wrote:
>>>>On 8 February 2013 17:31, Michal Suchanek <hramrach@...il.com> wrote:
>>>> Hello,
>>>>
>>>> I am dealing with VM disk images and performing something like wiping
>>>> free space to prepare image for compressing and storing on server or
>>>> copying it to external USB disk causes
>>>>
>>>> 1) system lockup in order of a few tens of seconds when all CPU cores
>>>> are 100% used by system and the machine is basicaly unusable
>>>>
>>>> 2) oom killer killing processes
>>>>
>>>> This all on system with 8G ram so there should be plenty space to work with.
>>>>
>>>> This happens with kernels 3.6.4 or 3.7.1
>>>>
>>>> With earlier kernel versions (some 3.0 or 3.2 kernels) this was not a
>>>> problem even with less ram.
>>>>
>>>> I have  vm.swappiness = 0 set for a long  time already.
>>>>
>>>>
>>>I did some testing with 3.7.1 and with swappiness as much as 75 the
>>>kernel still causes all cores to loop somewhere in system when writing
>>>lots of data to disk.
>>>
>>>With swappiness as much as 90 processes still get killed on large disk writes.
>>>
>>>Given that the max is 100 the interval in which mm works at all is
>>>going to be very narrow, less than 10% of the paramater range. This is
>>>a severe regression as is the cpu time consumed by the kernel.
>>>
>>>The io scheduler is the default cfq.
>>>
>>>If you have any idea what to try other than downgrading to an earlier
>>>unaffected kernel I would like to hear.
>>>
>> Can you try commit 3cf23841b4b7(mm/vmscan.c: avoid possible
>> deadlock caused by too_many_isolated())?
>>
>> Or try 3.8 and/or 3.9, additionally?
>>
>
> Hello,
>
> with deadline IO scheduler I experience this issue less often but it
> still happens.
>
> I am on 3.9.6 Debian kernel so 3.8 did not fix this problem.
>
> Do you have some idea what to log so that useful information about the
> lockup is gathered?
>

This appears to be fixed in vanilla 3.11 kernel.

I still get short intermittent lockups and cpu usage spikes up to 20%
on a core but nowhere near the minute+ long lockups with all cores
100% on earlier kernels.

Thanks

Michal
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