linux-kernel - Re: Kernel 2.6.29 runs out of memory and hangs.

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Message-ID: <40a4ed590904250132o63e715cbvaccf5aac82265cd@mail.gmail.com>
Date:	Sat, 25 Apr 2009 10:32:48 +0200
From:	Zeno Davatz <zdavatz@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	linux-kernel@...r.kernel.org, Hannes Wyss <hwyss@...see.com>
Subject: Re: Kernel 2.6.29 runs out of memory and hangs.

Dear David

On Fri, Apr 24, 2009 at 9:26 PM, David Rientjes <rientjes@...gle.com> wrote:
> On Fri, 24 Apr 2009, Zeno Davatz wrote:
>
>> > These types of livelocks are possible with the oom killer when a task
>> > fails to exit, one possible way to fix that is to introduce an oom killer
>> > timeout such that if a task fails to exit for a pre-defined period of
>> > time, the oom killer will choose to kill another task in the hopes of
>> > future memory freeing.  The problem with that approach, however, is that
>> > the hung task can consume an enormous amount of memory that will never be
>> > freed.
>>
>> Thanks for the hint! Is there another solution as well? Any
>> Kernel-Upgrades in the Pipeline? What does Linus think about this?
>>
>
> I had a patchset that added a timeout for oom killed tasks now that the
> entire oom killer is serialized, but it only really works well if your
> memory is so partitioned (such as with cpusets or the memory controller)
> that it actually makes sense to continue.  With global system-wide ooms
> such as yours, it would only result in a long chain of kills with no
> positive outcome.

Couldn't you start killing processes at an earlier stage? It seems to
me that the stage when processes are being killed by oom_killer is a
bit late in the game, when the machine is anyway very close to the
freezing point. I mean we had these messages of oom_kill several times
in our /var/log/kernel/current over a distributed amount of time.

Of course we now also set a roadblock to our main application
(http://ch.oddb.org) that kills the application if it uses more then
10 GB of memory.

Best
Zeno
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