linux-kernel - Re: 2.6.31 and OOM killer = bug?

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Date:	Mon, 15 Feb 2010 10:19:17 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Anton Starikov <ant.starikov@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: 2.6.31 and OOM killer = bug?

On Mon, 15 Feb 2010 00:43:02 +0100
Anton Starikov <ant.starikov@...il.com> wrote:

> Hi,
> 
> The setup:
> is 16-core opteron node, diskless with NFS root, swapless, 64GB of RAM. Operating under OpenSUSE 11.2. With kernel version 2.6.31. Although it isn't vanilla, I think probably more right is to submit this into LKML.
> 

At first, what is the version of kernel you are comparing with ? 2.6.22?(If OpenSuse10)
If so, many changes since that..

> The problem:
> On this node user run MPI job with 16 processes, local job by using shared memory communication.  
> At some point this processes are trying to use more memory that available.
> Normally, all of them or part of them would be killed by OOM killer, and it use to work for years over many versions of kernel.
> 
> Now, with fresh setup I got something new. OOM tried to kill, but didn't succeed, and even more, brought system in unusable state. All those processes are locked and un-killable. some of other processes are also locked and un-killable/inaccessible. kswapd consume 100% CPU (which I think is expected behavior when there is no free memory). 
> No free memory obviously, cause all original processes are still in memory.
> 
> I tried to test OOM behavior and it always happens like that now.
> 
> Here I attach full gzipped log of all related information captured by logserver (sent by logserver and netconsole, so it can be partly doubled). Sorry that it is too big, but I didn't know what information can be important.
> 

Anyway, I think it's not appreciated to depend on OOM-Kill on swapless-system.
I recommend you to use cgroup "memory" to encapsulate your apps (but please check
the performance regression can be seen or not..)

Thanks,
-Kame

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