Re: running of out memory => kernel crash
From: Mahmood Naderan
Date: Thu Aug 11 2011 - 03:07:18 EST
>The default behavior is to kill all eligible and unkillable threads until
>there are none left to sacrifice (i.e. all kthreads and OOM_DISABLE).
In a simple test with virtualbox, I reduced the amount of ram to 300MB.
Then I ran "swapoff -a" and opened some applications. I noticed that the free
spaces is kept around 2-3MB and "kswapd" is running. Also I saw that disk
activity was very high.
That mean although "swap" partition is turned off, "kswapd" was trying to do
something. I wonder how that behavior can be explained?
>Ok, so you don't have a /proc/pid/oom_score_adj, so you're using a kernel
>that predates 2.6.36.
Yes, the srv machine that I posted those results, has kernel before 2.6.36
// Naderan *Mahmood;
----- Original Message -----
From: David Rientjes <rientjes@xxxxxxxxxx>
To: Mahmood Naderan <nt_mahmood@xxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxx>; ""linux-kernel@xxxxxxxxxxxxxxx"" <linux-kernel@xxxxxxxxxxxxxxx>; "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx>
Sent: Thursday, August 11, 2011 8:39 AM
Subject: Re: running of out memory => kernel crash
On Wed, 10 Aug 2011, Mahmood Naderan wrote:
> >If you're using cpusets or mempolicies, you must ensure that all tasks
> >attached to either of them are not set to OOM_DISABLE. It seems unlikely
> >that you're using those, so it seems like a system-wide oom condition.
> I didn't do that manually. What is the default behaviour? Does oom
> working or not?
The default behavior is to kill all eligible and unkillable threads until
there are none left to sacrifice (i.e. all kthreads and OOM_DISABLE).
> For a user process:
> root@srv:~# cat /proc/18564/oom_score
> root@srv:~# cat /proc/18564/oom_adj
Ok, so you don't have a /proc/pid/oom_score_adj, so you're using a kernel
that predates 2.6.36.
> And for "init" process:
> root@srv:~# cat /proc/1/oom_score
> root@srv:~# cat /proc/1/oom_adj
> Based on my understandings, in an out of memory condition (oom),
> the init process is more eligible to be killed!!!!!!! Is that right?
init is exempt from oom killing, it's oom_score is meaningless.
> Again I didn't get my answer yet:
> What is the default behavior of linux in an oom condition? If the default is,
> crash (kernel panic), then how can I change that in such a way to kill
> the hungry process?
You either have /proc/sys/vm/panic_on_oom set or it's killing a thread
that is taking down the entire machine. If it's the latter, then please
capture the kernel log and post it as Randy suggested.
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