linux-kernel - Re: PROBLEM: oom killer and swap weirdness on 2.6.3* kernels

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Date:	Tue, 27 Jul 2010 00:05:55 +1000
From:	dave b <db.pub.mail@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: PROBLEM: oom killer and swap weirdness on 2.6.3* kernels

On 2 June 2010 06:52, David Rientjes <rientjes@...gle.com> wrote:
> On Thu, 27 May 2010, dave b wrote:
>
>> That was just a simple test case with dd. That test case might be
>> invalid - but it is trying to trigger out of memory - doing this any
>> other way still causes the problem. I note that playing with some bios
>> settings I was actually able to trigger what appeared to be graphics
>> corruption issues when I launched kde applications ... nothing shows
>> up in dmesg so this might just be a conflict between xorg and the
>> kernel with those bios settings...
>>
>> Anyway, This is no longer a 'problem' for me since I disabled
>> overcommit and altered the values for dirty_ratio and
>> dirty_background_ratio - and I cannot trigger it.
>>
>
> Disabling overcommit should always do it, but I'd be interested to know if
> restoring dirty_ratio to 40 would help your usecase.
>
Actually it turns out on 2.6.34.1 I can trigger this issue. What it
really is, is that linux doesn't invoke the oom killer when it should
and kill something off. This is *really* annoying.

I used the follow script - (on 2.6.34.1)
cat ./scripts/disable_over_commit
#!/bin/bash
echo 2 > /proc/sys/vm/overcommit_memory
echo 40 > /proc/sys/vm/dirty_ratio
echo 5 > /proc/sys/vm/dirty_background_ratio

And I was still able to reproduce this bug.
Here is some c  code to trigger the condition I am talking about.


#include <stdlib.h>
#include <stdio.h>

int main(void)
{
	while(1)
	{
		malloc(1000);
	}

	return 0;
}
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