linux-kernel - Re: [PATCH] trace: Set oom_score_adj to maximum for ring buffer allocating process

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Message-ID: <4DE337FB.3000804@jp.fujitsu.com>
Date:	Mon, 30 May 2011 15:23:55 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	rostedt@...dmis.org
CC:	vnagarnaik@...gle.com, rientjes@...gle.com, mingo@...hat.com,
	fweisbec@...il.com, mrubin@...gle.com, dhsharp@...gle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] trace: Set oom_score_adj to maximum for ring buffer allocating
 process

(2011/05/28 10:50), Steven Rostedt wrote:
> On Fri, 2011-05-27 at 17:44 -0700, Vaibhav Nagarnaik wrote:
> 
>> That said, I am open to changing it if Steven and you think using
>> oom_killer_disabled is a better solution.
> 
> My biggest concern is that we are setting policy in the kernel. If you
> are concerned about this, why not just have the process that is going to
> increase the size of the ring buffer adjust its own oom policy
> with /proc/<pid>/oom_score_adj ? Only a privilege process can increase
> the size of the ring buffer so it's not like we are worried about any
> normal user task upping the ring buffer to kill other processes.

I like Steven's approach.

Because even if we apply Vaibhav's patch, we still have a oom issue.
because when oom-killer killed echo commands, it doesn't shrink ring
buffer. it only just die. So, the kernel is still under extreme memory
shortage. Any admins operation may invoke next oom-killer.

And -personally- I think any tracing user should know system ram size
and proper ring buffer size. ;)

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