linux-kernel - Re: [PATCH 1/2][BUGFIX] oom: remove totalpage normalization from oom

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Date:	Wed, 25 Aug 2010 17:52:06 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH 1/2][BUGFIX] oom: remove totalpage normalization from
 oom_badness()

On Thu, 26 Aug 2010, KAMEZAWA Hiroyuki wrote:

> I'm now trying to write a userspace tool to calculate this, for me.
> Then, could you update documentation ? 
> ==
> 3.2 /proc/<pid>/oom_score - Display current oom-killer score
> -------------------------------------------------------------
> 
> This file can be used to check the current score used by the oom-killer is for
> any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
> process should be killed in an out-of-memory situation.
> ==
> 

You'll want to look at section 3.1 of Documentation/filesystems/proc.txt, 
which describes /proc/pid/oom_score_adj, not 3.2.

> add a some documentation like:
> ==
> (For system monitoring tool developpers, not for usual users.)
> oom_score calculation is implemnentation dependent and can be modified without
> any caution. But current logic is
> 
> oom_score = ((proc's rss + proc's swap) / (available ram + swap)) + oom_score_adj
> 

I'd hesitate to state the formula outside of the implementation and 
instead focus on the semantics of oom_score_adj (as a proportion of 
available memory compared to other tasks), which I tried doing in section 
3.1.  Then, the userspace tool only need be concerned about the units of 
oom_score_adj rather than whether rss, swap, or later extentions such as 
shm are added.

Thanks for working on this, Kame!
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