linux-kernel - Re: [PATCH 4/4] oom: don't kill random process

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Message-ID: <alpine.DEB.2.00.1105101640560.12477@chino.kir.corp.google.com>
Date:	Tue, 10 May 2011 16:41:44 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc:	CAI Qian <caiqian@...hat.com>, avagin@...il.com,
	Andrey Vagin <avagin@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Minchan Kim <minchan.kim@...il.com>,
	Hugh Dickins <hughd@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 4/4] oom: don't kill random process

On Tue, 10 May 2011, KOSAKI Motohiro wrote:

> CAI Qian reported oom-killer killed all system daemons in his
> system at first if he ran fork bomb as root. The problem is,
> current logic give them bonus of 3% of system ram. Example,
> he has 16GB machine, then root processes have ~500MB oom
> immune. It bring us crazy bad result. _all_ processes have
> oom-score=1 and then, oom killer ignore process memroy usage
> and kill random process. This regression is caused by commit
> a63d83f427 (oom: badness heuristic rewrite).
> 
> This patch changes select_bad_process() slightly. If oom points == 1,
> it's a sign that the system have only root privileged processes or
> similar. Thus, select_bad_process() calculate oom badness without
> root bonus and select eligible process.
> 

This second (and very costly) iteration is unnecessary if the range of 
oom scores is increased from 1000 to 10000 or 100000 as suggested in the 
previous patch.
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