linux-kernel - Re: [PATCH v2]oom-kill: CAP_SYS

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Date:	Tue, 9 Nov 2010 13:06:42 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"Figo.zhang" <zhangtianfei@...dcoretech.com>,
	figo zhang <figo1802@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH v2]oom-kill: CAP_SYS_RESOURCE should get bonus

On Tue, 9 Nov 2010, Alan Cox wrote:

> The reverse can be argued equally - that they can unprotect themselves if
> necessary. In fact it seems to be a "point of view" sort of question
> which way you deal with CAP_SYS_RESOURCE, and that to me argues that
> changing from old expected behaviour to a new behaviour is a regression.
> 

I didn't check earlier, but CAP_SYS_RESOURCE hasn't had a place in the oom 
killer's heuristic in over five years, so what regression are we referring 
to in this thread?  These tasks already have full control over 
oom_score_adj to modify its oom killing priority in either direction.

And, as I said, giving these threads a bonus to be less preferred doesn't 
seem appropriate since (1) it's not a defined or expected behavior of 
CAP_SYS_RESOURCE like it is for sysadmin tasks, and (2) these threads are 
not bound by resource limits and thus have a higher liklihood of consuming 
larger amounts of memory.

That's why I nack'd the patch in the first place and still do, there's no 
regression here and it's not in the best interest of freeing a large 
amount of memory which is the sole purpose of the oom killer.

Futhermore, the heuristic was entirely rewritten, but I wouldn't consider 
all the old factors such as cputime and nice level being removed as 
"regressions" since the aim was to make it more predictable and more 
likely to kill a large consumer of memory such that we don't have to kill 
more tasks in the near future.
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