linux-kernel - Re: Improving OOM killer

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Message-Id: <201002032222.15238.l.lunak@suse.cz>
Date:	Wed, 3 Feb 2010 22:22:15 +0100
From:	Lubos Lunak <l.lunak@...e.cz>
To:	balbir@...ux.vnet.ibm.com
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>, Jiri Kosina <jkosina@...e.cz>
Subject: Re: Improving OOM killer

On Wednesday 03 of February 2010, Balbir Singh wrote:
> * Lubos Lunak <l.lunak@...e.cz> [2010-02-03 13:10:27]:
> > On Wednesday 03 of February 2010, Balbir Singh wrote:
> > > 2. RSS alone is not sufficient, RSS does not account for shared pages,
> > > so we ideally need something like PSS.
> >
> >  Just to make sure I understand what you mean with "RSS does not account
> > for shared pages" - you say that if a page is shared by 4 processes, then
> > when calculating badness for them, only 1/4 of the page should be counted
> > for each? Yes, I suppose so, that makes sense.
>
> Yes, that is what I am speaking of
>
> > That's more like fine-tunning at
> > this point though, as long as there's no agreement that moving away from
> > VmSize is an improvement.
>
> There is no easy way to calculate the Pss today without walking the
> page tables, but some simplification there will make it a better and a
> more accurate metric.

 OOM should be a rare situation, so doing a little amount of counting 
shouldn't be a big deal. Especially if the machine is otherwise busy waiting 
for the HDD paging stuff out and in again and has plenty of CPU time to 
waste.

-- 
 Lubos Lunak
 openSUSE Boosters team, KDE developer
 l.lunak@...e.cz , l.lunak@....org
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