linux-kernel - Re: Memory overcommit

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Message-Id: <20091027153626.c5a4b5be.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 27 Oct 2009 15:36:26 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	vedran.furac@...il.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: Memory overcommit

On Tue, 27 Oct 2009 15:34:29 +0900
Minchan Kim <minchan.kim@...il.com> wrote:

> On Tue, 27 Oct 2009 15:10:52 +0900
> KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> 
> > 2009/10/27 KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>:
> > > On Mon, 26 Oct 2009 17:16:14 +0100
> > > Vedran Furač <vedran.furac@...il.com> wrote:
> > >> >  - Could you show me /var/log/dmesg and /var/log/messages at OOM ?
> > >>
> > >> It was catastrophe. :) X crashed (or killed) with all the programs, but
> > >> my little program was alive for 20 minutes (see timestamps). And for
> > >> that time computer was completely unusable. Couldn't even get the
> > >> console via ssh. Rally embarrassing for a modern OS to get destroyed by
> > >> a 5 lines of C run as an ordinary user. Luckily screen was still alive,
> > >> oomk usually kills it also. See for yourself:
> > >>
> > >> dmesg: http://pastebin.com/f3f83738a
> > >> messages: http://pastebin.com/f2091110a
> > >>
> > >> (CCing to lklm again... I just want people to see the logs.)
> > >>
> > > Thank you for reporting and your patience. It seems something strange
> > > that your KDE programs are killed. I agree.
> > >
> > > I attached a scirpt for checking oom_score of all exisiting process.
> > > (oom_score is a value used for selecting "bad" processs.")
> > > please run if you have time.
> > >
> > > This is a result of my own desktop(on virtual machine.)
> > > In this environ (Total memory is 1.6GBytes), mmap(1G) program is running.
> > >
> > > %check_badness.pl | sort -n | tail
> > > --
> > > 89924   3938    mixer_applet2
> > > 90210   3942    tomboy
> > > 94753   3936    clock-applet
> > > 101994  3919    pulseaudio
> > > 113525  4028    gnome-terminal
> > > 127340  1       init
> > > 128177  3871    nautilus
> > > 151003  11515   bash
> > > 256944  11653   mmap
> > > 425561  3829    gnome-session
> > > --
> > > Sigh, gnome-session has twice value of mmap(1G).
> > > Of course, gnome-session only uses 6M bytes of anon.
> > > I wonder this is because gnome-session has many children..but need to
> > > dig more. Does anyone has idea ?
> > > (CCed kosaki)
> > 
> > Following output address the issue.
> > The fact is, modern desktop application linked pretty many library. it
> > makes bloat VSS size and increase
> > OOM score.
> > 
> > Ideally, We shouldn't account evictable file-backed mappings for oom_score.
> > 
> Hmm. 
> I wonder why we consider VM size for OOM kiling. 
> How about RSS size?
> 

Maybe the current code assumes "Tons of swap have been generated, already" if
oom-kill is invoked. Then, just using mm->anon_rss will not be correct.

Hm, should we count # of swap entries reference from mm ?....

Regards,
-Kame


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