Re: [RFC][PATCH] oom_kill: avoid depends on total_vm and use realRSS/swap value for oom_score (Re: Memory overcommit

[Minchan Kim]

On Tue, 27 Oct 2009 16:45:26 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:

> On Tue, 27 Oct 2009 15:55:26 +0900
> Minchan Kim <minchan.kim@xxxxxxxxx> wrote:
> 
> > >> 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 ?....
> > 
> > In Vedran case, he didn't use swap. So, Only considering vm is the problem.
> > I think it would be better to consider both RSS + # of swap entries as
> > Kosaki mentioned.
> > 
> Then, maybe this kind of patch is necessary.
> This is on 2.6.31...then I may have to rebase this to mmotom.
> Added more CCs.
> 
> Vedran, I'm glad if you can test this patch.
> 
> 
> ==
> Now, oom-killer's score uses mm->total_vm as its base value.
> But, in these days, applications like GUI program tend to use
> much shared libraries and total_vm grows too high even when
> pages are not fully mapped.
> 
> For example, running a program "mmap" which allocates 1 GBbytes of
> anonymous memory, oom_score top 10 on system will be..
> 
>  score  PID     name
>  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 <-----------------use 1G of anon
>  425561	3829	gnome-session
> 
> No one believes gnome-session is more guilty than "mmap".
> 
> Instead of total_vm, we should use anon/file/swap usage of a process, I think.
> This patch adds mm->swap_usage and calculate oom_score based on
>   anon_rss + file_rss + swap_usage.
> Considering usual applications, this will be much better information than
> total_vm. After this patch, the score on my desktop is
> 
> score   PID     name
> 4033	3176	gnome-panel
> 4077	3113	xinit
> 4526	3190	python
> 4820	3161	gnome-settings-
> 4989	3289	gnome-terminal
> 7105	3271	tomboy
> 8427	3177	nautilus
> 17549	3140	gnome-session
> 128501	3299	bash
> 256106	3383	mmap
> 
> This order is not bad, I think.
> 
> Note: This adss new counter...then new cost is added.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

Thanks for making the patch.
Let's hear other's opinion. :)

-- 
Kind regards,
Minchan Kim
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