linux-kernel - Re: Memory overcommit

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Message-Id: <20091028152015.3d383cd6.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 28 Oct 2009 15:20:15 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	vedran.furac@...il.com, Hugh Dickins <hugh.dickins@...cali.co.uk>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	minchan.kim@...il.com, Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: Memory overcommit

On Tue, 27 Oct 2009 23:17:41 -0700 (PDT)
David Rientjes <rientjes@...gle.com> wrote:

> On Wed, 28 Oct 2009, KAMEZAWA Hiroyuki wrote:
> 
> > All kernel engineers know "than expected or not" can be never known to the kernel.
> > So, oom_adj workaround is used now. (by some special users.)
> > OOM Killer itself is also a workaround, too.
> > "No kill" is the best thing but we know there are tend to be memory-leaker on bad
> > systems and all systems in this world are not perfect.
> > 
> 
> Right, and historically that has been addressed by considering total_vm 
> and adjusting it with oom_adj so that we can identify memory leaking tasks 
> through user-defined criteria.
> 
> > Yes, some more trustable values other than vmsize/rss/time are appriciated.
> > I wonder recent memory consumption speed can be an another key value.
> > 
> 
> Sounds very logical.
> 
> > Anyway, current bahavior of "killing X" is a bad thing.
> > We need some fixes.
> > 
> 
> You can easily protect X with OOM_DISABLE, as you know.  I don't think we 
> need any X-specific heuristics added to the kernel, it looks like the 
> special cases have already polluted badness() enough.
> 
It's _not_ special to X.

Almost all applications which uses many dynamica libraries can be affected by this,
total_vm. And, as I explained to Vedran, multi-threaded program like Java can easily
increase total_vm without using many anon_rss.
And it's the reason I hate overcommit_memory. size of VM doesn't tell anything.


Thanks,
-Kame

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