linux-kernel - Re: Memory overcommit

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Date:	Tue, 27 Oct 2009 17:25:47 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	vedran.furac@...il.com
cc:	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	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 Wed, 28 Oct 2009, Vedran Fura wrote:

> But it is wrong at counting allocated memory!
> Come on, it kills /usr/lib/icedove/run-mozilla.sh. Parent, a shell
> script, instead of its child(s) which allocated memory. Look, "test"
> allocates some (0.1GB) memory, and you have:
> 
> % cat test.sh
> 
> #!/bin/sh
> ./test&
> ./test&
> ./test&
> ./test
> 
> % perl check_badness.pl|sort -n|g test
> 
> 26511   7884    test
> 26511   7885    test
> 26511   7886    test
> 26511   7887    test
> 53994   7883    test.sh
> 
> // great, so test.sh "is" the bad ass, ok, emulate OOMK:
> 
> % kill -9 7883
> 
> // did we kill "a rogue task"
> 
> % perl check_badness.pl|sort -n|g test
> 
> 26511   7884    test
> 26511   7885    test
> 26511   7886    test
> 26511   7887    test
> 
> // nooo, they are still alive and eating our memory!
> 

This is wrong; it doesn't "emulate oom" since oom_kill_process() always 
kills a child of the selected process instead if they do not share the 
same memory.  The chosen task in that case is untouched.
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