linux-kernel - Re: [PATCH] fs: limit maximum concurrent coredumps

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Message-Id: <20100622174906.ddf7d298.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 22 Jun 2010 17:49:06 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Roland McGrath <roland@...hat.com>,
	Edward Allcutt <edward@...cutt.me.uk>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Randy Dunlap <rdunlap@...otime.net>,
	Jiri Kosina <jkosina@...e.cz>,
	Dave Young <hidave.darkstar@...il.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Neil Horman <nhorman@...driver.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>
Subject: Re: [PATCH] fs: limit maximum concurrent coredumps

On Mon, 21 Jun 2010 18:41:16 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Mon, 21 Jun 2010 18:23:03 -0700 (PDT) Roland McGrath <roland@...hat.com> wrote:

> > That won't make your crashers each complete quickly, but it will prevent
> > the thrashing.  Instead of some crashers suddenly not producing dumps at
> > all, they'll just all queue up waiting to finish crashing but not using any
> > CPU or IO resources.  That way you don't lose any core dumps unless you
> > want to start SIGKILL'ing things (which oom_kill might do if need be),
> > you just don't die in flames trying to do nothing but dump cores.
> 
> A global knob is a bit old-school.  Perhaps it should be a per-memcg
> knob or something.
> 

Hmm, in my desktop, it seems coredump in a group is charged against
root cgroup. (not against the group it belongs to.)
This seems strange.....I've chased why...for 2 hours. I noticed 

==
[root@...extal kamezawa]# cat /proc/sys/kernel/core_pattern
|/usr/libexec/abrt-hook-ccpp /var/cache/abrt %p %s %u %c
==
This is fedora-12.

Then, for recent distros, doing "coredump" with some limited resource may
be a job of abrt program. It can make use of I/O cgroup + direct I/O.

If a kernel help is necesary, this helper function should work in
the caller's cgroup, maybe.

Regards,
-Kame

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