linux-kernel - Re: [RFC][PATCH 0/2] memcg: oom notifier and handling oom by user

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Message-Id: <20100309085711.f9158491.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 9 Mar 2010 08:57:11 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 0/2]  memcg: oom notifier and handling oom by user

On Mon, 8 Mar 2010 22:56:09 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2010-03-08 16:24:14]:
> 
> > This 2 patches is for memcg's oom handling.
> > 
> > At first, memcg's oom doesn't mean "no more resource" but means "we hit limit."
> > Then, daemons/user shells out of a memcg can work even if it's under oom.
> > So, if we have notifier and some more features, we can do something moderate
> > rather than killing at oom. 
> > 
> > This patch includes
> > [1/2] oom notifier for memcg (using evetfd framework of cgroups.)
> > [2/2] oom killer disalibing and hooks for waitq and wake-up.
> > 
> > When memcg's oom-killer is disabled, all tasks which request accountable memory
> > will sleep in waitq. It will be waken up by user's action as
> >  - enlarge limit. (memory or memsw)
> >  - kill some tasks
> >  - move some tasks (account migration is enabled.)
> > 
> 
> Hmm... I've not seen the waitq and wake-up patches, but does that mean
> user space will control resumtion of tasks?
> 
Yes. And what's useful in this behavior rathar than oom-kill(SIGKILL) by
the kernel is that users can take coredump (by gcore at el.) and snapshot of
all tasks's resource usage (by ps at el.) even if he has to kill a task.


Thanks,
-Kame

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