linux-kernel - Re: [patch -mm 4/9 v2] oom: remove compulsory panic_on

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Message-Id: <20100216171051.aebbffe5.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 16 Feb 2010 17:10:51 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Lubos Lunak <l.lunak@...e.cz>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch -mm 4/9 v2] oom: remove compulsory panic_on_oom mode

On Tue, 16 Feb 2010 19:08:17 +1100
Nick Piggin <npiggin@...e.de> wrote:

> On Mon, Feb 15, 2010 at 11:53:33PM -0800, David Rientjes wrote:
> > On Tue, 16 Feb 2010, Nick Piggin wrote:
> > 
> > > > Because it is inconsistent at the user's expense, it has never panicked 
> > > > the machine for memory controller ooms, so why is a cpuset or mempolicy 
> > > > constrained oom conditions any different?
> > > 
> > > Well memory controller was added later, wasn't it? So if you think
> > > that's a bug then a fix to panic on memory controller ooms might
> > > be in order.
> > > 
> > 
> > But what about the existing memcg users who set panic_on_oom == 2 and 
> > don't expect the memory controller to be influenced by that?
> 
> But that was a bug in the addition of the memory controller. Either the
> documentation should be fixed, or the implementation should be fixed.
> 
I'll add a documentation to memcg. As

"When you exhaust memory resource under memcg, oom-killer may be invoked.
 But in this case, the system never panics even when panic_on_oom is set."

Maybe I should add "memcg_oom_notify (netlink message or file-decriptor or some".
Because memcg's oom is virtual oom, automatic management software can show
report to users and can do fail-over. I'll consider something useful for
memcg oom-fail-over instead of panic. In the simplest case, cgroup's notiifer
file descriptor can be used.

Thanks,
-Kame

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