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

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Message-ID: <alpine.DEB.2.00.1002161550550.11952@chino.kir.corp.google.com>
Date:	Tue, 16 Feb 2010 15:54:50 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Nick Piggin <npiggin@...e.de>,
	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 Wed, 17 Feb 2010, KAMEZAWA Hiroyuki wrote:

> Please don't. I had a chance to talk with customer support team and talked
> about panic_on_oom briefly. I understood that panic_on_oom_alyways+kdump
> is the strongest tool for investigating customer's OOM situtation and do
> the best advice to them. panic_on_oom_always+kdump is the 100% information
> as snapshot when oom-killer happens. Then, it's easy to investigate and
> explain what is wront. They sometimes discover memory leak (by some prorietary
> driver) or miss-configuration of the system (as using unnecessary bounce buffer.)
> 

Ok, I'm not looking to cause your customers unnecessary grief by removing 
an option that they use, even though the same effect is possible by 
setting all tasks to OOM_DISABLE.  I'll remove this patch in the next 
revision.

> Then, please leave panic_on_oom=always.
> Even with mempolicy or cpuset 's OOM, we need panic_on_oom=always option.
> And yes, I'll add something similar to memcg. freeze_at_oom or something.
> 

Memcg isn't a special case here, it should also panic the machine if 
panic_on_oom == 2, so if we aren't going to remove this option then I 
agree with Nick that we need to panic from mem_cgroup_out_of_memory() as 
well.  Some users use cpusets, for example, for the same effect of memory 
isolation as you use memcg, so panicking in one scenario and not the other 
is inconsistent.
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