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

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Date:	Mon, 22 Feb 2010 12:55:57 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	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 Mon, 22 Feb 2010, KAMEZAWA Hiroyuki wrote:

> Essential fix is better. The best fix is don't call oom-killer in
> pagefault_out_of_memory. So, returning other than VM_FAULT_OOM is
> the best, I think. But hmm...we don't have VM_FAULT_AGAIN etc..
> So, please avoid quick fix. 
> 

The last patch in my oom killer series defaults pagefault_out_of_memory() 
to always kill current first, if it's killable.  If it is unsuccessful, we 
fallback to scanning the entire tasklist.

For tasks that are constrained by a memcg, we could probably use 
mem_cgroup_from_task(current) and if it's non-NULL and non-root, call 
mem_cgroup_out_of_memory() with a gfp_mask of 0.  That would at least 
penalize the same memcg instead of invoking a global oom and would try the 
additional logic that you plan on adding to avoid killing any task at all 
in such conditions.
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