linux-kernel - Re: can't oom-kill zap the victim's memory?

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Date:	Mon, 21 Sep 2015 16:42:44 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Oleg Nesterov <oleg@...hat.com>
cc:	Michal Hocko <mhocko@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kyle Walker <kwalker@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Vladimir Davydov <vdavydov@...allels.com>,
	linux-mm <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Stanislav Kozina <skozina@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: can't oom-kill zap the victim's memory?

On Mon, 21 Sep 2015, Oleg Nesterov wrote:

> Yes we should try to do this in the OOM killer context, and in this case
> (of course) we need trylock. Let me quote my previous email:
> 
> 	And we want to avoid using workqueues when the caller can do this
> 	directly. And in this case we certainly need trylock. But this needs
> 	some refactoring: we do not want to do this under oom_lock, otoh it
> 	makes sense to do this from mark_oom_victim() if current && killed,
> 	and a lot more details.
> 
> and probably this is another reason why do we need MMF_MEMDIE. But again,
> I think the initial change should be simple.
> 

I agree with the direction and I don't think it would be too complex to 
have a dedicated kthread that is kicked when we queue an mm to do 
MADV_DONTNEED behavior, and have that happen only if a trylock in 
oom_kill_process() fails to do it itself for anonymous mappings.  We may 
have different opinions of simplicity.
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