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

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Message-ID: <20150921135704.GA17804@redhat.com>
Date:	Mon, 21 Sep 2015 15:57:04 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Raymond Jennings <shentino@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kyle Walker <kwalker@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	Michal Hocko <mhocko@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	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 09/20, Raymond Jennings wrote:
>
> On 09/20/15 11:05, Linus Torvalds wrote:
>>
>> which can be called from just about any context (but atomic
>> allocations will never get here, so it can schedule etc).
>
> I think in this case the oom killer should just slap a SIGKILL on the
> task and then back out, and whatever needed the memory should just wait
> patiently for the sacrificial lamb to commit seppuku.

Not sure I understand you correctly, but this is what we currently do.
The only problem is that this doesn't work sometimes.

> Also, I observed that a task in the middle of dumping core doesn't
> respond to signals while it's dumping,

How did you observe this? The coredumping is killable.

Although yes, we have problems here in oom condition. In particular
with CLONE_VM tasks.

Oleg.

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