Re: [patch] mm, memcg: add oom killer delay

From: Kamezawa Hiroyuki
Date: Thu Jun 13 2013 - 20:57:12 EST

(2013/06/14 7:25), David Rientjes wrote:
On Thu, 13 Jun 2013, Michal Hocko wrote:

That's not at all the objective, the changelog quite explicitly states
this is a deadlock as the result of userspace having disabled the oom
killer so that its userspace oom handler can resolve the condition and it
being unresponsive or unable to perform its job.

Ohh, so another round. Sigh. You insist on having user space handlers
running in the context of the limited group. OK, I can understand your
use case, although I think it is pushing the limits of the interface and
it is dangerous.

Ok, this is where our misunderstanding is, and I can see why you have
reacted the way you have. It's my fault for not describing where we're
going with this.

Reading your discussion, I think I understand your requirements.
The problem is that I can't think you took into all options into
accounts and found the best way is this new oom_delay. IOW, I can't
convice oom-delay is the best way to handle your issue.

Your requeirement is
- Allowing userland oom-handler within local memcg.

Considering straightforward, the answer should be
- Allowing oom-handler daemon out of memcg's control by its limit.
(For example, a flag/capability for a task can archive this.)
Or attaching some *fixed* resource to the task rather than cgroup.

Allow to set task->secret_saving=20M.

Going back to your patch, what's confusing is your approach.
Why the problem caused by the amount of memory should be solved by
some dealy, i.e. the amount of time ?

This exchanging sounds confusing to me.

I'm not against what you finally want to do, but I don't like the fix.


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