Re: [RFC][PATCH 0/2] memcg: oom notifier and handling oom by user

From: KAMEZAWA Hiroyuki
Date: Mon Mar 08 2010 - 19:00:54 EST


On Mon, 8 Mar 2010 22:56:09 +0530
Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-03-08 16:24:14]:
>
> > This 2 patches is for memcg's oom handling.
> >
> > At first, memcg's oom doesn't mean "no more resource" but means "we hit limit."
> > Then, daemons/user shells out of a memcg can work even if it's under oom.
> > So, if we have notifier and some more features, we can do something moderate
> > rather than killing at oom.
> >
> > This patch includes
> > [1/2] oom notifier for memcg (using evetfd framework of cgroups.)
> > [2/2] oom killer disalibing and hooks for waitq and wake-up.
> >
> > When memcg's oom-killer is disabled, all tasks which request accountable memory
> > will sleep in waitq. It will be waken up by user's action as
> > - enlarge limit. (memory or memsw)
> > - kill some tasks
> > - move some tasks (account migration is enabled.)
> >
>
> Hmm... I've not seen the waitq and wake-up patches, but does that mean
> user space will control resumtion of tasks?
>
Yes. And what's useful in this behavior rathar than oom-kill(SIGKILL) by
the kernel is that users can take coredump (by gcore at el.) and snapshot of
all tasks's resource usage (by ps at el.) even if he has to kill a task.


Thanks,
-Kame

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