Re: [PATCH 2/3] memcg: Limit the number of events registered onoom_control

From: Tejun Heo
Date: Wed Aug 07 2013 - 09:47:52 EST


On Wed, Aug 07, 2013 at 03:37:46PM +0200, Michal Hocko wrote:
> > It isn't different from listening from epoll, for example.
> epoll limits the number of watchers, no?

Not that I know of. It'll be limited by max open fds but I don't
think there are other limits. Why would there be?

> > If there needs to be kernel memory limit, shouldn't that be handled by
> > kmemcg?
> kmemcg would surely help but turning it on just because of potential
> abuse of the event registration API sounds like an overkill.
> I think having a cap for user trigable kernel resources is a good thing
> in general.

I don't know. It's just very arbitrary because listening to events
itself isn't (and shouldn't) be something which consumes resource
which isn't attributed to the listener and this artificially creates a
global resource. The problem with memory usage event is breaching
that rule with shared kmalloc() so putting well-defined limit on it is
fine but the latter two create additional artificial restrictions
which are both unnecessary and unconventional. No?


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