Re: [PATCH] epoll: account epitem and eppoll_entry to kmemcg

[Michal Hocko <mhocko@kernel.org>]

On Thu 05-10-17 10:21:18, Michal Hocko wrote:
> On Wed 04-10-17 12:33:14, Shakeel Butt wrote:
> > >
> > > I am not objecting to the patch I would just like to understand the
> > > runaway case. ep_insert seems to limit the maximum number of watches to
> > > max_user_watches which should be ~4% of lowmem if I am following the
> > > code properly. pwq_cache should be bound by the number of watches as
> > > well, or am I misunderstanding the code?
> > >
> > 
> > You are absolutely right that there is a per-user limit (~4% of total
> > memory if no highmem) on these caches. I think it is too generous
> > particularly in the scenario where jobs of multiple users are running
> > on the system and the administrator is reducing cost by overcomitting
> > the memory. This is unaccounted kernel memory and will not be
> > considered by the oom-killer. I think by accounting it to kmemcg, for
> > systems with kmem accounting enabled, we can provide better isolation
> > between jobs of different users.
> 
> Thanks for the clarification. For some reason I didn't figure that the
> limit is per user, even though the name suggests so.

Completely forgot to add
Acked-by: Michal Hocko <mhocko@suse.com>
-- 
Michal Hocko
SUSE Labs

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