Re: [PATCH mm v3 0/9] memcg: accounting for objects allocated by mkdir cgroup

Michal Hocko
2022-06-01T09:32:25Z

On Wed 01-06-22 11:15:43, Michal Koutny wrote:
> On Wed, Jun 01, 2022 at 06:43:27AM +0300, Vasily Averin <vvs-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org> wrote:
> > CT-901 /# cat /sys/fs/cgroup/memory/cgroup.subgroups_limit
> > 512
> > CT-901 /# echo 3333 > /sys/fs/cgroup/memory/cgroup.subgroups_limit
> > -bash: echo: write error: Operation not permitted
> > CT-901 /# echo 333 > /sys/fs/cgroup/memory/cgroup.subgroups_limit
> > -bash: echo: write error: Operation not permitted
> >
> > I doubt this way can be accepted in upstream, however for OpenVz
> > something like this it is mandatory because it much better
> > than nothing.
>
> Is this customization of yours something like cgroup.max.descendants on
> the unified (v2) hierarchy? (Just curious.)
>
> (It can be made inaccessible from within the subtree either with cgroup
> ns or good old FS permissions.)

So we already do have a limit to prevent somebody from running away with
the number of cgroups. Nice! I was not aware of that and I guess this
looks like the right thing to do. So do we need more control and
accounting that this?
--
Michal Hocko
SUSE Labs