[RFC PATCH v2 4/5] drm, cgroup: Add total GEM buffer allocation limit

[Kenny Ho]

On Fri, May 10, 2019 at 11:08 AM Koenig, Christian
<Christian.Koenig at amd.com> wrote:
> Am 10.05.19 um 16:57 schrieb Kenny Ho:
> > On Fri, May 10, 2019 at 8:28 AM Christian König
> > <ckoenig.leichtzumerken at gmail.com> wrote:
> >> Am 09.05.19 um 23:04 schrieb Kenny Ho:
> So the drm cgroup container is separate to other cgroup containers?
In cgroup-v1, which is most widely deployed currently, all controllers
have their own hierarchy (see /sys/fs/cgroup/).  In cgroup-v2, the
hierarchy is unified by individual controllers can be disabled (I
believe, I am not super familiar with v2.)

> In other words as long as userspace doesn't change, this wouldn't have
> any effect?
As far as things like docker and podman is concern, yes.  I am not
sure about the behaviour of others like lxc, lxd, etc. because I
haven't used those myself.

> Well that is unexpected cause then a processes would be in different
> groups for different controllers, but if that's really the case that
> would certainly work.
I believe this is a possibility for v1 and is why folks came up with
the unified hierarchy in v2 to solve some of the issues.
https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#issues-with-v1-and-rationales-for-v2

Regards,
Kenny

> > On the other hand, if there are expectations for resource management
> > between containers, I would like to know who is the expected manager
> > and how does it fit into the concept of container (which enforce some
> > level of isolation.)  One possible manager may be the display server.
> > But as long as the display server is in a parent cgroup of the apps'
> > cgroup, the apps can still import handles from the display server
> > under the current implementation.  My understanding is that this is
> > most likely the case, with the display server simply sitting at the
> > default/root cgroup.  But I certainly want to hear more about other
> > use cases (for example, is running multiple display servers on a
> > single host a realistic possibility?  Are there people running
> > multiple display servers inside peer containers?  If so, how do they
> > coordinate resources?)
>
> We definitely have situations with multiple display servers running
> (just think of VR).
>
> I just can't say if they currently use cgroups in any way.
>
> Thanks,
> Christian.
>
> >
> > I should probably summarize some of these into the commit message.
> >
> > Regards,
> > Kenny
> >
> >
> >
> >> Christian.
> >>
>