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From:   "T.J. Mercier" <tjmercier@google.com>
Date:   Wed, 15 Jun 2022 10:31:21 -0700
Message-ID: <CABdmKX0WV8VWgeafVGJ++nJ4xsJD7Wpz=3KX=BW1du=huttfvw@mail.gmail.com>
Subject: Re: [PATCH v7 0/6] Proposal for a GPU cgroup controller
To:     Tejun Heo <tj@kernel.org>
Cc:     Nicolas Dufresne <nicolas@ndufresne.ca>,
        Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
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On Fri, May 20, 2022 at 9:25 AM T.J. Mercier <tjmercier@google.com> wrote:
>
> On Fri, May 20, 2022 at 12:47 AM Tejun Heo <tj@kernel.org> wrote:
> >
> > Hello,
> >
> > On Tue, May 17, 2022 at 04:30:29PM -0700, T.J. Mercier wrote:
> > > Thanks for your suggestion. This almost works. "dmabuf" as a key could
> > > work, but I'd actually like to account for each heap. Since heaps can
> > > be dynamically added, I can't accommodate every potential heap name by
> > > hardcoding registrations in the misc controller.
> >
> > On its own, that's a pretty weak reason to be adding a separate gpu
> > controller especially given that it doesn't really seem to be one with
> > proper abstractions for gpu resources. We don't want to keep adding random
> > keys to misc controller but can definitely add limited flexibility. What
> > kind of keys do you need?
> >
> Well the dmabuf-from-heaps component of this is the initial use case.
> I was envisioning we'd have additional keys as discussed here:
> https://lore.kernel.org/lkml/20220328035951.1817417-1-tjmercier@google.com/T/#m82e5fe9d8674bb60160701e52dae4356fea2ddfa
> So we'd end up with a well-defined core set of keys like "system", and
> then drivers would be free to use their own keys for their own unique
> purposes which could be complementary or orthogonal to the core set.
> Yesterday I was talking with someone who is interested in limiting gpu
> cores and bus IDs in addition to gpu memory. How to define core keys
> is the part where it looks like there's trouble.
>
> For my use case it would be sufficient to have current and maximum
> values for an arbitrary number of keys - one per heap. So the only
> part missing from the misc controller (for my use case) is the ability
> to register a new key at runtime as heaps are added. Instead of
> keeping track of resources with enum misc_res_type, requesting a
> resource handle/ID from the misc controller at runtime is what I think
> would be required instead.
>
Quick update: I'm going to make an attempt to modify the misc
controller to support a limited amount of dynamic resource
registration/tracking in place of the new controller in this series.

Thanks everyone for the feedback.
-T.J.

> > Thanks.
> >
> > --
> > tejun