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Sender: Tejun Heo <htejun@gmail.com>
Date:   Fri, 13 May 2022 06:13:25 -1000
From:   Tejun Heo <tj@kernel.org>
To:     "T.J. Mercier" <tjmercier@google.com>
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Subject: Re: [PATCH v7 0/6] Proposal for a GPU cgroup controller
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Hello,

On Thu, May 12, 2022 at 08:43:52PM -0700, T.J. Mercier wrote:
> > I'm actually happy I've asked this question, wasn't silly after all. I think the
> > problem here is a naming issue. What you really are monitor is "video memory",
> > which consist of a memory segment allocated to store data used to render images
> > (its not always images of course, GPU an VPU have specialized buffers for their
> > purpose).
> >
> > Whether this should be split between what is used specifically by the GPU
> > drivers, the display drivers, the VPU (CODEC and pre/post-processor) or camera
> > drivers is something that should be discussed. But in the current approach, you
> > really meant Video memory as a superset of the above. Personally, I think
> > generically (to de-Andronized your work), en-globing all video memory is
> > sufficient. What I fail to understand is how you will manage to distinguished
> > DMABuf Heap allocation (which are used outside of Android btw), from Video
> > allocation or other type of usage. I'm sure non-video usage will exist in the
> > future (think of machine learning, compute, other high bandwidth streaming
> > thingy ...)
> >
> Ok thank you for pointing out the naming issue. The naming is a
> consequence of the initial use case, but I guess it's too specific.
> What I want out of this change is that android can track dmabufs that
> come out of heaps, and drm can track gpu memory. But other drivers
> could track different resources under different names. Imagine this
> were called a buffer cgroup controller instead of a GPU cgroup
> controller. Then the use component ("video memory") isn't tied up with
> the name of the controller, but it's up to the name of the bucket the
> resource is tracked under. I think this meets the needs of the two use
> cases I'm aware of now, while leaving the door open to other future
> needs. Really the controller is just enabling abstract named buckets
> for tracking and eventually limiting a type of resource.

So, there hasn't been whole lot of discussion w/ other GPU folks and what
comes up still seems to indicate that we're still long way away from having
a meaningful gpu controller. For your use case, would it make sense to just
add dmabuf as a key to the misc controller? I'm not sure it makes sense to
push "gpu controller" forward if there's no conceptual consensus around what
resources are.

Thanks.

-- 
tejun