[PATCH 09/11] drm, cgroup: Introduce lgpu as DRM cgroup resource

[Kenny Ho]

Hi Tejun,

On Fri, Feb 14, 2020 at 2:17 PM Tejun Heo <tj at kernel.org> wrote:
>
> I have to agree with Daniel here. My apologies if I weren't clear
> enough. Here's one interface I can think of:
>
>  * compute weight: The same format as io.weight. Proportional control
>    of gpu compute.
>
>  * memory low: Please see how the system memory.low behaves. For gpus,
>    it'll need per-device entries.
>
> Note that for both, there one number to configure and conceptually
> it's pretty clear to everybody what that number means, which is not to
> say that it's clear to implement but it's much better to deal with
> that on this side of the interface than the other.

Can you elaborate, per your understanding, how the lgpu weight
attribute differ from the io.weight you suggested?  Is it merely a
formatting/naming issue or is it the implementation details that you
find troubling?  From my perspective, the weight attribute implements
as you suggested back in RFCv4 (proportional control on top of a unit
- either physical or time unit.)

Perhaps more explicit questions would help me understand what you
mean. If I remove the 'list' and 'count' attributes leaving just
weight, is that satisfactory?  Are you saying the idea of affinity or
named-resource is banned from cgroup entirely (even though it exists
in the form of cpuset already and users are interested in having such
options [i.e. userspace OpenCL] when needed?)

To be clear, I am not saying no proportional control.  I am saying
give the user the options, which is what has been implemented.

> cc'ing Johannes. Do you have anything on mind regarding how gpu memory
> configuration should look like? e.g. should it go w/ weights rather
> than absoulte units (I don't think so given that it'll most likely
> need limits at some point too but still and there are benefits from
> staying consistent with system memory).
>
> Also, a rather trivial high level question. Is drm a good controller
> name given that other controller names are like cpu, memory, io?

There was a discussion about naming early in the RFC (I believe
RFCv2), the consensuses then was to use drmcg to align with the drm
subsystem.  I have no problem renaming it to gpucg  or something
similar if that is the last thing that's blocking acceptance.  For
now, I would like to get some clarity on the implementation before
having more code churn.

Regards,
Kenny


> Thanks.
>
> --
> tejun