[Mesa-dev] [PATCH 2/2] i965: Context aware user space EU control through application

[Chris Wilson]

Quoting aravindan.muthukumar at intel.com (2018-07-20 09:32:57)
> From: "Muthukumar, Aravindan" <aravindan.muthukumar at intel.com>
> 
>  The Patch here is to give control to user/ application to really
>  decide what's the max GPU load it would put. If that can be
>  known in advance, rpcs can be programmed accordingly.
>  This solution has changes across i915,
>  drm and mesa (not limited only to kernel).
> 
>  Here, we pass gpu_load_type = {high, medium, low} from application
>  while context is created. Default here is 'High' and applications
>  roughly know if they are going to eat up entire GPU. The typical
>  usecase of 'Low' is idle screen or minor mouse movements. Users can
>  read meaning of high/medium/low for their platform  & then program
>  contexts accordingly. Here gpu_load_type directly translates to
>  number of shader cores/EUs a particular GPU has.
> 
>  Signed-off-by: Aravindan Muthukumar <aravindan.muthukumar at intel.com>
>  Signed-off-by: Kedar J Karanje <kedar.j.karanje at intel.com>
>  Signed-off-by: Praveen Diwakar <praveen.diwakar at intel.com>
>  Signed-off-by: Yogesh Marathe <yogesh.marathe at intel.com>

> +/* Dynamic Eu control */
> +struct drm_i915_load_type {
> +       __u32 ctx_id;
> +       __u32 load_type;
> +};
> +
> +/* DYNAMIC EU CONTROL */
> +int
> +brw_hw_context_load_type(struct brw_bufmgr *bufmgr,
> +                        uint32_t ctx_id,
> +                        int load_type)
> +{
> +       struct drm_i915_load_type type = {
> +               .ctx_id = ctx_id,
> +               .load_type = load_type,
> +       };
> +       int err;
> +
> +       err = 0;
> +       if(drmIoctl(bufmgr->fd, DRM_IOCTL_I915_LOAD_TYPE, &type))
> +               err = -errno;

This went through 4 people and none noticed that there already exists a
means to set per-context parameters. And it's even used right next to
this function.

The word hint needs to be firmly embedded around here.
-Chris