Re: [PATCH V9] drm/xe/uapi: Use hint for guc to set GT frequency

["Teres Alexis, Alan Previn" <alan.previn.teres.alexis@intel.com>]

On Wed, 2025-02-12 at 17:48 +0530, Tejas Upadhyay wrote:
> Allow user to provide a low latency hint. When set, KMD sends a hint
> to GuC which results in special handling for that process. SLPC will
> ramp the GT frequency aggressively every time it switches to this
> process.
> 
> We need to enable the use of SLPC Compute strategy during init, but
> it will apply only to processes that set this bit during process
> creation.
> 
> Improvement with this approach as below:
> 
> Before,
> 
> :~$ NEOReadDebugKeys=1 EnableDirectSubmission=0 clpeak --kernel-latency
> Platform: Intel(R) OpenCL Graphics
>   Device: Intel(R) Graphics [0xe20b]
>     Driver version  : 24.52.0 (Linux x64)
>     Compute units   : 160
>     Clock frequency : 2850 MHz
>     Kernel launch latency : 283.16 us
> 
> After,
> 
> :~$ NEOReadDebugKeys=1 EnableDirectSubmission=0 clpeak --kernel-latency
> Platform: Intel(R) OpenCL Graphics
>   Device: Intel(R) Graphics [0xe20b]
>     Driver version  : 24.52.0 (Linux x64)
>     Compute units   : 160
>     Clock frequency : 2850 MHz
> 
>     Kernel launch latency : 63.38 us
> 
> UMD Compute PR : https://github.com/intel/compute-runtime/pull/794
> UMD Mesa PR :  https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33214
> 
might be a silly question: looking at the UMD patches, am i reading it wrong but it looks like the UMDs are just going
to always enable low latency hint (as long as hw/kernel supports it)? I mean if that is the system level direction, then
why require a method for user-space to request, just always enable in kernel? or is UMD supposed to expose an extention
or something for the system integrator supposed to selectively modify app code?

...alan