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

["Upadhyay, Tejas" <tejas.upadhyay@xxxxxxxxx>]

> -----Original Message-----
> From: De Marchi, Lucas <lucas.demarchi@xxxxxxxxx>
> Sent: Tuesday, February 25, 2025 12:42 AM
> To: Upadhyay, Tejas <tejas.upadhyay@xxxxxxxxx>
> Cc: intel-xe@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx;
> Belgaumkar, Vinay <vinay.belgaumkar@xxxxxxxxx>
> Subject: Re: [PATCH V9] drm/xe/uapi: Use hint for guc to set GT frequency
> 
> On Mon, Feb 24, 2025 at 09:43:09AM -0600, Lucas De Marchi wrote:
> >On Wed, Feb 12, 2025 at 05:08:30PM +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
> >>
> >>v9(Vinay):
> >> - remove extra line, align commit message
> >>v8(Vinay):
> >> - Add separate example for using low latency hint
> >>v7(Jose):
> >> - Update UMD PR
> >> - applicable to all gpus
> >>V6:
> >> - init flags, remove redundant flags check (MAuld)
> >>V5:
> >> - Move uapi doc to documentation and GuC ABI specific change
> >>(Rodrigo)
> >
> >hmn... that doesn't look right.
> >
> >...
> >
> >>diff --git a/Documentation/gpu/drm-uapi.rst
> >>b/Documentation/gpu/drm-uapi.rst index b75cc9a70d1f..7337d1be45ef
> >>100644
> >>--- a/Documentation/gpu/drm-uapi.rst
> >>+++ b/Documentation/gpu/drm-uapi.rst
> >>@@ -583,3 +583,21 @@ dma-buf interoperability
> >>
> >>Please see Documentation/userspace-api/dma-buf-alloc-exchange.rst for
> >>information on how dma-buf is integrated and exposed within DRM.
> >>+
> >>+Low latency hint by user
> >>+========================
> >>+
> >>+Allow users to provide a hint to kernel for cases demanding low
> >>+latency profile. Please note it will have impact on power
> >>+consumption. User can indicate low latency hint with flag while
> >>+creating exec queue as mentioned below,
> >>+
> >>+     struct drm_xe_exec_queue_create exec_queue_create = {
> >>+          .flags = DRM_XE_EXEC_QUEUE_LOW_LATENCY_HINT,
> >>+          .extensions = 0,
> >>+          .vm_id = vm,
> >>+          .num_bb_per_exec = 1,
> >>+          .num_eng_per_bb = 1,
> >>+          .instances = to_user_pointer(&instance),
> >>+     };
> >>+     ioctl(fd, DRM_IOCTL_XE_EXEC_QUEUE_CREATE, &exec_queue_create);
> >
> >how does this driver-specific doc make sense in this file?

Thanks for looking at this.

There was suggestion to add this in documentation during review, @Vivi, Rodrigo Can we remove this? And if we remove this whats point in keeping documentation here for 4 line paragraph? 
@De Marchi, Lucas Do you mean completely remove from here, just keep in xe_drm.h?

Tejas

> 
> to avoid needless noise in the log, I zapped this commit from
> drm-xe-next:
> 
>   + 8f78c0dfbe9d...8b4b3af869e9 drm-xe-next -> drm-xe-next (forced
> update)
> 
> 8b4b3af o [drm-xe-next] {drm-xe/drm-xe-next} {drm-xe/HEAD}
> drm/xe/userptr: remove tmp_evict list
> 6b93cb9 o drm/xe/userptr: fix EFAULT handling
> 4e37e92 o drm/xe/userptr: restore invalidation list on error 8f78c0d │ o
> drm/xe/userptr: remove tmp_evict list f2211aa │ o drm/xe/userptr: fix EFAULT
> handling b9aaabb │ o drm/xe/userptr: restore invalidation list on error
> bee37a8 │ o drm/xe/uapi: Use hint for guc to set GT frequency
> 
> this documentation is also in include/uapi/drm/xe_drm.h, so maybe the best
> thing to do is probably to just drop this part that got included in the wrong
> part. Once this is fixed we can add it back.
> 
> Lucas De Marchi