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

[Lucas De Marchi]

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?

Lucas De Marchi