Re: [RFC v1] drm/xe/migrate: Configure migration queue as low latency

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Dec 19, 2025 at 11:49:03AM +0100, Francois Dugast wrote:
> Commit 5488bec96bcc ("drm/xe/uapi: Use hint for guc to set GT frequency")
> introduced low latency hint for use by user space when creating an exec
> queue. This instructs SLPC to ramp the GT frequency aggressively.
> 
> SVM relies on an internal exec queue to migrate memory upon page faults.
> This change creates this exec queue with the low latency hint to speed up
> migration.
> 
> This should not impact systems where GT frequency is set over sysfs, or
> with long running workloads which give enough time for the frequency to
> ramp up. An example of memory access pattern that shows an improvement of
> SVM performance is running hundreds of times IGT eu-fault-2m-once-device
> in xe_exec_system_allocator. The copy duration provided by GT stats in
> svm_2M_device_copy_us shows per GPU page fault:
>     ~ 165 μs without low latency hint
>     ~ 130 μs with low latency hint

\o/

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

> 
> Suggested-by: Matthew Brost <matthew.brost@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: Francois Dugast <francois.dugast@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_migrate.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> index f3b66b55acfb..878b13f27be4 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -471,7 +471,8 @@ int xe_migrate_init(struct xe_migrate *m)
>  					    EXEC_QUEUE_FLAG_KERNEL |
>  					    EXEC_QUEUE_FLAG_PERMANENT |
>  					    EXEC_QUEUE_FLAG_HIGH_PRIORITY |
> -					    EXEC_QUEUE_FLAG_MIGRATE, 0);
> +					    EXEC_QUEUE_FLAG_MIGRATE |
> +					    EXEC_QUEUE_FLAG_LOW_LATENCY, 0);
>  	} else {
>  		m->q = xe_exec_queue_create_class(xe, primary_gt, vm,
>  						  XE_ENGINE_CLASS_COPY,
> -- 
> 2.43.0
>