[RFC 16/18] drm/sched: Connect with dma-fence deadlines

[Christian König]

Am 08.01.25 um 19:35 schrieb Tvrtko Ursulin:
> Now that the scheduling policy is deadline based it feels completely
> natural to allow propagating externaly set deadlines to the scheduler.
>
> Scheduler deadlines are not a guarantee but as the dma-fence facility is
> already in use by userspace lets wire it up.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Danilo Krummrich <dakr at redhat.com>
> Cc: Matthew Brost <matthew.brost at intel.com>
> Cc: Philipp Stanner <pstanner at redhat.com>
> Cc: Rob Clark <robdclark at gmail.com>
> ---
>   drivers/gpu/drm/scheduler/sched_entity.c | 24 ++++++++++++++++++++++--
>   1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> index 98c78d1373d8..db5d34310b18 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -410,7 +410,16 @@ ktime_t
>   drm_sched_entity_get_job_deadline(struct drm_sched_entity *entity,
>   				  struct drm_sched_job *job)
>   {
> -	return __drm_sched_entity_get_job_deadline(entity, job->submit_ts);
> +	struct drm_sched_fence *s_fence = job->s_fence;
> +	struct dma_fence *fence = &s_fence->finished;
> +	ktime_t deadline;
> +
> +	deadline = __drm_sched_entity_get_job_deadline(entity, job->submit_ts);
> +	if (test_bit(DRM_SCHED_FENCE_FLAG_HAS_DEADLINE_BIT, &fence->flags) &&
> +	    ktime_before(s_fence->deadline, deadline))
> +		deadline = s_fence->deadline;
> +
> +	return deadline;
>   }
>   
>   /*
> @@ -579,9 +588,12 @@ void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
>    */
>   void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
>   {
> +	struct drm_sched_fence *s_fence = sched_job->s_fence;
>   	struct drm_sched_entity *entity = sched_job->entity;
> -	bool first;
> +	struct dma_fence *fence = &s_fence->finished;
> +	ktime_t fence_deadline;
>   	ktime_t submit_ts;
> +	bool first;
>   
>   	trace_drm_sched_job(sched_job, entity);
>   	atomic_inc(entity->rq->sched->score);
> @@ -593,6 +605,11 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
>   	 * Make sure to set the submit_ts first, to avoid a race.
>   	 */
>   	sched_job->submit_ts = submit_ts = ktime_get();
> +	if (test_bit(DRM_SCHED_FENCE_FLAG_HAS_DEADLINE_BIT, &fence->flags))
> +		fence_deadline = s_fence->deadline;
> +	else
> +		fence_deadline = KTIME_MAX;
> +

That makes no sense. When the job is pushed the fence is not made public 
yet.

So no deadline can be set on the fence.

>   	first = spsc_queue_push(&entity->job_queue, &sched_job->queue_node);
>   
>   	/* first job wakes up scheduler */
> @@ -601,6 +618,9 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
>   
>   		submit_ts = __drm_sched_entity_get_job_deadline(entity,
>   								submit_ts);
> +		if (ktime_before(fence_deadline, submit_ts))
> +			submit_ts = fence_deadline;
> +

Yeah, that won't work at all as far as I can see.

Regards,
Christian.

>   		sched = drm_sched_rq_add_entity(entity->rq, entity, submit_ts);
>   		if (sched)
>   			drm_sched_wakeup(sched);