[Intel-gfx] [PATCH 01/11] drm/i915/execlists: Avoid kicking the submission too early for rescheduling

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> If the request is still waiting on external fences, it has not yet been
> submitted to the HW queue and so we can forgo kicking the submission
> tasklet when re-evaluating its priority.
>
> This should have no impact other than reducing the number of tasklet
> wakeups under signal heavy workloads (e.g. switching between engines).
>
> v2: Use prebaked container_of()
>
> References: f6322eddaff7 ("drm/i915/preemption: Allow preemption between submission ports")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Michał Winiarski <michal.winiarski at intel.com>
> Cc: Michel Thierry <michel.thierry at intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index b4ab06b05e58..104b69e0494f 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1051,12 +1051,16 @@ static void queue_request(struct intel_engine_cs *engine,
>  	list_add_tail(&pt->link, &lookup_priolist(engine, pt, prio)->requests);
>  }
>  
> -static void submit_queue(struct intel_engine_cs *engine, int prio)
> +static void __submit_queue(struct intel_engine_cs *engine, int prio)
>  {
> -	if (prio > engine->execlists.queue_priority) {
>  		engine->execlists.queue_priority = prio;
>  		tasklet_hi_schedule(&engine->execlists.tasklet);
> -	}
> +}
> +
> +static void submit_queue(struct intel_engine_cs *engine, int prio)
> +{
> +	if (prio > engine->execlists.queue_priority)
> +		__submit_queue(engine, prio);

You did this...

>  }
>  
>  static void execlists_submit_request(struct i915_request *request)
> @@ -1189,7 +1193,10 @@ static void execlists_schedule(struct i915_request *request, int prio)
>  			__list_del_entry(&pt->link);
>  			queue_request(engine, pt, prio);
>  		}
> -		submit_queue(engine, prio);
> +
> +		if (prio > engine->execlists.queue_priority &&
> +		    i915_sw_fence_done(&pt_to_request(pt)->submit))
> +			__submit_queue(engine, prio);

..to have explicit priority comparison on submit callsite I gather.
Or is there some other reason?

-Mika

>  	}
>  
>  	spin_unlock_irq(&engine->timeline->lock);
> -- 
> 2.16.3