Re: [Intel-gfx] [PATCH] drm/i915/execlists: Enable timeslice on partial virtual engine dequeue

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

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

> If we stop filling the ELSP due to an incompatible virtual engine
> request, check if we should enable the timeslice on behalf of the queue.
>

Leaves me pondering more of the why.

So that on these boundaries also, the last rq gets subdued to
a timeslice and not get a free run?

> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/gt/intel_lrc.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 5da86a40434c..954bd4797482 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1802,6 +1802,20 @@ static void set_timeslice(struct intel_engine_cs *engine)
>  	set_timer_ms(&engine->execlists.timer, active_timeslice(engine));
>  }
>  
> +static void start_timeslice(struct intel_engine_cs *engine,
> +			    struct i915_request *last)
> +{
> +	struct intel_engine_execlists *execlists = &engine->execlists;
> +
> +	/* As we are returning early, update the hint from the queue */
> +	execlists->switch_priority_hint =
> +		max(execlists->queue_priority_hint,
> +		    execlists->switch_priority_hint);
> +
> +	if (!execlists->timer.expires && need_timeslice(engine, last))
> +		set_timer_ms(&execlists->timer, timeslice(engine));
> +}
> +
>  static void record_preemption(struct intel_engine_execlists *execlists)
>  {
>  	(void)I915_SELFTEST_ONLY(execlists->preempt_hang.count++);
> @@ -1965,11 +1979,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>  				 * Even if ELSP[1] is occupied and not worthy
>  				 * of timeslices, our queue might be.
>  				 */
> -				if (!execlists->timer.expires &&
> -				    need_timeslice(engine, last))
> -					set_timer_ms(&execlists->timer,
> -						     timeslice(engine));
> -
> +				start_timeslice(engine, last);
>  				return;
>  			}
>  		}
> @@ -2004,6 +2014,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
>  
>  			if (last && !can_merge_rq(last, rq)) {
>  				spin_unlock(&ve->base.active.lock);
> +				start_timeslice(engine, last);
>  				return; /* leave this for another */

for another interrupt?
-Mika

>  			}
>  
> -- 
> 2.25.1
>
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