Re: [Intel-gfx] [PATCH 09/27] drm/i915/guc: Kick tasklet after queuing a request

[Matthew Brost <matthew.brost@intel.com>]

On Fri, Aug 20, 2021 at 11:31:56AM -0700, Daniele Ceraolo Spurio wrote:
> 
> 
> On 8/18/2021 11:16 PM, Matthew Brost wrote:
> > Kick tasklet after queuing a request so it submitted in a timely manner.
> > 
> > Fixes: 3a4cdf1982f0 ("drm/i915/guc: Implement GuC context operations for new inteface")
> 
> Is this actually a bug or just a performance issue? in the latter case I
> don't think we need a fixes tag.
> 

Basically the tasklet won't get queued in certain ituations until the
heartbeat ping. Didn't notice it as the tasklet is only used during flow
control or after a full GT reset which both are rather rare. We can
probably drop the fixes tag as GuC submission isn't on by default is
still works without this fix.

> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >   drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > index 8f7a11e65ef5..d61f906105ef 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -1050,6 +1050,7 @@ static inline void queue_request(struct i915_sched_engine *sched_engine,
> >   	list_add_tail(&rq->sched.link,
> >   		      i915_sched_lookup_priolist(sched_engine, prio));
> >   	set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
> > +	tasklet_hi_schedule(&sched_engine->tasklet);
> 
> the caller of queue_request() already has a tasklet_hi_schedule in another
> branch of the if/else statement. Maybe we can have the caller own the kick
> to keep it in one place? Not a blocker.
>

I guess it could be:

bool kick = need_taklet()

if (kick)
	queue_requst()
else
	kick = bypass()
if (kick)
	kick_tasklet()

Idk, it that is better? I'll think on this and decide before the next
post.

Matt

> Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> 
> Daniele
> 
> >   }
> >   static int guc_bypass_tasklet_submit(struct intel_guc *guc,
>