Re: [Intel-gfx] [PATCH 3/9] drm/i915: Add i915_sched_engine_reset_on_empty function

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

On Fri, Jun 04, 2021 at 01:31:42PM -0500, Jason Ekstrand wrote:
> On Thu, Jun 3, 2021 at 4:09 PM Matthew Brost <matthew.brost@intel.com> wrote:
> >
> > Rather than touching schedule state in the generic PM code, reset the
> > priolist allocation when empty in the submission code. Add a wrapper
> > function to do this and update the backends to call it in the correct
> > place.
> 
> Seems reasonable, I think.  I'm by no means an expert but
> 
> Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
> 
> anyway.  My one suggestion would be to tweak the commit message to
> talk about the functional change rather than the helper.  Something
> like
> 
> drm/i915: Reset sched_engine.no_priolist immediately after dequeue
> 
> Typically patches which say "add a helper function" don't come with a
> non-trivial functional change.
> 

Agree.

Thanks - Matt

> --Jason
> 
> 
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_engine_pm.c            | 2 --
> >  drivers/gpu/drm/i915/gt/intel_execlists_submission.c | 1 +
> >  drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c    | 2 ++
> >  drivers/gpu/drm/i915/i915_scheduler.h                | 7 +++++++
> >  4 files changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> > index b6a00dd72808..1f07ac4e0672 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> > @@ -280,8 +280,6 @@ static int __engine_park(struct intel_wakeref *wf)
> >         if (engine->park)
> >                 engine->park(engine);
> >
> > -       engine->sched_engine->no_priolist = false;
> > -
> >         /* While gt calls i915_vma_parked(), we have to break the lock cycle */
> >         intel_gt_pm_put_async(engine->gt);
> >         return 0;
> > diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > index 2326a73af6d3..609753b5401a 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > @@ -1553,6 +1553,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
> >          * interrupt for secondary ports).
> >          */
> >         sched_engine->queue_priority_hint = queue_prio(sched_engine);
> > +       i915_sched_engine_reset_on_empty(sched_engine);
> >         spin_unlock(&engine->active.lock);
> >
> >         /*
> > 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 5d00f2e3c1de..f4a6fbfaf82e 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -263,6 +263,8 @@ static void guc_submission_tasklet(struct tasklet_struct *t)
> >
> >         __guc_dequeue(engine);
> >
> > +       i915_sched_engine_reset_on_empty(engine->sched_engine);
> > +
> >         spin_unlock_irqrestore(&engine->active.lock, flags);
> >  }
> >
> > diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
> > index 5bec7b3b8456..713c38c99de9 100644
> > --- a/drivers/gpu/drm/i915/i915_scheduler.h
> > +++ b/drivers/gpu/drm/i915/i915_scheduler.h
> > @@ -72,6 +72,13 @@ i915_sched_engine_is_empty(struct i915_sched_engine *sched_engine)
> >         return RB_EMPTY_ROOT(&sched_engine->queue.rb_root);
> >  }
> >
> > +static inline void
> > +i915_sched_engine_reset_on_empty(struct i915_sched_engine *sched_engine)
> > +{
> > +       if (i915_sched_engine_is_empty(sched_engine))
> > +               sched_engine->no_priolist = false;
> > +}
> > +
> >  void i915_request_show_with_schedule(struct drm_printer *m,
> >                                      const struct i915_request *rq,
> >                                      const char *prefix,
> > --
> > 2.28.0
> >
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