Re: [PATCH] drm/scheduler: use hw_rq_count for load calculation

[Nayan Deshmukh <nayan26deshmukh@gmail.com>]

On Mon, Oct 22, 2018 at 9:46 PM Koenig, Christian
<Christian.Koenig@amd.com> wrote:
>
> Am 18.10.18 um 17:37 schrieb :
> > If the hardware queue for a scheduler is empty then we don't
> > need to the shift the entities from their current scheduler
> > as they are not getting scheduled because of some dependency.
>
> That is most likely not a good idea. The scheduler might not have
> anything todo right now, but we can't guarantee that it will stay this way.
>
I agree. But conversely it might also happens that one hardware engine
is sitting idle until the runqueue of the other schedulers comes to
the level of this scheduler.

I think the best option is to pick the scheduler with empty hardware
queue when the difference in their software queues is less that
MAX_DIFF. The problem is that determining the optimal value of
MAX_DIFF is not all that easy.

For now it's better to use MAX_DIFF=0 as you suggested until we can
find a way to determine its value.

Regards,
Nayan
> Instead when the number of jobs on a rq is identical we should select
> the one with the least entities on it.
>
> This should make sure that we distribute the entities equally among the
> runqueues even when they are idle.
>
> Christian.
>
> >
> > Signed-off-by: Nayan Deshmukh <nayan26deshmukh@gmail.com>
> > ---
> >   drivers/gpu/drm/scheduler/sched_entity.c | 14 ++++++++++++++
> >   1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> > index 3e22a54a99c2..4d18497d6ecf 100644
> > --- a/drivers/gpu/drm/scheduler/sched_entity.c
> > +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> > @@ -130,6 +130,12 @@ drm_sched_entity_get_free_sched(struct drm_sched_entity *entity)
> >       int i;
> >
> >       for (i = 0; i < entity->num_rq_list; ++i) {
> > +             if (atomic_read(&entity->rq_list[i]->sched->hw_rq_count) <
> > +                     entity->rq_list[i]->sched->hw_submission_limit) {
> > +                     rq = entity->rq_list[i];
> > +                     break;
> > +             }
> > +
> >               num_jobs = atomic_read(&entity->rq_list[i]->sched->num_jobs);
> >               if (num_jobs < min_jobs) {
> >                       min_jobs = num_jobs;
> > @@ -470,6 +476,14 @@ void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
> >       if (spsc_queue_count(&entity->job_queue) || entity->num_rq_list <= 1)
> >               return;
> >
> > +     /*
> > +      * We don't need to shift entity if the hardware
> > +      * queue of current scheduler is empty
> > +      */
> > +     if (atomic_read(&entity->rq->sched->hw_rq_count) <
> > +             entity->rq->sched->hw_submission_limit)
> > +             return;
> > +
> >       fence = READ_ONCE(entity->last_scheduled);
> >       if (fence && !dma_fence_is_signaled(fence))
> >               return;
>
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel