On Sat, 2025-10-11 at 15:19 +0100, Tvrtko Ursulin wrote:
>
> On 10/10/2025 11:49, Philipp Stanner wrote:
> > On Wed, 2025-10-08 at 09:53 +0100, Tvrtko Ursulin wrote:
> > > Move the code dealing with entities entering and exiting run queues to
> > > helpers to logically separate it from jobs entering and exiting entities.
> > >
> > > Signed-off-by: Tvrtko Ursulin <[email protected]>
> > > Cc: Christian König <[email protected]>
> > > Cc: Danilo Krummrich <[email protected]>
> > > Cc: Matthew Brost <[email protected]>
> > > Cc: Philipp Stanner <[email protected]>
> > > ---
> > > drivers/gpu/drm/scheduler/sched_entity.c | 64 ++-------------
> > > drivers/gpu/drm/scheduler/sched_internal.h | 8 +-
> > > drivers/gpu/drm/scheduler/sched_main.c | 95 +++++++++++++++++++---
> > > 3 files changed, 91 insertions(+), 76 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/scheduler/sched_entity.c
> > > b/drivers/gpu/drm/scheduler/sched_entity.c
> > > index 4852006f2308..7a0a52ba87bf 100644
> > > --- a/drivers/gpu/drm/scheduler/sched_entity.c
> > > +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> > > @@ -456,24 +456,9 @@ drm_sched_job_dependency(struct drm_sched_job *job,
> > > return NULL;
> > > }
> > >
> > > -static ktime_t
> > > -drm_sched_rq_get_rr_ts(struct drm_sched_rq *rq, struct drm_sched_entity
> > > *entity)
> > > -{
> > > - ktime_t ts;
> > > -
> > > - lockdep_assert_held(&entity->lock);
> > > - lockdep_assert_held(&rq->lock);
> > > -
> > > - ts = ktime_add_ns(rq->rr_ts, 1);
> > > - entity->rr_ts = ts;
> > > - rq->rr_ts = ts;
> > > -
> > > - return ts;
> > > -}
> > > -
> > > struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity
> > > *entity)
> > > {
> > > - struct drm_sched_job *sched_job, *next_job;
> > > + struct drm_sched_job *sched_job;
> >
> > `next_job` has been added in a previous job. Have you tried whether
> > patch-order can be reversed?
> >
> > Just asking; I don't want to cause unnecessary work here
>
> You are correct that there would be some knock on effect on a few other
> patches in the series but it is definitely doable. Because for certain
> argument can be made it would be logical to have it like that. Both this
> patch and "drm/sched: Move run queue related code into a separate file"
> would be then moved ahead of "drm/sched: Implement RR via FIFO". If you
> prefer it like that I can reshuffle no problem.
I mean, it seems to make the overall git diff smaller, which is nice?
If you don't see a significant reason against it, I'd say it's a good
idea.
>
> > >
> > > sched_job = drm_sched_entity_queue_peek(entity);
> > > if (!sched_job)
> > > @@ -502,26 +487,7 @@ struct drm_sched_job
> > > *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
> > >
> > > spsc_queue_pop(&entity->job_queue);
> > >
> > > - /*
> > > - * Update the entity's location in the min heap according to
> > > - * the timestamp of the next job, if any.
> > > - */
> > > - next_job = drm_sched_entity_queue_peek(entity);
> > > - if (next_job) {
> > > - struct drm_sched_rq *rq;
> > > - ktime_t ts;
> > > -
> > > - spin_lock(&entity->lock);
> > > - rq = entity->rq;
> > > - spin_lock(&rq->lock);
> > > - if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
> > > - ts = next_job->submit_ts;
> > > - else
> > > - ts = drm_sched_rq_get_rr_ts(rq, entity);
> > > - drm_sched_rq_update_fifo_locked(entity, rq, ts);
> > > - spin_unlock(&rq->lock);
> > > - spin_unlock(&entity->lock);
> > > - }
> > > + drm_sched_rq_pop_entity(entity);
> > >
> > > /* Jobs and entities might have different lifecycles. Since
> > > we're
> > > * removing the job from the entities queue, set the jobs
> > > entity pointer
> > > @@ -611,30 +577,10 @@ void drm_sched_entity_push_job(struct drm_sched_job
> > > *sched_job)
> > > /* first job wakes up scheduler */
> > > if (first) {
> > > struct drm_gpu_scheduler *sched;
> > > - struct drm_sched_rq *rq;
> > >
> > > - /* Add the entity to the run queue */
> > > - spin_lock(&entity->lock);
> > > - if (entity->stopped) {
> > > - spin_unlock(&entity->lock);
> > > -
> > > - DRM_ERROR("Trying to push to a killed entity\n");
> > > - return;
> > > - }
> > > -
> > > - rq = entity->rq;
> > > - sched = rq->sched;
> > > -
> > > - spin_lock(&rq->lock);
> > > - drm_sched_rq_add_entity(rq, entity);
> > > - if (drm_sched_policy == DRM_SCHED_POLICY_RR)
> > > - submit_ts = entity->rr_ts;
> > > - drm_sched_rq_update_fifo_locked(entity, rq, submit_ts);
> > > -
> > > - spin_unlock(&rq->lock);
> > > - spin_unlock(&entity->lock);
> > > -
> > > - drm_sched_wakeup(sched);
> > > + sched = drm_sched_rq_add_entity(entity, submit_ts);
> > > + if (sched)
> > > + drm_sched_wakeup(sched);
> > > }
> > > }
> > > EXPORT_SYMBOL(drm_sched_entity_push_job);
> > > diff --git a/drivers/gpu/drm/scheduler/sched_internal.h
> > > b/drivers/gpu/drm/scheduler/sched_internal.h
> > > index 7ea5a6736f98..8269c5392a82 100644
> > > --- a/drivers/gpu/drm/scheduler/sched_internal.h
> > > +++ b/drivers/gpu/drm/scheduler/sched_internal.h
> > > @@ -12,13 +12,11 @@ extern int drm_sched_policy;
> > >
> > > void drm_sched_wakeup(struct drm_gpu_scheduler *sched);
> > >
> > > -void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
> > > - struct drm_sched_entity *entity);
> > > +struct drm_gpu_scheduler *
> > > +drm_sched_rq_add_entity(struct drm_sched_entity *entity, ktime_t ts);
> > > void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
> > > struct drm_sched_entity *entity);
> > > -
> > > -void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity,
> > > - struct drm_sched_rq *rq, ktime_t ts);
> > > +void drm_sched_rq_pop_entity(struct drm_sched_entity *entity);
> > >
> > > void drm_sched_entity_select_rq(struct drm_sched_entity *entity);
> > > struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity
> > > *entity);
> > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c
> > > b/drivers/gpu/drm/scheduler/sched_main.c
> > > index 8e62541b439a..e5d02c28665c 100644
> > > --- a/drivers/gpu/drm/scheduler/sched_main.c
> > > +++ b/drivers/gpu/drm/scheduler/sched_main.c
> > > @@ -151,9 +151,9 @@ static void drm_sched_rq_remove_fifo_locked(struct
> > > drm_sched_entity *entity,
> > > }
> > > }
> > >
> > > -void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity,
> > > - struct drm_sched_rq *rq,
> > > - ktime_t ts)
> > > +static void drm_sched_rq_update_fifo_locked(struct drm_sched_entity
> > > *entity,
> > > + struct drm_sched_rq *rq,
> > > + ktime_t ts)
> > > {
> > > /*
> > > * Both locks need to be grabbed, one to protect from
> > > entity->rq change
> > > @@ -191,22 +191,45 @@ static void drm_sched_rq_init(struct drm_sched_rq
> > > *rq,
> > > /**
> > > * drm_sched_rq_add_entity - add an entity
> > > *
> > > - * @rq: scheduler run queue
> > > * @entity: scheduler entity
> > > + * @ts: submission timestamp
> > > *
> > > * Adds a scheduler entity to the run queue.
> > > + *
> > > + * Returns a DRM scheduler pre-selected to handle this entity.
> > > */
> > > -void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
> > > - struct drm_sched_entity *entity)
> > > +struct drm_gpu_scheduler *
> > > +drm_sched_rq_add_entity(struct drm_sched_entity *entity, ktime_t ts)
> > > {
> >
> > I'm not sure if it's a good idea to have the scheduler returned from
> > that function. That doesn't make a whole lot of sense semantically.
> >
> > At the very least the function's docstring, maybe even its name, should
> > be adjusted to detail why this makes sense. The commit message, too.
> > It's not trivially understood.
> >
> > I think I get why it's being done, but writing it down black on white
> > gives us something to grasp.
> >
> > Sth like "adds an entity to a runqueue, selects to appropriate
> > scheduler and returns it for the purpose of XYZ"
>
> Yeah. Remeber your unlocked rq access slide and the discussion around it?
Sure. Is that related, though? The slide was about many readers being
totally unlocked. The current drm_sched_entity_push_job() locks readers
correctly if I'm not mistaken.
>
> Currently we have this:
>
> drm_sched_entity_push_job()
> {
> ...
> spin_lock(&entity->lock);
> ...
> rq = entity->rq;
> sched = rq->sched;
> ...
> spin_unlock(&rq->lock);
> spin_unlock(&entity->lock);
>
> drm_sched_wakeup(sched);
>
> Ie. we know entity->rq and rq->sched are guaranteed to be stable and
> present at this point because job is already in the queue and
> drm_sched_entity_select_rq() guarantees that.
>
> In this patch I moved all this block into drm_sched_rq_add_entity() but
> I wanted to leave drm_sched_wakeup() outside. Because I thought it is
> not the job of the run queue handling, and semantically the logic was
> "only once added to the entity we know the rq and scheduler for
> certain". That would open the door for future improvements and late
> rq/scheduler selection.
>
> But now I think it is premature and it would be better I simply move the
> wakekup inside drm_sched_rq_add_entity() together with all the rest.
>
> Does that sound like a plan for now?
Hmmm. What I'm wondering most about if it really is a good idea to have
drm_sched_wakeup() in rq_add_entity().
Do you think that makes semantically more sense than just reading:
drm_sched_entity_push_job()
{
foo
bar
more_foo
/* New job was added. Right time to wake up scheduler. */
drm_sched_wakeup();
I think both can make sense, but the above / current version seems to
make more sense to me.
P.
>
> Regards,
>
> Tvrtko
>
> >
> > > - lockdep_assert_held(&entity->lock);
> > > - lockdep_assert_held(&rq->lock);
> > > + struct drm_gpu_scheduler *sched;
> > > + struct drm_sched_rq *rq;
> > >
> > > - if (!list_empty(&entity->list))
> > > - return;
> > > + /* Add the entity to the run queue */
> > > + spin_lock(&entity->lock);
> > > + if (entity->stopped) {
> > > + spin_unlock(&entity->lock);
> > >
> > > - atomic_inc(rq->sched->score);
> > > - list_add_tail(&entity->list, &rq->entities);
> > > + DRM_ERROR("Trying to push to a killed entity\n");
> > > + return NULL;
> > > + }
> > > +
> > > + rq = entity->rq;
> > > + spin_lock(&rq->lock);
> > > + sched = rq->sched;
> > > +
> > > + if (list_empty(&entity->list)) {
> > > + atomic_inc(sched->score);
> > > + list_add_tail(&entity->list, &rq->entities);
> > > + }
> > > +
> > > + if (drm_sched_policy == DRM_SCHED_POLICY_RR)
> > > + ts = entity->rr_ts;
> > > + drm_sched_rq_update_fifo_locked(entity, rq, ts);
> > > +
> > > + spin_unlock(&rq->lock);
> > > + spin_unlock(&entity->lock);
> > > +
> > > + return sched;
> > > }
> > >
> > > /**
> > > @@ -235,6 +258,54 @@ void drm_sched_rq_remove_entity(struct drm_sched_rq
> > > *rq,
> > > spin_unlock(&rq->lock);
> > > }
> > >
> > > +static ktime_t
> > > +drm_sched_rq_get_rr_ts(struct drm_sched_rq *rq, struct drm_sched_entity
> > > *entity)
> > > +{
> > > + ktime_t ts;
> > > +
> > > + lockdep_assert_held(&entity->lock);
> > > + lockdep_assert_held(&rq->lock);
> > > +
> > > + ts = ktime_add_ns(rq->rr_ts, 1);
> > > + entity->rr_ts = ts;
> > > + rq->rr_ts = ts;
> >
> > I mentioned that pattern in a previous patch. "get_rr_ts" doesn't
> > appear like an obvious name since you're actually setting data here.
> >
> > P.
> >
> > > +
> > > + return ts;
> > > +}
> > > +
> > > +/**
> > > + * drm_sched_rq_pop_entity - pops an entity
> > > + *
> > > + * @entity: scheduler entity
> > > + *
> > > + * To be called every time after a job is popped from the entity.
> > > + */
> > > +void drm_sched_rq_pop_entity(struct drm_sched_entity *entity)
> > > +{
> > > + struct drm_sched_job *next_job;
> > > + struct drm_sched_rq *rq;
> > > + ktime_t ts;
> > > +
> > > + /*
> > > + * Update the entity's location in the min heap according to
> > > + * the timestamp of the next job, if any.
> > > + */
> > > + next_job = drm_sched_entity_queue_peek(entity);
> > > + if (!next_job)
> > > + return;
> > > +
> > > + spin_lock(&entity->lock);
> > > + rq = entity->rq;
> > > + spin_lock(&rq->lock);
> > > + if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
> > > + ts = next_job->submit_ts;
> > > + else
> > > + ts = drm_sched_rq_get_rr_ts(rq, entity);
> > > + drm_sched_rq_update_fifo_locked(entity, rq, ts);
> > > + spin_unlock(&rq->lock);
> > > + spin_unlock(&entity->lock);
> > > +}
> > > +
> > > /**
> > > * drm_sched_rq_select_entity - Select an entity which provides a job
> > > to run
> > > *
> >
>
