On Fri, 2025-08-22 at 15:43 +0200, Pierre-Eric Pelloux-Prayer wrote: > Currently, the scheduler score is incremented when a job is pushed to an > entity and when an entity is attached to the scheduler.
It's indeed awkward why attaching is treated equivalently to job submission. Can you expand the documentation for drm_sched_init_args a bit so that it gets clearer what the score is supposed to do? > > This leads to some bad scheduling decision where the score value is > largely made of idle entities. > > For instance, a scenario with 2 schedulers and where 10 entities submit > a single job, then do nothing, each scheduler will probably end up with > a score of 5. > Now, 5 userspace apps exit, so their entities will be dropped. > "entities will be dropped" == "drm_sched_entity_kill() gets called", right? > In > the worst case, these apps' entities where all attached to the same s/where/were or better yet: "could be" > scheduler and we end up with score=5 (the 5 remaining entities) and > score=0, despite the 2 schedulers being idle. Sounds indeed like a (small) problem to me. > When new entities show up, they will all select the second scheduler > based on its low score value, instead of alternating between the 2. > > Some amdgpu rings depended on this feature, but the previous commit > implemented the same thing in amdgpu directly so it can be safely > removed from drm/sched. Can we be that sure that other drivers don't depend on it, though? I suspect it's likely that it's just amdgpu, but… BTW, since you're cleaning up related stuff currently: I saw that it seems that the only driver that sets &struct drm_sched_init_args.score is amdgpu. Would be cool if you can take a look whether that's still needed. P. > > Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-pra...@amd.com> > --- > drivers/gpu/drm/scheduler/sched_main.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c > b/drivers/gpu/drm/scheduler/sched_main.c > index 5a550fd76bf0..e6d232a8ec58 100644 > --- a/drivers/gpu/drm/scheduler/sched_main.c > +++ b/drivers/gpu/drm/scheduler/sched_main.c > @@ -206,7 +206,6 @@ void drm_sched_rq_add_entity(struct drm_sched_rq *rq, > if (!list_empty(&entity->list)) > return; > > - atomic_inc(rq->sched->score); > list_add_tail(&entity->list, &rq->entities); > } > > @@ -228,7 +227,6 @@ void drm_sched_rq_remove_entity(struct drm_sched_rq *rq, > > spin_lock(&rq->lock); > > - atomic_dec(rq->sched->score); > list_del_init(&entity->list); > > if (rq->current_entity == entity)
