[PATCH 2/3] drm/scheduler: add counter for total jobs in scheduler

[Nayan Deshmukh]

On Thu, Aug 2, 2018 at 11:29 AM Zhang, Jerry (Junwei) <Jerry.Zhang at amd.com>
wrote:

> On 08/02/2018 01:50 PM, Nayan Deshmukh wrote:
> >
> >
> > On Thu, Aug 2, 2018 at 10:31 AM Zhang, Jerry (Junwei) <
> Jerry.Zhang at amd.com <mailto:Jerry.Zhang at amd.com>> wrote:
> >
> >     On 07/12/2018 02:36 PM, Nayan Deshmukh wrote:
> >      > Signed-off-by: Nayan Deshmukh <nayan26deshmukh at gmail.com <mailto:
> nayan26deshmukh at gmail.com>>
> >      > ---
> >      >   drivers/gpu/drm/scheduler/gpu_scheduler.c | 3 +++
> >      >   include/drm/gpu_scheduler.h               | 2 ++
> >      >   2 files changed, 5 insertions(+)
> >      >
> >      > diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c
> b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> >      > index 429b1328653a..3dc1a4f07e3f 100644
> >      > --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
> >      > +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> >      > @@ -538,6 +538,7 @@ void drm_sched_entity_push_job(struct
> drm_sched_job *sched_job,
> >      >       trace_drm_sched_job(sched_job, entity);
> >      >
> >      >       first = spsc_queue_push(&entity->job_queue,
> &sched_job->queue_node);
> >      > +     atomic_inc(&entity->sched->num_jobs);
> >
> >     Shall we use hw_rq_count directly or merge them together?
> >
> > hw_rq_count is the number of jobs that are currently in the hardware
> queue as compared to num_jobs which is the number of jobs in the software
> queue. num_jobs provides a give a better idea of the load
> > on a scheduler that's why I added that field and used it to decide the
> scheduler with the least load.
>
> Thanks for your explanation.
>
> Then may be more reasonable to move atomic_dec(&sched->num_jobs) after
> drm_sched_fence_scheduled() or just before atomic_inc(&sched->hw_rq_count).
> How do you think that?
>
> For now num_jobs also includes jobs that have been pushed to the hardware
queue. If I shift it before atomic_inc(&sched->hw_rq_count) then I also
need to handle cases when the job was reset and update the counter
properly. I went for the easier implementation as I felt that num_jobs will
correctly represent the load on the scheduler.

But the idea that you suggested can be a potential improvement over what I
have done.

Regards,
Nayan

> Regards,
> Jerry
>
> >
> > Regards,
> > Nayan
> >
> >
> >     Regards,
> >     Jerry
> >      >
> >      >       /* first job wakes up scheduler */
> >      >       if (first) {
> >      > @@ -818,6 +819,7 @@ static void drm_sched_process_job(struct
> dma_fence *f, struct dma_fence_cb *cb)
> >      >
> >      >       dma_fence_get(&s_fence->finished);
> >      >       atomic_dec(&sched->hw_rq_count);
> >      > +     atomic_dec(&sched->num_jobs);
> >      >       drm_sched_fence_finished(s_fence);
> >      >
> >      >       trace_drm_sched_process_job(s_fence);
> >      > @@ -935,6 +937,7 @@ int drm_sched_init(struct drm_gpu_scheduler
> *sched,
> >      >       INIT_LIST_HEAD(&sched->ring_mirror_list);
> >      >       spin_lock_init(&sched->job_list_lock);
> >      >       atomic_set(&sched->hw_rq_count, 0);
> >      > +     atomic_set(&sched->num_jobs, 0);
> >      >       atomic64_set(&sched->job_id_count, 0);
> >      >
> >      >       /* Each scheduler will run on a seperate kernel thread */
> >      > diff --git a/include/drm/gpu_scheduler.h
> b/include/drm/gpu_scheduler.h
> >      > index 43e93d6077cf..605bd4ad2397 100644
> >      > --- a/include/drm/gpu_scheduler.h
> >      > +++ b/include/drm/gpu_scheduler.h
> >      > @@ -257,6 +257,7 @@ struct drm_sched_backend_ops {
> >      >    * @job_list_lock: lock to protect the ring_mirror_list.
> >      >    * @hang_limit: once the hangs by a job crosses this limit then
> it is marked
> >      >    *              guilty and it will be considered for scheduling
> further.
> >      > + * @num_jobs: the number of jobs in queue in the scheduler
> >      >    *
> >      >    * One scheduler is implemented for each hardware ring.
> >      >    */
> >      > @@ -274,6 +275,7 @@ struct drm_gpu_scheduler {
> >      >       struct list_head                ring_mirror_list;
> >      >       spinlock_t                      job_list_lock;
> >      >       int                             hang_limit;
> >      > +     atomic_t                        num_jobs;
> >      >   };
> >      >
> >      >   int drm_sched_init(struct drm_gpu_scheduler *sched,
> >      >
> >
>
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