Re: [Intel-xe] [PATCH v3 05/13] drm/sched: Split free_job into own work item

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

On Tue, Sep 12, 2023 at 10:08:33AM +0200, Boris Brezillon wrote:
> On Mon, 11 Sep 2023 19:16:07 -0700
> Matthew Brost <matthew.brost@intel.com> wrote:
> 
> > Rather than call free_job and run_job in same work item have a dedicated
> > work item for each. This aligns with the design and intended use of work
> > queues.
> > 
> > v2:
> >    - Test for DMA_FENCE_FLAG_TIMESTAMP_BIT before setting
> >      timestamp in free_job() work item (Danilo)
> > 
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >  drivers/gpu/drm/scheduler/sched_main.c | 143 ++++++++++++++++++-------
> >  include/drm/gpu_scheduler.h            |   8 +-
> >  2 files changed, 110 insertions(+), 41 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> > index 3820e9ae12c8..d28b6751256e 100644
> > --- a/drivers/gpu/drm/scheduler/sched_main.c
> > +++ b/drivers/gpu/drm/scheduler/sched_main.c
> > @@ -213,11 +213,12 @@ void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
> >   * drm_sched_rq_select_entity_rr - Select an entity which could provide a job to run
> >   *
> >   * @rq: scheduler run queue to check.
> > + * @dequeue: dequeue selected entity
> >   *
> >   * Try to find a ready entity, returns NULL if none found.
> >   */
> >  static struct drm_sched_entity *
> > -drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq)
> > +drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq, bool dequeue)
> >  {
> >  	struct drm_sched_entity *entity;
> >  
> > @@ -227,8 +228,10 @@ drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq)
> >  	if (entity) {
> >  		list_for_each_entry_continue(entity, &rq->entities, list) {
> >  			if (drm_sched_entity_is_ready(entity)) {
> > -				rq->current_entity = entity;
> > -				reinit_completion(&entity->entity_idle);
> > +				if (dequeue) {
> > +					rq->current_entity = entity;
> > +					reinit_completion(&entity->entity_idle);
> > +				}
> >  				spin_unlock(&rq->lock);
> >  				return entity;
> >  			}
> > @@ -238,8 +241,10 @@ drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq)
> >  	list_for_each_entry(entity, &rq->entities, list) {
> >  
> >  		if (drm_sched_entity_is_ready(entity)) {
> > -			rq->current_entity = entity;
> > -			reinit_completion(&entity->entity_idle);
> > +			if (dequeue) {
> > +				rq->current_entity = entity;
> > +				reinit_completion(&entity->entity_idle);
> > +			}
> >  			spin_unlock(&rq->lock);
> >  			return entity;
> >  		}
> > @@ -257,11 +262,12 @@ drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq)
> >   * drm_sched_rq_select_entity_fifo - Select an entity which provides a job to run
> >   *
> >   * @rq: scheduler run queue to check.
> > + * @dequeue: dequeue selected entity
> >   *
> >   * Find oldest waiting ready entity, returns NULL if none found.
> >   */
> >  static struct drm_sched_entity *
> > -drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq)
> > +drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq, bool dequeue)
> >  {
> >  	struct rb_node *rb;
> >  
> > @@ -271,8 +277,10 @@ drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq)
> >  
> >  		entity = rb_entry(rb, struct drm_sched_entity, rb_tree_node);
> >  		if (drm_sched_entity_is_ready(entity)) {
> > -			rq->current_entity = entity;
> > -			reinit_completion(&entity->entity_idle);
> > +			if (dequeue) {
> > +				rq->current_entity = entity;
> > +				reinit_completion(&entity->entity_idle);
> > +			}
> >  			break;
> >  		}
> >  	}
> > @@ -282,13 +290,54 @@ drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq)
> >  }
> >  
> >  /**
> > - * drm_sched_submit_queue - scheduler queue submission
> > + * drm_sched_run_job_queue - queue job submission
> >   * @sched: scheduler instance
> >   */
> > -static void drm_sched_submit_queue(struct drm_gpu_scheduler *sched)
> > +static void drm_sched_run_job_queue(struct drm_gpu_scheduler *sched)
> >  {
> >  	if (!READ_ONCE(sched->pause_submit))
> > -		queue_work(sched->submit_wq, &sched->work_submit);
> > +		queue_work(sched->submit_wq, &sched->work_run_job);
> > +}
> > +
> > +static struct drm_sched_entity *
> > +drm_sched_select_entity(struct drm_gpu_scheduler *sched, bool dequeue);
> 
> Nit: Can you drop this forward declaration and move the function here?
>

Sure. Will likely move this function in a seperate patch though.
 
> > +
> > +/**
> > + * drm_sched_run_job_queue_if_ready - queue job submission if ready
> > + * @sched: scheduler instance
> > + */
> > +static void drm_sched_run_job_queue_if_ready(struct drm_gpu_scheduler *sched)
> > +{
> > +	if (drm_sched_select_entity(sched, false))
> > +		drm_sched_run_job_queue(sched);
> > +}
> > +
> > +/**
> > + * drm_sched_free_job_queue - queue free job
> > + *
> > + * @sched: scheduler instance to queue free job
> > + */
> > +static void drm_sched_free_job_queue(struct drm_gpu_scheduler *sched)
> > +{
> > +	if (!READ_ONCE(sched->pause_submit))
> > +		queue_work(sched->submit_wq, &sched->work_free_job);
> > +}
> > +
> > +/**
> > + * drm_sched_free_job_queue_if_ready - queue free job if ready
> > + *
> > + * @sched: scheduler instance to queue free job
> > + */
> > +static void drm_sched_free_job_queue_if_ready(struct drm_gpu_scheduler *sched)
> > +{
> > +	struct drm_sched_job *job;
> > +
> > +	spin_lock(&sched->job_list_lock);
> > +	job = list_first_entry_or_null(&sched->pending_list,
> > +				       struct drm_sched_job, list);
> > +	if (job && dma_fence_is_signaled(&job->s_fence->finished))
> > +		drm_sched_free_job_queue(sched);
> > +	spin_unlock(&sched->job_list_lock);
> >  }
> >  
> >  /**
> > @@ -310,7 +359,7 @@ static void drm_sched_job_done(struct drm_sched_job *s_job, int result)
> >  	dma_fence_get(&s_fence->finished);
> >  	drm_sched_fence_finished(s_fence, result);
> >  	dma_fence_put(&s_fence->finished);
> > -	drm_sched_submit_queue(sched);
> > +	drm_sched_free_job_queue(sched);
> >  }
> >  
> >  /**
> > @@ -906,18 +955,19 @@ static bool drm_sched_can_queue(struct drm_gpu_scheduler *sched)
> >  void drm_sched_wakeup_if_can_queue(struct drm_gpu_scheduler *sched)
> >  {
> >  	if (drm_sched_can_queue(sched))
> > -		drm_sched_submit_queue(sched);
> > +		drm_sched_run_job_queue(sched);
> >  }
> >  
> >  /**
> >   * drm_sched_select_entity - Select next entity to process
> >   *
> >   * @sched: scheduler instance
> > + * @dequeue: dequeue selected entity
> >   *
> >   * Returns the entity to process or NULL if none are found.
> >   */
> >  static struct drm_sched_entity *
> > -drm_sched_select_entity(struct drm_gpu_scheduler *sched)
> > +drm_sched_select_entity(struct drm_gpu_scheduler *sched, bool dequeue)
> >  {
> >  	struct drm_sched_entity *entity;
> >  	int i;
> > @@ -936,8 +986,10 @@ drm_sched_select_entity(struct drm_gpu_scheduler *sched)
> >  	/* Kernel run queue has higher priority than normal run queue*/
> >  	for (i = DRM_SCHED_PRIORITY_COUNT - 1; i >= DRM_SCHED_PRIORITY_MIN; i--) {
> >  		entity = sched->sched_policy == DRM_SCHED_POLICY_FIFO ?
> > -			drm_sched_rq_select_entity_fifo(&sched->sched_rq[i]) :
> > -			drm_sched_rq_select_entity_rr(&sched->sched_rq[i]);
> > +			drm_sched_rq_select_entity_fifo(&sched->sched_rq[i],
> > +							dequeue) :
> > +			drm_sched_rq_select_entity_rr(&sched->sched_rq[i],
> > +						      dequeue);
> >  		if (entity)
> >  			break;
> >  	}
> > @@ -974,8 +1026,10 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
> >  						typeof(*next), list);
> >  
> >  		if (next) {
> > -			next->s_fence->scheduled.timestamp =
> > -				job->s_fence->finished.timestamp;
> > +			if (test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT,
> > +				     &next->s_fence->scheduled.flags))
> > +				next->s_fence->scheduled.timestamp =
> > +					job->s_fence->finished.timestamp;
> 
> Looks like you are changing the behavior here (unconditional ->
> conditional timestamp update)? Probably something that should go in a
> separate patch.
> 

This patch creates a race so this check isn't need before this patch.
With that I think it makes sense to have all in a single patch. If you
feel strongly about this, I can break this change out into a patch prior
to this one.

> >  			/* start TO timer for next job */
> >  			drm_sched_start_timeout(sched);
> >  		}
> > @@ -1025,30 +1079,44 @@ drm_sched_pick_best(struct drm_gpu_scheduler **sched_list,
> >  EXPORT_SYMBOL(drm_sched_pick_best);
> >  
> >  /**
> > - * drm_sched_main - main scheduler thread
> > + * drm_sched_free_job_work - worker to call free_job
> >   *
> > - * @param: scheduler instance
> > + * @w: free job work
> >   */
> > -static void drm_sched_main(struct work_struct *w)
> > +static void drm_sched_free_job_work(struct work_struct *w)
> >  {
> >  	struct drm_gpu_scheduler *sched =
> > -		container_of(w, struct drm_gpu_scheduler, work_submit);
> > -	struct drm_sched_entity *entity;
> > +		container_of(w, struct drm_gpu_scheduler, work_free_job);
> >  	struct drm_sched_job *cleanup_job;
> > -	int r;
> >  
> >  	if (READ_ONCE(sched->pause_submit))
> >  		return;
> >  
> >  	cleanup_job = drm_sched_get_cleanup_job(sched);
> > -	entity = drm_sched_select_entity(sched);
> > +	if (cleanup_job) {
> > +		sched->ops->free_job(cleanup_job);
> > +
> > +		drm_sched_free_job_queue_if_ready(sched);
> > +		drm_sched_run_job_queue_if_ready(sched);
> > +	}
> > +}
> >  
> > -	if (!entity && !cleanup_job)
> > -		return;	/* No more work */
> > +/**
> > + * drm_sched_run_job_work - worker to call run_job
> > + *
> > + * @w: run job work
> > + */
> > +static void drm_sched_run_job_work(struct work_struct *w)
> > +{
> > +	struct drm_gpu_scheduler *sched =
> > +		container_of(w, struct drm_gpu_scheduler, work_run_job);
> > +	struct drm_sched_entity *entity;
> > +	int r;
> >  
> > -	if (cleanup_job)
> > -		sched->ops->free_job(cleanup_job);
> > +	if (READ_ONCE(sched->pause_submit))
> > +		return;
> >  
> > +	entity = drm_sched_select_entity(sched, true);
> 
> Nit:
> 
> 	if (!entity)
> 		return;
> 
> then you can save an indentation level for the rest of the function.
>

Sure.

Matt
 
> >  	if (entity) {
> >  		struct dma_fence *fence;
> >  		struct drm_sched_fence *s_fence;
> > @@ -1057,9 +1125,7 @@ static void drm_sched_main(struct work_struct *w)
> >  		sched_job = drm_sched_entity_pop_job(entity);
> >  		if (!sched_job) {
> >  			complete_all(&entity->entity_idle);
> > -			if (!cleanup_job)
> > -				return;	/* No more work */
> > -			goto again;
> > +			return;	/* No more work */
> >  		}
> >  
> >  		s_fence = sched_job->s_fence;
> > @@ -1089,10 +1155,8 @@ static void drm_sched_main(struct work_struct *w)
> >  		}
> >  
> >  		wake_up(&sched->job_scheduled);
> > +		drm_sched_run_job_queue_if_ready(sched);
> >  	}
> > -
> > -again:
> > -	drm_sched_submit_queue(sched);
> >  }
> >  
> >  /**
> > @@ -1151,7 +1215,8 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
> >  	spin_lock_init(&sched->job_list_lock);
> >  	atomic_set(&sched->hw_rq_count, 0);
> >  	INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
> > -	INIT_WORK(&sched->work_submit, drm_sched_main);
> > +	INIT_WORK(&sched->work_run_job, drm_sched_run_job_work);
> > +	INIT_WORK(&sched->work_free_job, drm_sched_free_job_work);
> >  	atomic_set(&sched->_score, 0);
> >  	atomic64_set(&sched->job_id_count, 0);
> >  	sched->pause_submit = false;
> > @@ -1276,7 +1341,8 @@ EXPORT_SYMBOL(drm_sched_submit_ready);
> >  void drm_sched_submit_stop(struct drm_gpu_scheduler *sched)
> >  {
> >  	WRITE_ONCE(sched->pause_submit, true);
> > -	cancel_work_sync(&sched->work_submit);
> > +	cancel_work_sync(&sched->work_run_job);
> > +	cancel_work_sync(&sched->work_free_job);
> >  }
> >  EXPORT_SYMBOL(drm_sched_submit_stop);
> >  
> > @@ -1288,6 +1354,7 @@ EXPORT_SYMBOL(drm_sched_submit_stop);
> >  void drm_sched_submit_start(struct drm_gpu_scheduler *sched)
> >  {
> >  	WRITE_ONCE(sched->pause_submit, false);
> > -	queue_work(sched->submit_wq, &sched->work_submit);
> > +	queue_work(sched->submit_wq, &sched->work_run_job);
> > +	queue_work(sched->submit_wq, &sched->work_free_job);
> >  }
> >  EXPORT_SYMBOL(drm_sched_submit_start);
> > diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> > index 04eec2d7635f..fbc083a92757 100644
> > --- a/include/drm/gpu_scheduler.h
> > +++ b/include/drm/gpu_scheduler.h
> > @@ -487,9 +487,10 @@ struct drm_sched_backend_ops {
> >   *                 finished.
> >   * @hw_rq_count: the number of jobs currently in the hardware queue.
> >   * @job_id_count: used to assign unique id to the each job.
> > - * @submit_wq: workqueue used to queue @work_submit
> > + * @submit_wq: workqueue used to queue @work_run_job and @work_free_job
> >   * @timeout_wq: workqueue used to queue @work_tdr
> > - * @work_submit: schedules jobs and cleans up entities
> > + * @work_run_job: schedules jobs
> > + * @work_free_job: cleans up jobs
> >   * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the
> >   *            timeout interval is over.
> >   * @pending_list: the list of jobs which are currently in the job queue.
> > @@ -518,7 +519,8 @@ struct drm_gpu_scheduler {
> >  	atomic64_t			job_id_count;
> >  	struct workqueue_struct		*submit_wq;
> >  	struct workqueue_struct		*timeout_wq;
> > -	struct work_struct		work_submit;
> > +	struct work_struct		work_run_job;
> > +	struct work_struct		work_free_job;
> >  	struct delayed_work		work_tdr;
> >  	struct list_head		pending_list;
> >  	spinlock_t			job_list_lock;
>