[PATCH] drm/scheduler: improve job distribution with multiple queues

[Christian König]

Am 15.01.20 um 15:16 schrieb Nirmoy Das:
> This patch uses score based logic to select a new rq for better
> loadbalance between multiple rq/scheds instead of num_jobs.
>
> Below are test results after running amdgpu_test from mesa drm
>
> Before this patch:
>
> sched_name     num of many times it got scheduled
> =========      ==================================
> sdma0          314
> sdma1          32
> comp_1.0.0     56
> comp_1.0.1     0
> comp_1.1.0     0
> comp_1.1.1     0
> comp_1.2.0     0
> comp_1.2.1     0
> comp_1.3.0     0
> comp_1.3.1     0
> After this patch:
>
> sched_name     num of many times it got scheduled
> =========      ==================================
> sdma0          218
> sdma1          211
> comp_1.0.0     39
> comp_1.0.1     9
> comp_1.1.0     12
> comp_1.1.1     0
> comp_1.2.0     12
> comp_1.2.1     0
> comp_1.3.0     12
> comp_1.3.1     0
>
> Signed-off-by: Nirmoy Das <nirmoy.das at amd.com>
> ---
>   drivers/gpu/drm/scheduler/sched_entity.c | 9 ++++-----
>   drivers/gpu/drm/scheduler/sched_main.c   | 5 +++--
>   include/drm/gpu_scheduler.h              | 6 +++---
>   3 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> index 2e3a058fc239..7120eeec1a9b 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -130,7 +130,7 @@ static struct drm_sched_rq *
>   drm_sched_entity_get_free_sched(struct drm_sched_entity *entity)
>   {
>   	struct drm_sched_rq *rq = NULL;
> -	unsigned int min_jobs = UINT_MAX, num_jobs;
> +	unsigned int min_score = UINT_MAX, num_score;
>   	int i;
>   
>   	for (i = 0; i < entity->num_sched_list; ++i) {
> @@ -141,9 +141,9 @@ drm_sched_entity_get_free_sched(struct drm_sched_entity *entity)
>   			continue;
>   		}
>   
> -		num_jobs = atomic_read(&sched->num_jobs);
> -		if (num_jobs < min_jobs) {
> -			min_jobs = num_jobs;
> +		num_score = atomic_read(&sched->score);
> +		if (num_score < min_score) {
> +			min_score = num_score;
>   			rq = &entity->sched_list[i]->sched_rq[entity->priority];
>   		}
>   	}
> @@ -498,7 +498,6 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job,
>   	bool first;
>   
>   	trace_drm_sched_job(sched_job, entity);
> -	atomic_inc(&entity->rq->sched->num_jobs);
>   	WRITE_ONCE(entity->last_user, current->group_leader);
>   	first = spsc_queue_push(&entity->job_queue, &sched_job->queue_node);
>   
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 3fad5876a13f..f58a0e04ef2b 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -92,6 +92,7 @@ void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
>   	if (!list_empty(&entity->list))
>   		return;
>   	spin_lock(&rq->lock);
> +	atomic_inc(&rq->sched->score);
>   	list_add_tail(&entity->list, &rq->entities);
>   	spin_unlock(&rq->lock);
>   }
> @@ -110,6 +111,7 @@ void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
>   	if (list_empty(&entity->list))
>   		return;
>   	spin_lock(&rq->lock);
> +	atomic_dec(&rq->sched->score);
>   	list_del_init(&entity->list);
>   	if (rq->current_entity == entity)
>   		rq->current_entity = NULL;
> @@ -655,7 +657,6 @@ static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb)
>   	struct drm_gpu_scheduler *sched = s_fence->sched;
>   
>   	atomic_dec(&sched->hw_rq_count);
> -	atomic_dec(&sched->num_jobs);

Please keep incrementing/decrementing the score when jobs are 
added/completed.

In other words we should have +1 score for each entity and +1 score for 
each job in the scheduler.

Apart form that looks good to me now.

Thanks,
Christian.

>   
>   	trace_drm_sched_process_job(s_fence);
>   
> @@ -830,7 +831,7 @@ 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);
> -	atomic_set(&sched->num_jobs, 0);
> +	atomic_set(&sched->score, 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 96a1a1b7526e..eda58b22cf76 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -261,7 +261,7 @@ 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
> + * @score: score to help loadbalancer pick a most idle sched
>    * @ready: marks if the underlying HW is ready to work
>    * @free_guilty: A hit to time out handler to free the guilty job.
>    *
> @@ -282,8 +282,8 @@ struct drm_gpu_scheduler {
>   	struct list_head		ring_mirror_list;
>   	spinlock_t			job_list_lock;
>   	int				hang_limit;
> -	atomic_t                        num_jobs;
> -	bool			ready;
> +	atomic_t                        score;
> +	bool				ready;
>   	bool				free_guilty;
>   };
>