Re: [PATCH v2] drm/sched: Further optimise drm_sched_entity_push_job

Christian König <ckoenig.leichtzumerken@xxxxxxxxx> · Tue, 24 Sep 2024 10:20:24 +0200

Am 16.09.24 um 19:30 schrieb Tvrtko Ursulin:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>

Having removed one re-lock cycle on the entity->lock in a patch titled
"drm/sched: Optimise drm_sched_entity_push_job", with only a tiny bit
larger refactoring we can do the same optimisation on the rq->lock.
(Currently both drm_sched_rq_add_entity() and
drm_sched_rq_update_fifo_locked() take and release the same lock.)

To achieve this we make drm_sched_rq_update_fifo_locked() and
drm_sched_rq_add_entity() expect the rq->lock to be held.

We also align drm_sched_rq_update_fifo_locked(),
drm_sched_rq_add_entity() and
drm_sched_rq_remove_fifo_locked() function signatures, by adding rq as a
parameter to the latter.

v2:
  * Fix after rebase of the series.
  * Avoid naming incosistency between drm_sched_rq_add/remove. (Christian)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Luben Tuikov <ltuikov89@xxxxxxxxx>
Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
Cc: Philipp Stanner <pstanner@xxxxxxxxxx>

Reviewed-by: Christian König <christian.koenig@xxxxxxx>

---
  drivers/gpu/drm/scheduler/sched_entity.c | 12 ++++++++--
  drivers/gpu/drm/scheduler/sched_main.c   | 29 ++++++++++++------------
  include/drm/gpu_scheduler.h              |  3 ++-
  3 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index d982cebc6bee..8ace1f1ea66b 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -515,9 +515,14 @@ struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
  
  		next = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));
  		if (next) {
+			struct drm_sched_rq *rq;
+
  			spin_lock(&entity->lock);
-			drm_sched_rq_update_fifo_locked(entity,
+			rq = entity->rq;
+			spin_lock(&rq->lock);
+			drm_sched_rq_update_fifo_locked(entity, rq,
  							next->submit_ts);
+			spin_unlock(&rq->lock);
  			spin_unlock(&entity->lock);
  		}
  	}
@@ -618,11 +623,14 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
  		sched = rq->sched;
  
  		atomic_inc(sched->score);
+
+		spin_lock(&rq->lock);
  		drm_sched_rq_add_entity(rq, entity);
  
  		if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
-			drm_sched_rq_update_fifo_locked(entity, submit_ts);
+			drm_sched_rq_update_fifo_locked(entity, rq, submit_ts);
  
+		spin_unlock(&rq->lock);
  		spin_unlock(&entity->lock);
  
  		drm_sched_wakeup(sched, entity);
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 18a952f73ecb..5c83fb92bb89 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -153,17 +153,18 @@ static __always_inline bool drm_sched_entity_compare_before(struct rb_node *a,
  	return ktime_before(ent_a->oldest_job_waiting, ent_b->oldest_job_waiting);
  }
  
-static inline void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *entity)
+static void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *entity,
+					    struct drm_sched_rq *rq)
  {
-	struct drm_sched_rq *rq = entity->rq;
-
  	if (!RB_EMPTY_NODE(&entity->rb_tree_node)) {
  		rb_erase_cached(&entity->rb_tree_node, &rq->rb_tree_root);
  		RB_CLEAR_NODE(&entity->rb_tree_node);
  	}
  }
  
-void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, ktime_t ts)
+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
@@ -171,17 +172,14 @@ void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, ktime_t ts
  	 * other to update the rb tree structure.
  	 */
  	lockdep_assert_held(&entity->lock);
+	lockdep_assert_held(&rq->lock);
  
-	spin_lock(&entity->rq->lock);
-
-	drm_sched_rq_remove_fifo_locked(entity);
+	drm_sched_rq_remove_fifo_locked(entity, rq);
  
  	entity->oldest_job_waiting = ts;
  
-	rb_add_cached(&entity->rb_tree_node, &entity->rq->rb_tree_root,
+	rb_add_cached(&entity->rb_tree_node, &rq->rb_tree_root,
  		      drm_sched_entity_compare_before);
-
-	spin_unlock(&entity->rq->lock);
  }
  
  /**
@@ -213,15 +211,14 @@ static void drm_sched_rq_init(struct drm_gpu_scheduler *sched,
  void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
  			     struct drm_sched_entity *entity)
  {
+	lockdep_assert_held(&entity->lock);
+	lockdep_assert_held(&rq->lock);
+
  	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);
  }
  
  /**
@@ -235,6 +232,8 @@ void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
  void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
  				struct drm_sched_entity *entity)
  {
+	lockdep_assert_held(&entity->lock);
+
  	if (list_empty(&entity->list))
  		return;
  
@@ -247,7 +246,7 @@ void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
  		rq->current_entity = NULL;
  
  	if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
-		drm_sched_rq_remove_fifo_locked(entity);
+		drm_sched_rq_remove_fifo_locked(entity, rq);
  
  	spin_unlock(&rq->lock);
  }
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 80198e6cf537..b21806d5a8eb 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -596,7 +596,8 @@ void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
  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, ktime_t ts);
+void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity,
+				     struct drm_sched_rq *rq, ktime_t ts);
  
  int drm_sched_entity_init(struct drm_sched_entity *entity,
  			  enum drm_sched_priority priority,







