Re: [PATCH 8/8] drm/sched: Further optimise drm_sched_entity_push_job

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On 16/09/2024 13:20, Tvrtko Ursulin wrote:

On 16/09/2024 13:11, Christian König wrote:
Am 13.09.24 um 18:05 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 rename drm_sched_rq_add_entity() to
drm_sched_rq_add_entity_locked(), making it expect the rq->lock to be
held, and also add the same expectation to
drm_sched_rq_update_fifo_locked().

Finally, to align drm_sched_rq_update_fifo_locked(),
drm_sched_rq_add_entity_locked() and
drm_sched_rq_remove_fifo_locked() function signatures, we add rq as a
parameter to the latter.

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>
---
  drivers/gpu/drm/scheduler/sched_entity.c |  8 ++++--
  drivers/gpu/drm/scheduler/sched_main.c   | 34 +++++++++++-------------
  include/drm/gpu_scheduler.h              |  7 ++---
  3 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index d982cebc6bee..c48f17faef41 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -517,6 +517,7 @@ struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
          if (next) {
              spin_lock(&entity->lock);
              drm_sched_rq_update_fifo_locked(entity,
+                            entity->rq,
                              next->submit_ts);
              spin_unlock(&entity->lock);
          }
@@ -618,11 +619,14 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
          sched = rq->sched;
          atomic_inc(sched->score);
-        drm_sched_rq_add_entity(rq, entity);
+
+        spin_lock(&rq->lock);
+        drm_sched_rq_add_entity_locked(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..c0d3f6ac3ae3 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);
  }
  /**
@@ -203,25 +201,23 @@ static void drm_sched_rq_init(struct drm_gpu_scheduler *sched,
  }
  /**
- * drm_sched_rq_add_entity - add an entity
+ * drm_sched_rq_add_entity_locked - add an entity
   *
   * @rq: scheduler run queue
   * @entity: scheduler entity
   *
   * Adds a scheduler entity to the run queue.
   */
-void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
-                 struct drm_sched_entity *entity)
+void drm_sched_rq_add_entity_locked(struct drm_sched_rq *rq,
+                    struct drm_sched_entity *entity)
  {
+    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 +231,8 @@ 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)

The naming of drm_sched_rq_add_entity_locked() and drm_sched_rq_add_entity_locked() don't match up any more.

I suggest to either remove the _locked postfix or always add it.

Oh well spotted.. I confused it with remove_fifo_locked when I told to myself everything is aligned. Will fix.

Sent v2.

I smoke tested this on the Steam Deck with lockdep enabled and it seems fine. But that does not feel enough. There is no automated CI on the AMD side to run this through?

Regards,

Tvrtko


Apart from that I'm not completely happy with the change, but it looks like it doesn't add any additional complexity.

Thanks, I agree! ;) Will have more passes once this series is done to find more things to polish.

Regards,

Tvrtko

  {
+    lockdep_assert_held(&entity->lock);
+
      if (list_empty(&entity->list))
          return;
@@ -247,7 +245,7 @@ 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..30686961a379 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -591,12 +591,13 @@ bool drm_sched_dependency_optimized(struct dma_fence* fence,
                      struct drm_sched_entity *entity);
  void drm_sched_fault(struct drm_gpu_scheduler *sched);
-void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
-                 struct drm_sched_entity *entity);
+void drm_sched_rq_add_entity_locked(struct drm_sched_rq *rq,
+                    struct drm_sched_entity *entity);
  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,




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