Re: [PATCH 4/8] drm/sched: Optimise drm_sched_entity_push_job

[Christian König]

Am 13.09.24 um 18:05 schrieb Tvrtko Ursulin:

From: Tvrtko Ursulin <tvrtko.ursu...@igalia.com>

In FIFO mode We can avoid dropping the lock only to immediately re-acquire
by adding a new drm_sched_rq_update_fifo_locked() helper.

v2:
  * Remove drm_sched_rq_update_fifo() altogether. (Christian)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@igalia.com>
Cc: Christian König <christian.koe...@amd.com>
Cc: Alex Deucher <alexander.deuc...@amd.com>
Cc: Luben Tuikov <ltuiko...@gmail.com>
Cc: Matthew Brost <matthew.br...@intel.com>
Cc: Philipp Stanner <pstan...@redhat.com>

Reviewed-by: Christian König <christian.koe...@amd.com>

---
  drivers/gpu/drm/scheduler/sched_entity.c | 13 +++++++++----
  drivers/gpu/drm/scheduler/sched_main.c   |  6 +++---
  include/drm/gpu_scheduler.h              |  2 +-
  3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c 
b/drivers/gpu/drm/scheduler/sched_entity.c
index 6645a8524699..aff79055643f 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -514,8 +514,12 @@ struct drm_sched_job *drm_sched_entity_pop_job(struct 
drm_sched_entity *entity)
                struct drm_sched_job *next;

next = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));

-               if (next)
-                       drm_sched_rq_update_fifo(entity, next->submit_ts);
+               if (next) {
+                       spin_lock(&entity->rq_lock);
+                       drm_sched_rq_update_fifo_locked(entity,
+                                                       next->submit_ts);
+                       spin_unlock(&entity->rq_lock);
+               }
        }

/* Jobs and entities might have different lifecycles. Since we're

@@ -615,10 +619,11 @@ void drm_sched_entity_push_job(struct drm_sched_job 
*sched_job)

atomic_inc(sched->score);

                drm_sched_rq_add_entity(rq, entity);
-               spin_unlock(&entity->rq_lock);

if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)

-                       drm_sched_rq_update_fifo(entity, submit_ts);
+                       drm_sched_rq_update_fifo_locked(entity, submit_ts);
+
+               spin_unlock(&entity->rq_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 f093616fe53c..d0ee0ba75a86 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -163,14 +163,15 @@ static inline void drm_sched_rq_remove_fifo_locked(struct 
drm_sched_entity *enti
        }
  }

-void drm_sched_rq_update_fifo(struct drm_sched_entity *entity, ktime_t ts)

+void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, ktime_t 
ts)
  {
        /*
         * Both locks need to be grabbed, one to protect from entity->rq change
         * for entity from within concurrent drm_sched_entity_select_rq and the
         * other to update the rb tree structure.
         */
-       spin_lock(&entity->rq_lock);
+       lockdep_assert_held(&entity->rq_lock);
+
        spin_lock(&entity->rq->lock);

drm_sched_rq_remove_fifo_locked(entity);

@@ -181,7 +182,6 @@ void drm_sched_rq_update_fifo(struct drm_sched_entity 
*entity, ktime_t ts)
                      drm_sched_entity_compare_before);

spin_unlock(&entity->rq->lock);

-       spin_unlock(&entity->rq_lock);
  }

/**

diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index a8d19b10f9b8..38465b78c7d5 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -593,7 +593,7 @@ 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(struct drm_sched_entity *entity, ktime_t ts);

+void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, ktime_t 
ts);

int drm_sched_entity_init(struct drm_sched_entity *entity,

                          enum drm_sched_priority priority,