drm/sched: Remove FIFO and RR and simplify to a single run queue

Since the new FAIR policy is in general better than FIFO and almost as
good as round-robin in interactive use cases, plus the latter has not been
the default policy in a long time, we can afford to remove both and leave
just FAIR.

By doing so we can simplify the scheduler code by making the scheduler to
run queue relationship always 1:1 and remove some code.

Also, now that the FIFO policy is gone the tree of entities is not a FIFO
tree any more so rename it to just the tree.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <phasta@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Tested-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20260417103744.76020-14-tvrtko.ursulin@igalia.com

1 files changed, 4 insertions, 32 deletions

diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 790f7ecb6b85..80e5ae2d61ec 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -100,8 +100,7 @@ struct drm_sched_entity {
 	 * @lock:
 	 *
 	 * Lock protecting the run-queue (@rq) to which this entity belongs,
-	 * @priority, the list of schedulers (@sched_list, @num_sched_list) and
-	 * the @rr_ts field.
+	 * @priority and the list of schedulers (@sched_list, @num_sched_list).
 	 */
 	spinlock_t			lock;
 
@@ -155,18 +154,6 @@ struct drm_sched_entity {
 	enum drm_sched_priority         priority;
 
 	/**
-	 * @rq_priority: Run-queue priority
-	 */
-	enum drm_sched_priority         rq_priority;
-
-	/**
-	 * @rr_ts:
-	 *
-	 * Fake timestamp of the last popped job from the entity.
-	 */
-	ktime_t				rr_ts;
-
-	/**
 	 * @job_queue: the list of jobs of this entity.
 	 */
 	struct spsc_queue		job_queue;
@@ -263,8 +250,7 @@ struct drm_sched_entity {
  * struct drm_sched_rq - queue of entities to be scheduled.
  *
  * @sched: the scheduler to which this rq belongs to.
- * @lock: protects @entities, @rb_tree_root, @rr_ts and @head_prio.
- * @rr_ts: monotonically incrementing fake timestamp for RR mode.
+ * @lock: protects @entities, @rb_tree_root and @head_prio.
  * @entities: list of the entities to be scheduled.
  * @rb_tree_root: root of time based priority queue of entities for FIFO scheduling
  * @head_prio: priority of the top tree element.
@@ -278,7 +264,6 @@ struct drm_sched_rq {
 
 	spinlock_t			lock;
 	/* Following members are protected by the @lock: */
-	ktime_t				rr_ts;
 	struct list_head		entities;
 	struct rb_root_cached		rb_tree_root;
 	enum drm_sched_priority		head_prio;
@@ -365,13 +350,6 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
  */
 struct drm_sched_job {
 	/**
-	 * @submit_ts:
-	 *
-	 * When the job was pushed into the entity queue.
-	 */
-	ktime_t                         submit_ts;
-
-	/**
 	 * @sched:
 	 *
 	 * The scheduler this job is or will be scheduled on. Gets set by
@@ -574,11 +552,7 @@ struct drm_sched_backend_ops {
  * @credit_count: the current credit count of this scheduler
  * @timeout: the time after which a job is removed from the scheduler.
  * @name: name of the ring for which this scheduler is being used.
- * @num_user_rqs: Number of run-queues. This is at most
- *                DRM_SCHED_PRIORITY_COUNT, as there's usually one run-queue per
- *                priority, but could be less.
- * @num_rqs: Equal to @num_user_rqs for FIFO and RR and 1 for the FAIR policy.
- * @sched_rq: An allocated array of run-queues of size @num_rqs;
+ * @rq: Scheduler run queue.
  * @job_scheduled: once drm_sched_entity_flush() is called the scheduler
  *                 waits on this wait queue until all the scheduled jobs are
  *                 finished.
@@ -610,9 +584,7 @@ struct drm_gpu_scheduler {
 	atomic_t			credit_count;
 	long				timeout;
 	const char			*name;
-	u32                             num_rqs;
-	u32                             num_user_rqs;
-	struct drm_sched_rq             **sched_rq;
+	struct drm_sched_rq             *rq;
 	wait_queue_head_t		job_scheduled;
 	atomic64_t			job_id_count;
 	struct workqueue_struct		*submit_wq;