linux-kernel - [RFC 08/21] drm/sched: Remove idle entity from tree

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Message-ID: <20250903152327.66002-9-tvrtko.ursulin@igalia.com>
Date: Wed,  3 Sep 2025 16:23:14 +0100
From: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
To: dri-devel@...ts.freedesktop.org
Cc: amd-gfx@...ts.freedesktop.org,
	kernel-dev@...lia.com,
	intel-xe@...ts.freedesktop.org,
	cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Tvrtko Ursulin <tvrtko.ursulin@...lia.com>,
	Christian König <christian.koenig@....com>,
	Danilo Krummrich <dakr@...nel.org>,
	Matthew Brost <matthew.brost@...el.com>,
	Philipp Stanner <phasta@...nel.org>
Subject: [RFC 08/21] drm/sched: Remove idle entity from tree

There is no need to keep entities with no jobs in the tree so lets remove
it once the last job is consumed. This keeps the tree smaller which is
nicer and more efficient as entities are removed and re-added on every
popped job.

Apart from that, the upcoming fair scheduling algorithm will rely on the
tree only containing runnable entities.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
Cc: Christian König <christian.koenig@....com>
Cc: Danilo Krummrich <dakr@...nel.org>
Cc: Matthew Brost <matthew.brost@...el.com>
Cc: Philipp Stanner <phasta@...nel.org>
---
 drivers/gpu/drm/scheduler/sched_rq.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_rq.c b/drivers/gpu/drm/scheduler/sched_rq.c
index 16d57461765e..67804815ca0d 100644
--- a/drivers/gpu/drm/scheduler/sched_rq.c
+++ b/drivers/gpu/drm/scheduler/sched_rq.c
@@ -19,6 +19,9 @@ drm_sched_entity_compare_before(struct rb_node *a, const struct rb_node *b)
 static void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *entity,
 					    struct drm_sched_rq *rq)
 {
+	lockdep_assert_held(&entity->lock);
+	lockdep_assert_held(&rq->lock);
+
 	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);
@@ -158,24 +161,27 @@ void drm_sched_rq_pop_entity(struct drm_sched_entity *entity)
 {
 	struct drm_sched_job *next_job;
 	struct drm_sched_rq *rq;
-	ktime_t ts;
 
 	/*
 	 * Update the entity's location in the min heap according to
 	 * the timestamp of the next job, if any.
 	 */
+	spin_lock(&entity->lock);
+	rq = entity->rq;
+	spin_lock(&rq->lock);
 	next_job = drm_sched_entity_queue_peek(entity);
-	if (!next_job)
-		return;
+	if (next_job) {
+		ktime_t ts;
 
-	spin_lock(&entity->lock);
-	rq = entity->rq;
-	spin_lock(&rq->lock);
-	if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
-		ts = next_job->submit_ts;
-	else
-		ts = drm_sched_rq_get_rr_ts(rq, entity);
-	drm_sched_rq_update_fifo_locked(entity, rq, ts);
+		if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
+			ts = next_job->submit_ts;
+		else
+			ts = drm_sched_rq_get_rr_ts(rq, entity);
+
+		drm_sched_rq_update_fifo_locked(entity, rq, ts);
+	} else {
+		drm_sched_rq_remove_fifo_locked(entity, rq);
+	}
 	spin_unlock(&rq->lock);
 	spin_unlock(&entity->lock);
 }
-- 
2.48.0