[PATCH 4/5] sched/deadline: Replace earliest deadline and runqueue leftmost caching

[Davidlohr Bueso]

... with the generic rbtree flavor instead. No changes
in semantics whatsoever.

Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
---
 kernel/sched/deadline.c | 50 +++++++++++++++++++------------------------------
 kernel/sched/sched.h    |  6 ++----
 2 files changed, 21 insertions(+), 35 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index df6c2912bd60..4e564276c634 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -47,7 +47,7 @@ static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
 {
 	struct sched_dl_entity *dl_se = &p->dl;
 
-	return dl_rq->rb_leftmost == &dl_se->rb_node;
+	return dl_rq->root.rb_leftmost == &dl_se->rb_node;
 }
 
 void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
@@ -71,7 +71,7 @@ void init_dl_bw(struct dl_bw *dl_b)
 
 void init_dl_rq(struct dl_rq *dl_rq)
 {
-	dl_rq->rb_root = RB_ROOT;
+	dl_rq->root = RB_ROOT_CACHED;
 
 #ifdef CONFIG_SMP
 	/* zero means no -deadline tasks */
@@ -79,7 +79,7 @@ void init_dl_rq(struct dl_rq *dl_rq)
 
 	dl_rq->dl_nr_migratory = 0;
 	dl_rq->overloaded = 0;
-	dl_rq->pushable_dl_tasks_root = RB_ROOT;
+	dl_rq->pushable_dl_tasks_root = RB_ROOT_CACHED;
 #else
 	init_dl_bw(&dl_rq->dl_bw);
 #endif
@@ -157,10 +157,10 @@ static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
 {
 	struct dl_rq *dl_rq = &rq->dl;
-	struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node;
+	struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_root.rb_node;
 	struct rb_node *parent = NULL;
 	struct task_struct *entry;
-	int leftmost = 1;
+	bool leftmost = true;
 
 	BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
 
@@ -172,17 +172,16 @@ static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
 			link = &parent->rb_left;
 		else {
 			link = &parent->rb_right;
-			leftmost = 0;
+			leftmost = false;
 		}
 	}
 
-	if (leftmost) {
-		dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;
+	if (leftmost)
 		dl_rq->earliest_dl.next = p->dl.deadline;
-	}
 
 	rb_link_node(&p->pushable_dl_tasks, parent, link);
-	rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
+	rb_insert_color_cached(&p->pushable_dl_tasks,
+			       &dl_rq->pushable_dl_tasks_root, leftmost);
 }
 
 static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
@@ -192,24 +191,23 @@ static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
 	if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
 		return;
 
-	if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
+	if (dl_rq->pushable_dl_tasks_root.rb_leftmost == &p->pushable_dl_tasks) {
 		struct rb_node *next_node;
 
 		next_node = rb_next(&p->pushable_dl_tasks);
-		dl_rq->pushable_dl_tasks_leftmost = next_node;
 		if (next_node) {
 			dl_rq->earliest_dl.next = rb_entry(next_node,
 				struct task_struct, pushable_dl_tasks)->dl.deadline;
 		}
 	}
 
-	rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
+	rb_erase_cached(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
 	RB_CLEAR_NODE(&p->pushable_dl_tasks);
 }
 
 static inline int has_pushable_dl_tasks(struct rq *rq)
 {
-	return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root);
+	return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root);
 }
 
 static int push_dl_task(struct rq *rq);
@@ -841,7 +839,7 @@ static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
 		dl_rq->earliest_dl.next = 0;
 		cpudl_clear(&rq->rd->cpudl, rq->cpu);
 	} else {
-		struct rb_node *leftmost = dl_rq->rb_leftmost;
+		struct rb_node *leftmost = dl_rq->root.rb_leftmost;
 		struct sched_dl_entity *entry;
 
 		entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
@@ -888,7 +886,7 @@ void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
 {
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
-	struct rb_node **link = &dl_rq->rb_root.rb_node;
+	struct rb_node **link = &dl_rq->root.rb_root.rb_node;
 	struct rb_node *parent = NULL;
 	struct sched_dl_entity *entry;
 	int leftmost = 1;
@@ -906,11 +904,8 @@ static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
 		}
 	}
 
-	if (leftmost)
-		dl_rq->rb_leftmost = &dl_se->rb_node;
-
 	rb_link_node(&dl_se->rb_node, parent, link);
-	rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);
+	rb_insert_color_cached(&dl_se->rb_node, &dl_rq->root, leftmost);
 
 	inc_dl_tasks(dl_se, dl_rq);
 }
@@ -922,14 +917,7 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
 	if (RB_EMPTY_NODE(&dl_se->rb_node))
 		return;
 
-	if (dl_rq->rb_leftmost == &dl_se->rb_node) {
-		struct rb_node *next_node;
-
-		next_node = rb_next(&dl_se->rb_node);
-		dl_rq->rb_leftmost = next_node;
-	}
-
-	rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
+	rb_erase_cached(&dl_se->rb_node, &dl_rq->root);
 	RB_CLEAR_NODE(&dl_se->rb_node);
 
 	dec_dl_tasks(dl_se, dl_rq);
@@ -1160,7 +1148,7 @@ static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
 static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
 						   struct dl_rq *dl_rq)
 {
-	struct rb_node *left = dl_rq->rb_leftmost;
+	struct rb_node *left = rb_first_cached(&dl_rq->root);
 
 	if (!left)
 		return NULL;
@@ -1297,7 +1285,7 @@ static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
  */
 static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
 {
-	struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
+	struct rb_node *next_node = rq->dl.pushable_dl_tasks_root.rb_leftmost;
 	struct task_struct *p = NULL;
 
 	if (!has_pushable_dl_tasks(rq))
@@ -1470,7 +1458,7 @@ static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
 	if (!has_pushable_dl_tasks(rq))
 		return NULL;
 
-	p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
+	p = rb_entry(rq->dl.pushable_dl_tasks_root.rb_leftmost,
 		     struct task_struct, pushable_dl_tasks);
 
 	BUG_ON(rq->cpu != task_cpu(p));
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 6fe986abfeee..49c311c10e16 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -527,8 +527,7 @@ struct rt_rq {
 /* Deadline class' related fields in a runqueue */
 struct dl_rq {
 	/* runqueue is an rbtree, ordered by deadline */
-	struct rb_root rb_root;
-	struct rb_node *rb_leftmost;
+	struct rb_root_cached root;
 
 	unsigned long dl_nr_running;
 
@@ -552,8 +551,7 @@ struct dl_rq {
 	 * an rb-tree, ordered by tasks' deadlines, with caching
 	 * of the leftmost (earliest deadline) element.
 	 */
-	struct rb_root pushable_dl_tasks_root;
-	struct rb_node *pushable_dl_tasks_leftmost;
+	struct rb_root_cached pushable_dl_tasks_root;
 #else
 	struct dl_bw dl_bw;
 #endif
-- 
2.12.0