[RFC][PATCH 3/7] rbtree, sched/deadline: Use rb_add_cached()

[Peter Zijlstra]

Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
 kernel/sched/deadline.c |   75 +++++++++++++++---------------------------------
 1 file changed, 24 insertions(+), 51 deletions(-)

--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -440,58 +440,38 @@ static void dec_dl_migration(struct sche
        update_dl_migration(dl_rq);
 }
 
+#define __node_2_pdl(node) \
+       rb_entry((node), struct task_struct, pushable_dl_tasks)
+
+static inline bool __pushable_less(struct rb_node *a, const struct rb_node *b)
+{
+       return dl_entity_preempt(&__node_2_pdl(a)->dl, &__node_2_pdl(b)->dl);
+}
+
 /*
  * The list of pushable -deadline task is not a plist, like in
  * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
  */
 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_root.rb_node;
-       struct rb_node *parent = NULL;
-       struct task_struct *entry;
-       bool leftmost = true;
-
        BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
 
-       while (*link) {
-               parent = *link;
-               entry = rb_entry(parent, struct task_struct,
-                                pushable_dl_tasks);
-               if (dl_entity_preempt(&p->dl, &entry->dl))
-                       link = &parent->rb_left;
-               else {
-                       link = &parent->rb_right;
-                       leftmost = false;
-               }
-       }
-
-       if (leftmost)
-               dl_rq->earliest_dl.next = p->dl.deadline;
-
-       rb_link_node(&p->pushable_dl_tasks, parent, link);
-       rb_insert_color_cached(&p->pushable_dl_tasks,
-                              &dl_rq->pushable_dl_tasks_root, leftmost);
+       if (rb_add_cached(&rq->dl.pushable_dl_tasks_root, &p->pushable_dl_tasks,
+                         __pushable_less))
+               rq->dl.earliest_dl.next = p->dl.deadline;
 }
 
 static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
 {
        struct dl_rq *dl_rq = &rq->dl;
+       struct rb_root_cached *root = &dl_rq->pushable_dl_tasks_root;
 
        if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
                return;
 
-       if (dl_rq->pushable_dl_tasks_root.rb_leftmost == &p->pushable_dl_tasks) 
{
-               struct rb_node *next_node;
+       if (rb_erase_cached(&p->pushable_dl_tasks, root))
+               dl_rq->earliest_dl.next = 
__node_2_pdl(rb_first_cached(root))->dl.deadline;
 
-               next_node = rb_next(&p->pushable_dl_tasks);
-               if (next_node) {
-                       dl_rq->earliest_dl.next = rb_entry(next_node,
-                               struct task_struct, 
pushable_dl_tasks)->dl.deadline;
-               }
-       }
-
-       rb_erase_cached(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
        RB_CLEAR_NODE(&p->pushable_dl_tasks);
 }
 
@@ -1401,29 +1381,21 @@ void dec_dl_tasks(struct sched_dl_entity
        dec_dl_migration(dl_se, dl_rq);
 }
 
+#define __node_2_dle(node) \
+       rb_entry((node), struct sched_dl_entity, rb_node)
+
+static inline bool __dl_less(struct rb_node *a, const struct rb_node *b)
+{
+       return dl_time_before(__node_2_dle(a)->deadline, 
__node_2_dle(b)->deadline);
+}
+
 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->root.rb_root.rb_node;
-       struct rb_node *parent = NULL;
-       struct sched_dl_entity *entry;
-       int leftmost = 1;
 
        BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
 
-       while (*link) {
-               parent = *link;
-               entry = rb_entry(parent, struct sched_dl_entity, rb_node);
-               if (dl_time_before(dl_se->deadline, entry->deadline))
-                       link = &parent->rb_left;
-               else {
-                       link = &parent->rb_right;
-                       leftmost = 0;
-               }
-       }
-
-       rb_link_node(&dl_se->rb_node, parent, link);
-       rb_insert_color_cached(&dl_se->rb_node, &dl_rq->root, leftmost);
+       rb_add_cached(&dl_rq->root, &dl_se->rb_node, __dl_less);
 
        inc_dl_tasks(dl_se, dl_rq);
 }
@@ -1436,6 +1408,7 @@ static void __dequeue_dl_entity(struct s
                return;
 
        rb_erase_cached(&dl_se->rb_node, &dl_rq->root);
+
        RB_CLEAR_NODE(&dl_se->rb_node);
 
        dec_dl_tasks(dl_se, dl_rq);