cfq-iosched: sort RT queues into the rbtree

Currently CFQ does a linked insert into the current list for RT
queues. We can just factor the class into the rb insertion,
and then we don't have to treat RT queues in a special way. It's
faster, too.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 12 insertions, 15 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 55c476baa692..81c057eadfcc 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -471,7 +471,16 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
                 parent = *p;
                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
 
-                if (rb_key < __cfqq->rb_key)
+                /*
+                 * sort RT queues first, we always want to give
+                 * preference to them. after that, sort on the next
+                 * service time.
+                 */
+                if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
+                        p = &(*p)->rb_left;
+                else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
+                        p = &(*p)->rb_right;
+                else if (rb_key < __cfqq->rb_key)
                         p = &(*p)->rb_left;
                 else {
                         p = &(*p)->rb_right;
@@ -490,7 +499,6 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
 {
         struct cfq_data *cfqd = cfqq->cfqd;
-        struct list_head *n;
 
         /*
          * Resorting requires the cfqq to be on the RR list already.
@@ -500,25 +508,14 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
 
         list_del_init(&cfqq->cfq_list);
 
-        if (cfq_class_rt(cfqq)) {
-                /*
-                 * At to the front of the current list, but behind other
-                 * RT queues.
-                 */
-                n = &cfqd->cur_rr;
-                while (n->next != &cfqd->cur_rr)
-                        if (!cfq_class_rt(cfqq))
-                                break;
-
-                list_add(&cfqq->cfq_list, n);
-        } else if (cfq_class_idle(cfqq)) {
+        if (cfq_class_idle(cfqq)) {
                 /*
                  * IDLE goes to the tail of the idle list
                  */
                 list_add_tail(&cfqq->cfq_list, &cfqd->idle_rr);
         } else {
                 /*
-                 * So we get here, ergo the queue is a regular best-effort queue
+                 * RT and BE queues, sort into the rbtree
                  */
                 cfq_service_tree_add(cfqd, cfqq);
         }