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Subject[PATCH 6/15] cfq-iosched: sort RT queues into the rbtree
Date
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>
---
block/cfq-iosched.c | 27 ++++++++++++---------------
1 files changed, 12 insertions(+), 15 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 7f964ee..38ac492 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);
}
--
1.5.1.1.190.g74474
-
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