cfq-iosched: tweak the FIFO checking

We currently check the FIFO once per slice. Optimize that a bit and
only do it as the first thing for a new slice, so we don't end up
doing a single request and then seek to the FIFO requests.

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

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3df41a0..03b1e47 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -885,16 +885,17 @@ static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
 
        if (cfq_cfqq_fifo_expire(cfqq))
                return NULL;
+
+       cfq_mark_cfqq_fifo_expire(cfqq);
+
        if (list_empty(&cfqq->fifo))
                return NULL;
 
        fifo = cfq_cfqq_class_sync(cfqq);
        rq = rq_entry_fifo(cfqq->fifo.next);
 
-       if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
-               cfq_mark_cfqq_fifo_expire(cfqq);
+       if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
                return rq;
-       }
 
        return NULL;
 }