cfq-iosched: use the default seek distance when there aren't enough seek samples
Jeff Moyer [Tue, 21 Apr 2009 05:31:56 +0000 (07:31 +0200)]
If the cfq io context doesn't have enough samples yet to provide a mean
seek distance, then use the default threshold we have for seeky IO instead
of defaulting to 0.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/cfq-iosched.c

index 0eb4aff..7e13f04 100644 (file)
@@ -947,14 +947,18 @@ static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
                return cfqd->last_position - rq->sector;
 }
 
+#define CIC_SEEK_THR   8 * 1024
+#define CIC_SEEKY(cic) ((cic)->seek_mean > CIC_SEEK_THR)
+
 static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
 {
        struct cfq_io_context *cic = cfqd->active_cic;
+       sector_t sdist = cic->seek_mean;
 
        if (!sample_valid(cic->seek_samples))
-               return 0;
+               sdist = CIC_SEEK_THR;
 
-       return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
+       return cfq_dist_from_last(cfqd, rq) <= sdist;
 }
 
 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
@@ -1039,9 +1043,6 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
        return cfqq;
 }
 
-
-#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
-
 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 {
        struct cfq_queue *cfqq = cfqd->active_queue;