cfq-iosched: make seek_mean converge more quickly
Jeff Moyer [Tue, 21 Apr 2009 05:25:04 +0000 (07:25 +0200)]
Right now, depending on the first sector to which a process issues I/O,
the seek time may start out way out of whack. So make sure we start
with 0 sectors in seek, instead of the offset of the first request
issued.

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

block/cfq-iosched.c

index 0d3b70d..0eb4aff 100644 (file)
@@ -1908,7 +1908,9 @@ cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
        sector_t sdist;
        u64 total;
 
-       if (cic->last_request_pos < rq->sector)
+       if (!cic->last_request_pos)
+               sdist = 0;
+       else if (cic->last_request_pos < rq->sector)
                sdist = rq->sector - cic->last_request_pos;
        else
                sdist = cic->last_request_pos - rq->sector;