From: Jeff Moyer <jmoyer@redhat.com>
Date: Tue, 3 Nov 2009 11:36:38 -0500
Subject: [block] cfq-iosched: default seek when not enough samples
Message-id: 1257266206-24003-5-git-send-email-jmoyer@redhat.com
O-Subject: [PATCH 04/12] cfq-iosched: use the default seek distance when there aren't enough seek samples
Bugzilla: 456181 448130 427709
RH-Acked-by: Rik van Riel <riel@redhat.com>
RH-Acked-by: Josef Bacik <josef@redhat.com>
RH-Acked-by: Vivek Goyal <vgoyal@redhat.com>
RH-Acked-by: Jeff Layton <jlayton@redhat.com>

commit 04dc6e71a28d4815bf9431efcafc107bb0ad2792
Author: Jeff Moyer <jmoyer@redhat.com>
Date:   Tue Apr 21 07:31:56 2009 +0200

    cfq-iosched: use the default seek distance when there aren't enough seek sam

    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>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 78f4853..b20eba7 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -962,18 +962,20 @@ 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;
 }
 
-#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
-
 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
 					      struct cfq_queue *cfqq)
 {