cfq: Make use of service count to estimate the rb_key offset

For the moment, different workload cfq queues are put into different
service trees. But CFQ still uses "busy_queues" to estimate rb_key
offset when inserting a cfq queue into a service tree. I think this
isn't appropriate, and it should make use of service tree count to do
this estimation. This patch is for for-2.6.33 branch.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 1bcbd8c79896..467981e19d7a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -600,11 +600,15 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
                                       struct cfq_queue *cfqq)
 {
+        struct cfq_rb_root *service_tree;
+
+        service_tree = service_tree_for(cfqq_prio(cfqq), cfqq_type(cfqq), cfqd);
+
         /*
          * just an approximation, should be ok.
          */
-        return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
-                       cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
+        return  service_tree->count * (cfq_prio_slice(cfqd, 1, 0) -
+                   cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
 }
 
 /*