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

[Gui Jianfeng]

Hi Jens, Czoccolo

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@xxxxxxxxxxxxxx>
---
 block/cfq-iosched.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 1bcbd8c..467981e 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));
 }
 
 /*
-- 
1.5.4.rc3

-- 
Regards
Gui Jianfeng

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