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authorShaohua Li <shaohua.li@intel.com>2009-10-27 08:46:23 +0100
committerJens Axboe <jens.axboe@oracle.com>2009-10-27 08:46:23 +0100
commit1a1238a7dd48e48b3bba8f426a1d61c22c80d6d1 (patch)
tree08a39610689b5da8e8d61701864b8eb257acd6d7
parente6c5bc737ab71e4af6025ef7d150f5a26ae5f146 (diff)
downloadop-kernel-dev-1a1238a7dd48e48b3bba8f426a1d61c22c80d6d1.zip
op-kernel-dev-1a1238a7dd48e48b3bba8f426a1d61c22c80d6d1.tar.gz
cfq-iosched: improve hw_tag detection
If active queue hasn't enough requests and idle window opens, cfq will not dispatch sufficient requests to hardware. In such situation, current code will zero hw_tag. But this is because cfq doesn't dispatch enough requests instead of hardware queue doesn't work. Don't zero hw_tag in such case. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
-rw-r--r--block/cfq-iosched.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 47d6aac..418da9a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2257,6 +2257,8 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
*/
static void cfq_update_hw_tag(struct cfq_data *cfqd)
{
+ struct cfq_queue *cfqq = cfqd->active_queue;
+
if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak)
cfqd->rq_in_driver_peak = rq_in_driver(cfqd);
@@ -2264,6 +2266,16 @@ static void cfq_update_hw_tag(struct cfq_data *cfqd)
rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
return;
+ /*
+ * If active queue hasn't enough requests and can idle, cfq might not
+ * dispatch sufficient requests to hardware. Don't zero hw_tag in this
+ * case
+ */
+ if (cfqq && cfq_cfqq_idle_window(cfqq) &&
+ cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
+ CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
+ return;
+
if (cfqd->hw_tag_samples++ < 50)
return;
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