From 1a1238a7dd48e48b3bba8f426a1d61c22c80d6d1 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Tue, 27 Oct 2009 08:46:23 +0100 Subject: 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 Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'block/cfq-iosched.c') diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 47d6aaca0c51..418da9a49bb0 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; -- cgit v1.2.3