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Commit 1a1238a7 authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
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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: default avatarShaohua Li <shaohua.li@intel.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent e6c5bc73

block/cfq-iosched.c

+12 −0
Original line number Diff line number Diff line
@@ -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;