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Commit 2f7a2d89 authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
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cfq-iosched: don't regard requests with long distance as close 



seek_mean could be very big sometimes, using it as close criteria is meaningless
as this doen't improve any performance. So if it's big, let's fallback to
default value.

Reviewed-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarShaohua <Li&lt;shaohua.li@intel.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 6ec1480d

block/cfq-iosched.c

+8 −4
Original line number Diff line number Diff line
@@ -1667,13 +1667,17 @@ static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 
#define CFQQ_SEEKY(cfqq)	((cfqq)->seek_mean > CFQQ_SEEK_THR)



static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,

			       struct request *rq)

			       struct request *rq, bool for_preempt)

{

	sector_t sdist = cfqq->seek_mean;



	if (!sample_valid(cfqq->seek_samples))

		sdist = CFQQ_SEEK_THR;



	/* if seek_mean is big, using it as close criteria is meaningless */

	if (sdist > CFQQ_SEEK_THR && !for_preempt)

		sdist = CFQQ_SEEK_THR;



	return cfq_dist_from_last(cfqd, rq) <= sdist;

}
@@ -1701,7 +1705,7 @@ static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, 
	 * will contain the closest sector.

	 */

	__cfqq = rb_entry(parent, struct cfq_queue, p_node);

	if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))

	if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq, false))

		return __cfqq;



	if (blk_rq_pos(__cfqq->next_rq) < sector)
@@ -1712,7 +1716,7 @@ static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, 
		return NULL;



	__cfqq = rb_entry(node, struct cfq_queue, p_node);

	if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))

	if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq, false))

		return __cfqq;



	return NULL;
@@ -3112,7 +3116,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 
	 * if this request is as-good as one we would expect from the

	 * current cfqq, let it preempt

	 */

	if (cfq_rq_close(cfqd, cfqq, rq))

	if (cfq_rq_close(cfqd, cfqq, rq, true))

		return true;



	return false;