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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: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Shaohua Li<shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Shaohua Li 2009-12-28 13:18:44 +01:00 committed by Jens Axboe
parent 6ec1480d85
commit 2f7a2d89a8
1 changed files with 8 additions and 4 deletions
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12
block/cfq-iosched.c
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@ -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;