path: root/block
diff options
authorShaohua Li <shaohua.li@intel.com>2009-12-28 13:18:44 +0100
committerJens Axboe <jens.axboe@oracle.com>2009-12-28 13:18:44 +0100
commit2f7a2d89a8b5915d89ad9ebeb0065db7d5831cea (patch)
tree776c4a7e47b07437c30411d7324b5a1c7de01696 /block
parent6ec1480d8539c8e2e6ba7fbbeffe5adc640bfe98 (diff)
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>
Diffstat (limited to 'block')
1 files changed, 8 insertions, 4 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 8df4fe58f4e..918c7fd9aeb 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -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;