From 2f7a2d89a8b5915d89ad9ebeb0065db7d5831cea Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Mon, 28 Dec 2009 13:18:44 +0100 Subject: [PATCH] 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 Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 8df4fe5..918c7fd 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; -- 1.8.2.3