Messages in this thread Patch in this message | | | From | Jeff Moyer <> | Subject | Re: [PATCH]cfq-iosched: don't take requests with long distence as close | Date | Thu, 07 Jan 2010 09:30:21 -0500 |
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Corrado Zoccolo <czoccolo@gmail.com> writes:
> On Tue, Jan 5, 2010 at 10:16 PM, Jeff Moyer <jmoyer@redhat.com> wrote: >> >> For now, I'm leaning towards asking Jens to revert this. It may still >> be worth making sure that we don't merge a seeky queue with a non-seeky >> queue. I have a patch for that if folks are interested. > Jeff, can you send this patch to Yanmin, that is investigating a > regression apparently caused by excessive queue merge? > > http://lkml.org/lkml/2010/1/4/194
You first have to back out Shaohua's patch, then apply this one.
Cheers, Jeff
cfq-iosched: don't allow merging with seeky queues
Shaohua Li noticed that cfq currently can merge with seeky queues, which causes unwanted merge/unmerge activity. We already know that the cur_cfqq is not seeky, so this patch just makes sure that the non-seeky queue is not merged with a seeky one.
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 8df4fe5..3db9050 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1677,6 +1677,10 @@ static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq, return cfq_dist_from_last(cfqd, rq) <= sdist; } +/* + * Search for a cfqq that is issuing non-seeky I/Os within the seek + * mean of the current cfqq. + */ static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, struct cfq_queue *cur_cfqq) { @@ -1701,7 +1705,14 @@ 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 the cfqq does not have enough seek samples, assume it is + * sequential until proven otherwise. If it is assumed that the + * queue is seeky first, then the close cooperator detection logic + * may never trigger as one queue strays further from the other(s). + */ + if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq) && + (!sample_valid(__cfqq->seek_samples) || !CFQQ_SEEKY(__cfqq))) return __cfqq; if (blk_rq_pos(__cfqq->next_rq) < sector) @@ -1712,7 +1723,8 @@ 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) && + (!sample_valid(__cfqq->seek_samples) || !CFQQ_SEEKY(__cfqq))) return __cfqq; return NULL; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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