Messages in this thread Patch in this message | | | Date | Mon, 28 Dec 2009 10:03:48 +0800 | From | Shaohua Li <> | Subject | [PATCH]cfq-iosched: don't take requests with long distence as close |
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On Fri, Dec 25, 2009 at 06:16:27PM +0800, Corrado Zoccolo wrote: > Hi Shaohua, > On Thu, Dec 24, 2009 at 1:55 AM, Shaohua Li <shaohua.li@intel.com> wrote: > > df5fe3e8e13883f58dc97489076bbcc150789a21 > > b3b6d0408c953524f979468562e7e210d8634150 > > The coop merge is too aggressive. For example, if two tasks are reading two > > files where the two files have some adjecent blocks, cfq will immediately > > merge them. cfq_rq_close() also has trouble, sometimes the seek_mean is very > > big. I did a test to make cfq_rq_close() always checks the distence according > > to CIC_SEEK_THR, but still saw a lot of wrong merge. (BTW, why we take a long > > distence far away request as close. Taking them close doesn't improve any thoughtput > > to me. Maybe we should always use CIC_SEEK_THR as close criteria). > Yes, when deciding if two queues are going to be merged, we should use > the constant CIC_SEEK_THR.
seek_mean could be very big sometimes, using it as close criteria is meanless as this doen't improve any performance. So if it's big, let's fallback to default value.
Signed-off-by: Shaohua Li<shaohua.li@intel.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index e2f8046..8025605 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1682,6 +1682,10 @@ static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq, if (!sample_valid(cfqq->seek_samples)) sdist = CFQQ_SEEK_THR; + /* if seek_mean is big, using it as close criteria is meanless */ + if (sdist > CFQQ_SEEK_THR) + sdist = CFQQ_SEEK_THR; + return cfq_dist_from_last(cfqd, rq) <= sdist; }
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