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deadline-iosched: allow non-sequential batching 

Deadline currently only batches sector-contiguous requests, so except
for a few circumstances (e.g. requests in a single direction), it is
essentially first come first served.  This is bad for throughput, so
change it to CSCAN, which means requests in a batch do not need to be
sequential and are issued in increasing sector order.

Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Aaron Carroll 2008-08-14 18:17:13 +10:00 committed by Jens Axboe
parent 766ca4428d
commit 63de428b13
1 changed files with 3 additions and 11 deletions
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14
block/deadline-iosched.c
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@ -258,17 +258,9 @@ static int deadline_dispatch_requests(struct request_queue *q, int force)
else
rq = dd->next_rq[READ];
if (rq) {
/* we have a "next request" */
if (dd->last_sector != rq->sector)
/* end the batch on a non sequential request */
dd->batching += dd->fifo_batch;
if (dd->batching < dd->fifo_batch)
/* we are still entitled to batch */
goto dispatch_request;
}
if (rq && dd->batching < dd->fifo_batch)
/* we have a next request are still entitled to batch */
goto dispatch_request;
/*
* at this point we are not running a batch. select the appropriate