linux-kernel - [PATCH 1/3] deadline-iosched: allow non-sequential batching

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Message-Id: <1218701835-17327-2-git-send-email-aaronc@gelato.unsw.edu.au>
Date:	Thu, 14 Aug 2008 18:17:13 +1000
From:	Aaron Carroll <aaronc@...ato.unsw.edu.au>
To:	jens.axboe@...cle.com
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] 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@...ato.unsw.edu.au>
---
 block/deadline-iosched.c |   14 +++-----------
 1 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index 342448c..07b80e4 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -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
-- 
1.5.4.5

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