linux-kernel - [PATCH] cfq-iosched: non-rot devices do not need queue merging

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Date:	Wed, 30 Dec 2009 13:10:04 +0100
From:	Corrado Zoccolo <czoccolo@...il.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	Linux-Kernel <linux-kernel@...r.kernel.org>,
	Jeff Moyer <jmoyer@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Shaohua Li <shaohua.li@...el.com>,
	Gui Jianfeng <guijianfeng@...fujitsu.com>,
	Corrado Zoccolo <czoccolo@...il.com>
Subject: [PATCH] cfq-iosched: non-rot devices do not need queue merging

Non rotational devices' performances are not affected by
distance of requests, so there is no point in having overhead
to merge queues of nearby requests.

Signed-off-by: Corrado Zoccolo <czoccolo@...il.com>
---
 block/cfq-iosched.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 918c7fd..01bb0f3 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1268,7 +1268,8 @@ static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 		return;
 	if (!cfqq->next_rq)
 		return;
-
+	if (blk_queue_nonrot(cfqd->queue))
+		return;
 	cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
 	__cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
 				      blk_rq_pos(cfqq->next_rq), &parent, &p);
@@ -1689,7 +1690,7 @@ static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
 	struct cfq_queue *__cfqq;
 	sector_t sector = cfqd->last_position;
 
-	if (RB_EMPTY_ROOT(root))
+	if (RB_EMPTY_ROOT(root) || blk_queue_nonrot(cfqd->queue))
 		return NULL;
 
 	/*
-- 
1.6.4.4

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