linux-kernel - [PATCH] cfq-iosched: replace sync_flight by rq_in_driver[BLK_RW

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Message-Id: <1262185738-11942-1-git-send-email-czoccolo@gmail.com>
Date:	Wed, 30 Dec 2009 16:08:58 +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: replace sync_flight by rq_in_driver[BLK_RW_SYNC]

According to my intuition (and brief testing), sync_flight is always
equal to rq_in_driver[BLK_RW_SYNC] at the point of usage, so it can
be removed and replaced by the other.

Signed-off-by: Corrado Zoccolo <czoccolo@...il.com>
---
 block/cfq-iosched.c |    8 +-------
 1 files changed, 1 insertions(+), 7 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 01bb0f3..4865e08 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -228,7 +228,6 @@ struct cfq_data {
 	unsigned int busy_queues;
 
 	int rq_in_driver[2];
-	int sync_flight;
 
 	/*
 	 * queue-depth detection
@@ -1875,8 +1874,6 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
 	cfqq->dispatched++;
 	elv_dispatch_sort(q, rq);
 
-	if (cfq_cfqq_sync(cfqq))
-		cfqd->sync_flight++;
 	cfqq->nr_sectors += blk_rq_sectors(rq);
 }
 
@@ -2229,7 +2226,7 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	/*
 	 * If this is an async queue and we have sync IO in flight, let it wait
 	 */
-	if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
+	if (cfqd->rq_in_driver[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
 		return false;
 
 	max_dispatch = cfqd->cfq_quantum;
@@ -3294,9 +3291,6 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
 	cfqd->rq_in_driver[sync]--;
 	cfqq->dispatched--;
 
-	if (cfq_cfqq_sync(cfqq))
-		cfqd->sync_flight--;
-
 	if (sync) {
 		RQ_CIC(rq)->last_end_request = now;
 		if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
-- 
1.6.4.4

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