linux-kernel - [PATCH 1/3] block: avoid unnecessary plug should

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Message-ID: <201208101945119533551@gmail.com>
Date:	Fri, 10 Aug 2012 19:45:14 +0800
From:	"Jianpeng Ma" <majianpeng@...il.com>
To:	axboe <axboe@...nel.dk>
Cc:	"Shaohua Li" <shli@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/3] block: avoid unnecessary plug should_sort test.

If request_count >= BLK_MAX_REQUEST_COUNT,then it will exec
blk_flush_plug_list which plug all request.So no need to do plug->should_sort test.

Signed-off-by: Jianpeng Ma <majianpeng@...il.com>
---
 block/blk-core.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 4b4dbdf..7a3abc6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1514,17 +1514,16 @@ get_rq:
 		if (list_empty(&plug->list))
 			trace_block_plug(q);
 		else {
-			if (!plug->should_sort) {
+			if (request_count >= BLK_MAX_REQUEST_COUNT) {
+				blk_flush_plug_list(plug, false);
+				trace_block_plug(q);
+			} else if (!plug->should_sort) {
 				struct request *__rq;
 
 				__rq = list_entry_rq(plug->list.prev);
 				if (__rq->q != q)
 					plug->should_sort = 1;
 			}
-			if (request_count >= BLK_MAX_REQUEST_COUNT) {
-				blk_flush_plug_list(plug, false);
-				trace_block_plug(q);
-			}
 		}
 		list_add_tail(&req->queuelist, &plug->list);
 		drive_stat_acct(req, 1);
-- 
1.7.9.5