Commit a6327162 authored Aug 24, 2011 by Shaohua Li Committed by Jens Axboe Aug 24, 2011

block: change force plug flush call order

Do blk_flush_plug_list() first and then add new request aDo blk_flush_plug_list() first and then add new request aDo blk_flush_plug_list() first and then add new request at the tail. New
request can't be merged to existing requests, but later new requests might
be merged with this new one. If blk_flush_plug_list() is done later, the
merge doesn't happen.
Believe it or not, this fixes a 10% regression running sysbench workload.

Signed-off-by: Shaohua Li <shli@kernel.org>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

parent e8037d49

block/blk-core.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -1302,11 +1302,11 @@ static int __make_request(struct request_queue q, struct bio bio)
		if (__rq->q != q)
		plug->should_sort = 1;
		}
		list_add_tail(&req->queuelist, &plug->list);
		plug->count++;
		drive_stat_acct(req, 1);
		if (plug->count >= BLK_MAX_REQUEST_COUNT)
		blk_flush_plug_list(plug, false);
		plug->count++;
		list_add_tail(&req->queuelist, &plug->list);
		drive_stat_acct(req, 1);
		} else {
		spin_lock_irq(q->queue_lock);
		add_acct_request(q, req, where);