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block: change force plug flush call order

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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>
This commit is contained in:
Shaohua Li 2011-08-24 16:04:32 +02:00 committed by Jens Axboe
parent e8037d4983
commit a632716275
1 changed files with 3 additions and 3 deletions
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6
block/blk-core.c
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@ -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);