linux-kernel - [PATCH] Block SQ/MQ Request Priority

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Date:   Tue, 4 Apr 2017 08:25:14 -0700
From:   <adam.manzanares@....com>
To:     <axboe@...nel.dk>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <hch@...radead.org>, <Bart.VanAssche@...disk.com>,
        Adam Manzanares <adam.manzanares@....com>
Subject: [PATCH] Block SQ/MQ Request Priority

From: Adam Manzanares <adam.manzanares@....com>

In 4.10 I introduced a patch that associates the ioc priority with
each request in the block layer. This work was done in the single queue
block layer code. This patch unifies ioc priority to request mapping across
the single/multi queue block layers.

I have tested this patch with the null block device driver with the following
parameters.

null_blk queue_mode=2 irqmode=0 use_per_node_hctx=1 nr_devices=1

I have not seen a performance regression with this patch and I would appreciate
any feedback or additional testing.

I have also verified that io priorities are passed to the device when using
the SQ and MQ path to a SATA HDD that supports io priorities.

Thanks.

Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Adam Manzanares <adam.manzanares@....com>
---
 block/blk-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 43b7d06..316a539 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1149,7 +1149,6 @@ static struct request *__get_request(struct request_list *rl, unsigned int op,

 	blk_rq_init(q, rq);
 	blk_rq_set_rl(rq, rl);
-	blk_rq_set_prio(rq, ioc);
 	rq->cmd_flags = op;
 	rq->rq_flags = rq_flags;

@@ -1636,6 +1635,7 @@ void init_request_from_bio(struct request *req, struct bio *bio)

 	req->errors = 0;
 	req->__sector = bio->bi_iter.bi_sector;
+	blk_rq_set_prio(req, rq_ioc(bio));
 	if (ioprio_valid(bio_prio(bio)))
 		req->ioprio = bio_prio(bio);
 	blk_rq_bio_prep(req->q, req, bio);
-- 
2.7.4