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From:   Li Feng <fengli@smartx.com>
To:     Jens Axboe <axboe@kernel.dk>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
        linux-block@vger.kernel.org (open list:BLOCK LAYER),
        linux-kernel@vger.kernel.org (open list),
        virtualization@lists.linux.dev (open list:VIRTIO BLOCK AND SCSI DRIVERS)
Cc:     Li Feng <fengli@smartx.com>
Subject: [PATCH] virtio_blk: set the default scheduler to none
Date:   Thu,  7 Dec 2023 12:31:05 +0800
Message-ID: <20231207043118.118158-1-fengli@smartx.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

virtio-blk is generally used in cloud computing scenarios, where the
performance of virtual disks is very important. The mq-deadline scheduler
has a big performance drop compared to none with single queue. In my tests,
mq-deadline 4k readread iops were 270k compared to 450k for none. So here
the default scheduler of virtio-blk is set to "none".

Signed-off-by: Li Feng <fengli@smartx.com>
---
 drivers/block/virtio_blk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index d53d6aa8ee69..5183ec8e00be 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -1367,7 +1367,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 	vblk->tag_set.ops = &virtio_mq_ops;
 	vblk->tag_set.queue_depth = queue_depth;
 	vblk->tag_set.numa_node = NUMA_NO_NODE;
-	vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+	vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_NO_SCHED_BY_DEFAULT;
 	vblk->tag_set.cmd_size =
 		sizeof(struct virtblk_req) +
 		sizeof(struct scatterlist) * VIRTIO_BLK_INLINE_SG_CNT;
-- 
2.42.0