Re: [PATCH] virtio_blk: set the default scheduler to none

Michael S. Tsirkin
2023-12-25T14:21:03Z

On Thu, Dec 07, 2023 at 12:31:05PM +0800, Li Feng wrote:
> 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>

I dropped this for now, pls try to address comments by Christoph/Paolo
if it's still needed

> ---
> 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