Re: [PATCH 0/3][RFC] virtio-blk: add io_uring passthrough support for virtio-blk

Jingbo Xu
2024-12-17T06:08:31Z

Hi Stefan & Christoph,

On 12/17/24 12:13 AM, Stefan Hajnoczi wrote:
> On Mon, 16 Dec 2024 at 10:54, Christoph Hellwig <hch@infradead.org> wrote:
>>
>> Hacking passthrough into virtio_blk seems like not very good layering.
>> If you have a use case where you want to use the core kernel virtio code
>> but not the protocol drivers we'll probably need a virtqueue passthrough
>> option of some kind.
>
> I think people are finding that submitting I/O via uring_cmd is faster
> than traditional io_uring. The use case isn't really passthrough, it's
> bypass :).

Right, the initial purpose is bypassing the block layer (in the guest)
to achieve better latency when the user process is operating on a raw
virtio-blk device directly.

>
> That's why I asked Jens to weigh in on whether there is a generic
> block layer solution here. If uring_cmd is faster then maybe a generic
> uring_cmd I/O interface can be defined without tying applications to
> device-specific commands. Or maybe the traditional io_uring code path
> can be optimized so that bypass is no longer attractive.

We are fine with that if it looks good to Jens.

--
Thanks,
Jingbo