Re: [PATCH 0/4] io_uring: add IORING_OP_READ[WRITE]_SPLICE_BUF

Jens Axboe
2023-02-10T21:55:16Z

On 2/10/23 8:32 AM, Ming Lei wrote:
> Hello,
>
> Add two OPs which buffer is retrieved via kernel splice for supporting
> fuse/ublk zero copy.
>
> The 1st patch enhances direct pipe & splice for moving pages in kernel,
> so that the two added OPs won't be misused, and avoid potential security
> hole.
>
> The 2nd patch allows splice_direct_to_actor() caller to ignore signal
> if the actor won't block and can be done in bound time.
>
> The 3rd patch add the two OPs.
>
> The 4th patch implements ublk's ->splice_read() for supporting
> zero copy.
>
> ublksrv(userspace):
>
> https://github.com/ming1/ubdsrv/commits/io_uring_splice_buf
>
> So far, only loop/null target implements zero copy in above branch:
>
> ublk add -t loop -f $file -z
> ublk add -t none -z
>
> Basic FS/IO function is verified, mount/kernel building & fio
> works fine, and big chunk IO(BS: 64k/512k) performance gets improved
> obviously.

Do you have any performance numbers? Also curious on liburing regression
tests, would be nice to see as it helps with review.

Caveat - haven't looked into this in detail just yet.

--
Jens Axboe