Re: [RFC -next 00/10] Add ZC notifications to splice and sendfile

Christoph Hellwig
2025-03-20T05:50:19Z

On Wed, Mar 19, 2025 at 08:32:19AM -0700, Joe Damato wrote:
> See the docs on MSG_ZEROCOPY [1], but in short when a user app calls
> sendmsg and passes MSG_ZEROCOPY a completion notification is added
> to the error queue. The user app can poll for these to find out when
> the TX has completed and the buffer it passed to the kernel can be
> overwritten.

Yikes. That's not just an ugly interface, but something entirely
specific to sockets and incompatible with all other asynchronous I/O
interfaces.

> > and why aren't you simply plugging this into io_uring and generate
> > a CQE so that it works like all other asynchronous operations?
>
> I linked to the iouring work that Pavel did in the cover letter.
> Please take a look.

Please write down what matters in the cover letter, including all the
important tradeoffs.