Re: [PATCH v1 00/15] io_uring zero copy rx

Joe Damato
2024-10-09T16:11:01Z

On Wed, Oct 09, 2024 at 04:07:01PM +0100, Pavel Begunkov wrote:
> On 10/9/24 00:10, Joe Damato wrote:
> > On Mon, Oct 07, 2024 at 03:15:48PM -0700, David Wei wrote:
> > > This patchset adds support for zero copy rx into userspace pages using
> > > io_uring, eliminating a kernel to user copy.
> > >
> > > We configure a page pool that a driver uses to fill a hw rx queue to
> > > hand out user pages instead of kernel pages. Any data that ends up
> > > hitting this hw rx queue will thus be dma'd into userspace memory
> > > directly, without needing to be bounced through kernel memory. 'Reading'
> > > data out of a socket instead becomes a _notification_ mechanism, where
> > > the kernel tells userspace where the data is. The overall approach is
> > > similar to the devmem TCP proposal.
> > >
> > > This relies on hw header/data split, flow steering and RSS to ensure
> > > packet headers remain in kernel memory and only desired flows hit a hw
> > > rx queue configured for zero copy. Configuring this is outside of the
> > > scope of this patchset.
> >
> > This looks super cool and very useful, thanks for doing this work.
> >
> > Is there any possibility of some notes or sample pseudo code on how
> > userland can use this being added to Documentation/networking/ ?
>
> io_uring man pages would need to be updated with it, there are tests
> in liburing and would be a good idea to add back a simple exapmle
> to liburing/example/*. I think it should cover it

Ah, that sounds amazing to me!

I thought that suggesting that might be too much work ;) which is
why I had suggested Documentation/, but man page updates would be
excellent!