Re: [RFC v2 00/11] Add vhost-net kernel support

[Eugenio Perez Martin <eperezma@redhat.com>]

On Wed, Jul 9, 2025 at 7:48 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> vhost-net is a kernel device that allows to read packets from a tap
> device using virtio queues instead of regular read(2) and write(2).
> This enables a more eficient packet processing, as the memory can
> be written directly by the kernel to the userspace and back, instead
> of wasting bandwith on copies, and it enables to batch many packets
> in a single notification (through eventfds) both tx and rx.
>
> Namespace tx performance improves from ~26.3Gbit/s to ~36.9Gbit/s.
>
> Namespace rx performance improves from ~16BGbit/s to ~17.26Gbit/s.
>

For reference, iperf without namespaces and veth both reaches
~47.8Gbit/s in both directions.

> RFC: At this moment only these are supported:
> * Receive l2 packets from the vhost kernel to pasta
> * Send l4 tcp socket received data through vhost-kernel to namespace.
>
> TODO: Add vhost zerocopy in the tests, and compare with veth.
> TODO: Implement at least UDP tx.  Or maybe we want UDP to be write(2) because
> of latency?
> TODO: Check style for variable declarations in for loops and use of curly
> brackets as long as they wrap more than a line.
> TODO: kerneldoc style function header comments
>
> --
> v2: Add TCP tx, and integrated some comments from the previous series. Please
>     check each patch message for details.
>
> Eugenio Pérez (11):
>   tap: implement vhost_call_cb
>   tap: add die() on vhost error
>   Replace tx tap hdr with virtio_nethdr_mrg_rxbuf
>   tcp: export memory regions to vhost
>   virtio: Fill .next in tx queue
>   tap: move static iov_sock to tcp_buf_data_from_sock
>   tap: support tx through vhost
>   tap: add tap_free_old_xmit
>   tcp: start conversion to circular buffer
>   Add poll(2) to used_idx
>   tcp_buf: adding TCP tx circular buffer
>
>  arp.c        |   2 +-
>  epoll_type.h |   4 +
>  passt.c      |  12 +-
>  passt.h      |  11 +-
>  tap.c        | 489 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  tap.h        |  13 +-
>  tcp.c        |   2 +-
>  tcp_buf.c    | 179 +++++++++++++++----
>  tcp_buf.h    |  19 ++
>  udp.c        |   2 +-
>  10 files changed, 675 insertions(+), 58 deletions(-)
>
> --
> 2.50.0
>