Re: [PATCH net-next v1 00/19] virtio-net: support AF_XDP zero copy

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Tue, 17 Oct 2023 10:53:44 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Mon, Oct 16, 2023 at 8:00 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > ## AF_XDP
> >
> > XDP socket(AF_XDP) is an excellent bypass kernel network framework. The zero
> > copy feature of xsk (XDP socket) needs to be supported by the driver. The
> > performance of zero copy is very good. mlx5 and intel ixgbe already support
> > this feature, This patch set allows virtio-net to support xsk's zerocopy xmit
> > feature.
> >
> > At present, we have completed some preparation:
> >
> > 1. vq-reset (virtio spec and kernel code)
> > 2. virtio-core premapped dma
> > 3. virtio-net xdp refactor
> >
> > So it is time for Virtio-Net to complete the support for the XDP Socket
> > Zerocopy.
> >
> > Virtio-net can not increase the queue num at will, so xsk shares the queue with
> > kernel.
> >
> > On the other hand, Virtio-Net does not support generate interrupt from driver
> > manually, so when we wakeup tx xmit, we used some tips. If the CPU run by TX
> > NAPI last time is other CPUs, use IPI to wake up NAPI on the remote CPU. If it
> > is also the local CPU, then we wake up napi directly.
> >
> > This patch set includes some refactor to the virtio-net to let that to support
> > AF_XDP.
> >
> > ## performance
> >
> > ENV: Qemu with vhost-user(polling mode).
> >
> > Sockperf: https://github.com/Mellanox/sockperf
> > I use this tool to send udp packet by kernel syscall.
> >
> > xmit command: sockperf tp -i 10.0.3.1 -t 1000
> >
> > I write a tool that sends udp packets or recvs udp packets by AF_XDP.
> >
> >                   | Guest APP CPU |Guest Softirq CPU | UDP PPS
> > ------------------|---------------|------------------|------------
> > xmit by syscall   |   100%        |                  |   676,915
> > xmit by xsk       |   59.1%       |   100%           | 5,447,168
> > recv by syscall   |   60%         |   100%           |   932,288
> > recv by xsk       |   35.7%       |   100%           | 3,343,168
>
> Any chance we can get a testpmd result (which I guess should be better
> than PPS above)?

Do you mean testpmd + DPDK + AF_XDP?

Yes. This is probably better because my tool does more work. That is not a
complete testing tool used by our business.

What I noticed is that the hotspot is the driver writing virtio desc. Because
the device is in busy mode. So there is race between driver and device.
So I modified the virtio core and lazily updated avail idx. Then pps can reach
10,000,000.

Thanks.

>
> Thanks
>
> >
> > ## maintain
> >
> > I am currently a reviewer for virtio-net. I commit to maintain AF_XDP support in
> > virtio-net.
> >
> > Please review.
> >
> > Thanks.
> >
> > v1:
> >     1. remove two virtio commits. Push this patchset to net-next
> >     2. squash "virtio_net: virtnet_poll_tx support rescheduled" to xsk: support tx
> >     3. fix some warnings
> >
> > Xuan Zhuo (19):
> >   virtio_net: rename free_old_xmit_skbs to free_old_xmit
> >   virtio_net: unify the code for recycling the xmit ptr
> >   virtio_net: independent directory
> >   virtio_net: move to virtio_net.h
> >   virtio_net: add prefix virtnet to all struct/api inside virtio_net.h
> >   virtio_net: separate virtnet_rx_resize()
> >   virtio_net: separate virtnet_tx_resize()
> >   virtio_net: sq support premapped mode
> >   virtio_net: xsk: bind/unbind xsk
> >   virtio_net: xsk: prevent disable tx napi
> >   virtio_net: xsk: tx: support tx
> >   virtio_net: xsk: tx: support wakeup
> >   virtio_net: xsk: tx: virtnet_free_old_xmit() distinguishes xsk buffer
> >   virtio_net: xsk: tx: virtnet_sq_free_unused_buf() check xsk buffer
> >   virtio_net: xsk: rx: introduce add_recvbuf_xsk()
> >   virtio_net: xsk: rx: introduce receive_xsk() to recv xsk buffer
> >   virtio_net: xsk: rx: virtnet_rq_free_unused_buf() check xsk buffer
> >   virtio_net: update tx timeout record
> >   virtio_net: xdp_features add NETDEV_XDP_ACT_XSK_ZEROCOPY
> >
> >  MAINTAINERS                                 |   2 +-
> >  drivers/net/Kconfig                         |   8 +-
> >  drivers/net/Makefile                        |   2 +-
> >  drivers/net/virtio/Kconfig                  |  13 +
> >  drivers/net/virtio/Makefile                 |   8 +
> >  drivers/net/{virtio_net.c => virtio/main.c} | 652 +++++++++-----------
> >  drivers/net/virtio/virtio_net.h             | 359 +++++++++++
> >  drivers/net/virtio/xsk.c                    | 545 ++++++++++++++++
> >  drivers/net/virtio/xsk.h                    |  32 +
> >  9 files changed, 1247 insertions(+), 374 deletions(-)
> >  create mode 100644 drivers/net/virtio/Kconfig
> >  create mode 100644 drivers/net/virtio/Makefile
> >  rename drivers/net/{virtio_net.c => virtio/main.c} (91%)
> >  create mode 100644 drivers/net/virtio/virtio_net.h
> >  create mode 100644 drivers/net/virtio/xsk.c
> >  create mode 100644 drivers/net/virtio/xsk.h
> >
> > --
> > 2.32.0.3.g01195cf9f
> >
>