Re: [PATCH net-next v2 00/21] virtio-net: support AF_XDP zero copy

Michael S. Tsirkin
2023-11-09T08:19:14Z

On Tue, Nov 07, 2023 at 11:12:06AM +0800, Xuan Zhuo 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).
> Host CPU: Intel(R) Xeon(R) Platinum 8163 CPU @ 2.50GHz
>
> ### virtio PMD in guest with testpmd
>
> testpmd> show port stats all
>
> ######################## NIC statistics for port 0 ########################
> RX-packets: 19531092064 RX-missed: 0 RX-bytes: 1093741155584
> RX-errors: 0
> RX-nombuf: 0
> TX-packets: 5959955552 TX-errors: 0 TX-bytes: 371030645664
>
>
> Throughput (since last show)
> Rx-pps: 8861574 Rx-bps: 3969985208
> Tx-pps: 8861493 Tx-bps: 3969962736
> ############################################################################
>
> ### AF_XDP PMD in guest with testpmd
>
> testpmd> show port stats all
>
> ######################## NIC statistics for port 0 ########################
> RX-packets: 68152727 RX-missed: 0 RX-bytes: 3816552712
> RX-errors: 0
> RX-nombuf: 0
> TX-packets: 68114967 TX-errors: 33216 TX-bytes: 3814438152
>
> Throughput (since last show)
> Rx-pps: 6333196 Rx-bps: 2837272088
> Tx-pps: 6333227 Tx-bps: 2837285936
> ############################################################################
>
> But AF_XDP consumes more CPU for tx and rx napi(100% and 86%).
>
> ## maintain
>
> I am currently a reviewer for virtio-net. I commit to maintain AF_XDP support in
> virtio-net.
>
> Please review.
>
> Thanks.
>
> v2
> 1. wakeup uses the way of GVE. No send ipi to wakeup napi on remote cpu.
> 2. remove rcu. Because we synchronize all operat, so the rcu is not needed.
> 3. split the commit "move to virtio_net.h" in last patch set. Just move the
> struct/api to header when we use them.
> 4. add comments for some code
>
> 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 (21):
> 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 core structures to virtio_net.h
> virtio_net: add prefix virtnet to all struct 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: move some api to header
> 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: skip dma unmap when rq is bind with AF_XDP
> 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} | 630 +++++++++-----------
> drivers/net/virtio/virtio_net.h | 346 +++++++++++
> drivers/net/virtio/xsk.c | 498 ++++++++++++++++
> drivers/net/virtio/xsk.h | 32 +
> 9 files changed, 1174 insertions(+), 365 deletions(-)
> create mode 100644 drivers/net/virtio/Kconfig
> create mode 100644 drivers/net/virtio/Makefile
> rename drivers/net/{virtio_net.c => virtio/main.c} (92%)
> 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

Too much code duplications for my taste. Would there maybe be less if
everything was in a single file?

> --
> 2.32.0.3.g01195cf9f