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

Xuan Zhuo
2023-11-07T03:12:34Z

## 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

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2.32.0.3.g01195cf9f