netdev - Re: [RFC net-next 00/13] virtio-net: support AF

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Message-ID: <CACGkMEsX5CwQmrwYzosSDMRdOfYVEmaL6x0-M9fWq0whwyRwSQ@mail.gmail.com>
Date: Mon, 22 Jul 2024 15:27:42 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>, 
	Eugenio Pérez <eperezma@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, virtualization@...ts.linux.dev, 
	bpf@...r.kernel.org
Subject: Re: [RFC net-next 00/13] virtio-net: support AF_XDP zero copy (tx)

On Tue, Jul 16, 2024 at 2:46 PM Xuan Zhuo <xuanzhuo@...ux.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.
>
> This patch set includes some refactor to the virtio-net to let that to support
> AF_XDP.
>
> ## About virtio premapped mode
>
> The current configuration sets the virtqueue (vq) to premapped mode,
> implying that all buffers submitted to this queue must be mapped ahead
> of time. This presents a challenge for the virtnet send queue (sq): the
> virtnet driver would be required to keep track of dma information for vq
> size * 17, which can be substantial. However, if the premapped mode were
> applied on a per-buffer basis, the complexity would be greatly reduced.
> With AF_XDP enabled, AF_XDP buffers would become premapped, while kernel
> skb buffers could remain unmapped.
>
> We can distinguish them by sg_page(sg), When sg_page(sg) is NULL, this
> indicates that the driver has performed DMA mapping in advance, allowing
> the Virtio core to directly utilize sg_dma_address(sg) without
> conducting any internal DMA mapping. Additionally, DMA unmap operations
> for this buffer will be bypassed.
>
> ## 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%).
>
> Please review.
>
> Thanks.
>
> Xuan Zhuo (13):
>   virtio_ring: introduce vring_need_unmap_buffer
>   virtio_ring: split: harden dma unmap for indirect
>   virtio_ring: packed: harden dma unmap for indirect
>   virtio_ring: perform premapped operations based on per-buffer
>   virtio-net: rq submits premapped buffer per buffer
>   virtio_ring: remove API virtqueue_set_dma_premapped
>   virtio_net: refactor the xmit type
>   virtio_net: xsk: bind/unbind xsk for tx
>   virtio_net: xsk: prevent disable tx napi
>   virtio_net: xsk: tx: support xmit xsk buffer
>   virtio_net: xsk: tx: handle the transmitted xsk buffer
>   virtio_net: update tx timeout record
>   virtio_net: xdp_features add NETDEV_XDP_ACT_XSK_ZEROCOPY
>
>  drivers/net/virtio_net.c     | 363 ++++++++++++++++++++++++++++-------
>  drivers/virtio/virtio_ring.c | 302 ++++++++++++-----------------
>  include/linux/virtio.h       |   2 -
>  3 files changed, 421 insertions(+), 246 deletions(-)
>
> --
> 2.32.0.3.g01195cf9f
>

Hi Xuan:

I wonder why this series is tagged as "RFC"?

Thanks