## 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
