On Thu, 25 Jan 2024 13:42:05 +0800, Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote: > On Thu, 25 Jan 2024 11:39:28 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote: > > On Tue, Jan 16, 2024 at 3:59 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote: > > > > > > This is the second part of virtio-net support AF_XDP zero copy. > > > > > > The whole patch set > > > http://lore.kernel.org/all/20231229073108.57778-1-xuanzhuo@xxxxxxxxxxxxxxxxx > > > > > > ## About the branch > > > > > > This patch set is pushed to the net-next branch, but some patches are about > > > virtio core. Because the entire patch set for virtio-net to support AF_XDP > > > should be pushed to net-next, I hope these patches will be merged into net-next > > > with the virtio core maintains's Acked-by. > > > > > > ============================================================================ > > > > > > ## 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. > > > > > > > Rethink of the whole design, I have one question: > > > > The reason we need to store DMA information is to harden the virtqueue > > to make sure the DMA unmap is safe. This seems redundant when the > > buffer were premapped by the driver, for example: > > > > Receive queue maintains DMA information, so it doesn't need desc_extra to work. > > > > So can we simply > > > > 1) when premapping is enabled, store DMA information by driver itself > > YES. this is simpler. And this is more convenience. > But the driver must allocate memory to store the dma info. > > > 2) don't store DMA information in desc_extra > > YES. But the desc_extra memory is wasted. The "next" item is used. > Do you think should we free the desc_extra when the vq is premapped mode? struct vring_desc_extra { dma_addr_t addr; /* Descriptor DMA addr. */ u32 len; /* Descriptor length. */ u16 flags; /* Descriptor flags. */ u16 next; /* The next desc state in a list. */ }; The flags and the next are used whatever premapped or not. So I think we can add a new array to store the addr and len. If the vq is premappd, the memory can be freed. struct vring_desc_extra { u16 flags; /* Descriptor flags. */ u16 next; /* The next desc state in a list. */ }; struct vring_desc_dma { dma_addr_t addr; /* Descriptor DMA addr. */ u32 len; /* Descriptor length. */ }; Thanks. > > Thanks. > > > > > > Would this be simpler? > > > > Thanks > >
