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Date:   Thu, 10 Nov 2016 06:19:05 +0000
From:   "Zhangming (James, Euler)" <james.zhangming@...wei.com>
To:     Jason Wang <jasowang@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "Michael S. Tsirkin" <mst@...hat.com>,
        Vlad Yasevic <vyasevic@...hat.com>
Subject: Re: Virtio_net support vxlan encapsulation package TSO offload
 discuss

On 2016年11月09日 15:14, Jason Wang wrote:
>On 2016年11月08日 19:58, Zhangming (James, Euler) wrote:
>> On 2016年11月08日 19:17, Jason Wang wrote:
>>
>>> On 2016年11月08日 19:13, Jason Wang wrote:
>>>> Cc Michael
>>>>
>>>> On 2016年11月08日 16:34, Zhangming (James, Euler) wrote:
>>>>> In container scenario, OVS is installed in the Virtual machine, and 
>>>>> all the containers connected to the OVS will communicated through 
>>>>> VXLAN encapsulation.
>>>>>
>>>>> By now, virtio_net does not support TSO offload for VXLAN 
>>>>> encapsulated TSO package. In this condition, the performance is not 
>>>>> good, sender is bottleneck
>>>>>
>>>>> I googled this scenario, but I didn’t find any information. Will 
>>>>> virtio_net support VXLAN encapsulation package TSO offload later?
>>>>>
>>>> Yes and for both sender and receiver.
>>>>
>>>>> My idea is virtio_net open encapsulated TSO offload, and transport 
>>>>> encapsulation info to TUN, TUN will parse the info and build skb 
>>>>> with encapsulation info.
>>>>>
>>>>> OVS or kernel on the host should be modified to support this. Using 
>>>>> this method, the TCP performance aremore than 2x as before.
>>>>>
>>>>> Any advice and suggestions for this idea or new idea will be 
>>>>> greatly appreciated!
>>>>>
>>>>> Best regards,
>>>>>
>>>>>     James zhang
>>>>>
>>>> Sounds very good. And we may also need features bits
>>>> (VIRTIO_NET_F_GUEST|HOST_GSO_X) for this.
>>>>
>>>> This is in fact one of items in networking todo list. (See 
>>>> http://www.linux-kvm.org/page/NetworkingTodo). While at it, we'd 
>>>> better support not only VXLAN but also other tunnels.
>>> Cc Vlad who is working on extending virtio-net headers.
>>>
>>>> We can start with the spec work, or if you've already had some bits 
>>>> you can post them as RFC for early review.
>>>>
>>>> Thanks
>> Below is my demo code
>> Virtio_net.c
>> static int virtnet_probe(struct virtio_device *vdev), add belows codes:
>>          if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF) ||				// avoid gso segment, it should be negotiation later, because in the demo I reuse num_buffers.
>>              virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
>>                  dev->hw_enc_features |= NETIF_F_TSO;
>>                  dev->hw_enc_features |= NETIF_F_ALL_CSUM;
>>                  dev->hw_enc_features |= NETIF_F_GSO_UDP_TUNNEL;
>>                  dev->hw_enc_features |= NETIF_F_GSO_UDP_TUNNEL_CSUM;
>>                  dev->hw_enc_features |= NETIF_F_GSO_TUNNEL_REMCSUM;
>>
>>                  dev->features |= NETIF_F_GSO_UDP_TUNNEL;
>>                  dev->features |= NETIF_F_GSO_UDP_TUNNEL_CSUM;
>>                  dev->features |= NETIF_F_GSO_TUNNEL_REMCSUM;
>>          }
>>
>> static int xmit_skb(struct send_queue *sq, struct sk_buff *skb), add 
>> below to pieces of codes
>>
>>                  if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL)
>>                          hdr->hdr.gso_type |= VIRTIO_NET_HDR_GSO_TUNNEL;
>>                  if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM)
>>                          hdr->hdr.gso_type |= VIRTIO_NET_HDR_GSO_TUNNEL_CSUM;
>>                  if (skb_shinfo(skb)->gso_type & SKB_GSO_TUNNEL_REMCSUM)
>>                          hdr->hdr.gso_type |= 
>> VIRTIO_NET_HDR_GSO_TUNNEL_REMCSUM;
>>
>>          if (skb->encapsulation && skb_is_gso(skb)) {
>>                  inner_mac_len = skb_inner_network_header(skb) - skb_inner_mac_header(skb);
>>                  tnl_len = skb_inner_mac_header(skb) - skb_mac_header(skb);
>>                  if ( !(inner_mac_len >> DATA_LEN_SHIFT) && !(tnl_len >> DATA_LEN_SHIFT) ) {
>>                          hdr->hdr.flags |= VIRTIO_NET_HDR_F_ENCAPSULATION;
>>                          hdr->num_buffers = (__virtio16)((inner_mac_len << DATA_LEN_SHIFT) | tnl_len);		//we reuse num_buffers for simple , we should add extend member for later.
>>                  }  else
>>                          hdr->num_buffers = 0;
>>          }
>>
>> Tun.c
>>                  if (memcpy_fromiovecend((void *)&hdr, iv, offset, tun->vnet_hdr_sz))		//read header with negotiation length
>>                          return -EFAULT;
>>
>>                  if (hdr.gso_type & VIRTIO_NET_HDR_GSO_TUNNEL)					//set tunnel gso info
>>                          skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
>>                  if (hdr.gso_type & VIRTIO_NET_HDR_GSO_TUNNEL_CSUM)
>>                          skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
>>                  if (hdr.gso_type & VIRTIO_NET_HDR_GSO_TUNNEL_REMCSUM)
>>                          skb_shinfo(skb)->gso_type |= 
>> SKB_GSO_TUNNEL_REMCSUM;
>>
>>          if (hdr.flags & VIRTIO_NET_HDR_F_ENCAPSULATION) {						//read tunnel info from header and set to built skb.
>>                  tnl_len = tun16_to_cpu(tun, hdr.num_buffers) & TUN_TNL_LEN_MASK;
>>                  payload_mac_len = tun16_to_cpu(tun, hdr.num_buffers) >> TUN_DATA_LEN_SHIFT;
>>                  mac_len = skb_network_header(skb) - skb_mac_header(skb);
>>                  skb_set_inner_mac_header(skb, tnl_len - mac_len);
>>                  skb_set_inner_network_header(skb, tnl_len + payload_mac_len - mac_len);
>>                  skb->encapsulation = 1;
>>          }
>>
>>
>
>Something like this, and you probably need do something more:
>
>- use net-next.git to generate the patch (for the latest code)
>- add feature negotiation
>- tun/macvtap/qemu patches for this, you can start with tun/macvtap patches
>- support for all other SKB_GSO_* types which is not supported
>- use a new field instead of num_buffers
>- a virtio spec patch to describe the support for encapsulation offload
>
>Thanks

Thank you for your advice, I will start it right now.

Thanks

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