Thank you for your reply.
I see the function skb_udp_tunnel_segment in file linux-3.14\net\ipv4\udp.c
struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
netdev_features_t features)
(...skip...)
/* segment inner packet. */
enc_features = skb->dev->hw_enc_features & netif_skb_features(skb); ★
(...skip...)
Is ★ used for deciding whether the NIC supports vxlan offload ?
If so, where is the skb->dev set ? Is skb->dev the physical NIC or is it the
vxlan virtual port?
At 2015-09-21 21:28:48, "Flavio Leitner" <[email protected]> wrote:
>On Fri, Sep 18, 2015 at 04:32:05PM +0800, openvswitcher wrote:
>> Why the vxlan offloading NICs can improve the bandwith performance?
>> Could you explain me by the source code?
>
>You have TSO and checksumming offloading on your card at least
>and very likely enabled by default. So, the iperf can send
>up to 64k bytes of data at once, which will transverse all the
>networking stack once, and then the NIC will do all the heavy
>lifting segmenting the packet and calculating the chsum.
>
>With VXLAN, that doesn't work anymore. The host CPU has to push
>MTU packets down into the networking stack each time and calculate
>chsum, etc... so the main CPU becomes a bottleneck.
>
>The work described above moves from the main CPU back to the NIC
>if you have/enable VXLAN offloading.
>
>fbl
>
>
>>
>>
>> Thanks.
>>
>>
>>
>>
>>
>>
>> At 2015-09-09 21:09:26, "YaoJun" <[email protected]> wrote:
>>
>> Try vxlan offloading firstly if you have the proper NICs.
>>
>>
>>
>> On Wed, Sep 9, 2015 at 6:35 PM, openvswitcher <[email protected]> wrote:
>> I use the openvswitch vxlan tunnel as the basic overlay service.
>> But I find the bandwith between two virtual machine only reaches 4G/s using
>> iperf to test.
>> So could anybody tell me how to improve it or where is the bottleneck?
>>
>>
>> Looking forward for your reply. Thank you!
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>>
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