Re: [PATCH net-next] virtio-net: switch to use build_skb() for small buffer

[Jason Wang <jasowang@redhat.com>]

On 2017年02月22日 11:17, Jason Wang wrote:
>
>
> On 2017年02月22日 11:06, Michael S. Tsirkin wrote:
>> On Wed, Feb 22, 2017 at 10:58:08AM +0800, Jason Wang wrote:
>>>
>>> On 2017年02月21日 22:37, Michael S. Tsirkin wrote:
>>>> On Tue, Feb 21, 2017 at 04:46:28PM +0800, Jason Wang wrote:
>>>>> This patch switch to use build_skb() for small buffer which can have
>>>>> better performance for both TCP and XDP (since we can work at page
>>>>> before skb creation). It also remove lots of XDP codes since both
>>>>> mergeable and small buffer use page frag during refill now.
>>>>>
>>>>>                          Before   | After
>>>>> XDP_DROP(xdp1) 64B  :  11.1Mpps | 14.4Mpps
>>>>>
>>>>> Tested with xdp1/xdp2/xdp_ip_tx_tunnel and netperf.
>>>>>
>>>>> Signed-off-by: Jason Wang<jasowang@redhat.com>
>>>> Thanks!
>>>> I had a similar patch for mergeable too, though it's trickier there
>>>> as host has a lot of flexibility in sizing buffers.
>>>> Looks like a good intermediate step to me.
>>> Yes, I think it's more tricky for the case of mergeable buffer:
>>>
>>> 1) we need reserve NET_SKB_PAD + NET_IP_ALIGN for each buffer, this 
>>> will
>>> break rx frag coalescing
>>> 2) need tailroom for skb_shinfo, so it won't work for all size of 
>>> packet
>>>
>>> Thanks
>> Have you seen my prototype?
>
> Not yet, please give me a pointer.

FYI, I posted a prototype during EWMA discussion in 2013:

https://lists.linuxfoundation.org/pipermail/virtualization/2013-October/025556.html