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

[Jason Wang]

On 2017å02æ22æ 11:17, Jason Wang wrote:
> On 2017å02æ22æ 11:06, Michael S. Tsirkin wrote:
> > On Wed, Feb 22, 2017 at 10:58:08AM +0800, Jason Wang wrote:
> > > On 2017å02æ21æ 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@xxxxxxxxxx>
> > > > 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