Subject: Re: Kernel 4.13.0-rc4-next-20170811 - IP Routing / Forwarding performance vs Core/RSS number / HT on

From: Jesper Dangaard Brouer <[email-masked]>
Date: Tue, 15 Aug 2017 12:05:39 +0200

On Tue, 15 Aug 2017 11:11:57 +0200 Paweł Staszewski <[email-masked]> wrote:

> Yes it helped - now there is almost no difference when using vlans or not:
> 
> 10.5Mpps - with vlan
> 
> 11Mpps - without vlan

Great! - it seems like we have pinpointed the root-cause.  It also
demonstrate how big the benefit is of Eric commit (thanks!):
 https://git.kernel.org/torvalds/c/93f154b594fe

> W dniu 2017-08-15 o 03:17, Eric Dumazet pisze:
> > On Mon, 2017-08-14 at 18:07 -0700, Eric Dumazet wrote:
> >  
> >> Or try to hack the IFF_XMIT_DST_RELEASE flag on the vlan netdev.  
> > Something like :
> >
> > diff --git a/net/8021q/vlan_netlink.c b/net/8021q/vlan_netlink.c
> > index 5e831de3103e2f7092c7fa15534def403bc62fb4..9472de846d5c0960996261cb2843032847fa4bf7 100644
> > --- a/net/8021q/vlan_netlink.c
> > +++ b/net/8021q/vlan_netlink.c
> > @@ -143,6 +143,7 @@ static int vlan_newlink(struct net *src_net, struct net_device *dev,
> >   	vlan->vlan_proto = proto;
> >   	vlan->vlan_id	 = nla_get_u16(data[IFLA_VLAN_ID]);
> >   	vlan->real_dev	 = real_dev;
> > +	dev->priv_flags |= (real_dev->priv_flags & IFF_XMIT_DST_RELEASE);
> >   	vlan->flags	 = VLAN_FLAG_REORDER_HDR;
> >   
> >   	err = vlan_check_real_dev(real_dev, vlan->vlan_proto, vlan->vlan_id);

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer