netdev - Re: NAT performance issue 944mbit -> ~40mbit

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Date:   Wed, 15 Jul 2020 14:40:17 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Ian Kumlien <ian.kumlien@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        jeffrey.t.kirsher@...el.com, intel-wired-lan@...ts.osuosl.org
Subject: Re: NAT performance issue 944mbit -> ~40mbit

On Wed, 15 Jul 2020 23:12:23 +0200 Ian Kumlien wrote:
> On Wed, Jul 15, 2020 at 11:02 PM Ian Kumlien <ian.kumlien@...il.com> wrote:
> > On Wed, Jul 15, 2020 at 10:31 PM Jakub Kicinski <kuba@...nel.org> wrote:  
> > > On Wed, 15 Jul 2020 22:05:58 +0200 Ian Kumlien wrote:  
> > > > After a  lot of debugging it turns out that the bug is in igb...
> > > >
> > > > driver: igb
> > > > version: 5.6.0-k
> > > > firmware-version:  0. 6-1
> > > >
> > > > 03:00.0 Ethernet controller: Intel Corporation I211 Gigabit Network
> > > > Connection (rev 03)  
> > >
> > > Unclear to me what you're actually reporting. Is this a regression
> > > after a kernel upgrade? Compared to no NAT?  
> >
> > It only happens on "internet links"
> >
> > Lets say that A is client with ibg driver, B is a firewall running NAT
> > with ixgbe drivers, C is another local node with igb and
> > D is a remote node with a bridge backed by a bnx2 interface.
> >
> > A -> B -> C is ok (B and C is on the same switch)
> >
> > A -> B -> D -- 32-40mbit
> >
> > B -> D 944 mbit
> > C -> D 944 mbit
> >
> > A' -> D ~933 mbit (A with realtek nic -- also link is not idle atm)  
> 
> This should of course be A' -> B -> D
> 
> Sorry, I've been scratching my head for about a week...

Hm, only thing that comes to mind if A' works reliably and A doesn't is
that A has somehow broken TCP offloads. Could you try disabling things
via ethtool -K and see if those settings make a difference?