netdev - Re: linux-3.0.18+r8169+ipv4/tcp forwarding = tso/gso weirdness and performance degration

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Date:	Thu, 15 Mar 2012 17:11:48 +0200
From:	Timo Teras <timo.teras@....fi>
To:	Timo Teras <timo.teras@....fi>
Cc:	Francois Romieu <romieu@...zoreil.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	netdev@...r.kernel.org
Subject: Re: linux-3.0.18+r8169+ipv4/tcp forwarding = tso/gso weirdness and
 performance degration

On Thu, 15 Mar 2012 08:06:35 +0200 Timo Teras <timo.teras@....fi> wrote:

> On Wed, 14 Mar 2012 21:53:19 +0100 Francois Romieu
> <romieu@...zoreil.com> wrote:
> 
> > Timo Teras <timo.teras@....fi> :
> > [...]
> > > # ethtool -S eth2
> > > NIC statistics:
> > >      tx_packets: 2069391193
> > >      rx_packets: 3245815642
> > >      tx_errors: 0
> > >      rx_errors: 645238
> > >      rx_missed: 31414
> > 
> > It does not look like stuff for the higher layers guys.
> > 
> > Can you tshark -w foobar on the sender side and
> > 'while : ; do sleep 1; ethtool -S eth2 >> glop; done' on the
> > receiver during a bad wget (a big zero filled file should compress
> > well).
> 
> Indeed.
> 
> It seems that my earlier test about the "GRO off" effect were mistaken
> (I used accidentally proxy, and that gave the illusion that things are
> working. Whoops.)
> 
> So far I changed the cross-over cable and it didn't help. However,
> forcing the NIC to 100mbit/full-duplex mode fixes the rx_errors. It
> seems that something bad is happening in the gigabit mode.
> 
> I wonder if it's using pause frames and that's messing things up.
> Seems that I can't turn it off, though.
> 
> I can also double check my cables, though it is factory made Cat-5E
> cross-over cable; and happens with two different cables.

Ok. So far I have two of these boxes with same r8169 hardware. Both
generate bad packets on transmit only; and on both 3 nic systems it's
the middle eth1 nic. The symptoms are identical: in 1GB mode I have
minor packet loss, where as 100Mbit/s mode seems to work just fine.

The first box, that I've been talking so far about, is as mentioned
connected to another similar box. The r8169 there reports rx_errors.
The cable is ok; I've tried with two different ones.

The other broken box is connected to a HP ProCurve 4202vl-48G, and the
switch is reporting drops due to FCS Rx errors.

So I have two broken pieces of hardware, or there is a driver bug.

I'll try upgrading my kernel to 3.0.x series on the sender box and see
if it's fixing anything. Suggestions for further testing would be
appreciated.
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