netdev - Re: GRO: forwading ISATAP packets is very slow with kernel 4.1

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Message-ID: <8145949.lUzHGl5xdY@h2o.as.studentenwerk.mhn.de>
Date:	Wed, 15 Jul 2015 02:34:41 +0200
From:	Wolfgang Walter <linux@...m.de>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	netdev@...r.kernel.org
Subject: Re: GRO: forwading ISATAP packets is very slow with kernel 4.1

Am Mittwoch, 15. Juli 2015, 08:08:49 schrieben Sie:
> On Wed, Jul 15, 2015 at 12:16:30AM +0200, Wolfgang Walter wrote:
> > Hello,
> > 
> > I upgraded routers from 3.14.x to 4.1.2. Forwarding ISATAP-packets (IPv4
> > packets with IPv6 payload) is very slow with 4.1 if GRO is enabled
> > (youtube
> > for example about 64kbit). Disabling GRO on the interfaces restores
> > performance to values comparable to 3.14.x.
> > 
> > The kernel is build with IPv6 support but IPv6 is disabled via kernel
> > command line. The router is not a tunnel endpoint, it only forwards the
> > ISATAP- packets. MTU is 1500 on both interfaces. Netfilter conntrack is
> > not used and disabling netfilter has no effect.
> 
> Can you run some tcpdumps and post the results in the two cases?
> 

Yes, but I need the cooperation of one of our customers.

I wonder if the router may treat all ipv6-tcp connections of a host as a 
single flow as all those ipv6-packets are embedded in ipv4-packets with the 
ipv4-address of the host and the ipv4-address of the isatap-gateway and next-
header is 41. It may only looks at those?

Regards,
-- 
Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts
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