netdev - Re: 10GBE performance drop with net.ipv4.tcp

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Message-ID: <1340183854.4604.847.camel@edumazet-glaptop>
Date:	Wed, 20 Jun 2012 11:17:34 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
Cc:	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: 10GBE performance drop with net.ipv4.tcp_timestamps=0

On Wed, 2012-06-20 at 11:12 +0200, Stefan Priebe - Profihost AG wrote:
> Am 20.06.2012 11:06, schrieb Stefan Priebe - Profihost AG:
> >> You seem to have a switch or something that drops packets in this case.
> >> You could try to rate limit to 9Gb/s and see if it is better.
> > Sadly i can't rate limit to 9Gbit/s on the switch.
> >
> >> Here, I roughly have same bandwidth with tcp_timestamps on or off, with
> >> ixgbe cards and net-next kernels.
> > Mhm strange. Do you have any vague idea what could cause this? Any wrong
> > reordering of the packets without tcp_timestamps?
> 
> I've now done another test without the switch. So both systems where 
> direct attached and still the same. Without tcp_timstamps speed drops to 
> 2-4Gbit/s.
> 
> Stefan


If you exchange sender/receiver role between linux kernel versions, is
it the same problem ?


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