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

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Message-ID: <1340183793.4604.846.camel@edumazet-glaptop>
Date:	Wed, 20 Jun 2012 11:16:33 +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 11:06 +0200, Stefan Priebe - Profihost AG wrote:
> Am 20.06.2012 10:41, schrieb Eric Dumazet:
> > On Wed, 2012-06-20 at 10:21 +0200, Stefan Priebe - Profihost AG wrote:
> >> Am 20.06.2012 09:22, schrieb Eric Dumazet:
> > Yes, you already told that in subject line.
> >
> > single tcp flow ?
> I use iperf - i think it uses just a single tcp flow. But i'm not sure.
> 
> > 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.

I was suggesting rate limiting on your linux sender machine, just to
verify if its indeed a problem on the path.

Its a matter of a "tc qdisc ..." command ;)

Or maybe iperf has an option for rate limiting.



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