From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: 10GBE performance drop with net.ipv4.tcp_timestamps=0
Date: Wed, 20 Jun 2012 10:41:16 +0200
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To: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
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On Wed, 2012-06-20 at 10:21 +0200, Stefan Priebe - Profihost AG wrote:
> Am 20.06.2012 09:22, schrieb Eric Dumazet:
> > On Wed, 2012-06-20 at 09:00 +0200, Stefan Priebe - Profihost AG wrote:
> >> Am 19.06.2012 23:31, schrieb Eric Dumazet:
> >> Before:
> >> http://pastebin.com/raw.php?i=1gVraWVc
> >>
> >> After:
> >> http://pastebin.com/raw.php?i=NSh8Y29s
> >
> > You have a lot of packet losses
> But this ONLY happens with tcp_timestamps=0.
> 

Yes, you already told that in subject line.

single tcp flow ?

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.

Here, I roughly have same bandwidth with tcp_timestamps on or off, with
ixgbe cards and net-next kernels.