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:

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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.

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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 ?