Which version of iperf 2 are you running? We did some work in 2.0.8_+ for
UDP throughput including using realtime clocks (vs. gettime of day) as well
as support realtime scheduling of the traffic threads. Also increased
shared memory significantly between traffic threads and the reporter thread
to reduce mutex contention. Could be other things too, as finding a
performance bottleneck is a bit tricky ;)
If you're using 2.0.5 none of the above applies.
Bob
On Thu, Jun 2, 2016 at 1:19 PM, Jeffrey Lane <jeffrey.l...@canonical.com>
wrote:
> I am running into a problem where there is a remarkable difference in
> reported throughput when using iperf2 vs iperf3.
>
> With iperf2, and about 16 - 20 threads, I can get, reliably, between
> 32 and 35 Gb/s on a 40Gb segment. with iperf3 on exactly the same
> hardware, I only get 4Gb/s, sometimes I can get up to 11Gb/s.
>
> Is there some trick to getting more accurate results out of iperf3?
>
> There is nothing special about the network, in fact, the network
> consists of two servers with 40Gb cards connected directly, no
> intervening switch. There is no routing issue that I can find, the
> 40Gb ports are on a completely different address space than the
> onboard 1Gb ports, AND the 1Gb ports on each server can't talk to each
> other. Physically the ONLY way these servers can talk to each other
> is across the 40Gb link.
>
> Another person opened a bug for this:
> https://github.com/esnet/iperf/issues/408
>
> and there are now three people on that thread reporting the same issues.
>
> Any suggestions for how to debug or resolve this?
>
>
> --
> "Entropy isn't what it used to be."
>
> Jeff Lane -
> Server Certification Lead, Warrior Poet, Biker, Lover of Pie
> Phone: 919-442-8649
> Ubuntu Ham: W4KDH Freenode IRC: bladernr or
> bladernr_
> gpg: 1024D/3A14B2DD 8C88 B076 0DD7 B404 1417 C466 4ABD 3635 3A14 B2DD
>
>
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