Re: Iperf logging oddity on Linux with iperf 1.7.0
--On Wednesday, March 10, 2004 6:07 PM -0600 paul shields <pshields --at-- NAVINI.com> wrote:
> Below is a snippet of a log from a Linux server with the report interval set for 2 seconds and
> timestamps added as to exactly when iperf generated the line of output. The handling of time gaps
> seems incorrect. (notice timestamps are the same for some report intervals and all of the data
> rate is attributed to the fist interval print at that time. Iperf seems to want to "catch up" on
> the reporting process and generates a lot of false 0.0 output lines.
>
> The report should generate output for the combined 4-8 interval instead of creating two intervals
> and incorrectly reporting the data rate distribution between them.
>
> Comments?
> Paul
>
> 17:44:13 [ 18] local 172.27.2.28 port 5001 connected with 172.27.2.13 port 1215
> 17:44:16 [ 18] 0.0- 2.0 sec 12.8 KBytes 52.5 Kbits/sec
> 17:44:18 [ 18] 2.0- 4.0 sec 11.4 KBytes 46.7 Kbits/sec
> 17:44:23 [ 18] 4.0- 6.0 sec 2.85 KBytes 11.7 Kbits/sec
> 17:44:23 [ 18] 6.0- 8.0 sec 0.00 KBytes 0.00 Kbits/sec
> 17:44:27 [ 18] 8.0-10.0 sec 1.43 KBytes 5.84 Kbits/sec
> 17:44:27 [ 18] 10.0-12.0 sec 0.00 KBytes 0.00 Kbits/sec
> 17:44:30 [ 18] 12.0-14.0 sec 4.28 KBytes 17.5 Kbits/sec
> 17:44:30 [ 18] 14.0-16.0 sec 0.00 KBytes 0.00 Kbits/sec
> 17:44:32 [ 18] 16.0-18.0 sec 5.70 KBytes 23.4 Kbits/sec
> 17:44:37 [ 18] 18.0-20.0 sec 1.50 KBytes 6.16 Kbits/sec
> 17:44:37 [ 18] 20.0-22.0 sec 0.00 KBytes 0.00 Kbits/sec
> 17:44:41 [ 18] 22.0-24.0 sec 1.43 KBytes 5.84 Kbits/sec
> 17:44:41 [ 18] 24.0-26.0 sec 0.00 KBytes 0.00 Kbits/sec
> 17:44:41 [ 18] 26.0-28.0 sec 1.43 KBytes 5.84 Kbits/sec
> 17:44:44 [ 18] 28.0-30.0 sec 5.15 KBytes 21.1 Kbits/sec
I've seen something similar with iperf 1.7 as well as iperf 2 betas
when running under RH9 on gigE-connected systems. The bitrates
are quite a bit higher, but some runs have intervals that report
0 bits sent! Other runs are consistent at 980-ish Mb/s.
A related observation is that when I try to do 900 Mb/s UDP
streams, some runs are consistently right around 900 Mb/s,
and some runs also have intervals that report 0 bits sent.
In both of these cases, the intervals with data do not try
to "make up" for the missing bits; overall reports show
low bitrate transfers (usually 50 to 200 Mb/s for me :),
and no interval ever spikes above the physical maximum
bitrate. (What were you expecting in the runs you show?
is 0 bits sent over 2 seconds reasonable for you? Have
you tried any tcpdump or equivalent passive traces?)
I believe there may be an issue at the sender... alarms there
look like they are not delivered in time either. Maybe I've
got a bogus device driver? I haven't had time to pursue the
matter :(, instead choosing to filter out runs that look to
be completely bogus. This is not the correct long-term solution...
--Matt