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Subsequent iperf tcp runs yield much less throughput #134

Open GoogleCodeExporter opened 9 years ago

GoogleCodeExporter commented 9 years ago 
What steps will reproduce the problem?
1. iperf3 -s -V on srv1;iperf3 -c srv1 -V on srv2; (Note srv2 has just been 
rebooted.)
2. Note the TCP throughput. On my setup (10Gb link) it shows about 9.41Gbps 
after the first test
3. Run the client again. The throughput shown is about 300Mbps. 
4. Run the client again and see that the throughput does not change ; still is 
aroung 300Mbps

What is the expected output? What do you see instead?
Expected to see the pipe being filled - about 9.41Gbps always. 

What version of the product are you using? On what operating system?
3.0.1

Please provide any additional information below.
iperf version 3.0.1 (10 January 2014)
Linux srv2 3.8.0-35-generic #50~precise1-Ubuntu SMP Wed Dec 4 17:25:51 UTC 2013 
x86_64 x86_64 x86_64 GNU/Linux

Original issue reported on code.google.com by nsri...@gmail.com on 16 Jan 2014 at 9:59

GoogleCodeExporter commented 9 years ago 
Hrm.  Are you still seeing this?  I haven't seen anything like this personally, 
and I can't figure why you would get different results on runs after the first 
one.  I've done tests on 10G and 40G links on our testbed at ESnet and haven't 
observed this.

Out of curiosity what 10G NICs are you using?

Original comment by bmah@es.net on 3 Feb 2014 at 10:20