[LARTC] Bandwidth Control Tolerances

[Martin A. Brown]

Hello Patrick,

Please excuse my suggestion if you have already considered the issue I
indicate below from Stef's FAQ.

 : I have measured the performance of HTB with iperf and found it to be
 : very close to expected (i.e., within 5%). I have a colleague who is
 : measuring the performance by ftp'ing large files and recording the time
 : required to make the transfer. He is seeing an average throughput that
 : is nearly 10% away from the theoretical, with occasional excursions to
 : nearly 30%.

How have you defined your PSCHED_CLOCK_SOURCE?  See this URL:

  http://www.docum.org/stef.coene/qos/faq/cache/40.html

 : My colleague is now questioning the quality of the traffic control
 : algorithms and wondering two things:

Let's be careful with the baby and the bathwater.  The algorithms have
been vetted.  The implementation may not be ideal, but implementations
always suffer from compromises, right?

 : 1) What tolerance can we guarantee and advertise?

Measure the deviations from your specified bandwidth after changing your
setting for PSCHED_CLOCK_SOURCE.  Advertise your measured tolerance
accordingly.

 : 2) Can the tolerance be improved, since the values he has measured are
 : unacceptable?

I don't know--see the above link, and check how your kernel was compiled.
Others on this list may have further suggestions for you.

Good luck,

-Martin

-- 
Martin A. Brown --- SecurePipe, Inc. --- mabrown@securepipe.com