[LARTC] Extremely inaccurate results using either TBF or HTB

["Dan Farino" <DFarino@Stamps.com>]

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Hi everyone,

 

I am getting extremely inaccurate results from my setup:

- RedHat 8.0 on a Compaq ProLiant 1600, dual PII/450, Intel Dual 100 NIC

- I've tried both SMP and non-SMP kernels.

- I'm using the updated tc from the HTB home page.

- I'm using the HTB that comes with the RH8 kernel.

 

Here's what's happening. If I, for instance:

     tc qdisc add dev eth2 root tbf rate 1.9mbit buffer 20Kb/8 limit
15Kb

 

Then my download rate goes at 360,000 bytes/s, which, by my
calculations, is 2.77mbit. I am using Win2k perfmon to test the speed.
The line is flat and the speed is very consistent (consistently *wrong*,
unfortunately...)

 

Immediately after, I do:

     tc qdisc change dev eth2 root tbf rate 1.8mbit buffer 20Kb/8 limit
15Kb

 

My download speed is then 243,000 bytes/s, or 1.85mbit. Again, very
flat, consistent line.

 

I have played with the parameters on both TBF and HTB in many different
configurations. I always seem to have a large jump between 1.8-1.9. I
can't find any number between those two that will actually produce a
2mbit limit. I know 1.85 is close to 2.0, but is this the expected
margin of error? (Then again, 2.77 isn't close to 1.9 at all, so I hope
not!)

 

Has anyone else experienced anything like this?

 

Thank you very much for any help you can provide!

 

Dan Farino

Sr. System Engineer

Stamps.com, Inc.

Santa Monica, CA

 


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