Re: [rtl] Measurement test example

[Oleg Subbotin <oleg@rtlinux.cs.nmt.edu>]

On Mon, 20 Jul 1998, Joshua Lamorie wrote:

> Gidday there,
> 
> 	What does the measurement test do?  I inserted the rt_process module,
> and saw the output
> from the monitor
> 
> 	Min: 12 Max: 47
> 
> 	Then I inserted the rt_irq module and the output became.
> 
> 	Min: 13 Max: 2883
> 
> 	What are those numbers?  Latency in microseconds?  What do the
> different modules do?
> 
> thanks
> 
> Joshua

Ok. This example shows difference between "expected" switch time and actual
switch time. So numbers show maximum and minimum "miss" delay.
This example does not produce any valuable information if you insert additional
modules ( or rt tasks with higher priority ). Using the output you can tune the
scheduler to reduce this time. Find "#define ADJUSTMENT 34" in the
rt_prio_sced.c and change it to 45 ( == 34+12-1 ; NOTE using 46 is not
recommended - you can have cases when task will scheduled to run _before_ its
time ). recompile example and run it again. 
The delays should be distributed between 1 (min) and 36(max). 

Out tests show that average miss time for "tuned" system is ~0 with  about 
3 to 5 percents(or even less) miss time greater then 4.

All numbers are roughly microseconds.

Oleg. 

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