Re: [Xenomai-help] [RTnet-users] Time scale problem.

[Jan Kiszka <jan.kiszka@domain.hid>]

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RAKOTOSALAMA, Nirilanto wrote:
> Hi Everyone
> 
> I'm programming a little client-server application to test network performances with xenomai 2.3.1 and rtnet 0.9.9.
> The 2 programs are based on the rtnet frag-ip example.
> The perdiodic scenario is :
> - RSG program sends a datagram to the REMOTE program which was waiting.
> - REMOTE sends a response to RSG.
> - RSG simulates a CPU performing period using rt_timer_spin.
> This cycle should take less than 2.5ms.
> 
> I observe strange time measurement :
> 
> For example when I want to run during 10 secs : 1000 cycles of 10 ms
> The program calculates a time between 16 and 17 secs (using rt_timer_tsc)
> But the effective elapsed time (i kept time with a chrono :-s ) is around 10secs

Before I start looking at details, please check the consistency of your
local Xenomai clock with this brand new tool:

http://svn.gna.org/viewcvs/xenomai/trunk/src/testsuite/clocktest/clocktest.c?view=markup
(you don't have to switch to trunk, just grab the source and compile
manually)

In case the Linux clock is not screwed up as well, you can check for
potential drifts and cross-cpu wraps that way.

> 
> When a cycle is supposed to be 5ms it is calculated to be 8.4ms
> 
> When I want a rt_timer_spin of 0.750ms, result is a 1.27ms burning period.
> 
> So a constant difference between effective and calculated time around +60%.
> 
> Maybe there something wrong in my program but I don't know what.
> Also, I have read some threads that mentionned time problem and /proc/xenomai/latency value.
> I didn't understand everything. 
> Any suggestion ?
> 
> 
> Thanks in advance.
> 
> Niry
> 

Jan


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