Re: [Xenomai-help] strange latency output (xenomai-2.4.5)

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Georg Gottleuber wrote:
> 
> Gilles Chanteperdrix schrieb:
>> Georg Gottleuber wrote:
>>> Hi,
>>>
>>> I recently port a  ARM926EJ-S mach to Xenomai
>>> (like described in http://www.xenomai.org/index.php/I-pipe:ArmPorting).
>>>
>>> While testing with latency I got this output:
>>> # /usr/xenomai/bin/latency  -p 1000 -h -s -H 500 -t 1
>>> == Sampling period: 1000 us
>>> == Test mode: in-kernel periodic task
>>> == All results in microseconds
>>> warming up...
>>> RTT|  00:00:01  (in-kernel periodic task, 1000 us period, priority 99)
>>> RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat worst
>>> RTD|      78.992|     104.308|     124.131|       0|      78.992|     124.131
>>> ...
>>> RTD|      14.678|      68.413|      96.275|       0|       9.528|     155.321
>>> RTD|      84.046|     116.435|     175.192|       0|       9.528|     182.139
>>> ...                                ^^^^^^^                            ^^^^^^^
>> I do not understand, what is wrong with these values ?
> 
> It thought, if "lat max" of the current interval is bigger than "lat worst", this "lat
> max" updates the "lat worst". So I ask myself, out of which interval comes the updated 182
> value?

If your machine is highly loaded, like what you get with a ping -f, the
"display" thread, which is a non real-time one, may be delayed for more
than one second, in which case, it "misses", what is sent by the
"sampling" thread, but the sampling thread never looses the worst
latency itself, so that when the display thread finally manages to print
something, it will print the correct worst case latency.

-- 
                                                 Gilles.