Rudolf Marek wrote:
> Hello all,
> 
> I tried the latency and klatency demo on some PPC procesor(s) (e500 and 60x) and the measurement results are rather strange.
> I observed this with arbitrary version of Adeos/ipipe and on Xenomai 2.0.3 older 2.0.x too.
> 
> -sh-3.00# ./run -- -T 10 -h -l 5
> ...
> RTT|  00:00:01
> RTH|----klat min|----klat avg|----klat max| overrun|---klat best|--klat worst
> RTD|       -4525|       -4323|        5777|       0|       -4525|        5777
> RTD|       -4525|       -4444|       -1777|       0|       -4525|        5777
> RTD|       -4525|       -4444|        -565|       0|       -4525|        5777
> RTD|       -4525|       -4444|       -1656|       0|       -4525|        5777
> RTD|       -4525|       -4444|       -1979|       0|       -4525|        5777
> RTT|  00:00:06
> RTH|----klat min|----klat avg|----klat max| overrun|---klat best|--klat worst
> RTD|       -4525|       -4444|       -2020|       0|       -4525|        5777
> RTD|       -4525|       -4444|       -1050|       0|       -4525|        5777
> RTD|       -4525|       -4444|       -1616|       0|       -4525|        5777
> RTD|       -4525|       -4444|       -1898|       0|       -4525|        5777
> RTD|       -4525|       -4444|       -1939|       0|       -4525|        5777
> ...
> Well if I set scheduling latency from automatic "0" to "1" I get:

0 means automatic latency compensation (which does not seem to work that
well here, it overcompensates), while 1 effectively means "no
hardware/software scheduling latency" (=> 1 ns). See also help of the
related kernel configuration parameters.

> 
> -sh-3.00# ./run -- -T 10 -h -l 5
> 
> RTT|  00:00:01
> RTH|----klat min|----klat avg|----klat max| overrun|---klat best|--klat worst
> RTD|        4767|        4929|       15191|       0|        4767|       15191
> RTD|        4767|        4808|        8282|       0|        4767|       15191
> RTD|        4767|        4808|        8080|       0|        4767|       15191
> RTD|        4808|        4808|        7838|       0|        4767|       15191
> RTD|        4767|        4808|        7272|       0|        4767|       15191
> RTT|  00:00:06
> RTH|----klat min|----klat avg|----klat max| overrun|---klat best|--klat worst
> RTD|        4808|        4808|        7555|       0|        4767|       15191
> RTD|        4767|        4808|        7959|       0|        4767|       15191
> RTD|        4767|        4808|        7393|       0|        4767|       15191
> RTD|        4808|        4808|        7191|       0|        4767|       15191
> RTD|        4767|        4808|        7313|       0|        4767|       15191
> 
> Is this a bug or feature please? Can someone throw the light?
> Good would be to print the units to the numbers too (ns).
> 

That was likely a layout question of the latency tool's output. We could
simply dump something like "All latencies in nanoseconds" during
start-up. Would this be more helpful?

Jan