Re: [Xenomai-help] test result on at91rm9200

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

robert165 wrote:
> 
> 
> 
> 在2009-12-29，"Gilles Chanteperdrix" <gilles.chanteperdrix@domain.hid> 写道：
>>robert165 wrote:
>>> 
>>> 
>>> 
>>> 在2009-12-28，"Gilles Chanteperdrix" <gilles.chanteperdrix@domain.hid> 写道：
>>>>robert165 wrote:
>>>>> Hi,
>>>>> I have tested xenomai on my at91rm9200 board, I used
>>>>> xenomai 2.4.10 + linux-2.6.28 + adeos-ipipe-2.6.28-arm-1.12-05.patch
>>>>> Test result seems very poor, is that correct?
>>>>
>>>>Your test results are rather good for an at91rm9200 board, which is the
>>>>sure sign that you are not loading the system enough.
>>>>
>>>>As I already told, you, the expected results are:
>>>>- user-space latency of 260us without FCSE
>>>>- user-space latency of 200us with FCSE
>>>>- kernel-space latency of 50us if running with unlocked context switches
>>>>(an option which is only available in the upcoming 2.5 branch).
>>>>
>>>>> And is there any introduction of the tests, as their purper, their
>>>>> meanling...
>>>>
>>>>The latency test computes some latencies (either user-space scheduling
>>>>latency, kernel-space scheduling latency, or kernel-space interrupt
>>>>latency, depending on the options). The switchtest tests context
>>>>switches. The switchbench measures context switching time. cyclictest
>>>>does the same thing as the latency test (only, you need to run it with
>>>>the right options to avoid running in fact with Linux timer), and in
>>>>general return similar results. Here I do not know what is the meaning
>>>>of cyclictest results you got, but if you want to know, I am afraid you
>>>>wil have to investigate, or simply ignore them.
>>>>
>>> 
>>> Thanks for your introdution, and is there any document of it. 
>>> The man pages just explain  parametres  of test scripts.  I could
>>> not understand the output of some test.
>>
>>No there is no document. But patches are welcome, as usual. As far as I
>>can tell, I explained you what the tests do, there is not much more to
>>tell. Which test's output did you not understand?
>>
> 
> when running: ./run -- -p 1000 -T 180 -t2 # latency
> result gave negative numbers like 
> RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat worst
> RTD|      -3.739|      11.330|      39.530|       0|      -3.739|      39.530
> Is that means timer interrupts are not perfect, and may occur before or after the exact moment.
> If so, the avg should calculate by the absolute value of the latency, and the best should be 
> the least absolute value.

It is a matter of point of view. From our point of view, the timer
interrupt ticking in advance is a feature, it compensates a bit for the
latency. Anyway, if you do not like it, just
echo 0 > /proc/xenomai/latency

The timer interrupts happen at the time they are programmed, only it is
their handling which may be delayed, most probably due to interrupts
masking sections.

-- 
					    Gilles.