Re: [Xenomai-help] gatekeeper/0

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

henning.richter@domain.hid wrote:
> 
> 
> henning.richter@domain.hid wrote:
>>> Hi,
>>>
>>> running a xenomai task in which I am sending a single Frame (size ~500
>>> byte) from my EtherCAT Master to some Beckhoff slaves has latencies
> around
>>> 200 us.
>>> While running that task, top shows that gatekeeper/0 (with RT priority)
> has
>>> 30% CPU usage.
>>> What is the task of this gatekeeper and can this cause my high
> latencies?
>> The gatekeeper is used when a taks is migrating from secondary mode to
>> primary mode. The gatekeeper itself can not cause the high latencies,
>> but the fact that a task runs in secondary mode can.
>>
>> To check if this is what happens, check the MSW column in
>> /proc/xenomai/stat for the thread which has latencies issues. If MSW is
>> increasing then you have a problem.
> 
>> To find where your thread switches to secondary mode, use the technique
>> demonstrated in examples/native/sigxcpu.c.
> 
> --
>                                                  Gilles.
> 
> So thank your for defining my problem.
> Now I am sure that there my thread is switching to secondary mode
> as the MSW column increases rapidly while running my application.
> Can I also use the ipipe tracer or LTTng to find the place where it
> switches the modes as I don't have the
> xenomai examples installed.

Yes, you can use the I-pipe tracer, but reading the output might be a
bit complicated. Examples are part of Xenomai sources freely available
on Xenomai web site.

-- 
                                                 Gilles.