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Date: Wed, 08 Apr 2009 21:16:30 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-help] Excess getpid calls??
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To: John Wojnaroski <castle@domain.hid>
Cc: xenomai@xenomai.org

John Wojnaroski wrote:
> Hi
> 
> We're running several apps with scheduled realtime task using 
> rt_task_spawn() in a flight simulator.  There are two apps each for a 
> pilot and copilot and each app has 8 periodic tasks running at various 
> duty cycles from 1Hz to 50Hz.
> 
> A concern was raised as to whether the calls to getpid() were 
> excessive.  See trace ouput below....
> 
> <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> 
> [1006]$ ps augx | grep -i copilot
> root      3561 24.7  5.6  51936 58108 ?        RLl  Apr01 2455:02 
> Source/Main/copilot --file=glass.cfg --window=0 0 2400 1050
> hcsl     20859  0.0  0.0   1820   532 pts/4    S+   09:55   0:00 grep -i 
> copilot
> (09:55) <hcsl on spire>: ~
> [1007]$ sudo !!
> sudo strace -p 3561 -c
> Process 3561 attached - interrupt to quit
> Process 3561 detached
> % time     seconds  usecs/call     calls    errors syscall
> ------ ----------- ----------- --------- --------- ----------------
> 92.78    0.179969           2     90067           getpid
> 5.67    0.010999           5      2247           ioctl
> 1.55    0.003000           1      2247           gettimeofday
> 0.00    0.000000           0         9           poll
> ------ ----------- ----------- --------- --------- ----------------
> 100.00    0.193968                 94570           total
> 
>  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> 
> We have not bored down into the xenomai source to see exactly what is 
> going on or where or how the calls are made as we've been quite happy 
> with the performance and stability.
> 
> Might someone shed a bit of light on the matter and should we be concerned?

strace will not work correctly with Xenomai. I am even surprised that it
does not exit with an error. The reason being that strace does not know
anything about xenomai syscalls. Maybe unrecognized syscalls are counted
as getpid calls ?

-- 
					    Gilles.