CODESYS - the IEC 61131-3 automation software

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 Post subject: Reducing Jitter
PostPosted: Tue Jul 09, 2019 7:02 pm 
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Joined: Sat Feb 17, 2007 5:06 pm
Posts: 29
I have been experimenting with reducing jitter on a Raspberry Pi with the Preempt RT patch. The one thing I found that seemed to help was to set the CodeSys process to a nice level of -20. My test is not very scientific, but enough to see results. I have a program with 5 tasks and they are all set to free floating processor core use. My before and after jitter results:

Before -> After
129 -> 95
157 -> 117
154 -> 66
102 -> 62
521 -> 147

So my question is whether changing the nice value could have other side effects?

This is the method I used to change the CodeSys nice value:

Connect using SSH
cd /etc/init.d
sudo nano codesyscontrol

insert the "--nicelevel -20" into the following line :

start-stop-daemon --start --background --make-pidfile --pidfile $PIDFILE --nicelevel -20 --chd$

reboot


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 Post subject: Re: Reducing Jitter
PostPosted: Fri Jul 12, 2019 8:35 am 
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Site Admin

Joined: Mon Sep 05, 2005 9:42 am
Posts: 3454
Hi,
which jitter do you see , before you start changing anything?

BR
Edwin


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 Post subject: Re: Reducing Jitter
PostPosted: Fri Jul 26, 2019 4:05 pm 
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Joined: Sat Feb 17, 2007 5:06 pm
Posts: 29
Edwin Schwellinger wrote:
Hi,
which jitter do you see , before you start changing anything?
These are the values before and after changes:
Before -> After
129 -> 95
157 -> 117
154 -> 66
102 -> 62
521 -> 147

This was only a short term test over a few hours so it may not be very accurate.


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