[PD] Pd-extended + Ubuntu Gutsy generic kernel versus rt kernel

Jerome Tuncer columbiatwo at free.fr
Tue Dec 25 11:46:13 CET 2007

Hi Daniel,

Interesting point here. Do you mean you edited the 
/etc/security/limits.conf even when running the non rt kernel and that 
it made things better than with the non-edited /etc/security/limits.conf ?

That's definitely one thing I must try then...

To get even more off-topic (even though I'm not really convenced it is) 
I noticed as well that rt kernels are really aggressive. For instance 
when I just play mp3s through jack with the hdsp driver it eats all 
performance for the rest of desktop apps which then get really really 
sluggish (on a PIV 3000MHz...).


Daniel Wilcox a écrit :
> To all those Pd Ubuntu-ers out there,
> I have been using the realtime (lowlatency) kernel for a while, back 
> since Feisty, and compiled my own in Dapper.
> I have noticed that, at least with Gusty, the generic kernel works 
> better then the rt kernel, giving me much *fewer*? xruns
> and artifacting with Pd ... while using the rt kernel,  Pd seems to 
> "sput" xruns while using Jack.  It's important to note that I
> did enable the realtime privledges by writing to the security config as 
> noted on the Ubuntu studio page:
>      sudo su -c 'echo @audio - rtprio 99 >> /etc/security/limits.conf'
>      sudo su -c 'echo @audio - memlock 250000 >> /etc/security/limits.conf'
>      sudo su -c 'echo @audio - nice -10 >> /etc/security/limits.conf'
> Could it be that the preemption enabled in the rt kernel is a bit *too* 
> aggressive?  Realtime audio in PD with Jack seems to run much
> better with the generic kernel!  Even at a 8ms latency ... in fact I'm 
> testing the same on my slow performance computer (PIII 500MHz) with a 
> fresh install of a Minimal command line Gutsy and it works *soooo* much 
> better then the realtime kernel.  (Plus suspend and
> hibernation work, while they don't using the realtime kernel.)
> -- 
> Dan Wilcox
> danomatika
> www.robotcowboy.com <http://www.robotcowboy.com>
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