[PD] benefits of planet ccrma kernel, and realtime priority pd?

julien.breval at tremplin-utc.net julien.breval at tremplin-utc.net
Wed Apr 27 13:22:21 CEST 2005

Hello Mike,

> Has anyone ever published performance results/benchmarks when using the 
> Planet CCRMA kernel vs. a regular RedHat/Fedora kernel? Where can I find 
> them?

I have used the planet ccrma low latency kernel (2.4) for over one year, with
the red hat 9 distribution that I downloaded from the ccrma web site. It works
very well with my PC (old 2.4 GHz shuttle with a rme hdsp multiface sound card).
Most of the time I use 64 or 128 smp hardware buffer size. It's difficult to
know about the real latency between the input and the output (it depends on the
software you are using anyway) but with pd I don't notice any latency so it
should be less than 10 ms. Jack prints a latency of 2.9 ms (buffer = 64 smp) or
5.38 ms (128). I don't get any xruns, except sometimes when the GUI of the
softwares are being loaded (or after using ardour for 7 minutes, still a mystery)
> ...or how about the benefit of using the -rt (realtime) option in Pd? I 
> don't seem to notice a difference.

on my computer, it's almost mandatory to use -rt, else I get lots of xruns;
also, I never managed to use pd with alsa only (so I use "jackd -R -d alsa -p
128" and "pd -jack -rt", both as root)

with pd, when the cpu is very high (over 80 %), I get periodic clics at 64 or
128 smp, in this case I have to use a larger buffer size (I don't need to do
this because I prefer working with < 50% cpu anyway)

> Is it worth it for me to install *just* the Planet CCRMA kernel for 
> RedHat 9? ...note that I can't really install anything else since I'm on 
> a networked machine with many restrictions. Will I get much improvement 
> from just the kernel alone?

I don't understand what you want to install more for improving performance
(besides better hardware) -- what am I missing ?


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