[Musix-users] Do I run a low-latency and realtime kernel?

[Marcos Guglielmetti]

El Lun 09 Abr 2007 12:54, julien bodd escribió:
 | Hi all,
 |
 | I'm experiencing tons of xruns and sound saturation when I use
 | zynAddSubFx in combination with freewheeling (live looper).
 |
 | I went through the linux-audio-users-request mailing list and I saw
 | that a low-latency kernel is not the same with a realtime kernel.
 |
 | When I do : uname - a, I have :
 | ... 2.6.16-beyond4.1 #1 PREEMPT Sun May 28 ...
 |
 | So my kernel is low-latency? But, it doesn't seem it is realtime as I
 | have installed no patch (Ingo Molnar patch). It doesn't seem to be
 | PREEMPT_RT. Or is it included in Musix by default?
 |
 | This might be the problem.
 
I dont think it could be, but, in that case, you can start Musix using the 
64studio kernel that comes with it...

cat /boot/config-2.6.17-2-multimedia-486 | grep -i realtime
CONFIG_SECURITY_REALTIME=m
marcos at musix099b16:~$ cat /boot/config-2.6.16-beyond4.1 | grep -i realtime
CONFIG_SECURITY_REALTIME=m


Also, I suggest to try the new kernel:

linux-image-2.6.21-rc4

apt-get update

apt-get install linux-image-2.6.21-rc4

 | Another thing I see is that when I run QJackCtl, it doesn't seem to
 | run realtime!

Why it does not seems?

To try it, start jack and type into a konsole:

ps -C jackd -cmL

You must see something like this:

ps -C jackd -cmL
  PID   LWP CLS PRI TTY          TIME CMD
11213     - -     - ?        00:00:00 jackd
    - 11213 TS   19 -        00:00:00 -
    - 11218 TS   20 -        00:00:00 -
    - 11219 TS   24 -        00:00:00 -
    - 11222 FF   90 -        00:00:00 -
    - 11223 FF   80 -        00:00:00 -


If there are no FF, it's not in realtime, also, Musix 0.99 tells you if you 
are not using a realtime kernel or JACK was not started in realtime...

 cat ~/.jackdrc
jackd -R -P40 -p128 -t2000 -m -dalsa -dhw:0 -r48000 -p128 -n2 -s -S

That "-R" is from realtime

 | Although it does not complain and I have activated the R (realtime)
 | switch. I can see it is not realtime because there is a RT indicator
 | that is not yellow.
 | I tried running as root, and it is the same.
 
Well, that's weird, mmm


	Is realtime-lsm installed and loaded?

lsmod | grep realtime


 | I have libpam-modules installed (0.79-4) and I added :
 | /etc/security/limits.conf
 | @audio		 -	 rtprio		 99
 | @audio		 -	 nice		 -10
 | @audio		 -	 memlock	 250000
 |
 | (I belong to the audio group of course)
 |
 | (I also tried some optimizations with fluxbox, no 3D accel, disable
 | unnecessary services, increase  pci latency for soundcard..)
 |
 | So, I is the problem the lack of realtime patch, or a bad version of
 | QJackCtl?

Mmmm... the realtime patch is into Musix, in both kernels.

If you have no luck with 2.6.16-x, try to install any of these:

linux-image-2.6.21-rc3 - Linux kernel binary image for version 2.6.21-rc3
linux-image-2.6.21-rc4 - Linux kernel binary image for version 2.6.21-rc4

They dont need realtime-lsm to work fine

Those kernels just needs this lines into: /etc/security/limits.conf  

# there is no way to say "allow locking all memory", 4G should be enough
#
* - rt_priority 0
* - nice 0
#
@audio - rtprio 99
@audio - memlock 250000
@audio - nice -10


 |
 | Thank you very much, and sorry for this long post !
 
It is a pleasure if I could help you, man!

 | Julien
 |
 | _______________________________________________
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 | Musix-users mailing list
 | Musix-users at lists.ourproject.org
 | https://lists.ourproject.org/cgi-bin/mailman/listinfo/musix-users

-- 
Marcos Guglielmetti  
* Director del desarrollo de Musix GNU+Linux, 100% Software Libre
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