JACK audio in realtime mode ... not working :o(

dreamtheater · 11-27-2005, 05:20 AM

Hello!

I've installed kernel-multimedia-2.6.12-12.mm.1mdk for Mandriva 2006. The realtime module is loaded with 'dmesg | grep -i realtime' yielding:

Realtime LSM initialized (all groups, mlock=1)

When I try to start JACK audio server in realtime mode (via qjackctl) it tells me:

cannot lock down memory for RT thread (cannot allocate memory)
cannot use real-time scheduling (FIFO at priority 9) [for thread -1223894096, from thread -1223894096] (operation not permitted)

[cannot lock down memory for RT thread (Nicht genügend Hauptspeicher verfügbar)
cannot use real-time scheduling (FIFO at priority 9) [for thread -1223894096, from thread -1223894096] (1: Die Operation ist nicht erlaubt)] (same message as above, german)

So jack won't run in realtime mode and I always get xruns. How can I fix this problem?

Thanks in advance!

tkedwards · 11-27-2005, 09:52 PM

Does this help: http://music.columbia.edu/pipermail/...er/017889.html

Are you sure the module loads properly - do

Code:

/sbin/lsmod | grep -i real

after you've loaded it

Have you tried running it as root?

dreamtheater · 11-28-2005, 11:13 AM

Runnin JACK in realtime as root works. But that's not very comfortable...

darc26 · 12-07-2005, 12:56 PM

Quote:

Originally Posted by dreamtheater

Hello!

I've installed kernel-multimedia-2.6.12-12.mm.1mdk for Mandriva 2006. The realtime module is loaded with 'dmesg | grep -i realtime' yielding:

Realtime LSM initialized (all groups, mlock=1)

When I try to start JACK audio server in realtime mode (via qjackctl) it tells me:

cannot lock down memory for RT thread (cannot allocate memory)
cannot use real-time scheduling (FIFO at priority 9) [for thread -1223894096, from thread -1223894096] (operation not permitted)

[cannot lock down memory for RT thread (Nicht genügend Hauptspeicher verfügbar)
cannot use real-time scheduling (FIFO at priority 9) [for thread -1223894096, from thread -1223894096] (1: Die Operation ist nicht erlaubt)] (same message as above, german)

So jack won't run in realtime mode and I always get xruns. How can I fix this problem?

Thanks in advance!

You need to do 2 things. Both of them need to be done as root.
1. Using the User Manager add your user to the "audio" group. You do this by selecting your user - edit - groups - put a check mark in the box for audio.
2. You need to edit the file /etc/limits.conf => there will be a line that says
@audio - realtime priority 50 ( or something like that)
you need to change that 50 to something like 80 or 100 (100 is the max)
You then need to add this line in that same file:
@audio - memlock xxxxx ( x is a number ) a good rule of thumb is to make that number equal to half your ram. So if you have a Gig of ram - that number would be 512000

Then just log out of your user account... log back in... and you should be good to go. Let me know if it works.

dreamtheater · 12-10-2005, 05:02 AM

Hello again!

All I can say is: I followed your instructions and they worked!

So in Mandriva 2006 it's 3 easy steps to get jack working in realtime mode:

1. Install the multimedia kernel from the contrib packages.

Code:

urpmi kernel-multimedia-2.6.12-12.mm.1mdk

2. Configure the realtime module

In /etc/modprobe.conf I commented out capability and added realtime like that:

Code:

# capability

realtime mlock=1 gid=81

Where gid=81 corresponds to the group id of the audio group (according to /etc/group) which I added myself to via drakuser. I could also have substituted gid=81 for any=1 which would have granted any user realtime privileges.

3. Modify limits.conf

In Mandriva 2006 limits.conf is located in /etc/security/

I've got 512MB RAM so I edited the appropriate section to read:

Code:

@audio          -       rt_priority     80
@audio          -       nice            -10

@audio          -       memlock         256000

After booting the new kernel, qjackctl should be able to start jack in realtime mode.