[linux-audio-user] Re: Realtime not working on Debian testing... why?

[David Causse]

On Tue, Nov 14, 2006 at 07:08:11PM +0100, Julian Hagenauer wrote:
> Hi,
> i am using Debian testing with libpam-modules 0.79-4.
> I added 
> @audio		 -	 rtprio		 99
> @audio		 -	 nice		 -10
> @audio		 -	 memlock	 250000
> to /etc/security/limits.conf and i am member of the audio-group.
> If i start jack with 'jackd -R -d alsa' it says:
> jackd 0.101.1
> Copyright 2001-2005 Paul Davis and others.
> jackd comes with ABSOLUTELY NO WARRANTY
> This is free software, and you are welcome to redistribute it
> under certain conditions; see the file COPYING for details
> 
> JACK compiled with System V SHM support.
> loading driver ..
> creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
> control device hw:0
> configuring for 48000Hz, period = 1024 frames, buffer = 2 periods
> nperiods = 2 for capture
> nperiods = 2 for playback
> 
> As you see there no warning about missing realtime-cappabilities, anyhow realtime seems not work, because i got a lot of xruns....
> What i am missing?
> Do i need other requirements to fullfill to get realtime to work, e.g. special kernel-configuration?

Debian testing current libpam-modules 0.79-4 supports rtprio (I use it).
To be sure just run :

jackd -R -P 70 -d dummy

in another shell launch :

top -H -p `pidof jackd`

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND           
26812 moino     18   0 21652  21m 3892 S    0  2.1   0:00.01 jackd              
26813 moino     18   0 21652  21m 3892 S    0  2.1   0:00.00 jackd              
26814 moino     19   0 21652  21m 3892 S    0  2.1   0:00.00 jackd              
26815 moino    -81   0 21652  21m 3892 S    0  2.1   0:00.00 jackd              
26816 moino    *-71*   0 21652  21m 3892 S    0  2.1   0:00.00 jackd              

If rlimit is not working you won't see a thread at prio -71
Don't be afraid if you don't have the thread at -81 you must have an
old version of jackd.

If you can verify this you can be sure your problem does not come from
rlimit or realtime stuff.
You will have to investigate more.

Goood luck.

PS. If you have a dual core setup I'm not sure your jackd version is patched
against some hw clock drift problems. Do you have the --clocksource
option when you launch jackd -h ?

David.