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

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? Thank you, Julian