Dapper preemptive kernel and rtlimits February 20, 2006Posted by oktyabr in audio, debian, linux, realtime, ubuntu.
Discovered that the Dapper 6.04 “flight 3” kernels, including the one on the iso report the following:
#cat /boot/config-2.6.15-12-386 | grep PREEMPT
This is something that has been missing from the current “breezy” kernels and seems to suggest that Ubuntu will be offering a true preemptive kernel that should improve desktop latency for realtime apps like jackd and clients!
Abandoning “realtime-lsm” for “rtlimits”, which I first read about at Jonathan Woithe’s Home page has made configuring realtime access on a user/group level basis as well as per invidual application very easy and most importantly, FAST!
Refer to his page on “set_rtlimits” for a handly little app that works quite well to ease this process: http://tapas.affenbande.org/?page_id=22 *updated package at his home page*
This has allowed me to get much better performance than when using ‘realtime-lsm’ on a breezy kernel… 5.8ms in KDE and 2.9ms in a conservative fluxbox or even xfce4 enviroment under load with zero xruns and cpu-dsp usage (as reported by qjackctl and ardour) usually no higher than 10-11%!
Very nice! Ubuntu as a music creation enviroment. /me is in bliss