[linux-audio-user] Ardour, Jack, and 2.6 kernels

[mark62756 at comcast.net]

I actually get very very well latency in the 2.6.3-rc3 kernel... its the only 2.6 kernel i have used so far... and on the 2.4.23 kernel that is patched with low-latency has xrun saying 400+-  ms which is crazy... and ll is turned on for sure... for 2.6 the highest i get is around 20 ms. but i am also running fluxbox which uses  very little cpu.. my machine is a intel celron 533MHz with 256mb RAM with gentoo installed :)

--
Marko Dimiskovski


> Hi,
> 
> torsdagen den 27 maj 2004 19.16 skrev cv223 at comcast.net:
> > So, based on Fernando's and Malcolm's advice, I decided to quit fussing
> > with the 2.6 kernels and stick with the 2.4.23 that I have working to do
> > some recording last night.  The band came over - we were set and ready to
> > go.  I hit 'record' to get an idea of the drum mix (we're submixing to
> > stereo) - 3 seconds in, Ardour stops with an 80ms xrun!  Arrgh!  I sweated
> > through the rest of the evening, fearing another occurence at 3:30 into a
> > 4:00 song.  Fortunately, everything went ok.
> >
> > I guess I'm back to trying to figure out what's causing these long xruns,
> > now under the 2.4.23 kernel.
> >
> > Do most people shut off non-essential daemons during recording sessions, or
> > do any other tricks?  This is kinda frustrating, as the CPU load seems
> > rather low (< 15% when the xrun happened).  I guess I'll test out reiserfs
> > and even ext2 to see if the filesystem is the culprit.
> 
> I actually run fullblown KDE most of the time, it works pretty well at 512x2, 
> I can run 256x2 but xruns get more frequent, but not unbearably so. I'm 
> mainly running MusE and I seldom get kicked out, but it does happen...
> 
> There has been talk on the Jack list from time to time about adding a mode 
> where you won't get kicked out so easily even if Jack misses a beat. 
> For developing jack I think the current approach is good, the audio equivalent 
> of an assert, but for real usage it is a little hard on the user. Especially 
> if you are doing a performance, then it's devastating.
> 
> To return to the subject, I hear others use lightweight window managers and do 
> stop all unnesesary services to get better stability, if you have problems it 
> will probably help.
> 
> /Robert
> 
> >
> > Thanks for reading the ramble,
> >
> > Joel
> >
> > > > I guess my main motivation for trying out the 2.6 kernel is laziness.
> > > > Just build the kernel and get the performance and ALSA without patches
> > > > or compiling extra stuff.  At least, that was _supposed_ to be the way
> > > > it worked!  I'll keep trying the new kernels, but keep the old faithful
> > > > 2.4 kernel around for recording.
> > > >
> > > > I'm _still_ curious about what causes the long xruns, though.
> > >
> > > New versions of alsa can be compiled with the "--debug=full" option (I
> > > don't think the current code in the kernel has that). That will enable
> > > you to tweak a proc variable to dump the kernel stack on each xrun, it
> > > is something like /proc/asound/card0/pcm0p/xrun_debug (for playback,
> > > same for recording in pcm0c). "echo "2">/proc/.../xrun_debug" will turn
> > > reporting on. You will get the stack traces in /var/log/messages.
> > >
> > > Not that you will immediately know exactly what has to be done to get it
> > > fixed, of course :-)
> > >
> > > IMHO stick with 2.4.x, in my tests 2.6.x is not even close to being
> > > ready for pro audio work. It will get better but it will take some time.
> > >
> > > -- Fernando
> 
> -- 
> http://spamatica.se/music/