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

[Robert Jonsson]

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

-- 
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