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

27 May 2004

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(a)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/ 

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