[linux-audio-user] Low latency kernel on Mandrake

Austin aacton at yorku.ca
Sun Nov 2 18:07:44 EST 2003

On Sun, 2003-11-02 at 11:40, Joe Button wrote:
> I thought that _ought_ to be the case but I was suspicious because of the 
> /proc/sys/kernel/lowlatency thing

Yeah, I dunno why Danny made it that way.  I think just to make sure
lowlat was enabled by default with that kernel.

> and also because I get very noticeable 
> audio dropouts when I do things like task-switch. jackd doesn't report xruns 
> though.

The #1 best thing you can do is mount /tmp as tmpfs.  See the jack
homepage.  It makes all the difference.  Also, if you are using KDE,
Mandrake has this stupid idea of renicing X to -10, which makes the mm
kernel very stop-and-go.  Adjust the -n level to 0 in
/etc/X11/xdm/Xservers.  If you're using gdm (as all sane people do), you
don't have to worry, X is not reniced by gdm.

> Am I correct in thinking that if I start jackd as root I don't need to use -R 
> or jackstart or anything to get good performance? At the moment I think I'm 
> using jackd -d alsa -d hw:0 -p 512 (although that's in a script on my other 
> PC so I might be mis-remembering).

With the mm kernel, you should install jack-realtime, and start jack as
a normal user with 'jackstart'.  That's part of the mm kernel's purpose.

Try using qjackctl too.  It lets you adjust all the jack parameters and
compare the performance.


                                 Austin Acton
        Synthetic Organic Chemist, Teaching Assistant, Ph.D. Candidate
               Department of Chemistry, York University, Toronto
        MandrakeLinux Volunteer Developer, homepage: www.groundstate.ca

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