[LAU] Re: Installing realtime kernel - getting it to work.

[Ismael Valladolid Torres]

Brad Fuller escribe:
> >well.. I was just following the directions - I haven't done a
> >realtime kernel on gentoo and am using/trying the proaudio overlay.

It's "preemptive kernel" and "realtime" which are different
stuff. AFAIK you can try going realtime without a preemptive kernel
(this is, a kernel without Ingo Molnar patches).

Going preemptive: Download a vanilla kernel sources, version according
to latest available Ingo Molnar patches. Apply patches, recompile,
install, reboot.

[1]This article explains nicely what preemption is all about.

1. http://lwn.net/Articles/146861/

If running a debianized distro things are far easier, simply download
a [2]Musix kernel or a [3]64 Studio kernel (I'm right now running
Debian sid with a Musix 2.6.20 kernel and everything's smooth).

2. http://linux.ilmainen.net/musix/
3. http://archive.64studio.com/64studio/testing/pool/main/l/linux-2.6/

Talking about realtime, the newest the kernel the better although
other things break.

Going realtime is a matter of running a fairly recent version of
libpam-modules (higher than 0.79 I think), making sure the user is a
member of the audio group, putting this stanza into
/etc/security/limits.conf and relogging.

# limit realtime and memory locking access to users in the group audio
# there is no way to say "allow locking all memory", 4G should be enough
#
* - rt_priority 0
* - nice 0
#
@audio - rtprio 99
@audio - memlock 250000
@audio - nice -10

You should then be able to run jackd realtime.

:  [ ~ ] $; jackd -R -d alsa

Also it should be useful enabling the high resolution timer in your
/etc/sysctl.conf as this:

dev.rtc.max-user-freq=1024

And then sysctl -p as root.

Hope I haven't mistaked anything and info is useful.

Cordially, Ismael
-- 
Ismael Valladolid Torres  m. +34679156321
La media hostia           j. ivalladt at gmail.com

http://lamediahostia.blogspot.com/
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