asterisk users - Feb 2007 - Linux Kernel Timer Frequency and Asterisk

Ok here is a real geek question,

I building my own linux kernel for my asterisk system and came across 
the kernel setting for the timer frequency.  I have one of 3 hardcode 
choices 100Hz, 250 Hz and 1000Hz.  From what I understand the default 
Freq was changed from 100Hz in kernel 2.4 to 1000Hz (1KHz) in kernel 
2.6.  Timing is a BIG issue in asterisk with all the TDM and zap channel 
stuff.  My guess is to go with the lower 100 or 250 Hz option but that 
is only a guess.  The 1KHz sounds like it will conflict with the Zap 
1khz timer (or am I wrong about that).  Does anyone know what the 
prefered settings are for Trixbox or AsteriskNOW (or the asterisk code 
forks e.g. OpenPBX)?  Please let me know what your experience has been.

Aloha,
Mark C
IS Director - Payroll Services Hawaii, Inc.
http://www.psh-inc.com
FWD: 293625

On Wed, 2007-02-07 at 14:53 -1000, Mark Coccimiglio
wrote:
> Ok here is a real geek question,
> 
> I building my own linux kernel for my asterisk system and came across 
> the kernel setting for the timer frequency.  I have one of 3 hardcode 
> choices 100Hz, 250 Hz and 1000Hz.  From what I understand the default 
> Freq was changed from 100Hz in kernel 2.4 to 1000Hz (1KHz) in kernel 
> 2.6.  Timing is a BIG issue in asterisk with all the TDM and zap channel 
> stuff.  My guess is to go with the lower 100 or 250 Hz option but that 
> is only a guess.  The 1KHz sounds like it will conflict with the Zap 
> 1khz timer (or am I wrong about that).  Does anyone know what the 
> prefered settings are for Trixbox or AsteriskNOW (or the asterisk code 
> forks e.g. OpenPBX)?  Please let me know what your experience has been.
Trixbox is based on CentOS4 which uses 1000Hz. Iirc the same goes for
FC6 with a recent kernel and the upcoming Fedora 7.

Regards,
Patrick

On Thu, Feb 08, 2007 at 02:15:15AM +0100, Patrick wrote:
> On Wed, 2007-02-07 at 14:53 -1000, Mark Coccimiglio wrote:
> > Ok here is a real geek question,
> > 
> > I building my own linux kernel for my asterisk system and came across 
> > the kernel setting for the timer frequency.  I have one of 3 hardcode 
> > choices 100Hz, 250 Hz and 1000Hz.  From what I understand the default 
> > Freq was changed from 100Hz in kernel 2.4 to 1000Hz (1KHz) in kernel 
> > 2.6.  Timing is a BIG issue in asterisk with all the TDM and zap
channel
> > stuff.  My guess is to go with the lower 100 or 250 Hz option but that
> > is only a guess.  The 1KHz sounds like it will conflict with the Zap 
> > 1khz timer (or am I wrong about that).  Does anyone know what the 
> > prefered settings are for Trixbox or AsteriskNOW (or the asterisk code
> > forks e.g. OpenPBX)?  Please let me know what your experience has
been.
> 
> Trixbox is based on CentOS4 which uses 1000Hz. Iirc the same goes for
> FC6 with a recent kernel and the upcoming Fedora 7.
Trixbox is based on RHEL, that uses kernel 2.6.9. The frequency speed is
configurable as of 2.6.13 .

Distributions tend to stick with the default of 250Hz, but this is not
necessarily ideal for Asterisk.

BTW: The default kernel of Debian Etch is non-preemptable, which is
centainly not a good idea for Asterisk.

-- 
               Tzafrir Cohen       
icq#16849755                    jabber:tzafrir@jabber.org
+972-50-7952406           mailto:tzafrir.cohen@xorcom.com       
http://www.xorcom.com  iax:guest@local.xorcom.com/tzafrir

On Wed, 7 Feb 2007, Mark Coccimiglio wrote:
> Ok here is a real geek question,
>
> I building my own linux kernel for my asterisk system and came across the 
> kernel setting for the timer frequency.  I have one of 3 hardcode choices 
> 100Hz, 250 Hz and 1000Hz.  From what I understand the default Freq was 
> changed from 100Hz in kernel 2.4 to 1000Hz (1KHz) in kernel 2.6.  Timing is
a
> BIG issue in asterisk with all the TDM and zap channel stuff.  My guess is
to
> go with the lower 100 or 250 Hz option but that is only a guess.  The 1KHz 
> sounds like it will conflict with the Zap 1khz timer (or am I wrong about 
> that).  Does anyone know what the prefered settings are for Trixbox or 
> AsteriskNOW (or the asterisk code forks e.g. OpenPBX)?  Please let me know 
> what your experience has been.
I always compile custom kernels and have been using 1KHz in all my systems 
which are for anything vaguely interactive.

Most of my asterisk systems are 1GHz processors but I have a small handful 
which are 533MHz and all are working just fine.

You're not using a recently kernel then ;-) 2.6.20 offers 300Hz too 
(supposedly good for video applications)

Gordon