[asterisk-users] Recommendations for kernel config

[Patrick]

On Fri, 2007-10-05 at 12:26 -0400, Matthew J. Roth wrote:
> Alan Lord wrote:
> > I'm building a test asterisk server and building the latest kernel I got 
> > to wonder if there are any specific recommendations about schedulers and 
> > so forth for optimum performance.
> >
> > There are a few areas that raise questions in my mind and I wonder if 
> > anyone has any opinions/comments on which settings are most suitable for 
> > use with asterisk:
> >
> > SLAB Allocator (SLAB or SLUB?)
> > Tickless System (?)
> > Preemption model (?)
> > IO Scheduler (Anticipatory, Deadline or CFQ?)
> > Flat or Sparse Memory (?)
> > Timer Frequency (100Hz .. 1000hz)
> >   
> Alan,
> 
> Good post!  I've wondered about the preemption model and I/O scheduler 
> myself, so I'll be keeping an eye on this thread.  As the Linux kernel 
> evolves to allow configuration as a fully deterministic real-time OS, it 
> will be interesting to see what settings provide the optimal environment 
> for Asterisk.
> 
> As for my contribution to the thread, I have a few tips for configuring 
> the kernel if you plan on using ztdummy for timing:
> 
>   1. The kernel version must be at least 2.6.13
>   2. The kernel must be configured with a timer frequency of 1000 HZ
>   3. The kernel must be configured to provide RTC interrupts

No kernel expert here but I don't think that RTC support is necessary if
you have a recent kernel with high resolution timer support. There is
support in the 1.2 svn tree for these high res timers. I tried them on
an updated Fedora 7 box and the zttest results were better than when
using the RTC stuff.

>   4. The kernel must be configured with enhanced real time clock support

See previous remark :)

> Remember to use zttest to verify the accuracy of your timing source.  
> The goal is to obtain at least 99.98% output from zttest

On the Fedora 7 box with high res timers the output of zttest shows 100%
many times while with RTC I have never seen 100% but usually something
between 99,97% and 99,98%. All I can say is try it and see for yourself.

Regards,
Patrick