[asterisk-users] DAHDI - Tickless Kernel?

[Shaun Ruffell]

On Thu, Jul 25, 2013 at 03:52:49PM -0500, Tim Nelson wrote:
> Greetings-
> 
> I'm running some USB DAHDI hardware on a system with a tickless
> kernel. The audio quality is quite poor. Could the tickless kernel
> be to blame? If so, when recompiling a kernel that is *not*
> tickless, is there a recommended KERNEL_HZ value? IIRC, older
> kernels used to be 1000, but newer ones are 250.

I doubt it's the tickless kernel that is causing your issue.
Normally if you have DAHDI hardware, then it should be generating
interrupts which drive the mixing / passing of audio. There
shouldn't be any reliance on the system timer tick.

Also, for most Asterisk installations that are using the system
timer for mixing I've not seen any problems with 250 HZ. Most VOIP
systems mix audio at in at least 20ms size packets, so even at 250
HZ there are 5 timer expirations for each audio packet. Keeping the
kernel tickless should also work fine here when using a software
timer to mix your audio since the kernel will set the timer to fire
at the next timer expiration (whatever that was set to).

So, in summary...I've not seen any problems related to the tickless
kernel.

-- 
Shaun Ruffell
Digium, Inc. | Linux Kernel Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: www.digium.com & www.asterisk.org