[Asterisk-Users] Re: X100P interrupt load

[Tom Samplonius]

On Tue, 22 Mar 2005 15:15:18 -0500, Jesse Guardiani <jesse at wingnet.net> wrote:

> > FreeBSD had some issues with Asterisk.
> 
> This should be "has some issues". I do not consider
> the FreeBSD zaptel support to be production quality
> in any way. I experienced reproducible system hangs
> (mostly after an asterisk restart), interrupt issues
> (audio skips and SSH pauses during typing), and
> general instability. This was with an up-to-date
> FreeBSD 5.3-SECURITY and the latest zaptel at
> asterisk from ports (1.0.6 for asterisk, and a
> significantly lower version for zaptel, I think).
> 
> I do not recommend anyone run FreeBSD + Asterisk at
> this time.

  I think if you don't use Zaptel cards, FreeBSD and Asterisk is fine.
 It sound like the interupt issues were definitely caused by the
Zaptel card.  I use Asterisk on FreeBSD 5.3-STABLE, and hasn't
crashed.  I'm annoyed by the bugs in 1.0.5 and 1.0.6 though, but I see
those should be addressed in 1.0.7.

> [...]
> 
> > Also, on 2.6.11 look at the "timer" in /proc/interrupts.  It's
> > 1000/second too.
> 
> Yeah, I saw that. How is that significant? I'm a software guy,
> not a hardware guy, so I don't know much about interrupts.
> Just that 1000 interrupts/sec is fairly high. :)
> 
...
> Again, is there a formula to describe how many interrupts per
> second a given CPU, PCI bus, and FSB bus can theoretically
> sustain per second?

  For a software guy, there is an easy solution:  count the number of
instructions in the interrupt handler, and then the number of cycle
required to execute those instructions.  Then factor in the context
switch overhead (which is really part of the interrupt handler).

> I'm curious if my 450mhz PIII should be able to handle 2 x100p
> cards, or just 1? What's the limit? Etc....

  That is probably a bit too much for such a CPU.  You might want to
invest in a 2 x FXO gateway.  That should reduce the interrupt load to
about 50 interrupts per second per active line (assuming one NIC
interupt per RTP packet).

> --
> Jesse Guardiani, Systems Administrator
> WingNET Internet Services,
> P.O. Box 2605 // Cleveland, TN 37320-2605
> 423-559-LINK (v)  423-559-5145 (f)
> http://www.wingnet.net

Tom