[Asterisk-Users] CPU spikes with wcfxs loaded

[Michael Welter]

I need to reopen this discussion because it's impossible to run spandsp 
(and VoIP) under these circumstances.

With zaptel unloaded, I see the following "vmstat 1" output:

no swapping, an occasional disk output, +/- 1003 interrupts/sec., less 
than 10 context switches/sec., CPU idle 100%.  A very quiet system.

I load modules zaptel and wcfxo, and the system utilization stays the 
same.  When I load wcfxs, the number of interrupts goes up to +-2004, 
which is normal.  However, every three seconds the CPU spikes to 50%. 
This is "system" utilization, not userland.  I assume it's in a wcfxs 
interrupt.

The number of interrupts stays constant at about 2004 during each spike, 
leading me to the conclusion that the TDM card is holding an interrupt 
for 500ms every three seconds (50% of 1000ms is 500ms).  This is a 
disaster for spandsp and VoIP in general.

When I unload the wcfxs module, CPU idle goes back to a constant 100%.

The TDM22B card is REV E/F, and I've tried it with several different 
cards.  Fedora Core 3 with linux-2.6.9 downloaded from kernel.org (a 
stock kernel).  The CPU is Athlon K7.

Can anyone please give me a clue?

Thanks,

-- 
Michael Welter
Introspect Telephony Corp.
Denver, Colorado US
+1.303.674.2575
mike at introspect.com
www.introspect.com