[Asterisk-Users] CPU spikes with wcfxs loaded

[Rich Adamson]

> 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?

I see about the same thing with RHv9, single tdm04b (no fxs) rev e/f,
2.2ghz celery, and zero calls being processed. The spikes to not 
correspond with anything observable with a packet sniffer.