[Asterisk-Users] Re: Problems with TDM400P card

[Andrew Kohlsmith]

On May 5, 2005 11:13 am, Mike Mueller wrote:
> > Couple this with the fact that the driver now seems to pull 100% CPU
> > every 5 seconds or so and it didn't before and I think we have a good
> > case for there being something weird in the driver that is causing frame
> > slips or other weirdness that is generally not audible for most people
> > but wreaks havoc even for G3 or ECM (I think that's the term for
> > error-correcting fax) fax machines.
>
> As measured with top?

No; vmstat 1, without anything (not even asterisk) running.

Driver unloaded: no spiking.  Driver loaded: spiking.

> > Nah; we've been down this road.  I just need a block of time to pull
> > wctdm from about a year back and basically do a binary search until I
> > find where the driver started pulling this insane CPU use every 5 seconds
> > or so.
>
> diff 'em. It's much faster :).

Well yes, but I still need to check 'em out and see if it spikes.

> If you use an old driver revision then you can receive faxes? Can you
> use an old TDM driver in a new Asterisk rev?

Sure; you don't need Asterisk for this test anyway.

> What was that? No buffering? That means its tx/rx ISR should have priority
> over those servicing interfaces with buffering.  Is that happening?

It's one of the primary reasons these cards are *so* interrupt and system 
sensitive.

But remember; system didn't change, drivers did.  the problem was not there 
with earlier drivers and is now.   Therefore, since everything else has 
remained constant, the problem is with the drivers.

> Assuming there are a lot of samples from TDM missing - and that
> lack of buffering makes that plausible - this could be measured in a
> working system by dumping TDM input into a file over a 10 minute period
> as measured by gettimeofday and determining the amount of shrinkage that
> occurred.  Using a long time period like 10m will reduce the effects of
> Linux scheduler latency and it will ensure capture of the 5-second-100%-CPU
> effect.

Well I think we're missing frames because the driver is holding the system 
hostage for such a long amount of time every so often.  Steve's proposed a 
couple of tests for measuring this, we just need to get off our duffs and do 
it.  :-)

-A.