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Old 08-13-06, 10:46 PM   #23
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Join Date: Jul 2006
Posts: 14
Default Re: Crashing when SMP enabled

Originally Posted by JaXXoN
This typically means that the High Resolution Timer support (HRT)
is not enabled (kernel configuration option).
Enabling this seems to have had no effect, the 'Max' figure is at zero for about 50 iterations then rapidly increases.

Originally Posted by JaXXoN
BTW.: can you please check if jackd is actually working at real
time priority?
Oh thanks, I've been trying to find a tool like 'rtnice'. I've applied the necessary patches to PAM in order for users in the 'audio' group to gain realtime priority, but until now had no way to be sure they were working.

Originally Posted by JaXXoN
Then do something like "rtnice -p `pidof jackd`".
Running that command line did initially tell me jackd was using the TS scheduler, but, I examined '/proc/`pidof jackd`/task/' and there are in fact five 'jackd' threads. Three are TS but there are also two realtime threads (one for the actual processing, and the other is a watchdog I believe).

I've done a little JACK programming recently and believe all apps using JACK I/O make use of callback, whereby 'jackd' will run the audio processing parts of your app. in a realtime thread. So the apps 'feeding' JACK don't have to be told to run in realtime. I was able to verify this by looking at XMMS's threads, and one of them (presumably the callback function for JACK) was running with realtime priority.

I'm happy to say that I'm free of any xruns so far on 2.6.16-rt29, and the 'nvidia' driver isn't giving me any of the hassle I had with earlier kernels. My problems with 2.6.17 are I think largely caused by bugs in the -rt patches, which still seem present in the latest -rt8 patch. I can hopefully do as Lonni suggested and get serial logging to work; this would allow me to report the -rt bugs to LKML or wherever is appropriate.

Also the realtime patch for the 'nvidia' driver appears to be doing the job perfectly. Thanks for pointing that out, because I really hadn't thought such a thing would exist.

As long as this kernel remains stable, it seems I'm finally back to a working system. I really appreciate everyone's help getting this to work. Thanks!
Steven Chamberlain
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