Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]

[Ingo Molnar <mingo@elte.hu>]

* Paul Davis <paul@linuxaudiosystems.com> wrote:

> >my main suspicion is that either the main jackd thread itself calls the
> >kernel where the kernel (unexpectedly for jackd) schedules away for
> >whatever reason, or that the chain of wakeup in the audio path somehow
> >gets violated (i.e. a kernel problem). There's one quick thing we could
> 
> the "max delay" measurement isn't a reflection of the runtime activity
> of jackd. its simply a measurement of the delay between when jackd
> expected to be next woken from poll and when it actually was.
> 
> as you noted, jackd generally goes back to sleep in poll typically a
> long time before the next interrupt is expected. hence any delay in
> the wakeup is between the interrupt handler and the scheduler getting
> jackd's main thread back on the processor. i think.

this brings up the next question: does the jackd measurement also
timestamp the time when it calls poll() - hence detecting in-jackd
processing delays? If yes, which value is this from Rui's stats? If not
then it might make sense to add it.

	Ingo