Messages in this thread | | | Date | Mon, 1 Nov 2004 15:30:49 +0100 | From | Ingo Molnar <> | Subject | Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4] |
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* Paul Davis <paul@linuxaudiosystems.com> wrote:
> > > >* Florian Schmidt <mista.tapas@gmx.net> wrote: > > > >> new max. jitter: 4.3% (41 usec) > >> new max. jitter: 4.9% (47 usec) > > > >a couple of conceptual questions: why does rtc_wakeup poll() on > >/dev/rtc? Shouldnt a read() be enough? > > i suggested to florian that it should model jackd's behaviour as > closely as possible. because jackd requires duplex operation, using > just read/write doesn't work.
ok - but i think there should at least be an option to turn the poll()-ing off. To showcase the best-possible wakeup latency offered by the kernel :-)
poll() is quite complex and with a good number of locks in the path the maximum latency increases accordingly.
btw., couldnt jackd use a separate input and output thread (of identical priority), to be purely read()/write() based? This method should also solve the priority problems of poll(): the thread woken up later will do the work later. (hence the _earlier_ interrupt source will be handled first.) With poll() how do you tell which fd needs attention first, if both are set?
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