Messages in this thread | | | Date | Sat, 20 Nov 2004 21:40:35 +0100 | From | Florian Schmidt <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm2-V0.7.29-0 |
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On Sat, 20 Nov 2004 20:11:55 +0100 Florian Schmidt <mista.tapas@gmx.net> wrote:
> 29-4 with PREEMPT works very good (jackd at 64 frames: 0 xruns (running for > 1h now), soundcard irq unthreaded). Opposed to 29-1 PREEMPT_REALTIME which > showed some very weird jackd behaviour (xruns from 10usec to 50msec [!!!]). > rtc_wakeup was showing no large jitter for that kernel though, nor did the > different traces show anything that might have caused the jackd xruns. And > yes, i configured the irq handlers sanely :) > > Will build 29-4 PREEMPT_REALTIME now and see how this one behaves.
Pretty much as bad as 29-1. Sadly i have no idea on how to find out what is causing jackd to act so weird under a PREEMPT_REALTIME kernel. It seems there is some correlation to activity on X. Hiding and showing windows has a certain chance of triggering a large xrun.
Hmm, the max jitter rtc_wakeup shows at 1024hz is around 150us. Which seems a tiny bit large, too, as the rtc histogram shows a max wakeup latency of 16us..
It seems it's not the threaded irq handlers as jackd peformed quite well under 29-4 PREEMPT with the soundcrd irq handler threaded and at high prio (which i forgot to mention in my previous mail).
So i don't really know how to go about this. I suppose i just run PREEMPT kernels instead of PREEMPT_REALTIME. Maybe it's the overhead which is killing jackd performance with PREEMPT_REALTIME, but i don't believe so (50ms? nah!).
flo
P.S.: There's so many variables in this PREEMPT/PREEMPT_REALTIME, handlers threaded/unthreaded. IRQ handler thread priorities. It would probably be cool if we could create some testing procedure which produces results which are comparable. Ideally this procedure would be automated. Any takers? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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