On Sun, 16 Jan 2005 17:15:13 -0500 Eric Dantan Rzewnicki <eric@xxxxxxxxxx> wrote: > I set my IRQ handlers' priorities like this: > p=99 ; for i in 1 9 11 8; do chrt -f -p $p $i; p=$(($p-1)); done > > where: > IRQ 1 i8042 (keyboard) > IRQ 9 ice1712 (delta66) > IRQ 11 ymfpci (used only for midi > IRQ 8 rtc (is setting prio for this necessary?) > > I set the prio for the rtc because the wiki says to turn off threads for > it ... but, from what Florian said earlier that is only for > desktop-preempt now. Since this kernel is realtime-preempt and all > handlers are threaded, do I still need to treat the rtc specially? The rtc prio only needs to be high when you use a software that needs the rtc. I think, some midi sequencers use it (used it), so i thought it doesn't hurt when i advise people to give it a high prio, too.. When it's not used, the high prio shouldn't have any negative effect either.. > jackd starts fine like this: > LD_ASSUME_KERNEL=2.4.22 jackd -v -R -P 90 -d alsa -d ice1712 -p 64 -n 2 90 is a bit high. jack also starts a watchdog thread with a prio +10. I'd recommend a prio of 60 or 70 for jackd. May i ask why you use the LD_ASSUME_KERNEL hack? Do you get bitten by the nptl-hell? Try running jackd without it and check the threads with chrt. > no xruns except the expected ones on client connect/disconnect. Does it > matter which version of 2.4 is assumed? I've seen .22 and .19 in various > places. I don't think so. But i'm not sure. I think for libc the only important thing is that it's a 2.4.x version and thus uses the linuxthreads implementation instead of nptl.. > I can run this script: > http://zhevny.com/bin/ecamynthes/ecanoscl-i-0.0.2.sh > > which now starts ecasound like this: > chrt -f -p 80 ecasound <various_options> > and sets LD_ASSUME_KERNEL > > The script runs fine and connects to jack, but the audio it produces is > very scratchy. This may have something to do with ecasound itself, > though, since I upgraded that yesterday. Is it possible that the extra > CPU overhead of preempt_rt is causing this? I'm guessing not since my > box has >2GHz cpu, but maybe it isn't only about cpu power ... > > How significant is the extra overhead of preempt_rt compared to > preempt_desktop? Has anyone done any statistics? Well, i run preempt_rt on a 1.2ghz athlon here and it works fine for audio stuff. I don't see any obvious performance differences. Flo -- Palimm Palimm! http://affenbande.org/~tapas/
