Jack O'Quin wrote: > Eric Dantan Rzewnicki <eric@xxxxxxxxxx> writes: >>How do I set jackd's priority? > Use the -P option. Thanks Jack. I'm still working with CONFIG_PREEMPT_RT for now. Current audiobox set up: http://zhevny.com/doc/audiobox_settup Current kernel config: http://zhevny.com/doc/config-2.6.11-rc1-rt-v0.7.35-01-audiobox-1 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? jackd starts fine like this: LD_ASSUME_KERNEL=2.4.22 jackd -v -R -P 90 -d alsa -d ice1712 -p 64 -n 2 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. there are 5 jackd threads started. Only one has prio 90 as specified with -P. It and 2 others are SCHED_FIFO, but the 2 other are prio 99. How did they get that? The remaining 2 threads are SCHED_OTHER with prio 0. Is this expected behavior? 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? Let's see .... have I missed anything? I get >50MB/s for all my drives in hdparm -t tests. Any other low latency best_(guess)_practices I should be aware of? Thanks guys, Eric Rz.
