[linux-audio-user] realtime-preempt-2.6.11-rc1-V0.7.35-01

Jack O'Quin joq at io.com
Sun Jan 16 18:17:51 EST 2005


Eric Dantan Rzewnicki <eric at zhevny.com> writes:

> 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.

Either is fine.  It forces glibc to use the old-style kernel
interfaces for threading, so it to uses linuxthreads instead of NPTL.

> 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?

Yes.  The other two realtime threads are the JACK watchdog timer and
the Linuxthreads manager thread.

> 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

You should probably set LD_ASSUME_KERNEL consistently for all clients,
but the `chrt' should not be necessary.  JACK will set all the client
process thread priorities to 89 (one less than 90), IIRC.  You don't
want to mess with the other ecasound threads.  They'll just interfere.
-- 
  joq



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