[LAU] unable to set scheduling priority with rt kernel

[Lee Revell]

On 10/29/07, Chuckk Hubbard <badmuthahubbard at gmail.com> wrote:
> On 10/29/07, Lee Revell <rlrevell at joe-job.com> wrote:
>
> > On 10/29/07, Chuckk Hubbard <badmuthahubbard at gmail.com> wrote:
> > > Update: I just discovered that running jackd -R -P 70 -dalsa -P -p256
> -n2
> > > -r44100 as ROOT doesn't even set priority 70.  jackd then runs as a root
> > > process with priority 20, according to both chrt and top.
> > > Apparently my system is not able to run anything higher than 20
> priority;
> > > does this mean my kernel is misconfigured, or might it be something
> else?
> >
> > jackd is a multithreaded process, you can't just look at the priority
> > of the main thread, you have to check all of them.  It should have
> > some SCHED_FIFO threads and some SCHED_NORMAL threads.
>
>
> Interesting, I'll have to keep reading until I find out how to do that.
> But is it normal, then, that chrt -p 70 `pidof "jackd"` would set rtprio 70
> but jackd -R -P 70 etc. wouldn't?
> Which is to say, if chrt can set the main thread priority, why not the -P
> flag?
>

That's normal.  The main thread is not supposed to be SCHED_FIFO.

Lee