[LAU] A surprisingly stupid RT priority question

[Paul Davis]

nice has absolutely nothing to do with this, and if it has any effect, it
is accidental and should not be relied on.


On Sun, Dec 2, 2012 at 7:50 PM, jim <jim at well.com> wrote:

>
>     You probably tried using the  nice  command,
> maybe with most processes +10 and with -10 for
> your music processes, yes?
>
>
>
>
> On Sun, 2012-12-02 at 13:00 -0800, Ken Restivo wrote:
> > OK, I know I've been using Linux audio for 6 years now, and gigged and
> recorded with it extensively for most of those, yadda yadda. But it seems
> I've had an embarassingly huge hole in my knowledge the whole time.
> >
> > I was under the impression that, in order to use real time
> priorities/permissions and Ingo kernels, it was required for the process
> ITSELF early in the main() routine of its source code, to make some system
> calls to claim RT priority. In fact, I specifically remember reading or
> even writing source code in C which did that (probably based on JACK sample
> code). I don't recall the name of the syscall, but it was something obvious
> and well-documented.
> >
> > Also, I remember that it was also required that the software behave
> properly in order to be real-time capable, something about callbacks taking
> some predictable amount of time. Or perhaps that was only a JACK
> requirement.
> >
> > Why am I asking these dumb-ass questions now? Because I've been playing
> around with Liquidsoap and Airtime for some radio stations, and I'm
> obsessed with getting them as rock-solid on cheap/free/old hardware as I'd
> been able to get with my gigging and studio synths.
> >
> > It physically pains me to hear audio stuttering because Apache is
> running on the same box. It seems an outrage to me. Shouldn't happen. Ever.
> I used to record and mix multi-track songs in Ardour with tons of
> soft-synths WHILE A KERNEL COMPILE WAS GOING ON THE SAME MACHINE without a
> single glitch. I expect no less.
> >
> > So I asked on the Liquidsoap list, and I got only shrugs and a pointer
> to the Gentoo page in response (why? I have no idea. I use Debian, and
> that's irrelevant to the question at hand anyway.).
> >
> > So what's the deal? Is there a way to give Ingo-approved preemptive RT
> priority to things that aren't real-time apps and aren't specifically
> architected for that? What, if anything, would break?
> >
> > And, if I wanted to hack Liquidsoap (which would require learning ML,
> which wouldn't be a bad thing to know anyway), is it even possible to get
> it RT-capable, or are there low-level C system calls required in order to
> make that work?
> >
> > Sorry for the long and obscure question, but it's been bothering me for
> a while, and I figured someone here would know the answer, or where I might
> find it.
> >
> > Thanks.
> >
> >
> > -ken
> > _______________________________________________
> > Linux-audio-user mailing list
> > Linux-audio-user at lists.linuxaudio.org
> > http://lists.linuxaudio.org/listinfo/linux-audio-user
>
>
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