Re: [LAU] difference between realtime-kernel and low-latency-kernel?

Hi Florian.
I understood nice to be an adjective, but I was questioning the word "low";
I see now you were referring to non-audio, so I understand.

I have two jackd scripts I use, one for Playback-only, and one for duplex
using my Zoom H4 mic. I have attached the scripts and their outputs from
your script. See anything I could improve?

Thanks.
-Chuckk

On 10/4/07, Florian Schmidt <mista.tapas@email-addr-hidden> wrote:
>
> On Thursday 04 October 2007, Chuckk Hubbard wrote:
>
> > > Well, with a vanilla kernel you simply don't get the fine grained
> control
> > > over
> > > what code gets the cpu at what times as with a realtime-preemption
> > > kernel..
> > >
> > > It is true that for many people a vanilla kernel with CONFIG_PREEMPT
> and
> > > CONFIG_HZ=1000 delivers great performance, probably even better than
> > > a "lowlatency" 2.4.x kernel. But basically one badly behaving kernel
> > > driver
> > > might cause delay, so for differing people the results differ. With a
> -rt
> > > kernel you would just give this device a nice and low prio, so it
> doesn't
> > > even get a chance to disturb the soundcard/jack..
> >
> > I'm a big fan of my rt-patched kernel; I'm also a big fan of taking out
> > most of the distro's default stuff from the kernel. One of these days I
> > will compile an rt kernel with no network support even - my soundcard
> > shares an IRQ with eth1, I don't know if this will help or not.
> > But isn't it a nice and high prio? As in, the chrt prio? I understood
> > this as different from the nice prio, no? I may not be doing it
> correctly.
> > I set my soundcard IRQ to something like 70, jackd to something like
> 65,
> > and Pd to something like 60. The Pd GUI I set a little lower yet. Do I
> > also have to renice these apps?
>
> Well forget the word "nice" in that sentence. It has nothing to do with
> nice
> levels :) Nice levels are only relevant for SCHED_OTHER processes.
> Anyways,
> if your e.g. hd controller device disturbs your audio device make sure you
> give the audio device a high prio and the controller device a low prio.
> That
> was what i meant..
>
> And yes, i consider it a bug that top and other software report the
> SCHED_FIFO
> prio as negative values. Where does that come from? Does the prio already
> get
> listed as negative in /proc? Or do they simply do it to separate the
> SCHED_FIFO threads from SCHED_OTHER threads? Anyways POSIX speaks of
> positive
> SCHED_FIFO prios in the range 1..99 afaik..
>
> > I get visible xruns but not audible so far. I am guessing I have the
> wrong
> > buffer sizes between Pd, Csound, and jackd...
>
> No, i don't think so. If you use Pd and CSound as jack apps, then jack
> tells
> them what buffer size to use. If one of these used the wrong size you
> would
> definitely hear it..
>
> Start jack and run this script and tell us the output please:
>
> http://tapas.affenbande.org/rt-setup-report.sh
>
> Thanks,
> Flo
>
> --
> Palimm Palimm!
> http://tapas.affenbande.org
>

-- 
http://www.badmuthahubbard.com

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