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

[Chuckk Hubbard]

On 10/4/07, Florian Schmidt <mista.tapas at gmx.net> 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?


This goes as far that if one sees an xrun while running a properly
> setup -rt-kernel one knows it's an application bug or a soundcard driver
> bug ;) The kernel itself or any userland processes (X, cronjobs, whatever)
> as
> a source of timing problems are pretty much eliminated.


I get visible xruns but not audible so far.  I am guessing I have the wrong
buffer sizes between Pd, Csound, and jackd...

-Chuckk

-- 
http://www.badmuthahubbard.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.linuxaudio.org/pipermail/linux-audio-user/attachments/20071004/362a32a2/attachment.htm