21 Dec
2005
21 Dec
'05
5:06 p.m.
On 12/21/05, Florian Schmidt <mista.tapas(a)gmx.net> wrote:
Well, rtlimits doesn't do this either.
The mechanism to gain realtime privs and the worst case scheduling
latencies of the kernel are two completely different issues.
For the former, there's the realtime-lsm and rtlimits which _only_
enable a non root user to do what a root user could do anyways.
For the latter, there's the -rt kernels, although the vanilla kernels
are quite usable these days, too.
I see, this is exactly the kind of thing I was looking for, and now
that I think about it, it makes total sense. Let me see if I
understand it: rtlimits allows a normal user to preempt, but you must
enable the preemption option in the kernel config in the first place
for it to do any good. Is that it?
It is quite ok for most uses, especially when not
going for ultra low
latencies (like 8 or 16 frames). Make sure you use the "(X) Preemptible
Kernel (Low-Latency Desktop)" setting though when building a vanilla
kernel (or make sure your distro builds it this way if you use a distro
provided kernel; check i.e. /proc/config.gz and/or write a mail to the
appropriate ML/maintainer).
Again, this is apparently the part that must be "enabled" to see the
full benefits of using rtlimits, correct? Once I've enabled this
option (Preemptible Kernel), do I then have what you are referring to
as a -rt kernel?
Also the -rt kernel, due to prioritizing the irq
handler threads,
provides better RT "guarantees" if you want to call it that ;) I.e.
given that the scheduler works correct, and that you have setup the
priorities in your system correctly (and that jackd ant the clients are
well behaving RT programs), there's almost _no way_ that other system
activity might cause delays that produce xruns in turn, even with
ridiculously low latencies.
I don't think that I am the type of user that needs that kind of low
latency, I just need enough to do my basic home recordings.
I think, in light of this, I might install DeMudi on my seperate
partition; it might avoid all of this kernel business very easily. I
still hate that I don't know how to do things myself, so any further
comment is welcome.
Thank you very much for your comments,
Josh
--
Josh Lawrence
http://www.hardbop200.com