[linux-audio-user] Kernel tweaking for low latency

[Joe Hartley]

On Tue, 7 Sep 2004 00:30:33 -0300
luis jure <ljure at multitel.com.uy> wrote:

> el Sun, 05 Sep 2004 21:48:29 -0400
> Ben Sheron <ben at whatsmykarma.com> escribió:
> > So, how exactly do I go about optimizing a kernel for audio, especially
> > on SuSE?  Does SuSE have a precompiled one available, or is it best to
> > just compile it on my own? 
> 
> i'm not an expert, but since you've had no answers so far, let me tell you
> that i haven't switched to 2.6 yet, i'm still using 2.4.26 with three
> patches: low-latency patch, preemptive patch and capabilities patch, and i
> have a fairly good performance. every time i install a new kernel i have to
> google for them patches, i never remember where they are... perhaps suse or
> some third party provides pre-patched kernels for audio, i wouldn't know.

Having trodden down the path of optimizing a system for Linux audio work
before, I've picked up a few things along the way.

The first was to lose any sense of wanting to hold onto a predefined
path.  Put it all on the table - the distro you use, the kernel you want,
and start with a clean slate.

Once I found the Planet CCRMA project, which provides a modified RedHat/
Fedora distribution with precompiled kernels and audio apps, things became
so much easier.  There are also other projects of the same ilk (Angula?
something like that) for other distros.

As much as I want to play with the latest and the greatest, when it came to
the studio machine, I let system optimation drive every decision.

So that machine (A 1GHz PIII w/ 512MB RAM, 3 hard drives and a CD burner)
is still running a 2.4.26 kernel, and I've got no plans to switch until
such a time that people with far more knowledge than I deem it ready for
realtime work.

So my advice for a Linux audio workstation?  Check out the audio distros
mentioned above, pick one, and configure the system from the ground up
around it.  Just itching to try the latest 2.6 kernel patches?  Great!
I'm really glad people want to blaze that trail!  But it's best done on
a machine other than the one you want to do recording on this weekend,
or at the very least in another partition that won't affect your working
environment.  And then check out the websites for optimizing IRQs and
hard drives and turning off CD polling and every other trick compiled
for setting up a Linux audio workstation.

After months of xruns popping up at the most inconvenient times, I now
have a rock-solid system in my studio.  So what if it's still based on
RedHat 9?  It _works_.

Good luck!

-- 
======================================================================
       Joe Hartley - UNIX/network Consultant - jh at brainiac.com
Without deviation from the norm, "progress" is not possible. - FZappa