On Tue, Feb 14, 2012 at 12:21 PM, Fernando Lopez-Lezcano <nando@ccrma.stanford.edu> wrote:
On 02/14/2012 11:31 AM, Brian Monroe wrote:
I've been spending a lot of time on the #opensourcemusicians channel
talking to Ubuntu Studio users about their kernel and latency times
they're getting. Seems like most of them are using g a stock kernel with
the preemptive option enabled and they are getting great latency results
(2ms)while utilizing the @audio group on their user. I ended up
compiling my own low latency kernel and I haven't had any issues with it
yet. If this is what we are missing for the spin I'd be happy to
maintain packaging for the kernel.  I know ccrma has been behind a few
kernel releases.

The latest I have, current in testing is 3.2.2 + rt11 (for Fedora 15 and 16). I am currently trying to build 3.2.6 + rt12.

Ah, that may have been an error on my part, I thought last I checked, which admittedly was a week and a half ago there was only a F15 kernel on the CCRMA website. 

The current rt not in testing is a 3.0.x based release (fc15/16). I have not seen a big interest on being up to date - I just try to keep up with the latest rt patch set. If there is more interest I could try to keep up (but keeping up with _what_?, for a bit I was testing a 3.2 based rt patched kernel and that was still not available for fc16 as an official release).

I saw the instructions for adding the real time patch for a tick less
kernel and from what I can tell it wouldn't be hard to get that rolling
as well.

I'm not entirely sure what ccrma does differently with their kernels
compared to other Linux users,

"compared to other Linux users"? I don't follow.

Namely the Ubuntu Studio folks. Most users in #opensourcemusicians seem to use Ubuntu. Why? I don't know.

and I'm still a bit of a noob so I could
be off base with this, but I would reason that we should be able to just
utilize the same settings to archive similar performance enhancements.

I thought I read that ccrma uses a unique scheduler, but if we could get
a 2ms latency time without it, the point may be moot.

Nope, no unique scheduler or other stuff. Where did you read that? (links please?)

To be honest I'm not sure where I read this, but I do remember having conversations about it in one of the channels. Part of the reason I wanted to email the list was to hear what's what from the source, so thanks for clearing that up for me. 

The Planet CCRMA rt patched kernels are based on recent Fedora source packages (usually from Koji) that are the closest I can find to the kernel releases for which rt patches are available. To that source package I add the rt patch, drop Fedora patches that are already included or conflict, and built that. I use pretty much the stock Fedora kernel configuration files except for whatever tweaks are necessary to enable the rt patch for full preemption. That's about it.

Is there any help needed for testing/ect? I'm just trying to figure out what I can do to start contributing.

As work in the rt patches has progressed the stock Fedora kernel (which is basically upstream plus a few patches that have not been merge yet) has become more and more usable for "normal" music work. For low latency work (in a word, using your computer as a musical instrument), an rt patched kernel still has an edge. Whether that really makes a difference depends on your usage, your tolerance to occasional xruns and even the exact hardware you are running on. 

-- Fernando