[Ardour-Users] The future?

[Fernando Lopez-Lezcano]

On Thu, 2010-08-12 at 15:24 +0100, Nick Murtagh wrote:
> On 12 August 2010 15:11, david headon <davidheadonuk at yahoo.co.uk> wrote:
> >   I'm not sure why. I find similar non-functionality with the Ubuntu repos
> > and their 'realtime' kernel..
> > Longer boot times, and no discernible performance improvements...
> > Perhaps even worse!
> 
> Here's what ubuntu do to create "their" kernel:
> 
> http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/lucid/linux-rt/lucid/annotate/head:/debian/patches/series
> 
> Very little. It's basically vanilla. Are the other distros patching
> their realtime kernels more than this?

The Planet CCRMA rt kernel is applied on top of (usually) bleeding edge
versions of the Fedora kernel builds. So it has whatever fixes Fedora
adds - but only those that allow the rt patch to patch cleanly - plus
the rt patch, and almost nothing else. 

The kernel configuration (also important) is vanilla Fedora plus the
usual rt tweaks. 

(BTW, the current version on fc13 is 2.6.33.7-rt29)

As to why different distros rt kernels act differently I don't really
really know. I would imagine it would be very difficult to do a
scientific comparison, too many variables. One caveat to take into
account is that performance not only depends on the rt kernel itself.
The interrupt priorities have to be properly prioritized (thanks to
Rui's rtirq script plus a correct configuration). And Jack itself has to
run at the right rt priority level as well (below the soundcard irq
priority but above everything else). If those priorities don't match up
correctly the performance will not be as good. 

Plus, of course, the hardware you run on will also make a difference. 

-- Fernando