Re: [jazzplusplus-devel] Thoughts about the linux kernel - observed trends

[Robert V. <vo...@ct...>]

On Thu, 2008-05-15 at 12:13 +0000, D.B. Moore wrote:
> 
> ----------------------------------------
> > Date: Tue, 13 May 2008 22:10:47 -0700
> 
> 
> >From thread ;
> 
> 
> > Subject: [jazzplusplus-devel] Debian Build and Run Attempt
> > 
> > RV = Robert Vogel wrote me on Sun, 11 May 2008 23:14:04 -0400
> > RV> Hi Pete,
> 
> > RV> I tried compiling Jazz++ on my Debian Etch stable system.
> > RV> It looked ok throughout the build process, and it produced
> > RV> an executable. When I tried opening the executable, it
> > RV> didn't prompt for a configuration file, but it found one
> > RV> in my home directory. I'm not sure it is the correct
> > RV> jazz.cfg though. (attached)
> 
> 
> 
> > RV>
> > RV> Rosegarden complains every time I start it that the
> > RV> 'system timer resolution is too low'. I know I need
> > RV> to find a RT kernel, but I've been too cautious to
> > RV> try one yet. Soon. That's why I need to be able to
> > RV> connect to an external device or to a soft synth.
> > RV>
> 
> 
> Thanks Robert, you've pointed out something we all know
> is a bit of an issue with linux. This really bites too when
> considering so called 'realtime' software applications, and
> timing sensitive transports like MIDI with linux.
> 
> Here's my thoughts and current experience with things
> smelling of herring...
> 
> Whether Robert really needs to 'find' a  'RT' kernel is
> probably up for debate. I mean...I haven't looked lately
> but patched&hacked RT kernels are out there, so are 
> the patches needed to compile your own, but there is
> SO MUCH dated and old documentation out there,
> it's not surprising to find comments like this.
> 
> There's a lot of the same out there. I actually know
> rosegarden (as a piece of software), and I'm also
> familiar with that runtime complaint about timer
> resolution. Old documentation leads people into 
> believing they need an RT kernel - perhaps they do
> in certain situations - but most people do not.
> 
> What they need to do instead, is reconfigure their
> linux source tree, recompile, install, and reboot to
> the new kernel. Compiling Jazz++ from svn is a 
> doddle for most people compared to a kernel rebuild.
> 
> In the configuration phase, they need to set
> the kernel timer resolution to 1000Hz. It can also
> matter (performance wise) which pre-emption model
>  is selected, and what task-scheduling is selected. Or 
> even how powerful (or not) their hardware is.... 
> 
> It's a minefield -- depending on just which linux distro
> people are using, determines exactly which kernel
> options were selected and configured in the 'standard'
> kernel build. Also, just how easy it might be for people
> to fix things themselves largely depends on which
> linux distribution they use as much as it does on their
> own skills or the instructions they might be following.
> 
> 
> I don't want to write yet another kernel howto - I am
> prepared to document this issue pretty much like I do 
> here, pointing out the issues, giving out clues, but just
> because of the large disparity and possible difference
> between one linux distro compared to another, the user
> is very much  largely on their own with that one.
> 
> I'm just wondering if something more can be done about it
> ...or nothing at all....and I just somehow get the feeling, 
> someday this will bite us all....
> 
> Regards,
> 
> Donald B
> 
Thanks for your note Donald. 

I think my version of this problem should belong to Debian. If they
accept a package into a stable version of thier distro, it should run
with the standard kernel...or they could offer a properly configured
one.

On the other hand, I can drive an external device or a software synth
with Rosegarden, so I don't feel that I'm missing much functionality
even without the RT kernel.

Can anyone tell me that it is worth the trouble in terms of sound
quality to patch the kernel ? 

Bob 


> 
> 
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