The different realtime kernels

[Ralf Mardorf]

On Fri, 2010-10-01 at 11:23 -0500, Scott Lavender wrote:
> 
> 
> On Fri, Oct 1, 2010 at 7:38 AM, Ralf Mardorf
> <ralf.mardorf at alice-dsl.net> wrote:
>         On Thu, 2010-09-30 at 14:10 -0500, Scott Lavender wrote:
>         
>         > [snip]
>         > This is not a rhetorical question.  I, as Ubuntu Studio
>         project lead,
>         > would like to include it.  If you can provide a tenable
>         method to
>         > include the -rt kernel in the Ubuntu Studio ISO image I
>         would like to
>         > implement it.
>         
>         > [snip]
>         
>         Hi Scott :)
>         
>         I'm not sure, if I do understand the problem.
>         
>         Does Ubuntu need the same vanilla kernel version for different
>         kind of
>         kernels, e.g. to provide packages for proprietary graphic
>         modules?
>         If so, IMO it's not needed to make the multimedia distro full
>         compatible
>         with a regular Ubuntu.
>         
> * snip *
> 
> I think you are missing the point.
> 
> It does not matter _why_ certain kernels are maintained and available
> in the repositories.  It only matters _that_ the decision was made.
> 
> The only kernels I can include within a Ubuntu Studio ISO image are
> the kernels available from the official Ubuntu archives.
> 
> Furthermore, I do not decide which kernels may be included in the
> archives.  That ultimate decision is made by others, although I may
> provide some small influence on it.  This is an example of when I
> mentioned "working within the Ubuntu framework".
> 
> To summarize:  Others control which kernels are available and
> maintained in the archives and I get to select from the available
> kernels which one to include in the Ubuntu Studio ISO image.
> 
> To state what is "needed" or "required" or "worthless without" for
> multimedia production is irrelevant.  I say again, to build a Ubuntu
> Studio ISO image within the Ubuntu framework I must choose from the
> available kernels in the repositories, of which I wield extremely
> limited influence in deciding which are to be available.
> 
>  
> 
>         Multimedia producer just need a kernel-rt and a package
>         including the
>         headers to compile e.g. drivers for graphics.
>         
>         For my needs the kernel-rt doesn't provide hard enough
>         real-time, but
>         the kernel-rt is a compromise that might enable some audio
>         productions.
>         
>         You might wish to compare a C64, Atari ST or stand alone
>         sequencer from
>         the eighties with a kernel-rt and a kernel without rt-patch
>         used by a
>         good classical or jazz musician. There still is too much
>         jitter, but the
>         kernel-rt for sure will be the first kernel, that might be
>         able to get
>         the knack of it.
>         
>         The kernel-rt is the best we do have for Linux, hence it's
>         invalid to
>         use a less good kernel, as long as even the kernel-rt isn't
>         able to do
>         hard real-time.
>         
>         So, if there should be a rule for Ubuntu, that all patched
>         kernels has
>         to base on the same vanilla version, which is a good thought,
>         it's not
>         good for multimedia productions.
>         
>         There are coders who program the rt-patch, to make Linux
>         better and
>         better, it's not smart if a multimedia distro tries to be
>         smarter by not
>         using a kernel-rt, because it shouldn't be needed.
>         
>         The kernel-rt is needed and there should be no rule not to use
>         it.
>         
>         Btw. to make the issue harder. It's not only that there isn't
>         a rt-patch
>         for every vanilla kernel, sometimes a current
>         rt-patch-kernel-combination can be bad, so that we need to
>         keep older
>         rt-patched kernels. Sometimes it's not possible to keep
>         'things' that
>         are available by a generic kernel of the same vanilla version,
>         when
>         using the rt-patch, but there's no need to keep all kernel
>         features for
>         real-time audio productions.
>         
> 
> * snip *
> 
> No one is suggesting that the -rt kernel is not a good thing or that
> is not to be preferred over other kernels.  However, stating that the
> -rt kernel is needed or multimedia production is worthless without it
> is not going to change the fact that the -rt kernel will not be
> included in an Ubuntu Studio ISO image for the reasons stated above.
> 
> Furthermore, no one is stating that you should not use the -rt kernel.
> Quite the contrary, it is almost required for laptop users with
> firewire audio interfaces and we have made it very clear that we will
> make the -rt kernel available via a PPA.
> 
> Again, this is not our choice to include a kernel other than the -rt
> kernel released in Ubuntu Studio.  It is a necessity dictated by what
> is available in the repositories.
> 
> Lastly, I am curious to which hardware you are using if you find that
> the -rt kernel is not hard time enough for your needs.

Today a PC isn't able to do hard real-time. As I've written before, my
machine is a AMD 2.1 GHz dual-core, I've got two Envy24 based PCI sound
cards and in addition I'm not using any USB device, even mouse and
keyboard are PS/2.

Hard real-time only is possible on computers were you can control the
hardware directly, e.g. a C64 or Atari ST, on a modern PC you only have
the choice to select the lesser of the two evils, e.g. avoid USB-MIDI,
but use PCI-MIDI, to get less jitter, anyway, on a PC you always will
get jitter.

> 
> 
>         The need for hard real-time is an exceptional case, not only
>         for
>         multimedia production, there are other real-time patches, e.g.
>         for the
>         Enhanced Machine Controller project.
>         Some people and you might be fine with a non-real-time patched
>         kernel,
>         but most professional studios aren't even fine with the
>         kernel-rt or on
>         Windows  ASIO, resp. ASIO + Nuendo on some machines should be
>         near to
>         eighties hard real-time.
> 
> * snip *
> 
> I would argue that Ubuntu Studio is not for a professional studio.
> 
> Despite what others might argue or what various documentation might
> say, I believe the Ubuntu Studio is NOT for professional use in a
> recording studio.
> 
> In my opinion, much greater control would be required to tailor
> kernels, applications, and system systems.  A company like Indamixx
> and their OS, Transmission 4.0, would be an example.
> http://www.indamixx.com/indamixx-iso-download.html

Indamixx is using 64 Studio, the distro I'm using to produce music.

> 
> To be direct, I would first remove Pulse Audio, stop shipping all
> graphical and video applications, and use a lighter desktop to
> maximize performance for starters.  Additional changes would be
> required as well, there were just the first I could think of.
> 
> Before some ask why isn't this done already (especially removing Pulse
> Audio), we lack the developer resources to handle it and most of our
> users most likely use the same machine for normal day-to-day uses
> (i.e. internet, email, etc).

I'm using email etc. with 64 Studio (based on Ubuntu) too and I'm not
missing PulseAudio when mailing etc.. Anyway, on my Suse PulseAudio is
installed it's a PITA, but has got no influence to audio productions,
PulseAudio for me is a PITA just for day-to-day use.

Unfortunately until now I'm unable to use Ubuntu Studio too. Startup is
interrupted when I try to boot the kernel-rt from the repositories, I
also had an issue with a self build kernel-rt, but I can't remember it
now, as I've written before, as soon as possible I'll try again to boot
and build several kernel-rt.

> 
>  
>         Cheers!
>         
>         
>         Ralf
>         
>         
> 
> I hope you find this information useful.

It is.

> 
> Regards,
> ScottL

Cheers!

Ralf