The different realtime kernels
Ralf Mardorf
ralf.mardorf at alice-dsl.net
Sat Oct 2 06:12:26 BST 2010
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
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