The different realtime kernels
scottalavender at gmail.com
Thu Sep 30 20:10:44 BST 2010
On Thu, Sep 30, 2010 at 1:40 PM, Ralf Mardorf <ralf.mardorf at alice-dsl.net>wrote:
> On Thu, 2010-09-30 at 13:25 -0500, Scott Lavender wrote:
> > On Thu, Sep 30, 2010 at 11:44 AM, Ralf Mardorf
> > <ralf.mardorf at alice-dsl.net> wrote:
> > On Thu, 2010-09-30 at 17:15 +0100, Ricardo Lameiro wrote:
> > > I agree with you. I think the best compromise is to use the
> > Hard RT
> > > kernel patch on top of vanilla kernel, and have the Generic
> > kernel for
> > > everyday usage.
> > > You can choose which kernel to boot from at the beginning,
> > I only use vanilla + rt-patched kernels for audio-video and
> > everyday
> > usage. The only difference is the CPU frequency scaling. For
> > everyday
> > usage I set it to ondemand and for audio-video work to
> > performance and
> > sometimes I manually enable hr timer when doing MIDI work.
> > IMO just a kernl-rt is needed, but as I mentioned before,
> > people running
> > 32-bit architecture might need a patch to enable usage of
> > large RAM.
> > But indeed, GRUB is our friend, we are free to use several
> > kernels. OT:
> > GRUB is a little bit more user-friendly than GRUB2 is ;).
> > > Hard RT kernel, should be the only one to be supported,
> > since it is
> > > the kernel that brings more benefits to audio/video
> > production, If we
> > > spread attention with 2 more kernel flavours, no one can
> > support it,
> > > and lets face it, abogani makes a hell of a good job, so we
> > should
> > > simplify is life :D
> > Hm, on my Ubuntu Studio, neither Abogani's, anyone else or my
> > own build
> > kernel-rt are ok :(. I can't boot any kernel-rt.
> > I'm able to run Suse with my self build kernel-rt, but not
> > with the
> > repositories once and I'm able to run 64 Studio (Hardy,
> > Karmic) with
> > kernel-rt from the repositories and self build kernels.
> > Live CDs, e.g. AV Linux are ok with the kernel-rt.
> > Anyway, the rt-patch could be a PITA, while the PREEMPT only
> > kernel for
> > Ubuntu Studio is ok on my machine, as far as a PREEMPT only
> > kernel is
> > able to do some jobs, but I'm able to boot the kernel.
> > IMO we only should take care of the kernel-rt and no other
> > kernel.
> > Hard disk drives today are less expensive so everybody should
> > be able to
> > install a distro for audio-video usage and if needed other
> > distros for
> > other usages, because not only the kernel makes a different.
> > IMO a DAW
> > e.g. don't need the security that's needed for some other
> > usages.
> > I'm running several Linux, no Windows, on my 2 core AMD 64-bit
> > PC, for
> > everyday usage and audio-MIDI productions, all Linux with
> > kernel-rt
> > only, excepted Ubuntu Studio, because I didn't had the time to
> > troubleshoot why I'm unable to boot a kernel-rt for Ubuntu
> > Studio.
> > I prefer 64 Studio, but I really like Suse and Ubuntu Studio
> > too, of
> > course there are some other good distros, but those three are
> > my
> > favourites, even if Ubuntu Studio until today isn't ready for
> > production.
> > I like the concept of Ubuntu Studio, excepted of the default
> > PREEMPT
> > kernel, without rt-patch.
> > This are just my personal 2 cents, the advantage of Linux,
> > that we do
> > have a lot of different paths we could go, even if it
> > sometimes seems to
> > be a disadvantage.
> > --
> > Ubuntu-Studio-users mailing list
> > Ubuntu-Studio-users at lists.ubuntu.com
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> > https://lists.ubuntu.com/mailman/listinfo/ubuntu-studio-users
> > This isn't necessarily addressed to Ralf, but it ties in with the
> > comments in his email.
> > Ubuntu Studio as a project makes far fewer decisions that people
> > probably expect. The kernel is a good example.
> > The Ubuntu Studio team did not decide to remove the -rt kernel from
> > the ISO image because we think it is inferior or that another kernel
> > performs better. We would like to still be able to provide it to our
> > users because we understand that it yields performance that other
> > kernels cannot provide. We can no longer provide the -rt kernel in
> > the ISO image because it is no longer in the official archives.
> > Ubuntu Studio exists and must maneuver within Canonical/Ubuntu
> > ecosphere. And sometimes decisions are made by Canonical or Ubuntu
> > that grossly affect Ubuntu Studio. Some of those can be mitigated
> > (e.g. ubuntustudio-menu vs. ubuntu menu with social integration) and
> > others cannot.
> > By the way, mitigating such things is a very good reason to keep
> > building ISOs instead of just focusing on a Ubuntu Studio PPA.
> > Some of the reasoning to remove the -rt kernel is because of a desire
> > to keep the kernel versions aligned between Ubuntu and Ubuntu Studio.
> > And since the -rt patch is not available for every kernel version
> > release, to continuously maintain the alignment would eventually be
> > untenable, as witnessed with Lucid.
> > Therefore, Ubuntu Studio is progressing to get the -lowlatency kernel
> > accepted and promoted to the official archives. This way we can offer
> > it in the ISO image. This would provide a performance tuned kernel
> > that hopefully most of our users will find acceptable
> > "out-of-the-box". Since the -lowlatency kernel results from compiling
> > the -generic kernel with different flags (at least my understanding of
> > it), it can be easily and continuously maintained in the repositories.
> > For those who still require an -rt kernel, we are planning to
> > accommodate those persons by offering the -rt kernel in a PPA.
> > However, it should be noted that the -rt kernel version will not
> > necessarily align with the kernel offered with any particular current
> > Ubuntu Studio release. As mentioned previously, since we cannot
> > control which versions will have a -rt patch released, therefore we
> > cannot control which versions can be -rt kernels. And we certainly
> > are not going to have Ubuntu as a whole use an older kernel to keep us
> > in sync.
> > I would not expect the -rt kernel to ever be in the archives again for
> > the reasons mentioned above. This is a secondary effect of developing
> > Ubuntu Studio within the Ubuntu framework. A small detraction, given
> > that we can still offer it in a PPA, given the overwhelming sea of
> > gains of working within the framework.
> > I hope this clears up any misconceptions.
> > Cheers,
> > ScottL
> 2 cents:
> Of course the rt-patch isn't available for every vanilla kernel version.
> But is it wise to have a distro that includes applications like Ardour,
> JAMin, JACK etc. without a kernel-rt?
> What do you think would be the answer, if somebody has got an issue when
> using Ardour and the person ask at the Ardour users mailing list,
> posting that the kernel isn't a kernel-rt?
> What is Ubuntu Studio for?
> I guess we could install a 'normal' Ubuntu and add Ardour, JACK etc., if
> Ubuntu Studio don't support a kernel-rt I don't understand what it
> should be for?
> Supporting real-time applications without a kernel that is patched with
> a rt-patch IMO is pointless.
> Ubuntu-Studio-users mailing list
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How do you suggest that the -rt kernel be included in Ubuntu Studio if it is
not in the Ubuntu repositories?
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.
If an acceptable solution is not found to include it in the ISO then I
believe that we are providing the next best solution; provide another
performance tuned kernel (i.e. -lowlatency) and make sure that the -rt
kernel is available in PPA and people know about it.
I routinely run Ardour on my P4 2.3ghz desktop with 1.5gigs of memory and
the -generic kernel at 11msecs latency and only see xruns when starting
applications. I would imagine that the -lowlatency kernel gives even better
Please test the other kernels available before saying that running
applications without a rt-patched kernel is pointless.
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