Fedora 10 as basis for RT?

Fedora 10 as basis for RT?

[Al Dorrington]

Hi,

I am working on a proof of concept project where we are going to try moving an
application that runs on VxWorks to Linux. I believe with what I've read on this
mailing list, and the RTwiki site that Linux is definitely up to the task with
these kernel patches.

However, I am not really sure which distribution of Linux we should use as the
base, nor am I sure if it would be better to stick with the 'i386' distribution
or go with the x86_64 variant.

I am considering Fedora 10, either i386 or x86_64. 

Does anyone have any comments or recommendations for which might be better to
use, or if we would be better off using another distribution?

Thanks!
- Al Dorrington

Re: Fedora 10 as basis for RT?

[Thomas Gleixner]

Al,

On Thu, 9 Apr 2009, Al Dorrington wrote:

> Hi,
> 
> I am working on a proof of concept project where we are going to try moving an
> application that runs on VxWorks to Linux. I believe with what I've read on this
> mailing list, and the RTwiki site that Linux is definitely up to the task with
> these kernel patches.
> 
> However, I am not really sure which distribution of Linux we should use as the
> base, nor am I sure if it would be better to stick with the 'i386' distribution
> or go with the x86_64 variant.
> 
> I am considering Fedora 10, either i386 or x86_64. 
> 
> Does anyone have any comments or recommendations for which might be better to
> use, or if we would be better off using another distribution?

We have the preempt-rt kernels running on various distros and I can't
tell a difference. It's up to your personal preference.

32 vs. 64bit: if your cpu has 64 bit then using a 64bit distro is the
natural choice, but it works with 32bit equally well.

Thanks,

	tglx

Re: Fedora 10 as basis for RT?

[Mark Knecht]

On Thu, Apr 9, 2009 at 6:49 AM, Al Dorrington
<albert.dorrington@lmco.com> wrote:
> Hi,
>
> I am working on a proof of concept project where we are going to try moving an
> application that runs on VxWorks to Linux. I believe with what I've read on this
> mailing list, and the RTwiki site that Linux is definitely up to the task with
> these kernel patches.
>
> However, I am not really sure which distribution of Linux we should use as the
> base, nor am I sure if it would be better to stick with the 'i386' distribution
> or go with the x86_64 variant.
>
> I am considering Fedora 10, either i386 or x86_64.
>
> Does anyone have any comments or recommendations for which might be better to
> use, or if we would be better off using another distribution?
>
> Thanks!
> - Al Dorrington
>

I personally don't think the distro is all that important in this
respect. I'd pick the distro based on other things like how it gets
installed, how does it's package management, how often you want to
update it, whether you want configuration through GUI apps or whether
you're comfortable working at the command line, and probably most
important how well the user lists are run and whether the folks who
answer questions tend to be gentle or demanding.

I run the rt-kernel on Gentoo and have had relatively great success. I
don't know of any distro that won't run it, and if there is one then I
suspect that the rt-devel team would want to know that. I'm sure
Fedora is a well tested distro. The PlanetCCRMA audio distro is
Fedora-based and it has always worked pretty well.

As for i386 vs x86_64 my only input would be that if your app needs to
interface to a lot of Windows multimedia data then you're likely
better off with i386. I run the rt-kernel on both under Gentoo and
have an easier time with the i386 boxes decoding what are generally
Windows only media types.

Good luck with whatever decision you take.

Cheers,
Mark

Re: Fedora 10 as basis for RT?

[Al Dorrington]

Thank you for your quick responses! We had thought that the distribution and
32-bit/64-bit wouldn't be a major concern, but glad to have it confirmed by the
experts.

Re: Fedora 10 as basis for RT?

[Clark Williams]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Thu, 9 Apr 2009 13:49:29 +0000 (UTC)
Al Dorrington <albert.dorrington@lmco.com> wrote:

> Hi,
> 
> I am working on a proof of concept project where we are going to try moving an
> application that runs on VxWorks to Linux. I believe with what I've read on this
> mailing list, and the RTwiki site that Linux is definitely up to the task with
> these kernel patches.
> 
> However, I am not really sure which distribution of Linux we should use as the
> base, nor am I sure if it would be better to stick with the 'i386' distribution
> or go with the x86_64 variant.
> 
> I am considering Fedora 10, either i386 or x86_64. 
> 
> Does anyone have any comments or recommendations for which might be better to
> use, or if we would be better off using another distribution?
> 
> Thanks!
> - Al Dorrington
> 

I'm running the -rt kernel on F10 and it runs fine (both 32 and 64 bit
versions). That said, I expect any modern distro with an up-to-date
glibc will be perfectly fine for running an -rt Linux system.

I'd make my pick as to the arch based on how much memory you
anticipate stuffing into the system: more than 4GB, use 64-bit; less or
equal to 4GB, use what's native to the CPU. I generally use 64-bit
nowadays, but that's really just personal preference. Some folks still
claim that 32-bit is faster, but I haven't seen it.

Clark
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.10 (GNU/Linux)

iEYEARECAAYFAkneOSwACgkQHyuj/+TTEp25NwCgiXyzDtdvtWvXBT49CE93NVvo
XlwAn1XK01VkjxO3QbElqnlByeNEeuMD
=cc3f
-----END PGP SIGNATURE-----

Re: Fedora 10 as basis for RT?

[Darren Hart]

Al Dorrington wrote:
> Hi,
> 
> I am working on a proof of concept project where we are going to try moving an
> application that runs on VxWorks to Linux. I believe with what I've read on this
> mailing list, and the RTwiki site that Linux is definitely up to the task with
> these kernel patches.
> 
> However, I am not really sure which distribution of Linux we should use as the
> base, nor am I sure if it would be better to stick with the 'i386' distribution
> or go with the x86_64 variant.
> 
> I am considering Fedora 10, either i386 or x86_64. 
> 
> Does anyone have any comments or recommendations for which might be better to
> use, or if we would be better off using another distribution?

As far as the distro goes, the one caveat used to be making sure you had 
one with a recent enough glibc so you could take advantage of Priority 
Inheritance with the pthread mutexes and such.  That's pretty much no 
longer an issue, but FC10 does ship glibc2.9 which has the advantage of 
using PROCESS_PRIVATE futexes by default, which should give you slightly 
better performance in some situations.

-- 
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team

Re: Fedora 10 as basis for RT?

[Al Dorrington]

Ok - one more question about Fedora 10...

Fedora 10 uses the 2.6.27 kernel, looking at the patches available at the RT
kernel project site at kernel.org, I see patches for 2.6.26 and 2.6.29.

I am not sure what the correct way to integrate the RT patches at this point.
Are there alternate patch sites, or should I downgrade to 2.6.26 or upgrade to
2.6.29?

Thanks - Al

Re: Fedora 10 as basis for RT?

[Mark Knecht]

On Fri, Apr 10, 2009 at 10:28 AM, Al Dorrington
<albert.dorrington@lmco.com> wrote:
> Ok - one more question about Fedora 10...
>
> Fedora 10 uses the 2.6.27 kernel, looking at the patches available at the RT
> kernel project site at kernel.org, I see patches for 2.6.26 and 2.6.29.
>
> I am not sure what the correct way to integrate the RT patches at this point.
> Are there alternate patch sites, or should I downgrade to 2.6.26 or upgrade to
> 2.6.29?
>
> Thanks - Al
>

If it's your first time with the rt-kernel then you should download
the 3 file set that Thomas announces for each kernel. One thing you do
NOT want to do is mix and match in ways that the rt-developers don't
suggest. Note that the rt-kernel should always (AFAIK) be built only
against the kernel.org kernel with the same base revision number.

Here's a recent announcement:

<QUOTE>

We are pleased to announce the next update to our new preempt-rt
series.

       - include the futex rework + requeue_pi support (Darren Hart)

The futex changes need profound testing. As we know from prior futex
work the best stress tests for the futex interface are RT-Java-VMs
especially with enterprise work loads on larger machines. Can the
folks who have access to such monstrosities please unleash the beasts
and give the futex code a good work out ? Please tell your sysadmin
upfront that he should be stand by to fix up the resulting wreckage
which might vary from harmless to system replacement.

Unfortunately I was not able to track down the weird 32bit PAE
shutdown crash, so the affected users need to stick to the
nosmp-alternatives work around for now.

Download locations:

    http://rt.et.redhat.com/download/
    http://www.kernel.org/pub/linux/kernel/projects/rt/

Information on the RT patch can be found at:

    http://rt.wiki.kernel.org/index.php/Main_Page

to build the 2.6.29.1-rt5 tree, the following patches should be
applied:

    http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.29.1.tar.bz2
    http://www.kernel.org/pub/linux/kernel/projects/rt/patch-2.6.29.1-rt5.bz2

The broken out patches are also available at the same download
locations.

Enjoy !

      tglx

</QUOTE>