[linux-audio-user] Ingo's RT patch: please tell this newbie the best jack settings

Mark Knecht markknecht at gmail.com
Mon Nov 14 21:09:23 EST 2005

On 11/14/05, thewade <pdman at aproximation.org> wrote:
>  > 1) The current kernel from Ingo would be 2.4.16-rt9. I think that rt5
>  > didn;t last very long and had some problems. Please try -rt9.
> OK, will do.

Since the time I wrote this the -rt kernel has moved to 2.6.14-rt12.
As 2.6.14 stable has moved to (or .3?) and the 2.6.15-rc1
candidate is out I expect that Ingo will release something new
shortly. None the less I am using 2.6.14-rt12 today. -rt9 is fine

>  > 2) Make sure you reinstall the realtime-lsm package after building
> that kernel.
> If I remember correctly this also included a PAM patch: does it still?
> I will investigate.

My information may possibly cause you a little heartburn. You are used
to using RPMs and basically the tools available through the Planet. I
am Gentoo based and am more used to using source code. I do not know
exactly how these two are going to mix, other than to say that either
is probably fine but mixing the two too much is posibly not a good
idea. I think it is fine to build your own kernel and the realtime-lsm
package on a Planet box. I used to do that when I used the Planet. I
do not recommend that a new user go any further than that as problem
may occur.

>  > 4) Making best use of the kernel requires that you understand the ISR
>  > number for your sound card and reset it's priority higher. This helps
>  > a lot in reducing or eliminating xruns.
> How does one control the IRQ number of the device? I thought this was
> determined by the hardware.
> Can you point me to a URL so that I might learn more? (I dont really
> know what terms to search for)

Do not worry about this until you are running 2.6.14-rt9/rt12. Deal
with it ONLY when you have that kernel running. We'll direct you at
the proper time.

>  > 7) Make sure you have the Jack FIFOS mounted on tmpfs.
> Of course!
>  > As a comment, I don't personally like Jack in /usr local. You might
>  > consider rebuilding Jack one of these days with:
>  >
>  > ./configure --prefix=/usr
> I was using a modified jack.spec file from the CVS distro of jack. I
> will change my version but perhaps I should suguest this change to the
> jack people as well?

Well, I think .spec files mean you are using RPMs? Again, I don't do
this. I download CVS and build the source code. I do not know what the
.spec file is going to do so I cannot help there.

If you want to build the executable directly from the CVS code then I can help.

>  > Hope this all helps a bit,.
> It does very much! I didnt really realize that the LSM module ran on top
> of the rt patch!

Realtime-lsm runs on top of ALL later revisions of the 2.6 kernel.
Certainly it works for any 2.6.13 or higher kernel. All that is
required is that you enable certain security features when you build
your kernel.

> Does your kernel have Default linux capabilities enabled? I cannot
> remember if this is supposed to be on or off with the LSM module...

It must be on as a module.

> Thanks for the help Mark!

You are welcome.


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