2.6 Kernel & real-time q's

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malrost
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Joined: 2006-05-23
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I'd been using Ingo Molnar's real-time kernel patch on a 2.4 kernel with my audio apps, mainly Ardour w/ jack.

I am coming across conflicting information on the real time capabilities of the 2.6 kernel (real time but not "true" real time...?)

To move to a 2.6 kernel, can I use the default kernel and get real time access? Or, will I still need to use the a patch build it from source or with specific options?

Thanks!

paul
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Joined: 2006-03-16
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1) vanilla 2.6.X (for X > 14) is massively better than vanilla 2.4

2) Ingo-patched 2.6 is better than Ingo-patch 2.4

3) realtime access on 2.6 systems now relies on the kernel rlimits mechanism. this means that you need not just the right kernel, but the right user space utilities (specifically PAM on those systems that use PAM for user login). i wish i could cite a specific version for you, but i cannot right now. if you have the correct version of PAM, then if the distro has not already patched it, you edit the file /etc/security/limits.conf to include these two lines:

@audio - memlock unlimited
@audio - rtprio 90

then add yourself to a group called "audio" and login again.

the best advice is to use a modern distro such as ubuntu or FC6 that is keeping up to date with all this. if you use Fedora, you can get prebuilt kernels directly from ingo's own yum repository - its great.

malrost
User offline. Last seen 7 years 1 week ago. Offline
Joined: 2006-05-23
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Gotcha on 1 & 2, and looks like I need to read up a little on user space utilities, PAM, and the /etc/security/limits.conf man page to get up to speed on your point #3.

I appreciate your help!