RealTime

Revision 43 as of 2007-04-10 17:03:53

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Please check the status of this specification in Launchpad before editing it. If it is Approved, contact the Assignee or another knowledgeable person before making changes.

Summary

This specification details the plan to add hard real time support in Ubuntu.

Rationale

In some contexts (i.e. industrial automation, robotics and telco) the low-latency support is insufficient. In order to push Ubuntu in these contexts it is necessary to add support for high resolution timers and full preemption in the Linux kernel. These features have been implemented by Thomas Gleixner and Ingo Molnar (http://people.redhat.com/mingo/realtime-preempt/).

We also want a valid FLOSS alternative to SLERT (http://www.novell.com/products/realtime/).

Use cases

Alex is developing an application software (SCADA type) for a customer and he would be very happy to use Linux and Ubuntu for the deployment.

Real time audio support in a radio station studio (http://postscriptumradio.org), which needs RT preemption to satisfy real time features of jack audio connection kit by Paul Davis.

Scope

This specification covers a new linux kernel flavour (-realtime) in Ubuntu.

Beta available

Add, as root, to your /etc/apt/sources.list (remember to do a backup of this file) the following line: 

deb http://www.texware.it/ubuntu feisty/

Then execute: 

wget -q http://www.texware.it/ubuntu/feisty/BBA3222D.gpg -O- | sudo apt-key add -
sudo apt-get update
sudo apt-get install linux-realtime

Packages available:

linux-realtimeBR linux-image-realtimeBR linux-image-2.6.20-13-realtime (2.6.20-rt8)BR linux-image-2.6.20-14-realtime (2.6.20-rt8)BR cyclictest

Patch is available at:

[http://www.texware.it/ubuntu/feisty/Ubuntu-2.6.20-13.21-realtime.diff Ubuntu-2.6.20-13.21-realtime.diff] BR [http://www.texware.it/ubuntu/feisty/Ubuntu-2.6.20-14.22-realtime.diff Ubuntu-2.6.20-14.22-realtime.diff] [http://www.texware.it/ubuntu/feisty/debian-14.22.patch debian-14.22.patch] BR

FAQ

Q) Did you manage to include all the regular Ubuntu kernel patches in it? If not, is it possible to know what was left out? BR A) No i don't include anything because i use _only_ full Ubuntu Kernel (not vanilla, not custom version or other). Ubuntu Realtime kernel is Ubuntu kernel plus realtime preemption patch. Also the configuration (aka /boot/config*) is the same expects for specific realtime options.

Q) Where i cand find documentation? BR A) All existing docs are available on http://rt.wiki.kernel.org

Todo

Linux image debug versionBR Linux image trace version (with wakeup and latency trace options enabled) BR Restricted modules package (when kernel in Feisty is freeze)BR Amd64 kernel version (any volunteer?)BR

BoF agenda and discussion

  • Any suggestion/feedbacks/requests? [wiki:AlessioIgorBogani alessio] BRBR

  • I can host the packages on my repo if bandwith is necessary [wiki:Ttoine ttoine] BRBR

  • I confirm that it seems to rock for music production, jack like it; will do my best to have it in the next Ubuntu Studio, hope that we will have the restricted modules packages for full opengl support, etc... [wiki:Ttoine ttoine] BRBR

  • Talk to /MOTU/Teams/Audio seems they are duplicating the load with a low latency audio kernel. Frink BRBR

Wow Alessio, you've really moved ahead with this. Smile :) Awesome. I would like to talk with you about Ubuntu Studio using this in our distro. This will get you alot of feedback to help make the kernel better as well as get our users a proper kernel.

For us to use it though we need to know some details. Please email me at coryisatmATubuntuDOTcom or hop on our IRC channel on Freenode #ubuntustudio.

I'd like to get you involved with the Ubuntu community so everyone can benefit from your great work. Smile :) -CKontros

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