Hardy

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##== Release Note ==
##
##This section should include a paragraph describing the end-user impact of this change. It is meant to be included
##in the release notes of the first release in which it is implemented. (Not all of these will actually be included
##in the release notes, at the release manager's discretion; but writing them is a useful exercise.)
##
##It is mandatory.
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##Other use cases?
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### == Assumptions == == Implementation ==
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## * [wiki:KernelTeam/Hardy/KernelVersion Kernel Version]: 2.6.24?
## * [http://lwn.net/Articles/230501/ Scheduler] in stock kernel: CFS		 We will use the new kernel build system created by the Ubuntu Kernel Team for production kernel: [http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-hardy.git;a=blob;hb=HEAD;f=debian/binary-custom.d/README More information about it]. Debug version and rt-tests packages will be released through [https://help.launchpad.net/PPAQuickStart PPA] of the [https://launchpad.net/~ubuntu-rt RealTime Team].
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##== Design ==
##
##You can have subsections that better describe specific parts of the issue.		 We use [wiki:KernelGitGuide Git] for handle kernel source code and [http://savannah.nongnu.org/projects/quilt Quilt] for handle the preempt-rt one.
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##== Implementation ==
##
##This section should describe a plan of action (the "how") to implement the changes discussed. Could include
##subsections like:		 Other utilities as like [[http://rt.wiki.kernel.org/index.php/Preemption_Test Preemption test]] or [[http://devresources.linux-foundation.org/craiger/hackbench/ hackbench]] are postponed to hardy+1. It is the same for integration with PolicyKit (framework for secure privilege elevation integration) and for RT related documentation due to lack of interest.
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##=== UI Changes ===
##
##Should cover changes required to the UI, or specific UI that is required to implement this		 == Outstanding Issues ==
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##=== Code Changes ===
##
##Code changes should include an overview of what needs to change, and in some cases even the specific details.		 1. High precision timers don't work on machine which have only PIT as souce clock [http://www.mail-archive.com/linux-rt-users@vger.kernel.org/msg00375.html more info] [[BR]]
2. The realtime kernel could expose you to security issues (probably local only) [[BR]]
3. Restricted modules increase latencies (please buy only hardware which have a free driver!) [[BR]]
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##=== Migration ===
##
##Include:
## * data migration, if any
## * redirects from old URLs to new ones, if any
## * how users will be pointed to the new way of doing things, if necessary.

##== Test/Demo Plan ==

##It's important that we are able to test new features, and demonstrate them to users. Use this section to describe a
##short plan that anybody can follow that demonstrates the feature is working. This can then be used during CD
##testing, and to show off after release.
##
##This need not be added or completed until the specification is nearing beta.

### == Outstanding Issues ==
##
##This should highlight any issues that should be addressed in further specifications, and not problems with the
##specification itself; since any specification with problems cannot be approved.

## * How will -rt fare with the introduction of CFS, replacing O(1).		 == Packages available ==
Packages available in Hardy archives: [[BR]]
###linux-rt
###linut-image-rt
linux-image-2.6.24-2-rt [[BR]]
###linux-ubuntu-modules-2.6.24-XX-rt
###linux-headers-rt
linux-headers-2.6.24-2-rt [[BR]]
###linux-restricted-modules-rt
###linux-restricted-modules-2.6.24-XX-rt
###linux-backports-modules-rt
###linux-backports-modules-2.6.24-XX-rt
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A) A simple adaptation to the BenC's kernel git tree isn't the only difference: We work on Ubuntu specific code or drivers (aka linux-ubuntu-modules/linux-restricted-modules) and also remove all code which isn't strictly related to real-time pre-emption support (if any). A) A simple adaptation to the BenC's kernel git tree isn't the only difference: We work on Ubuntu specific code or drivers (aka linux-ubuntu-modules/linux-restricted-modules) and also remove all code which isn't strictly related to real-time preemption support (if any).
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A) (I belive there is no Git repository. The best way is, I guess, get the Ubuntu kernel from the Git repository at http://kernel.ubuntu.com and then apply the patch from Ingo Molnar. Is there a patch package? Alessio, could you please elaborate on this?) A) Sure! You can find it at [http://kernel.ubuntu.com/git Ubuntu Kernel Team's Git Repositories].
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*) Team creation? [[BR]]
Collaboration with instant messaging, chat or mailing list? [[BR]]
    I would prefer using a mailing list for team collaboration. [[wiki:DeraldWoods Derald]] [[BR]]
    Ideally a forum; else a mailing list; else a permanent, logged IRC chat room. [[wiki:PeterLJones Peter]] [[BR]]
    I actually prefer a mailing list but a forum would also be OK. [[wiki:miguel Miguel]] [[BR]]
    I would prefer mailing list but IRC Chat root is also useful for me. [[wiki:AlessioIgorBogani Alessio]]

*) PolicyKit, framework for secure privilege elevation integration, seems which became default in Hardy. Investigate on possible integration. [[BR]]

*) Backport of the last upstream code? [[BR]]
It is necessary define a tool/method to track rt development and thus eventually backport useful bits.

 * Packaging the '''rt-tests''' utilities. [[http://rt.wiki.kernel.org/index.php/Cyclictest cyclictest/signaltest]] [[http://rt.wiki.kernel.org/index.php/Preemption_Test preemption test]] [[http://devresources.linux-foundation.org/craiger/hackbench/ hackbench]]

*) Debug packages? [[BR]]
See at https://blueprints.launchpad.net/ubuntu/+spec/daily-kernel-builds

There are some other test applications on http://rt.wiki.kernel.org that could also be integrated in a future test suite. And, of course, this test suite could be executed daily, integrated in the daily-kernel-builds referred above. [[wiki:miguel Miguel]]

In this way you testing realtime performance of the buildd server (the Ubuntu server that compile kernel). Testing is a very useful things but it is necessary find an other way for do it. [[wiki:AlessioIgorBogani Alessio]]

*) RT documentation? [[BR]]
I believe that it would be necessary to have some documentation package, at least for application developers. As a starting point, the documentation in the http://rt.wiki.kernel.org could be used but I think that something for newcomers should also be written (in cooperation with the http://rt.wiki.kernel.org maintainers, of course).

Good suggestion! [[wiki:AlessioIgorBogani Alessio]]

Need to review: [[BR]]
1. High precision timers don't work on machine which have only PIT as souce clock [http://www.mail-archive.com/linux-rt-users@vger.kernel.org/msg00375.html more info] [[BR]]
2. The realtime kernel could expose you to security issues[[BR]]
3. On some machine esd with realtime kernel freeze GNOME (please kill esd and relaunch it after)[[BR]]
4. Restricted modules could increase latencies (please buy only hardware which have a free driver!) [[BR]]
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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 improve hard real time support in Ubuntu Hardy. In particular, to comply with quality levels that users want from an LTS release.

Rationale

In order to push Ubuntu in very highly demanding business (e.g. industrial automation, financial, robotics, advanced multimedia and telco) and other contexts, it is necessary to improve real-time kernel flavour support.

Use Cases

1. Deterministic (Hard-Realtime) [Industrial Control, Robotics, Automation, DAQ, etc.]BR

  • Alex is developing an application ([http://en.wikipedia.org/wiki/SCADA SCADA] type) for a customer and he would be very happy to use Linux and Ubuntu for the deployment.

  • John is using the Ubuntu distribution, with the linux-rt kernel, as the RTOS, for a GANTRY type widget assembly application. The system has digital I/O, servo motors, and GPIB instrumentation.

2. Non-Deterministic (Low-Latency) [Data Sampling, Analysis Tools, Realtime Monitoring, etc.]BR

  • Beth is a user wanting application stability but with real-time performance capability for running Audio and MIDI applications (such as [http://jackaudio.org/ JACK] and its clients). This could include running a full [http://www.x.org X]/[http://www.gtk.org Gtk] UI stack with [http://www.winehq.com WINE] and/or [http://www.joebutton.co.uk/fst/ FST], with networking to allow for collaborative performances (e.g. [http://ninjam.com NINJAM]). Stability: must be reliable enough for live performance (system hangs look terribly unprofessional). Performance: no dropped MIDI messages (hanging notes suck...), no dropped audio frames (audio glitches suck...).

Scope

This specification covers the rt linux kernel flavour in Ubuntu.

Implementation

We will use the new kernel build system created by the Ubuntu Kernel Team for production kernel: [http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-hardy.git;a=blob;hb=HEAD;f=debian/binary-custom.d/README More information about it]. Debug version and rt-tests packages will be released through [https://help.launchpad.net/PPAQuickStart PPA] of the [https://launchpad.net/~ubuntu-rt RealTime Team].

We use [wiki:KernelGitGuide Git] for handle kernel source code and [http://savannah.nongnu.org/projects/quilt Quilt] for handle the preempt-rt one.

Other utilities as like http://rt.wiki.kernel.org/index.php/Preemption_Test Preemption test or http://devresources.linux-foundation.org/craiger/hackbench/ hackbench are postponed to hardy+1. It is the same for integration with PolicyKit (framework for secure privilege elevation integration) and for RT related documentation due to lack of interest.

Outstanding Issues

1. High precision timers don't work on machine which have only PIT as souce clock [http://www.mail-archive.com/linux-rt-users@vger.kernel.org/msg00375.html more info] BR 2. The realtime kernel could expose you to security issues (probably local only) BR 3. Restricted modules increase latencies (please buy only hardware which have a free driver!) BR

Packages available

Packages available in Hardy archives: BR

linux-image-2.6.24-2-rt BR

linux-headers-2.6.24-2-rt 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) We use _only_ the full Ubuntu Kernel (not vanilla, not custom version or other). The Ubuntu Realtime kernel is the Ubuntu Kernel plus the real-time pre-emption patch. Also the configuration (aka /boot/config*) is the same except for specific real-time options.

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

Q) What are the differences from vanilla Ingo Molnar's patch? BR A) A simple adaptation to the BenC's kernel git tree isn't the only difference: We work on Ubuntu specific code or drivers (aka linux-ubuntu-modules/linux-restricted-modules) and also remove all code which isn't strictly related to real-time preemption support (if any).

Q) What features will be included in Ubuntu rt kernel flavour? BR A) CPU shielding, priority inheritance, sleeping spinlocks, interrupt threads and high-resolution timers and CFS optimizations.

Q) How to get the source code? Is there a Git repository? BR A) Sure! You can find it at [http://kernel.ubuntu.com/git Ubuntu Kernel Team's Git Repositories].

BoF agenda and discussion

CategorySpec

RealTime/Hardy (last edited 2008-11-07 15:34:02 by d83-183-69-42)