Hardy

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 * '''Contributors''':  * '''Contributors''': PeterLJones
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This should provide an overview of the issue/functionality/change proposed here. Focus here on what will actually be DONE, summarising that so that other people don't have to read the whole spec. 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.
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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.		 ##== 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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This should cover the _why_: why is this change being proposed, what justifies it, where we see this justified. 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.
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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.

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...).

##Other use cases?

== Scope ==

This specification covers the rt linux kernel flavour in Ubuntu.
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== Design ==  * [wiki:KernelTeam/Hardy/KernelVersion Kernel Version]: 2.6.24?
 * [http://lwn.net/Articles/230501/ Scheduler] in stock kernel: CFS
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You can have subsections that better describe specific parts of the issue. ##== Design ==
##
##You can have subsections that better describe specific parts of the issue.
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== Implementation == ##== Implementation ==
##
##This section should describe a plan of action (the "how") to implement the changes discussed. Could include
##subsections like:
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This section should describe a plan of action (the "how") to implement the changes discussed. Could include subsections like: ##=== UI Changes ===
##
##Should cover changes required to the UI, or specific UI that is required to implement this
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=== UI Changes === ##=== Code Changes ===
##
##Code changes should include an overview of what needs to change, and in some cases even the specific details.
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Should cover changes required to the UI, or specific UI that is required to implement this ##=== 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.
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=== Code Changes === ##== Test/Demo Plan ==
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Code changes should include an overview of what needs to change, and in some cases even the specific details.

=== 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.		 ##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.
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##
##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.
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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).

== 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 pre-emption support (if any).
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Use this section to take notes during the BoF; if you keep it in the approved spec, use it for summarising what was discussed and note any options that were rejected. *) Team creation? [[BR]]
Collaboration with istant messaging, chat or mailing list?

*) 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.

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

*) RT Test suite? [[BR]]
Thomas Glexiner's rt-tests tools: http://git.kernel.org/?p=linux/kernel/git/tglx/rt-tests.git;a=summary

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]]


 * Any suggestions/feedbacks/requests? [wiki:AlessioIgorBogani Alessio] [[BR]][[BR]]

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

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.

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.

Assumptions

Outstanding Issues

  • How will -rt fare with the introduction of CFS, replacing O(1).

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 pre-emption support (if any).

BoF agenda and discussion

*) Team creation? BR Collaboration with istant messaging, chat or mailing list?

*) 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.

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

*) RT Test suite? BR Thomas Glexiner's rt-tests tools: http://git.kernel.org/?p=linux/kernel/git/tglx/rt-tests.git;a=summary

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 issuesBR 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

CategorySpec

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