RealTime
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| ##(see the SpecSpec for an explanation) | == Realtime == |
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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.'' | '''Basic introduction is available at:'''<<BR>> [[https://help.ubuntu.com/community/UbuntuStudio/RealTimeKernel]] <<BR>><<BR>> For more a more in-depth look at kernels, please see: [[https://wiki.ubuntu.com/Kernel/Dev]] <<BR>><<BR>> '''News:''' <<BR>> The -preempt and -rt kernels are no longer being developed due to lack of support. Focus has instead turned to the -lowlatancy and -realtime kernels, particularly for the the release of Ubuntu 11.04 Natty Narwhal. The long-term goal is to have -lowlatency in the official Ubuntu repositories, while maintaining -realtime in a dedicated PPA.<<BR>><<BR>> If you wish to see work continued on -preempt or -rt, you are encouraged to volunteer. To do so, join the Ubuntu Studio Developers e-mail list (see [[http://ubuntustudio.org/|Ubuntu Studio]]). |
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| ## * '''Launchpad entry''': https://launchpad.net/distros/ubuntu/+spec/realtime * '''Created''': [[Date(2007-01-09T17:28:06Z)]] by AlessioIgorBogani * '''Contributors''': AlessioIgorBogani * '''Packages affected''': linux-source-2.6.20 |
'''Make-up of the team and rules officially assigned:''' ||Leader|| || ||i386 amd64||vacant|| ||Code & Packaging||Natty||-lowlatency||i386 amd64||Luke Yelavich|| ||Upstream relationship||Natty||-realtime||i386 amd64||Alessio Igor Bogani|| ||Bug triage|| || || ||vacant|| ||Kernel and DKMS external driver upload||Natty||-lowlatency||i386 amd64||Luke Yelavich|| ||Test||Lucid||fglrx on -realtime||i386||Brian David|| |
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| == Summary == | |
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| This specification details the plan to add hard real time support in Ubuntu. | '''Persons who would want help but not yet assigned to something:''' <<BR>> - Asmo Koskinen: Test on -rt on Maverick (AMD64 and i386) with nVidia, M-Audio Delta 66 and Echo Audio Fire 4 <<BR>> - Erik Rasmussen : Test on -rt <<BR>> - Mike Holstein : -realtime on Lucid <<BR>> - ailo : -rt on Maverick with nvidia <<BR>> - Brian David: Testing fglrx in all kernel variants, testing -realtime and -rt kernels, if available<<BR>> - Laurent Bellegarde: testing, advertising, conference, demonstration to large public <<BR>> - Tim Cook: test on -rt and Relationships with other communities <<BR>> - Jeremy Jongepier: Test and packaging on -rt/-realtime <<BR>> - Scott Lavender: testing, packaging, Ubuntu relations, and Studio relation about -lowlatency <<BR>> - Janne Jokitalo: Testing, packaging, Ubuntu and Ubuntu Studio relation, learning to generally tweak kernels <<BR>> |
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| == Rationale == | |
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| In some contexts (i.e. industrial automation, robotics and telco) the low-latency support is insufficient. In order to push Ubuntu in these contexts is necessary the support for high resolution timers and the full preemption in the Linux kernel. These features have been implemented by Thomas Gleixner and Ingo Molnar (http://people.redhat.com/mingo/realtime-preempt/). | '''Work in progress:''' <<BR>> Nvidia on -realtime kernel at Alessio's PPA: testers? <<BR>> |
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| We want also a valid FLOSS alternative to SLERT (http://www.novell.com/products/realtime/). | |
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| == Use cases == | '''Known issues:''' <<BR>> Missing a decent FAQ section <<BR>> ATI (fglrx): volunteers? <<BR>> Firewire audio devices: again volunteers? <<BR>> |
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| 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. | |
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| == Scope == | '''FAQ:''' <<BR>> Q: What is the difference between an -rt kernel and a -realtime kernel? |
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| This specification cover the linux kernel in Ubuntu. | A: From a technical point of view, -rt and -realtime are the same kernel. They are both based on the PREEMPT_RT patchset, although the version may be different. The main difference is that the -rt kernel should be based on the Ubuntu source tree (and therefore can use the same features, patches, enabled hardware, security fixes and so on) and should offer the same services that the Ubuntu default -generic kernel offers. For example, it should be compatible with closed video drivers (nvidia and fglrx), any external DKMS drivers, and have available backport packages. The goal of an -rt kernel is to obtain a real time variant of the Ubuntu kernel that is aligned with the -generic kernel. <<BR>><<BR>> On the other hand, the -realtime kernel is a PREEMPT_RT patched kernel based on the vanilla source tree (not the Ubuntu source). This kernel will be missing Ubuntu specific code, patches or security fixes and it isn't guaranteed to be compatible with any external software (low level utilities, DKMS drivers and so on). It does not use the same Linux kernel version as the -generic kernel, and so these two kernels are not aligned. It is a working, upstream real-time kernel that is being used on Ubuntu. No more no less. |
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| == Design == | {{{#!wiki comment |
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| == Implementation == | -lowlatency == -generic + more aggressive low latency kernel configuration It can offers all things that Ubuntu offer with -generic so -backport modules, video closed drivers and so on. It is very solid and oriented to "soft" users. Trade-off between low latency and power consumption. |
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| We hope to add a linux-image-realtime package in universe repositary (the same place of the linux-image-lowlatency package). | In less words: if you need of closed video drivers, external DKMS kernel modules, linux-backports-* you should probably start to use -lowlatency (when it will be available through Ubuntu repos). Instead if you really need of an real-time system you should avoid all above or trying to make those working alone. |
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| === Code === | |
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| === Data preservation and migration === | To put it simply: -lowlatency all the way! It delivers impressive results for maintenance requirements way lower than -realtime (or -rt even more), meaning less work for maintainers and new kernel candy for users. |
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| == Unresolved issues == | Life is a trade-off: someone want a very hard real-time system without adopt other hardware architectures than pc (MCU, FPGA/ASIC, and so on), others want use normal and cheap pc, others want use also accelerated drivers also, others want a real-system which take care of they laptop's batteries too. And at the end we have limited resources(*) for give an answer on these needs (we are all volunteers). |
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| == BoF agenda and discussion == | }}} |
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| ---- CategorySpec CategorySpec |
=== Ancient stuff === These wiki pages covers hard real time support in Ubuntu. [[RealTime/Feisty|RealTime Feisty]] <<BR>> [[RealTime/Gutsy|RealTime Gutsy]] <<BR>> [[RealTime/Hardy|RealTime Hardy]] <<BR>> [[RealTime/Intrepid|RealTime Intrepid]] <<BR>> [[RealTime/Jaunty|RealTime Jaunty]] <<BR>> [[RealTime/Karmic|RealTime Karmic]] <<BR>> [[RealTime/Lucid|RealTime Lucid]] The RT kernel is still around! If you can help by describing it's current state, please do so. In the mean time see the official [[http://rt.wiki.kernel.org|rt.wiki.kernel.org]] and the [[http://ubuntustudio.org/|Ubuntu Studio]] team for more information. |
Realtime
Basic introduction is available at:
https://help.ubuntu.com/community/UbuntuStudio/RealTimeKernel
For more a more in-depth look at kernels, please see: https://wiki.ubuntu.com/Kernel/Dev
News:
The -preempt and -rt kernels are no longer being developed due to lack of support. Focus has instead turned to the -lowlatancy and -realtime kernels, particularly for the the release of Ubuntu 11.04 Natty Narwhal. The long-term goal is to have -lowlatency in the official Ubuntu repositories, while maintaining -realtime in a dedicated PPA.
If you wish to see work continued on -preempt or -rt, you are encouraged to volunteer. To do so, join the Ubuntu Studio Developers e-mail list (see Ubuntu Studio).
Make-up of the team and rules officially assigned:
Leader |
|
|
i386 amd64 |
vacant |
Code & Packaging |
Natty |
-lowlatency |
i386 amd64 |
Luke Yelavich |
Upstream relationship |
Natty |
-realtime |
i386 amd64 |
Alessio Igor Bogani |
Bug triage |
|
|
|
vacant |
Kernel and DKMS external driver upload |
Natty |
-lowlatency |
i386 amd64 |
Luke Yelavich |
Test |
Lucid |
fglrx on -realtime |
i386 |
Brian David |
Persons who would want help but not yet assigned to something:
- Asmo Koskinen: Test on -rt on Maverick (AMD64 and i386) with nVidia, M-Audio Delta 66 and Echo Audio Fire 4
- Erik Rasmussen : Test on -rt
- Mike Holstein : -realtime on Lucid
- ailo : -rt on Maverick with nvidia
- Brian David: Testing fglrx in all kernel variants, testing -realtime and -rt kernels, if available
- Laurent Bellegarde: testing, advertising, conference, demonstration to large public
- Tim Cook: test on -rt and Relationships with other communities
- Jeremy Jongepier: Test and packaging on -rt/-realtime
- Scott Lavender: testing, packaging, Ubuntu relations, and Studio relation about -lowlatency
- Janne Jokitalo: Testing, packaging, Ubuntu and Ubuntu Studio relation, learning to generally tweak kernels
Work in progress:
Nvidia on -realtime kernel at Alessio's PPA: testers?
Known issues:
Missing a decent FAQ section
ATI (fglrx): volunteers?
Firewire audio devices: again volunteers?
FAQ:
Q: What is the difference between an -rt kernel and a -realtime kernel?
A: From a technical point of view, -rt and -realtime are the same kernel. They are both based on the PREEMPT_RT patchset, although the version may be different. The main difference is that the -rt kernel should be based on the Ubuntu source tree (and therefore can use the same features, patches, enabled hardware, security fixes and so on) and should offer the same services that the Ubuntu default -generic kernel offers. For example, it should be compatible with closed video drivers (nvidia and fglrx), any external DKMS drivers, and have available backport packages. The goal of an -rt kernel is to obtain a real time variant of the Ubuntu kernel that is aligned with the -generic kernel.
On the other hand, the -realtime kernel is a PREEMPT_RT patched kernel based on the vanilla source tree (not the Ubuntu source). This kernel will be missing Ubuntu specific code, patches or security fixes and it isn't guaranteed to be compatible with any external software (low level utilities, DKMS drivers and so on). It does not use the same Linux kernel version as the -generic kernel, and so these two kernels are not aligned. It is a working, upstream real-time kernel that is being used on Ubuntu. No more no less.
Ancient stuff
These wiki pages covers hard real time support in Ubuntu.
RealTime Feisty
RealTime Gutsy
RealTime Hardy
RealTime Intrepid
RealTime Jaunty
RealTime Karmic
RealTime Lucid
The RT kernel is still around! If you can help by describing it's current state, please do so. In the mean time see the official rt.wiki.kernel.org and the Ubuntu Studio team for more information.
RealTime (last edited 2011-02-23 10:51:46 by cache1)