LITMUS RT: Linux Testbed for Multiprocessor Scheduling in Real-Time Systems

Date: Wed, 19 May 2010 12:07:15 -0400 Subject: Revert "Revert back Bjoern's changes and added scons -h option" This reverts commit 500804f9b4a81e9cf18f3a42f966cad3d241c793. --- index.html | 1085 ++++++++++++++++++++++++++++++------------------------------ 1 file changed, 542 insertions(+), 543 deletions(-) diff --git a/index.html b/index.html index 2116e9c..bb6c026 100644 --- a/index.html +++ b/index.html @@ -1,543 +1,542 @@ - - - - - - - - LITMUS RT: Linux Testbed for Multiprocessor Scheduling in Real-Time Systems - - -

- Dr. James H. Anderson & - Students, - The University of North Carolina at Chapel Hill -

- -

- about - - support - - collaborators - - publications - - download - - installation - - documentation -

- -

About

- The LITMUS^RT project is a soft real-time extension of the Linux - kernel with focus on multiprocessor real-time scheduling and - synchronization. The Linux kernel is modified - to support the sporadic task - model and modular scheduler plugins. Both partitioned and global scheduling - is supported. -

Goals

- The primary purpose of the LITMUS^RT project is to provide a useful experimental platform for applied real-time systems research. In that regard, LITMUS^RT provides abstractions and interfaces within the kernel that simplify the prototyping of multiprocessor real-time scheduling and synchronization algorithms (compared to modifying a "vanilla" Linux kernel). As a secondary goal, LITMUS^RT serves as a proof of concept, showing that algorithms such as PFAIR can be implemented on current hardware. Finally, we hope that parts of LITMUS^RT and the "lessons learned" may find value as blueprints/sources of inspiration for other (both commercial and open source) implementation efforts. -

Non-Goals

- LITMUS^RT is not a production-quality system, and we have currently no plans to turn it into one. LITMUS^RT is not "stable," i.e., interfaces and implementations may change without warning between releases. POSIX-compliance is not a goal; the LITMUS^RT-API offers alternate system call interfaces. While we aim to follow Linux-coding guidelines, LITMUS^RT is not targeted at being merged into mainline Linux. Rather, we hope that some of the ideas protoyped in LITMUS^RT may eventually find adoption in Linux. -

Current Version

- The current version of LITMUS^RT is 2010.1 and is based on Linux 2.6.32. - It was released on 05/12/2010 and includes plugins for the following - scheduling policies: -

Partitioned EDF with synchronization support (PSN-EDF)
Global EDF with synchronization support (GSN-EDF)
Clustered EDF (C-EDF)
PFAIR (both staggered and aligned quanta are supported)

- Please refer to the download and installation sections for details. -

Earlier versions based on Linux 2.6.24 and Linux 2.6.20, - which supported additional scheduling policies, are discussed on separate pages dedicated to the LITMUS^RT 2008 and LITMUS^RT 2007 series respectively. -

- The first version of LITMUS^RT, which was implemented in Spring 2006, - is based on Linux 2.6.9. -

Development Plans

- There are plans to port LITMUS^RT to PowerPC and ARM platforms. Please contact us for details. -

Support

- The LITMUS^RT development effort is being supported by grants from - AT&T, IBM, and Northrop Grumman Corps.; the National Science Foundation (grants CNS 0834270 and CNS 0834132); the U.S. - Army Research Office (grant W911NF-09-1-0535); and the Air Force Office of Scientific Research (grant FA 9550-09-1-0549). -

- -

Collaborators

The LITMUS^RT project is led by Dr. James H. Anderson. -

- The implementation effort is carried out by students of the - Real-Time Systems - Group at the University of North Carolina - at Chapel Hill: -

- Björn B. Brandenburg (current maintainer) -
Andrea Bastoni (University of Rome "Tor Vergata") -

- Additional collaborators contributed to the previous LITMUS^RT 2008 and the LITMUS^RT 2007 versions. -

- - -

Publications

- -

- B. Brandenburg and J. Anderson, - “On the Implementation of Global Real-Time - Schedulers”, Proceedings of the 30th IEEE Real-Time Systems Symposium, pp. 214-224, December 2009. - Postscript. - PDF. - Longer version with all graphs: - Postscript. - PDF. -
-
For reference, all evaluated plugins are provided as part of the following patch (against version 2008.3). -
-
- - litmus-rt-RTSS09.patch -
- -
-
- B. Brandenburg and J. Anderson - “Reader-Writer Synchronization for Shared-Memory Multiprocessor Real-Time Systems”, - Proceedings of the 21st Euromicro Conference on Real-Time Systems, pp. 184-193, July 2009. - Postscript. PDF. - Long version with blocking terms: - Postscript. PDF. -
-
-
- J. Calandrino and J. Anderson - “On the Design and Implementation of a Cache-Aware Multicore Real-Time Scheduler”, - Proceedings of the 21st Euromicro Conference on Real-Time Systems, pp. 194-204, July 2009. - Postscript. PDF. -
-
-
- M. Mollison, B. Brandenburg, and J. Anderson - “Towards Unit Testing Real-Time Schedulers in LITMUS^RT”, - Proceedings of the Fifth International Workshop on Operating Systems Platforms for Embedded Real-Time Applications, pp. 33-39, July 2009. - Postscript. PDF. -
-
-
- B. Brandenburg and J. Anderson, - “A Comparison of the M-PCP, D-PCP, and FMLP on LITMUS^RT”, - Proceedings of the 12th International Conference on Principles of Distributed Systems, pp. 105-124, December 2008. - Postscript. PDF. -
-
-
- B. Brandenburg, J. Calandrino, and J. Anderson, - “On the Scalability of Real-Time Scheduling Algorithms on Multicore Platforms: A Case Study”, - Proceedings of the 29th IEEE Real-Time Systems Symposium, - pp. 157-169, December 2008. - Postscript. PDF. -
-
-
- B. Brandenburg and J. Anderson, - “An Implementation of the PCP, SRP, D-PCP, M-PCP, - and FMLP Real-Time Synchronization Protocols in LITMUS^RT”, - Proceedings of the 14th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, pp. 185-194, August 2008. - Postscript. PDF. -
-
Note: The work described in this paper took part in a branch that is currently not part of - the main distribution. For reference, we provide the branch as a separate download: -
-
- - litmus-rt-RTCSA08.patch -
- - liblitmus-RTCSA08.tgz -
- SHA256 check sums -
-
Please don't use this version for active development. If you are interested in this work, it would be best - to first port the desired features to a current version of LTIMUS^RT and merge them into the main distribution. -
- -
-
- A. Block, B. Brandenburg, J. Anderson, - and S. Quint, “An Adaptive Framework for Multiprocessor Real-Time Systems”, - Proceedings of the 20th Euromicro Conference on Real-Time Systems, pp. 23-33, July 2008. - Postscript. PDF. -
-
-
- B. Brandenburg, J. Calandrino, A. Block, - H. Leontyev, and J. Anderson, “Real-Time Synchronization - on Multiprocessors: To Block or Not to Block, to Suspend or - Spin?”, Proceedings of the 14th IEEE Real-Time and Embedded -Technology and Applications Symposium, pp. 342-353, April 2008. - Postscript. PDF. -
-
- Extended version, including all graphs: - Postscript, - PDF. -
-
-
- B. Brandenburg, A. Block, J. Calandrino, U. Devi, H. Leontyev, and J. Anderson, - "LITMUS^RT: A Status Report", Proceedings of the 9th - Real-Time Linux Workshop, pp. 107-123, November 2007. - Postscript. - PDF. -
-
-
- B. Brandenburg and J. Anderson, "Integrating Hard/Soft Real-Time Tasks - and Best-Effort Jobs on Multiprocessors", Proceedings of the 19th Euromicro - Conference on Real-Time Systems, pp. 61-70, July 2007. - Postscript, - PDF. -
-
-
- J. Calandrino, H. Leontyev, A. Block, U. Devi, and J. Anderson, - "LITMUS^RT: A Testbed for Empirically Comparing Real-Time - Multiprocessor Schedulers ", Proceedings of the 27th IEEE Real-Time Systems - Symposium, pp. 111-123, December 2006. - Postscript, - PDF. -
-

- -

Download

- The source code of LITMUS^RT is made available as open source - under the terms of the GNU - General Public License (GPL). -

- The current release of LITMUS^RT is 2010.1. - It consists of our Linux kernel modifications in the form of - a patch against Linux 2.6.32 and - - liblitmus, the user-space API for real-time - tasks, as well as ft_tools, a collection of tools - used for tracing with Feather-Trace (which is part of the LITMUS^RT patch). -

- -

LITMUS^RT 2010.1

- Based on Linux 2.6.32. Released in May 2010. - -

Files:

Major changes (since LITMUS^RT 2008.3):

TO BE UPDATED -

- Changed codebase from Linux 2.6.24 to Linux 2.6.32 -
Several bugfixes.

- -

- Please note that the current implementation is a prototype with - certain limitations. Most notably, it is not secure in a multiuser context, - i.e., real-time system calls do not require superuser - privileges. -

- -

- - Older releases: LITMUS^RT 2008 series, LITMUS^RT 2007 series. -

- -

- - - -

Installation

- The current release of LITMUS^RT consists of an - extension of the Linux kernel that adds support for the sporadic task - model, a scheduler plugin infrastructure, and some scheduler plugins, as - well as a user-space library that provides the LITMUS^RT - real-time API. Note that the current implementation only works on the - Intel x86-32 and x86-64 architectures. -

Patching the Kernel

- The extension to the Linux kernel is released as a patch against Linux - 2.6.32. To install the LITMUS^RT kernel, first download the Linux - kernel 2.6.32 and untar it in a directory of your choice (hereafter - referred to as $DIR). Second, apply the - LITMUS^RT patch (see Section Download) - and configure, compile, and install the kernel as usual. The patch is -p1 applicable. - To summarize, the LITMUS^RT kernel can be obtained, patched, and - compiled with the following commands: -

-cd $DIR
-# get Linux 2.6.32
-wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.32.tar.bz2
-tar xjf linux-2.6.32.tar.bz2
-wget http://www.cs.unc.edu/~anderson/litmus-rt/download/2010.1/litmus-rt-2010.1.patch
-mv linux-2.6.32 litmus2010
-# apply the LITMUS RT patch
-cd litmus2010
-patch -p1 < ../litmus-rt-2010.1.patch
-# create a working kernel configuration
-#  - select HZ=1000
-#  - enable in-kernel preemptions
-#  - disable NO_HZ
-#  - don't use power management options like frequency scaling
-#  - disable support for group scheduling
-make menuconfig
-# compile the kernel
-make bzImage
-make modules
-# proceed to install kernel, build initrd, etc.
-...
-

- When configuring the kernel, note that there is a menu (at the very end of the list) - with LITMUS^RT-specific configuration options. For reference, we provide sample 32-bit and 64-bit configurations that are known to work under QEMU. -

- -

Libraries

- The user-space library for real-time tasks, liblitmus, - depends on the LITMUS^RT kernel kernel and provides its own build system (based on scons). - In order to compile liblitmus, you need to adjust the - variable LITMUS_KERNEL in the SConstruct file to point to your - copy of the kernel. Users should not update the SConstruct file manually anymore. Instead, a .config file can be created with appropriate variables. The required variables can be listed using scons -h command. This command lists the variables required for building the liblitmus2010 library.
- Sample output of scons -h is as shown below. -

-scons -h
-scons: Reading SConscript files ...
-scons: done reading SConscript files.
-
-=============================================
-liblitmus --- The LITMUS^RT Userspace Library
-
-There are a number of user-configurable build
-variables. These can either be set on the
-command line (e.g., scons ARCH=x86) or read
-from a local configuration file (.config).
-
-Run 'scons --dump-config' to see the final
-build configuration.
-
-Build Variables
----------------
-
-LITMUS_KERNEL: Where to find the LITMUS^RT kernel. ( /path/to/LITMUS_KERNEL )
-    default: ../litmus2010
-    actual: ../litmus2010
-
-PYTHON_HEADERS: Where to find Python headers. ( /path/to/PYTHON_HEADERS )
-    default: /usr/include/python2.5
-    actual: /usr/include/python2.5
-
-ARCH: Target architecture. (x86_64|sparc64|x86|i686)
-    default: x86_64
-    actual: x86_64
-
-WSS: Working set size for pm analysis
-    default: 3072
-    actual: 3072
-
-Use scons -H for help about command-line options.
-

- -

- To summarize, the liblitmus can be obtained and - compiled with the following commands: -

- -

-cd $DIR
-wget http://www.cs.unc.edu/~anderson/litmus-rt/download/2010.1/liblitmus-2010.1.tgz
-tar xzf liblitmus-2010.1.tgz
-cd liblitmus
-
-# set LITMUS_KERNEL in .config to point to the kernel source and compile
-scons
-

- Please refer to the documentation on how to use the LITMUS^RT - real-time API as provided by liblitmus. -

- -

- - -

Documentation

- -

- Unfortunately, most of the documentation has yet to be written. To get an overview of - the architecture of the kernel extension, we recommend reading the paper - “LITMUS^RT: - A Status Report”. -

Real-Time Scheduling Policies

- The kernel contains the following real-time scheduling policy implementations: -

- PFAIR, an implementation of the PD² algorithm, -
- PSN-EDF, a partitioned EDF (P-EDF) implementation with support for the real-time synchronization protocol - FMLP, -
- GSN-EDF, a global EDF (G-EDF) implementation with support for the real-time synchronization protocol - FMLP, -
- C-EDF (Clustered EDF), a hybrid of G-EDF and P-EDF, and -
- Linux, a placeholder policy that disables all real-time functionality added by the LITMUS^RT patch. -

- Only one policy can be active at any time. Initially (i.e., during and after boot), the "Linux" policy is active. - You can use the tool showsched (part of liblitmus) to display - the name of the currently active policy. -

Changing the Active Policy

- You can use the tool setsched (part of liblitmus) - to select a new plugin at run time. -

- Only root can change the active policy, and only when there are no real-time tasks present. -

- If you do not have the dialog utility installed, then you can still use setsched by passing the desired scheduling policy as a commandline parameter, e.g. type setsched PFAIR to activate the PFAIR plugin. -

Writing Real-Time Tasks

- The user space library that provides the LITMUS^RT API, - liblitmus, contains two example real-time tasks - (base_task.c and - base_mt_task.c) - that both illustrate how to use the API and provide a skeleton for real-time - task development. To get started with development, please take a look these example - programs. -

Tracing Overheads and Scheduling Decisions

LITMUS^RT provides numerous tracing facilities that are discussed in-depth in the tutorial Tracing with LITMUS^RT. -

- Please contact bbb[AT]cs.unc.edu if you have any - questions. -

- - -

- -

Credits

- -

- Linux is a registered trademark of Linus Torvalds.
The - LITMUS^RT logo was designed by Jasper McChesney of Break for Sense Design.
- Web design by Björn Brandenburg. -

- - -

- - - - - + + + + + + + + LITMUS RT: Linux Testbed for Multiprocessor Scheduling in Real-Time Systems + + +

+ Dr. James H. Anderson & + Students, + The University of North Carolina at Chapel Hill +

+ +

+ about - + support - + collaborators - + publications - + download - + installation - + documentation +

+ +

About

+ The LITMUS^RT project is a soft real-time extension of the Linux + kernel with focus on multiprocessor real-time scheduling and + synchronization. The Linux kernel is modified + to support the sporadic task + model and modular scheduler plugins. Both partitioned and global scheduling + is supported. +

Goals

+ The primary purpose of the LITMUS^RT project is to provide a useful experimental platform for applied real-time systems research. In that regard, LITMUS^RT provides abstractions and interfaces within the kernel that simplify the prototyping of multiprocessor real-time scheduling and synchronization algorithms (compared to modifying a "vanilla" Linux kernel). As a secondary goal, LITMUS^RT serves as a proof of concept, showing that algorithms such as PFAIR can be implemented on current hardware. Finally, we hope that parts of LITMUS^RT and the "lessons learned" may find value as blueprints/sources of inspiration for other (both commercial and open source) implementation efforts. +

Non-Goals

+ LITMUS^RT is not a production-quality system, and we have currently no plans to turn it into one. LITMUS^RT is not "stable," i.e., interfaces and implementations may change without warning between releases. POSIX-compliance is not a goal; the LITMUS^RT-API offers alternate system call interfaces. While we aim to follow Linux-coding guidelines, LITMUS^RT is not targeted at being merged into mainline Linux. Rather, we hope that some of the ideas protoyped in LITMUS^RT may eventually find adoption in Linux. +

Current Version

+ The current version of LITMUS^RT is 2010.1 and is based on Linux 2.6.32. + It was released on 05/12/2010 and includes plugins for the following + scheduling policies: +

Partitioned EDF with synchronization support (PSN-EDF)
Global EDF with synchronization support (GSN-EDF)
Clustered EDF (C-EDF)
PFAIR (both staggered and aligned quanta are supported)

+ Please refer to the download and installation sections for details. +

Earlier versions (2008.1 &mdash 2008.3),based on Linux 2.6.24 and (2007.1 — 2007.3), based on Linux 2.6.20 + ,support additional scheduling policies, are discussed on separate pages dedicated to the LITMUS^RT 2008 and LITMUS^RT 2007 series respectively. +

+ The first version of LITMUS^RT, which was implemented in Spring 2006, + is based on Linux 2.6.9. +

Development Plans

+ There are plans to port LITMUS^RT to PowerPC and ARM platforms. Please contact us for details. +

Support

+ The LITMUS^RT development effort is being supported by grants from, SUN Corp., + Intel Corp., IBM Corp., The National Science Foundation (grant CCR 0615197), and The U.S. + Army Research Office (grant W911NF-06-1-0425). +

+ +

Collaborators

The LITMUS^RT project is led by Dr. James H. Anderson. +

+ The implementation effort is carried out by students of the + Real-Time Systems + Group at the University of North Carolina + at Chapel Hill: +

+ Björn B. Brandenburg (current maintainer) +
Andrea Bastoni (Visiting researcher from University of Rome "Tor Vergata") +

+ (Additional collaborators for LITMUS^RT 2008 series and LITMUS^RT 2007 series contributed to earlier versions of LITMUS^RT.) +

+ + +

Publications

+ B. Brandenburg and J. Anderson, + “On the Implementation of Global Real-Time + Schedulers”, Proceedings of the 30th IEEE Real-Time Systems Symposium, pp. 214-224, December 2009. + Postscript. + PDF. + Longer version with all graphs: + Postscript. + PDF. +
+
For reference, all evaluated plugins are provided as part of the following patch (against version 2008.3). +
+
- + litmus-rt-RTSS09.patch +
+ +
+
+ B. Brandenburg and J. Anderson + “Reader-Writer Synchronization for Shared-Memory Multiprocessor Real-Time Systems”, + Proceedings of the 21st Euromicro Conference on Real-Time Systems, pp. 184-193, July 2009. + Postscript. PDF. + Long version with blocking terms: + Postscript. PDF. +
+
+
+ J. Calandrino and J. Anderson + “On the Design and Implementation of a Cache-Aware Multicore Real-Time Scheduler”, + Proceedings of the 21st Euromicro Conference on Real-Time Systems, pp. 194-204, July 2009. + Postscript. PDF. +
+
+
+ M. Mollison, B. Brandenburg, and J. Anderson + “Towards Unit Testing Real-Time Schedulers in LITMUS^RT”, + Proceedings of the Fifth International Workshop on Operating Systems Platforms for Embedded Real-Time Applications, pp. 33-39, July 2009. + Postscript. PDF. +
+
+
+ B. Brandenburg and J. Anderson, + “A Comparison of the M-PCP, D-PCP, and FMLP on LITMUS^RT”, + Proceedings of the 12th International Conference on Principles of Distributed Systems, pp. 105-124, December 2008. + Postscript. PDF. +
+
+
+ B. Brandenburg, J. Calandrino, and J. Anderson, + “On the Scalability of Real-Time Scheduling Algorithms on Multicore Platforms: A Case Study”, + Proceedings of the 29th IEEE Real-Time Systems Symposium, + pp. 157-169, December 2008. + Postscript. PDF. +
+
+
+ B. Brandenburg and J. Anderson, + “An Implementation of the PCP, SRP, D-PCP, M-PCP, + and FMLP Real-Time Synchronization Protocols in LITMUS^RT”, + Proceedings of the 14th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, pp. 185-194, August 2008. + Postscript. PDF. +
+
Note: The work described in this paper took part in a branch that is currently not part of + the main distribution. For reference, we provide the branch as a separate download: +
+
- + litmus-rt-RTCSA08.patch +
- + liblitmus-RTCSA08.tgz +
- SHA256 check sums +
+
Please don't use this version for active development. If you are interested in this work, it would be best + to first port the desired features to a current version of LTIMUS^RT and merge them into the main distribution. +
+ +
+
+ A. Block, B. Brandenburg, J. Anderson, + and S. Quint, “An Adaptive Framework for Multiprocessor Real-Time Systems”, + Proceedings of the 20th Euromicro Conference on Real-Time Systems, pp. 23-33, July 2008. + Postscript. PDF. +
+
+
+ B. Brandenburg, J. Calandrino, A. Block, + H. Leontyev, and J. Anderson, “Real-Time Synchronization + on Multiprocessors: To Block or Not to Block, to Suspend or + Spin?”, Proceedings of the 14th IEEE Real-Time and Embedded +Technology and Applications Symposium, pp. 342-353, April 2008. + Postscript. PDF. +
+
+ Extended version, including all graphs: + Postscript, + PDF. +
+
+
+ B. Brandenburg, A. Block, J. Calandrino, U. Devi, H. Leontyev, and J. Anderson, + "LITMUS^RT: A Status Report", Proceedings of the 9th + Real-Time Linux Workshop, pp. 107-123, November 2007. + Postscript. + PDF. +
+
+
+ B. Brandenburg and J. Anderson, "Integrating Hard/Soft Real-Time Tasks + and Best-Effort Jobs on Multiprocessors", Proceedings of the 19th Euromicro + Conference on Real-Time Systems, pp. 61-70, July 2007. + Postscript, + PDF. +
+
+
+ J. Calandrino, H. Leontyev, A. Block, U. Devi, and J. Anderson, + "LITMUS^RT: A Testbed for Empirically Comparing Real-Time + Multiprocessor Schedulers ", Proceedings of the 27th IEEE Real-Time Systems + Symposium, pp. 111-123, December 2006. + Postscript, + PDF. +
+

+ +

Download

+ The source code of LITMUS^RT is made available as open source + under the terms of the GNU + General Public License (GPL). +

+ The current release of LITMUS^RT is 2010.1. + It consists of our Linux kernel modifications in the form of + a patch against Linux 2.6.32 and + + liblitmus, the user-space API for real-time + tasks, as well as ft_tools, a collection of tools + used for tracing with Feather-Trace (which is part of the LITMUS^RT patch). +

+ +

LITMUS^RT 2010.1

+ Based on Linux 2.6.32. Released in May 2010. + +

Files:

Major changes (since LITMUS^RT 2008.3):

TO BE UPDATED +

+ Changed codebase from Linux 2.6.24 to Linux 2.6.32 +
Several bugfixes.

+ +

+ Please note that the current implementation is a prototype with + certain limitations. Most notably, it is not secure in a multiuser context, + i.e., real-time system calls do not require superuser + privileges. +

+ +

+ + Older releases: LITMUS^RT 2008 series, LITMUS^RT 2007 series. +

+ +

+ + + +

Installation

+ The current release of LITMUS^RT consists of an + extension of the Linux kernel that adds support for the sporadic task + model, a scheduler plugin infrastructure, and some scheduler plugins, as + well as a user-space library that provides the LITMUS^RT + real-time API. Note that the current implementation only works on the + Intel x86-32 and sparc64 architectures. +

Patching the Kernel

+ The extension to the Linux kernel is released as a patch against Linux + 2.6.32. To install the LITMUS^RT kernel, first download the Linux + kernel 2.6.32 and untar it in a directory of your choice (hereafter + referred to as $DIR). Second, apply the + LITMUS^RT patch (see Section Download) + and configure, compile, and install the kernel as usual. The patch is -p1 applicable. + To summarize, the LITMUS^RT kernel can be obtained, patched, and + compiled with the following commands: +

 
+cd $DIR
+# get Linux 2.6.32
+wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.32.tar.bz2
+tar xjf linux-2.6.32.tar.bz2
+wget http://www.cs.unc.edu/~anderson/litmus-rt/download/2010.1/litmus-rt-2010.1.patch
+mv linux-2.6.32 litmus2010
+# apply the LITMUS RT patch
+cd litmus2010
+patch -p1 < ../litmus-rt-2010.1.patch
+# create a working kernel configuration
+#  - select HZ=1000
+#  - enable in-kernel preemptions
+#  - disable NO_HZ
+#  - don't use power management options like frequency scaling
+#  - disable support for group scheduling
+make menuconfig
+# compile the kernel
+make bzImage
+make modules
+# proceed to install kernel, build initrd, etc.
+...
+

+ When configuring the kernel, note that there is a menu (at the very end of the list) + with LITMUS^RT-specific configuration options. For reference, we provide sample 32-bit and 64-bit configurations that are known to work under QEMU. +

+ +

Libraries

+ The user-space library for real-time tasks, liblitmus, + depends on the LITMUS^RT kernel kernel and provides its own build system (based on scons). + In order to compile liblitmus, you need to adjust the + variable LITMUS_KERNEL in the SConstruct file to point to your + copy of the kernel. Users should not update the SConstruct file manually anymore. Instead, a .config file can be created with appropriate variables. The required variables can be listed using scons -h command. This command lists the variables required for building the liblitmus2010 library.
+ Sample output of scons -h is as shown below. +

 
+scons -h
+scons: Reading SConscript files ...
+scons: done reading SConscript files.
+
+=============================================
+liblitmus --- The LITMUS^RT Userspace Library
+
+There are a number of user-configurable build
+variables. These can either be set on the
+command line (e.g., scons ARCH=x86) or read
+from a local configuration file (.config).
+
+Run 'scons --dump-config' to see the final
+build configuration.
+
+Build Variables
+---------------
+
+LITMUS_KERNEL: Where to find the LITMUS^RT kernel. ( /path/to/LITMUS_KERNEL )
+    default: ../litmus2010
+    actual: ../litmus2010
+
+PYTHON_HEADERS: Where to find Python headers. ( /path/to/PYTHON_HEADERS )
+    default: /usr/include/python2.5
+    actual: /usr/include/python2.5
+
+ARCH: Target architecture. (x86_64|sparc64|x86|i686)
+    default: x86_64
+    actual: x86_64
+
+WSS: Working set size for pm analysis
+    default: 3072
+    actual: 3072
+
+Use scons -H for help about command-line options.
+

+ +

+ To summarize, the liblitmus can be obtained and + compiled with the following commands: +

+ +

 
+cd $DIR
+wget http://www.cs.unc.edu/~anderson/litmus-rt/download/2010.1/liblitmus-2010.1.tgz
+tar xzf liblitmus-2010.1.tgz
+cd liblitmus 
+
+# set LITMUS_KERNEL in .config to point to the kernel source and compile
+scons
+

+ Please refer to the documentation on how to use the LITMUS^RT + real-time API as provided by liblitmus. +

+ +

+ + +

Documentation

+ +

+ Unfortunately, most of the documentation has yet to be written. To get an overview of + the architecture of the kernel extension, we recommend reading the paper + “LITMUS^RT: + A Status Report”. +

Real-Time Scheduling Policies

+ The kernel contains the following real-time scheduling policy implementations: +

+ PFAIR, an implementation of the PD² algorithm, +
+ PSN-EDF, a partitioned EDF (P-EDF) implementation with support for the real-time synchronization protocol + FMLP, +
+ GSN-EDF, a global EDF (G-EDF) implementation with support for the real-time synchronization protocol + FMLP, +
+ C-EDF (Clustered EDF), a hybrid of G-EDF and P-EDF, and +
+ Linux, a placeholder policy that disables all real-time functionality added by the LITMUS^RT patch. +

+ Only one policy can be active at any time. Initially (i.e., during and after boot), the "Linux" policy is active. + You can use the tool showsched (part of liblitmus) to display + the name of the currently active policy. +

Changing the Active Policy

+ You can use the tool setsched (part of liblitmus) + to select a new plugin at run time. +

+ Only root can change the active policy, and only when there are no real-time tasks present. +

+ If you do not have the dialog utility installed, then you can still use setsched by passing the desired scheduling policy as a commandline parameter, e.g. type setsched PFAIR to activate the PFAIR plugin. +

Writing Real-Time Tasks

+ The user space library that provides the LITMUS^RT API, + liblitmus, contains two example real-time tasks + (base_task.c and + base_mt_task.c) + that both illustrate how to use the API and provide a skeleton for real-time + task development. To get started with development, please take a look these example + programs. +

Tracing Overheads and Scheduling Decisions

LITMUS^RT provides numerous tracing facilities that are discussed in-depth in the tutorial Tracing with LITMUS^RT. +

+ Please contact bbb[AT]cs.unc.edu if you have any + questions. +

+ + +

+ +

Credits

+ +

+ Linux is a registered trademark of Linus Torvalds.
The + LITMUS^RT logo was designed by Jasper McChesney of Break for Sense Design.
+ Web design by Björn Brandenburg. +

+ + +

+ + + + + -- cgit v1.2.2

About

Goals

Non-Goals

Current Version

Development Plans

Support

Collaborators

Publications

Download

LITMUSRT 2010.1

Files:

Major changes (since LITMUSRT 2008.3):

Installation

Patching the Kernel

Libraries

Documentation

Real-Time Scheduling Policies

Changing the Active Policy

Writing Real-Time Tasks

Tracing Overheads and Scheduling Decisions

Credits

About

Goals

Non-Goals

Current Version

Development Plans

Support

Collaborators

Publications

Download

LITMUSRT 2010.1

Files:

Major changes (since LITMUSRT 2008.3):

Installation

Patching the Kernel

Libraries

Documentation

Real-Time Scheduling Policies

Changing the Active Policy

Writing Real-Time Tasks

Tracing Overheads and Scheduling Decisions

Credits

LITMUS^RT 2010.1

Major changes (since LITMUS^RT 2008.3):

LITMUS^RT 2010.1

Major changes (since LITMUS^RT 2008.3):