LITMUS^RT User-Space Library: liblitmus
Copyright (c) 2007-2016 The LITMUS^RT Project & Contributors http://www.litmus-rt.org
Released as open source under the terms of the GNU General Public License (GPL2).
This library and the included tools provide the user-space interface to
LITMUS^RT. Real-time tasks should link against this library. The header
litmus.h contains all necessary system calls and definitions to
interact with the kernel services provided for real-time tasks.
For a gentle introduction to LITMUS^RT and its userspace tools, we recommend to check out the materials that were prepared for the LITMUS^RT tutorial presented at TuToR'16 @ CPSWeek'16.
In particular, check out the online manual prepared for TuToR'16:
Some additional information is available on the LITMUS^RT wiki at:
When writing real-time applications that need to make use of
LITMUS^RT-specific interfaces and facilities, the application binary
needs to be linked against
liblitmus (this library). Instructions for
how to do so are provided on the LITMUS^RT wiki.
- HOWTO: linking against liblitmus.
As of version 2016.1, LITMUS^RT supports reservation-based scheduling. How to set up and use reservations is described in a separate document.
- HOWTO: working with reservations
As part of the reservation framework, LITMUS^RT also supports proper table-driven scheduling (aka time partitioning or time-triggered scheduling). How to set up and use a static scheduling table described in a separate guide.
- HOWTO: table-driven scheduling
For any questions, bug reports, suggestions, etc. pertaining to
liblitmus, please contact the LITMUS^RT mailing
Tools and Programs in
Selects the active scheduler. Must be run as root. Run without argument to be presented with a list of available plugins (requires 'dialog' to be installed).
Print the name of the currently active scheduler.
rt_launch [-w] [-p <PARTITION>] <WCET> <PERIOD> <PROGRAM> <ARGS>...
Launch the program
<PROGRAM> as a real-time task provisioned with the
given worst-case execution time and priod. Any additional parameters are
passed on to the real-time task. The -w option makes the task wait for a
sytem release. Run
rt_launch -h for further options.
Tip: for debugging purposes, a couple of
rt_launch $EXEC_TIME $PERIOD find /
real-time processes, for reasonable values of
$PERIOD, generates a workload that stresses the wakeup/suspend path of
the scheduler pretty well. Similarly, running
rt_launch $EXEC_TIME $PERIOD sha256sum `find /home | sort -R
produces a CPU-intensive workload that also includes significant IO.
rtspin [-w] [-p <PARTITION>] WCET PERIOD DURATION
A simple spin loop for emulating purely CPU-bound workloads. Not very
realistic, but a good tool for debugging. The
-w option makes the task
wait for a sytem release. Run
rtspin -h for further options.
PERIOD must be given in milliseconds, the
DURATION must be given in seconds.
release_ts [-f <NUM_TASKS>]
Release the task system. This allows for synchronous task system
releases (i.e., ensure that all tasks share a common "time zero"). The
-f option makes
release_ts wait until the number of tasks waiting
for the task system release equals
release_ts -h for further options.
measure_syscall: A simple tool that measures the cost of invoking a LITMUS^RT system call.
cycles: Display measured cycles per time interval, as determined by the cycle counter. Useful for converting benchmarking results.
base_task: Example real-time task. To be used as a template for the development of single-threaded real-time tasks.
base_mt_task: Example multi-threaded real-time task. To be used as a template for the development of multithreaded real-time tasks.
uncache: Demo application showing how to allocate and use uncached pages (i.e., pages that bypass the cache).
runtests: The LITMUS^RT test suite. By default, it runs the tests for the currently active plugin. Use this frequently when hacking on the core plugins. Add support for new plugins as needed. The tests can be found in tests/ directory.