A New Application-Defined Scheduling Implementation in RTLinux
A. Díaz,  Ismael Ripoll,  A. Crespo,  Patricia Balbastre,  
Sixth Real-Time Linux Workshop
Scheduling theory has shown an impressive evolution due to the intensive research done in this area. As a result, a lot of scheduling algorithms has been proposed to support a large amount of applications. RTLinux uses a xed-priority scheduler and although xed-priority scheduling is suited for a large number of real-time applications, it has some drawbacks. Nevertheless, adding new scheduling policies is a complex and time-consuming task since the kernel's internal structure must be modi ed. In recent years, an Application Program Interface (API) to create Application-De ned Schedulers in a way compatible with POSIX has been proposed. This model allows the implementation of di erent scheduling policies in a portable way, without modifying the internal structure of the real-time operating system. In this document, the implementation of a new Application-De ned Scheduling model in RTLinux is presented. The Application-De ned schedulers are not implemented as special threads but as a set of primitive operations that are executed inside the kernel, avoiding unnecessary and costly context switches. Also in this paper, a new library of Application-De ned Schedulers and its API is presented. This library o ers a wide range of scheduling policies. Using this library, the implementation of Real-Time systems can be done in an easy, e cient and consistent way. The use of the library makes possible the creation of systems with multiple schedulers working concurrently, every one at a di erent priority level.
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author = {Díaz A., Ripoll Ismael, Crespo A., Balbastre Patricia, },
title = {A New Application-Defined Scheduling Implementation in RTLinux},
booktitle = {Sixth Real-Time Linux Workshop},
pages = {175-181},
year = {2004},
isbn = {114},
publisher = {Peter Wurmsdobler}