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The IRMOS realtime scheduler

Aug 20, 2010, 00:02 (0 Talkback[s])
(Other stories by T. Cucinotta, F. Checconi)


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"In the context of the IRMOS European Project (Interactive Real-Time Applications on Service-Oriented Infrastructures), a new realtime scheduler for Linux has been developed by the Real-Time Systems Laboratory of Scuola Superiore Sant'Anna in Pisa. The purpose of this article is to provide a general overview of this new scheduler, describe its features and how it can be practically used, provide a few details about the implemented algorithms, and gathering feedback by the community about possible improvements.

"The IRMOS realtime scheduler (a.k.a., EDF throttling or realtime throttling), allows the administrator to reserve a "slice" of the processing capability of a system for a group of Linux tasks. It is based on a direct modification of the POSIX realtime scheduling class within the Linux kernel, and in particular, to the throttling mechanism already built into the kernel for realtime tasks. Basically, the realtime throttling mechanism is changed from a mechanism that exclusively limits the computation power granted to groups of realtime tasks, to one that provides them with both a limit and precise scheduling guarantees (in terms of a guaranteed runtime every period, on each of the available CPUs). Also, it has been designed from scratch with SMP support in mind, and it implements a hierarchical scheduling policy based on both deadlines and priorities. Specifically, POSIX fixed priority (FP) realtime scheduling is nested inside EDF (Earliest Deadline First) scheduling."

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