Real-Time Scheduling and Synchronization in Real-Time Mach

A micro kernel-based operating system architecture is becoming common for advanced distributed computing systems. Advantages of using such micro kernel for real-time applications is that the preemptability of the kernel is better, the size of the kernel becomes much smaller, and addition of new service is easier. However, such a micro kernel alone cannot provide a predictable, distributed real-time computing environment due to many unpredictable delay caused by unbounded priority inversions. In this paper, we report new extensions for supporting real-time thread, synchronization, and scheduler in Real-Time Mach. This extension is based on a real-time thread model and integrated time-drive scheduler model. We describe the interface, implementation results, and measured performance of the system functions. Our benchmark results demonstrated that policy/mechanism separation of real-time scheduling and synchronization facility is important. A proper choice of scheduling and locking policy can avoid unbounded priority inversions and improve the processor schedulability and worst case response time signi cantly. 1 This research was supported in part by the U.S. Naval Ocean Systems Center under contract number N66001-87-C-0155, by the O ce of Naval Research under contract number N00014-84-K0734, by the Defense Advanced Research Projects Agency, ARPA Order No. 7330 under contract number MDA72-90-C-0035, by the Federal Systems Division of IBM Corporation under University Agreement YA-278067, and by the SONY Corporation. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing o cial policies, either expressed or implied, of NOSC, ONR, DARPA, IBM, SONY, or the U.S. Government.