Hybrid Online/ooine Scheduling for Hard Real-time Systems
نویسندگان
چکیده
OOine (cyclic executive) and online preemptive, priority-based scheduling are not exclusive options but rather complementary techniques that can be combined to improve analytically veriiable schedulability. Selective ooine scheduling of periodic tasks improves online schedula-bility based on rate-monotonic priority assignment. Relative to pure ooine scheduling, a hybrid approach has the advantage of not requiring all tasks to be scheduled together. Aperiodic and sporadic tasks can be left to the online scheduling component where sporadic servers and other methods are applicable. Relative to pure online pre-emptive scheduling, the hybrid approach improves schedulability by avoiding worst-case task phasings, eliminating some blocking time and semaphore management overheads, and reducing context switch overheads. Manual division of source code into scheduling units is not necessary. We have constructed an ooine scheduler that optimally allocates idle time to improve rate-monotonic schedulability.
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