mmedia-sched

mmedia-sched - Today CSCI 5105 Foundations of Modern...

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1 CSCI 5105 Foundations of Modern Operating Systems Instructor: Abhishek Chandra Today Multimedia Scheduling Real-Time Scheduling Proportional-share Scheduling 2 Multimedia Scheduling Traditional schedulers: FIFO, Round-robin, SJF Try to satisfy global system properties: Fairness, throughput, latency Priority: Strict ordering Limitation: Do not provide application-specific guarantees Goal: Meet application CPU requirements 3 4 Real-Time Scheduling Used more generally in Real-time OS Scheduling of multiple processes with: Different amounts of work C i Different deadlines to finish the work D i Different frequencies of work generation F i (Period P i ) Multimedia Systems: Periodic processes E.g.: Video streams with different bit rates, playback rates, etc.
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2 5 Example Periodic Processes 0 10 20 30 40 50 A B C Processes A, B, C: Periods 30, 40, 50 Work/period: 10, 15, 5 60 70 80 90 100 6 Real-Time Scheduling Question: When should each process be scheduled so that all tasks finish their work before their deadlines? Feasibility condition: 1 1 m i i i P C 7 Real-Time Scheduling Algorithms Static: Each process is assigned a static priority Higher priority process always preempts lower- priority process Dynamic: Priorities are chosen dynamically
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mmedia-sched - Today CSCI 5105 Foundations of Modern...

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