Unformatted text preview: 1 1 Homework 5 Solution
Problem 1: Design a scheduling algorithm which ensures that over a relatively long interval CPU time is divided evenly between all tasks. For example, consider a system running this algorithm with two tasks, one I O bound, the other compute bound. The run time of the tasks is long compared to the interval. The I Obound task and the CPU-intensive task would each get 50 of the CPU time unless the time to complete I O requests is very large. Key Points: When a task goes into the Wait state it normally forfeits the remainder of its quantum. The scheduling algorithm should allow the task to catch up." Solution: Use two priority levels:
1: Normal tasks. 2: Tasks which have fallen behind. Within each priority level, use FCFS scheduling. OS is task-preemptive. The following actions are taken when a priority-1 task must wait: The remaining time in its quantum is stored, use symbol trq for this time. The time at which it went into the wait state is stored, tw . Its priority is set to 2 and it is placed in the wait lis...
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- Fall '99
- Trigraph, Central processing unit, Interrupt, CPU time, Priority level, Lecture Transparency