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Process Scheduling II ( 5.3)

Process Scheduling II ( 5.3). CPE 261403 - Operating Systems http://www.e-cpe.org/moodle. Scheduling Criteria (5.2). CPU Utilization Throughput Turnaround time Waiting time Response time. Scheduling Algorithms (5.3). FCFS SJF (non-preemptive / preemptive) Priority Scheduling

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Process Scheduling II ( 5.3)

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  1. Process Scheduling II(5.3) CPE 261403 - Operating Systems http://www.e-cpe.org/moodle

  2. Scheduling Criteria (5.2) • CPU Utilization • Throughput • Turnaround time • Waiting time • Response time

  3. Scheduling Algorithms (5.3) • FCFS • SJF (non-preemptive / preemptive) • Priority Scheduling • Round-Robin Scheduling • Multilevel Queue Scheduling • Multilevel Feedback-Queue Scheduling

  4. Priority Scheduling • Defining Priorities • Internally Defined Priorities (i.e. Memory requirements, Time to execute) • External priorities (usually defined by the user) (i.e. importance of the process)

  5. Starvation

  6. IBM 7094 at MIT When closing down in 1973, found a process submitted in 1967 (Myth)

  7. Round Robin Scheduling • Preemptive by Nature • Defines a Time Quantum • Time Quantum >> Context Switch Time

  8. Multilevel Queue Scheduling • Scheduling within & among queues • Use simple priority or CPU time slice (quota)

  9. Multilevel Feedback Queue • Example: Q1=RR, Q2=RR, Q3=FCFS

  10. Multilevel Feedback Queue • Parameters: • Number of queues • Scheduling algorithms for each queue • When to upgrade a process (i.e. when it requests I/O) • When to downgrade a process (i.e. when it exceeds the time quantum) • Which queue should a new process enter

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