Different Systems, Different Focuses •Batch Systems (e.g., billing, accounts receivable, accounts payable, etc.) –Max throughput, max CPU utilization •Interactive Systems (e.g., our PC) –Min. response time •Real‐time system (e.g., airplane) –Priority, meeting deadlines •Example: on airplane, Flight Control has strictly higher priority than Environmental Control
Program Behaviors Considered in Scheduling •Is it I/O bound? Example? •Is it CPU bound? Example? •Batch or interactive environment •Priority •Frequency of page fault •Frequency of I/O
Preemptive vs. Non‐preemptive •Non‐preemptive scheduling –The running process keeps the CPU until it voluntarily gives up the CPU •Process exits •Switch to blocked state •1 and 4 only (no 3 unless calls yield) •Preemptive scheduling –The running process can be interrupted and must release the CPU
Scheduling Algorithms
•First Come First Serve (FCFS) •Short Job First (SJF) •Priority Scheduling •Round Robin •Multi‐Queue & Multi‐Level Feedback •Earliest Deadline First Scheduling
Batch Systems
Interactive Systems
Different Systems, Different Focuses •Batch Systems (e.g., billing, accounts receivable, accounts payable, etc.) –Max throughput, max CPU utilization •Interactive Systems (e.g., our PC) –Min. response time •Real‐time system (e.g., airplane) –Priority, meeting deadlines •Example: on airplane, Flight Control has strictly higher priority than Environmental Control Program Behaviors Considered in Scheduling •Is it I/O bound? Example? •Is it CPU bound? Example? •Batch or interactive environment •Priority •Frequency of page fault •Frequency of I/OPreemptive vs. Non‐preemptive •Non‐preemptive scheduling –The running process keeps the CPU until it voluntarily gives up the CPU •Process exits •Switch to blocked state •1 and 4 only (no 3 unless calls yield) •Preemptive scheduling –The running process can be interrupted and must release the CPUScheduling Algorithms•First Come First Serve (FCFS) •Short Job First (SJF) •Priority Scheduling •Round Robin •Multi‐Queue & Multi‐Level Feedback •Earliest Deadline First SchedulingBatch SystemsInteractive Systems
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