Operating System_CPU Scheduling

Operating System_CPU Scheduling - Silberschatz Galvin and...

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Unformatted text preview: Silberschatz, Galvin and Gagne 2002 6.1 Operating System Concepts CPU Scheduling ■ Basic Concepts ■ Scheduling Criteria ■ Scheduling Algorithms ■ Multiple-Processor Scheduling ■ Real-Time Scheduling Silberschatz, Galvin and Gagne 2002 6.2 Operating System Concepts Basic Concepts ■ Maximum CPU utilization obtained with multiprogramming ■ CPU–I/O Burst Cycle – Process execution consists of a cycle of CPU execution and I/O wait. ■ CPU burst distribution Silberschatz, Galvin and Gagne 2002 6.3 Operating System Concepts Alternating Sequence of CPU And I/O Bursts Silberschatz, Galvin and Gagne 2002 6.4 Operating System Concepts CPU Scheduler ■ Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. ■ CPU scheduling decisions may take place when a process: 1. Switches from running to waiting state. 2. Switches from running to ready state. 3. Switches from waiting to ready. 4. Terminates. ■ Scheduling under 1 and 4 is nonpreemptive . ■ All other scheduling is preemptive. Silberschatz, Galvin and Gagne 2002 6.5 Operating System Concepts Dispatcher ■ Dispatcher module gives control of the CPU to the process selected by the short-term scheduler; this involves: ✦ switching context ✦ switching to user mode ✦ jumping to the proper location in the user program to restart that program ■ Dispatch latency – time it takes for the dispatcher to stop one process and start another running. Silberschatz, Galvin and Gagne 2002 6.6 Operating System Concepts Scheduling Criteria ■ CPU utilization – keep the CPU as busy as possible ■ Throughput – # of processes that complete their execution per time unit ■ Turnaround time – amount of time to execute a particular process ■ Waiting time – amount of time a process has been waiting in the ready queue ■ Response time – amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment) Silberschatz, Galvin and Gagne 2002 6.7 Operating System Concepts Optimization Criteria ■ Max CPU utilization ■ Max throughput ■ Min turnaround time ■ Min waiting time ■ Min response time Silberschatz, Galvin and Gagne 2002 6.8 Operating System Concepts First-Come, First-Served (FCFS) Scheduling...
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This note was uploaded on 04/05/2010 for the course CS 551 taught by Professor V during the Spring '08 term at Jaypee University IT.

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Operating System_CPU Scheduling - Silberschatz Galvin and...

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