ch05 - Chapter 5: CPU Scheduling Chapter 5: CPU Scheduling...

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Unformatted text preview: Chapter 5: CPU Scheduling Chapter 5: CPU Scheduling 5.2 Silberschatz, Galvin and Gagne 2005 Operating System Concepts Chapter 5: CPU Scheduling Chapter 5: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Multiple-Processor Scheduling Real-Time Scheduling Thread Scheduling Operating Systems Examples Java Thread Scheduling Algorithm Evaluation 5.3 Silberschatz, Galvin and Gagne 2005 Operating System Concepts Basic Concepts Basic Concepts Maximize CPU utilization by multiprogramming CPUI/O Burst Cycle Process execution consists of a cycle of CPU execution and I/O wait CPU burst distribution 5.4 Silberschatz, Galvin and Gagne 2005 Operating System Concepts Alternating Sequence of CPU And I/O Bursts Alternating Sequence of CPU And I/O Bursts 5.5 Silberschatz, Galvin and Gagne 2005 Operating System Concepts Histogram of CPU-burst Times Histogram of CPU-burst Times 1. A large number of short CPU bursts 2. A small number of long CPU bursts 5.6 Silberschatz, Galvin and Gagne 2005 Operating System Concepts CPU Scheduler 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 5.7 Silberschatz, Galvin and Gagne 2005 Operating System Concepts Dispatcher 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 5.8 Silberschatz, Galvin and Gagne 2005 Operating System Concepts Scheduling Criteria 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 (from the time of submission to the time of completion) Waiting time amount of time a process has been waiting in the ready queue CPU scheduling does not affect the amount of time during which a process executes or does I/O 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) 5.9 Silberschatz, Galvin and Gagne 2005 Operating System Concepts Optimization Criteria Optimization Criteria Max CPU utilization Max throughput Min turnaround time Min waiting time Min response time Question: Is average good?...
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This note was uploaded on 03/01/2011 for the course CSSE 250 taught by Professor Dr.yingwuzhu during the Spring '11 term at UH Clear Lake.

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ch05 - Chapter 5: CPU Scheduling Chapter 5: CPU Scheduling...

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