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第ä¹�ç« è°�度 - CHAPTER 9 CHAPTER 9...

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Unformatted text preview: CHAPTER 9 CHAPTER 9 UNIPROCESSOR SCHEDULING UNIPROCESSOR SCHEDULING ( ( t&l¶“u¡ 8A¢‚“u¡ Aim of Scheduling Aim of Scheduling • Processor efficiency (m : (m : CPU (m : • Fairness( ) 6 Types of Scheduling Types of Scheduling N : m : • i OS lA “ : & & i q • && & Long-term scheduling i m Medium-term scheduling im Short-term scheduling i m Long-term scheduling Long-term scheduling && H & i q ¡A : 6 H& H& Short-term scheduling • 3 “ : 8 : c l “ : i Medium- term scheduling H • @ aV & V 6 j ¡ “ : 6 Long-Term Scheduling Long-Term Scheduling • Determines which programs are admitted to the system for processing- &&& FCFS &&& i q H&&& • How many programs are admitted to the system ? - Controls the degree of multiprogramming • When does the scheduler be invoked?- Each time a job terminates- Processor is idle exceeds a certain threshold Medium-term scheduling Medium-term scheduling H z : & i q • h& h& h& h& • & & i q • && & V 6 m H z Short-term scheduling Short-term scheduling • & V i “ : 6 • Known as the dispatcher:: Which h&& ¡˚L·“ • Executes most frequently • Invoked when an event occurs – Clock interrupts – I/O interrupts – Operating system calls – Signals( i ) 9.2 9.2 SCHEDULING ALGORITHMS SCHEDULING ALGORITHMS ( ( N i ) ) • Scheduling Criteria( Scheduling Criteria( N i ) ) • The Use of Priorities( The Use of Priorities( N : m : ) ) • Scheduling Policies( Scheduling Policies( N i ) ) Scheduling Criteria Scheduling Criteria ( ( N i ) ) User-oriented User-oriented • Response Time ( h )- Elapsed time between the submission of a request until there is output....
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第ä¹�ç« è°�度 - CHAPTER 9 CHAPTER 9...

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