chapter09 - Aim of Scheduling Uniprocessor Scheduling...

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1 Uniprocessor Scheduling Chapter 9 Aim of Scheduling Assign processes to be executed by the processor or processors over time, in a way that meets system objectives: Response time Throughput Processor efficiency The key to multiprogramming is scheduling . Types of Scheduling Level of Scheduling (Referencing figure 3.9b)
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2 Long-Term Scheduling Determines when to create a new process and which programs are admitted next to the system for processing. Controls the degree of multiprogramming the more processes that are created, the smaller the percentage of time that each process can be executed may limit to provide satisfactory service to the current set of processes Medium-Term Scheduling Part of the swapping function The swapping-in decision is based on the need to manage the degree of multiprogramming considers the memory requirements of the swapped-out processes Short-Term Scheduling Known as the dispatcher Executes most frequently Makes the fine-grained decision of which process to execute next Invoked when an event occurs that may lead to the blocking of the current process or that may provide an opportunity to preempt a currently running process in favor of another Clock interrupts I/O interrupts Operating system calls Signals (e.g. semaphores). Short Term Scheduling Criteria Main objective is to allocate processor time to optimize certain aspects of system behavior A set of criteria is needed to evaluate the scheduling policy. Short-Term Scheduling Criteria: Performance Short-Tem Scheduling Criteria User-oriented Response Time Elapsed time between the submission of a request until there is output. System-oriented Effective and efficient utilization of the processor Throughput
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3 Short-Term Scheduling Criteria Performance-related Quantitative Measurable such as response time and throughput Not performance related Qualitative Predictability Priorities Scheduler will always choose a process
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This note was uploaded on 11/26/2011 for the course CSE 410 taught by Professor Bonakdarpour during the Spring '08 term at Michigan State University.

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chapter09 - Aim of Scheduling Uniprocessor Scheduling...

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