chapter6 - CS 390 Chapter 6 Homework Solutions 6.1 A...

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CS 390 Chapter 6 Homework Solutions 6.1 A CPU-scheduling algorithm determines ... Think of an ordered list with n elements in which we are to place n processes. The first element could be filled by any of the n processes. The second element could be filled by any of the remaining n - 1 processes. The third element by any of the remaining n - 2 processes, and so on. If we think of the each possible combination of processes in the list as a schedule, there are n ! schedules possible. 6.2 Explain the difference between preemptive ... In non-preemptive scheduling, the scheduler only runs when a process voluntarily relinquishes the CPU (either by performing a system call or terminating). In preemptive scheduling, scheduling occurs at both of these times, as well as during interrupt service. 6.10 Why is it important for ... Many scheduling algorithms require the scheduler to make an estimate of the length of a process’s next CPU burst. At a minimum, this estimate should take into account the past behavior of the process. A crude estimate of this past behavior can be obtained if we can distinguish between I/O-bound and CPU-bound processes. In addition, if we schedule I/O-bound processes before CPU-bound processes, interactive programs will show better response times, and we can use the time between user-responses to schedule CPU-bound processes. 6.11 Discuss how the following pairs ... a. CPU utilization and response time If we want to minimize response time, the scheduler needs to favor interactive processes (which tend to be IO-bound) over CPU-bound jobs. Because IO-bound jobs tend to have smaller CPU bursts, the scheduler will run more often, resulting in a lower CPU utilization, since the CPU will be running kernel code (and not user programs) more often. Note, however, that if
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there are not enough CPU-bound jobs to keep the processor busy, CPU utilization will be low no matter how we schedule.
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  • Winter '15
  • ghonaim
  • Central processing unit, Scheduling algorithm, Scheduling algorithms, READY QUEUE, Dynamic priority scheduling

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