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Page: PmWiki.Homework3 - Last Modified : Wed, 11 Nov 09

  • Consider the Solaris multithreaded feedback queue system. In this system, scheduling is controlled by a table, as shown below. For each priority, the table gives: (1) the time quantum for the priority, (2) the priority a process moves to if it uses up this quantim, (3) the priority it gets if it sleep before exhausting the quantum (called Wakeup), (4) the maximum waiting time, meaning how long can the job be in the ready queue without running, and (5) the new priority if the job exceeds its waiting time in the ready queue (Max Wait prio). In the table below, times are given in miliseconds. A job runs at its priority, and if it its quantum expires, it moves to the quantum expired priority and continues running its current burst of work. If a job waits or sleeps before the quantum expires, then when it wakes up, it runs at the Wakeup priority.
PriorityTime Quantum msecQuantum Expired PrioWakeup PrioMax Wait msecMax Wait Prio
  1. What is the highest priority in this system, and why?
  2. Consider a job that is CPU bound for the first minute (it runs without waiting or sleeping) and then becomes I/O bound and waits every 1 msec for the next minute. What will its final priority be?
  3. Consider a job that has a CPU burst of 11 msec. What will its priority be after it has run for a long time?
  • Consider a logical address space of 128 pages of 1024 bytes each, mapped onto physical memory of 32 frames
    1. How many bits are there in the logical (virtual) adddresses?
    2. How many bits are there in the physical addresses?
    3. Draw a picture showing how, with a single page table, logical addresses are converted into physical addresses
  • On a system with paging, a process cannot access memory that it does not own. Why? How could the operating system allow access to other processes' memory? Why should it or should it not?

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