CS3013 Practice Final Exam

  1. Fragmentation:

    1. What kind of fragmentation do we have with paging? Given N processes in memory, how much fragmentation do we have?
    2. What kind of fragmentation do we have with fixed partitions? Given N processes each in size M memory partitions how much fragmentation do we have?

  2. Explain what happens in terms of the OS and the memory mangagement unit when a process accesses an address that is out of range (such as, the famous "segmentation fault"). Use as much detail as you can.

  3. Consider the following page reference string: 

        5,2,3,7,6,3,2,5,2,3,2
    How many page faults would occur for an Second-Chance algorithm using 3 frames? Assume pure demand paging so your first unique pages will all cost one fault each.

  4. Consider a demand-paging system with the following time-measured utilizations:

        CPU utilization:     90%
    Paging disk:         10%
    Other I/O devices:    8%

    Which (if any) of the following will (probably) decrease CPU utilization?

    1. Install a faster paging disk
    2. Increase the degree of multiprogramming
    3. Decrease the degree of multiprogramming
    4. Install more memory
    5. Upgrade to a higher-bandwidth network

  5. What is the locality of reference? How does demand paging take advantage of this in terms of a process' working set?

  6. Consider a paging system with the page table stored in memory:

    1. If a paged memory reference takes 220 nanoseconds, how long does a memory reference take?
    2. If we add associative registers, and we have an effective access time of 150 nanoseconds, what is the hit-ratio? Assume access to the associative registers takes 5 nanoseconds.

  7. Explain what happens when a process executes an exec() call in terms of the paging environment.

  8. What is the maximum number of disk I/O operations required to add a block to the end of the file a file descriptor of type:

    1. linked-list
    2. linked-list allocation with index
    3. i-nodes
    Assume the file descriptor and the data to be written is currently cached in memory, but nothing else is.

  9. Explain the principles behind the "top half" of an interrupt handler and the "bottom half."

  10. What is the role of the device independent layer of a device driver?

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