CS3013 Practice Third Exam

1. Assume you have a page reference string for a process with m frames (initially all empty). The page reference string has length p with n distinct page numbers occurring in it. For any page replacement algorithms:

   • What is a lower bound on the number of page faults?
   • What is an upper bound on the number of page faults?

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

       CPU utilization:     20%
       Paging disk:       97.7%
       Other I/O devices     5%
   

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

   1. Install a faster CPU
   2. Install a bigger paging disk
   3. Increase the degree of multiprogramming
   4. Decrease the degree of multiprogramming
   5. Install more main memory
   6. Install a faster hard disk, or multiple controllers with multiple hard disks
   7. Add pre-paging to the page fetch algorithms
   8. Increase the page size

3. Give some reasons why LRU is a good page replacement algorithm. Why is the theory behind it correct?

4. What would be the worst possible page replacement algorithm?

5. Explain why Belady's anomaly cannot occur in the optimal page replacement algorithm.

6. What are the potential advantages and disadvantages to writing a single-threaded program to writing a multi-threaded program?

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