Homework 9 Operating Systems ACSI 400 UAlbany, SUNY

1. 1. Explain the difference between a page and a page frame.
   2. Discuss one disadvantage of a system that always has more page frames than pages it uses. Hint: Think about money.
   3. Discuss one disadvantage of a system that frequently uses more pages than it has page frames.
   4. Discuss one advantage for EACH of the above two situations.
2. Discuss the difference between the (1) "segment" described by a "segment descriptor" as used in OSCJ Figure 9.21 and (2) the Linux "memory region" described in Chapter 8 of ULK. (The term "segment" is usually used to mean memory region in Unix technical literature.)
3. OSCJ Problems (10.1) and (10.3). Assume 11123456 is hexadecimal and 32, 18 and 4,096 are decimal numerals.
4. 1. OSCJ (10.4). Find out about any of the techniques and structures you don't know from the textbooks, data structures or algorithms textbooks, the Web, or by asking people--exercise some judgement of course.
   2. Describe a simple C/C++ program that will cause terrible virtual memory performance when it is run. DO NOT RUN such a program except on your own personal computer.
5. OSCJ (10.5) and (10.17).
6. OSCJ (10.11) Show how you figured out which references caused page faults.
7. Demonstrate Belady's anomaly by showing how FIFO replacement works on the reference string on page 382 for number of page frames equal to 3 and 4.
8. Prove that Belady's anomaly cannot occur with OPTIMAL replacement. You may use the result that the latest first future use algorithm is optimal, but it is easier to give a proof based on the definition of what it means to be optimal. Hint: Suppose somebody makes believe that there are fewer page frames than there really are.
9. OSCJ (10.20).