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Unformatted text preview: 9 C H A P T E R Virtual Memory Practice Exercises 9.1 Under what circumstances do page faults occur? Describe the actions taken by the operating system when a page fault occurs. 9.2 Assume that you have a page-reference string for a process with m frames (initially all empty). The page-reference string has length p ; n distinct page numbers occur in it. Answer these questions for any page- replacement algorithms: a. What is a lower bound on the number of page faults? b. What is an upper bound on the number of page faults? 9.3 Which of the following programming techniques and structures are “ good ” for a demand-paged environment ? Which are “ not good ” ? Ex- plain your answers. a. Stack b. Hashed symbol table c. Sequential search d. Binary search e. Pure code f. Vector operations g. Indirection 9.4 Consider the following page-replacement algorithms. Rank these al- gorithms on a five-point scale from “ bad ” to “ perfect ” according to their page-fault rate. Separate those algorithms that suffer from Belady’s anomaly from those that do not. a. LRU replacement 17 18 Chapter 9 Virtual Memory b. FIFO replacement c. Optimal replacement d. Second-chance replacement 9.5 When virtual memory is implemented in a computing system, there are certain costs associated with the technique and certain benefits. List thecertain costs associated with the technique and certain benefits....
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This note was uploaded on 11/03/2009 for the course IT OS taught by Professor Dr.stephan during the Winter '09 term at Abu Dhabi University.
- Winter '09
- Operating Systems