Fa99 midterm 2-solutions - University of California,...

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Page 1/12 University of California, Berkeley College of Engineering Computer Science Division – EECS Fall 1999 Anthony D. Joseph Midterm Exam #2 Solutions November 10, 1999 CS162 Operating Systems Your Name: SID: Circle the letters of your CS162 login (1 per line): a b c d e f g h i j k l m n o p q r s t u v w x y z a b c d e f g h i j k l m n o p q r s t u v w x y z TA Name / Section: This is a closed book examination. You have two hours to answer as many questions as possible. The number in parentheses at the beginning of each question indicates the number of points given to the question; there are 100 points in all. You should read all of the questions before starting the exam, as some of the questions are substantially more time consuming. Write all of your answers directly on this paper. Make your answers as concise as possible. If there is something in a question that you believe is open to interpretation, then please ask us about it! Good Luck!! Problem Possible Score 1 12 2 28 3 15 4 12 5 15 6 18 Total 100
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CS 162 Fall 1999 Midterm Exam #2 November 10, 1999 Solutions Page 2/12 1. (12 points total) True / False and Why . Circle the correct answer and provide a short reason for your answer: a. Doubling the block size in the UNIX 4.2 BSD file system will exactly double the maximum file size. True / False Why: False. The size will more than double because the size of indirect, doubly indirect, and triply indirect blocks also doubles. The correct answer was worth 2 points. Good reasoning was worth 2 points. b. A direct mapped cache can sometimes have a higher hit rate than a fully associative cache with an LRU replacement policy (on the same reference pattern). True / False Why: True. A direct mapped cache will do better than LRU on a pattern like ABCDEABCDE… if the cache size is one entry smaller than the total number of items in the pattern (e.g., four cache entries). LRU will miss on every access, while a direct mapped cache will only miss on the two entries that map to the same cache entry. c. Virtual memory address translation is useful even if the total size of virtual memory (summed over all programs) is guaranteed to be smaller than physical memory. True / False Why: True. It avoids the need to relocate programs when they are loaded and allows memory to be dynamically allocated. Also, provides protection and doesn’t require that each program’s addresses be contiguous.
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CS 162 Fall 1999 Midterm Exam #2 November 10, 1999 Solutions Page 3/12 2. (28 points total) File system buffer cache management. a. (12 points) Unix systems use a 30 second write-behind policy for file system data. List the advantages and disadvantages i) Name two advantages of this policy. (1) Delaying writes allows multiple small writes to be batched together into a
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This homework help was uploaded on 01/30/2008 for the course CS 162 taught by Professor Kubiatowicz during the Fall '02 term at University of California, Berkeley.

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Fa99 midterm 2-solutions - University of California,...

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