Sp06 midterm 1-solutions - University of California,...

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Page 1/11 University of California, Berkeley College of Engineering Computer Science Division – EECS Spring 2006 Anthony D. Joseph Midterm Exam Solutions March 8, 2006 CS162 Operating Systems Your Name: SID AND 162 Login: TA Name: Discussion Section Time: General Information: This is a closed book and notes examination. You have 90 minutes 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 21 2 54 3 12 4 13 Total 100
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CS 162 Spring 2006 Midterm Exam March 8, 2006 Solutions Page 2/11 1. (21 points total) Short answer questions: a. (4 points) True/False and Why? Lottery scheduling can be used to implement any other scheduling algorithm. TRUE FALSE Why? FALSE . Lottery scheduling cannot implement strict priority scheduling, FIFO, or real-time scheduling. The correct answer was worth 2 points and the justification was worth an additional 2 points. b. (5 points) Inverted Page Tables: i) (3 points) Give a two to three sentence description of an inverted page table. An inverted page table uses a hash function to map virtual addresses to physical addresses. . ii) (2 points) Briefly (2-3 sentences) state the problem it is intended to solve. An inverted page table supports a large virtual address space while only requiring a physical page table that is proportional in size to the available physical memory (an forward page table would require physical memory proportional to the size of virtual memory). We did not give credit for answers that stated the only problem it solves is reducing the number of lookups to memory. c. (4 points) Why would two processes want to use shared memory for communication instead of using message passing? Your answer should be brief (no more than 5 sentences). Shared memory has higher performance because you avoid the context switch overhea d of using message passing through the kernel. We gave full credit only if your answer included both performance and context switch overhead.
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CS 162 Spring 2006 Midterm Exam March 8, 2006 Solutions Page 3/11 d. (4 points) We say that the operating system is an “illusionist”. Name two illusions that it provides: i) (2 points) Illusion #1: Any of the many illusions we’ve discussed were acceptable: exclusive access to CPU, memory, disk or I/O devices; “infinite” memory; etc. . ii)
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This homework help was uploaded on 01/30/2008 for the course CS 162 taught by Professor Kubiatowicz during the Spring '02 term at University of California, Berkeley.

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Sp06 midterm 1-solutions - University of California,...

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