课程名称︰作业系统 课程性质︰必修 课程教师︰薛智文 开课学院：电资学院 开课系所︰资工系 考试日期（年月日）︰2019/06/19 考试时限（分钟）：180 试题 : This is an open-book and open-own-note exam. Please do answer with your own words in the ORDER of question number. Provide your own question definition if you feel it is not clear enough. Points will be deducted if your answer is difficult to read. You can write in Chinese and keep this paper. Have a nice summer vacation. 1. [10%] Suppose there is no deadlock prevention and detection implemented in a computer system. How do we make sure there is a deadlock happening? [5%] How do we find the processes involved in the deadlock? [5%] 2. [10%] Why do we need different sizes of a memory page? [5%] If we support different page sizes at the same time in an OS, what need to be changed in TLB? [5%] 3. [10%] Why we used to lock shared pages in memory? [5%]? For locking IO memory pages, is there any different reason? [5%]. 4. [10%] When implementing an application, we usually experiment in higher (application) level for flexibility or avoiding system crash, then move into lower (kernel, driver or even hardware) level for better performance. In what sample applications, we would tune in higher level for better performance [5%] and lower level for flexibility, respectively. [5%] 5. [10%] Any way to improve the design of working set for lowering the page fault rate? [5%] Why there are upper bound and lower bound to control page fault frequency? [5%] 6. [10%] Describe the key factors to make page fault a successful design to virtual memory management utilizing the secondary storage. [5%] When the space of secondary storage such as disk is not enough, how can we further use the tertiary storage such as tape? [5%] ◎ 黑板补充： tertiary 第三 7. [20%] Memory management and (disk) storage management use similar technologies. a. List 3 common ones. [1,2,2%] b. Describe 3 technologies which are better used in memory management but not in storage management, with the most significant reason in one sentence. [3*5%] excluding page fault. 8. [20%] For Project 2, please answer the following questions: a. Since it is a client-server program, how do we guarantee the correct behavior no matter how the set up orders of both sides? [5%] b. Where enforcing "Copy Semantics" might be beneficial in your design? [5%] c. Please describe the performance differences of different file sizes, buffer sizes, and implementations (synchronous or asynchoronous, ...). [10%] 8. [20%] For a multiprogramming system with many process, when a process needs to do I/O operations, it will send a system call to the operating system, but if the controller is busy, the process will be placed in the disk queue, allowing the operating system to execute or optimize later. There are some common disk scheduling algorithms: FCFS, SSTF, SCAN, C-SCAN, LOOK, C-LOOK a. Suppose there are totally of 200 cylinders on the disk, if it requests continuous read and write track 105, 45, 120, 130, 70, 111, and 155. Which scheduling algorithm results in the least disk arm moves, and how many? (Head start on the 50th track, the default direction is the direction of increasing) [7%] b. When the probability to read any track varies little (probability needs not to be fixed on each track), try to analyze the performance of the best and the worst scheduling algorithm? [4%] c. What applications are mostly suitable using FCFS, C-SCAN, SSTF, respectively? Why? [3*3%] --

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