課程名稱︰作業系統 課程性質︰必帶 課程教師︰薛智文 開課學院：電資學院 開課系所︰資訊系 考試日期（年月日）︰103/6/18 考試時限（分鐘）：9:10 ~ 12:10 是否需發放獎勵金：是 （如未明確表示，則不予發放） 試題 : 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%] Please describe how to set the niceness values for the scheduling algorithms FIFO, RR, and, SJF. [3*2%] In Linux, why can't we get the desired scheduling under some circumstances? Please give two examples and explain why? [4%] 2.[10%] When implementing blocking I/O in a kernel module, it is common to establish a shared data buffer between kernel threads and user processes. Please describe how we can use wait_event to ensure the correct behavior even if there are no data available in the buffer.[5%] What's the difference between wait_event and wait_event_interruptible?[5%] 3.[10%] In Linux, a file can be mapped into memory via the system call mmap. Please describe an efficient implementation exploiting demand paging and data buffer to minimize both initialization time and access time.[5%] Suppose a file is mapped into two different address spaces with the flag MAP_PRIVATE at the same time. How can we make sure that any updates to the mapped memory region in one process are invisible to other processes, and are not carried through to the underlying file? Please explain your solution with an example. [5%] Hint: void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset); 4.[10%] Find a save (from deadlock) sequence if any.[5%] Find the maximal request of P_4 that can be granted at current stage.[5%] Allocation Need Available A B C A B C A B C P_0 0 1 0 7 4 3 3 3 1 P_1 3 0 1 5 0 0 P_2 3 0 2 0 4 0 P_3 2 2 1 1 2 0 P_4 0 0 2 3 4 1 5.[10%] Why Raid(1+0) is preferable than Raid(0+1)?[5%] How Raid technologies can be extended to wireless broadcast systems?[5%] 6.[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 one management but not in the other, with reasons.[3*5%] 7. [20%] In Project 2, we need to guarantee the following orders. ● The slave program will be executed only after both device modules have been loaded ● The master program will be executed only after the master device module has been loaded ● In the slave program, it first set the IP address and then begin reading data from the slave device with blocking I/O. a. Why do we guarantee them in device driver instead of in applications?[5%] b. What happen if they are not guaranteed?[5%] Hint: Can the master and slave still be connected? c. Can implementation by asynchronous I/O outperform synchronous I/O?[5%] d. What is the difference between nonblocking I/O and asynchronous I/O?[5%] 8. [20%] For a multiprogramming system with many process, when a process need I/O operation, 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 choose. There are some common disk scheduling algorithms: FCFS, SSTF, SCAN, C-SCAN, LOOK, C-LOOK a. Suppose there is the total of 200 cylinders on the disk, if it requests continuous read and write 110, 60, 120, 131, 70, 111, 130. Try to find which scheduling's disk arm moves the least distance? (Head start on 50th track, the default direction is the direction of increasing)[7%] b. When the operating system reads the track which is evenly distributed, try to analyze the performance of SCAN and C-SCAN? [4%] c. What application is mostly suitable using FCFS, SSTF, C-SCAN, respectively? Why?[3*3%] --

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