UNIVERSITY OF HOUSTON Department of Computer Science COSC 6360: Operating Systems FINAL EXAMINATION Part I: General Questions QUALIFYING EXAMINATION Part A: Graduate Topics May 7, 1992 CLOSED BOOK: You may have with you two sheets of notes. 1. In their latest paper on Amoeba, Tanenbaum et al. state that: The scheduling of threads within a process is done by code within the process itself. When a thread blocks, either because it has no work to do (i.e., on a GET_REQUEST) or because it is waiting for a remote reply (i.e., on a DO_OPERATION), the internal scheduler is called, the thread is blocked and a new thread can be run. Contrast their approach with other implementations of threads and highlight its benefits. (20 points) 2. With today's large address spaces, it becomes feasible to MAP entire files in the virtual address spaces of the processes accessing the file. Consider a mapped file system with the following two operations: ptr = map (filename, access), which maps the file into the virtual address space of the calling process and returns the starting address of the mapped file, and unmap(), which undoes the mapping. Note the absence of read() and write() primitives. Describe in some detail a possible implementation of a distributed MAPPED file system providing UNIX sharing semantics. (20 points) UNIVERSITY OF HOUSTON Department of Computer Science COSC 6360: Operating Systems FINAL EXAMINATION Part II: Specific Questions May 7, 1992 CLOSED BOOK: You may have with you two sheets of notes. 1. What are the two new system mechanisms that have been added to the Ninth Edition Unix System? (10 points) Explain in a few lines how these mechanisms can be used to establish a network connection between two processes. (5 points) THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN THE READING LIST. IT WILL BE NOT BE ASKED AGAIN. 2. State in two or three lines the most important limitation of STATELESS file servers. (5 points) 3. Describe in some detail the sharing semantics of Andrew. (10 points) 4. What is a VERSION VECTOR? (5 points) How can version vectors be used to detect inconsistencies between replicas of the same file? (5 points) 5. According to Liskov et al., what is the major benefit of adding uninterruptible power supplies to all HARP servers? (10 points) 6. How does the Bullet file server store files on disk? Why? (5 points) 7. Explain in a few lines what Nelson et al. mean by "Sequential Write Sharing." (5 points)