ecs150 fall 2010 midterm

1. ecs150 fall 2010 midterm Name: Student ID: Email: Open book and totally 3 questions (4%/8% each), 8 pages. Please write precise and clean answers (should be around half to one full page). But, please do not leave it blank there as I will give partial credits. Please READ the questions VERY CAREFULLY before putting down the final answer. And, also please mark your answer clearly. You can use the back of the pages. Every page of this exam book needs to be returned back. Also, while turning in your exam book, please make sure to SIGN the special sign-up sheet. If you do NOT sign up and in case WE LOSS your exam book, it will be hard to convince us that you actually turn in the exam book back to us. If we suspect any cheating behavior, we will pass the case to the academic committee immediately. Score: ___/16 ecs150 fall 2010, midterm exam

2. Q-01 (Scheduler Activation/KSE, 4%) Please explain briefly the advantage of Scheduler Activation over a pure UTS (User-level Thread Scheduler) system or a pure KTS (Kernel-level Thread Scheduler) system? When a user-level thread made a system call to the kernel, the scheduler activation mechanism will detect and make a upcall to the UTS about this activity. The UTS then can re-assign a different/ready user level thread to run on the KSE to avoid idle CPU. ecs150 fall 2010, midterm exam

3. Q-02 (I-Node, 4%) Given the following parameters of UFS2 I-node: di_size (the logical size of the file) 8 bytes block-size 4096 bytes Please write down the largest file that we can represent using this I-node specification. Please explain how you derive the answer. 212/23 = 29 pointers per block 12*212 + 29*212 + 29*29*212 + 29*29*29*212 264-1 264*212 The smallest is the first one (~239 bytes) ecs150 fall 2010, midterm exam

4. Q-03 (Priority Inversion, Inheritance, and Ceiling, 8%) This question is regarding priority ceiling protocol. Somewhat similar to the example we went over in the class, the following diagram shows four tasks and their independent execution sequences, of course, assuming no contention of any resources: 1 L L S1 S2 L 2 L L S2 S1 L 3 L L 4 L S2 S2 S2 S2 L 0 2 4 6 8 10 12 14 16 18 The meanings of the labels are: L: Local execution, B: blocked, Si: Semaphore I, C: Ceiling-Driven blocking, F: Finishing, P: Preempted. Please use the charts in the next few pages to lay out the schedules (using the label characters above) for regular priority scheduling (i.e., without solutions like priority inheritance, ceiling, and emulation), basic priority inheritance, priority ceiling, and priority ceiling emulation. Please also put down the effective prioritywhen priority inheritance occurs. Also, if you encounter a deadlock, please point it out as well. ecs150 fall 2010, midterm exam

5. Regular Priority Scheduling 1 L L S1 B B B B B S2 L 2 L L P P P B B B B B P P S2 S1 L 3 P P P P P L L 4 L S2 P P P P P P P S2 S2 S2 P P P P P L 0 2 4 6 8 10 12 14 16 18 ecs150 spring 2009, FINAL exam

6. Basic Priority Inheritance 1 L L S1 B B B S2 L 2 L L P P P P/B P/B P/B P P S2 S1 L 3 P P P P P P P P P P P P P L L 4 L S2 P P P P P S2 S2 S2 P P P P P P P L 0 2 4 6 8 10 12 14 16 18 ecs150 spring 2009, FINAL exam

7. Priority Ceiling Protocol 1 L L C C C S1 S2 L 2 L L P P P/B P/B P/B P P P S2 S1 L 3 P P P P P P P P P P P P P L L 4 L S2 P P P P S2 S2 S2 P P P P P P P P L 0 2 4 6 8 10 12 14 16 18 ecs150 spring 2009, FINAL exam

8. Priority Ceiling Emulation 1 P L L S1 S2 L 2 P P P P P P P P L L S2 S1 L 3 P P P P P P P P P P P P P L L 4 L S2 S2 S2 S2 P P P P P P P P P P P P L 0 2 4 6 8 10 12 14 16 18 ecs150 spring 2009, FINAL exam