※ [本文转录自 NTU-Exam 看板 #1NnoihGd ] 作者: SahsB (SahsB) 看板: NTU-Exam 标题: [试题] 104下 郭大维 作业系统 期末考 时间: Thu Sep 1 03:08:24 2016 课程名称︰作业系统 课程性质︰必修 课程教师︰郭大维 开课学院：电资 开课系所︰资工 考试日期（年月日）︰2016.06.29 考试时限（分钟）：150 试题 : Operating Systems Final Exam Spring 2016 The exam is 150 minutes long. The total score is 100pts. Please read the questions carefully. 1. Terminologies (21pts). a. Absolute Code b. Physical Address c. Swapping Out (Hint: Virtual Memory Management) d. Address-Space Identifiers(ASID) in TLB e. Non-Uniform Memory Access (NUMA) f. i-node (Hint: File System) g. File-System Mounting Point 2. There are 4 necessary conditions for deadlocks: Mutual Exclusion, Hold and Wait, No Preemption, and Circular Wait. Please explain the relationship between Hold and Wait and others? (10pts) 3. Given the following snapshot of the system: Please determine whether there is a deadlock? If there is a deadlock or more, you must show me which processes are in any deadlock. If not, please provide me a sequence such that Finish[i]=0 for all i. (5pts) ┌─┬──────┬─────┬──────┐ │ │ Allocation │ Request │ Available │ │ │ ---------- │ ------- │ --------- │ │ │ A B C │ A B C │ A B C │ ├─┼──────┼─────┼──────┤ │P0│ 1 2 0 │ 1 0 1 │ 1 0 0 │ ├─┼──────┼─────┼──────┤ │P1│ 1 0 2 │ 0 0 1 │ │ ├─┼──────┼─────┼──────┤ │P2│ 0 1 0 │ 0 0 0 │ │ ├─┼──────┼─────┼──────┤ │P3│ 0 0 1 │ 1 0 1 │ │ ├─┼──────┼─────┼──────┤ │P4│ 1 1 0 │ 0 0 0 │ │ └─┴──────┴─────┴──────┘ 4. When Contiguous Allocation is considered in memory allocation, consider Dynamic Partitioning. Please compare First-Fit and Best-Fit Algorithms. (6pts) 5. Given the following reference string, which reference causes a page fault under the LRU algorithm. Please also show us which page is replaced when a page replacement occurs? Suppose that we have 3 available frames, which are empty initially. (6pts) 0 1 1 2 1 3 5 3 1 2 0 2 1 3 0 4 5 1 6. Please answer thede questions for memory management. You must provide explanation to receive any credits. (25pts) a. What is the advantage in having large pages and small pages simultaneously? Please give me two reasons. (10pts) b. How the Modify Bit helps in improving Demand Paging? (5pts) c. How the Additional-Reference-Bits helps in improving Demand Paging? (5pts) d. How remembering which page was in each frame of the pool (in Page Buffering) helps in improving Demand Paging? (5pts) 7. Why the introduction of Symbolic Link might cause looping in tracing a path name? (6pts) 8. Consider IA-32 Segmentation, as shown below: We have 8K private segments and 8K public segments. g is the selector to choose which kind of descriptor table to use. Assume that we always have a 2-level paging. Let the system be byte-addressable. Suppose that the frame number needs 6 bytes to store. Please answer the following questions: (21pts). Selector │ Segment Offset ┌───┬─┬─┬────────┐ Logical Address │ s │g │p │ sd │ └───┴─┴─┴────────┘ 13 1 2 │ 32 ┌──┬──┬──┐ Linear Address │ p1 │ p2 │ d │ └──┴──┴──┘ 10 10 12 a. What would be the page size? What is the maximum number of pages that a process can have. What is the maximum size of a segment? (9pts) b. Notice that IA-32 has segmentation and then paging in address translation. Let the memory access time be 100ns. Without TLB, what is the effective memory access time? (6pts) c. Suppose that TLB is adopted only for paging (not for segmentation). Let the memory access time and TLB access time be 100ns and 10 ns, respectively. When the TLB hit ratio is 99%, what is the effective memory access time? (6pts) --

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