Operating system question

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[Please use different color in your answer] Question 1. Briefly answer the following questions. (a), why is the protection of processes’ memory space important? Describe a scenario where absence of memory protection leads to problems. (b) What is MMU? Where is it found and how is it used? Question 2. Consider a system where the virtual memory page size is 1KB (1024 bytes), and main memory consists of 4 page frames, which are empty initially. Now consider a process, which requires 8 pages of storage. At some point during its execution, the page table is as shown below: Virtual page # 0 1 2 3 4 5 6 7 Physical page # Valid Flag No No 2 Yes 3 Yes No No 0 Yes 1 Yes 1. List the virtual address ranges that will result in a page fault. 2. Give the following ordered references to the virtual addresses (i) 4500, (ii) 8000, (iii) 3000, (iv) 1100, please calculate the main memory (physical) addresses. If there is a page fault, please use LRU based page replacement to replace the page. How which page will be affected and compute the physical addresses after the page fault. We assume the reference string is … 2 4 7 3 0 4 3 0 7 5 0 7 6 0 2 3 6 4 7 6 3 2 before the new reference. Question 3. Given a computer system with the following paging based addressing for virtual addresses. Please answer the following questions: 2 bits 5 bits 5 bits 5 bits 7 bits 1. 2. 3. 4. What is the size of the virtual address space? What is the page size? What is the maximum number of pages for a process? Given the system has a TLB hit ratio of 99% and page fault rate of 1%. Please formulate the effective memory access time. Question 4. Consider a system with 1MB of available memory and requests for 42KB, 396KB, 10KB, and 28KB. The system is using Buddy Allocation Algorithm. a). Show the amount of memory allocated for each request and the state of memory after each request. Assume there is no memory release. 1/2 b). Why does internal fragmentation occur with buddy allocation? How much internal fragmentation exists in this scenario? c). Why does external fragmentation occur with buddy allocation? How much external fragmentation exists in this scenario? In answering the questions, we are assuming the platform is either Linux or Windows on 32-bit x86. 5. Sometimes a program receives a segmentation fault by stack overflow, explain what the stack overflow is and discuss and root causes and how to deal with such fault? 6. What is the impact of page size on the system performance in terms of memory utilization and effective memory access time? 7. Why swapping is necessary for the memory management? 8. Compared to memory, what is the downside of the swapping space? 2/2
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