Using the Virtual Memory Template, fill out the tables and answer the questions listed below.
- Consider a demand-paging system with the following time-measured utilizations:
CPU utilization 20%
Paging disk 97.7%
Other I/O devices 5%
For each of the following, say whether it will (or is likely to) improve CPU utilization. Explain your answers.
- Install a faster CPU.
- Install a bigger paging disk.
- Increase the degree of multiprogramming.
- Decrease the degree of multiprogramming.
- Install more main memory.
- Install a faster hard disk or multiple controllers with multiple hard disks.
- Add prepaging to the page fetch algorithms.
- Increase the page size.
- What is the cause of thrashing?
- How does the system detect thrashing?
- Once it detects thrashing, what can the system do to eliminate this problem?
- A system provides support for user-level and kernel-level threads. The mapping in this system is one to one (there is a corresponding kernel thread for each user thread). Does a multithreaded process consist of (a) a working set for the entire process or (b) a working set for each thread? Explain.
- Consider the following page reference string:
7, 2, 3, 1, 2, 5, 3, 4, 6, 7, 7, 1, 0, 5, 4, 6, 2, 3, 0, 1.
Assuming demand paging with 3 frames, how many page faults would occur for the following replacement algorithms?
- LRU replacement
- FIFO replacement
- Optimal replacement
- 7. Calculate the effective access time for a demand-paged memory given a memory access time of 100 nanoseconds, a page fault service time of 6,000,000 nanoseconds, and a page-fault rate of 1 page fault out of every 10,000 access attempts. You must show your calculations to receive full credit on this question.
- Using the following page replacement algorithms, determine the number of faults in the following reference string given a physical memory size of 4 frames:
5 6 5 4 4 4 8 2 9 9 0 4 5 3 9 6 8 1 9 1 6 1 0 0 5
| Replacement algorithm | 3 frames |
| a. FIFO | |
| b. OPT | |
| c. LRU | |
| d. LFU | |
| e. MFU |
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