Consider a demand-paging system with the following time-measured utilizations: C

Question

Consider a demand-paging system with the following time-measured utilizations:

CPU: 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.

a. Install a faster CPU.

b. Install a bigger paging disk.

c. Increase the degree of multiprogramming.

d. Decrease the degree of multiprogramming.

e. Install more main memory.

f. Install a faster hard disk or multiple controllers with multiple hard disks.

g. Add prepaging to the page fetch algorithms.

h. Increase the page size.

Explanation / Answer

a. No this won't help since the CPU is under utilized.This will likely have no effect. The limiting factor is available memory per program. b.No, this won't help because the problem is speed of retrieval not the amount of room needed. c.No, this will mean still fewer frames per process and more thrashing making the problem worse.This typically decreases CPU utilization because less memory is available to each program and the chances of page faults increase. d.Yes, this will help. Fewer process, more frames per process and less thrashing.This typically increases CPU utilization by keeping more of the working set of each program in memory, thereby reducing the number of page faults. e.Yes, this will help. More frames in memory so less thrashing. f.No, won't help. The paging disk is the problem not other disks. g.This is increase CPU utilization by avoiding page faults by having the pages pulled into memory before they

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