Operating Systems 1. Consider a demand-paged computer system where the degree of

Question

Operating Systems

1.       Consider a demand-paged computer system where the degree of multiprogramming is currently fixed at four. The system was recently measured to determine utilization of CPU and the paging disk. The results are one of the following alternatives. For each case, what is happening? Can the degree of multiprogramming be increased to increase the CPU utilization? Is the paging helping?

a. CPU utilization 13 percent; disk utilization 97 percent.

b. CPU utilization 87 percent; disk utilization 3 percent.

c. CPU utilization 13 percent; disk utilization 3 percent.

Explanation / Answer

a. Thrashing is occurring, since the disk utilization is very high while the CPU is underutilized. Processes are spending most of their time paging. The degree of multiprogramming cannot be increased. On the contrary, one or more processes should be suspended to allow increase in the utilization of the CPU.

b. CPU utilization is sufficiently high to leave things alone. Any increase in the degree of multiprogramming could lead to thrashing.

c. Increase the degree of multiprogramming. The CPU is available for executing additional processes.

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