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

$\begin{array}{ll} \text{COU Utilization} & 20 \% \\ \text{Paging disk} & 97.7 \% \\ \text{Other I/O devices} & 5 \% \end{array}$

Which of the following will probably improve CPU utilization?

  1. Increase the degree of multiprogramming
  2. Add pre paging to the page fetch algorithms
  3. Increase the page size
  4. none of the above
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A Increasing degree of multiprogramming will result in more trashing resulting in less CPU utilization.

 B  Add pre paging to the page fetch algorithms The CPU will get more data faster, so it will be more in use. This is only the case if the paging action is amenable to pre fetching (i.e., some of the access is sequential).

 C  Increase the page size Increasing the page size will result in fewer page faults if data is being accessed sequentially. If data access is more or less random, more paging action could ensue because fewer pages can be kept in memory and more data is transferred per page fault. So this change is as likely to decrease utilization as it is to increase it.
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