When using physical addresses directly, there is no virtual to physical translation overhead. Assume it takes 100 nanoseconds to make a memory reference. If we used physical addresses directly, then all memory references will take 100 nanoseconds each.
What would the working set algorithm try to accomplish, and why? (Hint: These two cases represent extremes that could lead to problematic behavior.)
CPU utilization: 20%
Paging disk: 97.7% (demand, not storage)
Other I/O devices: 5%
For each of the following, say whether it will (or is likely to) improve CPU utilization. Briefly 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
For (g), the page-fetch algorithm is the page replacement algorithm. Prepaging is an optimization that tries to anticipate near-future page accesses by loading pages from disk that the page replacement algorithm predicts will be accessed soon, but before those pages are actually accessed (effectively prefetching those pages).