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The VAX VMS system uses a FIF

[问答题]

The VAX/ VMS system uses a FIFO replacement algorithm for resident pages and a free-frame pool of recently used pages. Assume that the
free-frame pool is managed using the least recently used replacement policy. Answer the following questions:
a. If a page fault occurs and if the page does not exist in the freeframe pool, how is free space generated for the newly requested page?
b.If a page fault occurs and if the page exists in the free-frame pool, how is the resident page set and the free-frame pool managed to make space for the requested page?
c.What does the system degenerate to if the number of resident pages is set to one?
d.What does the system degenerate to if the number of pages in the free-frame pool is zero?

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• When a page fault occurs and if the page does not exist in the free-frame pool, then one of the pages in the free-frame pool is evicted to disk, creating space for one of the resident pages to be moved to the free-frame pool. The accessed page is then moved to the resident set.
• When a page fault occurs and if the page exists in the free-frame pool, then it is moved into the set of resident pages, while one of the resident pages is moved to the free-frame pool.
• When the number of resident pages is set to one, then the system degenerates into the page replacement algorithm used in the free-frame pool, which is typically managed in a LRU fashion.
• When the number of pages in the free-frame pool is zero, then the system degenerates into a FIFO page replacement algorithm.

发表于 2018-03-23 21:57:38 回复(0)