Several fault-breaking algorithms in virtual storage management

Source: Internet
Author: User

Page break is to access the pages are not main memory, the operating system needs to be transferred into main memory before access.

In memory access, if the page accessed is already in main memory, it is said that the visit was successful;

If the page visited is not in main memory, it is said that the visit failed and a fault was generated.

Best Replacement Method:

For example, suppose the system allocates 3 physical blocks for a process, and the order of the pages accessed by the process is 0,7,6,5,7,4,7,3,5,4,7,4,5,6,5,7,6,0,7,6. Request a page break during access?

Answer: The process runs 0,7,6 three pages into memory first, when access to the 5th, resulting in a page break, according to the best substitution method, (will not be accessed for the longest time in the future), page 0 will be accessed 18 times, so it is the longest page in this three page is not accessed, So the elimination of replacement, will be 5 in exchange. Then go to page 7th, because page 7th is in memory, so there will be no missing pages, and so on ...

With the best permutation algorithm, 9 page faults were generated, and 6 pages were replaced.

Several fault-breaking algorithms in virtual storage management

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