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Question

A demand paging system has page fault service time as 125 time units if page is not dirty and 400 times units of page fault service time if it is a dirty page. Memory access time is 10 time units. The probability of a page fault is 0.3. In case of page fault, the probability of page being dirty is P. It is observed that average access time is 50 time units. Then, the value of P is ______? [upto four decimal places]

Answer 1

This is the standard formula from Galvin.

but sometimes it is also used as  EMAT = p(Page fault service time) + mem access time  (I am also confused,when to use what)

Comments

the above answer is wrong according to concept of page fault,because after servicing a page fault you search in the main memory again..

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But it was given in Galvin