If a normal access to memory takes 100 ns and reading a page from disk takes 10 ms, what is the average memory access time (including page fault overhead) if the page fault occurs in 0.1% of the memory references? You may assume that there is no additional overhead due to TLB misses.
(A) 10 μs
(B) 15 ms
(C) 2000 ns
(D) 0.15 s


Answer: (A)

Explanation: Average memory access time (including page fault overhead) is,

= 0.1%*10ms + 99.9%*100ns 
= 10μs + 99.9ns 
≈ 10μs 

So, option (A) is correct.

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