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I am getting confused with calculation of EEMAT(Effective memory access time). I decided to close the book and think on my own and make an equation. Please see whther this is correct or not. I thought a lot and also refereed google but i am lost. Please help!

Let TLB hit ratio = x.

TLB access time = c

main memory access time = m

page fault rate = p; page fault service time = S

First i will access TLB. In case of TLB hit i will directly access main memory(so time here = c+m in case of TLB hit)

If TLB Miss, then i will have to access via page table. I am assuming here n level page table(so n page tables needed to access main memory).

In case of TLB Miss, i will access page table(n level) --> it can be hit or miss. If page hit, then time = c+(n+1)m

If page fault, time = c+m+(n+1)m --> TLB access time + first i access page table to know that there is no valid frame in 1st level page table itself(i got another doubt here, in case of page fault in n level paging, valid bit is 0(invalid page) in 1st level or any of n levels or in nth level page table???) + n level page table access in main memory + finally main memory

So EEMAT = x(c+m)+(1-x){ (1-p)[(n+1)m] + p[S + m + (n+1)m ] }

Is this correct???

  • My another doubt:

in case of page fault in n level paging, valid bit is 0(invalid page) in 1st level or any of n levels or in nth level page table???

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  • $\begingroup$ We discourage "please check whether my answer is correct" questions, as only "yes/no" answers are possible, which won't help you or future visitors. See here and here. Can you edit your post to ask about a specific conceptual issue you're uncertain about? As a rule of thumb, a good conceptual question should be useful even to someone who isn't looking at the problem you happen to be working on. If you just need someone to check your work, you might seek out a friend, classmate, or teacher. $\endgroup$ – D.W.♦ Dec 12 '19 at 17:48
  • $\begingroup$ sir i am a mechanical engineering student and learning OS on my own. Atleast please clarify my query and then downvote or delete my post. $\endgroup$ – Nascimento de Cos Dec 12 '19 at 22:07

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