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Consider, 2 level paging , with Process P, Inner page table PTi, and outer page table PTo.

Now we know that P and PTi  are divided in various pages but PTo is in 1 page only.

So in order to run process P, we need few pages of P , few pages of PTi and complete PTo in main memory.

If PTi asks for a page of P which is not present in main memory , then thats a PAGE FAULT and that particular page of P will be loaded in.

Now the question is :

Q1)  If PTo asks for a page of PTi which is not present in main memory , then ,is that also a PAGE FAULT ?

Please explain.

If YES, then can it be extended to all k page tables ( for k-level paging) where PTk is the outermost page table of within 1 page.

If No, then why ?

Q2) If answer to above question is YES, then consider the two images below:

             Case 1 gives formula for EMAT , in case of no page fault ,which is correct.

             EMAT formula considering page faults( as per Q1 assuming YES)  is given in CASE 2

             but most of the EMAT formulas online and in books gave formula given in  CASE 3

         Why they have used formula given in case 3 and not in case 2 in case of page faults?

in Operating System by (25 points)
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