2 votes

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?