Page managment

Question

I want to divide a page table into 2 page tables (outer and inner). Single page table has 2^20 entries with Page Size of 2^5 Bytes and Page Entry of 4Bytes in Page Table.  
What should be the number of entries in Outer Page Table? What is the formula ?

Comments

inner page table size =2²⁰ * 2²

                                              =2²²

no of entries of page table = 2²²/ 2⁵

                                                =2¹⁷  ( entries)

Answer 1

Outer Page Table	Inner Page Table	Page Size
17	3	5

Number of entries in Outer Page Table = 2^20 * 2^2 / 2^5. = 2^17. 

Don't remember the formula rather understand the logic. We divide the inner page table into size of Page Size so that one Page Table could fit into one frame size. Size of single level Page Table = 2^20 * 4B = 2^22B.

Now divide 2^22  by 2^5 to get 2^17 page tables of size 2^5 each. So for 2^17 page Tables you need 2^17 entries in outer Page Table to select Inner Page Table and rest 3 bits for entry in Inner Page Table.