Multilevel Paging in OS
Entry of each page of a process is recorded into its page table. If page table size is greater than its frame then OS further divide the page table into equal frame size. So, that page table could easily be accommodate into the frame. it is all multilevel paging in OS.
Page Table Base Register value is stored in Outer most table of that process. We move outer most to inner most table to find the required address.
In the same way, if the size of second level page table is greater than frame size then we again divided 2 level page table into equal frame size and third level page table is generated and so on.
Multilevel paging with example
If there is a process of 8 pages and its page table size is 8MB while the frame size of main memory is 2MB. Then page table cannot fit into single frame so we have to load this table into multiple frames.
As size of Page table is 8MB so divide it into 4 equal page tables of 2MB each. These 4 page tables are loaded into different frames as shown in diagram.