Performance of 2-level Paging

28 Dec, 2020
In this article, we are going to discuss the performance of 2-level paging and also will discuss how we can evaluate an expression for evaluating the performance of 2-level paging. Let’s discuss one by one.
Pre-requisite: Paging in OS | 2-level Paging And Multi-level Paging
Performance of 2-level Paging :
Let’s consider the main memory access time is M. Page tables are stored in the main memory then the formula for effective memory access time.
Effective Memory Access Time(E.M.A.T) = 3M

Features :
The TLB is added to improve the performance of paging.
The TLB contains frequently referred page numbers and corresponding frame numbers.
Evaluating Expression for Performance of 2-level Paging :
Let’s consider the TLB access time is C. And TLB hit ratio is x then the formula for E.M.A.T as follows.   
E.M.A.T = x(C+M) + (1 - x)(C+3M)
                           |
                           |
                        N-level Paging
E.M.A.T = x(C+M) + (1 - x)(C+ (N+1)M)

Important points for Performance of 2-level Paging :
In multi-level paging when paging is applied on page table. The last page table which we get is called the 1st level page table.In the multi-level paging when multiple paging is applied on the page table the first level page table entry contains the base address of the 2nd level page table, The 2nd level page table entry contains the base address of the 3rd level page table, and so on.In the multilevel paging when paging is applied on the page table then whatever may be the level of paging all the page table (page of page table) will be stored in the main memory.In multilevel paging when paging is applied on the page table then whatever may be the level of paging all the page table entry contains frame number.If the page size is not mentioned in the problem then generally page size will be the same in all the places(Levels).
In multi-level paging when paging is applied on page table. The last page table which we get is called the 1st level page table.
In the multi-level paging when multiple paging is applied on the page table the first level page table entry contains the base address of the 2nd level page table, The 2nd level page table entry contains the base address of the 3rd level page table, and so on.
In the multilevel paging when paging is applied on the page table then whatever may be the level of paging all the page table (page of page table) will be stored in the main memory.
In multilevel paging when paging is applied on the page table then whatever may be the level of paging all the page table entry contains frame number.
If the page size is not mentioned in the problem then generally page size will be the same in all the places(Levels).
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