multilevel paging

Question

In a 32-bit machine we subdivide the virtual address into 4 segments as follows: 
 

10-bit

8-bit

6-bit

8 bit

We use a 3-level page table, such that the first 10-bit are for the first level and so on.

1. What is the size of a page table for a process that has 256K of memory starting at address 0?

How to solve such questions?? please someone answer it with proper explanation

Comments

page table entry size?

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if PTE size is not given then we can use frame no bits...
http://www.cs.utexas.edu/~lorenzo/corsi/cs372h/07S/hw/3sol.html

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2 bytes.

Answer 1

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Comments

@Debashish Deka

"The Process that has 256K of memory starting at address 0"

Does it mean the 256KB is the logical address space  or it is the physical memory consumed by the process

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page entry size is not given nor physical address given  how you decide page entry size is 2?

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This is a good example of "page size need not be equal in all levels of page table".

In 3rd level each page can hold $2^{6}$ entries.

2nd level each page can hold  $2^{8}$ entries.

1st level each page can hold $2^{10}$ entries.

assuming page table entry size is same in all levels.

Answer 2

1. The page field is 8-bit wide, then the page size is 256 bytes.
2. Using the subdivision above, the first level page table points to 1024 2nd  level page tables, each pointing to 256 3rd page tables, each containing 64 pages. The program's address space consists of 1024 pages, thus we need we need 16 third-level page tables. Therefore we need 16 entries in a 2nd level page table, and one entry in the first level page table. Therefore the size is: 1024 entries for the first table, 256 entries for the 2nd level page table, and 16 3rd level page table containing 64 entries each. Assuming 2 bytes per entry, the space required is 1024 * 2 + 256 * 2 (one second-level paget table) + 16 * 64 * 2 (16 third-level page tables) = 4608 bytes.

Comments

"1024 entries and hence cannot fit inside a page"

• 1st level will consume = $1024*2 = 2048$B
• it will not fit in one frame.

then it will take more frames. 

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Yes! answer is COPIED..Because the question is same!

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Can you please explain me this. I am very confused . Not getting this .