Memory Management

Question

Which of the following are true about of paging ?

1) It divide the memory into units of equal size

2)It permits implementation  of  virtual memory

3)It suffers from Internal Fragmentation

option a) 1 b ) 2 c) 3 d) 1,2,3

Answer 1

Paging divides memory in equal size pages.It suffers from internal fragmentation (on an average (page size)/2) at very last level of page. Paging also implement virtual memory.

All are true,

Comments

yes :) I concluded the fragmentation point from optimal page size !

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Optimal page size : size of page with minimum overhead.

Overhead = Page Table Size + (Lastlevelfragmentation i.e. P/2)

If fragmentation (not only fragmentation, other overhead also) then OPTIMAL PAGE SIZE.

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i know it ! i just wanted to verify

Answer 2

Ans :  d ) 1,2,3 

            1 , as in paging main memory is divided into "frames" of equal size  and the logical memory is divided into "pages"  .

                 page size = frame size

            2 as Paging is an important part of virtual memory implementations in modern operating systems ..

             ( source wikipedia)   

            3  . Lets see an example from Galvin.   If page size is 2,048 bytes, a process of 72,766 bytes will need 35 pages plus                       1,086 bytes. It will be allocated 36 frames, resulting in internal fragmentation of 2,048−1,086= 962 bytes. In the worst                   case, a process would need n pages plus 1 byte. It would be allocated n+ 1 frames, resulting in internal                                       fragmentation of almost an entire frame.