GATE | GATE CS 2021 | Set 1 | Question 21

In the context of operating systems, which of the following statements is/are correct with respect to paging?
(A) Paging helps solve the issue of external fragmentation
(B) Page size has no impact on internal fragmentation
(C) Paging incurs memory overheads
(D) Multi-level paging is necessary to support pages of different sizes


Answer: (A) (C)

Explanation: (A) True.
Paging helps solve with external fragmentation in two ways.

• First, it subdivides memory into fixed-size adjacent chunks – the pages – that are “large enough” so they’re never useless.
• Second, the paging hardware provides a level of indirection between application pages and physical memory pages.

(B) False.
There is no external fragmentation in paging but internal fragmentation exists. Large pages will also waste more space with internal fragmentation.

(C) True.
In general, smaller page sizes lead to lesser internal fragmentation (i.e., space being unused in the last page of the process). However, smaller pages also imply greater overhead in storing page tables.
Implementation of Paging requires management of Page tables which resides in pages and hence consume additional memory.

(D) False.
Multilevel Paging is needed when the size of page table is greater than the frame size. Since page table reside in page, it is further divided to pages of same size.


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