Paging is a memory management function in which a computer stores as well as retrieves data from the system’s secondary storage to primary storage. The process of memory management is very crucial for every computing system, and paging is particularly necessary for virtual memory implementation.
In this article, we will look more into the Size of the Page Table according to the GATE Syllabus for (Computer Science Engineering) CSE. Let us read ahead to find out more about it.
Table of Contents
What is the Size of the Page Table?
The part of a given process that is getting executed by a CPU should be present in the system’s main memory during that very time. Also, the page table must be present in this main memory (precisely all the time) since it consists of the entry for all of the pages.
Note that the size of a page table depends entirely on the total number of entries given in the table, along with the number of bytes stored in a single entry.
Now, let us consider the following:
Logical address space = 2 ^ 24 bytes
Logical address = 24 bits
If, page size = 4 KB = 2 ^ 12 bytes
and page offset = 12
Then the total number of bits in the page = Logical address – page offset = 24 – 12 = 12 bits
Total number of pages = 2 ^ 12 = 2 X 2 X 10 ^ 10 = 4 KB
Now let us say, page table entry = 1 byte
Thus, the page table size = 4 KB X 1 byte = 4 KB
We are lucky here to get the page frame equal to the table size. Thus, the page table would be stored simply in one frame present in the main memory. Also, the Central Processing Unit maintains a register. It consists of the base address of this frame. All the page numbers from a logical address would be first added to this base address. This way, we can access the real location of the word that is being asked.
However, in certain cases, the frame size and the page table size might not even be the same. In such cases, the page table can be considered as a collection of frames. It will get stored in various different frames.
What is the Maximum Size of a Page Table?
Page size is assigned to all tables produced within a tablespace with a specific size. With a 32-KB page size, a single table or an index object could be as large as 64 TB. The total number of levels in an index can be reduced by using larger page sizes.
Optimal Page Size
The optimal page size is the one that has the least amount of overhead. Read more on finding optimal page size here. It can be given as follows:
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