Memory Page

Abstract

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• Smallest unit of memory managed by an OS

Important

The size of a memory page depends on the OS and hardware architecture. Usually, each page has a fixed size of 4 KB (you can check this using the command getconf PAGESIZE).

This 4 KB memory page represents a contiguous block of space in the Main Memory. However, two consecutive memory pages are not necessarily located in contiguous spaces within the main memory.

Page Number

• A number to identify a Memory Page

Dirty Memory Page

• Memory Page that has been modified in the Main Memory, and needs to be written back to secondary storage (Flash Memory or Hard Disk) to ensure consistency and data integrity

Memory Page Size

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• We need to find a fine balance overhead and flexibility when deciding the size of the Memory Page
• With more overhead, it comes with more flexibility, vice versa
• When we want more flexibility, we should reduce the memory page size, so we can more freely to manipulate the Main Memory with Virtual Memory. But that means we more space for Page Table to manage mapping

Caution

If the memory page size is too big, this may leads to a lot of wasted memory space. For example, the memory page size is 10MB, and my program needs 10.00001MB. The Kernel will issue 2 memory page that are 10MB each, this means 9.99999MB is wasted. Imagine I have a lot of programs with 10.00001MB in my computer, that means we waste almost half of the available main memory!