dirty pagetable

A dirty page table, also known as a modified page table, is a data structure used by an operating system to keep track of which pages in the virtual memory have been modified (i.e., marked as "dirty") since they were last written to the disk.

When a process modifies a page in its virtual memory, the corresponding page table entry is marked as dirty. This indicates that the page needs to be written back to the disk before it can be replaced with another page. The dirty bit is set to 1 to indicate that the page is dirty, and set to 0 when the page has been written back to disk.

The dirty page table is used by the operating system's memory management system to decide which pages to flush to disk when there is a memory pressure or when a process terminates. By only writing back the dirty pages, the operating system can minimize the I/O operations and improve performance.

Overall, the dirty page table is an essential component of the virtual memory management system, allowing the operating system to efficiently manage and track modified pages in the system.