dirty pagetable

A dirty page table refers to a page table that has some of its entries marked as "dirty". In the context of virtual memory systems, a dirty page refers to a page of memory that has been modified or written to since it was last loaded from disk. When a page is marked as dirty, it indicates that its contents have changed and need to be saved back to disk before the page can be evicted from memory.

The dirty bit in a page table entry is typically set by the memory management unit (MMU) whenever a write operation is performed on a page. The operating system can then use this information to determine which pages need to be written back to disk during the page eviction process.

Maintaining a dirty page table allows the operating system to efficiently manage memory by prioritizing the eviction of dirty pages. Dirty pages must be written back to disk before they can be reused, and by keeping track of which pages are dirty, the operating system can avoid unnecessary disk I/O operations.

Overall, a dirty page table is an essential component of virtual memory systems that helps to ensure data integrity and optimize memory management.