accessed and dirty (where a page has been accessed and whether it has been changed) You need to know "dirty" to know whether a page needs to be written back to

accessed and dirty (where a page has been accessed and whether it has been changed) You need to know "dirty" to know whether a page needs to be written back to a swap file (or needs to be duplicated in lazy copying cases), you may want to know "accessed" if you want to do the accounting to push out less often used pages when memory gets short