Paging supervisor:

This part of the operating system built and manages the page tables. If the  due to dynamic address translation hardware a page fault occurs exception then the paging supervisor searches the page space on secondary storage for the page containing the needed virtual address, reads it into real physical memory and updates the page tables to reflect the new location of the virtual address and lastly tells the dynamic address translation mechanism to begin the search again. typically all of the real physical memory is already in use and the paging supervisor have to first save an area of real physical memory to disk and update the page table to say that the connected virtual addresses are no longer in real physical memory but saved on disk. Paging supervisors usually save and overwrite areas of real physical memory which have been least recently used, because these are probably the areas which are used least frequently. So each time the dynamic address translation hardware matches a virtual address with a real physical memory address, it has to put a time-stamp in the page table entry for that virtual address.