Memory Management – Page Fault & Page Replacement

A page fault occurs when a process tries to use a page that is not in memory, causing an operating system interrupt.

A page fault occurs when a page that is needed is not loaded in memory.

The page table is checked for the memory reference.

A page fault trap occurs, which is an operating system interrupt.

The OS locates the page on auxiliary storage (disk) and loads it into a free memory frame.

The OS resets the page table to mark the page as valid and restarts the instruction that caused the page fault.

Page replacement occurs when there are no free frames available to load a missing page.

To find a frame to free in order to reduce page faults.

A victim page is selected, its contents are copied to disk if modified, the page table is updated to mark it invalid, and the frame is then available.

The algorithm is chosen to have the lowest page fault rate.

FIFO (First In First Out), Optimal, Least Recently Used (LRU), Random, Second Chance.

FIFO replaces the oldest page in memory based on the age of pages.

15 page faults.

It is when increasing the number of memory frames causes an increase in page faults, observed in some algorithms like FIFO.

The Optimal page replacement algorithm.

It replaces the page that will not be used for the longest period in the future.

It requires knowledge of future memory references, which is generally not available.

LRU replaces the page that has not been used for the longest period, based on past usage history.

Hardware assistance to track and order frames by their last used time.

It selects any page at random to replace.

A variation of FIFO where pages with a set reference bit are given a second chance and moved to the end of the queue before replacement.

Thrashing occurs when high page replacement activity causes processes to spend more time paging than executing, reducing CPU utilization and system throughput.