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Page faults
Page Faults A page fault is when a process tries to access memory that is outside of its accessible physical memory (the memory that the process is curre...
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Page Faults A page fault is when a process tries to access memory that is outside of its accessible physical memory (the memory that the process is curre...
A page fault is when a process tries to access memory that is outside of its accessible physical memory (the memory that the process is currently using). This can happen for several reasons:
Programmed I/O operations: Some I/O operations can temporarily require memory outside of the process's address space.
Virtual memory allocation: A program may request memory that is not available in physical memory, but is present in a virtual memory space that the process is using.
Execution of a procedure: Certain procedures, like system calls, may require memory outside of the process's address space.
Memory corruption: In some cases, memory can become corrupted, causing the process to access invalid memory locations.
When a page fault occurs, the operating system intervenes to find a free page in physical memory to satisfy the memory request. This can be done by:
Swapping out a page from secondary storage (hard disk) to a free page in physical memory.
Loading a page from secondary storage into a free page in physical memory.
Combining multiple pages into one page.
This process is called page replacement. The page that was swapped out is moved to secondary storage, and the free page is loaded into the memory that the process is currently using.
Page faults can be a significant performance bottleneck, as they can slow down program execution significantly. The operating system tries to prevent page faults as much as possible by using memory protection techniques and optimizing memory allocation