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Swapping in Operating System

      ⇰  SWAPPING :-
As we know a process must be in memory to be executed. A computer has sufficient amount of physical memory but most of times we need more memory so we swap some memory on baking store or harddisk. A process can be swapped temporarily out of memory to a backing store and then brought back into memory for continued execution. Swapping makes it possible for the total physical address space of all processes to exceed the real physical memory of the system, thus increasing the degree of multiprogramming in a system.

Thus swapping is a mechanism in which a process can be swapped temporarily out of main memory to secondary storage or harddisk and make that memory available to other processes. At some later time, the system swaps back the process from the secondary storage to main memory. Sometimes performance is usually affected by swapping process but it helps in running multiple and big processes in parallel and that's the reason Swapping is also known as a technique for memory compaction.

 Swap space is a space on hard disk which is a substitute of physical memory. It is used as virtual memory which contains process memory image. Whenever our computer run short of physical memory it uses it’s virtual memory and stores information in memory on disk. Swap space helps the computer’s operating system in pretending that it have more RAM memory than it actually has. It is also called as swap file.This interchange of data between virtual memory and real memory is called as swapping and space on disk as “swap space”.

The total time taken by swapping process includes the time it takes to move the entire process to a secondary disk and then to copy the process back to memory, as well as the time the process takes to regain main memory.

Operating Systems: Main Memory


SWAP-IN :- Moving data from Swap space to main memory of the machine.
SWAP-OUT :- Moving data from main memory to backing store or harddisk when main memory space fills up.

    
⇰ BENIFITS OF SWAPPING :- 
 i > It offers a higher degree of multiprogramming. 
 ii > Allows dynamic relocation.
iii > It helps to get better utilization of memory.
iv > Minimum wastage of CPU time on completion so it can easily be applied to a        priority-based scheduling method to improve its performance.




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