What is a Swapping Technique in Operating System (OS)?

 

Swapping in OS:

 

Swapping is a method to improve the main memory utilization. For ex: the main memory consists of 10 processes. Assume that it is the maximum capacity, and the CPU is currently executing the process number 9. In the middle of the execution, the process number 9 needs an IO. Then, the CPU switch to another job and process number 9 is moved to a disc and another process is loaded in main memory in the place of process number 9. When the process number 9 completes its IO operation, then the process number 9 is moved into main memory from disc. Switching a process from main memory to disk is said to be “swap out” and switching a process from disk to main memory is said to be “swap in”. This type of mechanism is said to be “swapping”. We can achieve efficient memory utilization with swapping.

 

Consider the following figure:

Swapping requires a ‘Backing Store’. The backing store is commonly a fast disk. It must be large enough to accommodate the copies of all process images for all users. When a process is swapped out, its executable image is copied into backing store. When it is swapped in, it is copied into the new block allocated by the Memory Manager.