Swapping in Operating System - GeeksforGeeks (2024)

To increase CPU utilization in multiprogramming, a memory management scheme known as swapping can be used. Swapping is the process of bringing a process into memory and then temporarily copying it to the disc after it has run for a while. The purpose of swapping in an operating system is to access data on a hard disc and move it to RAM so that application programs can use it.

What is Swapping in the Operating System?

Swapping in an operating system is a process that moves data or programs between the computer’s main memory (RAM) and a secondary storage (usually a hard disk or SSD). This helps manage the limited space in RAM and allows the system to run more programs than it could otherwise handle simultaneously.

It’s important to remember that swapping is only used when data isn’t available in RAM. Although the swapping process degrades system performance, it allows larger and multiple processes to run concurrently. Because of this, swapping is also known as memory compaction. The CPU scheduler determines which processes are swapped in and which are swapped out. Consider a multiprogramming environment that employs a priority-based scheduling algorithm. When a high-priority process enters the input queue, a low-priority process is swapped out so the high-priority process can be loaded and executed. When this process terminates, the low-priority process is swapped back into memory to continue its execution. The below figure shows the swapping process in the operating system:

Swapping has been subdivided into two concepts: swap-in and swap-out.

• Swap-out is a technique for moving a process from RAM to the hard disc.
• Swap-in is a method of transferring a program from a hard disc to main memory, or RAM.

Process of Swapping

• When the RAM is full and a new program needs to run, the operating system selects a program or data that is currently in RAM but not actively being used.
• The selected data is moved to the secondary storage, making space in RAM for the new program.
• When the swapped-out program is needed again, it can be swapped back into RAM, replacing another inactive program or data if necessary.

Real Life Example of Swapping

Imagine you have a disk (RAM) that is too small to hold all your books and papers (programs). You keep the most important items on the desk and store the rest in a cabinet (secondary storage). When you need something from the cabinet, you swap it with something on your desk. This way, you can work with more items than your desk alone could hold.

Advantages

• If there is low main memory so some processes may has to wait for much long but by using swapping process do not have to wait long for execution on CPU.
• It utilize the main memory.
• Using only single main memory, multiple process can be run by CPU using swap partition.
• The concept of virtual memory start from here and it utilize it in better way.
• This concept can be useful in priority based scheduling to optimize the swapping process.

Disadvantages

• If there is low main memory resource and user is executing too many processes and suddenly the power of system goes off there might be a scenario where data get erase of the processes which are took parts in swapping.
• Chances of number of page faults occur
• Low processing performance

Only one process occupies the user program area of memory in a single tasking operating system and remains in memory until the process is completed.
When all of the active processes in a multitasking operating system cannot coordinate in main memory, a process is swapped out of main memory so that other processes can enter it.

For more information, you can refer Difference between Paging and Swapping in OS, and the Difference between Swapping and Context Switching.

Conclusion

Swapping in an operating system is a technique that moves data between RAM and secondary storage to manage limited memory efficiently. It allows the system to run more programs simultaneously by temporarily moving inactive data out of RAM. This process helps improve system performance and ensures that the available memory is used effectively.

Frequently Asked Questions on Swapping – FAQs

Why is swapping used in operating systems?

Swapping is used to manage limited RAM effectively, allowing the system to run more programs simultaneously and improving overall system performance.

How does swapping work?

When RAM is full, the operating system selects inactive data or programs and moves them to secondary storage. This frees up RAM for new or active programs. When the swapped-out data is needed again, it is moved back to RAM.

What is “swapping in” and “swapping out”?

“Swapping in” refers to the process of moving data from secondary storage back into RAM, while “swapping out” refers to moving data from RAM to secondary storage.