What is Memory Swapping? How Memory Swapping Works

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Memory swapping is a popular technology that helps improve the performance of the operating system. With this process, the system can efficiently switch between physical memory and virtual memory as per requirements. 

As physical memory (RAM) is primarily used for operational processes, it is not always sufficient to handle all the load all the time. At times, it gets exhausted and thus demands additional memory to run applications and processes. 

Memory swapping can help as this technique creates a larger virtual address space by combining the physical memory and hard disk space. Unused memory contents are swapped to the disk space, which can be restored later. As a result, the physical memory becomes free and can run other operations. 

Let’s get into detail about the memory swapping technique, how it helps improve performance, its advantages, limitations, and other vital aspects.

Learn more about RAM

How Memory Swapping Works & Improves Performance

Memory swapping means the exchange of memory. The primary goal of this process is to improve the utilization of the main memory

In an operating system, processes run based on priority-based preemptive scheduling. When a higher-priority task needs to be performed, space must be available in the main memory for the execution. Therefore, the system uses virtual memory and storage space as additional resources. It helps in faster execution of the process and efficient data analysis.

The storage disk space acts as a functional equivalent of the memory storage execution space. This storage device space is called the “swap space.” The processes that are swapped out of the physical RAM are run in this swap space. 

By default the operating system or a virtual machine hypervisor manages the memory-swapping process. However, the user has the option to disable this capability if required. 

When the physical RAM is used up completely — and additional processes and applications need space to run — the process of memory swapping gets initiated. The operating system manages this automatically and forms a virtual memory capacity (non-physical RAM) by mapping the physical memory space to the swap space. 

The primary goal behind this entire process is to enable more usable memory than the computer hardware actually holds. Users can extend the memory to the storage disk space. This results in an efficient memory management system while ensuring stability. 

What is Swap Space or Swap File? 

Physical memory on a computer is adequate, but most of the time, we need more space. So we swap some memory on the disk. A hard drive’s swap space serves as a replacement for physical memory. It holds images from process memory and serves as virtual memory. 

When the computer’s physical memory runs out, it utilizes virtual memory to store data on a disk. The computer’s operating system uses swap space to make the device appear to have more memory than it does.

Swapping is the process of exchanging data between virtual and physical memory, and “swap space” refers to the disk space used for this. Running processes can use virtual memory, which is a combination of RAM and disk space. When RAM is at capacity, swap space — a piece of virtual memory stored on the hard drive gets consumed.

When the system’s memory is low, a system file called a swap file will generate temporary storage space on a solid-state drive or hard disk. This file will free up memory for other running programs by swapping a portion of RAM from inactive applications.

Users can adjust the default amount of swap space provided by operating systems like Windows, Linux, and others according to their demands. Virtual memory can be simply turned off entirely if the user doesn’t want to use it. 

But if they do and run out of memory, the kernel will kill some of the running processes to free up enough physical memory. Deciding to use swap space is entirely up to the user.

Read more: Memory vs Storage: What Are the Differences?

Advantages of Memory Swapping 

Memory swapping has several benefits, including optimizing your system, enhancing its multi-tasking abilities and prioritizing processes for continuous operation. Here are some of the advantages of memory swapping: 

  • Maximum Memory utilization: Swapping frees up memory and enables the seamless operation of more applications. Swap files guarantee that each program has its own dedicated memory, which enhances overall performance.
  • Continuous Operations: Priority-based process scheduling might use the swapping method, which involves replacing a low-priority activity with a high-priority process that minimizes operations disruption.
  • System Optimization: With swapping, the CPU can perform many tasks simultaneously, reducing the time programs must wait to run. As a result, it is easier for the CPU to control numerous processes in a single main memory.
  • Enhanced multi-tasking: Memory swapping also helps boost the level of multiprogramming by enabling more programs to run concurrently and effectively use RAM.

Limitations of Memory Swapping

Memory swapping also has some disadvantages, including performance lag, capacity limitations, and loss of information. Here are some of the potential cons of memory swapping:  

  • Performance: When triggered by memory swapping, disk storage space cannot offer the same performance as actual RAM used for process execution.
  • Disk Limitations: Storage media’s reliability and accessibility help swap files, which may not be as reliable as system memory.
  • Capacity: The operating system’s or hypervisor’s allocated swap space limits how much memory can be swapped.
  • Information loss: If the computer system loses power during intensive swapping, the user could lose all program-related information.
  • Increase page fault: If the swapping technique is subpar, the composite method may result in more page faults and reduce processing speed. 

How Does Memory Swapping Improve Performance?

The primary goal of memory management swapping is to make more memory accessible than the computer hardware supports. Physical memory may occasionally be allotted while a process still needs more memory. 

Memory swapping allows the operating system and its users to expand memory to disk rather than limiting the system to solely physically RAM-based memory.

The operating system or hypervisor oversees the memory-swapping process. Swap is often turned on by default, although users can opt to turn it off. The operating system automatically controls the actual memory-swapping procedure and the construction of the swap file. 

It starts when necessary because processes and apps eat up physical RAM and need more space. The state of physical memory pages is translated into swap space as additional RAM is needed, implementing a virtual (as opposed to physical RAM) memory capacity.

Memory Swapping Examples

Swapping is the interchange of processes. Moreover, priority-based preemptive scheduling is used in process interchange. This means that when a process with a higher priority enters the system, the memory management temporarily switches the lowest priority process to disk and executes the process with the highest priority in the main memory. 

The lower priority process is switched back to memory and continues to operate after the highest priority process finishes. This technique is known as roll in/roll out.

If address binding occurs during the load time, processes paged out of the main memory will occupy the same address space when paged back into the main memory. If it had run-time binding, the address would be determined in real time, allowing the process to utilize any address space in the main memory.

Several holes in the memory are made when the process is switched in and out. In order to handle these holes, a large memory space is created by combining holes. Moving every procedure as far downward as possible does this. This process is known as compaction and is rarely applied as it takes higher CPU time. 

For instance, if there is 40+20+20K of vacant space, this space is available, but it’s not all together. So, swapping will create 80K of space by compaction.

What’s the Difference Between Swapping and Paging?

Swapping is the process of temporarily moving a process from the main memory to the secondary memory, which is faster than the secondary memory. However, because RAM has a limited capacity, dormant processes are moved to secondary memory. 

Paging, on the other hand, is a memory allocation process in which several non-contiguous memory blocks are given fixed-size assignments. Usually, the size is 4KB. Paging always occurs between pages that are currently active. 

The following are some key distinctions between paging and swapping in the operating system:

  • The memory management technique known as paging enables systems to store and retrieve data from secondary storage for use in the main memory. Swapping, however, momentarily moves a process from primary to secondary memory.
  • Paging transfers pages, making it more adaptable than swapping. Swapping, on the other hand, offers less flexibility.
  • When swapping, many tasks are running in the main memory. Yet, when paging, some processes are running in the main memory.
  • Processes that swap between the primary memory and secondary memory are known as swapping. In contrast, pages are identical-sized memory blocks that move between the main and secondary memory during paging.
  • Swapping speeds up the CPU’s access to processes. On the other hand, virtual memory can be used with paging.
  • Swapping is ideal for heavy workloads. Paging, on the other hand, is suitable for light to medium workloads.
  • Multiprogramming is possible using swapping. The physical address space of a process can be non-contiguous with paging, which prevents external fragmentation.

Head-to-Head Comparison between Paging and Swapping

Paging and swapping have been compared side by side in several situations. Following are some distinctions between the two:

Features Paging Swapping
Definition It is a technique for managing memory that gives computers the ability to store and retrieve data from secondary storage for use in RAM. A process is momentarily moved from primary memory to secondary memory.
Basic The memory address space of a process might be non-contiguous thanks to paging. Swapping allows the operating system to run multiple programs efficiently concurrently.
Flexibility Since only the pages of a process are moved, paging is more flexible. Because swapping switches the entire process back and forth between RAM and the back store, it is less adaptable.
Main Functionality Pages are memory blocks of identical size transferred between primary and secondary memory during paging. Processes that swap go back and forth between primary and secondary memory.
Multiprogramming More processes can run in the main memory thanks to paging. Swapping permits fewer applications to execute in the main memory than paging does.
Workloads Heavy workloads are suited for swapping. For light to moderate workloads, paging is suitable.
Usage Virtual memory can be used with paging. The CPU can access processes more quickly, thanks to swapping.
Processes When swapping, many processes are running in the main memory. With paging, some programs are running in the main memory.

Bottom Line: What is Memory Swapping?

The OS’s swapping feature maintains proper memory use by temporarily moving stopped or inactive processes from main memory to secondary memory. One of its primary benefits is the swapping technique’s ability to properly utilize RAM and guarantee memory availability for all processes.

One of the key drawbacks of the swapping technique is that the system’s performance will suffer if the switching algorithm is not good enough. Swapping can be highly effective at keeping machines running smoothly if done correctly. However, if done incorrectly, it may result in sluggish performance or even system failures.

Read more about memory management.

Kashyap Vyas
Kashyap Vyas
Kashyap Vyas is a contributing writer to Enterprise Storage Forum. He covers a range of technical topics, including managed services, cloud computing, security, storage, business management, and product design and development. Kashyap holds a Master's Degree in Engineering and finds joy in traveling, exploring new cultures, and immersing himself in Indian classical and Sufi music. uns a consulting agency.

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