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CompTIA Linux+ XK0-005 - 4.3 - Swapping

In Linux environments, efficient memory management is crucial for optimal system performance. When the available physical memory is insufficient to meet the demands of running processes, the operating system utilizes a technique called swapping to move inactive memory pages to disk. This guide explores the concept of swapping, its implications on system performance, common causes of high swap usage, and how to check for swap usage.

What is Swapping?

Swapping is a memory management technique employed by the Linux kernel to cope with memory pressure. When the system is low on physical memory, inactive memory pages that are not actively used by processes are temporarily moved to a designated area on the disk called the swap space. This frees up physical memory to accommodate more active processes.

Common Causes of High Swap Usage

Several factors can contribute to high swap usage in a Linux system:

  • Insufficient physical memory: When the system lacks sufficient physical memory to accommodate the memory demands of running processes, swapping becomes necessary.
  • Memory leaks: Programming errors or poorly designed applications may result in memory leaks, where memory is allocated but not properly released. Over time, this can lead to excessive memory consumption and increased swap usage.
  • Overcommitment of memory: If the system allows aggressive memory overcommitment, processes may allocate more memory than is actually available. In such cases, swapping may be triggered to compensate for the shortage.

How to Check for Swap Usage

You can use various commands and tools to check the swap usage on a Linux system. Here are a few examples:

  • free command: The free command displays information about system memory, including swap utilization. Running the following command provides an overview of swap usage:

    free -h

    The output includes the total swap space, used swap space, and available swap space.

  • swapon command: The swapon command displays the active swap areas and their utilization. Executing the following command provides details about active swap devices:

    swapon --show

    The output shows the swap device, type, size, used space, and priority.


Swapping is a vital mechanism in Linux for managing memory when physical memory becomes limited. By understanding swapping, its causes, and how to monitor swap usage, you can effectively analyze and troubleshoot CPU and memory issues related to high swap utilization. Regularly monitoring swap usage helps identify potential performance bottlenecks and optimize system resources for optimal performance.

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