Monitoring I/O Usage with iotop (with examples)
Monitoring I/O usage is essential for maintaining system performance and identifying resource-intensive processes. iotop is a powerful command-line tool that provides real-time insights into I/O usage by processes or threads in a Linux system. In this article, we will explore eight different use cases of the iotop command, along with code examples, motivations, arguments, and example outputs for each use case.
Start top-like I/O monitor
To start a top-like I/O monitor using iotop, you can use the following command:
sudo iotop
Motivation: By starting an I/O monitor, you can observe the current I/O usage by processes or threads in real-time. This is useful for identifying any processes causing high I/O activity and potentially affecting overall system performance.
Output: The command will continuously display a table showing the processes or threads sorted by their current I/O usage. You will see columns such as PID, USER, DISK READ, DISK WRITE, and SWAPIN.
Show only processes or threads actually doing I/O
To show only the processes or threads actually performing I/O, you can use the following command:
sudo iotop --only
Motivation: Filtering the output to display only the processes or threads actively engaged in I/O can help focus on the most resource-intensive activities. This allows for easier identification of processes that are actively utilizing the disk.
Output: The output will show only the processes or threads that are actively performing I/O operations.
Show I/O usage in non-interactive mode
To view I/O usage in non-interactive mode, you can use the following command:
sudo iotop --batch
Motivation: In certain scenarios, it may be necessary to fetch I/O usage data programmatically or store it for further analysis. Non-interactive mode allows the iotop output to be easily parsed and integrated into scripts or monitoring systems.
Output: The command will display the I/O usage information once and then exit, making it suitable for capturing I/O data programmatically.
Show only I/O usage of processes
By default, iotop displays I/O usage for both processes and threads. To show only the I/O usage of processes, you can use the following command:
sudo iotop --processes
Motivation: Focusing solely on the I/O usage of processes can be helpful when troubleshooting issues related to a particular process or when monitoring a specific set of processes for performance tuning.
Output: The output will show only the I/O usage of processes, excluding the information about threads.
Show I/O usage of given PID(s)
To display the I/O usage of specific process IDs (PIDs), you can use the following command:
sudo iotop --pid=PID
Motivation: Monitoring the I/O usage of specific processes can be beneficial when troubleshooting a particular application or process that is heavily utilizing disk I/O resources.
Arguments:
PID: Replace this with the process ID(s) (numeric value) of the process(es) you want to monitor. You can specify multiple PIDs separated by commas.
Output: The output will present the I/O usage information limited to the specified process IDs.
Show I/O usage of a given user
To view the I/O usage of processes belonging to a specific user, you can use the following command:
sudo iotop --user=user
Motivation: Monitoring the I/O usage of a particular user can help identify resource-heavy processes initiated by that user. This information can be useful for examining the impact of specific user activities on disk I/O.
Arguments:
user: Replace this with the username of the user whose I/O usage you want to monitor.
Output: The output will display the I/O usage only for processes initiated by the specified user.
Show accumulated I/O instead of bandwidth
By default, iotop displays I/O bandwidth usage in kilobits per second. If you want to see accumulated I/O instead, you can use the following command:
sudo iotop --accumulated
Motivation: When analyzing I/O patterns, it’s sometimes more meaningful to examine the total amount of I/O performed rather than the bandwidth per second. This can be particularly useful for long-running processes or when comparing different processes based on their total I/O volume.
Output: The command will display the accumulated I/O, represented in kilobytes, for each process or thread.
Conclusion
iotop is a versatile tool for monitoring I/O usage in Linux systems. Each of the eight use cases explored in this article demonstrates different scenarios where iotop can provide valuable insights into I/O activity. Whether you need to monitor resource-intensive processes, analyze I/O patterns, or troubleshoot performance issues, iotop is a powerful command-line utility that can help you in these endeavors.
Remember, always run iotop with administrative privileges (sudo) to ensure proper access to I/O usage information.
