Exploring 'iotop' for Monitoring I/O Usage (with examples)
The iotop command provides a user-friendly way to monitor the Input/Output (I/O) usage of different processes and threads in real-time on a Linux system. Similar in concept to the popular top command, which displays general resource usage information, iotop specifically focuses on I/O activities. Understanding which processes are consuming I/O resources can be crucial for diagnosing performance bottlenecks, managing resource allocation, and ensuring efficient operation of applications.
Start top-like I/O monitor
Code:
sudo iotop
Motivation:
Watching in real-time which processes are the most I/O intensive on a Linux system can be essential for system administrators and performance analysts. The default iotop command provides a dynamic, top-like interface that continuously updates to show the I/O activity, allowing users to quickly spot I/O-heavy processes that could be affecting system performance.
Explanation:
sudo: Elevates privileges to allow monitoring system processes that require administrative access.iotop: Executes the program to display I/O usage interactively akin totop.
Example Output:
Total DISK READ : 0.00 B/s | Total DISK WRITE : 2.18 M/s
TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
4567 be/4 root 0.00 B/s 2.18 M/s 0.00 % 1.24 % dd if=/dev/zero of=/tmp/output.img bs=1M count=1024
Show only processes or threads actually doing I/O
Code:
sudo iotop --only
Motivation:
Sometimes, you may not need to monitor all processes but rather focus solely on those that are actively performing I/O operations at a given moment. This option allows for a cleaner and more focused view, filtering out idle processes to reduce clutter on the display.
Explanation:
--only: This argument limits the results to processes and threads that are currently engaged in I/O activity effectively.
Example Output:
Total DISK READ : 0.00 B/s | Total DISK WRITE : 512.00 K/s
TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
1024 be/4 root 0.00 B/s 512.00 K/s 0.00 % 0.74 % rsync
Show I/O usage in non-interactive mode
Code:
sudo iotop --batch
Motivation:
In scenarios where you want to log I/O usage data without interacting with the terminal, perhaps as part of a larger monitoring script, the batch mode is ideal. It outputs I/O usage either once or continuously without the use of cursor movements or display updates to the terminal.
Explanation:
--batch: Enables a non-interactive mode useful for logging or further processing, laying out I/O data sequentially on the terminal.
Example Output:
07:15:32 Total DISK READ : 0.00 B/s | Total DISK WRITE : 65.00 K/s
TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
3221 be/4 user1 0.00 B/s 65.00 K/s 0.00 % 0.92 % cp somefile /backup
Show only I/O usage of processes (not threads)
Code:
sudo iotop --processes
Motivation:
For users interested only in process-level I/O activity rather than detailed thread-level data, this option aggregates the data into processes, helping to simplify the output.
Explanation:
--processes: Filters results to display only processes, omitting individual thread information to provide a more concise overview.
Example Output:
Total DISK READ : 0.00 B/s | Total DISK WRITE : 4.56 M/s
PID PRIO USER DISK READ DISK WRITE COMMAND
2316 be/4 admin 0.00 B/s 4.56 M/s mysqld
Show I/O usage of given PID(s)
Code:
sudo iotop --pid=1234
Motivation:
If you need to investigate the I/O behavior of a specific process of interest, for example, one that you’ve identified through ps or another monitoring tool, specifying a PID allows for focused monitoring.
Explanation:
--pid=PID: This argument restricts output to a particular process, based on its Process ID (PID), enabling targeted inspection.
Example Output:
Total DISK READ : 0.00 B/s | Total DISK WRITE : 3.12 M/s
TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
1234 be/4 service 0.00 B/s 3.12 M/s 0.00 % 2.45 % java someApp
Show I/O usage of a given user
Code:
sudo iotop --user=user1
Motivation:
In multi-user systems, it may be necessary to monitor the I/O impact of processes initiated by a specific user, either for troubleshooting or auditing purposes. This command focuses exclusively on the I/O usage of particular user-initiated processes.
Explanation:
--user=user: Limits the display to show only the processes belonging to the specified user, providing a user-centric view of I/O consumption.
Example Output:
Total DISK READ : 0.00 B/s | Total DISK WRITE : 10.00 K/s
TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
4356 be/4 user1 0.00 B/s 10.00 K/s 0.00 % 0.67 % vim script.sh
Show accumulated I/O instead of bandwidth
Code:
sudo iotop --accumulated
Motivation:
There are times when you might want to know the total amount of data read or written by processes over time rather than just their current rate. This perspective can help identify long-running processes contributing to significant I/O loads.
Explanation:
--accumulated: Outputs total data read and written by each process sinceiotopstarted, rather than per-second bandwidth figures, offering cumulative insights.
Example Output:
Total DISK READ : 512.00 K | Total DISK WRITE : 10.00 M
TID PRIO USER DISK READ DISK WRITE COMMAND
8921 be/4 daemon 512.00 K 10.00 M apache2 -k start
Conclusion:
The iotop command is a powerful tool for monitoring I/O utilization within Linux systems. It provides significant flexibility, allowing users to examine I/O data in real-time, filter specific processes, aggregate data for particular users, and accumulate overarching I/O usage statistics. Understanding how to leverage these options can greatly enhance system administration and performance tracking tasks.
