mpstat

Guri Bee

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17-10-2024

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Demystifying mpstat: A Deep Dive into Linux System Performance

mpstat is a powerful command-line utility in Linux that provides real-time statistics about your system's CPU, memory, and I/O activity. This tool is invaluable for system administrators and developers looking to diagnose performance bottlenecks, understand resource utilization, and optimize system performance.

In this article, we'll explore the core features of mpstat, break down its output, and demonstrate how to use it effectively. We'll also delve into some common scenarios where mpstat proves indispensable.

What does mpstat tell you?

mpstat reveals crucial metrics about your system's activity, including:

• CPU Usage: mpstat provides detailed insights into the CPU's workload, showing the percentage of time spent in various states:
  • User: Time spent executing user-level processes.
  • Nice: Time spent executing low-priority processes.
  • System: Time spent executing kernel-level tasks.
  • Idle: Time the CPU is idle, not executing any processes.
  • IOWait: Time the CPU spends waiting for I/O operations to complete.
  • IRQ: Time spent servicing hardware interrupts.
  • SoftIRQ: Time spent servicing software interrupts.
  • Steal: Time spent waiting for another virtual machine to release the CPU.
• Memory Usage: mpstat provides information about the system's memory pressure, showing the percentage of swap used and the rate of page-ins and page-outs.
• I/O Activity: mpstat reports on the rate of disk reads and writes, providing insights into the workload on your storage devices.

How to use mpstat effectively

Let's dive into some practical examples of mpstat in action.

1. Monitoring CPU Usage

To get a snapshot of your CPU usage, run the following command:

mpstat

This will display the current CPU statistics for all cores. You can then analyze the output to see which states are dominating the CPU time.

Example Output:

Linux 5.10.0-10-amd64 (DESKTOP-H665E5R) 	08/28/2023  _x86_64_        (12 CPUs)

11:57:58     CPU    %usr   %nice    %sys  %iowait    %irq  %soft  %steal   %guest  %gnice   %idle
11:57:58      0   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      1   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      2   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      3   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      4   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      5   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      6   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      7   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      8   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58      9   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58     10   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99
11:57:58     11   10.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00   89.99

2. Monitoring CPU Usage Over Time

To track CPU usage over a period of time, use the -T option with a time interval:

mpstat -T 5 

This will display CPU statistics every 5 seconds. The output will help you identify trends and spikes in resource utilization.

3. Monitoring Specific CPU Cores

To focus on a particular CPU core, use the -P option followed by the core number:

mpstat -P ALL

This will show statistics for all CPU cores. You can also specify individual core numbers.

4. Monitoring I/O Activity

To monitor I/O activity, use the -I option:

mpstat -I -T 1

This command will display I/O statistics for all devices every second.

5. Monitoring Memory Usage

While mpstat primarily focuses on CPU and I/O, you can also obtain some memory-related information. Use the -m option:

mpstat -m

This command will display the percentage of swap used and the rate of page-ins and page-outs.

Understanding the output

mpstat provides detailed information in a tabular format. The key columns to interpret are:

• %usr: The percentage of time spent on user-level tasks.
• %sys: The percentage of time spent on kernel-level tasks.
• %iowait: The percentage of time the CPU spent waiting for I/O operations.
• %idle: The percentage of time the CPU was idle.

Analyzing Performance Bottlenecks

Analyzing mpstat output helps identify performance bottlenecks:

• High %usr: Suggests CPU-bound processes are consuming significant resources.
• High %sys: Indicates the kernel is heavily engaged in tasks, potentially due to excessive interrupts or system calls.
• High %iowait: Points towards a potential I/O bottleneck, where the CPU is waiting for data from disks.
• Low %idle: Indicates the CPU is under significant load.

Beyond mpstat

While mpstat provides a comprehensive overview of system performance, remember that it's only one piece of the puzzle. Combining mpstat with other monitoring tools like top, iostat, and vmstat can give you a more holistic picture.

Conclusion

mpstat is an invaluable tool for system administrators and developers to monitor and analyze system performance. By understanding its output and applying the knowledge gained, you can diagnose performance bottlenecks, optimize resource utilization, and ensure your system runs smoothly and efficiently.

Note: The examples and output snippets provided in this article are illustrative. Specific output will vary depending on your system configuration and workload.

Attribution:

• This article draws inspiration from the official mpstat documentation and discussions on various platforms like Stack Overflow and the Linux kernel mailing list.