How to Use MySQLTuner to Test Database Performance on a Linux Machine

How to Use MySQLTuner to Test Database Performance

Databases are the backbone of many modern applications, and their performance can significantly impact the user experience. One of the most popular database management systems is MySQL. To ensure that a MySQL database runs efficiently, it’s crucial to regularly assess its performance. One of the best tools for this purpose is MySQLTuner.

MySQLTuner is a Perl script that assists you in optimizing your MySQL settings. It reviews the database server’s performance and provides recommendations to increase its stability and performance. This guide will walk you through the process of using MySQLTuner on a Linux machine to assess the efficiency of database operations and evaluate query performance and latency.

Let’s get started.

Step 1. Installing MySQLTuner

MySQLTuner is not included in the default repositories of most Linux distributions. However, you can easily download and run it as a Perl script.

chmod +x

Step 2. Running MySQLTuner

To run MySQLTuner, simply execute the script:


You might be prompted to enter the MySQL root password. After providing the password, MySQLTuner will start analyzing your database server.

For example:

>>  MySQLTuner 1.7.19 - Major Hayden 
>>  Bug reports, feature requests, and downloads at
>>  Run with '--help' for additional options and output filtering

[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.7.31
[OK] Operating on 64-bit architecture

-------- Log file Recommendations ------------------------------------------------------------------
[--] Log file: /var/log/mysql/error.log(0B)
[OK] Log file /var/log/mysql/error.log exists
[OK] Log file /var/log/mysql/error.log is readable.

-------- Storage Engine Statistics -----------------------------------------------------------------
[--] Data in InnoDB tables: 1G (Tables: 1234)
[--] Data in MyISAM tables: 123M (Tables: 56)
[--] Data in MEMORY tables: 3M (Tables: 12)
[!!] Total fragmented tables: 23

-------- Security Recommendations ------------------------------------------------------------------
[!!] User '@localhost' has no password set.
[!!] There are anonymous accounts for localhost.

-------- Performance Metrics -----------------------------------------------------------------------
[--] Up for: 3d 12h 34m 56s (12M q [34.567 qps], 456K conn, TX: 123B, RX: 45B)
[--] Reads / Writes: 80% / 20%
[--] Binary logging is disabled
[--] Physical Memory     : 15.7G
[--] Max MySQL memory    : 6.8G
[--] Other process memory: 500M
[OK] Maximum reached memory usage: 4.2G (26.78% of installed RAM)
[OK] Maximum possible memory usage: 6.8G (43.31% of installed RAM)
[OK] Overall possible memory usage with other process is compatible with memory available
[!!] Slow queries: 23% (2M/12M)
[OK] Highest usage of available connections: 80% (202/250)
[OK] Aborted connections: 0.34%  (1567/456789)
[!!] Query cache is disabled
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 2M sorts)
[!!] Joins performed without indexes: 45678
[OK] Temporary tables created on disk: 24% (1M on disk / 5M total)
[OK] Thread cache hit rate: 99% (202 created / 456K connections)
[!!] Table cache hit rate: 5% (1K open / 23K opened)

-------- Recommendations ---------------------------------------------------------------------------
General recommendations:
    Set a password for user '@localhost'
    Remove anonymous accounts for localhost
    Enable the slow query log to troubleshoot bad queries
    Add skip-name-resolve to MySQL configuration to disable DNS lookups
    Adjust your join queries to always utilize indexes
    Increase table_open_cache gradually to avoid file descriptor limits

Variables to adjust:
    query_cache_size (>= 8M)
    join_buffer_size (> 128.0M, or always use indexes with joins)
    table_open_cache (> 2000)

Step 3. Understanding the Report

MySQLTuner will provide a detailed report, including:

  • General statistics about the server.
  • Storage engine statistics.
  • Performance metrics.
  • Recommendations to optimize the server.

In our example:

Performance Metrics:

  • The server has processed 12 million queries since its last restart, averaging 34.567 queries per second.
  • 80% of the operations are read operations, and 20% are write operations.
  • The server has 15.7GB of physical memory, with MySQL potentially using up to 6.8GB.
  • Slow queries account for 23% of all queries, which is concerning. Slow queries can significantly impact performance.
  • The server has a maximum of 250 connections, with the highest usage reaching 202 connections (80%).
  • The query cache, which can improve performance by storing the results of frequently used queries, is disabled.
  • Some joins are being performed without indexes, which can slow down query performance.
  • The table cache hit rate is low at 5%, indicating that the server frequently has to open new tables. This can be a performance bottleneck.


  • Security: Set a password for the user ‘@localhost’ and remove anonymous accounts to enhance security.
  • Performance: Enable the slow query log to identify and optimize slow-performing queries. Consider disabling DNS lookups by adding skip-name-resolve to the MySQL configuration. Adjust join queries to use indexes, which can significantly speed up performance.
  • Configuration Adjustments: Increase the query_cache_size to at least 8M to enable and optimize the query cache. Increase the join_buffer_size or ensure joins always use indexes. Gradually increase the table_open_cache to improve the table cache hit rate.

Interpretation Summary:

The MySQL server in this sample output has some areas that need attention:

  1. Security Concerns: The lack of a password for a user and the presence of anonymous accounts are significant security risks that should be addressed immediately.
  2. Performance Issues: The high percentage of slow queries and joins without indexes are concerning. These can lead to noticeable performance degradation and should be optimized.
  3. Configuration Tweaks: Several configuration adjustments are recommended, such as enabling the query cache and increasing buffer sizes. These changes can help improve the server’s overall performance.

Step 4. Applying Recommendations

Based on the report, you can adjust the MySQL configuration file, typically located at /etc/my.cnf or /etc/mysql/my.cnf.

It’s essential to understand that not all recommendations should be applied blindly. Some might not be suitable for your specific use case. Always backup your configuration before making any changes.

After making changes, always restart the MySQL service for the new settings to take effect.

sudo service mysql restart

Step 5. Regularly Monitor Your Database

It’s a good practice to run MySQLTuner periodically, especially after significant changes to your database or application. This ensures that your database remains optimized as your data grows and usage patterns change.

Commands Mentioned

  • wget – Used to download files from the internet.
  • chmod – Changes the permissions of a file.
  • ./ – Executes the MySQLTuner script.
  • sudo service mysql restart – Restarts the MySQL service.
  1. How often should I run MySQLTuner?

    It’s recommended to run MySQLTuner periodically, especially after significant changes to your database or application. This ensures that your database remains optimized as your data grows and usage patterns change.

  2. Is MySQLTuner suitable for all MySQL versions?

    MySQLTuner supports a wide range of MySQL versions, but it’s always a good idea to check the tool’s official documentation or website for compatibility with your specific MySQL version.

  3. Do I need to restart MySQL after applying changes?

    Yes, after making changes to the MySQL configuration based on MySQLTuner’s recommendations, you should restart the MySQL service for the new settings to take effect.

  4. Can MySQLTuner make changes to my configuration automatically?

    No, MySQLTuner only provides recommendations. It’s up to the administrator to review and apply these recommendations manually, ensuring they are suitable for the specific use case.

  5. Is it safe to apply all recommendations from MySQLTuner?

    Not necessarily. While MySQLTuner provides valuable insights, not all recommendations may be suitable for every scenario. It’s essential to understand each recommendation and its implications before applying changes. Always backup your configuration before making any adjustments.


Optimizing your MySQL database is crucial for ensuring smooth and efficient operations, especially as your application grows and evolves. MySQLTuner is an excellent tool that aids in this optimization process by providing insightful recommendations based on the current state of your database. However, it’s essential to approach these recommendations with caution. Not every suggestion will be suitable for your specific use case or environment.

When using MySQLTuner:

  • Always backup your configuration before making any changes. This ensures that you can quickly revert to a previous state if something goes wrong.
  • Understand the implications of each recommendation. While the tool provides valuable insights, blindly applying all suggestions can lead to unforeseen issues.
  • Regularly monitor your database’s performance. As your application grows and user behavior changes, the database’s needs might also evolve. Regular checks ensure that the database remains optimized for the current scenario.
  • Consider other performance-enhancing techniques and tools in conjunction with MySQLTuner. While it’s a powerful tool, it’s just one of many that can help you maintain a high-performing database.

In web hosting and server management, understanding the intricacies of your database is just one piece of the puzzle. Familiarizing yourself with different hosting options, such as dedicated servers, VPS servers, cloud hosting, and shared hosting, can further enhance your website’s performance. Additionally, understanding the nuances of various web servers like Apache, Nginx, and LiteSpeed can provide a more holistic approach to optimization.

In conclusion, while tools like MySQLTuner are invaluable for database optimization, a comprehensive understanding of all components of your web infrastructure is crucial for achieving the best performance. Regular monitoring, continuous learning, and a proactive approach to optimization will ensure that your applications run smoothly, efficiently, and remain responsive


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