MySQL 8 sample config (my.cnf example) and tuning.

With the release of MySQL 8 I wanted to paste my tuned my.cnf (MySQL configuration file) for discussion, suggestions, and questions. To get the most out of your MySQL 8 installation, you will need to configure it correctly and tune the settings for your specific use case. In this blog post, we will discuss my sample MySQL 8 configuration file and some tips for tuning the settings for optimal performance.

The MySQL configuration file, also known as my.cnf, is a text file that contains configuration settings for your MySQL installation. The file is usually located in the MySQL installation directory, and it can be edited with a text editor.

With the launch of this blog’s tech forums, I’m hoping that the performance tuning tips that emerge will be from all of us who manage MySQL databases. Recommendations are continued in the comments section at the end of this article.

Screenshot from btop showing MySQL 8 memory and CPU usage.
Screenshot from btop showing MySQL 8 memory and CPU usage.


Sample MySQL 8 Config

The my.cnf configuration file shared below is from a standalone MySQL 8 server that was recently separated from a web server. It consistently performs around 9,000 queries per second (QPS) on average.

However, there are occasional spikes where the QPS increases to around 40,000 and lasts for a few days. These events occur roughly 5 to 10 times a year.

Some of the notable config lines are:


max_conections is set for the 5 to 10 times per year peak connections,


thread_cache_size is set somewhere in between normal traffic and those peak days.


innodb_buffer_pool_instances is set to 48 because innodb_dedicated_server automatically sets innodb_buffer_pool_size to 48 GB. See the chart below:
innodb_dedicated_server and innodb_buffer_pool_size

MySQL buffers

For read_buffer_size, join_buffer_size, sort_buffer_size and read_rnd_buffer_size, please read this important tuning article.


performance-schema, read Performance Schema Benchmarks: OLTP RW.

disable-log-bin, read How Binary Logs Affect MySQL 8.0 Performance.


Paste of MySQL 8 my.cnf

disable-log-bin = 1
skip-name-resolve = 1
performance-schema = 0
local-infile = 0
mysqlx = 0
bind-address = [IPs removed]
open_files_limit = 200000
max_allowed_packet = 256M

innodb_dedicated_server = 1
innodb_buffer_pool_instances = 48
innodb_log_buffer_size = 64M
innodb_read_io_threads = 12
innodb_write_io_threads = 12
innodb_stats_on_metadata = 0
innodb_file_per_table = 1

max_connections = 500
thread_cache_size = 128
table_definition_cache = 65536
table_open_cache = 65536

wait_timeout = 10
connect_timeout = 5
interactive_timeout = 30

tmp_table_size = 128M
max_heap_table_size = 128M

read_buffer_size = 256K
join_buffer_size = 512K
sort_buffer_size = 512K
read_rnd_buffer_size = 512K

slow-query-log = 1
long_query_time = 2
slow_query_log_file = /var/log/mysql_slow_query.log
log-error = /var/log/mysql/db.[removed].com.err

Have questions or suggestions? Add your comment at the end of this article.


MySQL server ‘status’

This is the output of MySQL status for the above MySQL server:

mysql> status
Server version: 8.0.30 MySQL Community Server - GPL
Uptime: 37 days 5 hours 39 min 39 sec
Threads: 8 Questions: 31068214993 Slow queries: 0 Opens: 36331 
Flush tables: 1 Open tables: 36024 Queries per second avg: 9656.974


Continue reading MySQL performance-related guides

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  1. First recommendation is not to depend on innodb_dedicated_server = 1.

    When innodb_dedicated_server is enabled, InnoDB automatically configures the following variables:

    (innodb_log_file_size and innodb_log_files_in_group are deprecated in MySQL 8.0.30. These variables are superseded by the innodb_redo_log_capacity variable.)

    Only enable innodb_dedicated_server if the MySQL instance resides on a dedicated server where it can use all available system resources. For example, consider enabling innodb_dedicated_server if you run MySQL Server in a Docker container or dedicated VM that only runs MySQL.

    That said, you won’t gain any performance by using innodb_dedicated_server if you instead just set the MySQL variables optimally. So, this setting is more of a convenience, as it will simply automatically configure the variables to ~ what you should be using anyway.

    Add your tips below.

  2. Suggestion for MySQL 8 enable slow query log and fix those queries. Also choose InnoDB Over MyISAM as MyISAM is old news.

  3. Hello I have a server with mysql 8.034 with RAM 200GB cpu 18 cores i want to tuning my mysql config
    I put theses values
    ############### my tuning ##############
    join_buffer_size = 512M
    innodb_buffer_pool_size = 160G
    innodb_log_file_size = 512M
    innodb_log_buffer_size = 512M
    interactive_timeout = 200
    wait_timeout = 200
    do you think that values are correct because i always have full RAM used.

  4. Hi @Baba_Ndiaye

    Welcome to our Linux Community :handshake:t4:

    MySQL cannot truly be fined tuned without logging and analyzing at least several hours of runtime stats. (or more for less busy servers)

    That said, there are some general mistakes to avoid before tuning.

    For example, please read: MySQL Database Performance: Avoid this common mistake

    As per the article and MySQL documentation referenced:
    your join_buffer is almost certainly too high.
    Your wait timeout is far too high. (also see above article)

    Also see: MySQL 8 sample config (my.cnf example) and tuning.
    If this is a dedicated MySQL server you should use: innodb_dedicated_server to avoid misconfig. (as per the above article)

    Hope this is helpful.

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