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

A while back, I wrote the article Tuning MySQL my.cnf? Avoid this common pitfall! With the release of MySQL 8 I wanted to paste some of a my.cnf config file for discussion, suggestions and questions.

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

MySQL 8 dedicated server


Sample MySQL 8 Config

This my.cnf config is from a dedicated MySQL 8 server that was recently split from a web server. It averages a modest 9k QPS (queries per second), however around 5 to 10 times a year the QPS will spend a few days averaging ~ 40k QPS.

Some notable config areas are:

max_conections and thread_cache_size. max_conections is set for the 5 to 10 times per year peak-connections, while 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 below chart:
innodb_dedicated_server and innodb_buffer_pool_size

read_buffer_size, join_buffer_size, sort_buffer_size and read_rnd_buffer_size, please read here.

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

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

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

Paste of my.cnf:

disable-log-bin = 1
skip-name-resolve = 1
performance-schema = 0
local-infile = 0
mysqlx = 0
bind-address = [IPs removed]
default-storage-engine = InnoDB
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 = 1M
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


MySQL server ‘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


Other MySQL performance related reading/guides:

Could not increase number of max_open_files to more than… (Solution).

MySQL Performance Tuning: Tips, Scripts and Tools.

MySQL Performance: Stop hoarding. Drop unused MySQL databases.

“MySQL server has gone away” error – Solution(s).

Tuning MySQL my.cnf? Avoid this common pitfall!

Linux server performance: Is disk I/O slowing your application?


See below for MySQL 8 tuning discussion. My.cnf config questions are welcome!

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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, with a innodb_dedicated_server enabled, you won’t gain any performance by using innodb_dedicated_server if you instead just set the automatically configured 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.

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