Understanding how MySQL uses memory is key to tuning it for optimal performance as well as troubleshooting cases of unexpected memory usage, i.e. when you have MySQL Server using a lot more than you would expect based on your configuration settings. Early in MySQL history, understanding memory usage details was hard and included a lot [&]

https://www.percona.com/blog/2020/11/02/understanding-mysql-memory-usage-with-performance-schema/