Short answers:

• Turn off HyperThreading 
• Turn off any cores beyond 8 
• HyperThreading is mostly a thing of the past, so this section may not apply. 

HyperThreading is great for marketing, lousy for performance. It involves having two processing units sharing a single hardware cache. If both units are doing the same thing, the cache will be reasonably useful. If the units are doing different things, they will be clobbering each other's cache entries.

Furthermore MySQL is not great on using multiple cores. So, if you turn off HT, the remaining cores run a little faster.

Mariadb (MySQL)은 많은 CPU 코어를 안쓰므로, HT를 off 하는 것이 이득이다... 뭐 그런.

https://mariadb.com/kb/en/library/mariadb-memory-allocation/