innodb_thread_concurrency
INFO
Rule IDs: cc_001
Overview
- Purpose
- Documented in the MySQL 8.4 manual as a server system variable (scope: Global). Purpose and semantics are described at the linked manual page.
- Dynamic (MySQL 8.4 reference)
- MySQL 8.4 marks this variable as dynamic (
Dynamic= Yes). Runtime changes useSET GLOBAL(global scope) orSET SESSION(session scope) — confirm syntax and persistence (SET PERSIST) in the manual. - Default value
- 0 (unlimited) (MySQL 8.4)
- Version and product notes
- MariaDB and Percona Server may use different names, defaults, or dynamic behavior; verify their documentation.
- Documentation
- https://dev.mysql.com/doc/refman/8.4/en/innodb-parameters.html#sysvar_innodb_thread_concurrency
- Other vendors
What is checked
Rules that reference this variable, with their severity and what each rule detects:
- INFO
cc_001: Leave innodb_thread_concurrency=0 on modern systems unless MySQL shares the server with other heavy processes.
Tuning guidance
- Recommended actions:
- Leave innodb_thread_concurrency=0 on modern systems unless MySQL shares the server with other heavy processes.
- Trade-offs: Thread concurrency controls balance CPU utilization against contention. Too many concurrent threads cause lock waits; too few leave CPU idle. Auto-management (concurrency=0) works well for most workloads.
Example
SET GLOBAL innodb_thread_concurrency = 0; -- Let InnoDB manage
Always validate on a non-production instance first. Use SET PERSIST (MySQL 8.0+) for changes that should survive restarts.