Troubleshooting guide
Troubleshooting Guide: MariaDB High CPU Usage
Use this guide to work through the most likely causes, gather useful evidence and make production-safe changes without turning a small problem into a larger outage.
MariaDBhigh CPUslow queriesindexesperformance tuning
What this problem usually means
MariaDB high CPU usually means the database is doing expensive work: table scans, joins without indexes, too many concurrent queries, maintenance jobs, or application code repeatedly asking inefficient questions.
Production caution: Killing queries can reduce load temporarily, but the real fix is usually indexing, query changes, workload control or scheduling.
Common symptoms
- mysqld uses high CPU for long periods
- WordPress or application pages load slowly
- CPU spikes at predictable times
- Database process list shows many running queries
- Admin dashboards or checkout pages time out
Common causes
- Missing or unused indexes
- Large table scans from plugins or reports
- Too many concurrent connections
- Cron tasks or backup processes running during traffic
- Poorly optimised queries after an application update
- Storage latency causing queries to pile up
Safe first checks
These checks are intended to assist identify the direction of the issue. Always adjust paths, solution names and commands for your environment.
Show running queries
mysqladmin processlistEnable/check slow query log
mysql -e "SHOW VARIABLES LIKE 'slow_query_log'; SHOW VARIABLES LIKE 'long_query_time';"Check CPU and I/O
top -o %CPU -b -n1 | head -20; iostat -xz 1 3Review table sizes
mysql -e "SELECT table_schema, ROUND(SUM(data_length+index_length)/1024/1024) MB FROM information_schema.tables GROUP BY table_schema ORDER BY MB DESC;"Typical fixes
- Use slow query logs to find repeat offenders
- Add or adjust indexes carefully
- Reduce heavy plugin/reporting workload
- Move maintenance jobs away from peak traffic
- Tune connection and buffer settings to fit server resources
- Investigate disk latency when CPU and I/O rise together
When to get assist
Get assist if the system is production-facing, customer data is involved, backup processes are uncertain, or the issue affects revenue, security hardening or uptime. We can review the logs, confirm the cause and quote a fixed-scope fix where appropriate.
Need this fixed?
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