Why mysql application is utilizing 100% cpu?
Environment
- Red Hat Enterprise Linux 5
- Red Hat Enterprise Linux 6
Issue
- Top command is reporting 100% cup is being utilized by mysql.
Resolution
- Database tuning is require. indexing etc....
Root Cause
-
Slow query logs were reporting that some queried were running for long time ( Query time was increased because of no of rows mysql had to examined).
-
Example:
# Query_time: 33.400307 Lock_time: 2.295032 Rows_sent: 3 Rows_examined: 3420581
# Query_time: 33.408299 Lock_time: 2.298814 Rows_sent: 3 Rows_examined: 3420581
# Query_time: 33.424737 Lock_time: 2.293420 Rows_sent: 3 Rows_examined: 3420581
# Query_time: 33.445227 Lock_time: 2.283884 Rows_sent: 3 Rows_examined: 3420581
# Query_time: 33.465387 Lock_time: 2.304770 Rows_sent: 3 Rows_examined: 3420581
- If such queries runs, obviously it is expected that it will hit CPU eventually.
Diagnostic Steps
- Checked mysql slow query logs.
- Checked mysql logs.
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