13.7.5.22 SHOW MUTEX STATUS Syntax

SHOW MUTEX STATUS

SHOW MUTEX STATUS displays InnoDB mutex statistics. From MySQL 5.0.3 to 5.0.32, the statement displays the following output fields:

From MySQL 5.0.33 on, the statement uses the same output format as that just described, but only if UNIV_DEBUG was defined at MySQL compilation time (for example, in include/univ.i in the InnoDB part of the MySQL source tree). If UNIV_DEBUG was not defined, the statement displays the following fields. In the latter case (without UNIV_DEBUG), the information on which the statement output is based is insufficient to distinguish regular mutexes and mutexes that protect rw-locks (which permit multiple readers or a single writer). Consequently, the output may appear to contain multiple rows for the same mutex.

Information from this statement can be used to diagnose system problems. For example, large values of spin_waits and spin_rounds may indicate scalability problems.

SHOW MUTEX STATUS was added in MySQL 5.0.3. In MySQL 5.1, SHOW MUTEX STATUS is deprecated and SHOW ENGINE INNODB MUTEX should be used instead. The latter statement displays similar information but in a somewhat different output format. SHOW MUTEX STATUS is removed in MySQL 5.5.