Information Schema INNODB_MUTEXES Table

MariaDB starting with 10.1.3

The Information Schema INNODB_MUTEXES table was added in MariaDB 10.1.3

The INNODB_MUTEXES table monitors mutex and rw locks waits. It has the following columns:

ColumnDescription
NAMEName of the lock, as it appears in the source code.
CREATE_FILEFile name of the mutex implementation.
CREATE_LINELine number of the mutex implementation.
OS_WAITSHow many times the mutex occurred.

The CREATE_FILE and CREATE_LINE columns depend on the InnoDB/XtraDB version.

Note that since MariaDB 10.2.2, the table has only been providing information about rw_lock_t, not any mutexes. From MariaDB 10.2.2 until MariaDB 10.2.32, MariaDB 10.3.23, MariaDB 10.4.13 and MariaDB 10.5.1, the NAME column was not populated (MDEV-21636).

The SHOW ENGINE INNODB STATUS statement provides similar information.

Examples

SELECT * FROM INNODB_MUTEXES;
+------------------------------+---------------------+-------------+----------+
| NAME                         | CREATE_FILE         | CREATE_LINE | OS_WAITS |
+------------------------------+---------------------+-------------+----------+
| &dict_sys->mutex             | dict0dict.cc        |         989 |        2 |
| &buf_pool->flush_state_mutex | buf0buf.cc          |        1388 |        1 |
| &log_sys->checkpoint_lock    | log0log.cc          |        1014 |        2 |
| &block->lock                 | combined buf0buf.cc |        1120 |        1 |
+------------------------------+---------------------+-------------+----------+

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