25.12.3 Performance Schema Instance Tables
Instance tables document what types of objects are instrumented. They provide event names and explanatory notes or status information:
cond_instances
: Condition synchronization object instancesfile_instances
: File instancesmutex_instances
: Mutex synchronization object instancesrwlock_instances
: Lock synchronization object instancessocket_instances
: Active connection instances
These tables list instrumented synchronization objects, files, and connections. There are three types of synchronization objects: cond
, mutex
, and rwlock
. Each instance table has an EVENT_NAME
or NAME
column to indicate the instrument associated with each row. Instrument names may have multiple parts and form a hierarchy, as discussed in Section 25.6, “Performance Schema Instrument Naming Conventions”.
The mutex_instances.LOCKED_BY_THREAD_ID
and rwlock_instances.WRITE_LOCKED_BY_THREAD_ID
columns are extremely important for investigating performance bottlenecks or deadlocks. For examples of how to use them for this purpose, see Section 25.19, “Using the Performance Schema to Diagnose Problems”