Instance tables document what types of objects are instrumented. They provide event names and explanatory notes or status information:

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 29.6, “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 29.19, “Using the Performance Schema to Diagnose Problems”