10.3 Performance Schema Instance Tables

10.3.1 The cond_instances Table

10.3.2 The file_instances Table

10.3.3 The mutex_instances Table

10.3.4 The rwlock_instances Table

10.3.5 The socket_instances Table

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

• cond_instances: Condition synchronization object instances

• file_instances: File instances

• mutex_instances: Mutex synchronization object instances

• rwlock_instances: Lock synchronization object instances

• socket_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 Chapter 7, 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 Chapter 14, Using the Performance Schema to Diagnose Problems