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wait/io/file

An instrumented file I/O operation. For files, the wait is the time waiting for the file operation to complete (for example, a call tofwrite()). Due to caching, the physical file I/O on the disk might not happen within this call.

wait/io/socket

An instrumented socket operation. Socket instruments have names of the formwait/io/socket/sql/socket_type. The server has a listening socket for each network protocol that it supports. The instruments associated with listening sockets for TCP/IP or Unix socket file connections have asocket_type value ofserver_tcpip_socket orserver_unix_socket, respectively. When a listening socket detects a connection, the server transfers the connection to a new socket managed by a separate thread. The instrument for the new connection thread has asocket_type value ofclient_connection.

wait/io/table

An instrumented table I/O operation. These include row-level accesses to persistent base tables or temporary tables. Operations that affect rows are fetch, insert, update, and delete. For a view, waits are associated with base tables referenced by the view.

Unlike most waits, a table I/O wait can include other waits. For example, table I/O might include file I/O or memory operations. Thus,events_waits_current for a table I/O wait usually has two rows. For more information, seeSection 29.8, “Performance Schema Atom and Molecule Events”.

Some row operations might cause multiple table I/O waits. For example, an insert might activate a trigger that causes an update.

wait/lock/table

An instrumented table lock operation.

wait/lock/metadata/sql/mdl

An instrumented metadata lock operation.

wait/synch/cond

A condition is used by one thread to signal to other threads that something they were waiting for has happened. If a single thread was waiting for a condition, it can wake up and proceed with its execution. If several threads were waiting, they can all wake up and compete for the resource for which they were waiting.

wait/synch/mutex

A mutual exclusion object used to permit access to a resource (such as a section of executable code) while preventing other threads from accessing the resource.

wait/synch/prlock

A priorityrwlock lock object.

wait/synch/rwlock

A plainread/write lock object used to lock a specific variable for access while preventing its use by other threads. A shared read lock can be acquired simultaneously by multiple threads. An exclusive write lock can be acquired by only one thread at a time.

wait/synch/sxlock

A shared-exclusive (SX) lock is a type ofrwlock lock object that provides write access to a common resource while permitting inconsistent reads by other threads.sxlocks optimize concurrency and improve scalability for read-write workloads.