29.6 Performance Schema Instrument Naming Conventions (original) (raw)

An instrument name consists of a sequence of elements separated by'/' characters. Example names:

wait/io/file/myisam/log
wait/io/file/mysys/charset
wait/lock/table/sql/handler
wait/synch/cond/mysys/COND_alarm
wait/synch/cond/sql/BINLOG::update_cond
wait/synch/mutex/mysys/BITMAP_mutex
wait/synch/mutex/sql/LOCK_delete
wait/synch/rwlock/sql/Query_cache_query::lock
stage/sql/closing tables
stage/sql/Sorting result
statement/com/Execute
statement/com/Query
statement/sql/create_table
statement/sql/lock_tables
errors

The instrument name space has a tree-like structure. The elements of an instrument name from left to right provide a progression from more general to more specific. The number of elements a name has depends on the type of instrument.

The interpretation of a given element in a name depends on the elements to the left of it. For example, myisam appears in both of the following names, butmyisam in the first name is related to file I/O, whereas in the second it is related to a synchronization instrument:

wait/io/file/myisam/log
wait/synch/cond/myisam/MI_SORT_INFO::cond

Instrument names consist of a prefix with a structure defined by the Performance Schema implementation and a suffix defined by the developer implementing the instrument code. The top-level element of an instrument prefix indicates the type of instrument. This element also determines which event timer in theperformance_timers table applies to the instrument. For the prefix part of instrument names, the top level indicates the type of instrument.

The suffix part of instrument names comes from the code for the instruments themselves. Suffixes may include levels such as these:

• A name for the major element (a server module such asmyisam, innodb,mysys, or sql) or a plugin name.

• The name of a variable in the code, in the form_XXX_ (a global variable) or_`CCC`_::_`MMM`_ (a member MMM in class_CCC_). Examples:COND_thread_cache,THR_LOCK_myisam,BINLOG::LOCK_index.

• Top-Level Instrument Elements

• Idle Instrument Elements

• Error Instrument Elements

• Memory Instrument Elements

• Stage Instrument Elements

• Statement Instrument Elements

• Thread Instrument Elements

• Wait Instrument Elements

Top-Level Instrument Elements

• idle: An instrumented idle event. This instrument has no further elements.
• error: An instrumented error event. This instrument has no further elements.
• memory: An instrumented memory event.
• stage: An instrumented stage event.
• statement: An instrumented statement event.
• transaction: An instrumented transaction event. This instrument has no further elements.
• wait: An instrumented wait event.

Error Instrument Elements

The error instrument indicates whether to collect information for server errors and warnings. This instrument is enabled by default. The TIMED column for the error row in thesetup_instruments table is inapplicable because timing information is not collected.

Memory Instrument Elements

Memory instrumentation is enabled by default. Memory instrumentation can be enabled or disabled at startup, or dynamically at runtime by updating theENABLED column of the relevant instruments in the setup_instruments table. Memory instruments have names of the formmemory/_`codearea`_/_`instrumentname`_ where codearea is a value such assql or myisam, and_instrumentname_ is the instrument detail.

Instruments named with the prefixmemory/performance_schema/ expose how much memory is allocated for internal buffers in the Performance Schema. The memory/performance_schema/ instruments are built in, always enabled, and cannot be disabled at startup or runtime. Built-in memory instruments are displayed only in thememory_summary_global_by_event_name table. For more information, seeSection 29.17, “The Performance Schema Memory-Allocation Model”.

Stage Instrument Elements

Stage instruments have names of the formstage/_`codearea`_/_`stagename`_, where codearea is a value such assql or myisam, and_stagename_ indicates the stage of statement processing, such as Sorting result or Sending data. Stages correspond to the thread states displayed by SHOW PROCESSLIST or that are visible in the Information Schema PROCESSLIST table.

Statement Instrument Elements

• statement/abstract/*: An abstract instrument for statement operations. Abstract instruments are used during the early stages of statement classification before the exact statement type is known, then changed to a more specific statement instrument when the type is known. For a description of this process, seeSection 29.12.6, “Performance Schema Statement Event Tables”.
• statement/com: An instrumented command operation. These have names corresponding toCOM_ _`xxx`_ operations (see the mysql_com.h header file and sql/sql_parse.cc. For example, the statement/com/Connect andstatement/com/Init DB instruments correspond to the COM_CONNECT andCOM_INIT_DB commands.
• statement/scheduler/event: A single instrument to track all events executed by the Event Scheduler. This instrument comes into play when a scheduled event begins executing.
• statement/sp: An instrumented internal instruction executed by a stored program. For example, thestatement/sp/cfetch andstatement/sp/freturn instruments are used cursor fetch and function return instructions.
• statement/sql: An instrumented SQL statement operation. For example, thestatement/sql/create_db andstatement/sql/select instruments are used for CREATE DATABASE andSELECT statements.

Thread Instrument Elements

Instrumented threads are displayed in thesetup_threads table, which exposes thread class names and attributes.

Thread instruments begin with thread (for example, thread/sql/parser_service orthread/performance_schema/setup).

The names of thread instruments forndbcluster plugin threads begin withthread/ndbcluster/; for more information about these, see ndbcluster Plugin Threads.

Wait Instrument Elements

• wait/io
  An instrumented I/O operation.
  • 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 to fwrite()). 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/_`sockettype`_. 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 a_sockettype_ 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 a sockettype value of client_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
  An instrumented lock operation.
  • wait/lock/table
    An instrumented table lock operation.
  • wait/lock/metadata/sql/mdl
    An instrumented metadata lock operation.
• wait/synch
  An instrumented synchronization object. For synchronization objects, the TIMER_WAIT time includes the amount of time blocked while attempting to acquire a lock on the object, if any.
  • 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 priority rwlock lock object.
  • wait/synch/rwlock
    A plain read/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.