5.2 Database File I/O pages

The Database file I/O section contains the following dashboards:

Database File I/O By Host

The Database File I/O By Host dashboard summarizes the file I/O, grouped by host.

Table 5.2 Database File I/O By Host

NameDescription

Host

The host from which the client connected. Rows for which the HOST column in the underlying Performance Schema table is NULL are assumed to be for background threads and are reported with a host name of background.

Total

The total number of file I/O events for the host.

Total Latency

The total wait time of timed file I/O events for the host.


Database File I/O By Thread

The Database File I/O By Thread dashboard summarizes I/O consumers to display time waiting for I/O, grouped by thread.

Table 5.3 Database File I/O By Thread

NameDescription

Thread ID

The thread identifier.

User

For foreground threads, the account associated with the thread. For background threads, the thread name.

Average Latency

The average wait time per timed I/O event for the thread.

Max Latency

The maximum single wait time of timed I/O events for the thread.

Min Latency

The minimum single wait time of timed I/O events for the thread.

Process List ID

For foreground threads, the processlist ID of the thread. For background threads, NULL.

Total

The total number of I/O events for the thread.

Total Latency

The total wait time of timed I/O events for the thread.


Database File I/O By File

The Database File I/O By File dashboard summarizes global I/O consumers to display amount of I/O, grouped by file.

Table 5.4 Database File I/O By File

NameDescription

File

The file path name.

Count Misc

The total number of other I/O events for the file.

Count Read

The total number of read I/O events for the file.

Count Write

The total number of write I/O events for the file.

Misc Latency

The total wait time of timed other I/O events for the file.

Total

The total number of I/O events for the file.

Total Latency

The total wait time of timed I/O events for the file.

Write Latency

The total wait time of timed write I/O events for the file.


Database File I/O By Type

The Database File I/O By Type dashboard summarizes global I/O consumers to display amount of I/O and time waiting for I/O, grouped by event.

Table 5.5 Database File I/O By Type

NameDescription

Event

The I/O event name, with the wait/io/file/ prefix stripped.

Average Latency

The average wait time per timed occurrence of the I/O event.

Average Read

The average number of bytes per read for the I/O event.

Average Written

The average number of bytes per write for the I/O event.

Count Read

The number of read requests for the I/O event.

Count Write

The number of write requests for the I/O event.

Max Latency

The maximum single wait time of timed occurrences of the I/O event.

Misc Latency

The total wait time of timed other occurrences of the I/O event.

Read Latency

The total wait time of timed read occurrences of the I/O event.

Total

The total number of occurrences of the I/O event.

Total Latency

The total wait time of timed occurrences of the I/O event.

Total Read

The number of bytes read for the I/O event.

Total Written

The number of bytes written for the I/O event.

Write Latency

The total wait time of timed write occurrences of the I/O event.


InnoDB File I/O

The InnoDB File I/O dashboard displays information on the various file I/O activity on the monitored server.

Table 5.6 InnoDB File I/O Performance Page Regions

NameDescription
Data File IO Activity (bytes)Graphs the amount of data read and written, in bytes.
Data File IO Activity (ops)Graphs the number of fsync() operations, data reads and writes.
Average Bytes Per ReadGraphs the average bytes per read.
Double Write ActivityGraphs the number of doublewrite operations and the number of pages written for doublewrite operations.
Redo Log IO Activity (bytes)Graphs the number of bytes written to the log file.
Redo Log IO Activity (ops)Graphs the number of log write requests and the number of physical log writes.
Redo Log WaitsGraphs the number of times the log buffer was too small and had to be flushed.
Pending IOGraphs the number of pending asynchronous I/O read/write requests,
Pending FlushesGraphs the number of pending buffer and redo log flush operations.
Open FilesGraphs the number of open files in InnoDB.
InnoDB IO ConfigurationLists the InnoDB IO-specific system variables and their values.