MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
These views summarize file I/O, grouped by user and event type. By default, rows are sorted by user and descending total latency.
The user_summary_by_file_io_type
and
x$user_summary_by_file_io_type
views have these columns:
user
The client user name. Rows for which the
USER 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.
event_name
The file I/O event name.
total
The total number of occurrences of the file I/O event for the user.
latency
The total wait time of timed occurrences of the file I/O event for the user.
max_latency
The maximum single wait time of timed occurrences of the file I/O event for the user.