The file I/O summary tables aggregate information about I/O operations:

For example:

mysql> SELECT * FROM file_summary_by_instance\G
...
*************************** 2. row ***************************
                FILE_NAME: /var/mysql/share/english/errmsg.sys
               EVENT_NAME: wait/io/file/sql/ERRMSG
               COUNT_READ: 3
              COUNT_WRITE: 0
 SUM_NUMBER_OF_BYTES_READ: 42211
SUM_NUMBER_OF_BYTES_WRITE: 0
...
*************************** 6. row ***************************
                FILE_NAME: /var/mysql/data/binlog.000001
               EVENT_NAME: wait/io/file/sql/binlog
               COUNT_READ: 0
              COUNT_WRITE: 0
 SUM_NUMBER_OF_BYTES_READ: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
...

TRUNCATE TABLE is permitted for file I/O summary tables. It resets the counters to zero rather than removing rows.

The file I/O summary tables have these grouping columns to indicate how events are aggregated:

The file I/O summary tables have these summary columns containing aggregated values:

The MySQL server uses several techniques to avoid I/O operations by caching information read from files, so it is possible that statements you might expect to result in I/O events will not. You may be able to ensure that I/O does occur by flushing caches or restarting the server to reset its state.