The host_cache table provides access to the contents of the host cache,
which contains client host name and IP address information and is used to avoid DNS lookups.
DNSにキャッシュされた情報を見る事が出来る、合わせて接続エラーなどのの確認も出来る。
この情報は、FLUSH HOSTSかTRUNCATE TABLE host_cacheでFlushする事が出来る。

Reference: 22.9.10.1 The host_cache Table

mysql> select * from performance_schema.host_cache \G
*************************** 1. row ***************************
                                        IP: 192.168.11.10
                                      HOST: 
                            HOST_VALIDATED: YES
                        SUM_CONNECT_ERRORS: 0
                 COUNT_HOST_BLOCKED_ERRORS: 0
           COUNT_NAMEINFO_TRANSIENT_ERRORS: 0
           COUNT_NAMEINFO_PERMANENT_ERRORS: 0
                       COUNT_FORMAT_ERRORS: 0
           COUNT_ADDRINFO_TRANSIENT_ERRORS: 0
           COUNT_ADDRINFO_PERMANENT_ERRORS: 0
                       COUNT_FCRDNS_ERRORS: 0
                     COUNT_HOST_ACL_ERRORS: 0
               COUNT_NO_AUTH_PLUGIN_ERRORS: 0
                  COUNT_AUTH_PLUGIN_ERRORS: 0
                    COUNT_HANDSHAKE_ERRORS: 0
                   COUNT_PROXY_USER_ERRORS: 0
               COUNT_PROXY_USER_ACL_ERRORS: 0
               COUNT_AUTHENTICATION_ERRORS: 1
                          COUNT_SSL_ERRORS: 0
         COUNT_MAX_USER_CONNECTIONS_ERRORS: 0
COUNT_MAX_USER_CONNECTIONS_PER_HOUR_ERRORS: 0
             COUNT_DEFAULT_DATABASE_ERRORS: 0
                 COUNT_INIT_CONNECT_ERRORS: 0
                        COUNT_LOCAL_ERRORS: 0
                      COUNT_UNKNOWN_ERRORS: 0
                                FIRST_SEEN: 2014-07-07 14:20:08
                                 LAST_SEEN: 2014-07-07 14:35:00
                          FIRST_ERROR_SEEN: 2014-07-07 14:35:00
                           LAST_ERROR_SEEN: 2014-07-07 14:35:00

mysql>

接続している、現在のホスト確認はこれまで通り、processlistで良いかと。

mysql> show full processlist;
+----+------+-----------------+--------------------+---------+------+-------+-----------------------+
| Id | User | Host            | db                 | Command | Time | State | Info                  |
+----+------+-----------------+--------------------+---------+------+-------+-----------------------+
|  1 | root | localhost:53678 | performance_schema | Query   |    0 | init  | show full processlist |
+----+------+-----------------+--------------------+---------+------+-------+-----------------------+
1 row in set (0.00 sec)

mysql>