To increase the MySQL server performance if there are many hosts and if DNS is slow, consider disabling DNS lookups with –skip-name-resolve or consider increasing the value of HOST_CACHE_SIZE define (default value: 128) and recompiling the server. These methods are very effective and improve the server performance a lot.
Sometimes, all connections to the database appear to be slow due to the DNS being slow. In such cases, conversions from IP addresses to the corresponding hostnames can be stopped by using the skip-name-resolve parameter. To disable DNS lookups the following line can be added in the my.cnf file:-
skip-name-resolve
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