I have a MySQL server with multiple websites running on it. These sites are mostly the same software, but since recently MySQL is under very high CPU load.

I'm pretty sure there is 1 MySQL user that is causing the higher load, but how can I identify the resources used per user?

I know I can limit the number of connections and number of queries per user, but before enforcing limits, I want to know what the current numbers are.

How can this be measured (in MySQL 5.7)?