I'm using a very small MariaDB instance as a datastore for my YouLess energy monitor , my own mail server (postfix, roundcube). It's a virtual machine from a commercial VPS provider. All data fits in memory and the overhead of running with performance_schema on is not an issue. While I was reading a blog post about performance_schema by Mark Leith I wanted to see what P_S could tell me about my own server. This is the output from the first query: mysql> select * from file_summary_by_event_name order by count_read desc,count_write desc limit 10; +--------------------------------------+------------+-------------+--------------------------+---------------------------+ | EVENT_NAME | COUNT_READ | COUNT_WRITE | SUM_NUMBER_OF_BYTES_READ | SUM_NUMBER_OF_BYTES_WRITE | +--------------------------------------+------------+-------------+--------------------------+---------------------------+ | wait/io/file/sql/FRM | 25387 | ...