At the MySQL commandline, you can enter
and see what processes are running.
If you’re tracking down some problematic code and you’ve got a query (or set of queries) that don’t end, consume CPU cycles and generally bog everything down to a crawl, it can be helpful to know what time you’ve run the command above. Thusly, I now run this:
show processlist; select now as current_date_time;
and it rather nicely tells me the current date/time on the MySQL server, using the Time column from the processlist, you can work out a tad more accurately when a query started, giving you a starting point to look in other logs.
Now those long running sql queries are easier to track down.