Are you trying to run some MySQL based software on a server with low memory (AWS micro, Vultr micro) and keep running out of memory?
If you're running this application on a server with very low memory, it's safe to assume you don't have a lot of performance needs at the moment. You can reduce the memory usage for MySQL drastically by adding this line in the
performance_schema = 0
And then restart your MySQL server
sudo service mysql restart
This simple change can yield a ~10x reduction in idle memory usage from MySQL.