I want to turn performance_schema ON in mysql to collect statistics.
How can I achieve this?
The following guide is linux-specific, but should easily be adaptable to windows.
You have to check wether the mysql server binary was compiled with support for it:
mysqld --verbose --help|grep performance-schema
If the last command returned anything, you are good to go.
Enable it on server startup by putting into /etc/mysql/my.cnf
[mysqld]
performance_schema
Afterwards do a systemctl restart mysqld (redhat) (or systemctl restart mysql on debian/ubuntu) to restart the mysql server.
On how to use the performance schema engine and its output, see the manual:
https://dev.mysql.com/doc/refman/5.5/en/performance-schema-quick-start.html