I think this has to be performed when the project is starting and not when the project is running, but, I don't decide that. I'm only the developer. I read a lot about performance in Drupal 7, and I saw modules like (Boost, Devel...) but I'm not very experienced with this.
Devel isn't working for my project (when I enter here admin/config/development/devel the page only stay await for a couple of seconds and return a problem with the server [The connection was reset] and nothing happen). AS of yet, I have not tried Boost.
I want to make performance improvements not only for Drupal way but also for Apache+MySQL. I read something and some guys talked about jMeter to make some stress test and other thing. buy, I want to know what you think, what you use and your experience dealing with performance.
(One answer will be: CACHE, but I'm looking something more than a cache).
So much thanks guys!