My guts tell me you have WordPress, Drupal or similar heavy-weight PHP application installed and now you are wondering why your Apache does not serve out ONE HUNDRED BILLION requests per second.
The truth is that nowadays you first have to tune everything on top of Apache (or any other web server software). Most likely the bottleneck is in your application, [lack of] caching, bad database/SQL query design, some database software running with its default settings, or some other reason.
In your typical environment the web server software itself is the last one needing any kind of optimization, unless your traffic amount is hefty.
Please be more specific and tell us why and what you are actually trying to performance tune.
Edit after your comment
Still, before going as far as optimizing Apache, you need to carefully study and benchmark your application and database on top of it.
"Why he's repeating that, I just wanna optimize my Apache!!", you probably now wonder.
It all comes up to how fast your application can render something that Apache can serve out. If your app and/or database takes two seconds to return something, then optimizing Apache itself is pretty much useless, it won't make anything faster if the bottleneck is elsewhere. And, in any case, after running those benchmarks you can have an idea how to begin tuning your Apache.
So, what to do if your application is slow?
Varnish or a similar front-end cache,
memcached etc would be more a performance boost in that case, not tuning Apache.