Apache / PHP Memory Usage

On my Virtualmin server, I’m seeing high Apache and PHP usage. I expect this, since every website on the server is running WordPress. However, is there anything I can do to optimize it / make it use less memory? I’ve tried editing the preform.c values, but it doesn’t really seem to be making a large impact.

Here’s my running processes / usage: (I just restarted Apache a few minutes ago, so there’s usually more processes spawned.) http://pastebin.com/w7k9yxdZ

How about adding some caching (there are caching plugins for wordpress) or you may install varnish in front of it. This will at least seriously limit the necessary httpd processes.

This might be a better representation of current and longer-term usage. MySQL seems to be taking up the majority of usage.

http://pastebin.com/aeM8GkzN

I have WP Super Cache on all of the wordpress sites. I will look into Varnish for the HTTP requests. Any advice for MySQL? I’ve run MySQLTuner and followed its advice…not much change in the amount of memory it uses.