Site Resource Limits

Hi first off my VPS is running 10 Wordpress sites and is on a 15mbit internet connection, 384 MB of RAM, Six Core AMD Opteron Processor & runs Ubuntu.

Wordpress is a very backend intensive service, using apache, php & mysql.

When people go to one of the Wordpress sites it is generally slow 4 secs average compared with 0.2 secs for a html and i notice that php, mysql only use about 4% of the CPU.

I want to know what settings i can change to allow sites to use more of the CPU with out crashing the server and to provide equal resources to the other sites. Or if one user is uploading files, i don't want to kill other users. The bottel necks are php, mysql and maybe apache.

So could some one give me some advice on the configuration on these.

Thanks, Dave