cloudlinux, php version selector and sites slowing down

One of the software’s we use on our servers is http://www.cloudlinux.com/ this allows the customer to choose which version of PHP he wants on his account, this selection is done on the cpanel, it secures the site so if one site is hacked the server is not damaged and other sites on the server are secure and it controls the resources one site can use, the more resources you use will cause your site to load slow, until all your resources available for your site are used and then your site stops loading until the resources are back to normal.