The cause is how your site is setup. The only way to free up processes is to have less processes. 😉
What hosting and platform are you on? Maybe this article will help.
If you have a WordPress site, look at your theme and the number (and quality) of the plugins you have installed and only keep those you just have to have. If you are having resource issues -- less is more.
Judith "Many of life's failures are people who did not realize how close they were to success when they gave up." ~Thomas Edison