I have some php sites and ruby on rails sites on my VDS, but I have no idea how many processes should be spawned. I'm using lighty and have PHP_FCGI_CHILDREN arbitrarily set to 5. Each php-cgi process seems to consume about 20megs of ram and each mongrel_rails process takes up 35megs, so I'd like really like to take control of this so I can keep my memory load down.
