I'm asking the question after reading this article http://stevehanov.ca/blog/index.php?id=95
Also isn't it a penalty to use cgi instead of fastcgi ?
Update: why some people do pretend like in answer "that you get 20-30% performance improvement" ? Is it pure guess or is this number coming from solid benchmark ? I have looked at HipHop performance is more in the scale of 10 times.