[e12e]

The Apache documentation has a nice overview:

http://httpd.apache.org/docs/2.2/mod/prefork.html

essentially it forks before a request comes in, the master process pushes requests to an idle "pre-forked" worker process. Works pretty well under Linux with pretty light processes - pretty badly under windows nt where processes are much fatter than threads.

The main process tries to maintain a pool of idle workers so there is no need to wait for a fork before an incomming request is handled.