KeepAlives and MaxClients
It is worth turning off KeepAlive
(see Chapter 3) on busy sites because it keeps the server
connected to each client for a minimum time even if they are doing
nothing. This consumes processes, which consumes memory. Because each
connection corresponds to a process, and each process has a whole
instance of Perl and all the cached compiled code and persistent
variables, this can be a great deal of memory — far more than you
get with more ordinary Apache usage. Likewise, tuning MaxClients to
avoid swapping can improve the performance even though,
paradoxically, it actually causes people to have to wait.
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