How much memory PostgreSQL is going to use?

Hi all,

   I have a server with 4GB of memory and I'm tweaking the PostgreSQL
configuration. This server will be dedicated to run PostgreSQL so I'd
like to dedicate as much as possible RAM to it.

   I have dedicated 1GB to shared_buffers (shared_buffers=131072) but
I'm not sure if this will be the maximum memory used by PostgreSQL or
additional to this it will take more memory. Because if shared_buffers
is the maximum I could raise that value even more.

Cheers!
--
Arnau