How to cache database?

Reading discussions on scalability, I saw Tom Lane reccomend caching a
"large chunk" of a database as a path to faster performance. Is there
any place I can read up (rtfm) on how to do this? (Specifically
redhat6.2 system running postgres 6.5.x soon to be postgres 7.x)

I expect this could really speed up my database access as I'm dealing
with a small database that has many small nearly static tables (the
restaurant menus) and a few larger highly active tables (customer data
and order data). The small tables are <100 rows each while the large
are thousands and tens of thousands in size. The database is small
(currently dumps into ~6megs) and should be able live in ram without
difficulty.

--

Glenn Wittrock

Linux: when you need to run like a greased weasel.