Postgresql optimization

Friends,

I have what seems to me to be a fairly beefy Linux box (2x1Ghz cpu, 768meg
memory) that is a dedicated Postgres server, and which hasn't been
performing the way I felt it should.

I found a good article on the web about optimizing Postgres on Linux, (
http://www.phpbuilder.com/columns/smith20010821.php3?print_mode=1 )and the
thing that seems to be the bottleneck for my database appears to be the
amount of memory that Linux sets aside for shared memory space. I set my
machine up like the guy in the article (by doing echo 128000000 >
/proc/sys/kernel/shmmax to set the shared memory to 128 megs), and things
are going way faster now than they were. I'm still at 340 megs free on the
machine, and I would like to bump this up by half again (192 megs), and then
up to double (256 megs) if that works out, however I don't really understand
all the ramification for this, so I just wanted to check with y'all and see
if you thought I would be getting myself in trouble...

Thanks,
Peter Darley