Performance

Hello,

Ich have a big performance problem.
I'm running postgres 7.4.2 on Suse Linux 9.0 on a dual Xeon 3.0 GHz with 3
Gbyte Ram.
In postgres.conf I'm using the defaults. Filesystem is ext3 with writeback
journaling

I have 3 tables with ca 10 million entries with a gist index on GIS data and
5 tables with 10 million entries with an index on (timestamp,double,double).
There are 10 tables with 1 million entries and index on int. and some
smaller tables.

With 1 Gbyte Ram all went fine. Than I added a new table and it startet to
swap. I added 2 Gbyte but the Problem is still there.
The kswapd and kjournald are running nearly permanently.

The first time I do a query it takes very long. But the second time it goes
a lot faster.

Is postgres only using a certain amount of Ram for the indexes? But why my
Ram is full then?
Am I too short of Ram? Is the filesystem too slow?

Can anyone help me?

Greeting
Jens