Generally speaking, once you've gotten to the point of swapping, even a little, you've gone too far. A better approach is to pick some conservative number, like 10-25% of your ram for shared_buffers, and 1 gig or so for maintenance work_mem, and then increase them while exercising the system, and measure the difference increasing them makes. If going from 1G shared buffers to 2G shared buffers gets you a 10% increase, then good. If going from 2G to 4G gets you a 1.2% increase, it's questionable. You should reach a point where throwing more shared_buffers stops helping before you start swapping. But you might not. Same goes for maintenance work mem. Incremental changes, accompanied by reproduceable benchmarks / behaviour measurements are the way to determine the settings. Note that you can also vary those during different times of the day. you can have maint_mem set to 1Gig during the day and crank it up to 8 gig or something while loading data. Shared_buffers can't be changed without restarting the db though.
I'm currently benchmarking various configuration adjustments. Problem is these tests take a really long time because I have to run the load process... which is like a 9 hour deal. That's why I'm asking for advice here, because there's a lot of variables here and it's really time costly to test :)
I'm still working on the benchmarkings and by Friday I should have some interesting statistics to work with and maybe help figure out what's going on.
Thanks! Steve
