TCP Overhead on Local Loopback

Hi all,

We are running performance tests using PG 8.3 on a Windows 2008 R2 machine connecting locally over TCP.
In our tests, we have found that it takes ~3ms to update a table with ~25 columns and 60K records, with one column indexed.
We have reached this number after many tweaks of the database configuraiton and one of the changes we made was to perform the updates in batches of 5K as opposed to the pervious transaction per event. Note that our use of batches is to have only one transaction, but still each of the 5K events is independently SELECTing and UPDATEing records, i.e. it is not all contained in a stored procedure or such.

Still these times are too high for us and we are looking to lower them and I am wondering about the TCP/IP overhead of passing the information back and forth. Does anyone have any numbers in what the TCP could cost in the configuration mentioned above or pointers on how to test it?

Many thanks,
Ofer