kernels performance difference

I have a kernel version problem: 2.6.10 and 2.6.11 are much slower
than 2.6.9 in Fedora Core 3 within a certain function.

One machine runs 8.03, 512 MB, XP2100.
Times: 2.6.11 and 2.6.10 - 83 minutes. 2.6.9 - 32 minutes

In another FC3 machine, 8.0.1, 1 GB, P4 2.4, the times are 35 and 5
minutes respectively.

I think memory size and a faster HD are probably the cause for the
difference between machines. But I don't care about the machines
differences but I care about the kernel differences. Due to the huge
performance difference I'm stuck with 2.6.9.

Since I'm not knowledgeable enough to find the source of the kernel
problem I'm asking if someone could try it.

I prepared the files to download from http://txt.fahstats.com :

restorecontext.sh - creates a test database and loads a table and a function
testit.sh - runs the function
usuarios_producao.txt.bz2 - table dump 3.9 MB
create_function_update_ranking_usuarios.sql - function
postgresql.conf

To test run restorecontext.sh then testit.sh

By the way, if someone knows a better way to update a ranking table,
please let me know.

Regards, Clodoaldo Pinto