[BusyBox] 2.4 / 2.6 problems

[Luke Albers]

I have a system that boots off of compactflash, running on a PC-104 SBC
with a Geode 300MHz processor and 256MB ram.  I am using one of the
latest stable releases of busybox, I forget the exact version and cannot
get to it right now to check.  I am using linux 2.6.5.

This board connects to serial boards, which are connected to devices
that I need to poll as fast as possible.  The software which does the
polling runs extremely fast on comparable PC's, and also when I move up
to a PC-104 board with a 600MHz Celeron processor.  Unfortunately, when
I ran it on my setup, it ran extremely slow, and consumed a lot of the
CPU, making the system run very slow and generating a lot of heat. 
Yesterday I got kernel 2.4.20 running on it, and after testing I found
out that it runs as fast as I would like it to.  I need to run this on a
2.6 kernel though, so I need to find out what the problem is here.

Can anyone tell me what any of the possible differences might be between
the kernels that causes the slowdown on 2.6?  And, it does not have to
do with the serial drivers, because using TCP instead of serial produces
the same results.  I am using NPTL with both 2.4 and 2.6 (the 2.4 is a
redhat kernel that I think was patched to use NPTL or something like
that).  

I know that this isnt really a busybox question (although I guess its
possible that busybox could be part of the problem), but I couldnt think
of a better place to post this.

Thanks
-- 
Luke Albers
Georgia Institute of Technology, Electrical Engineering
Email:  gtg940r at mail.gatech.edu
Web:    www.lukealbers.com