NFS performance 2.4.21 vs 2.6.7-rc2

Cross posting to NFS list as well.

Hello,

I have been doing some testing of NFS performance with
2.4.21 and 2.6.7-rc2 (2.6.5 and 2.6.6 as well).  I
have noticed that 2.4.21 seems to be faster with the
same hardware and mount options as noted by iozone
(iozone -s 1g -r 1m -o).  As well, the amount of CPU
power on the server side is higher for the test run
under 2.6.7-rc2.  Is this known, or have I done
something incorrect?

2.4.21:

1048576    1024   46646   60697   814945   845351 
844893   24716  845657  106998  845220    44423   
60731  811409   841193

2.6.7-rc2:
1048576    1024   42944   48703   536023   546492 
543524   23445  537662   83739  544263   188456  
259651  538667   537420

I have run the same test against NetApp filers and two
different linux file server (2.4.22 and 2.6.7-rc2). 
The client is a 2x 3.0GHz w/8G RAM, Ge (tg3).

Thank you for your time.
Phy