difference between RHEL5 and RHEL6 for sio_ntap action?

Hi all

Since I have been testing with sio_ntap on RHEL5 and 6 environment,

I always got high benchmark score on RHEL6 each test senario and

it's obviously difference between two of them. 

Could anyone tell me that any similar case ?

Test env specs

RHEL 5.11

2.6.18-398.el5 x86_64

RHEL 6.6

2.6.32-504.el6 x86_64

*All parameters set same and difference is only OS version.

Thank you