The daemon distributes the incoming IRQs across all CPUs in ordner to increase performance. To ensure that the daemon doesn't influence the IRQ affinity, it simply can be stopped.
This daemon is started from the irqbalance init script. To disable once do:
$ /etc/init.d/irqbalance stop
To disable the deamon permantent do:
$ chkconfig irqbalance off
The irqbalance daemon has a parameter, that already set IRQ affinities for example by kernel comandline or procfs are ignored.