I really do not think sysctl makes sense for this. We do not create global knobs that affect network drivers like this. If there is going to be a knob, it should be per-interface, via ifconfig.
Additionally, I am *extremely sceptical this code works. If the sysctl is changed, network interfaces don't notice that it changed. They need an ifconfig down/up. Also if they hit a watchdog timer, or go through suspend/resume, it will change behaviour, because ixgbe_init() gets called. Very wrong.
