BTW.: applying "pci=conf1" as boot option sometimes helps
(mostly for multi GPU multi CPU setups, but you may give it
a try nevertheless).
Concerning realtime preemption, have checked the following thread
and applied the appropriate patch to the nvidia driver?
Concerning high latencies with realtime preemption: the nvidia4
SATA controller can cause latencies up to 16.6ms (seems that
there is no way to easily fix that in software). Maybe the ATA
controller is also affected.