Ah. I guess it's only useful for an optimized router/firewall or network storage appliance, perhaps with a bespoke stack carefully tuned to quickly process and then hand the data back to the controller (via DDIO) before it flushes.
EDIT: Here's an interesting writeup about trying to make use of it with FreeBSD+netmap+ipfw: https://adrianchadd.blogspot.com/2015/04/intel-ddio-llc-cach... So it can work as advertised, it's just very constraining, requiring careful tuning if not outright rearchitecting your processing pipeline with the constraints in mind.
EDIT: Here's an interesting writeup about trying to make use of it with FreeBSD+netmap+ipfw: https://adrianchadd.blogspot.com/2015/04/intel-ddio-llc-cach... So it can work as advertised, it's just very constraining, requiring careful tuning if not outright rearchitecting your processing pipeline with the constraints in mind.