The No-Op (coop) IO Scheduler/elevator
The algorithms used to schedule disk IO requests are referred to as elevator algorithms. Since 2.6 you have had the choice of the Deadline elevator, the Anticipatory elevator (as), the No-op (noop) elevator and the Completely Fair Queuing (CFQ) elevator.
The No-Op elevator pretty much does what it says on the tin - carries out no optimisation. All requests are put on the block devices' FIFO queue as they arrive. This may seem like an odd elevator, but if you have intelligent disk controllers (hardware RAID etc) or other intelligent block devices then requests may well be rescheduled by the controller, therefore you're just wasting CPU time trying to order/optimise them yourself.
As the elevator carries out no optimisation it has no settings that can be tuned.