an option to mlock indexes or preallocate memory would be nice.

in our case we want to have all our data in mem for quicker access, the option to preallocate memory to the mongo daemon or strictly set locking indexes to memory would be very helpful.
our data will possible exceed 100gb and we eventually preparing a read slave with 256gb of ram to keep the database very fast.
in this constellation a trigger similar to memcache's -m flag to preallocate memory would be very helpful.

just some way to ensure that the data and/or indexes are fully copied to mem would make my life much easier...

thanks!