Limiting LighMass Usage of RAM?

basically is there a way to tell UnrealLighmass not to use all my RAM when baking light?
i have 12 GB of RAM and windows takes 1.5 GB and UEditor takes another 1GB so that leaves 9.5 GB of memory (free + cached) to be used when baking light and if lightmass needs more, then it should cache my hard drive before reaching memory limit and not to dominate over Windows portion of memory, is this possible?