Devel::Size is far from accurate when it comes to complex hashes, beware.

My recent project which had some 140,000 hashes inside another hash reported its size significantly differently between Linuxes 'top' and Devel::Size.
While I am not entirely sure why this is the case, it still happened; top would say the programme was at 70MB resident and Devel::Size would say 40MB, and I can assure you the actual code itself manipulating the data did not occupy all of 30MB.

At any rate, your mileage may vary - I just wouldn't use Devel::Size to be particularly accurate without evaluating exactly what type of data structure you are using, and comparing what the OS thinks the resident size is, and what Devel::Size thinks it is.

JP,
-- Alexander Widdlemouse undid his bellybutton and his bum dropped off --