Design pattern for processing a huge directory tree of files using GPars

I am trying to process millions of files, spread over a tree of directories.  At the moment I can collect the set of top level directories into a list and then process these in parallel using GPars with list processing (e.g. .eachParallel).
But what would be more efficient would be a 'parallel' for the File handling routines, for example:

               withPool() {
                              directory.eachFileMatchParallel (FILES, ~/($fileMatch)/) {aFile ->  ...

then I would be a very happy bunny!

I know I could copy the list of matching files into an Array list and then use the withPool { filesArray.eachParallel { ... - but this does not seem like an efficient solution - especially if there are several hundred thousand files in a directory.

What design pattern(s) might be better to consider using?

Merlin Beedell