I was asking myself if it could be a good idea to parallelize some of the
alogorithms of Hadoop, such as MergeSorter, for the case a single job of
run on a multicore system. If so, I would like to propose a patch that do
it, by adding a parameter like io.sort.parallelism.
If the number of sorting threads is less than this value, Hadoop will start
more than one thread.