A general note on this is to be wary of cache levels. It may be more efficient to sort in chunks of the cache level of the machine rather than as large a chunk as possible.
Some very quick testing here (a while ago), shows -S2M -T/dev/shm was as fast or faster than big buffers, as well as being "nicer" to the rest of the system. cheers, Pádraig. p.s. ensure MALLOC_PERTURB_ is unset when benchmarking sort
