Description of the flags used for the BEA SPECjbb2000 results: -Xgc:parallel Starts the parallel garbage collector. -XXminblocksize:12k This flag sets the minimal block size allowed on the freelist. For performance reasons we don’t want to have all free areas of the heap on the freelist, just those that are big enough (bigger than or equal to minblocksize). Default: 2 kb.