I noticed that mkgmap since a few revistions memory requiresments at least doubled. Two weeks ago everything was still okay, rev >=1350 is however consuming a lot more memory. The thing that makes me think that there is a big leak however is that the memory builds up tile after tile. When rendering Germany with max-jobs=2 I needed 5GB of java heap. Some month ago I did fine with 3GB on max-jobs=3 (without any big changes to either my style, nor an increase in the max-nodes for the splitter). I'll try to find some time to find out if there was a specific revision from which onwards the memory requirements increased.