I’m not sure, I’m not very familiar with snappy, but I think you have to set a value in the jpyconfig.py script in the snappy folder.
Try setting
jvm_maxmem = None
to
jvm_maxmem = '6G'
Another place to change the memory usage might be in snappy.ini in the snappy folder.
Change the line
# java_max_mem: 4G
to e.g.
java_max_mem: 6G