memory usage tasks

[Koert Kuipers]

silly question, but i have our hadoop slave boxes configured with 7 mappers
each, yet i see java 14 process for user mapred on each box. and each
process takes up about 2GB, which is equals to my memory allocation
(mapred.child.java.opts=-Xmx2048m). so it is using twice as much memory as
i expected! why is that?