Increasing Java heap size for a class inside a jar
I believe you need to increase the memory allocation for the launched map tasks. The default is 200 MB which seems to be insufficient in your case. If the driver class is a subclass of Tool, you can pass the following arguments -Dmapred.child.java.opts=-Xmx500m . Here , you are bumping up the memory from 200 to 500.
You can also do profiling of your map reduce job to see which objects are taking up memory.