For purposes of performance tuning it should be possible to set some environment variables that Hadoop honors before launching the Hadoop daemons. For e.g. to set the heap size of the JVM, we should set the HADOOP_HEAPSIZE variable. These can be configured through hodrc using the gridservice-mapred.envs environment variable. This works for everything except HADOOP_OPTS, which is also useful, for e.g. to pass in Garbage collection parameters to the JVM, like -XX:+UseParallelGC. This is because HOD tries to set HADOOP_OPTS from the gridservice-mapred.java-opts variable, but it does not read the java-opts variable anywhere properly.