You need to set mapreduce.map.java.opts and mapreduce.reduce.java.opts
instead of mapred.child.java.opts to tune JVMs when you use MRv2.
Please note that you also need to tune
mapreduce.map.memory.mb/mapreduce.reduce.memory.mb to notify
ResourceManager of the amounts of resource usage.
This doc is also useful for you.http://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/ClusterSetup.html
On Thu, May 22, 2014 at 10:58 PM, ch huang <[EMAIL PROTECTED]> wrote: