While looking into MAPREDUCE-5207 (adding defaults for mapreduce.{map|reduce}.memory.mb), I was wondering how much headroom should be left on top of mapred.child.java.opts (or other similar JVM opts) for the container memory itself?
I would like to have separated java option settings for map/reduce parts. Something like mapred.map.child.java.opts mapred.reduce.child.java.opts.