By default a job that has less than 10 mappers only and one reducer, and the input size is less than the size of one HDFS block is said to be small job. These values may
be changed for a job by setting mapreduce.job.ubertask.maxmaps ,
mapreduce.job.ubertask.maxreduces , and mapreduce.job.ubertask.maxbytes
It’s also possible to disable Uber tasks entirely by setting mapreduce.job.ubertask.enable to false.
