title: How many cores each Hadoop map task use?
body: <p>I'm running Hadoop task on a cluster of YARN with max of 8 tasks and 16 cores.
  When I run the job I see 8 tasks running on a node yet all 16 cores been used.
  Is map task is multi threaded ? 
  Map task use more than 1 core ?
  Can I know which cores used each map task ?</p>
  
  <p>Thanks,
  Assaf</p>