title: Limit number of concurrent map tasks in Hadoop 2.6.0
body: <p>I want to restrict number of simultaneously map tasks running at one slave node.</p>
  
  <p>In my case, when I submit my job, Hadoop generate 8 map tasks, when I looked at Job history UI at port 19888, I always saw that 8 map tasks started at the same time at same slave node.</p>
  
  <p>Even I tried to set this attribute <code>mapreduce.tasktracker.map.tasks.maximum</code> equal to 4 (from <a href="https://stackoverflow.com/questions/14380841/how-to-restrict-the-concurrent-running-map-tasks">how to restrict the concurrent running map tasks?</a>). It still didn't work for me.</p>
  
  <p>Does anyone have a experiment to deal with this issue?</p>