title: Mesos tasks use more resources than specified
body: <p>I tried to launch a framework that has 1000 tasks, on a Mesos cluster with 208 cores. In scheduler, I specify that each task requires 2 cores. But some tasks just failed with error message: <code>Task uses more resources cpus(*):4; mem(*):4096; disk(*):4096 than available cpus(*):2; mem(*):2048; disk(*):2048</code>.  I also try to monitor the resource usage dynamically on the cluster.  And I noticed that each task actually consume 4 cores based on the information </p>
  
  <pre><code>2016/11/02 02:25:10.073 mesos_scheduler INFO 208.0 cpu 98.0 used, 807768.0 memory 100352.0 used, 44052112.0 disk 100352.0 used, 24.0 active tasks
  2016/11/02 02:25:10.574 mesos_scheduler INFO 208.0 cpu 96.0 used, 807768.0 memory 98304.0 used, 44052112.0 disk 98304.0 used, 24.0 active tasks
  2016/11/02 02:25:15.301 mesos_scheduler INFO 208.0 cpu 94.0 used, 807768.0 memory 96256.0 used, 44052112.0 disk 96256.0 used, 23.0 active tasks
  2016/11/02 02:25:15.803 mesos_scheduler INFO 208.0 cpu 92.0 used, 807768.0 memory 94208.0 used, 44052112.0 disk 94208.0 used, 23.0 active tasks
  2016/11/02 02:25:16.728 mesos_scheduler INFO 208.0 cpu 90.0 used, 807768.0 memory 92160.0 used, 44052112.0 disk 92160.0 used, 22.0 active tasks
  2016/11/02 02:25:17.229 mesos_scheduler INFO 208.0 cpu 88.0 used, 807768.0 memory 90112.0 used, 44052112.0 disk 90112.0 used, 22.0 active tasks
  </code></pre>
  
  <p>The code I wrote to specify the number of cores are as follows</p>
  
  <pre><code> cpus = executor.resources.add()
   cpus.name = "cpus"
   cpus.type = mesos_pb2.Value.SCALAR
   cpus.scalar.value =2
  </code></pre>
  
  <p>Do I use the api correctly?</p>