title: Spark Executors & Tasks
body: <p>In Spark, an executor may run many tasks concurrently maybe 2 or 5 or 6 . </p>
  
  <p>How Spark figures out (or calculate) the number of tasks to be run in the same executor concurrently i.e how many tasks can run in an executor concurrently? </p>
  
  <p>An executor may be executing one task but one more task maybe be placed to run concurrently on same executor? What's the criteria for that? </p>
  
  <p>An executor is assigned a fixed number of cores &amp; memory. As we do not specify memory &amp; cores requirements for task in Spark, how to calculate how many can run concurrently in an executor?</p>