title: What happens under the hood when you specify more partitions than the number of cores available?
body: <p>For example, my laptop has 8 cores and if I submit:</p>
  
  <p><code>sc.parallelize(1 to 100, 30).count</code></p>
  
  <p>Does it execute 8 tasks first then the other 22 tasks is executed one by one when a core becomes available?</p>
  
  <p>Is there a way to verify what happens under the hood myself via the SparkUI or logs?</p>