title: How to set Spark executor memory?
body: <p>I have set <strong>spark.executor.memory</strong> to <strong>2048m</strong>, and in the UI "Environment" page, I can see this value has been set correctly. But in the "Executors" page, I saw there's only 1 executor and its memory is <strong>265.4MB</strong>. Very strange value. why not 256MB, or just as what I set?</p>
  
  <p>What am I missing here?</p>