why zeppelin SparkInterpreter use FIFOScheduler

[linxi zeng]

hi, Moon:
   I notice that the getScheduler function in the SparkInterpreter.java
return a FIFOScheduler which makes the spark interpreter run spark job one
by one. It's not a good experience when couple of users do some work on
zeppelin at the same time, because they have to wait for each other.
And at the same time, SparkSqlInterpreter can chose what scheduler to use
by "zeppelin.spark.concurrentSQL".
My question is, what kind of consideration do you based on to make such a
decision?