[SPARK-1953][YARN]yarn client mode Application Master memory size is same as driver memory...

... size

Ways to set Application Master's memory on yarn-client mode:
1.  `spark.yarn.am.memory` in SparkConf or System Properties
2.  default value 512m

Note: this arguments is only available in yarn-client mode.


I don't think this is correct. Just to confirm my understanding: In cluster mode, the AM and the driver are in the same JVM, so we ignore `spark.yarn.am.memoryOverhead`. In this case, `userClass` should not be null, which is this else case here. Right?