Where do you start to tune the above mentioned params. Do we start with executor memory and get number of executors, or we start with cores and get the executor number. I followed the [link](http://blog.cloudera.com/blog/2015/03/how-to-tune-your-apache-spark-jobs-part-2/). However got a high level idea, but still not sure how or where to start and arrive to a final conclusion.