In hadoop MR, there is an option *mapred.reduce.slowstart.completed.maps* which can be used to start reducer stage when X% mappers are completed. By doing this, the data shuffling process is able to parallel with the map process.
In a large multi-tenancy cluster, this option is usually tuned off. But, in some cases, turn on the option could accelerate some high priority jobs. Will spark provide similar option?
