Spark Streaming optimization: spark.default.parallelism adjust processing parallelism

This is what the authorities say:

Cluster resources can be under-utilized if the number of parallel tasks used on any stage of the computation are not high E Nough. For example, for distributed reduce operations like Reducebykey and Reducebykeyandwindow, the default number of parallel t Asks is controlled by the Thespark.default.parallelism configuration property. You can pass the level of parallelism as a argument (see pairdstreamfunctions documentation), or set the SPARK.DEFAULT.PA Rallelism the default.

My ideal: Is that you can adjust the spark.default.parallelism to modify the default degree of parallelism, or pass in the parallelism directly to the method when using the Transformation,action method.

Spark Streaming optimization: spark.default.parallelism adjust processing parallelism