1. A method for processing a stream of tuples, comprising: receiving a stream of tuples to be processed by a plurality of processing elements operating on one or more computer processors; generating a model of performance for processing the stream of tuples at runtime, wherein one or more tuples from the stream of tuples potentially cause adverse performance; predicting a parameter for a tuple from the stream of tuples, the parameter indicating a potential for adverse performance, the predicting including using the model; and modifying processing of the tuple if the parameter falls outside a threshold.