1. A computer implemented method of dynamically instrumenting a computer program to detect that plural data fetches comprise a prefix of data fetches in a given stream of data fetches, and to prefetch a suffix of data fetches in the stream, the method comprising: creating instructions that detect when the prefix of elements in the stream have been fetched by the computer program; creating instructions that prefetch elements in a suffix of the stream when the prefix is detected; and instrumenting the computer program with the created instruction.