1. A computing system comprising: at least one processor; and at least one module operable by the at least one processor to: calculate a tail of a first dataset, wherein calculating the tail of the first dataset includes determining elements of the first dataset that fall outside of a specified percentile; determine locations of the first dataset at which the elements of the first dataset that fall outside of the specified percentile are located; calculate a tail of a second dataset, wherein calculating the tail of the second dataset includes: populating a data structure with elements of the second dataset that are located at locations of the second dataset that correspond to the locations of the first dataset, and determining, using the data structure, elements of the second dataset that fall outside of the specified percentile; and output an indication of at least one of the tail of the first dataset or the tail of the second dataset.