Interaction cost: for when event counts just don't add up

Most performance analysis tasks boil down to finding bottlenecks. In the context of this article, a bottleneck is any event (for example, branch mispredict, window stall, or arithmetic-logic unit (ALU) operation) that limits performance. Bottleneck analysis is critical to an architect's work, whether the goal is tuning processors for energy efficiency, improving the effectiveness of optimizations, or designing a more balanced processor. Interaction cost helps to improve processor performance and decrease power consumption by identifying when designers can choose among a set of optimizations and when it's necessary to perform them all