In many contexts, the problem is not the absolute performance, but the variation in performance. For example, we want the Opus codec to be relatively insensitive to timing analysis, since Opus audio is often encrypted and transmitted over a network. Large variations represent an information leak that could be exploited by an external observer.

When we started looking at actual timings, we found that it was mostly pretty consistent, except for huge slowdowns in some frames. The cause? glibc's exp() slow path.