This is interesting to me, because if I was given this problem, the way I would have done it would be to query the hardware counters at every function's start and end, by using the linker to wrap every function (presented here: https://gdcvault.com/play/1015727/Runtime-CPU-Performance-Spike-Detection). So I was interested to hear that Insomniac took a completely different approach. Review: 7/10 They said it took them 2 weeks of work, which seems like a good cost/benefit ratio. They also gave a couple examples of using it to improve real perf.