The optimise the hot part strategy, applied repeatedly across different test cases, stamps down the spikes on the profiler until the profile is basically flat.

The optimise the hot part strategy, applied repeatedly across different test cases, stamps down the spikes on the profiler until the profile is basically flat. Sadly at that point rather more thought is needed and it seems to get a bit domain specific what needs to change next. A corollary of this that bad architecture choices made up front, e.g. because performance was not considered, become both extremely entrenched and difficult to see on the flat flame graph.