Yes and no, I think that what can happen if you only focus on "performance critical code" is the rest of your code is slow and incredibly unfriendly to cache, b

Yes and no, I think that what can happen if you only focus on "performance critical code" is the rest of your code is slow and incredibly unfriendly to cache, but there's absolutely nothing you can really do about it past a point. Like, if all your code is 5x slower than it possibly could be, then even after you fix the performance critical bits you have this ugly tax everywhere else that you can't do anything about other than a rewrite. And I do think that matters, look at various projects written in a language like python where bits have been written in C, but you still have all this slow interpreted stuff. (I like Python btw, I'm just making a point that if performance matters it doesn't just matter in loops)