Well-illustrated, and well-illustrated, gems:

C++ for Games: Performance, Allocations and Data Locality

by Sergey Ignatchenko

From the draft chapter:

One further thing to keep in mind with regards to 90-10 (or 70-30) rule is that even if only performance of 10% of the code matters, the rest of the code can still affect performance of critical 10% in a Pretty Bad Way :-( ...