Sure, you don't really need to know any of this stuff unless you're actually needing to optimize code beyond the lowest hanging fruit. My list presupposes you'

Sure, you don't really need to know any of this stuff unless you're actually needing to optimize code beyond the lowest hanging fruit. My list presupposes you've hit a wall and need the best performance you can get. That's not always the case, but I certainly wouldn't say that these optimizations don't make a difference in the "real world of softare." False sharing alone can be the difference between a 16x parallelization speedup and a 1000x+ slowdown over the naive serial algorithm. 16x can be the difference between actionable results tomorrow or three weeks from today... and if you didn't know about it, the 1000x+ slowdown would be otherwise inscrutable.