Question

When coding performance-critical portions of code (not necessarily large, but code that gets executed a lot), what topics should I be aware of/take into account.

I'm already fairly familiar with caching, aliasing, branching, cost of arithmetic operations, loop unrolling (and I guess some others that don't come to mind).

What else should I know? (not necessarily looking for details, just concepts I can look up on my own)

Answer 1

I think when it comes to performance, being familiar with the compiler optimization strategies and methods is essential. What this helps you with is that when you understand what kind of optimizations the compiler is capable of doing and under which circumstances, you actually can offload the performance tuning to the compiler(as you should anyway, if possible) by making sure that you give it the maximum possible opportunity to optimize the code.

Of course being familiar with tools which assist you with profiling and benchmarking your code/implementations is an essential. Infact, there's no point in optimizing unless you can measure the benefit. In the end this boils down to being able to reason between multiple implementations and what and why the performance differs at the lowest level possible - without this understanding it is very hard to come up with valid optimizing opportunities which you can reason about.

As the bottom line I would argue that being familiar with the compiler and it's optimizing capabilities and opportunities as well as being familiar with tools to measure benefits and spot bottlenecks as well as understanding the CPU's capabilities and instruction set are the three most important things for any programmer when it comes to writing performant native code. Yes, this is very general but as such it's also very applicable. Everything boils down to this in the end.