Efficient programming is all about knowing how to use CPU features and memory to your advantage. If you don't already know C, I suggest "Learn C the Hard Way"[0]. After that, here's two great places to start: "What Every Programmer Should Know About Memory"[1] and "What's new in CPUs since the 80s and how does it affect programmers?"[2]

[0]: https://learncodethehardway.org/c/

[1]: https://people.freebsd.org/~lstewart/articles/cpumemory.pdf

[2]: https://danluu.com/new-cpu-features/