From a tiny observation at work about odd behaviors of spinlocks I spent months trying to find good benchmarks, (still not entirely successful) writing my own spinlocks, mutexes and condition variables and even contributing a patch to the Linux kernel. The main thing I’ll try to answer is to give some more informed guidance on the endless discussion of mutex vs spinlock. Besides that I found that most mutex implementations are really good, that most spinlock implementations are pretty bad, and that the Linux scheduler is OK but far from ideal.