[lowbloodsugar]

TFA makes the point that modern "mutex" implementations actually use spinlocks first and only fall back to heavy, kernel Mutexes if there is contention. So the title is click-baity. Mutexes are slower than spinlocks. The "faster than spinlocks" mutexes in this article are actually spinlocks that fallback to mutexes.

Then the benchmark uses spinlocks in situations that spinlocks aren't great for. And, surprise, spinlocks are slower, than spinlocks-with-mutexes.

Spinlocks are great in situations such as:

  * There are far more resources than threads,
  * The probability of actually having to spin is small,
    ideally if the time spent in the lock is a few instructions
  * When you can't use optimistic concurrency*

* because perhaps the number of memory locations to track is too complicated for my poor brain and I can't be arsed to remember how TLA+ works

There's plenty of linked list implementations, for example, that use optimistic concurrency. At that point you've got yourself a thread-safe message queue and that might be better than mutexes, too.