[fasterik]

As always: use standard libraries first, profile, then write your own if the data indicate that it's necessary. To your point, the standard library probably already uses the OS primitives under the hood, which themselves do a short userspace spin-wait and then fall back to a kernel wait queue on contention. If low latency is a priority, the latter might be unacceptable.

The following is an interesting talk where the author used a custom spinlock to significantly speed up a real-time physics solver.

Dennis Gustafsson – Parallelizing the physics solver – BSC 2025 https://www.youtube.com/watch?v=Kvsvd67XUKw

[Lectem]

> which themselves do a short userspace spin-wait and then fall back to a kernel wait queue on contention.

Yes, but sadly not all implementations... The point remains that you should prefer OS primitives when you can, profile first, reduce contention, and then only, maybe, if you reeeally know what you're doing, on a system you mostly know and control, then perhaps you may start doing it yourself. And if you do, the fallback under contention must be the OS primitive