On: Mutexes are faster than Spinlocks

[Diggsey]

Actually, the parking_lot mutex is fair: https://docs.rs/parking_lot/0.10.0/parking_lot/type.Mutex.ht...

The high waiting variance is because the benchmark randomly decides which locks to take, meaning that the amount of contention is variable.

[sanxiyn → Diggsey]

Note that fair locking is still expensive. parking_lot achieves both speed and fairness by starting with unfair locking and falling back to fair locking.

[matklad → Diggsey]

Benchmark uses fixed seeds, there’s no inherent randomness.