I assumed they would spin for only a short period of time only then fallback to a real lock. This is usually done to avoid blocking the thread before the end o

I assumed they would spin for only a short period of time only then fallback to a real lock. This is usually done to avoid blocking the thread before the end of it's time slice if there is a chance the lock would become available. If instead they implement a pure spin loop with sleep I can see why it does not perform well.