It is very unfortunate. On that project we looked at all sorts of ways to avoid burning cores but they all had significant latency issues. If it involved going

It is very unfortunate. On that project we looked at all sorts of ways to avoid burning cores but they all had significant latency issues. If it involved going to the kernel then there was a major context switch overhead. But the big killer is the non-constant time. Each time you go to the kernel there's a danger of loosing your timeslice or being shunted to some other core. This leads to very high variance in performance. (I must always repeat though, this variance is not likely relevant in most applications.) So we spun in loops. And we had the CPUs set to maximum performance (no idle-time scaling). The total real load was probably less than 1%, so yes, it's very unfortunate.