SpinWait vs Sleep waiting. Which one to use?

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In .NET 4 SpinWait performs CPU-intensive spinning for 10 iterations before yielding. But it does not return to the caller immediately after each of those cycles; instead, it calls Thread.SpinWait to spin via the CLR (essentially the OS) for a set time period. This time period is initially a few tens of nano-seconds but doubles with each iteration until the 10 iterations are complete. This enables clarity/predictability in the total time spent spinning (CPU-intensive) phase, which the system can tune according to conditions (number of cores etc.). If SpinWait remains in the spin-yielding phase for too long it will periodically sleep to allow other threads to proceed (see J. Albahari’s blog for more information). This process is guaranteed to keep a core busy…

So, SpinWait limits the CPU-intensive spinning to a set number of iterations, after which it yields its time slice on every spin (by actually calling Thread.Yield and Thread.Sleep), lowering its resource consumption. It will also detect if the user is running a single core machine and yield on every cycle if that is the case.

With Thread.Sleep the thread is blocked. But this process will not be as expensive as the above in terms of CPU.

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