wmb vs mmiowb

[Linus Torvalds]

On Thu, 23 Aug 2007, Nick Piggin wrote:
> 
> Also, FWIW, there are some advantages of deferring the mmiowb thingy
> until the point of unlock.

And that is exactly what ppc64 does.

But you're missing a big point: for 99.9% of all hardware, mmiowb() is a 
total no-op. So when you talk about "advantages", you're not talking about 
any *real* advantage, are you?

			Linus