[temac]

As far as I know Win NT threads are 1:1.

Not even sure how it would work or even make any sense to have N:M handled by the kernel. N:M is usually a mainly a userspace thing. And Windows is even less likely to use that kind of convolution, because IIRC it can call back from kernel to userspace (that design I would not recommend, btw, but oh well). You have fibers, of course, but that's a different thing.

Windows does not scale probably simply because the kernel is full of "big" locks (at least not small enough...) everywhere, and they have far less fancy structures and algo than Linux (is there any equivalent of RCU that is widely used in there? - not sure). Cf the classic posts of the builder of Chrome who every now and then encounter a ridiculous slowdown of his builds on moderately big computers, sometimes because of mutexes badly placed.

[0x8BADF00D]

> Not even sure how it would work or even make any sense to have N:M handled by the kernel. N:M is usually a mainly a userspace thing.

Correct, I meant that the benchmarking program itself probably used that implementation. Not the Win NT kernel’s implementation of OS threads.