Consider making Windows use threadpools

[gdamore]

Thread Pools offer some attractive benefits over raw I/O completion ports, including a simpler programming model and better automatic scaling. We might be able to use these to handle taskq type tasks too!

[gdamore]

This may be required for some kinds of Windows applications. Apparently at least Windows Store 8.1 apps are not permitted to use _beginthreadex....

[gdamore]

I have some mixed data here. Apparently threadpoolio is "new", with almost non-existent documentation and examples. Worse, the I/O threadpools seem to assume that you only really want one outstanding operation on a file handle at a time, which seems (to my mind) to make them less scalable than the underlying IOCP. They are also implemented on top of IOCP, so adding a layer of indirection is unlikely to yield better performance.

I'm shelving this for now. If we need something for Windows Store 8.1 apps, we'll revisit.

[gdamore]

Closing this -- we're not going to do it for the reasons given above.