> every way of doing concurrency other than kernel threads has come and gone out of fashion (think Scala actors and Goroutines, two very admirable features). I

> every way of doing concurrency other than kernel threads has come and gone out of fashion (think Scala actors and Goroutines, two very admirable features). I'd say the fact that these examples are around show that NxM, green-over-kernel threading works and works well. It made it through the crucible of fashion and is now a "good" way. Much like GC did. So I'd say your claim that kernel threads are it is misplaced... unless you just consider NxM threads to be kernel threads w/ some sugar?