> This is true for readiness-based IO (which, admittedly, most current async IO loops are using) Right, so if most async I/O frameworks use readiness-based IO

> This is true for readiness-based IO (which, admittedly, most current async IO loops are using) Right, so if most async I/O frameworks use readiness-based IO (epoll, kqueue), then the context switch overhead is similar. So then most of the performance arguments for async I/O don't stand. That's where I'm confused :)