It sounds like you might be arguing the relative merits of preemptive multitasking in some generic case rather than the specific domain tokio operates in. Toki

It sounds like you might be arguing the relative merits of preemptive multitasking in some generic case rather than the specific domain tokio operates in. Tokio is a lot about IO. The resources the scheduler is waiting for will almost exclusively be network and file operations. There is a risk that a task does some long running CPU work on the back of a future or uses sync network/file operations. Maybe a preemptive scheduler could help then, but I'm not convinced by your argument that tokio needs to optimize for this.