Comment by newpavlov

>If you're not doing things better than threads then why don't you just use threads?

Because green threads are more efficient than the classical threads. You have less context switching, more control over concurrency (e.g. you can have application-level pseudo critical section and tools like `join!`/`select!`), and with io-uring you have a much smaller number of syscalls.

In other words, memory footprint would be similar to the classical threads, but runtime performance can be much higher.

>So you only allow join/select at the task level? Sounds awful!

What is the difference with join/select at the future level?

Yes, with the most straightforward implementation you have to allocate full stack for each sub-task (somewhat equivalent to boxing sub-futures). But it's theoretically possible to use the parent task stack for sub-task stacks with the aforementioned compiler improvements.

Another difference is that instead of just dropping the future state on the floor you have to explicitly send a cancellation signal (e.g. based on `IORING_OP_ASYNC_CANCEL`) and wait for the sub-task to finish. Performance-wise it should have minimal difference when compared against the hypothetical async Drop.

>Yes, exactly.

Ok, I have nothing more to add then.