Comment by conradludgate

Expanding on this. If you have a lot of concurrent tasks, you will overflow[0] the task local queue and be bottlenecked by the global queue mutex[1]

[0]: https://github.com/tokio-rs/tokio/blob/8897885425bf3d89053f8... [1]: https://github.com/tokio-rs/tokio/blob/8897885425bf3d89053f8...