I always thought tokio, for rust, is implemented with OS native poll fd for async io:

• epoll for linux
• kqueue for mac
• legacy select for windows, or iocp
• legacy select/poll for other unix

Because in c/c++ this is very basic for a multi-threaded, non-blocking framework, such as libevent, libuv, asio, etc.

Until I read this part: tokio::fs - Rust

"Be aware that most operating systems do not provide asynchronous file system APIs. Because of that, Tokio will use ordinary blocking file operations behind the scenes. This is done using the spawn_blocking threadpool to run them in the background."

So file io is actually blocking io + thread pool? Did I mis-understood something?

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