goroutine vs tokio
February 16, 2022
Go uses a different strategy for blocking systemcalls. It does not run them on a threadpool - it moves all the other goroutines that are queued to run on the current thread to a new worker thread, then runs the blocking systemcall on the current thread. This minimizes context switching.
You can do this in tokio as well, using task::block_in_place. If I change your code to use that instead of tokio::fs, it gets a lot closer to the go numbers. Note that using block_in_place is not without caveats, and it only works on the multi-threaded runtime, not the single-threaded one. That’s why it’s not used in the implementation of tokio::fs.
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