[ASK] what is the purpose of sleep?

Hi, I'm trying to understand how the runtime works,
can anyone explain to me what is the purpose of sleep 10 ms in
https://github.com/async-rs/async-std/blob/fc4e4725992b1b147a4a286cea5d094c5263b951/src/rt/runtime.rs#L247-L250
and
https://github.com/async-rs/async-std/blob/fc4e4725992b1b147a4a286cea5d094c5263b951/src/rt/runtime.rs#L263-L266

why not just blocking on reactor instead of blocking on sleep,
does that mean that short blocking on sleep is more efficient than short blocking on reactor? like, we let the reactor to capture multiple io event, analogous to buffering when reading data, instead of byte by byte, we go block by block

Read src/rt/runtime.rs at lines 247-250 and 263-266, then trace the referenced reactor and sleep entry points. Compare what each wait does and document the purpose of the 10 ms sleeps, including why the runtime uses them instead of blocking directly on the reactor.

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