Function blocking_limit 

pub fn blocking_limit() -> usize

The blocking pool (docs/async.md): spawn_blocking runs a job on a worker thread and resolves on the awaiting side; std-only, so it lives in day-async and is re-exported here. How many threads the blocking pool may hold at once: the machine’s parallelism, at least four (a job waiting behind three slow ones still gets a thread), at most thirty-two. Zero on the web, where jobs run inline.