A pool of systhreads, to avoid the overhead of creating a new thread for each operation.
val create : sleep_q:Eio_utils.Zzz.t -> tcreate ~sleep_q is a new thread pool.
sleep_q is used to register a clean-up task to finish idle threads.
val run : t -> (unit -> 'a) -> 'arun t fn runs fn () and then marks t as closed, releasing all idle threads.
val submit :
t ->
ctx:Eio.Private.Fiber_context.t ->
enqueue:(('a, Eio.Exn.with_bt) result -> unit) ->
(unit -> 'a) ->
unitsubmit t ~ctx ~enqueue fn starts running fn in a sys-thread, which uses enqueue to return the result.
If ctx is already cancelled then the error is passed to enqueue immediately. Systhreads do not respond to cancellation once running.