The type of backoff value

create ~max:maxv () returns a backoff value, which when waited upon, suspends the calling domain for x milliseconds, where x is the current value of the backoff. The backoff value x is doubled after every wait upto a maximum of maxv milliseconds. The default maximum is 32 milliseconds. The initial backoff is 1 millisecond.

once b suspends the current domain for x milliseconds, where x is the current value of the backoff.

Resets the backoff clock to 1 millisecond.