A scheduler's end of the pool.
Fields
- allocator: Allocator
- mutex: Thread.Mutex
- done_head: *Op
- done_tail: *Op
- inflight: s64
- Operations handed to workers whose completion the scheduler has not taken yet.
- wake_fd: s64
- epoll: the eventfd, and the internal READ that waits for it.
- wake_op: *Op
- wake_buffer: [8] u8
- queue_fd: s64
- kqueue: the descriptor to trigger.