Avoid acquiring lock and notify if no worker is parking - #1591
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Master's mmtk#1591 replaces the branch's lock-free wake-up fast path with its own: `WorkerParker` moves out of `WorkerMonitorSync` and `parked_workers` becomes an `AtomicUsize`, so `notify_work_available` can test it without taking the monitor lock. That supersedes this branch's `sleeping` counter, which existed only to be that lock-free reading and was strictly narrower -- `sleeping <= parked_workers` always, since a worker increments it only after `inc_parked_workers`. Master's counter is the more conservative test (it also counts the last parked worker while it runs `on_last_parked`), so it can cost an occasional redundant lock acquisition but cannot miss a wake-up. Dropped with it, both now judged not to earn their divergence: - `inactive_waiters`, and the `notify_inactive_while_locked` gate it fed. It only suppressed a `notify_all` on `active_worker_number_changed` when no worker was waiting there -- one no-op FUTEX_WAKE per bucket boundary, which is noise against a pause. The extra call it added to `wake_n_while_locked` was not load-bearing either: `set_active_workers` documents that its caller must follow with `notify_work_available(true)`, so a reactivation always arrives as `WakeAll`, never as `Wake(n)`. - `wake_all_override` (`MMTK_WAKE_ALL`), which existed to measure what the targeted wake-ups were worth. mmtk#1589 settled that. worker_monitor.rs is now byte-identical to master. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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This PR moves
WorkerParkeroutside ofWorkerMonitorSync. The main goal is to accessparked_workersas an atomic without the lock. This allows us to avoid acquiring the lock and waking up all workers innotify_work_available-- which almost happens for every newly added work packet.