The Windows host could tank a local game's 1% lows — mint retries broadcast PnP device changes at the whole box, and session tuning never reverted
#185
Merged
enricobuehlermerged 2 commits from worktree-audio-stutter-fixes into main2026-08-12 22:03:51 +00:00
Field report (2026-08-12): Punktfunk's audio devices tank Helldivers 2 to
1% lows of 2-5 FPS; uninstalling restores performance. Two host-side
mechanisms can plausibly do that, both fixed here.
The mint retry storm: minted::ensure_blocking() ran a FULL provisioning
pass on every mic-pump open with no cooldown, no in-flight guard, and no
give-up - and ensure_role() reached UpdateDriverForPlugAndPlayDevicesW
even when the devnode already existed. On a box where minting never
latches, the pump's reopen backoff (capped 60 s) turned that into a PnP
driver rebind + system-wide device-change broadcast roughly once a
minute, forever - and games rebuild their audio graph on each broadcast.
Now:
* ensure_role() gets a steady-state fast path: a marker devnode whose
endpoints are all live resolves without touching PnP or the
default-device policy.
* ensure_blocking() waits on an in-flight pass instead of racing a
second SetupAPI sweep against it (the dead-mic-air deploy race),
honours RETRY_COOLDOWN after a failed pass (first-ever resolve still
blocks, per the cold-boot mint contract), and
* five unlatched passes stop minting for the host lifetime (a service
restart re-arms) - counted across the worker and the blocking path.
The never-reverted session tuning: pf-frame's tune_process_once() put
the whole host at HIGH_PRIORITY_CLASS with timeBeginPeriod(1) and DWM
MMCSS on the first hot stream thread and documented 'reverts at process
exit' - but the host is a 24/7 service, so after one stream it competed
at HIGH class with a 1 ms global timer against whatever the user played
locally, forever. The process-wide tuning is now refcounted across the
hot threads via a TLS guard: the first hot thread applies it, the last
one's exit reverts it (timeEndPeriod, DwmEnableMMCSS(0), NORMAL class) -
the same thread-exit lifetime the MMCSS and execution-state effects
already ride. Every on_hot_thread() call site is a session-scoped
thread (capture/encode, packetizer, send, NVENC retrieve), so the
revert lands at session teardown.
enricobuehler