Brian Hanson 7a1e157c9c perf: gate hot /dev/shm writes on change — controlsd 69%→28% CPU ...

py-spy showed per-cycle atomic param writes were the dominant cost. Each
put() is mkstemp+fsync+flock+rename+fsync_dir — fine when rare, ruinous at
100Hz. At park with no state changes, these writes were running anyway and
the flock contention was poisoning the whole system.

carstate.py (update + update_canfd): CarSpeedLimit, CarIsMetric,
  CarCruiseDisplayActual were written every CAN update. Now cached and
  written only on change.
controlsd.py: same fix for LatRequested and no_lat_lane_change. Also
  throttle the sentry crash-file stat() from 100Hz to 1Hz.

Also: suppress locationdTemporaryError/paramsdTemporaryError/posenetInvalid
on lat engage (same 2s window as commIssue), and tie suppression to the
LatRequested edge instead of CC.latActive (fires immediately, not after
the 250ms ramp-up delay).

Also: reset Ratekeeper when it falls >1s behind — the ~6s fingerprinting
stall at startup was poisoning the lag metric for the entire session.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2026-04-16 17:34:07 -05:00

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