Rate Control Upgrade & Auto CPU Scaling #56
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Implements dynamic CPU frequency scaling that monitors audio buffer stress to automatically adjust between POWERSAVE/NORMAL/PERFORMANCE levels. Key features: - Uses rate control stress metric (0-1 normalized, buffer-size independent) - Window-based averaging with hysteresis (1s boost, 1.5s reduce) - Background thread applies changes without blocking emulation - Panic path for immediate boost on audio underruns - Startup grace period avoids false positives during buffer fill Added to minarch CPU Speed menu as "Auto" option (4th choice). Testing on Miyoo Mini shows correct behavior: - Demanding games (Punch-Out) stay at PERFORMANCE - Light games (Tetris) reduce appropriately - No audio glitches from frequency changes
The "Prevent Tearing" (vsync) and "Prioritize Audio" (threaded video) settings were workarounds for audio/video sync issues. With dynamic rate control implemented, these are obsolete - vsync should always be on, and rate control handles timing drift via audio resampling. - Remove thread_video, prevent_tearing variables and menu options - Remove coreThread() and all pthread synchronization code - Remove GFX_setVsync/PLAT_setVsync from API and all platforms - Set strict vsync at init on miyoomini (SDL2 platforms use renderer flag) - Clean up system.cfg and emulator config files
timing. Moving GFX_flip() outside the video callback allows the core to run at its natural rate instead of being throttled to display refresh rate. This fixes the audio production deficit that required aggressive rate control (d=2%) and enables accurate CPU performance measurement.
When vsync throttles the main loop to display rate instead of core rate, audio production falls short of consumption causing buffer drift and underruns. Implements display rate correction (display_fps / core_fps) applied to resampler ratio_adjust, compensating for structural timing mismatch. Also separates rate control parameter (0.5%) from resampler safety clamp (5%), extracts display measurement to measureDisplayRate() with stability detection, and removes unused SND_getRateControlStress().
Auto CPU mode now detects available frequencies from sysfs and scales through all steps instead of just 3 fixed levels. Includes conservative step-down limits (max 2 at once), 75% predicted utilization safety margin, and 8-window panic cooldown to prevent oscillation on platforms with sparse frequency tables.
- Renamed MENU → IDLE (20% of max, for tools/utilities) - Updated all platforms to 20/55/80/100% frequency distribution - Launcher now uses POWERSAVE instead of IDLE for responsiveness - Changed default CPU mode from Normal to Auto - Removed all per-core CPU overrides (Auto handles everything)
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Pull request overview
This PR implements comprehensive rate control upgrades and auto CPU scaling for LessUI. It replaces the old VSync/threading system with always-on VSync + dynamic rate control, adds automatic CPU frequency scaling based on frame timing, and introduces granular frequency control using all available CPU frequencies detected from the system.
Key changes:
- Auto CPU scaling with frame timing-based monitoring and granular frequency control
- Unified rate measurement system (RateMeter) for display and audio with dual clock correction
- VSync always-on approach with threading removal, decoupling flip from core.run()
Reviewed changes
Copilot reviewed 74 out of 75 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| Platform files (zero28, tg5040, rgb30, etc.) | CPU speed enum renamed (MENU→IDLE), frequency values updated, new frequency detection/setting functions |
| minarch.c | Auto CPU scaling implementation, threading removal, VSync decoupling, rate measurement integration |
| api.c/api.h | Rate meter integration, dual correction, adaptive d parameter, CPU frequency sysfs helpers |
| rate_meter.c/h | New unified rate measurement module with stability detection |
| audio_resampler.c/h | Safety clamp increase (1%→5%), diagnostics tracking |
| utils.c/h | Percentile calculation functions for frame timing analysis |
| Config files | VSync/threading options removed, CPU speed defaults updated |
| Documentation | Comprehensive docs for auto CPU scaling and audio rate control |
| Tests | New rate_meter unit tests |
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So much.... Really nice upgrade across the board!