Final Log Optimization for Performance

Summary

The emulator worked correctly with classic Tetris, but at only 13 FPS due to log saturation on the console. All diagnostic logs that were running thousands of times per second (DMA, interrupts, STAT, MBC, etc.) were identified and commented on, allowing the emulator to reach 60 FPS and be fully playable.

The logs discussed include: DMA transfers (START/COMPLETE), interrupt dispatch, MBC bank changes, STAT/LYC/TAC updates, and active STAT signals. All logs are maintained in the code as comments to facilitate future debugging when necessary.

Hardware Concept

In an emulator, theperformanceis critical to keeping the gaming experience smooth. The original Game Boy ran at approximately 59.7 FPS (70,224 cycles per frame), and a modern emulator should maintain this speed on current hardware.

The performance problem was not in the hardware emulation itself, but in thediagnostic instrumentationwhich was added during development. The logs oflogger.info()They execute thousands of times per second:

• DMA: Executed every time sprites are copied to OAM (several times per frame)
• Interruptions: Triggered multiple times per frame (V-Blank, STAT, Timer)
• STAT/LYC/TAC: Constantly updated during execution
• MBC: ROM bank changes during data loading

Every call tologger.info()It has a cost: string formatting, writing to the console, I/O synchronization. When this happens thousands of times per second, the emulator slows down drastically.

Solution:Comment out all frequent diagnostic logs, keeping them in the code to activate them when necessary for debugging. Critical logs (errors, warnings) remain active.

Implementation

All diagnostic logs that are frequently executed during normal emulator execution were systematically commented. Logs are maintained in the code as comments with the markCOMMENTED for performanceto facilitate its reactivation when necessary.

Modified components

• src/memory/mmu.py: Commented logs of DMA START/COMPLETE, STAT UPDATE, LYC SET, TAC UPDATE
• src/memory/cartridge.py: Commented MBC bank change log
• src/cpu/core.py: Commented INTERRUPT DISPATCHED logs (general and specific Timer)
• src/gpu/ppu.py: Annotated STAT SIGNAL ACTIVE logs (LYC Match, H-Blank, V-Blank, OAM Search), STAT interrupt triggered, and LYC written

Logging strategy

A tiered logging strategy is maintained:

• ERROR/WARNING: Always active (critical errors, unexpected conditions)
• INFO (frequent diagnosis): Commented for performance, can be reactivated when necessary
• DEBUGS: They were already commented or disabled by default

All commented logs include the mark# COMMENTED for performanceto facilitate its search and selective reactivation during debugging.

Affected Files

• src/memory/mmu.py- Commented DMA, STAT, LYC, TAC logs
• src/memory/cartridge.py- Commented MBC bank change log
• src/cpu/core.py- Commented interruption logs
• src/gpu/ppu.py- Commented STAT signals and LYC logs

Tests and Verification

The optimization was validated by running classic Tetris (user-contributed ROM, not distributed):

• ROM:Tetris (classic, 32KB, DMG) - User-contributed ROM, not distributed
• Execution mode:UI with Pygame, logging disabled
• Success Criterion:The emulator must reach a stable 60 FPS and be fully playable
• Observation:
  • Before optimization: 13.44 FPS (log saturation)
  • After optimization: 60 FPS stable
  • Visible and functional title screen
  • Responsive controls (piece movement)
  • No lag or stuttering
• Result: Verified- The emulator works perfectly at 60 FPS

Legal notes:The Tetris ROM is the property of Nintendo and is used solely for the author's local testing. It is not distributed or linked in the repository.

Sources consulted

• Python logging documentation:https://docs.python.org/3/library/logging.html
• Best performance practices in Python: Lazy formatting, logging levels

Note: This optimization is standard software development practice. Diagnostic logs are essential during development, but must be disabled in production to maintain performance.

Educational Integrity

Next Steps

• [ ] Check performance with Pokémon Red and Tetris DX (GBC/DMG hybrid games)
• [ ] Try complete gameplay of classic Tetris (move pieces, make lines, game over)
• [ ] If there are compatibility problems with hybrid games, investigate differences in STAT or JOYPAD register
• [ ] Consider implementing a conditional logging system for future debugging