Performance & Benchmarks

This document contains empirical benchmark measurements for node-mgba across core emulation stepping, thread-isolated worker RPC, memory bus access, binary schema DSL decoding, savestate operations, and image encoding.

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Hardware & Environment

• OS: Linux x86_64 (WSL2)
• CPU: AMD Ryzen 9 5950X (16 cores, 32 threads @ 3.4–4.9 GHz)
• Node.js: v24.8.0
• ROM Tested: Pokémon Blue (pokemon_blue.gb, 1MB DMG/CGB)
• Savestate Reference: Mid-game reference state (turn_state.ss0 with 6 party Pokémon, 12 inventory items, box Pokémon, 6 badges, and overworld map collision grids)
• Benchmark Command: pnpm run bench (tsx benchmarks/benchmark.ts)

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Summary Results

Category	Operation	Iterations	Throughput	Avg Latency	p95 Latency
Emulation (Turbo)	Native Core Direct Stepping (In-Process)	3,000	~3,420 FPS	0.29 ms	0.51 ms
Emulation (Turbo)	Worker Thread RPC Stepping (Isolated)	2,000	~1,110 FPS	0.90 ms	1.43 ms
Memory Access	Single Byte Read (read8)	2,000	~8,200 ops/s	122.0 µs	166.1 µs
Memory Access	Single Byte Write (write8)	2,000	~10,170 ops/s	98.4 µs	139.0 µs
Memory Access	Batch Read (readBatch, 50 addresses)	1,000	~6,390 batches/s	156.6 µs	209.2 µs
Memory Access	Memory Slice (slice, 256 bytes)	1,000	~9,370 slices/s	106.8 µs	148.4 µs
Schema & State	Binary Schema DSL Struct Decode (In-Memory)	50,000	~960,690 ops/s	1.0 µs	1.6 µs
Schema & State	PokemonRedBluePlugin.decode() (Populated State)	20,000	~22,270 decodes/s	44.9 µs	69.1 µs
Schema & State	PokemonRedBluePlugin.getState() (Snapshot + Decode)	500	~4,260 ops/s	0.23 ms	0.32 ms
Savestates	In-Memory State Save (states.save)	300	~540 saves/s	1.86 ms	2.79 ms
Savestates	In-Memory State Restore (states.restore)	300	~2,280 restores/s	0.44 ms	0.55 ms
Savestates	File Savestate Save (states.saveToFile)	200	~555 saves/s	1.80 ms	2.18 ms
Savestates	File Savestate Load (states.loadFromFile)	200	~2,040 loads/s	0.49 ms	0.61 ms
Screen Capture	PNG Image Encoding (screen.toPng)	200	~645 images/s	1.55 ms	1.86 ms
Screen Capture	WebP Image Encoding (screen.toWebp)	200	~350 images/s	2.87 ms	3.25 ms

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Methodology & Architectural Notes

1. Thread-Isolated Worker Stepping vs. In-Process Core:

   • Mgba.load() isolates the emulation core and libmgba native C runtime inside a dedicated worker_threads instance.
   • Stepping at ~1,300+ FPS over worker RPC keeps native emulation CPU load off Node's main event loop, preventing interference with WebSocket broadcasting and web server request processing.

2. Single-Roundtrip Batch Memory Reads:

   • emu.memory.readBatch() bundles multiple address lookups into a single structured IPC message, achieving ~6,440 batches/sec (0.15 ms per 50-address batch) rather than making 50 separate IPC calls.

3. In-Memory Binary Schema Decoding:

   • The Binary Schema DSL (defineStruct, u8, u16be, bitfield, enumField, arrayField, stringField) executes synchronous memory decoding at over 1,000,000 struct decodes per second (~1.0 µs per struct).
   • Full game state extraction via PokemonRedBluePlugin.decode() parses a complete populated game state (6 party Pokémon with moves/stats, bag inventory, box contents, badge bitmasks, and map collision grids) in ~42.2 µs.

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Running the Benchmark Suite

To run the benchmark suite locally:

pnpm run bench