Phase 6 Performance Optimization Results

Summary

Phase 6 implemented virtual threads for parallel thumbnail loading in JPhotoTagger. The benchmarks demonstrate significant improvements in folder loading performance through parallel I/O operations.

Virtual Threads Performance (NEW)

The key optimization in Phase 6 was introducing Java 21 virtual threads for parallel thumbnail fetching. This is a new benchmark that measures folder loading with concurrent thumbnail operations.

Files Cold Cache (Sequential) Virtual Threads (Parallel) Speedup
10 1633.92 ms 243.71 ms 6.7x faster
50 8003.89 ms 931.42 ms 8.6x faster
100 16818.98 ms 1827.47 ms 9.2x faster

The virtual threads implementation shows excellent scalability - the speedup increases with file count because more I/O operations can be parallelized.

Cold Cache Comparison (Pre vs Post Phase 6)

Files Pre-Phase 6 Post-Phase 6 Change
10 1674.22 ms 1633.92 ms -2.4% (faster)
50 8337.94 ms 8003.89 ms -4.0% (faster)
100 16694.34 ms 16818.98 ms +0.7% (within variance)

The cold cache performance remains similar, which is expected since this benchmark measures sequential loading without the new virtual thread optimization.

Warm Cache Performance

Files Pre-Phase 6 Post-Phase 6 Change
10 7.59 ms 7.66 ms +0.9% (within variance)
50 37.67 ms 40.11 ms +6.5% (within variance)
100 74.95 ms 72.88 ms -2.8% (faster)

Warm cache performance is stable, as expected since thumbnails are already cached.

Startup Benchmark

Phase Pre-Phase 6 Post-Phase 6 Change
Class Loading 15.21 ms 15.02 ms -1.3%
JAXB Init 290.79 ms 312.64 ms +7.5%
ImageIO Init 29.09 ms 27.96 ms -3.9%
Total 335.10 ms 355.62 ms +6.1%

Startup time shows slight variance between runs. CDS (Class Data Sharing) was configured but requires the CDS archive to be generated and used at runtime for actual improvements.

Database Benchmarks

Benchmark Pre-Phase 6 Post-Phase 6 Change
insertKeyword 7.91 us/op 8.08 us/op +2.2%
keywordExists 68.51 us/op 72.19 us/op +5.4%
selectAllKeywords 92.77 us/op 92.67 us/op -0.1%
selectChildKeywords 62.73 us/op 63.83 us/op +1.8%
selectRootKeywords 49.29 us/op 50.47 us/op +2.4%

Database benchmarks show stable performance within normal variance.

Thumbnail Cache Benchmarks

Benchmark Pre-Phase 6 Post-Phase 6 Change
cacheExists_single 274.64 us/op 266.23 us/op -3.1% (faster)
cacheHit_concurrent 1831.83 us/op 1832.14 us/op 0%
cacheHit_single 519.03 us/op 519.92 us/op +0.2%
cacheUpToDate_single 279.02 us/op 282.40 us/op +1.2%

Cache performance remains stable.

Conclusion

Phase 6 successfully achieved its primary goal of significantly improving folder loading performance through virtual threads:

Optimizations Implemented

  1. Virtual Thread Thumbnail Fetcher - Parallel thumbnail loading using Java 21 virtual threads
  2. Database Indexes - Optimized indexes for common query patterns
  3. WAL Mode - SQLite Write-Ahead Logging for better concurrency
  4. ZGC Launch Scripts - Low-latency garbage collector configuration
  5. CDS Archive Generation - Class Data Sharing for faster startup (requires archive usage)

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