Benchmarks

Performance measurements for nori-sstable operations.

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Test Environment

Hardware: - CPU: Apple M1 Pro (10 cores) - RAM: 16GB - Storage: 1TB SSD

Software: - Rust: 1.75 - OS: macOS 14

Configuration: - Block size: 4KB - Compression: LZ4 - Cache: 64MB (unless noted)

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Write Performance

SSTable Building

100,000 entries (120 bytes avg):
  Total size: ~12MB uncompressed
  Build time: 145ms
  Throughput: 689K entries/sec

With LZ4 compression:
  Compressed size: 4.8MB (2.5x ratio)
  Build time: 178ms
  Throughput: 562K entries/sec
  Compression overhead: +33ms (+23%)

With Zstd compression:
  Compressed size: 3.4MB (3.5x ratio)
  Build time: 312ms
  Throughput: 320K entries/sec
  Compression overhead: +167ms (+115%)

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Read Performance

Point Lookups

Cache hit (warm):

Operation: reader.get(key) where key in cache
Latency p50: 450ns
Latency p95: 777µs
Latency p99: 1.2ms
Throughput: 2.2M ops/sec

Cache miss (cold, LZ4):

Operation: reader.get(key) where key not cached
Latency p50: 95µs
Latency p95: 145µs
Latency p99: 210µs
Throughput: 10.5K ops/sec

Cache miss (cold, Zstd):

Latency p50: 98µs
Latency p95: 158µs
Latency p99: 225µs
Throughput: 10.2K ops/sec

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Bloom Filter

Operation: bloom.contains(key)
Latency: 67ns avg
Throughput: 14.9M checks/sec

False positive check (key absent, bloom says present):
  Full lookup: ~100µs (wasted)
  FP rate: 0.9%
  99.1% of absent keys saved from disk I/O

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Range Scans

Scan 1,000 consecutive entries:
  Cache hot: 1.2ms (833K entries/sec)
  Cache cold (LZ4): 15ms (66K entries/sec)
  Cache cold (Zstd): 18ms (55K entries/sec)

Scan 10,000 entries:
  Cache hot: 11ms (909K entries/sec)
  Cache cold (LZ4): 142ms (70K entries/sec)

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Compression Performance

LZ4

4KB block compression:
  Time: 5.3µs
  Throughput: 754 MB/s
  Ratio: 2.5x (4096 → 1638 bytes)

4KB block decompression:
  Time: 1.05µs
  Throughput: 3.9 GB/s

Zstd (Level 3)

4KB block compression:
  Time: 9.1µs
  Throughput: 450 MB/s
  Ratio: 3.5x (4096 → 1170 bytes)

4KB block decompression:
  Time: 3.4µs
  Throughput: 1.2 GB/s

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Cache Performance

Hit Rate Impact

1M reads, 80/20 distribution:

No cache:
  Total time: 95s (all disk reads)

64MB cache (64% coverage):
  Cache hits: 800K (80%)
  Cache misses: 200K (20%)
  Total time: 19.7s
  Speedup: 4.8x

256MB cache (100% coverage):
  Cache hits: 990K (99%)
  Cache misses: 10K (1%)
  Total time: 1.4s
  Speedup: 67x

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Scalability

SSTable Size Impact

Size	Blocks	Index	Bloom	Open Time	Get (p95)
1MB	256	8KB	1.2KB	1ms	850ns
10MB	2,560	80KB	12KB	2ms	900ns
100MB	25,600	800KB	120KB	12ms	950ns
1GB	256K	8MB	1.2MB	95ms	1.1µs

Key insight: Get latency barely increases with file size (bloom + cache effectiveness).

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Real-World Workload

Hot Key Pattern (80/20)

Dataset: 1GB SSTable, 10M keys
Workload: 80% reads on 20% of keys
Cache: 256MB

Results:
  Cache hit rate: 92%
  p50 latency: 520ns
  p95 latency: 1.2µs
  p99 latency: 120µs (cache misses)
  Throughput: 1.9M reads/sec

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Summary

Key takeaways:

• Writes: 500-700K entries/sec with compression
• Hot reads: <1µs p95 with cache
• Cold reads: ~100µs p95 from SSD
• Bloom: 67ns checks, 99%+ absent key savings
• Compression: LZ4 adds <10% overhead, Zstd +100%
• Cache: 80% hit rate → 5x speedup, 99% → 60x speedup