perf(core): eliminate allocations in emit hot path#185
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- Reuse a module-level Date object instead of allocating new Date() on every emit/addLog call (isoNow helper) - Skip TailSamplingContext object allocation when no tail sampling is configured (the common case) - Avoid empty object allocation when emit() is called without overrides
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Benchmark reportBundle size
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commit: |
Merging this PR will degrade performance by 50.38%
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| Benchmark | BASE |
HEAD |
Efficiency | |
|---|---|---|---|---|
| ⚡ | emit minimal event |
132.5 µs | 95.6 µs | +38.6% |
| ❌ | duration match |
25.2 µs | 44.6 µs | -43.41% |
| ⚡ | evlog |
149.1 µs | 115.2 µs | +29.41% |
| ❌ | path glob match |
25.4 µs | 44.6 µs | -42.95% |
| ❌ | status match |
25.4 µs | 51.1 µs | -50.38% |
| ❌ | winston |
452.6 µs | 565.5 µs | -19.96% |
| ❌ | no match (fast path) |
25.6 µs | 45.4 µs | -43.67% |
| ⚡ | full emit with sampling (likely sampled out) |
72 µs | 61.3 µs | +17.48% |
| ⚡ | emit + JSON.stringify |
144.5 µs | 107 µs | +35.05% |
| ❌ | winston — 4 separate log calls |
431.6 µs | 592.1 µs | -27.11% |
| ❌ | push 100 events (no flush) |
424.2 µs | 563.9 µs | -24.78% |
| ❌ | push 1000 events (no flush) |
1.8 ms | 2.6 ms | -27.75% |
| ⚡ | Firefox Linux |
219.3 µs | 87.5 µs | ×2.5 |
| ⚡ | with traceparent |
472.7 µs | 337.6 µs | +40.02% |
Comparing perf/emit-hot-path (2f8061b) with main (609ad97)1
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Summary
Dateobject viaisoNow()instead ofnew Date().toISOString()on every emit — eliminates 1 heap allocation per call (pattern used by pino)TailSamplingContextobject allocation when no tail sampling is configured (the default/common case) — saves 1 object + 5 property assignments per emitif (overrides)instead of(overrides ?? {})— avoids allocating an empty object when no overrides are passedThese target
emitWideEvent(45% CPU in CodSpeed profiling) andemit()directly.