feat(core): add HTTP/2 performance gates

2026-08-13 21:29:21 +00:00
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+# HTTP performance baselines
+
+These numbers are regression controls, not cross-machine promises. They were measured on
+2026-08-13 under Linux 6.12/KVM, six exposed cores of an AMD Ryzen 7 1700X, Temurin 21.0.11 and
+JMH 1.37. CI uses short independent forks for allocation and sample latency so the sampling
+harness does not contaminate `gc.alloc.rate.norm`.
+
+## Gated hot paths
+
+| Benchmark | B/op | p50 ns | p99 ns | p999 ns | CI p99 ceiling ns |
+|---|---:|---:|---:|---:|---:|
+| h1 parse and route | 0.022 | 540 | 33,472 | 60,822 | 45,000 |
+| h2 pooled stream lifecycle | 0.010 | 530 | 2,138 | 37,724 | 2,900 |
+| h2 response encoding | 0.004 | 210 | 993 | 14,626 | 1,350 |
+| HPACK browser-request decode | 0.015 | 730 | 5,245 | 27,577 | 7,100 |
+| HPACK typical-response encode | 0.003 | 180 | 620 | 12,025 | 850 |
+| frame read/validate/discard | 0.006 | 70 | 1,999 | 90,508 | 2,700 |
+
+The sub-byte allocation values occur with no collection and are JMH/GC-profiler rate
+normalization noise. The CI allocation ceiling is 0.05 B/op. A benchmark exceeding it fails; a
+baseline or ceiling change requires an explicit edit and justification here.
+
+The table records the higher percentile observed across three consecutive controlled runs; this is
+important because short sample-mode runs on the shared KVM host showed visible scheduler noise.
+The p999 values expose those tails but are recorded rather than gated. The p99 ceilings are the
+worst observed p99 plus about 35% headroom.
+
+## HTTP/1 historical comparison
+
+The plan required a pre-Phase-1 number, but no benchmark was committed at that point. Phase 17
+reconstructed the current `RequestPipelineBenchmark.parseAndRoute` fixture against Phase 0 commit
+`db6e4a4` in a detached worktree and ran both revisions on the same host and JVM:
+
+| Revision | ns/op | B/op |
+|---|---:|---:|
+| Phase 0 (`db6e4a4`) | 976.195 ± 45.924 | 224.007 |
+| Phase 17 | 1,024.602 ± 50.744 | 0.007 |
+
+The hardened parser's mean is 5.0% higher and removes effectively all 224 B/op. The 99.9%
+confidence intervals overlap (`930.271–1,022.120` ns for Phase 0 and `973.858–1,075.345` ns for
+Phase 17), so this run does not establish a statistically significant latency regression. This is
+an honest reconstruction, not a claim that an absent historical run existed. Phase 17 recovered
+about 4.5% by having `RequestParser` populate `Http1HeaderMap`'s zero-copy index during the same
+validated header pass instead of rescanning every line; all security checks remain in that path.