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a473c71cac
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Connector tax Phase A: build_connector_meta is 1.4ms/step (the tax source)
Per-step timing from engine_step.jsonl definitively resolves H3:
plain: 53 μs/step (p50)
noop_connector: 69 μs/step (+16 μs = negligible framework cost)
mooncake_producer: 1461 μs/step (build_connector_meta = 1386 μs)
mooncake_both: 1452 μs/step (same as producer)
The substrate tax is NOT in the v1 framework — it's specifically in
Mooncake's build_connector_meta() which walks set(cache.keys()) every
scheduler step (O(|cache|) per step, E2 audit §6.5).
Accumulated per-request tax: 256 decode steps × 1.4ms = 358ms.
Observed TTFT tax at rate=1.0: plain 378ms vs mooncake_both 422ms (+12%).
At rate=2.0 (near saturation): +29%, approaching trace-replay's +45%.
Also fixes kill_vllm() to properly kill EngineCore subprocesses.
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2026-05-26 19:33:15 +08:00 |
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297fed6e73
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Microbench 3 (connector_tax): infrastructure for KV connector substrate tax
Validates the elastic_migration_v2 finding that kv_role=kv_both adds
TTFT p90 +45% even when PD-sep never fires. Replicates under
single-instance, synthetic, open-loop workload to disambiguate
mechanism cost from 8-instance feedback amplification.
Configurations (8):
plain, noop_connector, mooncake_{producer,consumer,both},
nixl_both, lmcache_only, multi_mooncake_lmcache.
Pre-flight verification gates risky configs (kv_consumer needs dummy
bootstrap, multi-connector composition, NoOp custom class loading).
Workload: two-phase sweep
Phase A: rate {0.5..32} req/s × shape (4096, 256), saturation criteria
Phase B: ref_safe rate × cartesian (input ∈ {512,4k,32k}, output ∈ {64,256,1024})
Step-timing patch enriches vLLM's existing AGENTIC_STEP_LOG_PATH emit
with step_duration_us and build_meta_us — directly measures per-step
substrate cost, not just user-visible TTFT/TPOT.
run_all.sh runs as 5-stage barrier:
0 pre-flight + apply patch
1 Phase A all configs
2 pick ref_safe / ref_load
3 Phase B all configs
4 revert patch + analyze + plot
Outputs aggregate.{json,csv}, MANIFEST.tsv, and 5 figures.
Estimated runtime: 4-5.5 hours on idle dash0 H20.
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2026-05-26 17:27:41 +08:00 |
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