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3bc37cc6d5
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PS experiments + H4 cache-gate + GPU profiling + Mooncake elif→if fix
Experiments run:
- Phase 0: kv_both has zero idle overhead (TPOT +1.3%, noise)
- PS V1 (cold prefill): REJECTED — PS always slower than cached C
- PS V1+flexD: 92.5% OK, HEAVY TTFT 7.8s (baseline 5.0s) — PS bottleneck
- V2 (C_s prefill + flexible D): E2E -9% but 6 errors, RDMA bimodal
- H4 (cache-gate): 198/200 OK, GPU imbalance 4.0x→2.0x, but HEAVY_OFFLOAD
TTFT=11.5s due to RDMA. HEAVY_COLO improved 10.5% from better balance.
- H5: Mooncake RDMA transfer R²=0.095, bimodal (0.6s or 18-30s)
Key findings:
- Mooncake lacks layerwise KV transfer → RDMA is pure sequential overhead
- 92% of HEAVY are turn-1 cold → offloading cold requests always loses
- GPU balance improvement from routing IS real (-10.5% HEAVY_COLO TTFT)
- RDMA transfer negates the routing benefit for offloaded requests
Code changes:
- bench.sh: add GPU timeline monitoring (gpu_monitor.sh during benchmark)
- cache_aware_proxy.py: H4 cache-gate, flexible D, PS routing
- mooncake_connector.py: elif→if fix (allow dual prefill+decode flags)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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2026-05-23 02:14:37 +08:00 |
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fc92410ec9
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Invalidate prior A/B results + add proper experiment harness
Prior cross-machine comparison (commit 1e86285) was invalid: dash0
baseline used warm instances with residual KV cache, inflating TTFT
by 2x. Evidence: inst_7 APC=68.3% impossible from 25 cold-start
requests; WARM TTFT p90=3.3s vs fresh=0.26s.
Fair same-machine comparison (both fresh restart on dash0):
Baseline: TTFT50=1.075 TPOT90=0.076 E2E50=5.075 OK=198/200
Elastic P2P: TTFT50=1.018 TPOT90=0.085 E2E50=6.977 OK=195/200
Elastic is WORSE due to Mooncake kv_both memory overhead.
Changes:
- REPORT.md: rewrite §3-4 with corrected results, add §3.5 errata
- pd_separation_analysis.md: update elastic TL;DR with correct numbers
- cache_aware_proxy.py: fix double-decrement bugs in offload path,
add 120s prefill timeout with co-located fallback (HEAVY_COLO_FALLBACK)
- bench.sh: standardized experiment harness with guaranteed GPU cleanup
and fresh-state verification (nvidia-smi check before start)
- run_elastic_stability_test.sh: two-phase elastic vs baseline test
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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2026-05-22 17:54:21 +08:00 |
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