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>
Gahow Wang
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