7f2ebf3d87
Q1: Mooncake "is not alive" is hair-trigger — a single
send_kvcache_slice ret != 0 in
third_party/sglang/python/sglang/srt/disaggregation/mooncake/conn.py
:1270 permanently adds the D's mooncake_session_id to failed_sessions
and blacklists it for the rest of the process lifetime. The D worker
process is alive (D1 keeps serving admit_direct_append OK seconds
after), but every subsequent P→D transfer for that session
short-circuits at conn.py:1184. The "Failures should never happen if
the session is not dead" comment encodes the wrong assumption for the
saturation regime we hit.
Q2: KVC v2's migration mechanism IS sound but its trigger is gated
by replay.py:1379 _ADMISSION_REJECTION_SUBSTRINGS = ("session-cap",
"no-d-capacity", "d-backpressure"). All 1054 failures have
execution_mode="kvcache-centric" (generic fallback bucket) which
contains none of those substrings, so session_d_rejects is never
incremented. Empirically 46 of 49 (sess, D) pairs that the worker
RPC rejected would have qualified for blacklist (most-rejected
pair: 25 rejects), but policy never saw them. Result: D0 reject
→ next-bind D0 (253×), D1 reject → next-bind D1 (329×), D0/D1 reject
→ next-bind D2 (0×).
Fix paths documented for both, shortest path is widening the
substring filter to include the failure-fallback bucket, but the
right fix is to call record_admission_reject directly from the
actual rejection signal site instead of string-matching execution_mode.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Agentic PD Hybrid
这个项目是在 SGLang xPyD 上做一个最小实验框架，用来判断：
面向 agentic coding workload 的 session-aware / KV-cache-aware P/D routing，能不能降低端到端延迟。
更完整但仍然简洁的说明见 docs/PROJECT_OVERVIEW.md。
当前做了什么
- 启动单机 SGLang P/D 栈。
- 回放 Ali coding agent trace，并记录 request-level metrics。
- 支持
default、sticky、kv-aware路由策略。 - 支持
pd-disaggregation、kvcache-centric、pd-colo对比。 - 支持小 append、多轮 session 的 micro-benchmark trace。
- 维护了基于 SGLang
v0.5.10的本地 patch，放在third_party/sglang。
环境
统一使用 uv：
uv sync
默认模型路径：
~/models/Qwen/Qwen3-Coder-30B-A3B-Instruct
当前主要测试环境是单机 8 GPU，约束是 prefill + decode <= 8。
常用命令
生成小 append trace：
uv run agentic-pd-hybrid make-small-append-trace \
--output outputs/smoke-hotcap-30k-1k-256.jsonl \
--session-count 4 \
--turns-per-session 3 \
--initial-input-length 30000 \
--append-input-length 1000 \
--output-length 256
跑 live benchmark：
uv run agentic-pd-hybrid benchmark-live \
--trace outputs/micro-serveable-varturn-30k-1k-256-20260424T0756Z.jsonl \
--output-root outputs/live-serveable-varturn-30k-1k-256-hotcap \
--mechanism kvcache-centric \
--policy kv-aware \
--kvcache-admission-mode worker \
--prefill-workers 1 \
--decode-workers 1 \
--prefill-gpu-ids 0 \
--decode-gpu-ids 1 \
--transfer-backend mooncake \
--target-duration-s 2000 \
--session-sample-rate 1.0 \
--min-turns 2 \
--time-scale 1 \
--concurrency-limit 1000
只回放并写 metrics：
uv run agentic-pd-hybrid replay \
--trace path/to/trace.jsonl \
--policy kv-aware \
--mechanism pd-disaggregation \
--router-url http://127.0.0.1:8000 \
--output outputs/replay.jsonl
输出
每次 replay/benchmark 会写：
- request metrics：
request-metrics.jsonl - 汇总结果：
request-metrics.jsonl.summary.json
重点看：
- E2E latency
- TTFT / TPOT
- execution mode
- cached tokens
- KV transfer blocks
- error
维护约定
- 项目代码改动：
feat:/fix:/docs:。 - SGLang 改动：
feat(sglang): .../fix(sglang): ...。 third_party/sglang的基线是 clean SGLangv0.5.10snapshot。- 不提交
outputs/、日志、__pycache__、虚拟环境。