d40db1f117
H1 (load balance) confirmed at the 15-min checkpoint: D2 received
22.5% of bindings (225 out of 1001) covering 30 unique sessions,
versus 0 in both E1 and E2. The graduated load-floor formula with
K=200 produces the intended distribution: fresh sessions on
under-loaded D, sticky sessions stay put.
But decode-1 crashed at 11:51:21 (~5 min into benchmark) with an
SGLang AssertionError in schedule_batch.py:1646. Root cause: the
streaming-session correction at line 1572-1585 patches
req.extend_input_len to 0 when len(fill_ids) < len(prefix_indices),
but the downstream invariant uses raw fill_ids/prefix_indices
lengths, so the arithmetic check fails. This is a pre-existing
landmine in the b8e6f13 SGLang vendor patch, not caused by the
load-floor bonus. It just happened to be masked in E2 by the
failure cascade preventing sessions from accumulating deep enough
prefix to trigger the correction.
Crash session 1000195 stayed on decode-1 the whole time (not a
migration race). E3 exposes this faster because sessions actually
run further with rebalanced load.
5 fix options evaluated. Recommended: Fix A — local patch at
schedule_batch.py:1646 to skip zero-extend-len reqs before
asserting. Less invasive than C (recomputing seq/prefix arrays);
addresses the actual case (D and E are workarounds, not fixes).
4 decision points for review; no code changes in this commit.
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。