Gahow Wang
d71a111099
Adds analysis/pd_sep_paper_section/ as the home for the "PD separation is net negative under agentic workloads" paper section: plot scripts for C1 (workload chars), C6 (roofline), C7 (routing-vs-PD-sep lever), the C6/C7 PDFs already rendered, and a README mapping candidate claims to required figures plus open re-run items. Removes --enforce-eager from bench.sh and all active launch scripts so cuda graphs are captured -- the prior methodology suppressed one of PD-sep's structural advantages (D-node fixed-shape decode). Legacy scripts under scripts/legacy/ are intentionally untouched as historical records. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
88 lines
4.2 KiB
Markdown
88 lines
4.2 KiB
Markdown
# Paper section: PD separation under agentic workloads
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This directory collects everything produced for the "PD-sep is net negative
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on agentic workloads" paper section. It is one section of a larger paper,
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not the whole paper.
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## Layout
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```
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analysis/pd_sep_paper_section/
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├── README.md # this file
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├── scripts/
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│ ├── plot_workload.py # C1: input/output CDF + KV reuse decomposition
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│ ├── plot_roofline.py # C6: prefill roofline at varying cache reuse
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│ └── plot_routing_lever.py # C7: routing vs PD-sep as design levers
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└── figures/
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├── fig_c6_roofline.pdf # rendered locally (analytical, no trace needed)
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├── fig_c7_routing_lever.pdf # rendered locally (from REPORT.md §3.1)
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└── (fig_c1a_io_cdf.pdf, # produced on dash0 when trace is available
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fig_c1b_reuse.pdf)
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```
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## Candidate claims -> figures (status)
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| Claim | Figure | Status |
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|---|---|---|
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| C1: 98% prefill share + 91% intra-session KV reuse | `figures/fig_c1a_io_cdf.pdf`, `figures/fig_c1b_reuse.pdf` | **needs trace on dash0** |
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| C2: PD-sep vs Combined headline numbers | (not yet) | **needs re-run without --enforce-eager on `traces/w600_r0.0015_st30.jsonl`** |
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| C3: decode KV cache memory wall (time-series) | (not yet) | needs step-level vLLM telemetry during PD-sep run |
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| C4: TTFT stacked breakdown (prefill / KV pull / decode wait) | (not yet) | needs per-request breakdown.json from PD-sep run |
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| C5: cuda-graph ablation (eager vs cudagraph × Combined vs PD-sep) | (not yet) | needs the 2×2 matrix |
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| C6: prefill stays compute-bound at 95% reuse | `figures/fig_c6_roofline.pdf` | **rendered** |
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| C7: cache-aware routing is a larger lever than PD-sep | `figures/fig_c7_routing_lever.pdf` | **rendered** (legacy data, footer caveat) |
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## In-place edits made for this task
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These edits are in the repo, not in this directory, because they modify
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existing launch scripts. `--enforce-eager` was removed so cuda graphs can be
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captured — PD-sep's D-node is a particularly clean case for cuda-graph
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benefit and the prior methodology suppressed it.
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| File | Lines | Change |
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|---|---|---|
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| `scripts/bench.sh` | 150, 161 | drop `--enforce-eager` (elastic + baseline modes) |
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| `scripts/launch_pd_mooncake.sh` | 47, 64 | drop `--enforce-eager` (P and D instances) |
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| `scripts/launch_pd_separated.sh` | 52, 68 | drop `--enforce-eager` (P and D instances) |
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| `scripts/launch_phase1_ps.sh` | 32, 43 | drop `--enforce-eager` (C and PS instances) |
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| `scripts/launch_elastic_p2p.sh` | 57 | drop `--enforce-eager` (kv_both instances) |
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`scripts/legacy/*.sh` are intentionally left as-is — they record the
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configuration of past experiments.
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`REPORT.md` and `analysis/pd_separation_analysis.md` still describe the
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old `--enforce-eager` setup. Update them once the new runs land.
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## Reproducing the figures
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From repo root:
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```bash
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# C1 (needs sampled trace on dash0)
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.venv/bin/python analysis/pd_sep_paper_section/scripts/plot_workload.py \
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--trace traces/w600_r0.0015_st30.jsonl
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# C6 (analytical, runs anywhere with matplotlib)
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.venv/bin/python analysis/pd_sep_paper_section/scripts/plot_roofline.py
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# C7 (hardcoded REPORT.md §3.1 numbers; no inputs)
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.venv/bin/python analysis/pd_sep_paper_section/scripts/plot_routing_lever.py
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```
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All three default `--outdir` to `analysis/pd_sep_paper_section/figures`.
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## Caveats / open items
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- **C7 uses legacy data**. The footer of `fig_c7_routing_lever.pdf` says so:
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PD-sep numbers come from the random-sampled trace + `--enforce-eager`. Re-run
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on `traces/w600_r0.0015_st30.jsonl` with cuda-graphs on before paper-grade
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citation. The plotting code keeps the source numbers in a single `ROWS`
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table (top of `plot_routing_lever.py`) for a one-line swap.
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- **C2/C3/C4/C5 figures are not produced** because the experiments have not
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been re-run. The 4h matrix proposed in the prior conversation turn
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(Combined + RR, Combined + cache-aware, PD-sep 4P+4D, PD-sep 6P+2D, plus
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eager-vs-cudagraph ablation, ×3 seeds) is the prerequisite.
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- **C6 is analytical**, so it is independent of any re-run. The numbers
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match `scripts/compute_roofline.py` (constants are duplicated; if one
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changes, the other must change too).
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