# Paper section: PD separation under agentic workloads

This directory collects everything produced for the "PD-sep is net negative
on agentic workloads" paper section. It is one section of a larger paper,
not the whole paper.

## Layout

```
analysis/pd_sep_paper_section/
├── README.md                       # this file
├── scripts/
│   ├── plot_workload.py            # C1: input/output CDF + KV reuse decomposition
│   ├── plot_roofline.py            # C6: prefill roofline at varying cache reuse
│   └── plot_routing_lever.py       # C7: routing vs PD-sep as design levers
└── figures/
    ├── fig_c6_roofline.pdf         # rendered locally (analytical, no trace needed)
    ├── fig_c7_routing_lever.pdf    # rendered locally (from REPORT.md §3.1)
    └── (fig_c1a_io_cdf.pdf,        # produced on dash0 when trace is available
          fig_c1b_reuse.pdf)
```

## Candidate claims -> figures (status)

| Claim | Figure | Status |
|---|---|---|
| C1: 98% prefill share + 91% intra-session KV reuse | `figures/fig_c1a_io_cdf.pdf`, `figures/fig_c1b_reuse.pdf` | **needs trace on dash0** |
| C2: PD-sep vs Combined headline numbers | (not yet) | **needs re-run without --enforce-eager on `traces/w600_r0.0015_st30.jsonl`** |
| C3: decode KV cache memory wall (time-series) | (not yet) | needs step-level vLLM telemetry during PD-sep run |
| C4: TTFT stacked breakdown (prefill / KV pull / decode wait) | (not yet) | needs per-request breakdown.json from PD-sep run |
| C5: cuda-graph ablation (eager vs cudagraph × Combined vs PD-sep) | (not yet) | needs the 2×2 matrix |
| C6: prefill stays compute-bound at 95% reuse | `figures/fig_c6_roofline.pdf` | **rendered** |
| C7: cache-aware routing is a larger lever than PD-sep | `figures/fig_c7_routing_lever.pdf` | **rendered** (legacy data, footer caveat) |

## In-place edits made for this task

These edits are in the repo, not in this directory, because they modify
existing launch scripts. `--enforce-eager` was removed so cuda graphs can be
captured — PD-sep's D-node is a particularly clean case for cuda-graph
benefit and the prior methodology suppressed it.

| File | Lines | Change |
|---|---|---|
| `scripts/bench.sh` | 150, 161 | drop `--enforce-eager` (elastic + baseline modes) |
| `scripts/launch_pd_mooncake.sh` | 47, 64 | drop `--enforce-eager` (P and D instances) |
| `scripts/launch_pd_separated.sh` | 52, 68 | drop `--enforce-eager` (P and D instances) |
| `scripts/launch_phase1_ps.sh` | 32, 43 | drop `--enforce-eager` (C and PS instances) |
| `scripts/launch_elastic_p2p.sh` | 57 | drop `--enforce-eager` (kv_both instances) |

`scripts/legacy/*.sh` are intentionally left as-is — they record the
configuration of past experiments.

`REPORT.md` and `analysis/pd_separation_analysis.md` still describe the
old `--enforce-eager` setup. Update them once the new runs land.

## Reproducing the figures

From repo root:

```bash
# C1 (needs sampled trace on dash0)
.venv/bin/python analysis/pd_sep_paper_section/scripts/plot_workload.py \
    --trace traces/w600_r0.0015_st30.jsonl

# C6 (analytical, runs anywhere with matplotlib)
.venv/bin/python analysis/pd_sep_paper_section/scripts/plot_roofline.py

# C7 (hardcoded REPORT.md §3.1 numbers; no inputs)
.venv/bin/python analysis/pd_sep_paper_section/scripts/plot_routing_lever.py
```

All three default `--outdir` to `analysis/pd_sep_paper_section/figures`.

## Caveats / open items

- **C7 uses legacy data**. The footer of `fig_c7_routing_lever.pdf` says so:
  PD-sep numbers come from the random-sampled trace + `--enforce-eager`. Re-run
  on `traces/w600_r0.0015_st30.jsonl` with cuda-graphs on before paper-grade
  citation. The plotting code keeps the source numbers in a single `ROWS`
  table (top of `plot_routing_lever.py`) for a one-line swap.
- **C2/C3/C4/C5 figures are not produced** because the experiments have not
  been re-run. The 4h matrix proposed in the prior conversation turn
  (Combined + RR, Combined + cache-aware, PD-sep 4P+4D, PD-sep 6P+2D, plus
  eager-vs-cudagraph ablation, ×3 seeds) is the prerequisite.
- **C6 is analytical**, so it is independent of any re-run. The numbers
  match `scripts/compute_roofline.py` (constants are duplicated; if one
  changes, the other must change too).