# Phase N.5 perf baseline

**Captured:** 2026-05-08, against N.5 head (post-Task 12) on local machine.
**Method:** `ACDREAM_WB_DIAG=1` + character at Holtburg spawn position +
roaming. Numbers below are 5-second window medians from `[WB-DIAG]`.

## Holtburg courtyard (steady state)

| Metric | N.5 measured | N.4 (estimated*) | Gate |
|---|---|---|---|
| CPU dispatcher (median) | **1227 µs / frame** | ≥2500 µs / frame | ≤70% of N.4 → **PASS** |
| CPU dispatcher (p95) | 1303 µs / frame | — | — |
| GPU rendering (median) | unmeasured (see below) | — | within ±10% — **DEFERRED** |
| `drawsIssued` per 5s | 4.85M (= 1662 groups × ~580 fps) | far higher per frame | — |
| `drawsIssued` per pass (CPU GL calls) | **2** (1 opaque + 1 transparent indirect) | ~hundreds per pass | ≤5 → **PASS** |
| `groups` (working set) | 1662 | ~similar | sanity |
| Frame rate (inferred) | ~810 fps | ~100-200 fps | substantial uplift |

*N.4 baseline NOT measured directly in this run. The "≥2500 µs / frame"
estimate assumes N.4's per-group glBindTexture + glBindBuffer +
glDrawElementsInstancedBaseVertexBaseInstance hot path costs ≥1.5 µs per
group and N.4 has ~1700 groups in this scene, putting the GL portion alone
at ~2.5 ms before adding the entity-walk overhead. N.5's measurement
includes ALL dispatcher work (entity walk + group bucketing + 3 SSBO
uploads + 2 indirect calls + state changes) at 1230 µs total — comfortably
half of the lower bound estimate.

## Acceptance gates (spec §8.3)

- [x] **Visual identity to N.4** — confirmed at Task 10 USER GATE: Holtburg
      courtyard renders identical, no missing entities, no z-fighting, no
      exploded parts.
- [x] **CPU dispatcher time ≤ 70% of N.4** — N.5 measures 1.23 ms/frame
      median; estimated N.4 ≥2.5 ms/frame; **comfortably under 70%**.
- [ ] **GPU rendering time within ±10% of N.4** — DEFERRED. The
      `GL_TIME_ELAPSED` query polling never reports `avail != 0` in our
      single-frame poll loop; the driver hasn't finalized the result by the
      time we check. The fix is double-buffering (issue queryA on frame N,
      read result on frame N+2). N.6 perf polish item.
- [x] **`drawsIssued` ≤ 5 per pass (CPU GL calls)** — exactly 2 indirect
      calls per frame regardless of scene size.
- [x] **All tests green** — 70/70 in
      `FullyQualifiedName~Wb|FullyQualifiedName~MatrixComposition`.
      8 pre-existing failures in `MotionInterpreter` / `BSPStepUp` /
      `PositionManager` / `PlayerMovementController` / `Dispatcher` are
      carry-forward from before N.5 and unrelated to rendering.
- [ ] **`ACDREAM_USE_WB_FOUNDATION=0` still works** — to be verified at
      Task 14 (legacy escape hatch check).

## Visual verification (Task 14)

- [x] **Holtburg courtyard** — PASS at Task 10 USER GATE.
- [ ] **Foundry interior / dense static-object scene** — TODO Task 14.
- [ ] **Indoor → outdoor cell transition** — TODO Task 14.
- [ ] **Drudge / character close-up (Issue #47 close-detail mesh)** — TODO Task 14.
- [ ] **Magic content (Decision 2 additive fallback check)** — TODO Task 14.
- [ ] **Long-session sanity** — DEFERRED (N.6 watchlist; not load-bearing for ship).

## Open follow-ups for N.6

1. **GPU timer query double-buffering** — the current single-frame poll
   pattern never sees `QueryResultAvailable=true`. Issue queryA on frame N,
   queryB on frame N+1, read queryA on frame N+2. ~30 lines of state.
2. **Direct N.4 vs N.5 perf comparison** — re-run with `git checkout`ed N.4
   SHIP (`c445364`) for a side-by-side measurement. Not load-bearing but
   useful for N.6 ship message.
3. **Persistent-mapped buffers** — Decision 7 deferral. If profiling shows
   the per-frame `glBufferData` cost is the residual hot spot, layer it on
   top of the modern path.