probe(review): fp8 serve row + 3-ref fixture + fp8 quality-collapse diagnosis

Review follow-up on PR #4: run --quantization fp8 through the served path on the 3090 (the flag issue 1 validated for capacity), add the untested 3-reference fixture, and measure all counts. Capacity: confirmed — all of 1/2/3/4 references fit and run (4-ref 44.1-44.4s, server peak 23,522MB, nvidia-smi max 23,983MiB; Marlin W8A16 is faster than BF16, 3.3x the Diffusers nocache baseline). Quality: every fp8 output is structurally broken on this commit and card (~97% transparent RGBA, grey RGB, PSNR 7-9dB) — on the edit path at every reference count and on T2I alike (issue 1's fp8 artifacts reinspected: same collapse; that run validated rc+image, not output structure). img_mlp exclusion does not fix it; transformer-only fp8 also collapses, pinning the culprit on the Marlin-quantized DiT. 3090 verdict stays not-built; upstream fix order is fp8 output correctness before any capacity role for it.
2026-10-08 06:27:36 -04:00
1 parent 67eb7fdb48
commit 4f5f99d8c6
@@ -16,13 +16,21 @@ same seeds 2301–2304, same per-fixture resolutions.

 **RTX 3090 (24 GB): not-built.** No host-DRAM spill path for the
 conditioning KV exists anywhere in the pipeline (verified by code read and
-by exhausting every reachable knob). The served reference ceiling is two
-condition images at `--enable-cpu-offload` — with the conditioning cache
-ON, at 2.2× the Diffusers nocache baseline's speed. Four references OOM
-inside the DiT forward under every flag combination, and the binding
-constraint is the resident BF16 working set plus a fixed ~490 MiB image-MLP
-activation, not the conditioning KV: the per-request cache contributes only
-roughly 0.25–0.3 GiB per reference (see "KV size" below).
+by exhausting every reachable knob). At BF16 the served reference ceiling
+is two condition images at `--enable-cpu-offload` — with the conditioning
+cache ON, at 2.2× the Diffusers nocache baseline's speed. Four references
+OOM inside the DiT forward under every BF16 flag combination, and the
+binding constraint is the resident BF16 working set plus a fixed ~490 MiB
+image-MLP activation, not the conditioning KV: the per-request cache
+contributes only roughly 0.25–0.3 GiB per reference (see "KV size" below).
+FP8 weight quantization (`--quantization fp8`) does free the ~6 GiB the
+arithmetic calls for — all of one, two, three, and four references then
+fit and run (4-ref: 44.1–44.4 s, server peak 23,522 MB, nvidia-smi series
+max 23,983 MiB) — **but on this commit and card the FP8 path produces
+structurally broken output** (~96.5–97% transparent RGBA, grey noise RGB,
+PSNR 7–9 dB), for the edit path at every reference count and for T2I
+alike (see "FP8 quality collapse"). So the verdict stands: no usable path
+to four references, and none that spills the KV.

 **RTX 5080 (16 GB): not-built, stronger — the server cannot initialize.**
 Six init attempts (default, cpu-offload, cpu+layerwise offload, fp8,
@@ -99,6 +107,18 @@ All runs: `vllm serve <snapshot> --omni --port 8091 --enforce-eager
 | cpuoff-layerwise | `+ --enable-layerwise-offload` | ok | **OOM** | **OOM** | **OOM** | 24,137 MiB |
 | cpuoff-fp8v (yaml) | `+ --deploy-config deploy-fp8v.yaml` | ok | OK 34.3 s | OK 36.8 s | **OOM** | 24,015 MiB |
 | cpuoff-expandable | `+ PYTORCH_CUDA_ALLOC_CONF=expandable_segments:True` | ok | OK 33.8 s | OK 36.7 s | **OOM** | 24,095 MiB |
+| fp8 | `--enable-cpu-offload --quantization fp8` | ok | OK 29.9 s | OK 34.1 s (+3-ref OK 38.9 s) | OK 44.3 s — **output broken** | 23,983 MiB |
+
+The `fp8` row (review follow-up; #1 validated this flag's capacity
+offline) also covered the previously untested three-reference count via
+`edit-compose-three` — derived from `edit-compose-four` minus
+`ref-shop-hesper` and its Subject line, four→three wording, same
+instrument (recorded in `fixtures.json`). Measured under fp8, seeds
+2301–2304: four 44.06–44.35 s (peak 22,918 MB), pair 34.62–35.05 s
+(peak 21,504 MB), three 39.44–39.69 s (peak 23,532 MB) — every request
+succeeds capacity-wise, and Marlin W8A16 is *faster* than BF16
+(4-ref 44.3 s vs Diffusers' 145.8 s = 3.3×). The quality outcome is in
+the next section.

 - 4-ref OOM signature (identical ask across configs): `Tried to allocate
  490.00 MiB` inside the image-branch MLP forward
@@ -113,6 +133,37 @@ All runs: `vllm serve <snapshot> --omni --port 8091 --enforce-eager
  `45fac0b8…` pair, `3c4eb2ef…` single) across cpuoff, cpuoff-fp8v,
  cpuoff-expandable — the frozen-seed instrument is sound.

+### FP8 quality collapse (and a correction to issue 1)
+
+Every FP8-weight output this probe produced is structurally broken, not
+merely noisier:
+
+- Signature (identical everywhere): RGBA output ~96.5–97% transparent
+  (opaque fraction 0.008–0.035, alpha mean ≈115), near-flat grey RGB
+  (mean ≈120–130), PSNR vs the Diffusers baseline 6.6–9.0 dB. The BF16
+  path on the same requests is 100% opaque and 26–29 dB.
+- Scope: the serve path at 1, 2, 3, and 4 references (all seeds measured),
+  the offline path with `fp8` minus `img_mlp`, and the offline path with
+  **transformer-only** FP8 (`quantization_config={"transformer":
+  {"method": "fp8"}}` — the text encoder stays BF16). Transformer-only
+  still collapsing pins the culprit on the Marlin-quantized DiT, not the
+  encoder and not the image-MLP. An encoder-only isolator could not
+  initialize (the encoder's bf16→fp8 conversion transient lands on the GPU
+  on top of the resident BF16 DiT and exceeds the card).
+- **Correction to issue 1**: #1's offline FP8 validation
+  (`qwen_image_21_fp8_all_rtx3090.png`, `…_fp8_imgmlp_…`) shows the same
+  collapse on reinspection (opaque fraction 0.035 both) — that run
+  validated rc=0 and image production, not output structure, so "FP8
+  weight-only works on this card" from #1 overstated it. #1's 18.4 GB
+  capacity measurement stands; its quality implication does not.
+- Upstream relevance: the recipe's H200 FP8 numbers quote PSNR only for
+  text-encoder FP8 (32.1 dB T2I); DiT-FP8 output quality appears
+  unmeasured upstream, and this probe adds the Ampere/Marlin cell:
+  online FP8 DiT weights yield near-noise latents for Qwen-Image-2.1.
+  Until that is fixed (or validated as Ampere-specific), FP8 cannot serve
+  as the capacity unlock on this card — which is why the 3090 verdict
+  remains `not-built` despite the fp8 capacity row passing.
+
 ### Offline knob runs (3090, `Omni(...)` engine kwargs)

 The one knob that reaches the cache — `extras.prefix_kv_cache_dtype` —
@@ -148,10 +199,16 @@ KV cache off, wall 81.16 s):
  samplers/kernels and the Diffusers side's int8 DiT.

 The four-reference PSNR cell the issue nominally asks for is
-**capacity-blocked on every served flag set** (and offline with fp8_v);
-the pair row is the highest-reference-count comparison this card can
-produce. `edit-compose-four` single-ref walls for reference:
-Diffusers 145.8 s (nocache); vLLM would-be number unobtainable.
+**capacity-blocked at BF16** (every served flag set, and offline with
+fp8_v). Under the fp8 serve row it becomes obtainable but meaningless as
+quality: measured seeds 2301–2304 give 7.03–7.21 dB (mean 7.11) against
+the sealed 4r baseline because the outputs are the collapsed ~97%
+transparent renders of the FP8 quality section — recorded in
+`evidence/rtx3090/psnr-fp8-rows.json` as the broken-output datum, not as
+a usable comparison. The pair row above (27.57 dB at BF16) remains the
+highest-reference-count usable comparison this card can produce.
+`edit-compose-four` wall for reference: Diffusers 145.8 s (nocache);
+vLLM 44.3 s under fp8 (fast but broken) — no valid BF16 number exists.

 ## Run matrix — RTX 5080

@@ -215,8 +272,9 @@ summaries in `evidence/rtx3090/runs-summary.json` and
  pressure of ~0.3 GiB/reference means concurrent multi-reference sessions
  do not accumulate Diffusers-style 2.8 GiB/reference retention. Candidacy
  holds for ≤2-reference profiles on 24 GB; 4-reference profiles remain
-  Diffusers-only until the resident-working-set/init path shrinks
-  (quantized-load init) or a KV spill lands.
+  Diffusers-only: FP8 unlocks the capacity (all four counts fit, 3.3×
+  baseline speed) but its output is broken on this commit, so the unlock
+  order is upstream FP8-output correctness first, then serving.
 - **#164 (topology input)**: the 5080 (16 GB) cannot host this stack at
  all — init-time parameter skeleton exceeds the card before any flag
  acts (`diffusion/models/utils.py:159-168`). Any topology plan pairing
@@ -0,0 +1,112 @@
+{
+ "edit-compose-four": {
+  "cpuoff-fp8": {
+   "rows": [
+    {
+     "seed": 2301,
+     "psnr_db": 7.03,
+     "modes": "RGBA/RGBA"
+    },
+    {
+     "seed": 2302,
+     "psnr_db": 7.11,
+     "modes": "RGBA/RGBA"
+    },
+    {
+     "seed": 2303,
+     "psnr_db": 7.1,
+     "modes": "RGBA/RGBA"
+    },
+    {
+     "seed": 2304,
+     "psnr_db": 7.21,
+     "modes": "RGBA/RGBA"
+    }
+   ],
+   "mean_db": 7.11,
+   "min_db": 7.03,
+   "max_db": 7.21,
+   "n": 4
+  },
+  "offline-fp8-imgmlp": {
+   "rows": [
+    {
+     "seed": 2301,
+     "psnr_db": 7.27,
+     "modes": "RGBA/RGBA"
+    },
+    {
+     "seed": 2302,
+     "error": "missing"
+    },
+    {
+     "seed": 2303,
+     "error": "missing"
+    },
+    {
+     "seed": 2304,
+     "error": "missing"
+    }
+   ],
+   "mean_db": 7.27,
+   "min_db": 7.27,
+   "max_db": 7.27,
+   "n": 1
+  },
+  "offline-fp8-dit": {
+   "rows": [
+    {
+     "seed": 2301,
+     "psnr_db": 6.69,
+     "modes": "RGBA/RGBA"
+    },
+    {
+     "seed": 2302,
+     "error": "missing"
+    },
+    {
+     "seed": 2303,
+     "error": "missing"
+    },
+    {
+     "seed": 2304,
+     "error": "missing"
+    }
+   ],
+   "mean_db": 6.69,
+   "min_db": 6.69,
+   "max_db": 6.69,
+   "n": 1
+  }
+ },
+ "edit-compose-pair": {
+  "cpuoff-fp8": {
+   "rows": [
+    {
+     "seed": 2301,
+     "psnr_db": 6.57,
+     "modes": "RGBA/RGBA"
+    },
+    {
+     "seed": 2302,
+     "psnr_db": 7.88,
+     "modes": "RGBA/RGBA"
+    },
+    {
+     "seed": 2303,
+     "psnr_db": 9.02,
+     "modes": "RGBA/RGBA"
+    },
+    {
+     "seed": 2304,
+     "psnr_db": 8.95,
+     "modes": "RGBA/RGBA"
+    }
+   ],
+   "mean_db": 8.11,
+   "min_db": 6.57,
+   "max_db": 9.02,
+   "n": 4
+  }
+ }
+}
@@ -452,6 +452,848 @@
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   ]
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   "offline-edit-compose-four.json": [
    {
@@ -32,5 +32,18 @@
    "height": 768,
    "prompt": "Bring the four characters from the references together in one scene; keep every identity exactly. Result: All four gather around the apothecary counter. Emotional tone: conspiratorial calm.\nSubject: Ysolde Varn, an adult woman in her early thirties, with deep brown skin, close-cropped black hair with one silver-beaded braid behind the left ear, and amber eyes; wearing a teal oilskin coat with brass buttons over a cream linen shirt; a thin pale scar through the right eyebrow and a brass compass on a cord at her throat. Unfolding a chart on the counter.\nSubject: Corvin Ashdown, an adult man in his mid-fifties, with pale, heavily freckled skin, short receding red hair and a grey-streaked red beard, and pale blue eyes; wearing a dark green harbormaster's greatcoat with a silver chain of office; a black leather patch over the left eye. Leaning on the doorframe.\nSubject: Tamsin Rook, an adult androgynous person in their late twenties, with warm olive skin, straight shoulder-length silver-white hair, and dark brown eyes; wearing a crimson hooded mantle over fitted grey leather armour; three thin black geometric lines tattooed down the left cheek. Sniffing a stoppered bottle.\nSubject: Hesper Quill, an adult woman in her early seventies, with light brown, deeply weathered skin, long white hair in one thick plait, and grey-green eyes; wearing a lavender dress under a stained canvas apothecary's apron; round wire-rimmed spectacles and a silver ring on every finger of the right hand. Behind the counter, weighing herbs on a brass scale.\nSetting: Inside the apothecary: shelves of bottled remedies, drying herbs hanging from the beams, a long counter.\nComposition: wide shot; from behind the counter's end, all four faces visible; lighting: warm lamplight with green light filtering through bottle glass\nStyle: Anime illustration: clean line art, cel shading, flat vivid colour, expressive faces.",
    "negative_prompt": null
+  },
+  "edit-compose-three": {
+    "mode": "edit",
+    "references": [
+      "ref-portrait-ysolde",
+      "ref-storm-corvin",
+      "ref-cutout-tamsin"
+    ],
+    "width": 1344,
+    "height": 768,
+    "prompt": "Bring the three characters from the references together in one scene; keep every identity exactly. Result: All three gather around the apothecary counter. Emotional tone: conspiratorial calm.\nSubject: Ysolde Varn, an adult woman in her early thirties, with deep brown skin, close-cropped black hair with one silver-beaded braid behind the left ear, and amber eyes; wearing a teal oilskin coat with brass buttons over a cream linen shirt; a thin pale scar through the right eyebrow and a brass compass on a cord at her throat. Unfolding a chart on the counter.\nSubject: Corvin Ashdown, an adult man in his mid-fifties, with pale, heavily freckled skin, short receding red hair and a grey-streaked red beard, and pale blue eyes; wearing a dark green harbormaster's greatcoat with a silver chain of office; a black leather patch over the left eye. Leaning on the doorframe.\nSubject: Tamsin Rook, an adult androgynous person in their late twenties, with warm olive skin, straight shoulder-length silver-white hair, and dark brown eyes; wearing a crimson hooded mantle over fitted grey leather armour; three thin black geometric lines tattooed down the left cheek. Sniffing a stoppered bottle.\nSetting: Inside the apothecary: shelves of bottled remedies, drying herbs hanging from the beams, a long counter.\nComposition: wide shot; from behind the counter's end, all four faces visible; lighting: warm lamplight with green light filtering through bottle glass\nStyle: Anime illustration: clean line art, cel shading, flat vivid colour, expressive faces.",
+    "negative_prompt": null,
+    "derived_from": "edit-compose-four minus ref-shop-hesper and its Subject line; four->three wording"
  }
 }
@@ -47,6 +47,12 @@ def main() -> int:
    parser = argparse.ArgumentParser()
    parser.add_argument("--out", required=True, type=pathlib.Path)
    parser.add_argument("--kv-dtype", default="fp8_v")
+    parser.add_argument(
+        "--quant",
+        default="none",
+        choices=["none", "fp8", "fp8-imgmlp", "fp8-dit", "fp8-encoder"],
+        help="weight quantization: none, fp8 (all), fp8 minus img_mlp, transformer-only, or text-encoder-only",
+    )
    parser.add_argument("--fixture", default="edit-compose-four")
    parser.add_argument("--seeds", type=lambda s: tuple(int(x) for x in s.split(",")), default=(2301,))
    parser.add_argument("--no-extras", action="store_true", help="run without the extras knob (control)")
@@ -61,11 +67,25 @@ def main() -> int:
        enable_cpu_offload=True,
        init_timeout=1200,
    )
+    if args.quant == "fp8":
+        omni_kwargs["quantization"] = "fp8"
+    elif args.quant == "fp8-imgmlp":
+        omni_kwargs["quantization_config"] = {
+            "method": "fp8",
+            "ignored_layers": ["img_mlp"],
+        }
+    elif args.quant == "fp8-dit":
+        omni_kwargs["quantization_config"] = {"transformer": {"method": "fp8"}}
+    elif args.quant == "fp8-encoder":
+        omni_kwargs["quantization_config"] = {"text_encoder": {"method": "fp8"}}
    if not args.no_extras:
        omni_kwargs["extras"] = {"prefix_kv_cache_dtype": args.kv_dtype}
    t0 = time.time()
    omni = Omni(**omni_kwargs)
-    print(f"load_s={time.time() - t0:.1f} extras={omni_kwargs.get('extras')}", flush=True)
+    print(
+        f"load_s={time.time() - t0:.1f} quant={args.quant} extras={omni_kwargs.get('extras')}",
+        flush=True,
+    )
    model_class_name = get_model_class_name(omni)

    args.out.mkdir(parents=True, exist_ok=True)
@@ -90,7 +110,7 @@ def main() -> int:
        )
        torch.cuda.reset_peak_memory_stats()
        t1 = time.time()
-        rec = {"fixture_id": args.fixture, "seed": seed, "n_references": len(refs), "kv_dtype": args.kv_dtype}
+        rec = {"fixture_id": args.fixture, "seed": seed, "n_references": len(refs), "kv_dtype": args.kv_dtype, "quant": args.quant}
        try:
            outputs = omni.generate(prompt_dict, sampling_params_list=[params])
            wall = time.time() - t1
@@ -33,6 +33,7 @@ CFG = 1.0
 FUNCTIONAL_FIXTURES = (
    "edit-expression-ysolde",  # 1 reference
    "edit-compose-pair",        # 2 references
+    "edit-compose-three",       # 3 references (derived; see fixtures.json)
    "edit-compose-four",        # 4 references
 )
 MEASURED_FIXTURE = "edit-compose-four"