unsloth/studio/backend/tests/test_diffusion_memory.py
Daniel Han 3a0bd55bdf Studio diffusion (Phase 2A): measured-budget memory planner + offload/VAE policy
Add a lean, backend-agnostic memory policy that picks a CPU-offload policy and
VAE tiling/slicing from measured free device memory vs the model's estimated
resident footprint, then applies it to the built pipeline. auto stays resident
when the model fits (byte-identical to the prior resident path), and falls to
whole-module offload when tight; fast/balanced/low_vram are explicit overrides.
Sequential submodule offload is unreliable for GGUF transformers on diffusers
0.38, so it falls back to whole-module offload and status reports the policy
actually engaged.

Verified on Z-Image-Turbo Q4_K_M (B200): auto reproduces the resident image with
no VRAM/latency regression (PSNR inf); balanced/low_vram cut generation peak VRAM
47.9% (15951 -> 8318 MB) with byte-identical output, at the expected latency cost.

73 prior + 35 new CPU tests pass.
2026-06-25 13:55:08 +00:00

369 lines
14 KiB
Python

# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2026-present the Unsloth AI Inc. team. All rights reserved. See /studio/LICENSE.AGPL-3.0
"""Unit tests for the diffusion memory planner (``diffusion_memory.py``).
Hermetic and CPU-only: no torch, diffusers, GPU, or network. The device target
and the device-memory snapshot are constructed directly, so the planner's policy
matrix and the applier's pipeline calls are exercised in isolation.
"""
from __future__ import annotations
import types
import pytest
from core.inference.diffusion_memory import (
DEFAULT_IMAGE_HEIGHT,
DEFAULT_IMAGE_WIDTH,
MEMORY_MODE_BALANCED,
MEMORY_MODE_FAST,
MEMORY_MODE_LOW_VRAM,
OFFLOAD_MODEL,
OFFLOAD_NONE,
OFFLOAD_SEQUENTIAL,
DeviceMemory,
apply_memory_plan,
estimate_gguf_dense_mib,
estimate_image_runtime_mib,
infer_gguf_quant_label,
normalize_memory_mode,
plan_diffusion_memory,
snapshot_device_memory,
)
def _target(*, device = "cuda", backend = "cuda", supports_offload = True):
"""A duck-typed stand-in for DiffusionDeviceTarget (only the fields the
planner / snapshot read)."""
return types.SimpleNamespace(
device = device,
backend = backend,
supports_model_cpu_offload = supports_offload,
)
def _discrete(free_mib, total_mib = None):
return DeviceMemory("cuda", "cuda", "discrete_vram", free_mib, total_mib or free_mib)
# ── mode normalisation ────────────────────────────────────────────────────────
def test_normalize_memory_mode_accepts_and_rejects():
assert normalize_memory_mode(None) is None
assert normalize_memory_mode(" ") is None
assert normalize_memory_mode("LOW-VRAM") == "low_vram"
assert normalize_memory_mode("Balanced") == "balanced"
with pytest.raises(ValueError):
normalize_memory_mode("ultra")
# ── filename / size estimates ─────────────────────────────────────────────────
@pytest.mark.parametrize(
"filename,expected",
[
("z-image-turbo-Q4_K_M.gguf", "Q4_K_M"),
("flux1-dev-Q8_0.gguf", "Q8_0"),
("model-BF16.gguf", "BF16"),
("qwen-image-IQ4_XS.gguf", "IQ4_XS"),
("no-quant-here.gguf", None),
(None, None),
],
)
def test_infer_gguf_quant_label(filename, expected):
assert infer_gguf_quant_label(filename) == expected
def test_estimate_gguf_dense_mib_expansion():
# 4-bit roughly quadruples once dequantised to bf16; F16 is already dense.
assert estimate_gguf_dense_mib(1000, "Q4_K_M") == 4000
assert estimate_gguf_dense_mib(1000, "Q8_0") == 2000
assert estimate_gguf_dense_mib(1000, "BF16") == 1000
assert estimate_gguf_dense_mib(None, "Q4_K_M") is None
# Unknown quant falls back to the conservative 4-bit-ish factor.
assert estimate_gguf_dense_mib(1000, None) == 4000
def test_estimate_image_runtime_scales_with_pixels_and_family():
base = estimate_image_runtime_mib(width = DEFAULT_IMAGE_WIDTH, height = DEFAULT_IMAGE_HEIGHT)
bigger = estimate_image_runtime_mib(width = 2048, height = 2048)
assert bigger > base
# Distilled / turbo families get a discount.
turbo = estimate_image_runtime_mib(
width = DEFAULT_IMAGE_WIDTH, height = DEFAULT_IMAGE_HEIGHT, family = "z-image-turbo"
)
assert turbo < base
# ── planner: device classes ───────────────────────────────────────────────────
def test_cpu_target_never_offloads_but_tiles():
plan = plan_diffusion_memory(
target = _target(device = "cpu", backend = "cpu", supports_offload = False),
device_memory = DeviceMemory("cpu", "cpu", "system_memory", 8000, 16000),
model_dense_mib = 4000,
runtime_headroom_mib = 2000,
)
assert plan.offload_policy == OFFLOAD_NONE
# CPU/MPS have no separate device pool, so VAE tiling is on to cap the spike.
assert plan.vae_tiling and plan.vae_slicing
def test_mps_unified_never_auto_offloads():
plan = plan_diffusion_memory(
target = _target(device = "mps", backend = "mps", supports_offload = False),
device_memory = DeviceMemory("mps", "mps", "unified_memory", 4000, 32000),
model_dense_mib = 20000,
runtime_headroom_mib = 4000,
)
assert plan.offload_policy == OFFLOAD_NONE
assert any("unified" in r for r in plan.reasons)
def test_unified_cuda_skips_offload_even_if_offload_capable():
# An integrated CUDA SoC reports unified memory; CPU offload would free nothing.
plan = plan_diffusion_memory(
target = _target(device = "cuda", backend = "cuda", supports_offload = True),
device_memory = DeviceMemory("cuda", "cuda", "unified_memory", 2000, 16000),
model_dense_mib = 12000,
runtime_headroom_mib = 4000,
)
assert plan.offload_policy == OFFLOAD_NONE
# ── planner: auto budget tiers on a discrete GPU ──────────────────────────────
def test_auto_resident_when_roomy():
# 80 GB card, ~16 GB model: fits with headroom -> stay resident (bit-identical).
plan = plan_diffusion_memory(
target = _target(),
device_memory = _discrete(80000),
model_dense_mib = 12000,
runtime_headroom_mib = 4000,
)
assert plan.offload_policy == OFFLOAD_NONE
assert plan.vae_tiling is False and plan.vae_slicing is False # roomy -> no tiling
def test_auto_model_offload_on_tight_fit():
# 24 GB free -> reserve max(2048, 2400)=2400 -> budget 21600, 0.85*budget=18360.
# required = 16000+4000+1000 = 21000: over 0.85*budget but still under budget
# -> whole-module offload.
plan = plan_diffusion_memory(
target = _target(),
device_memory = _discrete(24000, 24000),
model_dense_mib = 16000,
runtime_headroom_mib = 4000,
base_overhead_mib = 1000,
)
assert plan.offload_policy == OFFLOAD_MODEL
assert plan.vae_tiling is True # offloading -> device is tight -> tile
def test_auto_sequential_when_model_exceeds_budget():
plan = plan_diffusion_memory(
target = _target(),
device_memory = _discrete(8000, 8000),
model_dense_mib = 40000,
runtime_headroom_mib = 4000,
)
assert plan.offload_policy == OFFLOAD_SEQUENTIAL
def test_auto_stays_resident_when_budget_unknown():
plan = plan_diffusion_memory(
target = _target(),
device_memory = _discrete(None, None),
model_dense_mib = 40000,
runtime_headroom_mib = 4000,
)
assert plan.offload_policy == OFFLOAD_NONE
assert any("unknown" in r for r in plan.reasons)
# ── planner: explicit modes + cpu_offload override ────────────────────────────
def test_explicit_modes_force_policy_regardless_of_budget():
roomy = _discrete(80000)
assert plan_diffusion_memory(
target = _target(), device_memory = roomy, model_dense_mib = 1000,
runtime_headroom_mib = 1000, requested_mode = MEMORY_MODE_FAST,
).offload_policy == OFFLOAD_NONE
assert plan_diffusion_memory(
target = _target(), device_memory = roomy, model_dense_mib = 1000,
runtime_headroom_mib = 1000, requested_mode = MEMORY_MODE_BALANCED,
).offload_policy == OFFLOAD_MODEL
assert plan_diffusion_memory(
target = _target(), device_memory = roomy, model_dense_mib = 1000,
runtime_headroom_mib = 1000, requested_mode = MEMORY_MODE_LOW_VRAM,
).offload_policy == OFFLOAD_SEQUENTIAL
def test_fast_falls_back_to_model_offload_when_it_does_not_fit():
plan = plan_diffusion_memory(
target = _target(),
device_memory = _discrete(8000, 8000),
model_dense_mib = 40000,
runtime_headroom_mib = 4000,
requested_mode = MEMORY_MODE_FAST,
)
assert plan.offload_policy == OFFLOAD_MODEL
def test_explicit_cpu_offload_overrides_resident_auto_choice():
# Roomy GPU -> auto would stay resident, but cpu_offload=True forces offload.
plan = plan_diffusion_memory(
target = _target(),
device_memory = _discrete(80000),
model_dense_mib = 4000,
runtime_headroom_mib = 2000,
explicit_offload = True,
)
assert plan.offload_policy == OFFLOAD_MODEL
assert any("explicit cpu_offload" in r for r in plan.reasons)
def test_explicit_cpu_offload_ignored_on_cpu_target():
plan = plan_diffusion_memory(
target = _target(device = "cpu", backend = "cpu", supports_offload = False),
device_memory = DeviceMemory("cpu", "cpu", "system_memory", 8000, 16000),
model_dense_mib = 4000,
runtime_headroom_mib = 2000,
explicit_offload = True,
)
assert plan.offload_policy == OFFLOAD_NONE
# ── snapshot ──────────────────────────────────────────────────────────────────
def test_snapshot_cpu_target_uses_system_memory(monkeypatch):
import core.inference.diffusion_memory as mem
monkeypatch.setattr(mem, "_system_memory_mib", lambda: (16000, 9000))
snap = snapshot_device_memory(_target(device = "cpu", backend = "cpu"))
assert snap.memory_kind == "system_memory"
assert snap.free_mib == 9000 and snap.total_mib == 16000
def test_snapshot_cuda_reads_mem_get_info(monkeypatch):
import sys
fake_torch = types.ModuleType("torch")
fake_torch.cuda = types.SimpleNamespace(
mem_get_info = lambda: (10 * 1024 * 1024 * 1024, 24 * 1024 * 1024 * 1024),
get_device_properties = lambda i: types.SimpleNamespace(integrated = False),
)
monkeypatch.setitem(sys.modules, "torch", fake_torch)
snap = snapshot_device_memory(_target())
assert snap.memory_kind == "discrete_vram"
assert snap.free_mib == 10 * 1024 and snap.total_mib == 24 * 1024
def test_snapshot_never_raises_on_probe_failure(monkeypatch):
import sys
fake_torch = types.ModuleType("torch")
def _boom():
raise RuntimeError("no cuda")
fake_torch.cuda = types.SimpleNamespace(mem_get_info = _boom)
monkeypatch.setitem(sys.modules, "torch", fake_torch)
snap = snapshot_device_memory(_target())
assert snap.free_mib is None and snap.total_mib is None
# ── applier ───────────────────────────────────────────────────────────────────
class _RecordingPipe:
def __init__(self) -> None:
self.calls: list[str] = []
def to(self, device):
self.calls.append(f"to:{device}")
return self
def enable_model_cpu_offload(self):
self.calls.append("model_offload")
def enable_sequential_cpu_offload(self):
self.calls.append("sequential_offload")
def enable_vae_tiling(self):
self.calls.append("vae_tiling")
def enable_vae_slicing(self):
self.calls.append("vae_slicing")
def _plan(policy, *, tiling):
return plan_diffusion_memory(
target = _target(),
device_memory = _discrete(80000) if policy == OFFLOAD_NONE else _discrete(4000, 8000),
model_dense_mib = 1000 if policy == OFFLOAD_NONE else 40000,
runtime_headroom_mib = 1000,
requested_mode = {
OFFLOAD_NONE: MEMORY_MODE_FAST,
OFFLOAD_MODEL: MEMORY_MODE_BALANCED,
OFFLOAD_SEQUENTIAL: MEMORY_MODE_LOW_VRAM,
}[policy],
)
def test_apply_none_places_resident():
pipe = _RecordingPipe()
effective = apply_memory_plan(pipe, _plan(OFFLOAD_NONE, tiling = False), device = "cuda")
assert pipe.calls == ["to:cuda"] # no tiling on a roomy resident run
assert effective == OFFLOAD_NONE
def test_apply_model_offload_engages_offload_and_tiling():
pipe = _RecordingPipe()
effective = apply_memory_plan(pipe, _plan(OFFLOAD_MODEL, tiling = True), device = "cuda")
assert "model_offload" in pipe.calls
assert "to:cuda" not in pipe.calls # offload owns placement; never both
assert "vae_tiling" in pipe.calls and "vae_slicing" in pipe.calls
assert effective == OFFLOAD_MODEL
def test_apply_sequential_offload():
pipe = _RecordingPipe()
effective = apply_memory_plan(pipe, _plan(OFFLOAD_SEQUENTIAL, tiling = True), device = "cuda")
assert "sequential_offload" in pipe.calls and "to:cuda" not in pipe.calls
assert effective == OFFLOAD_SEQUENTIAL
def test_apply_sequential_falls_back_to_model_offload_when_unsupported():
# Sequential offload is unreliable for GGUF on some diffusers versions; the
# applier must fall back to whole-module offload and report what actually ran.
class _NoSeqPipe(_RecordingPipe):
def enable_sequential_cpu_offload(self):
raise RuntimeError("sequential offload not supported for this transformer")
pipe = _NoSeqPipe()
effective = apply_memory_plan(pipe, _plan(OFFLOAD_SEQUENTIAL, tiling = True), device = "cuda")
assert effective == OFFLOAD_MODEL
assert "model_offload" in pipe.calls
def test_apply_tolerates_pipe_without_vae_savers():
# A pipeline missing enable_vae_* must not crash the applier.
class _Bare:
def __init__(self):
self.moved = None
def to(self, device):
self.moved = device
bare = _Bare()
apply_memory_plan(bare, _plan(OFFLOAD_NONE, tiling = False), device = "cpu")
assert bare.moved == "cpu"