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ROCm-Research-Archive/_TestScripts/Scripts and Tests/bc250_softmax_patch_v6.py
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2026-08-20 00:45:43 +02:00

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"""
BC-250 gfx1010 Comprehensive Monkey-Patch v6
1. Replaces torch.softmax with manual implementation (VGPR overflow fix)
2. Replaces SDPA with manual implementation
3. Patches GGUF cast_bias_weight to dequant on CPU (avoids GPU page-fault hangs)
4. Pre-clones mmap'd tensor data before GPU transfer (XNACK workaround)
5. Pre-warms GPU context and caching allocator
6. Forces text encoder to CPU (memory constraint)
7. Forces VAE decode on CPU (prevents GPU page-fault hang on safetensors mmap)
v6 changes: Removed NO_VRAM (made sampling impossibly slow).
Instead, VAE is forced to decode on CPU. UNet uses normal lowvram path.
Previous LOWVRAM run: 4/4 steps in 21s (5.5s/step). NO_VRAM: stuck at 0/4 for 10+ min.
BC-250 APU / gfx1010: XNACK disabled, no GPU page fault handling.
GPU copy shader hangs on non-resident pages (mmap'd or swapped).
Place in ComfyUI root and import as first line of main.py.
"""
import torch
import torch.nn.functional as F
import os
import sys
import gc
import logging
logger = logging.getLogger(__name__)
SAFE_SOFTMAX_THRESHOLD = int(os.environ.get("BC250_SOFTMAX_THRESHOLD", "512"))
_original_softmax = torch.nn.functional.softmax
_original_tensor_softmax = torch.Tensor.softmax
_original_sdpa = torch.nn.functional.scaled_dot_product_attention
# === MMAP PRE-CLONE PATCH ===
_original_module_apply = torch.nn.Module._apply
def _bc250_safe_apply(self, fn, recurse=True):
"""Pre-clone mmap'd CPU tensor data before GPU transfer to avoid XNACK hangs."""
for key, param in self._parameters.items():
if param is not None and param.device.type == 'cpu':
param.data = param.data.clone()
for key, buf in self._buffers.items():
if buf is not None and buf.device.type == 'cpu':
self._buffers[key] = buf.clone()
return _original_module_apply(self, fn, recurse)
# === SOFTMAX PATCH ===
def _safe_softmax_impl(input, dim=-1):
x_max = input.max(dim=dim, keepdim=True).values
exp_x = torch.exp(input - x_max)
return exp_x / exp_x.sum(dim=dim, keepdim=True)
def patched_softmax(input, dim=None, _stacklevel=3, dtype=None):
if dim is None:
dim = -1
if dtype is not None:
input = input.to(dtype)
if input.is_cuda and input.shape[dim] > SAFE_SOFTMAX_THRESHOLD:
return _safe_softmax_impl(input, dim)
return _original_softmax(input, dim=dim)
def patched_tensor_softmax(self, dim=-1, dtype=None):
if dtype is not None:
self = self.to(dtype)
if self.is_cuda and self.shape[dim] > SAFE_SOFTMAX_THRESHOLD:
return _safe_softmax_impl(self, dim)
return _original_tensor_softmax(self, dim=dim)
def _safe_sdpa(query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False, scale=None):
L, S = query.size(-2), key.size(-2)
if scale is None:
scale = query.size(-1) ** -0.5
attn_weight = torch.matmul(query, key.transpose(-2, -1)) * scale
if is_causal:
causal_mask = torch.triu(torch.ones(L, S, dtype=torch.bool, device=query.device), diagonal=1)
attn_weight = attn_weight.masked_fill(causal_mask, float('-inf'))
if attn_mask is not None:
if attn_mask.dtype == torch.bool:
attn_weight = attn_weight.masked_fill(~attn_mask, float('-inf'))
else:
attn_weight = attn_weight + attn_mask
attn_weight = _safe_softmax_impl(attn_weight, dim=-1)
if dropout_p > 0.0:
attn_weight = torch.nn.functional.dropout(attn_weight, p=dropout_p)
return torch.matmul(attn_weight, value)
def patched_sdpa(query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False, scale=None):
S = key.size(-2)
if query.is_cuda and S > SAFE_SOFTMAX_THRESHOLD:
return _safe_sdpa(query, key, value, attn_mask=attn_mask,
dropout_p=dropout_p, is_causal=is_causal, scale=scale)
return _original_sdpa(query, key, value, attn_mask=attn_mask,
dropout_p=dropout_p, is_causal=is_causal, scale=scale)
# === GGUF CPU-DEQUANT PATCH (cast_bias_weight override) ===
_gguf_patched = False
def _try_patch_gguf():
"""Patch GGMLLayer.cast_bias_weight to dequant on CPU, send floats to GPU."""
global _gguf_patched
if _gguf_patched:
return True
ops_mod = None
dequant_mod = None
for name, mod in sys.modules.items():
if mod is None:
continue
if name.endswith('.ops') and 'GGUF' in name:
ops_mod = mod
if name.endswith('.dequant') and 'GGUF' in name:
dequant_mod = mod
if ops_mod is None or dequant_mod is None:
return False
GGMLLayer = getattr(ops_mod, 'GGMLLayer', None)
is_quantized_fn = getattr(dequant_mod, 'is_quantized', None)
if GGMLLayer is None or is_quantized_fn is None:
return False
def _bc250_cast_bias_weight(s, input=None, dtype=None, device=None, bias_dtype=None):
"""Dequant on CPU, only send float results to GPU."""
import comfy.model_management
import comfy.ops
if input is not None:
if dtype is None:
dtype = getattr(input, "dtype", torch.float32)
if bias_dtype is None:
bias_dtype = dtype
if device is None:
device = input.device
non_blocking = comfy.model_management.device_supports_non_blocking(device)
bias = None
if s.bias is not None:
if is_quantized_fn(s.bias):
bias = s.get_weight(s.bias, bias_dtype)
else:
bias = s.get_weight(s.bias.to(device), bias_dtype)
bias = comfy.ops.cast_to(bias, bias_dtype, device, non_blocking=non_blocking, copy=False)
if is_quantized_fn(s.weight):
weight = s.get_weight(s.weight, dtype)
else:
weight = s.get_weight(s.weight.to(device), dtype)
weight = comfy.ops.cast_to(weight, dtype, device, non_blocking=non_blocking, copy=False)
return weight, bias
GGMLLayer.cast_bias_weight = _bc250_cast_bias_weight
_gguf_patched = True
logger.warning("[BC-250] GGUF cast_bias_weight patched (CPU dequant, float-only GPU transfer)")
return True
# === IMPORT HOOK for deferred GGUF patching ===
class _GGUFImportWatcher:
def __init__(self):
self.done = False
def find_module(self, fullname, path=None):
if self.done:
return None
if 'GGUF' in fullname and ('dequant' in fullname or 'ops' in fullname):
return self
return None
def load_module(self, fullname):
if self in sys.meta_path:
sys.meta_path.remove(self)
try:
import importlib
mod = importlib.import_module(fullname)
finally:
if self not in sys.meta_path:
sys.meta_path.insert(0, self)
if _try_patch_gguf():
self.done = True
return mod
# === TEXT ENCODER CPU PATCH ===
_te_patched = False
def _try_patch_text_encoder_device():
global _te_patched
if _te_patched:
return True
mm = sys.modules.get('comfy.model_management')
if mm is None:
return False
mm.text_encoder_device = lambda: torch.device("cpu")
mm.text_encoder_offload_device = lambda: torch.device("cpu")
_te_patched = True
logger.warning("[BC-250] Text encoder forced to CPU (memory constraint)")
return True
# === VAE CPU-ONLY PATCH ===
# Force VAE to decode on CPU. VAE is only 320MB — fast enough on CPU for small images.
# Avoids GPU page-fault hangs from safetensors mmap'd weights on BC-250 (XNACK disabled).
_vae_patched = False
def _try_patch_vae_cpu():
"""Patch comfy.sd.VAE to decode and encode on CPU only."""
global _vae_patched
if _vae_patched:
return True
sd_mod = sys.modules.get('comfy.sd')
if sd_mod is None:
return False
VAE = getattr(sd_mod, 'VAE', None)
if VAE is None:
return False
_original_vae_decode = VAE.decode
_original_vae_encode = getattr(VAE, 'encode', None)
def _bc250_vae_decode(self, samples_in, vae_options={}):
"""Force VAE decode on CPU — bypass load_models_gpu entirely.
Root cause: load_models_gpu tries to unload UNet (5032MB in GPU managed memory)
before loading VAE. Unloading reads GPU pages that may be swapped → XNACK hang.
Solution: skip load_models_gpu, run VAE inference directly on CPU.
"""
import comfy.model_management as mm
logger.warning("[BC-250] VAE decode: CPU-only bypass (skipping load_models_gpu)")
torch.cuda.empty_cache()
gc.collect()
# Temporarily no-op load_models_gpu to prevent UNet unload hang
_orig_lmg = mm.load_models_gpu
mm.load_models_gpu = lambda *a, **kw: None
# Save and override device to CPU
orig_device = getattr(self, 'device', None)
orig_output_device = getattr(self, 'output_device', None)
self.device = torch.device("cpu")
self.output_device = torch.device("cpu")
try:
# Ensure VAE model weights are on CPU
if hasattr(self, 'first_stage_model'):
self.first_stage_model.to(torch.device("cpu"))
self.first_stage_model.eval()
# Run the original decode (which now skips load_models_gpu)
result = _original_vae_decode(self, samples_in, vae_options)
if isinstance(result, torch.Tensor):
result = result.to(device=torch.device("cpu"))
return result
finally:
# Restore everything
mm.load_models_gpu = _orig_lmg
if orig_device is not None:
self.device = orig_device
if orig_output_device is not None:
self.output_device = orig_output_device
VAE.decode = _bc250_vae_decode
if _original_vae_encode is not None:
def _bc250_vae_encode(self, pixel_samples):
"""Force VAE encode on CPU — same bypass as decode."""
import comfy.model_management as mm
logger.warning("[BC-250] VAE encode: CPU-only bypass")
torch.cuda.empty_cache()
gc.collect()
_orig_lmg = mm.load_models_gpu
mm.load_models_gpu = lambda *a, **kw: None
orig_device = getattr(self, 'device', None)
orig_output_device = getattr(self, 'output_device', None)
self.device = torch.device("cpu")
self.output_device = torch.device("cpu")
try:
if hasattr(self, 'first_stage_model'):
self.first_stage_model.to(torch.device("cpu"))
self.first_stage_model.eval()
pixel_samples = pixel_samples.to(device=torch.device("cpu"), dtype=torch.float32)
result = _original_vae_encode(self, pixel_samples)
if isinstance(result, torch.Tensor):
result = result.to(device=torch.device("cpu"))
return result
finally:
mm.load_models_gpu = _orig_lmg
if orig_device is not None:
self.device = orig_device
if orig_output_device is not None:
self.output_device = orig_output_device
VAE.encode = _bc250_vae_encode
_vae_patched = True
logger.warning("[BC-250] VAE forced to CPU decode/encode (prevents mmap GPU hangs)")
return True
class _SDModuleWatcher:
"""Patches comfy.sd.VAE after it's imported."""
def __init__(self):
self.done = False
def find_module(self, fullname, path=None):
if self.done:
return None
if fullname == 'comfy.sd':
return self
return None
def load_module(self, fullname):
if self in sys.meta_path:
sys.meta_path.remove(self)
try:
import importlib
mod = importlib.import_module(fullname)
finally:
if self not in sys.meta_path:
sys.meta_path.insert(0, self)
if _try_patch_vae_cpu():
self.done = True
return mod
class _ModelMgmtWatcher:
def __init__(self):
self.done = False
def find_module(self, fullname, path=None):
if self.done:
return None
if fullname == 'comfy.model_management':
return self
return None
def load_module(self, fullname):
if self in sys.meta_path:
sys.meta_path.remove(self)
try:
import importlib
mod = importlib.import_module(fullname)
finally:
if self not in sys.meta_path:
sys.meta_path.insert(0, self)
if _try_patch_text_encoder_device():
self.done = True
return mod
# === GPU MEMORY CLEANUP HOOK ===
# Patch model_management.load_models_gpu to clean up before loading
_load_patched = False
def _try_patch_load_models():
"""Add GPU memory cleanup before model loading."""
global _load_patched
if _load_patched:
return True
mm = sys.modules.get('comfy.model_management')
if mm is None:
return False
_original_load = getattr(mm, 'load_models_gpu', None)
if _original_load is None:
return False
def _bc250_load_models_gpu(models, *args, **kwargs):
"""Clean GPU cache before loading models to prevent memory pressure hangs."""
gc.collect()
torch.cuda.empty_cache()
return _original_load(models, *args, **kwargs)
mm.load_models_gpu = _bc250_load_models_gpu
_load_patched = True
logger.warning("[BC-250] GPU memory cleanup hook installed (load_models_gpu)")
return True
# === INSTALL ===
def _prewarm_gpu():
try:
if not torch.cuda.is_available():
return
dummy = torch.zeros(1, device='cuda')
_ = dummy + 1
torch.cuda.synchronize()
del dummy
torch.cuda.empty_cache()
logger.warning("[BC-250] GPU pre-warmed (context + allocator ready)")
except Exception as e:
logger.warning(f"[BC-250] GPU pre-warm failed: {e}")
def install():
# Mmap pre-clone patch
torch.nn.Module._apply = _bc250_safe_apply
logger.warning("[BC-250] Mmap pre-clone patch installed (XNACK workaround)")
# Softmax patches
torch.nn.functional.softmax = patched_softmax
torch.Tensor.softmax = patched_tensor_softmax
torch.nn.functional.scaled_dot_product_attention = patched_sdpa
logger.warning(f"[BC-250] Softmax monkey-patch installed (threshold={SAFE_SOFTMAX_THRESHOLD})")
# GGUF deferred cast_bias_weight patch
sys.meta_path.insert(0, _GGUFImportWatcher())
logger.warning("[BC-250] GGUF CPU-dequant hook registered (cast_bias_weight)")
# Text encoder CPU patch
sys.meta_path.insert(0, _ModelMgmtWatcher())
# VAE CPU-only patch
sys.meta_path.insert(0, _SDModuleWatcher())
# Try immediate patches if modules already loaded
_try_patch_gguf()
_try_patch_text_encoder_device()
_try_patch_vae_cpu()
_try_patch_load_models()
# Pre-warm GPU
_prewarm_gpu()
install()