implement lightweight safetensors with READ mmap

The CoW MMAP as used by safetensors is hardcoded to CoW which forcibly
consumes windows commit charge on a zero copy. RIP. Implement safetensors
in pytorch itself with a READ mmap to not get commit charged for all our
open models.

comfy/utils.py

@@ -28,8 +28,12 @@ import logging
 import itertools
 from torch.nn.functional import interpolate
 from einops import rearrange
-from comfy.cli_args import args
+from comfy.cli_args import args, enables_dynamic_vram
 import json
+import mmap
+import ctypes
+
+import packaging
 
 MMAP_TORCH_FILES = args.mmap_torch_files
 DISABLE_MMAP = args.disable_mmap
@@ -55,21 +59,72 @@ if hasattr(torch.serialization, "add_safe_globals"):  # TODO: this was added in
 else:
     logging.warning("Warning, you are using an old pytorch version and some ckpt/pt files might be loaded unsafely. Upgrading to 2.4 or above is recommended as older versions of pytorch are no longer supported.")
 
+# Current as of safetensors 0.7.0
+_TYPES = {
+    "F64": torch.float64,
+    "F32": torch.float32,
+    "F16": torch.float16,
+    "BF16": torch.bfloat16,
+    "I64": torch.int64,
+    "I32": torch.int32,
+    "I16": torch.int16,
+    "I8": torch.int8,
+    "U8": torch.uint8,
+    "BOOL": torch.bool,
+    "F8_E4M3": torch.float8_e4m3fn,
+    "F8_E5M2": torch.float8_e5m2,
+    "C64": torch.complex64,
+}
+if packaging.version.Version(torch.__version__) >= packaging.version.Version("2.3.0"):
+    _TYPES.update(
+        {
+            "U64": torch.uint64,
+            "U32": torch.uint32,
+            "U16": torch.uint16,
+        }
+    )
+
+def load_safetensors(ckpt):
+    f = open(ckpt, "rb")
+    mapping = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ)
+
+    header_size = struct.unpack("<Q", mapping[:8])[0]
+    header = json.loads(mapping[8:8+header_size].decode("utf-8"))
+
+    data_area = torch.frombuffer(mapping, dtype=torch.uint8)[8 + header_size:]
+
+    sd = {}
+    for name, info in header.items():
+        if name == "__metadata__": continue
+
+        start, end = info["data_offsets"]
+        sd[name] = data_area[start:end].view(_TYPES[info["dtype"]]).view(info["shape"])
+
+    return sd, header.get("__metadata__", {}),
+
+
 def load_torch_file(ckpt, safe_load=False, device=None, return_metadata=False):
     if device is None:
         device = torch.device("cpu")
+    else:
+        assert False
     metadata = None
     if ckpt.lower().endswith(".safetensors") or ckpt.lower().endswith(".sft"):
         try:
-            with safetensors.safe_open(ckpt, framework="pt", device=device.type) as f:
-                sd = {}
-                for k in f.keys():
-                    tensor = f.get_tensor(k)
-                    if DISABLE_MMAP:  # TODO: Not sure if this is the best way to bypass the mmap issues
-                        tensor = tensor.to(device=device, copy=True)
-                    sd[k] = tensor
-                if return_metadata:
-                    metadata = f.metadata()
+            if enables_dynamic_vram():
+                sd, metadata = load_safetensors(ckpt)
+                if not return_metadata:
+                    metadata = None
+            else:
+                with safetensors.safe_open(ckpt, framework="pt", device=device.type) as f:
+                    sd = {}
+                    for k in f.keys():
+                        tensor = f.get_tensor(k)
+                        if DISABLE_MMAP:  # TODO: Not sure if this is the best way to bypass the mmap issues
+                            tensor = tensor.to(device=device, copy=True)
+                        sd[k] = tensor
+                    if return_metadata:
+                        metadata = f.metadata()
         except Exception as e:
             if len(e.args) > 0:
                 message = e.args[0]