Support weight loading without mmap (#7469)

python/sglang/srt/managers/schedule_batch.py

@@ -101,6 +101,7 @@ GLOBAL_SERVER_ARGS_KEYS = [
     "torchao_config",
     "triton_attention_reduce_in_fp32",
     "num_reserved_decode_tokens",
+    "weight_loader_disable_mmap",
 ]
 
 # Put some global args for easy access

python/sglang/srt/model_loader/loader.py

@@ -337,7 +337,14 @@ class DefaultModelLoader(BaseModelLoader):
                 hf_weights_files,
             )
         elif use_safetensors:
-            weights_iterator = safetensors_weights_iterator(hf_weights_files)
+            from sglang.srt.managers.schedule_batch import global_server_args_dict
+
+            weight_loader_disable_mmap = global_server_args_dict.get(
+                "weight_loader_disable_mmap"
+            )
+            weights_iterator = safetensors_weights_iterator(
+                hf_weights_files, disable_mmap=weight_loader_disable_mmap
+            )
         else:
             weights_iterator = pt_weights_iterator(hf_weights_files)
 

python/sglang/srt/model_loader/weight_utils.py

@@ -422,6 +422,7 @@ def safetensors_weights_iterator(
     hf_weights_files: List[str],
     is_all_weights_sharded: bool = False,
     decryption_key: Optional[str] = None,
+    disable_mmap: bool = False,
 ) -> Generator[Tuple[str, torch.Tensor], None, None]:
     """Iterate over the weights in the model safetensor files.
 
@@ -443,7 +444,11 @@ def safetensors_weights_iterator(
         disable=not enable_tqdm,
         bar_format=_BAR_FORMAT,
     ):
-        result = safetensors.torch.load_file(st_file, device="cpu")
+        if disable_mmap:
+            with open(st_file, "rb") as f:
+                result = safetensors.torch.load(f.read())
+        else:
+            result = safetensors.torch.load_file(st_file, device="cpu")
         for name, param in result.items():
             yield name, param
 

python/sglang/srt/server_args.py

@@ -237,6 +237,7 @@ class ServerArgs:
 
     # For model weight update
     custom_weight_loader: Optional[List[str]] = None
+    weight_loader_disable_mmap: bool = False
 
     def __post_init__(self):
         # Expert parallelism
@@ -1599,6 +1600,11 @@ class ServerArgs:
             default=None,
             help="The custom dataloader which used to update the model. Should be set with a valid import path, such as my_package.weight_load_func",
         )
+        parser.add_argument(
+            "--weight-loader-disable-mmap",
+            action="store_true",
+            help="Disable mmap while loading weight using safetensors.",
+        )
 
     @classmethod
     def from_cli_args(cls, args: argparse.Namespace):