[Diffusion] Add loader-owned host-weight plans for DLO

Signed-off-by: Hongsheng Liu <liuhongsheng4@huawei.com>

vllm_omni/diffusion/offloader/base.py

@@ -27,11 +27,10 @@ class OffloadConfig:
     pin_cpu_memory: bool = True
     use_hsdp: bool = False
     dp_size: int = 1  # derived from parallel_config, not user-configurable
-    # True: add DP sharding + AllGather. False: stream the standard loader's
-    # rank-local tensors (including TP-local shards) with H2D only.
+    # True: add DP sharding + AllGather. False: stream complete rank-local
+    # blocks from the loader-selected host backing with H2D only.
     dlo_use_allgather: bool = True
     dlo_resident_layers: int = 0  # leading DiT layers kept on device
-    model_path: str | None = None  # checkpoint path for mmap weight loading
 
     @classmethod
     def from_od_config(cls, od_config: OmniDiffusionConfig) -> "OffloadConfig":
@@ -58,7 +57,6 @@ class OffloadConfig:
 
         parallel_config = getattr(od_config, "parallel_config", None)
         use_hsdp = getattr(parallel_config, "use_hsdp", False) if parallel_config else False
-
         # Derive dp_size from parallel_config — not user-configurable.
         # The offload adapts to whatever DP/SP is already configured.
         dp_size = 1
@@ -116,7 +114,8 @@ class OffloadConfig:
             dp_size = 1
             logger.info(
                 "Distributed layerwise offload: dlo_use_allgather=False, "
-                "streaming standard-loader rank-local weights (no DP shard or AllGather)"
+                "streaming complete rank-local blocks (no DLO shard or AllGather); "
+                "the backend will select mmap or standard-loader host storage"
             )
 
         # HSDP already shards parameters into DTensors.  Running distributed
@@ -137,7 +136,6 @@ class OffloadConfig:
             dp_size=dp_size,
             dlo_use_allgather=dlo_use_allgather,
             dlo_resident_layers=dlo_resident_layers,
-            model_path=getattr(od_config, "model", None),
         )