Add logs offloading (#2075)

* add logs

* fix comm

* rework comment

src/accelerate/big_modeling.py

@@ -402,9 +402,23 @@ def dispatch_model(
             skip_keys=skip_keys,
             preload_module_classes=preload_module_classes,
         )
+
+        # warn if there is any params on the meta device
+        if len(offload) > 0:
+            offloaded_devices_str = " and ".join(
+                [device for device in set(device_map.values()) if device in ("cpu", "disk")]
+            )
+            logging.warning(
+                f"Some parameters are on the meta device device because they were offloaded to the {offloaded_devices_str}."
+            )
+
         # Attaching the hook may break tied weights, so we retie them
         retie_parameters(model, tied_params)
 
+        # warn if there is any params on the meta device
+        if len(offload) > 0:
+            logging.warn("Some parameters are on the meta device device because they were offloaded to the cpu/disk.")
+
         # add warning to cuda and to method
         def add_warning(fn, model):
             @wraps(fn)