[FSDP] Add FairScale FSDP adoptions logging (#913)

* Add FairScale FSDP adoptions logging

* Add FairScale FSDP adoptions logging

fairscale/experimental/nn/ssd_offload.py

@@ -207,7 +207,7 @@ class SsdTensorHandle(torch.Tensor):
         else:
             read(tensor, self.filename, self.offset * tensor.element_size())
 
-    __torch_function__ = torch._C._disabled_torch_function_impl  # type: ignore
+    __torch_function__ = torch._C._disabled_torch_function_impl
 
     @classmethod
     def __torch_dispatch__(cls, func, types, args=(), kwargs=None):  # type: ignore

fairscale/nn/data_parallel/fully_sharded_data_parallel.py

@@ -321,6 +321,13 @@ class FullyShardedDataParallel(nn.Module):
         offload_config: Optional[OffloadConfig] = None,
         state_dict_on_rank_0_only: bool = False,
     ):
+        try:
+            import torch._C
+
+            torch._C._log_api_usage_once("fairscale.fsdp")
+        except ImportError:
+            pass
+
         init_start = time.time()
         super().__init__()
         self.process_group = process_group or get_process_group_cached()