add logging to make the saving action visible (#19042)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19042

show the model saving step in the log.

Reviewed By: kennyhorror

Differential Revision: D14809385

fbshipit-source-id: c7a1e50ff92bb45b16b1c501d9325b304b07fbd3
diff --git a/caffe2/operators/load_save_op.h b/caffe2/operators/load_save_op.h
index 5657611..a901d8e 100644
--- a/caffe2/operators/load_save_op.h
+++ b/caffe2/operators/load_save_op.h
@@ -485,6 +485,8 @@
     };
 
     const vector<const Blob*>& inputs = OperatorBase::Inputs();
+    VLOG(0) << "Saving " << inputs.size() << " inputs to " << db_type_ << ": "
+            << full_db_name;
     for (int i = 0; i < inputs.size(); ++i) {
       SerializeBlob(*inputs[i], blob_names_[i], acceptor, chunk_size_);
     }