Restrain tokenizer.model_max_length default (#9681)

* Restrain tokenizer.model_max_length default

* Fix indent

examples/language-modeling/run_mlm.py

@@ -338,6 +338,12 @@ def main():
 
         if data_args.max_seq_length is None:
             max_seq_length = tokenizer.model_max_length
+            if max_seq_length > 1024:
+                logger.warn(
+                    f"The tokenizer picked seems to have a very large `model_max_length` ({tokenizer.model_max_length}). "
+                    "Picking 1024 instead. You can change that default value by passing --max_seq_length xxx."
+                )
+                max_seq_length = 1024
         else:
             if data_args.max_seq_length > tokenizer.model_max_length:
                 logger.warn(