diff --git a/userbenchmark/dynamo/dynamobench/_dynamo/utils.py b/userbenchmark/dynamo/dynamobench/_dynamo/utils.py
index fe2f096ec4..e171fc905e 100644
--- a/userbenchmark/dynamo/dynamobench/_dynamo/utils.py
+++ b/userbenchmark/dynamo/dynamobench/_dynamo/utils.py
@@ -23,6 +23,7 @@
 import time
 import types
 import typing
+import warnings
 import weakref
 from contextlib import contextmanager
 from functools import lru_cache, wraps
@@ -2751,3 +2752,18 @@ def __init__(self, s):
 
     def __repr__(self):
         return self.s
+
+
+warn_once_cache: Set[str] = set()
+
+
+def warn_once(msg, stacklevel=1):
+    # Dynamo causes all warnings.warn (in user code and in Dynamo code) to print all the time.
+    # https://github.com/pytorch/pytorch/issues/128427.
+    # warn_once is a workaround: if the msg has been warned on before, then we will not
+    # warn again.
+    # NB: it's totally ok to store a cache of all the strings: this is what warnings.warn does as well.
+    if msg in warn_once_cache:
+        return
+    warn_once_cache.add(msg)
+    warnings.warn(msg, stacklevel=stacklevel + 1)