bpo-41006: Document the runpy optimization (GH-20953)

diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
index 9878f7f81cedac28918a834d1a3466620e050fba..1f4840fc0fb8efb76983085e60d3252c590af3fb 100644 (file)
--- a/Doc/whatsnew/3.10.rst
+++ b/Doc/whatsnew/3.10.rst
@@ -103,6 +103,11 @@ Improved Modules
 Optimizations
 =============
 
+* The :mod:`runpy` module now imports less modules.
+  The ``python3 -m module-name`` command startup time is 1.3x faster in
+  average.
+  (Contributed by Victor Stinner in :issue:`41006`.)
+
 
 Deprecated
 ==========