diff --git a/changelog.d/19440.misc b/changelog.d/19440.misc
new file mode 100644
index 0000000000..7777601114
--- /dev/null
+++ b/changelog.d/19440.misc
@@ -0,0 +1 @@
+Add log to explain when and why we freeze objects in the garbage collector.
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index c64c41e9d2..7f4855f36b 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -776,6 +776,11 @@ async def start(hs: "HomeServer", *, freeze: bool = True) -> None:
         #
         # PyPy does not (yet?) implement gc.freeze()
         if hasattr(gc, "freeze"):
+            logger.info(
+                "garbage collector: Freezing all allocated objects in the hopes that (almost) "
+                "everything currently allocated are things that will be used by the homeserver "
+                "for the rest of time. Doing so means less work each GC (hopefully)."
+            )
             gc.collect()
             gc.freeze()