diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -700,6 +700,8 @@
     b'debug.peer-request',
     default=False,
 )
+# If discovery.randomize is False, random sampling during discovery are
+# deterministic. It is meant for integration tests.
 coreconfigitem(
     b'devel',
     b'discovery.randomize',