diff -r c9849bec227a -r b62d13506860 mercurial/configitems.py
--- a/mercurial/configitems.py	Fri Jun 30 03:46:01 2017 +0200
+++ b/mercurial/configitems.py	Wed Jul 05 00:01:30 2017 +0200
@@ -155,6 +155,8 @@
 coreconfigitem('ui', 'quiet',
     default=False,
 )
+# Windows defaults to a limit of 512 open files. A buffer of 128
+# should give us enough headway.
 coreconfigitem('worker', 'backgroundclosemaxqueue',
     default=384,
 )