diff -r 71427ff1dff8 -r 471918fa7f46 mercurial/worker.py
--- a/mercurial/worker.py	Mon Nov 20 10:27:41 2017 -0800
+++ b/mercurial/worker.py	Sun Dec 17 11:26:25 2017 -0800
@@ -82,7 +82,8 @@
     args - arguments to split into chunks, to pass to individual
     workers
     '''
-    if worthwhile(ui, costperarg, len(args)):
+    enabled = ui.configbool('worker', 'enabled')
+    if enabled and worthwhile(ui, costperarg, len(args)):
         return _platformworker(ui, func, staticargs, args)
     return func(*staticargs + (args,))