--- a/contrib/perf.py	Thu Mar 20 18:55:28 2014 -0700
+++ b/contrib/perf.py	Wed Mar 26 17:25:11 2014 -0700
@@ -335,7 +335,7 @@
     def d():
         if clear:
             repo.invalidatevolatilesets()
-        repo.revs(expr)
+        for r in repo.revs(expr): pass
     timer(d)
 
 @command('perfvolatilesets')