--- a/contrib/perf.py	Tue Jan 11 14:58:17 2011 -0600
+++ b/contrib/perf.py	Tue Jan 04 14:12:52 2011 -0600
@@ -83,8 +83,7 @@
     import mercurial.changelog
     def d():
         t = repo.changelog.tip()
-        repo.changelog = mercurial.changelog.changelog(repo.sopener)
-        repo.changelog._loadindexmap()
+        repo.invalidate()
     timer(d)
 
 def perfstartup(ui, repo):