--- a/contrib/perf.py	Tue Jan 18 15:55:48 2011 -0600
+++ b/contrib/perf.py	Tue Jan 18 15:55:49 2011 -0600
@@ -81,6 +81,7 @@
 
 def perfindex(ui, repo):
     import mercurial.revlog
+    mercurial.revlog._prereadsize = 2**24 # disable lazy parser in old hg
     n = repo["tip"].node()
     def d():
         repo.invalidate()