diff --git a/hgext3rd/perftweaks.py b/hgext3rd/perftweaks.py
--- a/hgext3rd/perftweaks.py
+++ b/hgext3rd/perftweaks.py
@@ -79,6 +79,19 @@
     if repo.local() is not None:
         _preloadrevs(repo)
 
+        class perftweaksrepo(repo.__class__):
+            @localrepo.unfilteredmethod
+            def updatecaches(self, tr=None):
+                # Disable "branchmap.updatecache(self.filtered('served'))"
+                # code path guarded by "if tr.changes['revs']". First, we
+                # don't have on-disk branchmap. Second, accessing
+                # "repo.filtered('served')" alone is not very cheap.
+                if tr and 'revs' in tr.changes:
+                    tr.changes['revs'] = ()
+                super(perftweaksrepo, self).updatecaches(tr)
+
+        repo.__class__ = perftweaksrepo
+
 def _singlenode(orig, self, repo, name):
     """Skips reading branches namespace if unnecessary"""
     if repo.ui.configbool('tweakdefaults', 'allowbranch', True):