diff -r fccc3eea2ddb -r 7c7d845f8b64 mercurial/manifest.py
--- a/mercurial/manifest.py	Thu Nov 10 02:13:19 2016 -0800
+++ b/mercurial/manifest.py	Thu Nov 10 02:13:19 2016 -0800
@@ -1255,10 +1255,12 @@
         self._repo = repo
 
         usetreemanifest = False
+        cachesize = 4
 
         opts = getattr(opener, 'options', None)
         if opts is not None:
             usetreemanifest = opts.get('treemanifest', usetreemanifest)
+            cachesize = opts.get('manifestcachesize', cachesize)
         self._treeinmem = usetreemanifest
 
         self._oldmanifest = repo._constructmanifest()
@@ -1266,15 +1268,9 @@
 
         # A cache of the manifestctx or treemanifestctx for each directory
         self._dirmancache = {}
+        self._dirmancache[''] = util.lrucachedict(cachesize)
 
-        # We'll separate this into it's own cache once oldmanifest is no longer
-        # used
-        self._mancache = self._oldmanifest._mancache
-        self._dirmancache[''] = self._mancache
-
-        # A future patch makes this use the same config value as the existing
-        # mancache
-        self.cachesize = 4
+        self.cachesize = cachesize
 
     def __getitem__(self, node):
         """Retrieves the manifest instance for the given node. Throws a