--- a/mercurial/hgweb/webcommands.py	Sat Nov 12 03:06:07 2016 +0000
+++ b/mercurial/hgweb/webcommands.py	Wed Nov 16 23:29:28 2016 -0500
@@ -861,12 +861,24 @@
     f = fctx.path()
     parity = paritygen(web.stripecount)
 
+    # parents() is called once per line and several lines likely belong to
+    # same revision. So it is worth caching.
+    # TODO there are still redundant operations within basefilectx.parents()
+    # and from the fctx.annotate() call itself that could be cached.
+    parentscache = {}
     def parents(f):
-        for p in f.parents():
-            yield {
-                "node": p.hex(),
-                "rev": p.rev(),
-            }
+        rev = f.rev()
+        if rev not in parentscache:
+            parentscache[rev] = []
+            for p in f.parents():
+                entry = {
+                    'node': p.hex(),
+                    'rev': p.rev(),
+                }
+                parentscache[rev].append(entry)
+
+        for p in parentscache[rev]:
+            yield p
 
     def annotate(**map):
         if util.binary(fctx.data()):

--- a/mercurial/scmutil.py	Sat Nov 12 03:06:07 2016 +0000
+++ b/mercurial/scmutil.py	Wed Nov 16 23:29:28 2016 -0500
@@ -392,8 +392,7 @@
             newstat = util.filestat(dstpath)
             if newstat.isambig(oldstat):
                 # stat of renamed file is ambiguous to original one
-                advanced = (oldstat.stat.st_mtime + 1) & 0x7fffffff
-                os.utime(dstpath, (advanced, advanced))
+                newstat.avoidambig(dstpath, oldstat)
             return ret
         return util.rename(self.join(src), dstpath)
 
@@ -1460,8 +1459,7 @@
             newstat = util.filestat(self._origfh.name)
             if newstat.isambig(oldstat):
                 # stat of changed file is ambiguous to original one
-                advanced = (oldstat.stat.st_mtime + 1) & 0x7fffffff
-                os.utime(self._origfh.name, (advanced, advanced))
+                newstat.avoidambig(self._origfh.name, oldstat)
 
     def __exit__(self, exc_type, exc_value, exc_tb):
         self._origfh.__exit__(exc_type, exc_value, exc_tb)

--- a/mercurial/util.py	Sat Nov 12 03:06:07 2016 +0000
+++ b/mercurial/util.py	Wed Nov 16 23:29:28 2016 -0500
@@ -1499,6 +1499,24 @@
         except AttributeError:
             return False
 
+    def avoidambig(self, path, old):
+        """Change file stat of specified path to avoid ambiguity
+
+        'old' should be previous filestat of 'path'.
+
+        This skips avoiding ambiguity, if a process doesn't have
+        appropriate privileges for 'path'.
+        """
+        advanced = (old.stat.st_mtime + 1) & 0x7fffffff
+        try:
+            os.utime(path, (advanced, advanced))
+        except OSError as inst:
+            if inst.errno == errno.EPERM:
+                # utime() on the file created by another user causes EPERM,
+                # if a process doesn't have appropriate privileges
+                return
+            raise
+
     def __ne__(self, other):
         return not self == other