diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -532,6 +532,9 @@
 coreconfigitem('experimental', 'evolution.track-operation',
     default=True,
 )
+coreconfigitem('experimental', 'log.topo',
+    default=False,
+)
 coreconfigitem('experimental', 'maxdeltachainspan',
     default=-1,
 )
diff --git a/mercurial/logcmdutil.py b/mercurial/logcmdutil.py
--- a/mercurial/logcmdutil.py
+++ b/mercurial/logcmdutil.py
@@ -717,6 +717,13 @@
         revs.reverse()
     return revs
 
+def _maybetoposort(repo, revs, opts):
+    if opts.get('graph') and repo.ui.configbool('experimental', 'log.topo'):
+        revs = dagop.toposort(revs, repo.changelog.parentrevs)
+        # TODO: try to iterate the set lazily
+        revs = revset.baseset(list(revs))
+    return revs
+
 def getrevs(repo, pats, opts):
     """Return (revs, differ) where revs is a smartset
 
@@ -727,7 +734,7 @@
     limit = getlimit(opts)
     revs = _initialrevs(repo, opts)
     if not revs:
-        return smartset.baseset(), None
+        return _maybetoposort(repo, smartset.baseset(), opts), None
     match, pats, slowpath = _makematcher(repo, revs, pats, opts)
     filematcher = None
     if follow:
@@ -756,7 +763,7 @@
 
     differ = changesetdiffer()
     differ._makefilematcher = filematcher
-    return revs, differ
+    return _maybetoposort(repo, revs, opts), differ
 
 def _parselinerangeopt(repo, opts):
     """Parse --line-range log option and return a list of tuples (filename,
diff --git a/tests/test-glog-topological.t b/tests/test-glog-topological.t
--- a/tests/test-glog-topological.t
+++ b/tests/test-glog-topological.t
@@ -114,3 +114,41 @@
   |/
   o  0
   
+
+Topological sort can be turned on via config
+
+  $ cat >> $HGRCPATH << EOF
+  > [experimental]
+  > log.topo=true
+  > EOF
+
+  $ hg log -G
+  o  8
+  |
+  o  3
+  |
+  o  2
+  |
+  o  1
+  |
+  | o  7
+  | |
+  | o  6
+  | |
+  | o  5
+  | |
+  | o  4
+  |/
+  o  0
+  
+Does not affect non-graph log
+  $ hg log -T '{rev}\n'
+  8
+  7
+  6
+  5
+  4
+  3
+  2
+  1
+  0