--- a/README	Tue May 30 11:39:45 2017 +0200
+++ b/README	Tue May 30 17:32:39 2017 +0200
@@ -119,6 +119,8 @@
  - olog: add an '--all' option to show the whole obsolescence history tree.
  - evolution: add an experiment to track the effect of rewrites.
    (See hg help - evolve for details)
+ - obsdiscovery: add a config flag to disable all obsmarkers discovery
+   (See hg help - evolve for details)
  - template: add a 'precursors' template that display the closests precursors of changesets
  - template: add a 'successors' template that display the closests successors of changesets
  - template: add a 'obsfate' template that display how a changeset has evolved

--- a/hgext3rd/evolve/__init__.py	Tue May 30 11:39:45 2017 +0200
+++ b/hgext3rd/evolve/__init__.py	Tue May 30 17:32:39 2017 +0200
@@ -44,6 +44,12 @@
     # * abort: abort the push
     auto-publish = ignore
 
+    # For some large repository with few markers, the current  for obsolescence
+    # markers discovery can get in the way. You can disable it with the
+    # configuration option below. This means all pushes and pulls will
+    # re-exchange all markers every time.
+    evolution.obsdiscovery = yes
+
 Obsolescence Markers Discovery Experiment
 =========================================
 

--- a/hgext3rd/evolve/obsdiscovery.py	Tue May 30 11:39:45 2017 +0200
+++ b/hgext3rd/evolve/obsdiscovery.py	Tue May 30 17:32:39 2017 +0200
@@ -872,6 +872,14 @@
     (_canobshashtree, _pushobshashtree),
 ]
 
+obsdiscovery_skip_message = """\
+(skipping discovery of obsolescence markers, will exchange everything)
+(controled by 'experimental.evolution.obsdiscovery' configuration)
+"""
+
+def usediscovery(repo):
+    return repo.ui.configbool('experimental', 'evolution.obsdiscovery', True)
+
 @eh.wrapfunction(exchange, '_pushdiscoveryobsmarkers')
 def _pushdiscoveryobsmarkers(orig, pushop):
     if _dopushmarkers(pushop):
@@ -881,6 +889,11 @@
         revs = list(repo.revs('::%ln', pushop.futureheads))
         unfi = repo.unfiltered()
 
+        if not usediscovery(repo):
+            # discovery disabled by user
+            repo.ui.status(obsdiscovery_skip_message)
+            return orig(pushop)
+
         # look for an obs-discovery protocol we can use
         discovery = None
         for candidate in obsdiscoveries:
@@ -929,6 +942,12 @@
         boundaries['common'] = [node.nullid]
         return boundaries
 
+    if not usediscovery(repo):
+        # discovery disabled by users.
+        repo.ui.status(obsdiscovery_skip_message)
+        boundaries['common'] = [node.nullid]
+        return boundaries
+
     if bundle2 and _canobshashrange(repo, remote):
         obsexcmsg(repo.ui, "looking for common markers in %i nodes\n"
                   % len(revs))

--- a/tests/test-wireproto.t	Tue May 30 11:39:45 2017 +0200
+++ b/tests/test-wireproto.t	Tue May 30 17:32:39 2017 +0200
@@ -149,4 +149,34 @@
   1 new obsolescence markers
   (run 'hg heads' to see heads)
 
+test discovery avoid exchanging known markers
+
+  $ hg push
+  pushing to ssh://user@dummy/server
+  searching for changes
+  no changes found
+  [1]
+  $ hg -R ../other pull
+  pulling from ssh://user@dummy/server
+  searching for changes
+  no changes found
+
+test discovery can be disabled
+
+  $ hg push --config experimental.evolution.obsdiscovery=no
+  pushing to ssh://user@dummy/server
+  searching for changes
+  (skipping discovery of obsolescence markers, will exchange everything)
+  (controled by 'experimental.evolution.obsdiscovery' configuration)
+  no changes found
+  remote: obsmarker-exchange: 346 bytes received
+  [1]
+  $ hg -R ../other pull --config experimental.evolution.obsdiscovery=no
+  pulling from ssh://user@dummy/server
+  searching for changes
+  no changes found
+  (skipping discovery of obsolescence markers, will exchange everything)
+  (controled by 'experimental.evolution.obsdiscovery' configuration)
+  obsmarker-exchange: 346 bytes received
+
   $ cd ..