diff --git a/mercurial/changelog.py b/mercurial/changelog.py
--- a/mercurial/changelog.py
+++ b/mercurial/changelog.py
@@ -385,6 +385,9 @@
             datafile=datafile,
             checkambig=True,
             mmaplargeindex=True,
+            persistentnodemap=opener.options.get(
+                'exp-persistent-nodemap', False
+            ),
         )
 
         if self._initempty and (self.version & 0xFFFF == revlog.REVLOGV1):
diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -660,6 +660,9 @@
     b'experimental', b'rust.index', default=False,
 )
 coreconfigitem(
+    b'experimental', b'exp-persistent-nodemap', default=False,
+)
+coreconfigitem(
     b'experimental', b'server.filesdata.recommended-batch-size', default=50000,
 )
 coreconfigitem(
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -929,6 +929,8 @@
 
     if ui.configbool(b'experimental', b'rust.index'):
         options[b'rust.index'] = True
+    if ui.configbool('experimental', 'exp-persistent-nodemap'):
+        options[b'exp-persistent-nodemap'] = True
 
     return options
 
diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -407,6 +407,7 @@
         mmaplargeindex=False,
         censorable=False,
         upperboundcomp=None,
+        persistentnodemap=False,
     ):
         """
         create a revlog object
@@ -418,6 +419,10 @@
         self.upperboundcomp = upperboundcomp
         self.indexfile = indexfile
         self.datafile = datafile or (indexfile[:-2] + b".d")
+        self.nodemap_file = None
+        if persistentnodemap:
+            self.nodemap_file = indexfile[:-2] + b".n"
+
         self.opener = opener
         #  When True, indexfile is opened with checkambig=True at writing, to
         #  avoid file stat ambiguity.
@@ -2286,6 +2291,7 @@
             ifh.write(data[0])
             ifh.write(data[1])
             self._enforceinlinesize(transaction, ifh)
+        nodemaputil.setup_persistent_nodemap(transaction, self)
 
     def addgroup(self, deltas, linkmapper, transaction, addrevisioncb=None):
         """
diff --git a/mercurial/revlogutils/nodemap.py b/mercurial/revlogutils/nodemap.py
--- a/mercurial/revlogutils/nodemap.py
+++ b/mercurial/revlogutils/nodemap.py
@@ -21,6 +21,39 @@
         raise error.RevlogError(b'unknown node: %s' % x)
 
 
+def setup_persistent_nodemap(tr, revlog):
+    """Install whatever is needed transaction side to persist a nodemap on disk
+
+    (only actually persist the nodemap if this is relevant for this revlog)
+    """
+    if revlog.nodemap_file is None:
+        return  # we do not use persistent_nodemap on this revlog
+    callback_id = b"revlog-persistent-nodemap-%s" % revlog.nodemap_file
+    if tr.hasfinalize(callback_id):
+        return  # no need to register again
+    tr.addfinalize(callback_id, lambda tr: _persist_nodemap(tr, revlog))
+
+
+def _persist_nodemap(tr, revlog):
+    """Write nodemap data on disk for a given revlog
+    """
+    if getattr(revlog, 'filteredrevs', ()):
+        raise error.ProgrammingError(
+            "cannot persist nodemap of a filtered changelog"
+        )
+    if revlog.nodemap_file is None:
+        msg = "calling persist nodemap on a revlog without the feature enableb"
+        raise error.ProgrammingError(msg)
+    data = persistent_data(revlog.index)
+    # EXP-TODO: if this is a cache, this should use a cache vfs, not a
+    # store vfs
+    with revlog.opener(revlog.nodemap_file, 'w') as f:
+        f.write(data)
+    # EXP-TODO: if the transaction abort, we should remove the new data and
+    # reinstall the old one. (This will be simpler when the file format get a
+    # bit more advanced)
+
+
 ### Nodemap Trie
 #
 # This is a simple reference implementation to compute and serialise a nodemap
diff --git a/tests/test-persistent-nodemap.t b/tests/test-persistent-nodemap.t
--- a/tests/test-persistent-nodemap.t
+++ b/tests/test-persistent-nodemap.t
@@ -5,8 +5,14 @@
 
   $ hg init test-repo
   $ cd test-repo
+  $ cat << EOF >> .hg/hgrc
+  > [experimental]
+  > exp-persistent-nodemap=yes
+  > EOF
   $ hg debugbuilddag .+5000
-  $ hg debugnodemap --dump | f --sha256 --bytes=256 --hexdump --size
+  $ hg debugnodemap --dump | f --sha256 --size
+  size=245760, sha256=bc400bf49f11e83bbd25630439feee6628a80a8602d2e38972eac44cc3efe10c
+  $ f --sha256 --bytes=256 --hexdump --size < .hg/store/00changelog.n
   size=245760, sha256=bc400bf49f11e83bbd25630439feee6628a80a8602d2e38972eac44cc3efe10c
   0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
   0010: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|