diff --git a/remotefilelog/__init__.py b/remotefilelog/__init__.py
--- a/remotefilelog/__init__.py
+++ b/remotefilelog/__init__.py
@@ -68,6 +68,8 @@
 import time
 import traceback
 
+from functools import partial
+
 # ensures debug commands are registered
 hgdebugcommands.command
 
@@ -130,6 +132,21 @@
     # debugdata needs remotefilelog.len to work
     extensions.wrapcommand(commands.table, 'debugdata', debugdatashallow)
 
+def extsetup(ui):
+    def _runcommandwrapper(orig, lui, repo, cmd, *args, **kwargs):
+
+        if util.safehasattr(repo, 'fileservice') and cmd == 'commit':
+            # Currently prefetches happen even during commit, and that means
+            # that sometimes it's impossible to commit offline. This is a very
+            # bad user experience, but we don't know when and why it happens.
+            # This logger should help us with that.
+            logger = partial(lui.log, 'remotefilelogcommitprefetch',
+                             user=shallowutil.getusername(repo.ui))
+            repo.fileservice.logger = logger
+        return orig(lui, repo, cmd, *args)
+
+    extensions.wrapfunction(dispatch, 'runcommand', _runcommandwrapper)
+
 def cloneshallow(orig, ui, repo, *args, **opts):
     if opts.get('shallow'):
         repos = []
diff --git a/remotefilelog/fileserverclient.py b/remotefilelog/fileserverclient.py
--- a/remotefilelog/fileserverclient.py
+++ b/remotefilelog/fileserverclient.py
@@ -557,6 +557,15 @@
         if fetchhistory:
             missingids.update(historystore.getmissing(idstocheck))
 
+        if util.safehasattr(self, 'logger') and missingids:
+            # logger is set if we want to log all prefetches (for example,
+            # prefetches that happen during command that shouldn't require
+            # network connection like hg commit).
+            # Since there can be a lot of missing ids, let's log just first 5
+            # of them
+            files = ['(%s %s)' % (f[0], hex(f[1]))
+                     for f in sorted(list(missingids))[:5]]
+            self.logger(files=', '.join(files), total=len(missingids))
         # partition missing nodes into nullid and not-nullid so we can
         # warn about this filtering potentially shadowing bugs.
         nullids = len([None for unused, id in missingids if id == nullid])
diff --git a/tests/test-remotefilelog-commit-logging.t b/tests/test-remotefilelog-commit-logging.t
new file mode 100644
--- /dev/null
+++ b/tests/test-remotefilelog-commit-logging.t
@@ -0,0 +1,66 @@
+Currently 'hg commit' sometimes requires network connection, and that means
+that people can't commit offline. Let's log these issues to understand why and
+how often it happens.
+
+  $ PYTHONPATH=$TESTDIR/..:$PYTHONPATH
+  $ export PYTHONPATH
+
+  $ . "$TESTDIR/library.sh"
+
+  $ hginit master
+  $ cd master
+  $ cat >> .hg/hgrc <<EOF
+  > [remotefilelog]
+  > server=True
+  > EOF
+  $ echo x > x
+  $ hg commit -qAm x
+  $ mkdir dir
+  $ echo y > dir/y
+  $ hg commit -qAm y
+
+  $ cd ..
+
+Shallow clone from full
+
+  $ hgcloneshallow ssh://user@dummy/master shallow --noupdate
+  streaming all changes
+  2 files to transfer, 473 bytes of data
+  transferred 473 bytes in * seconds (*/sec) (glob)
+  searching for changes
+  no changes found
+
+  $ cd shallow
+
+Setup extension that logs ui.log linkrevfixup output on the stderr
+  $ cat >> $TESTTMP/uilog.py <<EOF
+  > from mercurial import extensions
+  > from mercurial import ui as uimod
+  > def uisetup(ui):
+  >     extensions.wrapfunction(uimod.ui, 'log', mylog)
+  > def mylog(orig, self, service, *msg, **opts):
+  >     if service in ['remotefilelogcommitprefetch']:
+  >         kwstr = ", ".join("%s=%s" % (k, v) for k, v in
+  >                           sorted(opts.iteritems()))
+  >         self.warn('%s: %s\n' % (service, kwstr))
+  >     return orig(self, service, *msg, **opts)
+  > EOF
+  $ cat >> $HGRCPATH <<EOF
+  > [extensions]
+  > uilog=$TESTTMP/uilog.py
+  > EOF
+
+  $ hg update
+  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
+
+Delete the cache - it should trigger prefetch
+  $ rm -r $TESTTMP/hgcache
+  $ echo y > x
+  $ hg ci -m test
+  remotefilelogcommitprefetch: files=(dir/y 076f5e2225b3ff0400b98c92aa6cdf403ee24cca), (x 1406e74118627694268417491f018a4a883152f0), total=2, user=test
+  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
+
+Make sure that next commit doesn't trigger prefetch
+  $ echo z > x
+  $ hg ci -m test2