--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test-revlog-mmapindex.t	Wed Sep 13 17:26:26 2017 +0000
@@ -0,0 +1,54 @@
+create verbosemmap.py
+  $ cat << EOF > verbosemmap.py
+  > # extension to make util.mmapread verbose
+  > 
+  > from __future__ import absolute_import
+  > 
+  > from mercurial import (
+  >     extensions,
+  >     util,
+  > )
+  > 
+  > def mmapread(orig, fp):
+  >     print "mmapping %s" % fp.name
+  >     return orig(fp)
+  > 
+  > def extsetup(ui):
+  >     extensions.wrapfunction(util, 'mmapread', mmapread)
+  > EOF
+
+setting up base repo
+  $ hg init a
+  $ cd a
+  $ touch a
+  $ hg add a
+  $ hg commit -qm base
+  $ for i in `$TESTDIR/seq.py 1 100` ; do
+  > echo $i > a
+  > hg commit -qm $i
+  > done
+
+set up verbosemmap extension
+  $ cat << EOF >> $HGRCPATH
+  > [extensions]
+  > verbosemmap=$TESTTMP/verbosemmap.py
+  > EOF
+
+mmap index which is now more than 4k long
+  $ hg log -l 5 -T '{rev}\n' --config experimental.mmapindexthreshold=4k
+  mmapping $TESTTMP/a/.hg/store/00changelog.i (glob)
+  100
+  99
+  98
+  97
+  96
+
+do not mmap index which is still less than 32k
+  $ hg log -l 5 -T '{rev}\n' --config experimental.mmapindexthreshold=32k
+  100
+  99
+  98
+  97
+  96
+
+  $ cd ..