diff -r d93436e2ca6b -r dbca2e5563c3 contrib/perf.py
--- a/contrib/perf.py	Mon Mar 25 13:16:53 2019 +0100
+++ b/contrib/perf.py	Mon Mar 25 13:43:40 2019 +0100
@@ -1,5 +1,23 @@
 # perf.py - performance test routines
-'''helper extension to measure performance'''
+'''helper extension to measure performance
+
+Configurations
+==============
+
+``perf``
+--------
+
+``all-timing``
+    When set, additional statistic will be reported for each benchmark: best,
+    worst, median average. If not set only the best timing is reported
+    (default: off).
+
+``presleep``
+  number of second to wait before any group of run (default: 1)
+
+``stub``
+    When set, benchmark will only be run once, useful for testing (default: off)
+'''
 
 # "historical portability" policy of perf.py:
 #