diff --git a/contrib/perf-utils/subsetmaker.py b/contrib/perf-utils/subsetmaker.py
--- a/contrib/perf-utils/subsetmaker.py
+++ b/contrib/perf-utils/subsetmaker.py
@@ -102,7 +102,9 @@
     for x in range(n):
         if not heads:
             break
-        pick = rand.choice(list(heads))
+        pickable = list(heads)
+        pickable.sort()
+        pick = rand.choice(pickable)
         heads.remove(pick)
         assert pick not in selected
         selected.add(pick)