diff --git a/test/fiber/scheduler.rb b/test/fiber/scheduler.rb
index 7003d88417..d57e743067 100644
--- a/test/fiber/scheduler.rb
+++ b/test/fiber/scheduler.rb
@@ -1,5 +1,9 @@
 # frozen_string_literal: true
 
+# This is an example and simplified scheduler for test purposes.
+# It is not efficient for a large number of file descriptors as it uses IO.select().
+# Production Fiber schedulers should use epoll/kqueue/etc.
+
 require 'fiber'
 require 'socket'