diff --git a/benchmark/bm_io_copy_stream_write_socket.rb b/benchmark/bm_io_copy_stream_write_socket.rb
new file mode 100644
index 0000000000..11f369bd0d
--- /dev/null
+++ b/benchmark/bm_io_copy_stream_write_socket.rb
@@ -0,0 +1,35 @@
+# The goal of this is to use a synthetic (non-IO) reader
+# to trigger the read/write loop of IO.copy_stream,
+# bypassing in-kernel mechanisms like sendfile for zero copy,
+# so we wrap the /dev/zero IO object:
+class Zero
+  def initialize
+    @n = 100000
+    @in = File.open('/dev/zero', 'rb')
+  end
+
+  def read(len, buf)
+    return if (@n -= 1) == 0
+    @in.read(len, buf)
+  end
+end
+
+begin
+  require 'socket'
+  src = Zero.new
+  rd, wr = UNIXSocket.pair
+  pid = fork do
+    wr.close
+    buf = String.new
+    while rd.read(16384, buf)
+    end
+  end
+  rd.close
+  IO.copy_stream(src, wr)
+rescue Errno::ENOENT, NotImplementedError, NameError
+  # not *nix: missing /dev/zero, fork, or UNIXSocket
+rescue LoadError # no socket?
+ensure
+  wr.close if wr
+  Process.waitpid(pid) if pid
+end if IO.respond_to?(:copy_stream)