[PATCH] add benchmark for IO.copy_stream IO#write case

[Eric Wong <e@80x24.org>]

I will attempt to reduce garbage in proposed fix
for https://bugs.ruby-lang.org/issues/13085
---
 benchmark/bm_io_copy_stream_write.rb | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 benchmark/bm_io_copy_stream_write.rb

diff --git a/benchmark/bm_io_copy_stream_write.rb b/benchmark/bm_io_copy_stream_write.rb
new file mode 100644
index 0000000..3fd8725
--- /dev/null
+++ b/benchmark/bm_io_copy_stream_write.rb
@@ -0,0 +1,24 @@
+# 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
+  src = Zero.new
+  dst = File.open(IO::NULL, 'wb')
+  n = IO.copy_stream(src, dst)
+rescue Errno::ENOENT
+  # not *nix
+end if IO.respond_to?(:copy_stream) && IO.const_defined?(:NULL)
-- 
EW