benchmark/io_copy_stream_write.yml


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prelude: |
  # 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:
benchmark:
  io_copy_stream_write: |

    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)
loop_count: 1