Simple bench of the overhead of nonblocking calls that would block

nonblock_bench.rb

require 'benchmark'

inn, out = IO.pipe

5.times do
  puts Benchmark.measure {
    100_000.times do
      begin
        inn.read_nonblock(1000)
      rescue IO::WaitReadable
      end
    end
  }
end

__END__

Results without and with patch for #6154

    $ ./ruby -I lib:ext:. nonblock_bench.rb 
      0.940000   0.170000   1.110000 (  1.113261)
      0.940000   0.170000   1.110000 (  1.104994)
      0.940000   0.160000   1.100000 (  1.108880)
      0.950000   0.170000   1.120000 (  1.107059)
      0.970000   0.170000   1.140000 (  1.148363)
    
    $ ./ruby -I lib:ext:.:ext/socket nonblock_bench.rb 
      0.660000   0.140000   0.800000 (  0.808189)
      0.680000   0.150000   0.830000 (  0.814997)
      0.670000   0.140000   0.810000 (  0.811901)
      0.670000   0.140000   0.810000 (  0.804447)
      0.670000   0.140000   0.810000 (  0.817231)