test-io.rb

#!/usr/bin/env ruby

require 'benchmark'

class Reading
  def initialize
    @r, @w = IO.pipe

    @thread = Thread.new do
      @r.read
    rescue IOError
      # Ignore.
    end
  end

  attr :r
  attr :w

  attr :thread

  def join
    @thread.join
  end
end

count = ARGV.last.to_i
# count = 10, average time to close = 0.06ms
# count = 10_000, average time to close = 1.2ms

readings = count.times.map do
  Reading.new
end

sleep 0.1

duration = Benchmark.measure do
  readings.each do |reading|
    reading.r.close
    reading.w.close
  end
end

pp duration: duration, average: (duration/count)

readings.each(&:join)