You can use "measure" command to check performance in IRB like below:

  irb(main):001:0> 3
  => 3
  irb(main):002:0> measure
  TIME is added.
  => nil
  irb(main):003:0> 3
  processing time: 0.000058s
  => 3
  irb(main):004:0> measure :off
  => nil
  irb(main):005:0> 3
  => 3

You can set "measure :on" by "IRB.conf[:MEASURE] = true" in .irbrc, and, also,
set custom performance check method:

  IRB.conf[:MEASURE_PROC][:CUSTOM] = proc { |context, code, line_no, &block|
    time = Time.now
    result = block.()
    now = Time.now
    puts 'custom processing time: %fs' % (Time.now - time) if IRB.conf[:MEASURE]
    result
  }

https://github.com/ruby/irb/commit/3899eaf2e2