Benchmark.bm do |x|
  x.report("100") { 100.times { filechecker.instance_variable_set(:@watched, nil); filechecker.send(:watched) } }
  x.report("500") { 500.times { filechecker.instance_variable_set(:@watched, nil); filechecker.send(:watched) } }
  x.report("1000") { 1000.times { filechecker.instance_variable_set(:@watched, nil); filechecker.send(:watched) } }
end

       user     system      total        real
100  1.848159   4.299229   6.147388 (  6.168887)
500  9.300296  21.366761  30.667057 ( 30.745420)
1000 19.483886  44.818354  64.302240 ( 64.836183)

paths = filechecker.send(:watched)
Benchmark.bm do |x|
  x.report("100") { 100.times { filechecker.send(:max_mtime, paths) } }
  x.report("500") { 500.times { filechecker.send(:max_mtime, paths) } }
  x.report("1000") { 1000.times { filechecker.send(:max_mtime, paths) } }
end

       user     system      total        real
100  1.426184   3.571109   4.997293 (  5.026946)
500  7.087467  17.499392  24.586859 ( 24.639787)
1000 14.260406  35.296779  49.557185 ( 49.607833)

@glob = filechecker.instance_variable_get :@glob
Benchmark.bm do |x|
  x.report("100") { 100.times { Dir[@glob] } }
  x.report("500") { 500.times { Dir[@glob] } }
  x.report("1000") { 1000.times { Dir[@glob] } }
end

       user     system      total        real
100  1.893343   4.713202   6.606545 (  6.740979)
500  9.211575  21.604094  30.815669 ( 30.887512)
1000 18.438504  43.192094  61.630598 ( 61.936676)