benchmark:
  10: 'tmp = {}; i = 0; while i < 10; tmp[i.to_s] = i; i += 1; end;'
  20: 'tmp = {}; i = 0; while i < 20; tmp[i.to_s] = i; i += 1; end;'
  30: 'tmp = {}; i = 0; while i < 30; tmp[i.to_s] = i; i += 1; end;'
  40: 'tmp = {}; i = 0; while i < 40; tmp[i.to_s] = i; i += 1; end;'
  50: 'tmp = {}; i = 0; while i < 50; tmp[i.to_s] = i; i += 1; end;'
  60: 'tmp = {}; i = 0; while i < 60; tmp[i.to_s] = i; i += 1; end;'
  70: 'tmp = {}; i = 0; while i < 70; tmp[i.to_s] = i; i += 1; end;'
  80: 'tmp = {}; i = 0; while i < 80; tmp[i.to_s] = i; i += 1; end;'
  90: 'tmp = {}; i = 0; while i < 90; tmp[i.to_s] = i; i += 1; end;'
  100: 'tmp = {}; i = 0; while i < 100; tmp[i.to_s] = i; i += 1; end;'

Warming up --------------------------------------
                  10   566.558k i/s -    570.267k times in 1.006546s (1.77μs/i)
                  20   270.042k i/s -    275.120k times in 1.018805s (3.70μs/i)
                  30   201.843k i/s -    204.498k times in 1.013154s (4.95μs/i)
                  40   143.105k i/s -    150.535k times in 1.051917s (6.99μs/i)
                  50   119.197k i/s -    123.097k times in 1.032718s (8.39μs/i)
                  60    99.200k i/s -    100.827k times in 1.016405s (10.08μs/i)
                  70    77.240k i/s -     79.838k times in 1.033635s (12.95μs/i)
                  80    65.777k i/s -     67.920k times in 1.032576s (15.20μs/i)
                  90    61.631k i/s -     62.453k times in 1.013339s (16.23μs/i)
                 100    54.605k i/s -     56.488k times in 1.034492s (18.31μs/i)
Calculating -------------------------------------
                      bin/jruby  jruby-9.2.1.0-dev  jruby-9.2.0.0 
                  10   711.586k           701.286k       704.778k i/s -      1.700M times in 2.388570s 2.423654s 2.411643s
                  20   321.324k           302.121k       334.296k i/s -    810.125k times in 2.521209s 2.681458s 2.423378s
                  30   239.461k           197.403k       250.212k i/s -    605.528k times in 2.528711s 3.067478s 2.420059s
                  40   171.903k           131.317k       169.674k i/s -    429.316k times in 2.497435s 3.269313s 2.530241s
                  50   128.795k           110.135k       140.688k i/s -    357.591k times in 2.776439s 3.246837s 2.541730s
                  60   105.906k            94.417k       117.455k i/s -    297.598k times in 2.810011s 3.151951s 2.533721s
                  70   101.439k            71.614k        90.587k i/s -    231.720k times in 2.284337s 3.235695s 2.557970s
                  80    77.377k            76.307k        80.680k i/s -    197.331k times in 2.550264s 2.586007s 2.445860s
                  90    68.088k            66.144k        67.540k i/s -    184.892k times in 2.715494s 2.795294s 2.737522s
                 100    61.661k            53.884k        61.975k i/s -    163.813k times in 2.656681s 3.040103s 2.643221s

Comparison:
                               10
           bin/jruby:    711586.5 i/s 
       jruby-9.2.0.0:    704778.3 i/s - 1.01x  slower
   jruby-9.2.1.0-dev:    701285.7 i/s - 1.01x  slower

                               20
       jruby-9.2.0.0:    334295.8 i/s 
           bin/jruby:    321324.0 i/s - 1.04x  slower
   jruby-9.2.1.0-dev:    302121.1 i/s - 1.11x  slower

                               30
       jruby-9.2.0.0:    250212.1 i/s 
           bin/jruby:    239461.1 i/s - 1.04x  slower
   jruby-9.2.1.0-dev:    197402.5 i/s - 1.27x  slower

                               40
           bin/jruby:    171902.7 i/s 
       jruby-9.2.0.0:    169673.9 i/s - 1.01x  slower
   jruby-9.2.1.0-dev:    131316.9 i/s - 1.31x  slower

                               50
       jruby-9.2.0.0:    140688.1 i/s 
           bin/jruby:    128794.8 i/s - 1.09x  slower
   jruby-9.2.1.0-dev:    110135.2 i/s - 1.28x  slower

                               60
       jruby-9.2.0.0:    117454.9 i/s 
           bin/jruby:    105906.4 i/s - 1.11x  slower
   jruby-9.2.1.0-dev:     94417.1 i/s - 1.24x  slower

                               70
           bin/jruby:    101438.6 i/s 
       jruby-9.2.0.0:     90587.5 i/s - 1.12x  slower
   jruby-9.2.1.0-dev:     71613.7 i/s - 1.42x  slower

                               80
       jruby-9.2.0.0:     80679.6 i/s 
           bin/jruby:     77376.7 i/s - 1.04x  slower
   jruby-9.2.1.0-dev:     76307.2 i/s - 1.06x  slower

                               90
           bin/jruby:     68087.8 i/s 
       jruby-9.2.0.0:     67539.9 i/s - 1.01x  slower
   jruby-9.2.1.0-dev:     66144.0 i/s - 1.03x  slower

                              100
       jruby-9.2.0.0:     61974.8 i/s 
           bin/jruby:     61660.8 i/s - 1.01x  slower
   jruby-9.2.1.0-dev:     53884.0 i/s - 1.15x  slower