State file use in UUID gem causes severe performance degradation

[headius]

From http://jira.codehaus.org/browse/JRUBY-6841

The 'uuid' gem uses a state file to maintain some global sequencing. However when using this file under JRuby, performance is severely impacted. It seems like the problem is its repeated reopening of the file for every UUID generated.

Benchmark:

require 'uuid'

(ARGV[0] || 5).to_i.times do
  Benchmark.bm(20) do |bm|
    bm.report("default") do
      uuid = UUID.new
      100_000.times { uuid.generate }
    end
    bm.report("default, no state file") do
      old_state_file = UUID.state_file
      UUID.state_file = false
      uuid = UUID.new
      100_000.times { uuid.generate }
      UUID.state_file = old_state_file
    end
  end
end

Numbers:

system ~/projects/jruby/tmp/uuid $ jruby -Ilib bench_uuid.rb 
                           user     system      total        real
default               10.610000   3.870000  14.480000 (  9.157000)
default, no state file  1.390000   0.370000   1.760000 (  0.767000)
                           user     system      total        real
default                4.420000   3.660000   8.080000 (  6.886000)
default, no state file  0.370000   0.000000   0.370000 (  0.352000)
                           user     system      total        real
default                3.990000   3.610000   7.600000 (  6.723000)
default, no state file  0.400000   0.000000   0.400000 (  0.349000)
                           user     system      total        real
default                3.540000   3.550000   7.090000 (  6.580000)
default, no state file  0.380000   0.000000   0.380000 (  0.339000)
                           user     system      total        real
default                3.520000   3.510000   7.030000 (  6.551000)
default, no state file  0.350000   0.000000   0.350000 (  0.328000)

system ~/projects/jruby/tmp/uuid $ rvm 1.9.3 do ruby -Ilib bench_uuid.rb 
                           user     system      total        real
default                0.740000   0.010000   0.750000 (  0.736922)
default, no state file  0.730000   0.000000   0.740000 (  0.759890)
                           user     system      total        real
default                0.730000   0.000000   0.730000 (  0.734763)
default, no state file  0.730000   0.010000   0.740000 (  0.727520)
                           user     system      total        real
default                0.730000   0.000000   0.730000 (  0.734713)
default, no state file  0.760000   0.000000   0.760000 (  0.755858)
                           user     system      total        real
default                0.750000   0.000000   0.750000 (  0.759376)
default, no state file  0.730000   0.000000   0.730000 (  0.730918)
                           user     system      total        real
default                0.730000   0.010000   0.740000 (  0.730651)
default, no state file  0.730000   0.000000   0.730000 (  0.726645)

[k77ch7]

Works for me on MacOS.
I guess that was fixed from #4393.

My env:

$ jruby -v
jruby 9.1.8.0-SNAPSHOT (2.3.1) 2017-01-15 3e4fd9e Java HotSpot(TM) 64-Bit Server VM 25.101-b13 on 1.8.0_101-b13 +jit [darwin-x86_64]

Numbers:

$ jruby -Ilib bench_uuid.rb
                           user     system      total        real
default                5.050000   0.100000   5.150000 (  1.885882)
default, no state file  2.060000   0.040000   9.060000 (  3.626896)
                           user     system      total        real
default                0.290000   0.010000   0.300000 (  0.301836)
default, no state file  0.410000   0.020000   0.430000 (  0.335635)
                           user     system      total        real
default                0.300000   0.000000   0.300000 (  0.282258)
default, no state file  1.370000   0.040000   1.410000 (  0.697191)
                           user     system      total        real
default                0.290000   0.010000   0.300000 (  0.286831)
default, no state file  0.380000   0.010000   0.390000 (  0.308904)
                           user     system      total        real
default                0.280000   0.000000   0.280000 (  0.281324)
default, no state file  0.390000   0.010000   0.400000 (  0.329983)

$ rvm jruby-9.1.7.0 do ruby -Ilib bench_uuid.rb
                           user     system      total        real
default               12.480000  13.160000  25.640000 ( 21.828986)
default, no state file  2.190000   0.030000   9.920000 (  3.741480)
                           user     system      total        real
default                4.600000   5.280000   9.880000 ( 12.094271)
default, no state file  0.420000   0.000000   0.420000 (  0.326450)
                           user     system      total        real
default                3.810000   5.210000   9.020000 ( 11.751834)
default, no state file  0.370000   0.000000   0.370000 (  0.321610)
                           user     system      total        real
default                3.240000   5.260000   8.500000 ( 12.087594)
default, no state file  0.690000   0.010000   0.700000 (  0.366765)
                           user     system      total        real
default                3.130000   5.190000   8.320000 ( 11.753569)
default, no state file  0.360000   0.010000   0.370000 (  0.324683)

[k77ch7]

ping @headius

[headius]

@k77ch7 I have no idea how #4393 would fix this, but if it's fixed it's fixed! Thanks for the ping :-)