Ruby - Threading and the GIL

gil.rb

require 'benchmark'
require 'mysql2'

x = Mysql2::Client.new
y = Mysql2::Client.new

Benchmark.bm do |b|
  b.report('w/o') do
    x.query("SELECT SLEEP(1)")
    y.query("SELECT SLEEP(1)")
  end

  b.report('with') do
    a = Thread.new{ x.query("SELECT SLEEP(1)") }
    b = Thread.new{ y.query("SELECT SLEEP(1)") }
    a.join
    b.join
  end
end

Benchmark.bm do |x|
  x.report('w/o') do
    10_000_000.times{ 2+2 }
  end

  x.report('with') do
    a = Thread.new{ 5_000_000.times{ 2+2 } }
    b = Thread.new{ 5_000_000.times{ 2+2 } }
    a.join
    b.join
  end
end

Benchmark.bm do |x|
  x.report('w/o') do
    2.times{ sleep(1) }
  end

  x.report('with') do
    a = Thread.new{ sleep(1) }
    b = Thread.new{ sleep(1) }
    a.join
    b.join
  end
end

output

       user     system      total        real
w/o  0.000000   0.000000   0.000000 (  2.002883)
with  0.000000   0.000000   0.000000 (  1.001794)

       user     system      total        real
w/o  2.470000   0.010000   2.480000 (  2.472945)
with  2.400000   0.000000   2.400000 (  2.414797)

       user     system      total        real
w/o  0.000000   0.000000   0.000000 (  2.002112)
with  0.000000   0.000000   0.000000 (  1.001252)