gvl_release.rb

require 'fiddle'
require 'fiddle/import'

module GVL
  include Fiddle
  extend Importer

  dlload Handle::DEFAULT

  T = import_function 'rb_thread_call_without_gvl', TYPE_VOIDP,
    [TYPE_VOIDP, TYPE_VOIDP, TYPE_VOIDP, TYPE_VOIDP]

  def self.without_blocking(&block)
    cl = Closure::BlockCaller.new(TYPE_VOIDP, [TYPE_VOIDP]){ Fiddle.dlwrap(block.call) }
    T.call(cl, nil, nil, nil).to_value
  end

  # Just for tests
  def self.blocking(&block)
    block.call
  end

end

if $0 == __FILE__
  require 'benchmark'
  def fib(n)
    Handler.fib
    n < 2 ? n : fib(n-1) + fib(n-2)
  end
  t = Benchmark.realtime do
    t1 = Thread.new { sleep 1; loop { STDOUT.write ".";  }}
    t2 = Thread.new { sleep 1; loop { STDOUT.write "x";  }}
    t3 = Thread.new { GVL.blocking { fib(36) } } # <<<<<<<<<<< switch GVL.blocking -> GVL.without_blocking
    t3.join
    [t1, t2].each(&:kill)
  end
  puts "in #{t}"
end

result.rb

# Blocking others threads, there is few time for scheduling
experiments $ ruby gvl.rb
......................................................................x.........xxx.x.xxxxxxxxxxxxx
in 2.798758

# Using a no blocking version you'll see that there is more time for other threads to run:
...................................................................................................
.x....xxxxxxx.xxxxxxxxxxxxxx..x.x..xxxx............xxxx........x.............xx.xxxxxxxxxxxxx....xx
xxxxxxxxxxxxxxxxxxx....x.x.......................xxxx..xxxxxxxxxxxxxxxxxxxxx....xx...xxxx......xxx.
xx.x.....x.xx..x..............xx.......x...xx.x.xx.........xxx.x....x..............................
............xxxx.x....xxx......x........xxxxxxxxxxxxxxxxxx...xxx.....xxx....xx...x.x...xxxxxxx.xxxx
xxxxxxxxx......xx...........xxx.................x...xx.................x.x.xxx........x.xxxxxxx.x..
xxx.xx....x...x..xx.........xxx...x.........x...................xxxx.....xxx.....x......xx.xxxxxxxx
xxxxxxxxxxxxxx..xxxxxxx..x............................xxx.x......xxxxxxxxxxxxxx........xxxxxxxxxxx.
...........x............xxxxxxxxxxxx.xx.x.........x......xxx..xx.xx...x......xxxxxxxxxxx.xx...xxx.x
x.....xxxxxxxxxx......xxx.........x.x...x.xxxxxxx.x.....xxxx....xx..xxx.xxx.xxxxxxxxx.......xxxxxx.
xxxxxxxx...............x.x.xxxxxx.xxxxxxxxxx..x.x.xx..xxxxxx.........xxx.x....x.xx..x.xxxx..x.x.xxx
.xxx................xxxx.x...x....xx.................xxxxxxxx.x.....x..xxxxxxx.....xxxxxxxxxxxxxxxx
x...x.x...xxxxxxx.xxxxxxxx..x....x..xxx...xxxx.x.xxx.x.xx...xxxxxx.xxxxxx..xxxx....xxxx.xxxxxx.xxxx
x...xxxx................x....x................xxx....xxxxxxxxxxxx.xxxxx..xxx.x.xxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxx...xxxxxxxx..................xxx.xxxxxxxxxxxxxxxxxxxx.xxx.xxxx.........
in 2.6518364