Пример программного снятия GVL. Оригинал статьи http://www.spacevatican.org/2012/7/5/whos-afraid-of-the-big-bad-lock/

cleaning_up.c

static void *rb_rdiscount_to_html_no_gvl(void * param_block){
  rb_discount_to_html_param_block *block = (rb_discount_to_html_param_block*)param_block;
  block->doc = mkd_string(block->input, block->input_length, block->flags);
  if(mkd_compile(block->doc, block->flags)){
    block->szres = mkd_document(block->doc, &block->res);
  }
  return NULL;
}

/*wrapper function. only exists because we need to pass a function pointer to rb_ensure*/
static VALUE rb_discount_to_html_no_gvl_wrapper(VALUE arg){
  rb_thread_blocking_region(rb_rdiscount_to_html_no_gvl, arg, NULL, NULL);
  return Qnil;
}

/*called after rb_discount_no_gvl_wrapper. cleanups up markdown resources and sticks the result in block->result)*/
static VALUE rb_discount_to_html_no_gvl_cleanup(VALUE arg){
  rb_discount_param_block *block = (rb_discount_to_html_param_block*)arg;
  if(block->szres !=EOF){
      block->result = rb_str_buf_new(block->szres+1);
      rb_str_cat(block->result, block->res, block->szres);
      rb_str_cat(block->result, "\n", 1);
  }
  else{
    block->result = rb_str_buf_new(1);
  }
  mkd_cleanup(block->doc);
  return Qnil;
}
static VALUE rb_rdiscount_to_html(int argc, VALUE *argv, VALUE self)
{
  /* boring setup*/;
  rb_ensure(rb_discount_to_html_no_gvl_wrapper, &block, rb_discount_to_html_no_gvl_cleanup, &block);

  /*encoding massaging omitted*/
  return block.result;
}

execution_result_1.txt

user     system      total        real
1 thread   6.420000   0.010000   6.430000 (  6.426911)
2 thread   6.430000   0.010000   6.440000 (  6.439822)
4 thread   6.380000   0.020000   6.400000 (  6.395870)

execution_result_2.txt

user     system      total        real
1 thread   6.250000   0.060000   6.310000 (  6.315216)
2 thread   6.730000   0.110000   6.840000 (  3.463594)
4 thread   7.520000   0.350000   7.870000 (  2.146914)

rb_thread_blocking_region.rb

rb_thread_blocking_region(do_some_work, argument, unblocker, unblocker_argument);

rdiscount.c

static void *rb_rdiscount_to_html_no_gvl(void * param_block){
  rb_discount_to_html_param_block *block = (rb_discount_to_html_param_block*)param_block;
  block->doc = mkd_string(block->input, block->input_length, block->flags);
  if(mkd_compile(block->doc, block->flags)){
    block->szres = mkd_document(block->doc, &block->res);
  }
}

static VALUE
rb_rdiscount_to_html(int argc, VALUE *argv, VALUE self)
{
  /* boring setup stuff */
  rb_thread_blocking_region(rb_rdiscount_to_html_no_gvl, (void*)&block, NULL, NULL);
  if(block.szres !=EOF){
    rb_str_cat(buf, block.res, block.szres);
    rb_str_cat(buf, "\n", 1);
  }
  mkd_cleanup(block.doc);
  /* boring cleanup */
  return buf;
}

simple_example.c

static VALUE rb_rdiscount_to_html(int argc, VALUE *argv, VALUE self) {
  /*boring setup stuff */
  MMIOT *doc = mkd_string(RSTRING_PTR(text), RSTRING_LEN(text), flags);
  if ( mkd_compile(doc, flags) ) {
    szres = mkd_document(doc, &res);

    if ( szres != EOF ) {
      rb_str_cat(buf, res, szres);
      rb_str_cat(buf, "\n", 1);
    }
  }
  mkd_cleanup(doc);
  /*boring cleanup */
  return buf;
}

simple_example_2.rb

require 'thread'
require 'benchmark'
require 'rdiscount'
include Benchmark
$content = []
Dir.glob('/Users/fred/markdown/*.markdown').each {|path| $content.push File.read path}

def parse_with_threads(count)
  q = Queue.new
  $content.each {|data| q.push data}
  count.times {q.push nil}
  threads = (1..count).collect do
    Thread.new do
      while s = q.pop
        RDiscount.new(s).to_html
      end
    end
  end
  threads.each {|th| th.join}
end

bmbm(5) do |x|
  x.report("1 thread") { 40.times {parse_with_threads 1}}
  x.report("2 thread") { 40.times {parse_with_threads 2}}
  x.report("4 thread") { 40.times {parse_with_threads 4}}
end