131% faster Ruby tests, no new code needed

Some speed improvements on a Rails app test suite, about 100 assertions.

Initial state – Ruby 1.9.3-p448:

Total run time: 37s

First improvement – Ruby 1.9.3-p448 with Railsexpress patches:

Total run time: 31s

Improvement from initial state: +20%

Second improvement – Ruby 2.0.0-p247:

Total run time: 24s

Improvement from initial state: +54%

Last improvement – Ruby 2.0.0-p247 with GC tuning:

Total run time: 21s

Improvement from initial state: +75% !

Now I need to further tune the GC, I think I can double the original speed :)

Update:

I just installed ruby-2.0.0-head (right now, p290), and got even better results!

Total run time: 16s

Improvement from initial state: +131% !!!

And I still have to tune the GC...

Does anybody know what has changed between 2.0.0-p247 and 2.0.0-p290 to warrant the speed improvement?

Bonus! (this one touches code though) – feat. Stefan Kaes

The following code makes it so that the Rails env is initialized once for all the test suites, instead of three times (one per suite):

4	4
5	5	require File.expand_path('../config/application', __FILE__)
6	6
7		-XXX::Application.load_tasks
		\ No newline at end of file
	7	+XXX::Application.load_tasks
	8	+
	9	+namespace :test do
	10	+  Rake::TestTask.new(:all) do |t|
	11	+    t.libs << "test"
	12	+    t.pattern = 'test/{lib,scripts,unit,functional,integration}/**/*_test.rb'
	13	+    t.verbose = true
	14	+  end
	15	+  tsk = Rake::Task['test:all']
	16	+  tsk.enhance(['test:prepare'])
	17	+  tsk.comment = "Run all tests in one go"
	18	+end
	19	+
	20	+Rake::Task['default'].clear_prerequisites
	21	+Rake::Task['default'].enhance ["test:all"]