Speed up RSpec by deferring garbage collection
Update: This trick probably isn't very useful anymore in Ruby 2.x. The Ruby GC has improved a lot over the years.
Joe Van Dyk discovered that running the Ruby garbage collector only every X seconds can speed up your tests. I found that deferring garbage collection would speed up my RSpec examples by about 15%, but it probably depends on the nature of your tests. I also tried applying it to Cucumber features, but found no performance improvements.
Since Joe is using Test::Unit in his example, here is how to apply the same trick to RSpec.
First, copy this class to
class DeferredGarbageCollection DEFERRED_GC_THRESHOLD = (ENV['DEFER_GC'] || 10.0).to_f @@last_gc_run = Time.now def self.start GC.disable if DEFERRED_GC_THRESHOLD > 0 end def self.reconsider if DEFERRED_GC_THRESHOLD > 0 && Time.now - @@last_gc_run >= DEFERRED_GC_THRESHOLD GC.enable GC.start GC.disable @@last_gc_run = Time.now end end end
Then, in your
spec_helper.rb, configure RSpec like seen below. Note that you might already have code hooked up to
after(:all), so merge it together:
Spec::Runner.configure do |config| config.before(:all) do DeferredGarbageCollection.start end config.after(:all) do DeferredGarbageCollection.reconsider end end
You can now enjoy faster specs.