54 lines
2.0 KiB
Markdown
54 lines
2.0 KiB
Markdown
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date = "2011-09-24"
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title = "RSpec speed-up (24.6%) by tweaking ruby garbage collection"
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tags = ["Ruby", "Rails", "rspec", "speed", "garbage collection", "GC"]
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slug = "rspec-speed-up-by-tweaking-ruby-garbage-collection"
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[Today I learned][1] that Ruby garbage collection can be of huge importance to performance. More precisely, if Ruby does a lot of garbage collection it may slow down your code. Running garbage collection only every 10 or 20 seconds when running specs may increase performance dramatically.
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At this time specs for Ariejan.net take an average of 25.29s to run. This is not bad, but in my opinion faster specs are better. After tweaking ruby garbage collection I got my specs to run in 19.05s, a **24.6% speed increase**!
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[1]: http://37signals.com/svn/posts/2742-the-road-to-faster-tests
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~
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So, how do _you_ speed up _your_ tests?
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The key is that you don't want ruby to decide when to do garbage collection for you. Instead, we'll tell Ruby when to do this, and we'll let it do it every 15 seconds.
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To set this up for RSpec create a file `spec/support/deferred_garbage_collection.rb`:
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class DeferredGarbageCollection
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DEFERRED_GC_THRESHOLD = (ENV['DEFER_GC'] || 15.0).to_f
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@@last_gc_run = Time.now
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def self.start
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GC.disable if DEFERRED_GC_THRESHOLD > 0
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end
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def self.reconsider
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if DEFERRED_GC_THRESHOLD > 0 && Time.now - @@last_gc_run >= DEFERRED_GC_THRESHOLD
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GC.enable
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GC.start
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GC.disable
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@@last_gc_run = Time.now
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end
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end
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end
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Next, add the following to your `spec/spec_helper.rb` so rspec will use our deferred garbage collection.
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config.before(:all) do
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DeferredGarbageCollection.start
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end
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config.after(:all) do
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DeferredGarbageCollection.reconsider
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end
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Now, when you run `rake spec` you should see a nice speed increase. Try to alter the threshold value a bit to see what gives your best performance:
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DEFER_GC=20 rake spec
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Enjoy!
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