Demonstration of object allocation improvements in RSpec 3.2

README.md

This repository demonstrates the difference in object allocations between rspec-core 3.1 and 3.2. See output for the results of running example_spec.rb while tracking object allocations on 3.1 and 3.2.

• 3.1: 134745
• 3.2: 91816
• Difference: 42929

That's a 31.9% reduction in allocations between RSpec 3.1 and 3.2.

example_spec.rb

require 'allocation_stats'
require 'rspec/core'

stats = AllocationStats.new.trace do
  10.times do |i|
    RSpec.describe "Group #{i}" do
      10.times do |j|
        it("example #{j}") { }

        context "nested group #{j}" do
          10.times do |k|
            it("example #{k}") { }
          end
        end
      end
    end
  end

  RSpec::Core::Runner.invoke
end

puts stats.allocations.group_by().to_text

Gemfile-3-1

source "https://rubygems.org"

gem 'rspec-core', "~> 3.1.7"
gem 'allocation_stats'

Gemfile-3-1.lock

GEM
  remote: https://rubygems.org/
  specs:
    allocation_stats (0.1.5)
    rspec-core (3.1.7)
      rspec-support (~> 3.1.0)
    rspec-support (3.1.2)

PLATFORMS
  ruby

DEPENDENCIES
  allocation_stats
  rspec-core (~> 3.1.7)

Gemfile-3-2

source "https://rubygems.org"

gem 'rspec-core', "~> 3.2.0"
gem 'allocation_stats'

Gemfile-3-2.lock

GEM
  remote: https://rubygems.org/
  specs:
    allocation_stats (0.1.5)
    rspec-core (3.2.0)
      rspec-support (~> 3.2.0)
    rspec-support (3.2.0)

PLATFORMS
  ruby

DEPENDENCIES
  allocation_stats
  rspec-core (~> 3.2.0)

output

➜  rspec-allocations git:(master) time BUNDLE_GEMFILE=Gemfile-3-1 bundle exec ruby example_spec.rb
............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

Finished in 0.20442 seconds (files took 0.23812 seconds to load)
1100 examples, 0 failures
count
-----
  134745
BUNDLE_GEMFILE=Gemfile-3-1 bundle exec ruby example_spec.rb  1.45s user 0.13s system 99% cpu 1.590 total
➜  rspec-allocations git:(master) time BUNDLE_GEMFILE=Gemfile-3-2 bundle exec ruby example_spec.rb
............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

Finished in 0.20653 seconds (files took 0.18637 seconds to load)
1100 examples, 0 failures

count
-----
  91816
BUNDLE_GEMFILE=Gemfile-3-2 bundle exec ruby example_spec.rb  1.21s user 0.11s system 99% cpu 1.329 total