Allocate the "ruby" and "\0" Strings once.

[jrafanie]

Index#search is called many times so this change is worth it.

With a single gem in your Gemfile, this change drops the string
allocations by nearly 30,000.

Script:

require 'allocation_tracer'

ObjectSpace::AllocationTracer.setup(%i{path line type})

result = ObjectSpace::AllocationTracer.trace do
  begin
    require 'bundler/inline'
  rescue LoadError => e
    $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
    raise e
  end

  gemfile(true) do
    source 'https://rubygems.org'
    gem 'benchmark-ips'
  end
end

result.sort_by{|k, v| k}.each{|k, v|
  puts ([v[0]]+k).join("\t")
}

String allocations before:

$ruby benchmark_allocations.rb | grep T_STRING | sort -nr | head -n 10
65461 /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb  54  T_STRING
64982 /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/version.rb  163 T_STRING
29986 /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/index.rb 71  T_STRING
22142 /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/spec_set.rb  111 T_STRING
20457 /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/version.rb  225 T_STRING
5280  /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/index.rb 87  T_STRING
4848  /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/requirement.rb  92  T_STRING
4708  /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/lockfile_parser.rb 54  T_STRING
4608  /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/version.rb  282 T_STRING
4561  /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/index.rb 19  T_STRING

String allocations after:

$ ruby benchmark_allocations.rb | grep T_STRING | sort -nr | head -n 10
65479 /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb  54  T_STRING
64143 /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/version.rb  163 T_STRING
22142 /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/spec_set.rb  111 T_STRING
20407 /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/version.rb  225 T_STRING
5280  /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/index.rb 90  T_STRING
4916  /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/requirement.rb  92  T_STRING
4730  /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/lockfile_parser.rb 54  T_STRING
4608  /Users/joerafaniello/.rubies/ruby-2.2.3/lib/ruby/2.2.0/rubygems/version.rb  282 T_STRING
4561  /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/index.rb 22  T_STRING
3334  /Users/joerafaniello/.gem/ruby/2.2.3/gems/bundler-1.10.6/lib/bundler/spec_set.rb  134 T_STRING

[segiddins]

Instead of a constant, could we just freeze the string literals?

[jrafanie]

Yes @segiddins, thanks for the review!

We can do that but only ruby 2.1, 2.2+ will benefit since they're the only rubies that will use the same single shared frozen string: http://tmm1.net/ruby21-fstrings/

The constant way will work with older and newer rubies AFAIK.

[jrafanie]

I have no attachment to using constants. I thought bundler favored backward compatible changes and in this case, I didn't think the "new shiny" way was that much better to warrant excluding ruby 2.0 and below from the "fun". 😉

[segiddins]

Ah, had no idea the interned frozen strings were new! In that case, frozen constants sounds good :)

[jrafanie]

Thanks @segiddins, updated.

[segiddins]

@homu r+

[homu]

📌 Commit e20d286 has been approved by segiddins

[homu]

⌛ Testing commit e20d286 with merge b0eab63...

[homu]

☀️ Test successful - status