Reduce memory allocation on TypeName#initialize

[pocke]

This PR improves the performance of initializing TypeName. It improves loading an environment.

This PR reduces 9% execution time.

Profiling

StackProf

code

require 'rbs'
require 'stackprof'

def subject
  loader = RBS::EnvironmentLoader.new
  RBS::Environment.from_loader(loader).resolve_type_names
end

StackProf.run(mode: :wall, out: "tmp/stackprof-environment-load-#{Time.now.to_f}") do
  40.times do
    subject
  end
end

result

$ stackprof tmp/stackprof-environment-load-1689829686.8585012 -m 'RBS::TypeName#initialize'
RBS::TypeName#initialize (/Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:9)
  samples:    61 self (1.4%)  /    185 total (4.3%)
  callers:
     102  (   55.1%)  RBS::Parser._parse_signature
      83  (   44.9%)  Class#new
  callees (124 total):
      99  (   79.8%)  Regexp#===
      19  (   15.3%)  Symbol#to_s
       6  (    4.8%)  String#[]
  code:
                                  |     9  |     def initialize(namespace:, name:)
    6    (0.1%) /     6   (0.1%)  |    10  |       @namespace = namespace
   13    (0.3%) /    13   (0.3%)  |    11  |       @name = name
   43    (1.0%) /    18   (0.4%)  |    12  |       @kind = case name.to_s[0,1]
  114    (2.6%) /    20   (0.5%)  |    13  |               when /[A-Z]/
    1    (0.0%) /     1   (0.0%)  |    14  |                 :class
    8    (0.2%) /     3   (0.1%)  |    15  |               when /[a-z]/
                                  |    16  |                 :alias

It indicates TypeName#initialize consumes 4.3% execution time.

MemoryProfiler

code

require 'rbs'
require 'memory_profiler'

def subject
  loader = RBS::EnvironmentLoader.new
  RBS::Environment.from_loader(loader).resolve_type_names
end

report = MemoryProfiler.report do
  subject
end

report.pretty_print

part of result

allocated memory by location
-----------------------------------
  16711810  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/parser_aux.rb:17
   2033824  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:13
   1896399  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/environment_loader.rb:144
    881200  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:12

allocated objects by location
-----------------------------------
    155956  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/parser_aux.rb:17
     22030  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:12
     19556  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:13

Allocated String Report
-----------------------------------
      4162  "E"
      2083  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:12
      2079  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:13

      3775  "S"
      1887  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:12
      1887  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:13
         1  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/parser_aux.rb:17

      3610  "I"
      1807  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:12
      1803  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:13

      1372  "Integer"
      1372  /Users/kuwabara.masataka/ghq/github.com/ruby/rbs/lib/rbs/type_name.rb:12

It indicates TypeName#initialize allocates many strings.

Benchmark

require 'rbs'
require 'benchmark'

def subject
  loader = RBS::EnvironmentLoader.new
  RBS::Environment.from_loader(loader).resolve_type_names
end

Benchmark.bmbm(20) do |x|
  x.report do
    40.times do
      subject
    end
  end
end

before

$ ruby -v bench.rb
ruby 3.2.2 (2023-03-30 revision e51014f9c0) [arm64-darwin21]
Rehearsal --------------------------------------------------------
                       3.109180   0.101717   3.210897 (  3.256885)
----------------------------------------------- total: 3.210897sec

                           user     system      total        real
                       3.212283   0.103555   3.315838 (  3.339915)

after

$ ruby -v bench.rb
ruby 3.2.2 (2023-03-30 revision e51014f9c0) [arm64-darwin21]
Rehearsal --------------------------------------------------------
                       3.250580   0.104434   3.355014 (  3.406756)
----------------------------------------------- total: 3.355014sec

                           user     system      total        real
                       2.909117   0.098380   3.007497 (  3.031184)

It reduces 9% execution time in this benchmark script.
I also tested on a large Rails app and got the same improvement (reducing 9% execution time).

Implementation note

I used Symbol#match? instead of Symbol#start_with? because Symbol#match? is faster than #start_with? because #start_with? creates a MatchData.

[soutaro]

Looks good. Looks like test is failing because of 2.x?

[pocke]

Yes, Ruby 2.6 does not have Symbol#start_with? so the CI is failing.

I'll rebase this PR on the master branch, write the PR description, then merge this PR.