Add basic memory usage profile (#1137)

This commit:

- adds a rake task to profile basic memory usage; and
- configures Travis to perform a memory usage profile on CI builds.

.travis.yml

@@ -8,10 +8,15 @@ rvm:
   - "2.3"
   - "2.4"
   - "2.5"
-  - "2.6"
+  - &latest_ruby "2.6"
 cache:
   bundler: true
 bundler_args: --without development
 script:
   - bundle exec rake
   - bundle exec rubocop
+matrix:
+  include:
+    - rvm   : *latest_ruby
+      name  : Profile Memory Allocation
+      script: bundle exec rake profile_memory

Gemfile

@@ -15,6 +15,11 @@ gem 'rubocop', '~> 0.49.1'
 # don't try to install redcarpet under jruby
 gem 'redcarpet', :platforms => :ruby
 
+# Profiling
+if RUBY_VERSION >= '2.3.0'
+  gem 'memory_profiler', :require => false
+end
+
 group :development do
   gem 'pry'
 

Rakefile

@@ -39,3 +39,34 @@ task :default => :spec
 Dir.glob(Pathname.new(__FILE__).dirname.join('tasks/*.rake')).each do |f|
   load f
 end
+
+task :profile_memory do
+  lib = File.expand_path("lib", __dir__)
+  $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+
+  require 'memory_profiler'
+
+  source = File.expand_path('lib/rouge/lexer.rb', __dir__)
+  sample = File.read(source, encoding: 'utf-8')
+  report = MemoryProfiler.report do
+    require 'rouge'
+    formatter = Rouge::Formatters::HTML.new
+    lexer     = Rouge::Lexers::Ruby.new
+    formatter.format(lexer.lex(source))
+  end
+  print_options = { :scale_bytes => true }
+
+  if ENV['CI']
+    report.pretty_print(print_options)
+  else
+    results_file = File.expand_path('rouge-memory.tmp')
+    t_allocated = report.scale_bytes(report.total_allocated_memsize)
+    t_retained  = report.scale_bytes(report.total_retained_memsize)
+    puts
+    puts "Total allocated: #{t_allocated} (#{report.total_allocated} objects)"
+    puts "Total retained:  #{t_retained} (#{report.total_retained} objects)"
+    report.pretty_print(print_options.merge(to_file: results_file))
+    puts
+    puts "Detailed report saved to file: #{results_file}"
+  end
+end