Make rbs validate faster

[pocke]

This pull request improves the performance of DefiniitonBuilder for rbs validate.

How

RBS::DefinitionBuilder#merge_method is slow (see the profiling section). Because the method creates new object for all method types with sub method.

This pull request reduces method calls of sub method.
sub method replaces type parameters, so it is not necessary if the type parameter mapping is empty.

Behavior change

It changes behavior of instance type. Previously instance type is replaced with Types::Bases::Instance.new(location: nil) with Substitution.

rbs/lib/rbs/substitution.rb

Line 14 in 77aaea0

def self.build(variables, types, instance_type: Types::Bases::Instance.new(location: nil), &block)

But it will be not changed by this patch.

I think it is not a problem because the previous behavior only changes location actually. The location will be kept, but I guess it is not affect anything.

Benchmark

I used https://github.com/pocke/rbs_rails for the benchmark because it contains large RBS files.

$ rbs -rlogger -rpathname -rmutex_m -Isig -Iassets/sig validate > /dev/null

before: 15.85s
after: 4.20s

3.77x faster 🚀

Profiling

I used stackprof for the above command, and got the following result.

$ stackprof stackprof-out --sort-total
==================================
  Mode: cpu(1000)
  Samples: 4643 (1.11% miss rate)
  GC: 2141 (46.11%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
      2502  (53.9%)           0   (0.0%)     <top (required)>
      2502  (53.9%)           0   (0.0%)     <top (required)>
      2502  (53.9%)           0   (0.0%)     Object#exec_command
      2502  (53.9%)           0   (0.0%)     Object#exec
      2502  (53.9%)           0   (0.0%)     Object#main
      2502  (53.9%)           0   (0.0%)     <top (required)>
      2502  (53.9%)           0   (0.0%)     <main>
      2502  (53.9%)           0   (0.0%)     <main>
      2494  (53.7%)           1   (0.0%)     RBS::CLI#run_validate
      2494  (53.7%)           0   (0.0%)     RBS::CLI#run
      2197  (47.3%)           0   (0.0%)     Kernel#tap
      2141  (46.1%)          16   (0.3%)     (garbage collection)
      1977  (42.6%)           4   (0.1%)     RBS::DefinitionBuilder#try_cache
      1780  (38.3%)           7   (0.2%)     RBS::DefinitionBuilder#merge_definitions
      1743  (37.5%)          42   (0.9%)     RBS::DefinitionBuilder#merge_method
      1627  (35.0%)        1627  (35.0%)     (marking)
      1422  (30.6%)          10   (0.2%)     RBS::MethodType#sub
      1288  (27.7%)           4   (0.1%)     RBS::DefinitionBuilder#build_singleton
      1168  (25.2%)          11   (0.2%)     RBS::MethodType#map_type
      1167  (25.1%)          26   (0.6%)     Kernel#yield_self
       931  (20.1%)         152   (3.3%)     RBS::Types::Function#map_type
       689  (14.8%)           2   (0.0%)     RBS::DefinitionBuilder#build_instance
       498  (10.7%)         498  (10.7%)     (sweeping)
       350   (7.5%)          58   (1.2%)     RBS::Types::Function::Param#map_type
       331   (7.1%)           1   (0.0%)     RBS::EnvironmentLoader#load
       331   (7.1%)           0   (0.0%)     RBS::Environment.from_loader
       313   (6.7%)         313   (6.7%)     Kernel#class
       312   (6.7%)           0   (0.0%)     Racc::Parser#do_parse
       312   (6.7%)           0   (0.0%)     RBS::Parser.parse_signature
       262   (5.6%)          67   (1.4%)     RBS::Substitution#without

We can confirm RBS::DefinitionBuilder#merge_method takes 37.5% exetuion time.

[soutaro]

🚀