[ruby-core:114149] [Ruby master Bug#18572] Performance regression when invoking refined methods

13 Jul 2023

      Issue #18572 has been updated by shugo (Shugo Maeda).

shugo (Shugo Maeda) wrote in #note-10:
...
Eregon (Benoit Daloze) wrote in #note-9:
...
From https://bugs.ruby-lang.org/issues/14083#note-3 it seems part of the problem at least is CRuby currently implements what I would call invalid usages of refinements (different set of activates refinements over time for a given call site), and that basically means extra checks and overhead, e.g., for a method which was refined once, even if there are no refinements active in the current scope.
If it's needed to fix the performance issue, it may be acceptable to raise exceptions in some cases (but I don't know the exact condition of such cases).
@ko1, @matz What do you think?
It's simple to prohibit using calls in blocks, but it will break backward compatibility, e.g., using in module_eval.
I and @ko1 discussed it at today's developer meeting, and concluded that there is no need to change the behavior to fix the performance regression.
@eregon Could you create another issue if you would like to change the behavior?

----------------------------------------
Bug #18572: Performance regression when invoking refined methods
https://bugs.ruby-lang.org/issues/18572#change-103827

* Author: palkan (Vladimir Dementyev)
* Status: Assigned
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Since Ruby 3.0, defining a refinement for a method slows down its execution even if we do not activate the refinement:

```ruby
require "benchmark_driver"

source = <<~RUBY
class Hash
  def symbolize_keys
    transform_keys { |key| key.to_sym rescue key }
  end
  def refined_symbolize_keys
    transform_keys { |key| key.to_sym rescue key }
  end
end
module HashRefinements
  refine Hash do
    def refined_symbolize_keys
      raise "never called"
    end
  end
end
HASH = {foo: 1, bar: 2, baz: 3}
class Foo
  def original
  end
  def refined
  end
end
module FooRefinements
  refine Foo do
    def refined
      raise "never called"
    end
  end
end
FOO = Foo.new
RUBY

Benchmark.driver do |x|
  x.prelude %Q{
    #{source}
  }
  x.report "#symbolize_keys original", %{ HASH.symbolize_keys }
  x.report "#symbolize_keys refined", %{ HASH.refined_symbolize_keys }
end

Benchmark.driver do |x|
  x.prelude %Q{
    #{source}
  }
  x.report "no-op original", %{ FOO.original }
  x.report "no-op refined", %{ FOO.refined }
end
```

The results for Ruby 3.1:

```sh
...

Comparison:
#symbolize_keys original:   2372420.1 i/s 
 #symbolize_keys refined:   1941019.0 i/s - 1.22x  slower

...

Comparison:
      no-op original:  51790974.2 i/s 
       no-op refined:  14456518.9 i/s - 3.58x  slower
```

For Ruby 2.6 and 2.7:

```sh
Comparison:
#symbolize_keys original:   2278339.7 i/s 
 #symbolize_keys refined:   2264153.1 i/s - 1.01x  slower

...

Comparison:
       no-op refined:  64178338.5 i/s 
      no-op original:  63357980.1 i/s - 1.01x  slower
```

You can find the full code and more results in this [gist](https://gist.github.com/palkan/637dc83edd86d70b5dbf72f2a4d702e5).

P.S.  The problem was originally noticed by @byroot, see https://github.com/ruby-i18n/i18n/pull/573

-- 
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