From: "palkan (Vladimir Dementyev) via ruby-core" <ruby-core@...>
Date: 2023-02-24T21:15:41+00:00
Subject: [ruby-core:112579] [Ruby master Bug#18572] Performance regression when invoking refined methods

Issue #18572 has been updated by palkan (Vladimir Dementyev).





Eregon (Benoit Daloze) wrote in #note-3:

> Interesting, maybe this is partly the cause for the `13 seconds` mentioned in https://shopify.engineering/the-case-against-monkey-patching.



As far as I understand, this line is responsible for "the 13 seconds" boot time overhead: https://github.com/ruby/ruby/blob/master/eval.c#L1342 (I was able to achieve similar results by adding tons of `using` to the source code). The line was added in the same commit as mentioned above, so the root cause is the same for sure.



> Maybe we should deprecate refinements: my main concern about them is it's a ton of complexity in Ruby implementations (in method lookup and even worse in super method lookup) and it's not really used much or gains much, so it does not seem worth it. It does make every uncached/cache-filling method lookup slower.

> It shouldn't make cached method lookup slower though when no refinements are active in that scope, at least it does not currently in TruffleRuby.



But that wasn't the case in Ruby <3; refined methods were fast (b/c cached), and had no effect on the original method calls, like today. I believe, something just got lost along the introduction of disposable call-caches.



The problem with "it's not really used much or gains much" is that it took many years for refinements to reach some sort of stability (2.6 and 2.7 releases were pretty good) and finally developers were convinced not to be afraid of the "experimentality" of the feature, and with Ruby 3 we made a huge step back. Especially now, when Shopify engineers claim that "refinements are really slow!" (which is only partially true), we, for sure, should expect the community to turn backs on refinements, again. 



It's a two-edged sword �������������



----------------------------------------

Bug #18572: Performance regression when invoking refined methods

https://bugs.ruby-lang.org/issues/18572#change-102028



* 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







-- 

https://bugs.ruby-lang.org/

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