[ruby-core:52090] [ruby-trunk - Feature #7816] Don't invalidate method caches when defining a new method on a class without subclasses

Issue #7816 has been updated by marcandre (Marc-Andre Lafortune).

Subject changed from Don't invalidate method caches when defining a new method on a class without subclasses to Don't invalidate method caches when defining a new method on a class without subclasses

Speed boosts sounds awesome, especially the 15% rails bootup time, since the example is a bit contrived.

It would have been great to get this in 2.0.0

I'd split the new API from the patch; personally I'm not convinced of the usefulness of Class#has_subclass?  or of RubyVM.state_version
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Feature #7816: Don't invalidate method caches when defining a new method on a class without subclasses
https://bugs.ruby-lang.org/issues/7816#change-36105

Author: charliesome (Charlie Somerville)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: next minor


=begin
Attached is a patch that avoids incrementing the VM state version when defining a method and these conditions are true:

* The method is not a redefinition of an existing method in the same class or any superclass
* The class has no subclasses
* The class is not a module

This means that defining singleton methods on objects no longer invalidates every method cache. This will significantly improve performance of code that defines singleton methods at runtime (eg. when using OpenStruct)

In my testing, a fresh Rails app boots about 15% faster (~1.7 sec down to ~1.4 sec).

This controller action can do ~440 requests per second with my patch, compared to ~320 requests per second without my patch.

  class HomeController < ApplicationController
    def index
      OpenStruct.new a: 1, b: 2
      render text: "home"
    end
  end

Of course these numbers will vary between apps, but I think this is a good start in improving the performance of a very common use case in Ruby.
=end


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