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Perf: save ~9% of object allocations on heavy requests.

The per-thread registry is keyed on the class name, and each request for
the class name returns a new string. This is in the hot path for a lot
of Active Record behavior, so we easily accumulate thousands of repeated

To fix, we simply cache the key when the class is first extended with
the module.

TODO: Eliminate this module. The per-thread instance concept is common,
but this technique confuses and obfuscates.
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1 parent 1792293 commit b474d06d5ea646c8145b07c8acbf1181c9e0b2aa @jeremy jeremy committed Dec 13, 2013
Showing with 5 additions and 2 deletions.
  1. +5 −2 activesupport/lib/active_support/per_thread_registry.rb
7 activesupport/lib/active_support/per_thread_registry.rb
@@ -32,12 +32,15 @@ module ActiveSupport
# If the class has an initializer, it must accept no arguments.
module PerThreadRegistry
+ def self.extended(object)
+ object.instance_variable_set '@per_thread_registry_key',
+ end
def instance
- Thread.current[name] ||= new
+ Thread.current[@per_thread_registry_key] ||= new
def method_missing(name, *args, &block) # :nodoc:
# Caches the method definition as a singleton method of the receiver.
define_singleton_method(name) do |*a, &b|

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