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#6695 ✓committed

Dramatic rendering slowdown from 3.0.3 to 3.0.6

Reported by stiang | April 12th, 2011 @ 11:49 AM | in 3.0.6

I am experiencing a 10x slowdown on some pages when upgrading from 3.0.3 to 3.0.6.

3.0.3: Completed 200 OK in 1332ms (Views: 1261.9ms | ActiveRecord: 61.2ms)
3.0.6: Completed 200 OK in 12668ms (Views: 12629.0ms | ActiveRecord: 25.4ms)

This is a page that renders a whole lot of partials, maybe 50-100 (one for each record). Regular pages, with a limited number of partials, seem less slow. The slowdown is apparent in both the development and production environments.

Please let me know if I should provide additional information.

Comments and changes to this ticket

  • Santiago Pastorino

    Santiago Pastorino April 13th, 2011 @ 04:55 PM

    • State changed from “new” to “open”
    • Milestone set to 3.0.6
    • Assigned user set to “Santiago Pastorino”
    • Importance changed from “” to “Low”

    Can you check if reverting this commit fix your issue?

  • stiang

    stiang April 14th, 2011 @ 07:45 AM

    Indeed it does, Santiago, specifically the changes to activerecord/lib/active_record/attribute_methods/read.rb. Reverting those makes my app perform as it did with 3.0.3 (or even a little better, it seems).

  • stiang

    stiang April 14th, 2011 @ 02:12 PM

    I’ve investigated this a bit more and come to the conclusion that rescue is extremely expensive on ruby 1.8. When I run this gist I get the following results on my machine:

    Showing results for 1000000 method calls
    Method IS NOT defined
    With rescue:      10.35 seconds
    With respond_to:  0.64 seconds
    Direct call:      0.35 seconds
    Method IS defined
    With rescue:      0.57 seconds
    With respond_to:  0.85 seconds
    Direct call:      0.35 seconds

    Unless I’m misunderstanding something, it would appear that changing

    def read_attribute(attr_name)
      send "_#{attr_name}"
    rescue NoMethodError
      _read_attribute attr_name

    in read.rb to something like

    def read_attribute(attr_name)
      if respond_to? "_#{attr_name}"
       send "_#{attr_name}"
        _read_attribute attr_name

    should improve the speed dramatically when the underscore method doesn’t exist, and only add a slight penalty (the respond_to call) when it does. Any thoughts?

  • stiang

    stiang April 14th, 2011 @ 04:00 PM

    I added a pull request for this change after verifying that the tests pass with it.

    (Actually, this test failed, but that appears to be wholly unrelated to my change.)

  • Santiago Pastorino

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