Rails Optimization @RailsConf
By Steph Skardal
May 7, 2009
On the second day of RailsConf 2009, I attended a talk on Advanced Performance Optimization of Rails Applications. Although it was reminiscent of college as I felt compelled to write down and memorize lots of trivial information, I appreciate that I can actually apply the information. Below is a performance checklist for advanced optimization techniques covered in the talk.
Rails optimization:
- Use eager loading (investigate the virtual attributes plugin)
- Avoid string callbacks
- Minimize view instances of the object and use template inlining. Objects passed through partials can add up and be expensive.
Ruby optimization:
- Date is 16* slower than Time
- Use Date::Performance
- Avoid the string+= method, Use string« method instead
- Compare like objects—comparing different types of objects is expensive.
Database optimization:
- Use explain analyze
- Use any(array ()) instead of in()
- Push conditions into subselects and joins—postgresql doesn’t do that for you.
Environment Optimization:
- Buy more memory, optimize memory, set memory limits for mongrel (with monit)
- Competing for memory cache is expensive on a shared server (must avoid database in cold state)
- Use live debugging tools such as strace, oprofile, dtrace, monit, nagios
- Pay attention to load balancing
User Environment Optimization:
- Listen to yslow
- Inherently slow javascript functions are eval, DOM selectors, css selectors, element.style changes, getElementById, getElementByName, style switching.
Other Topics:
Some final tips from the presentation were get benchmarks, use profiling tool like ‘ruby-prof’, optimize memory, pay attention to the garbage collection methods for the language, profile memory and measure! measure! measure!!!
Probably more important than the optimization details covered, the presentation served more valuable to remind me of the following:
Pay attention to all potential areas for optimization. As I’ve grown as a developer I’ve continued to add to my “optimization checklist”.
When learning a new language, don’t forget to pay attention to the the little details of the language. I should appreciate specific points that make a language unique from other languages, including inherently expensive functions.
Like other developers, sometimes I produce code to meet the performance criteria, but I don’t have the luxury to spend time examining every area for optimization. I’d like to spend more time throughout a project paying attention to each of these points on my optimization checklist—and always work on doing it better the second time around.
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