From: Gregory Brown <gregory.t.brown@...>
Date: 2007-08-12T12:38:05+09:00
Subject: Re: Interesting garbage collection article on LTU

On 8/11/07, John Joyce <dangerwillrobinsondanger@gmail.com> wrote:

> > And Linux is notoriously proud of the mantra "free memory is wasted
> > memory". It usually won't kick a page out to disk until it needs it
> > for
> > something else. So the resident set size of a Linux process/thread may
> > have little or nothing to do with its actual working set.
> >
> Might it not have something to do with the liberal use of symbols in
> Rails?
> AFAIK symbols don't get GC'd, or do they?

It's true that symbols can create memory leaks[0], but the tendency of
Rails to hog memory is mostly because its a big system that hasn't
necessarily been designed for performance.  Creating a bunch of
temporary objects without discarding them properly, using Array#shift
in Ruby 1.8, or leaving references to objects open in closures without
realizing it is more likely to make up a much more significant part of
what causes processes to balloon.

Also keep in mind that Rails keeps quite a bit of objects alive just
in normal use.  This is not something that will be easy to change.

That having been said, I'm sure there are places in the code base when
something like:

something.to_s == "foo"

could be used instead of:

something.to_sym == :foo

This would not be my first place to look for memory optimizations in
Rails though.

Saving my criticism for last, the OP as well as Ed didn't mention
Rails, and Ruby != Rails. :)

[0] http://www.oreillynet.com/ruby/blog/2006/04/nubygems_symbolic_starvation.html