[Ruby] Memory profiling with Rails

[Scott Laird]

On 8/15/06, Ryan Davis <ryand-ruby at zenspider.com> wrote:
>
> On Aug 15, 2006, at 11:50 AM, Scott Laird wrote:
>
> > One of the big things looming on the Typo Development Horizon is
> > reducing our memory footprint.  Even after closing all of the known
> > leaks, Typo is still growing too big--I've seen 60 MB dispatchers
> > after a couple days' use.
> >
> > Does anyone have any suggestions on how to best profile memory use
> > within Rails?  I'm planning on using something like this:
> >
> >   http://raggle.org/pipermail/raggle-dev/2003-August/000086.html
> >
> > But I'd love to discover that someone has a better tool for Ruby
> > memory tracking.  Even if it requires patching Ruby itself or
> > something similarly difficult.
>
> When I've done memory profiling it consisted of 1 thread, 2 hashes
> (curr, prev), classes as keys, and fixnums as values. No extra memory
> required if I can help it. Keep it as simple as possible. The code at
> the link above is WAY to complex for such a simple task. Try
> something like:
>
> def memory_profiler
>    Thread.new do
>      prev = Hash.new(0)
>      curr = Hash.new(0)
>      loop do
>        curr.clear
>        ObjectSpace.each_object do |o|
>          curr[o.class] += 1
>        end
>
>        curr.each do |k,v|
>          curr[k] -= prev[k]
>        end
>
>        puts "Top 20"
>        curr.sort_by { |k,v| -v }[0..19].each do |k,v|
>          printf "%+5d: %s\n", v, k.name unless v == 0
>        end
>
>        prev.clear
>        prev.update curr
>        sleep 2
>      end
>    end
> end
>
> It does use a sort_by, so that produces a bit extra junk... but that
> shouldn't be more than an extra array and hash per iteration.

Thanks, this helps.  I made a few small changes, and it looks like
Typo's action cache is leak-free, but non-cached pages leak a couple
strings per hit.  I'm sure that'll be a lot of fun to find :-(.


Scott