From: ara.t.howard@...
Date: 2006-10-27T00:53:52+09:00
Subject: Re: debugging memory use and GC

On Fri, 27 Oct 2006, Rick DeNatale wrote:

> On 10/25/06, snacktime <snacktime@gmail.com> wrote:
>> What is a good way to find out what objects are not being GC'd ?  I am
>> seeing a strange pattern I can't figure out.  The app is handling
>> large files and will use up to 150mb or so of memory and then when I
>> call GC.start it goes back down to around 8mb.  But after a few cycles
>> memory stops being reclaimed.
>
> Of course, what you really want to know is not just what's not getting
> GCed but WHY.
>
> This can be a difficult problem.  You really want to find the
> reference paths from root objects.
>
> Some GC languages like Smalltalk have methods in object to get a list
> of everything which references it. I haven't seen such a facility in
> Ruby.  Then the problem with this is that calling this method
> generates additional references to the objects referencing the object
> etc.  This kind of heisenberg effect makes building a tool to find
> reference paths difficult.

it would be expensive, but i wonder of dumping the objects in objectspace
might be useful - since Marshal.dump already follows all references it seems
like a custom _dump method on object which could all themselves to a tree
might do the trick.  in otherwords, if you dumped an object with a global tree
in contect then all objects being dumped as a result would add themselves to
this tree.  after the dump, you simply keep a copy of the tree...

just a thought...

-a
-- 
my religion is very simple.  my religion is kindness. -- the dalai lama