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comp.lang.ruby

Debugging garbage collection

elbows

9/13/2003 10:24:00 PM

I have a Ruby program that seems to be leaking memory -- in the sense
that objects which I think should be GCed aren't getting GCed (even if
I call GC.start).
Something must be keeping references to these objects, but I can't
figure out what.

Are there any tools to debug this problem? Some way to watch the GC in
operation, or to find references to a particular object (at runtime),
would be helpful.

Nathan
3 Answers

Hal E. Fulton

9/13/2003 10:45:00 PM

0

Nathan Weston wrote:
> I have a Ruby program that seems to be leaking memory -- in the sense
> that objects which I think should be GCed aren''t getting GCed (even if
> I call GC.start).
> Something must be keeping references to these objects, but I can''t
> figure out what.
>
> Are there any tools to debug this problem? Some way to watch the GC in
> operation, or to find references to a particular object (at runtime),
> would be helpful.

I''m not aware of any such GC debugging tools.

I guess the obvious question (to me) is: What behavior makes you think
that objects aren''t getting collected?

Hal

Joel VanderWerf

9/14/2003 8:59:00 PM

0

Nathan Weston wrote:
> I have a Ruby program that seems to be leaking memory -- in the sense
> that objects which I think should be GCed aren''t getting GCed (even if
> I call GC.start).
> Something must be keeping references to these objects, but I can''t
> figure out what.
>
> Are there any tools to debug this problem? Some way to watch the GC in
> operation, or to find references to a particular object (at runtime),
> would be helpful.

You can patch gc.c and variable.c to give some information. See

http://redshift.sourceforge.net/deb...

The patches there are for 1.6.7 and 1.7.2, unfortunately. I haven''t had
the need to update them.

What it gives you is a method you can call like:

GC.reachability_paths(obj)

and it will return an array of arrays, each of which is a path starting
from some root reference in the interpreter, and ending with an object
that contains a reference to obj. The root references can be ruby
objects or can be references on the stack or in globals, and those are
reported in descriptive strings, like

"frame <number>: <filename> line <number>"
"Ruby global <varname>"
"C global <varname>"

elbows

9/15/2003 1:18:00 AM

0

Thanks, that sounds like just what I need. I''ll give it a try.

Nathan

Joel VanderWerf <vjoel@PATH.Berkeley.EDU> wrote in message news:<3F64D69F.4070500@path.berkeley.edu>...
> Nathan Weston wrote:
> > I have a Ruby program that seems to be leaking memory -- in the sense
> > that objects which I think should be GCed aren''t getting GCed (even if
> > I call GC.start).
> > Something must be keeping references to these objects, but I can''t
> > figure out what.
> >
> > Are there any tools to debug this problem? Some way to watch the GC in
> > operation, or to find references to a particular object (at runtime),
> > would be helpful.
>
> You can patch gc.c and variable.c to give some information. See
>
> http://redshift.sourceforge.net/deb...
>
> The patches there are for 1.6.7 and 1.7.2, unfortunately. I haven''t had
> the need to update them.
>
> What it gives you is a method you can call like:
>
> GC.reachability_paths(obj)
>
> and it will return an array of arrays, each of which is a path starting
> from some root reference in the interpreter, and ending with an object
> that contains a reference to obj. The root references can be ruby
> objects or can be references on the stack or in globals, and those are
> reported in descriptive strings, like
>
> "frame <number>: <filename> line <number>"
> "Ruby global <varname>"
> "C global <varname>"