From: "Mauricio Fernández" <batsman.geo@...>
Date: 2002-08-29T09:06:58+09:00
Subject: Re: Temporary VALUE Needs to Be Protected?

On Thu, Aug 29, 2002 at 08:51:44AM +0900, Christian Szegedy wrote:
> William Djaja Tjokroaminata wrote:
> >Hi,
> >
> >Yes, I probably feel the same way as you do.  The more I know about the
> >extent of the Ruby garbage collector, the more concerned I am with its
> >impact on execution performance.
> >
> >I think I am using Ruby in some sense not in its original intended
> >purpose.  For my current application, I am using Ruby more like "a user
> >interface" then a full-blown programming tool.  The core computation is
> >done in C and therefore for efficiency purpose I have moved a lot of data
> >to C struct members instead of Ruby's "@" internal data.
> >
> >As I am trying to separate Ruby object model from its memory management,
> >issues like this really come out.  Has anybody really done a C programming
> >in the presence of a (mark & sweep) garbage collector (besides doing C
> >programming within the scripting languages)?
> >
> >Regards,
> >
> >Bill
> >============================================================================
> >Mauricio Fern?ndez <batsman.geo@yahoo.com> wrote:
> >
> >>On Wed, Aug 28, 2002 at 06:03:41PM +0900, Christian Szegedy wrote:
> >>
> >>>The Ruby garbage collector scans the used part of the stack,
> >>>and registers all addresses found there. This may be too much,
> >>>but it does not matter. (That was matzs commment about the
> >>>"conservativness of the gc")
> >>
> >
> >>What is the performance impact of Ruby's GC being conservative?
> >><=> How large is the C-stack usually?
> >
> >
> >>Couldn't we use some preprocessor-magic to mark the pointers as they're
> >>created?
> >
> 
> I don't have not made any tests but my intuition says that under normal 
> circumstances, the size of the (used part of) stack must be fairly 
> negligible compared to the heap, therefore, it should not make
> significant overhead.

That's what I thought, we just have to avoid alloca when the GC is about
to do its job.

If Ruby were interfaced with C++ we could have a special ValueReference
type which would (un)register the pointer as needed, so that a full
stack marking wouldn't be needed.

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