Re: Memory fragmentation?

On Thursday 2007-11-15 09:39 -0800, Dan Mosedale wrote:
> Boris Zbarsky wrote:
> > No, we don't. DOM nodes and other refcounted things can outlive the tab 
> > closure and teardown of the window arbitrarily. Just have some script in 
> > another window referencing them.
> 
> What percentage of the time do you think we would be able to destroy 
> them together?  Most of time, or am I misunderstanding how often these 
> sorts of references happen?

Well, there's a set of objects that we can destroy when we tear down
the document and then another set that we can destroy after the next
garbage collection / cycle collection.  Some things may occasionally
take multiple iterations of cycle collection to be collected (though
this generally means there's something deficient about the cycle
collection traversal implementations on some objects).  I'm not sure
whether you count all of that as "together", but that probably gets
most objects most of the time.

In some cases, script has pointers across windows.  This is probably
pretty common when Web apps open popups for things like picking a
date, choosing seats on a flight, etc.  In these cases, the page may
end up keeping pointers across windows, and we might not collect
some things until both/all windows are closed.

There are things like window.opener that require that we (the
browser) keep extra windows alive in case the page asks for them.
(I'm not sure if there's anything *else* like window.opener,
actually, but it does cause us to keep chrome windows alive longer
than we might want to.)

-David

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/